Forecast Discussions mentioning any of "HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/24/12

AREA FORECAST DISCUSSION

NWS NORTHERN INDIANA

 633 PM EST SUN DEC 23 2012



.AVIATION...
00Z TAFS.. BKN-SCT 20-30 WILL CONTINUE TO LINGER OVER SOUTHERN
MICHIGAN AND NORTHERN INDIANA BUT THIN OUT AFTER 06Z. OVC020 WILL
RETURN TO THE AREA DURING MORNING HOURS MONDAY WITH SLIGHT CHANCE
OF -SHSN LATER IN THE DAY

&&

.PREV DISCUSSION... /ISSUED 338 PM EST SUN DEC 23 2012/

SHORT TERM.../TONIGHT THROUGH MONDAY NIGHT/

LATEST SFC ANALYSIS HAS WEAK FRONTAL BOUNDARY JUST TO THE SOUTH
OF THE CWA EXTENDING BACK TO DEVELOPING FRONTAL WAVE IN EASTERN
OKLAHOMA. WATER VAPOR IMAGERY ALONG WITH LATEST RAP ANALYSIS
DEPICTING SPLIT FLOW PATTERN ACROSS THE EASTERN TWO THIRDS OF THE
CONUS...EACH WITH THEIR OWN WEAK DISTURBANCE THAT WILL MOVE ACROSS
THE REGION ON MONDAY. NORTHERN STREAM SHORT WAVE CURRENTLY MOVING
THROUGH THE DAKOTAS IS EXPECTED TO CONTINUE EASTWARD INTO THE
GREAT LAKES REGION WHILE SOUTHERN STREAM SHORT WAVE WILL MOVE INTO
THE TN VALLEY. MODEL TRENDS HAVE CONTINUED TOWARD A LACK OF
PHASING WITH THESE DISTURBANCES...RESULTING IN CONCERN OVER
FORCING AND AVAILABLE MOISTURE WITH PRECIP CHANCES MONDAY.
CONSENSUS FAVORS A SPLIT OVER OUR CWA IN BOTH MOISTURE AND
DYNAMICS AS WEAKER SOUTHERN STREAM MOVES QUICKLY INTO EAST TN BY
MONDAY AFTERNOON WHILE NORTHERN STREAM WAVE DIGS INTO THE CENTRAL
GREAT LAKES REGION AND WILL PROVIDE SOME DECENT FORCING IN OUR NE
CWA WITH 500MB HT FALLS OF 60-80M POSSIBLE. PROBLEM IS THAT BEST
MOISTURE WILL BE CONFINED TO THE NORTH. HAVE THEREFORE OPTED TO
KEEP POPS IN HIGH CHANCE RANGE IN EASTERN THIRD OF CWA WHERE BEST
CHANCE FOR PRECIP WILL MATERIALIZE. PRECIP TYPE WILL ALSO COME
INTO PLAY FOR THE E/SE CWA AS TEMPS EXPECTED TO REACH THE MID 30S
AND TIMING OF SYSTEM HAS BEST CHANCE FOR PRECIP AT MAX HEATING.
THIS WILL ALL ACT TO HOLD ANY ACCUMULATING SNOW IN CHECK WITH LESS
THAN AN INCH OVER THE NORTHERN CWA. SYSTEM QUICKLY EXITS THE
REGION MONDAY NIGHT...MAY GET CLIPPED WITH BRIEF LAKE EFFECT IN
ITS WAKE IN FAR NW CORNER BEFORE FLOW BECOMES MORE NE AND SHIFTS
ANY BANDS WEST OF THE AREA.&&

LONG TERM.../TUESDAY THROUGH SATURDAY/

FOCUS OF THE EXTENDED FORECAST WILL BE ON THE POTENTIAL OF SNOWFALL
ACROSS THE AREA WEDNESDAY.

FORECAST PERIOD BEGINS TUESDAY WILL QUASI ZONAL FLOW ACROSS GREAT
LAKES REGION IN ADVANCE OF SHARPENING H5 TROF AND DEEPENING SFC LOW
ACROSS WRN TX. RAISED HI TEMPS ACROSS THE SOUTHERN 3/4THS OF THE
AREA TUESDAY SLIGHTLY...AND RAISED LOWS SLIGHTLY ON TUESDAY
NIGHT...OTHERWISE NO MAJOR CHANGES TO FORECAST. H5 CUT OFF LOW WILL
DEVELOP OVER ARKLATEX REGION LATE TUESDAY AS UPPER TROF BECOMES
NEGATIVELY TILTED AND EJECTS NORTHEASTWARD THROUGH THE MID
MISSISSIPPI VALLEY INTO THE OHIO VALLEY BY WEDNESDAY. THE EXACT
TRACK OF THE SYSTEM WILL HAVE HUGE IMPLICATIONS FOR SNOWFALL AMOUNTS
ACROSS OUR AREA.

DECENT SPREAD BETWEEN DIFFERENT MODEL SYSTEM TRACKS...NOT TO BE
UNEXPECTED 72+ HOURS OUT. 12Z NAM AND 09Z/15Z SREF ARE FURTHEST NW W/
SFC LOW TRACK INVOF CINCINNATI...WHILE THE 00Z/12Z ECMWF IS FURTHER
SE WITH A JACKSON KY TO CHARLESTON WV SFC LOW TRACK. THE 12Z
GFS/GEFS IS A NICE COMPROMISE AMONG THE SOLUTIONS...WITH A FRANKFORT
KY TO CHILLICOTHE OH TRACK. OVERALL...RECENT MODEL TRENDS HAVE
SUBTLY SHIFTED THE SYSTEM TRACK NW WITH A SLIGHTLY SLOWER
SOLUTION...WHICH IS NOT UNCOMMON WITH NEGATIVELY TILTED PANHANDLE
HOOK TYPE SYSTEMS.

A LEAN TOWARD A 12Z GFS/GEFS LOW TRACK WOULD BRING THE POTENTIAL FOR
SIGNIFICANT SNOWFALL ACROSS A PORTION OF THE AREA...WITH BROAD
SATURATED ASCENT IN THE NW QUADRANT OF THE SYSTEM. THERMAL PROFILES
WOULD BE CONDUCIVE FOR ALL SNOW WITH THE ONSET OF THE SYSTEM FOR THE
DURATION OF THE EVENT. HOWEVER...A FURTHER NW SOLUTION OR STRONGER
SYSTEM COULD WRAP WARMER AIR INTO SE PORTIONS OF THE AREA AND IN
TURN MIXED PRECIPITATION POTENTIAL. THERE IS ALSO SOME EVIDENCE FOR
HEAVIER BANDED PRECIPITATION ACROSS A PORTION OF THE AREA. STRONG
H75-H6 FRONTOGENESIS...WITH NEAR ZERO OR NEGATIVE EPV ALOFT...AND
STRONG OMEGA IMPINGING ON THE DGZ WOULD SUGGEST INGREDIENTS FOR A
POSSIBLE BAND OF HEAVY SNOWFALL...HOWEVER GIVEN UNCERTAINTIES THIS
FAR OUT...CAN NOT RESOLVE THIS IN THE FORECAST AT THIS TIME. INITIAL
THINKING IS THAT A WIDESPREAD 2-4" EVENT...WITH LOWEST AMOUNTS
WEST/NW...WITH THE POTENTIAL FOR A NARROW BAND OF 4-6" WITH LOCALLY
HIGHER AMOUNTS SOMEWHERE ACROSS THE CENTRAL TO EASTERN/SOUTHEASTERN
PORTION OF THE AREA. CONTEMPLATED A WINTER STORM WATCH WITH THIS
FCST ISSUANCE...BUT DECIDED TO DEFER TO THE NEXT SHIFT TO CAPTURE
LATEST MODEL TRENDS AND POTENTIAL INCREASED CONFIDENCE.

FORECAST WISE...INCREASED POPS WEST/NWWARD WITH GIVEN MODEL
SOLUTIONS LATE TUESDAY NIGHT THROUGH WEDNESDAY...WITH A PERIOD OF
CAT POPS FAR SE WEDNESDAY. LEFT EXPECTED PTYPE ALL SNOW AT THIS
JUNCTURE GIVEN PREFERRED MODEL SOLUTION/TRACK/INTENSITY.

SYSTEM WILL EXIT THE REGION WEDNESDAY NIGHT INTO THURSDAY. SOME
POTENTIAL FOR LIGHT LAKE EFFECT SNOW THURSDAY INTO THURSDAY NIGHT
ACROSS FAR NW PORTIONS OF THE AREA WITH NORTHERLY FLOW IN THE WAKE
OF THIS SYSTEM. OTHERWISE CONDITIONS WILL BE DRY WITH COOLER
TEMPS...ESPECIALLY EAST WITH EXPECTED FRESH SNOWPACK. LOWS THURSDAY
NIGHT COULD DROP INTO THE LOWER TEENS EAST.

NEXT SYSTEM OF INTEREST WILL ARRIVE FRIDAY NIGHT INTO SATURDAY.
ECMWF AND GFS DISAGREE WITH THE OVERALL EVOLUTION OF THE
SYSTEM...BUT BOTH HAVE THE GENERAL IDEA AND IMPACT ON OUR AREA.
ECMWF SEPARATES THE NORTHERN AND SOUTHERN STREAM ENERGY...ALLOWING
FOR SHARPENING TROUGH AND LEE CYCLOGENESIS...SIMILAR TO MIDWEEK
PANHANDLE HOOK SYSTEM. GFS HOWEVER COMBINES BOTH NORTHERN AND
SOUTHERN STREAM ENERGY WITH BROAD UPPER TROF OVER ERN CONUS AND MORE
SUBTLE SHORTWAVE. NEVERTHELESS...TEMPERATURE PROFILES SUPPORT AN ALL
SNOW TYPE EVENT.



&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SHORT TERM...JAL
LONG TERM...NG
AVIATION...SABONES






AREA FORECAST DISCUSSION

NWS INDIANAPOLIS IN

 336 AM EST SAT DEC 22 2012

.UPDATE...
AVIATION AND LONG TERM SECTIONS HAVE BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 302 AM EST SAT DEC 22 2012

HIGH PRESSURE IS EXPECTED ACROSS THE AREA OVER THE WEEKEND. A LOW
PRESSURE SYSTEM IS EXPECTED TO MOVE THROUGH THE OHIO VALLEY AROUND
MONDAY. A STRONGER SYSTEM MAY AFFECT THE AREA TOWARDS THE MIDDLE OF
NEXT WEEK. IN THE WAKE OF THIS SYSTEM...HIGH PRESSURE WILL MOVE INTO
THE AREA FOR LATE NEXT WEEK.

&&

.NEAR TERM /TODAY/...
ISSUED AT 302 AM EST SAT DEC 22 2012

SATELLITE LOOP INDICATES BACK EDGE OF LOW CLOUD DECK IS BEGINNING TO
PUSH EAST. EXTRAPOLATION AND SHORT TERM MODEL DATA SUGGEST THE
CLEARING LINE SHOULD REACH THE FAR EASTERN ZONES AROUND SUNRISE.
OTHERWISE...EXPECTING A SUNNY DAY TODAY UNDER HIGH PRESSURE...WITH
ONLY SOME THIN HIGH CLOUD COVER AT TIMES. PROGGED LOW LEVEL
THICKNESSES SUGGEST THE GFS MOS HIGHS FOR TODAY MAY BE A FEW DEGREES
TOO COOL...MAINLY OVER THE NORTH. WILL BUMP UP THE NUMBERS ABOUT 3-4
DEGREES IN THOSE AREAS.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
ISSUED AT 302 AM EST SAT DEC 22 2012

MODELS INDICATE UPPER FLOW WILL FLATTEN OUT DURING THIS PERIOD AS
DEEP UPPER TROUGH CURRENTLY OVER THE NORTHEAST LIFTS INTO CANADA.
LOOKS RATHER QUIET THROUGH SUNDAY AS SURFACE AND UPPER RIDGING MOVES
THROUGH. MAIN ITEM OF INTEREST WILL BE A UPPER DISTURBANCE THAT IS
EXPECTED TO MOVE ACROSS THE FORECAST AREA MONDAY INTO MONDAY NIGHT.
SOME OF THE ENSEMBLE MEMBERS BRING A THREAT FOR SOME LIGHT RAIN OR
MIXED PRECIPITATION LATE SUNDAY NIGHT OVER THE FAR SOUTH...WHILE THE
MAJORITY OF THE OPERATIONAL AND ENSEMBLE DATA HOLD OFF THIS THREAT
UNTIL MONDAY. WILL CONTINUE TO KEEP THE FORECAST DRY THROUGH SUNDAY
NIGHT.

LIFT WITH THE SYSTEM COMING IN ON MONDAY LOOKS PRETTY DECENT AT THIS
POINT...ALTHOUGH DEEP MOISTURE IN THE PRECIPITATION BEARING LAYERS
IS QUESTIONABLE. THEREFORE...DOESN/T APPEAR THIS SYSTEM WILL BE A
BIG QPF PRODUCER. WILL GO WITH CHANCE POPS FOR LIGHT RAIN OR SNOW
OVER THE NORTHERN TWO THIRDS OF THE FORECAST AREA ON MONDAY...AND
CHANCE POPS FOR LIGHT RAIN FARTHER SOUTH. APPEARS THIS SYSTEM WILL
MOVE EAST OF THE AREA DURING MONDAY NIGHT...SO WILL KEEP SOME
SMALL CHANCE POPS FOR LIGHT SNOW OR RAIN INTO MONDAY NIGHT.

PROGGED LOW LEVEL THICKNESSES SUGGEST THE GFS MOS TEMPERATURE
GUIDANCE FOR SUNDAY AND MONDAY LOOK TOO COOL...ESPECIALLY THE HIGHS
ON SUNDAY. WILL BUMP UP THE GUIDANCE HIGHS SUNDAY ABOUT 5
DEGREES...AND NUDGE THE SUNDAY NIGHT LOWS AND MONDAY NIGHTS UP
SLIGHTLY.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...

ISSUED AT 336 AM EST SAT DEC 22 2012

THE FORECAST FOCUS STILL APPEARS TO BE ON A POSSIBLE  WINTER STORM
AROUND MIDWEEK AS ADVERTISED BY THE GFS AND EUROPEAN MODELS.

LIGHT PRECIP FROM MONDAY SYSTEM WILL HAVE ENDED BY TUESDAY AS HIGH
PRESSURE BUILDS ACROSS OUR AREA.  BOTH THE GFS AND EURO INDICATE
SIGNIFICANT SNOW ACCUMULATIONS BY WEDNESDAY AS STRONG LOW PRESSURE
TRACKS FROM NORTHERN MISSISSIPPI VALLEY TO THE MID APPALACHIANS. LOW
LEVEL THICKNESS INDICATE PRECIP TO BE ALL SNOW. BUT IT COULD FIRST
START OUT BRIEFLY AS MIXED OVER SOUTHERN SECTIONS TUESDAY NIGHT.
ON THE OTHER HAND...THE DGEX AND CANADIAN TAKE THE SURFACE LOW A
LITTLE FARTHER SOUTH AND EAST AND TRACK THE SIGNIFICANT PRECIP
BARELY SOUTH AND EAST OF OUR REGION. THE GFS ENSEMBLE MEAN SUPPORTS
THE OPERATIONAL GFS SCENARIO WITH POSSIBLE HEAVY SNOW AS FAR
NORTHWEST AS INDY. BUT THERE IS A LARGE SPREAD WITH SURFACE LOW
TRACKS RANGING FROM THE CAROLINA COAST TO THE OHIO VALLEY.  FOR NOW
WILL CONTINUE LIKELY POPS OVER THE SOUTHEAST HALF OF OUR REGION
WEDNESDAY. IF THE GFS AND EURO ARE CORRECT THIS MAY WELL END UP AS
OUR NEXT WINTER STORM.

LIGHT SNOW MAY LINGER ACROSS OUR REGION WEDNESDAY NIGHT AND WILL
CONTINUE ISOLATED SNOW SHOWERS NORTHEAST THURSDAY...MAINLY FROM LAKE
EFFECT.  THEN DRY WEATHER WILL BE THE RULE THURSDAY AND FRIDAY.
MODELS INDICATE PRECIP MAY OCCUR FRIDAY NIGHT AND SATURDAY AS
ANOTHER SYSTEM MOVES OUR WAY.

ALL BLEND TEMPERATURES SEEM REASONABLE TUESDAY AND WEDNESDAY.  WENT
A FEW DEGREES COLDER THAN MOS TEMPERATURES AFTER WEDNESDAY AS THERE
WILL PROBABLY BE SOME SNOW COVER.

&&

.AVIATION /DISCUSSION FOR THE 220900Z KIND TAF UPDATE/...

ISSUED AT 336 AM EST SAT DEC 22 2012

MINOR TWEAKS MADE TO KIND TAF PER OBSERVATIONS. NO OTHER CHANGES
NEEDED AT THIS TIME. PREVIOUS AVIATION DISCUSSION FOLLOWS...

MVFR EXPECTED TO  IMPROVE TO VFR DURING THIS TAF PERIOD.

IR IMAGES SHOW BACK EDGE OF THE LARGE CLOUD SHIELD ASSOCIATED WITH
THE STRONG AREA OF LOW PRESSURE TO THE NORTHEAST STILL LINGERING
ACROSS THE TAF SITES AT IND...LAF AND BMG. LATEST RAP INDICATES
THAT THIS FEATURE SHOULD FINALLY DRIFT EAST AFTER 09Z...AND WILL
TREND TAFS THIS WAY.

MODELS SUGGEST MID LEVEL RIDGE BUILDING ACROSS THE AREA ON
SATURDAY...AS THIS SHOULD CERTAINLY PUSH THE CYCLONIC CLOUD SHIELD
EAST. TAF SITES SHOULD GO VFR ON SATURDAY AS FORECAST SOUNDINGS
AND TIME HEIGHT SECTIONS DRY OUT AND CONVECTIVE TEMPERATURES
REMAIN UNATTAINABLE.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....JH
AVIATION...JH











AREA FORECAST DISCUSSION

NWS INDIANAPOLIS IN

 305 AM EST SAT DEC 22 2012

.UPDATE...
THE SYNOPSIS...NEAR TERM AND SHORT TERM SECTIONS HAVE BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 302 AM EST SAT DEC 22 2012

HIGH PRESSURE IS EXPECTED ACROSS THE AREA OVER THE WEEKEND. A LOW
PRESSURE SYSTEM IS EXPECTED TO MOVE THROUGH THE OHIO VALLEY AROUND
MONDAY. A STRONGER SYSTEM MAY AFFECT THE AREA TOWARDS THE MIDDLE OF
NEXT WEEK. IN THE WAKE OF THIS SYSTEM...HIGH PRESSURE WILL MOVE INTO
THE AREA FOR LATE NEXT WEEK.

&&

.NEAR TERM /TODAY/...
ISSUED AT 302 AM EST SAT DEC 22 2012

SATELLITE LOOP INDICATES BACK EDGE OF LOW CLOUD DECK IS BEGINNING TO
PUSH EAST. EXTRAPOLATION AND SHORT TERM MODEL DATA SUGGEST THE
CLEARING LINE SHOULD REACH THE FAR EASTERN ZONES AROUND SUNRISE.
OTHERWISE...EXPECTING A SUNNY DAY TODAY UNDER HIGH PRESSURE...WITH
ONLY SOME THIN HIGH CLOUD COVER AT TIMES. PROGGED LOW LEVEL
THICKNESSES SUGGEST THE GFS MOS HIGHS FOR TODAY MAY BE A FEW DEGREES
TOO COOL...MAINLY OVER THE NORTH. WILL BUMP UP THE NUMBERS ABOUT 3-4
DEGREES IN THOSE AREAS.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
ISSUED AT 302 AM EST SAT DEC 22 2012

MODELS INDICATE UPPER FLOW WILL FLATTEN OUT DURING THIS PERIOD AS
DEEP UPPER TROUGH CURRENTLY OVER THE NORTHEAST LIFTS INTO CANADA.
LOOKS RATHER QUIET THROUGH SUNDAY AS SURFACE AND UPPER RIDGING MOVES
THROUGH. MAIN ITEM OF INTEREST WILL BE A UPPER DISTURBANCE THAT IS
EXPECTED TO MOVE ACROSS THE FORECAST AREA MONDAY INTO MONDAY NIGHT.
SOME OF THE ENSEMBLE MEMBERS BRING A THREAT FOR SOME LIGHT RAIN OR
MIXED PRECIPITATION LATE SUNDAY NIGHT OVER THE FAR SOUTH...WHILE THE
MAJORITY OF THE OPERATIONAL AND ENSEMBLE DATA HOLD OFF THIS THREAT
UNTIL MONDAY. WILL CONTINUE TO KEEP THE FORECAST DRY THROUGH SUNDAY
NIGHT.

LIFT WITH THE SYSTEM COMING IN ON MONDAY LOOKS PRETTY DECENT AT THIS
POINT...ALTHOUGH DEEP MOISTURE IN THE PRECIPITATION BEARING LAYERS
IS QUESTIONABLE. THEREFORE...DOESN/T APPEAR THIS SYSTEM WILL BE A
BIG QPF PRODUCER. WILL GO WITH CHANCE POPS FOR LIGHT RAIN OR SNOW
OVER THE NORTHERN TWO THIRDS OF THE FORECAST AREA ON MONDAY...AND
CHANCE POPS FOR LIGHT RAIN FARTHER SOUTH. APPEARS THIS SYSTEM WILL
MOVE EAST OF THE AREA DURING MONDAY NIGHT...SO WILL KEEP SOME
SMALL CHANCE POPS FOR LIGHT SNOW OR RAIN INTO MONDAY NIGHT.

PROGGED LOW LEVEL THICKNESSES SUGGEST THE GFS MOS TEMPERATURE
GUIDANCE FOR SUNDAY AND MONDAY LOOK TOO COOL...ESPECIALLY THE HIGHS
ON SUNDAY. WILL BUMP UP THE GUIDANCE HIGHS SUNDAY ABOUT 5
DEGREES...AND NUDGE THE SUNDAY NIGHT LOWS AND MONDAY NIGHTS UP
SLIGHTLY.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...

ISSUED AT 239 PM EST FRI DEC 21 2012

FORECAST FOCUS IS ON SIGNIFICANT STORM SYSTEM MID WEEK...WHICH MAY
OR MAY NOT HIT CENTRAL INDIANA DEPENDING ON THE EXACT TRACK. QUITE A
BIT OF VARIABILITY IN MODEL SOLUTIONS WITH THIS SYSTEM. WITH HIGH
ENSEMBLE SPREAD AND THE GFS ENSEMBLE AVERAGE SOLUTION AND GEM
SOLUTION VARYING SIGNIFICANTLY FROM THE OPERATIONAL GFS AND 12Z
ECMWF THINK BEST COURSE OF ACTION IS TO GO WITH A CONSENSUS AND HOPE
VARIABILITY LESSENS AS SYSTEM APPROACHES.

MONDAY NIGHT A SYSTEM ALONG THE OHIO RIVER SHOULD BE PULLING AWAY
FROM THE AREA. COULD SEE A MIX OF RAIN AND SNOW IN THE SOUTH WITH
SNOW IN THE NORTH BRIEFLY BEFORE THE LOW PULLS FAR ENOUGH AWAY FROM
THE AREA TO BRING PRECIP TO AN END. CHRISTMAS DAY LOOKS LIKE HIGH
PRESSURE WILL BRIEFLY BE OVER THE AREA KEEPING CONDITIONS DRY.
CHRISTMAS NIGHT IS WHEN POPS START TO BE INTRODUCED WITH THE
AFOREMENTIONED SIGNIFICANT SYSTEM. LOW TRACKS VARY FROM UP THE
MISSISSIPPI RIVER THROUGH THE TENNESSEE VALLEY TO ACROSS THE FLORIDA
PANHANDLE AND UP THE EAST COAST. THIS LESSENS CONFIDENCE IN ANY
PARTICULAR SOLUTION. CONSENSUS POPS YIELD CHANCE FOR CHRISTMAS NIGHT
WITH LIKELY IN THE SOUTHEAST ON WEDNESDAY AND CHANCE WEDNESDAY
NIGHT. FOR PRECIP TYPE WILL GO WITH SNOW IN THE NORTH AND A MIX OF
RAIN AND SNOW IN THE SOUTH AS TRACK VARIABILITY IMPACTS THE ARRIVAL
OF THE COLD AIR AS WELL. TEMPERATURES SHOULD BE BELOW NORMAL AFTER
TUESDAY.

&&

.AVIATION /DISCUSSION FOR THE 220600Z IND TAFS/...

ISSUED AT 1118 PM EST FRI DEC 21 2012

MVFR EXPECTED TO  IMPROVE TO VFR DURING THIS TAF PERIOD.

IR IMAGES SHOW BACK EDGE OF THE LARGE CLOUD SHIELD ASSOCIATED WITH
THE STRONG AREA OF LOW PRESSURE TO THE NORTHEAST STILL LINGERING
ACROSS THE TAF SITES AT IND...LAF AND BMG. LATEST RAP INDICTATES
THAT THIS FEATURE SHOULD FINALLY DRIFT EAST AFTER 09Z...AND WILL
TREND TAFS THIS WAY.

MODELS SUGGEST MID LEVEL RIDGE BUILDING ACROSS THE AREA ON
SATURDAY...AS THIS SHOULD CERTAINLY PUSH THE CYCLONIC CLOUD SHIELD
EAST. TAF SITES SHOULD GO VFR ON SATURDAY AS FORECAST SOUNDINGS
AND TIME HEIGHT SECTIONS DRY OUT AND CONVECTIVE TEMPERATURES
REMAIN UNATTAINABLE.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....CP
AVIATION...JP







AREA FORECAST DISCUSSION

NWS INDIANAPOLIS IN

 1126 PM EST FRI DEC 21 2012

.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW

&&

.SYNOPSIS...

ISSUED AT 152 PM EST FRI DEC 21 2012

A STRONG STORM SYSTEM WILL CONTINUE TO PULL AWAY FROM THE AREA
TONIGHT. HIGH PRESSURE IS EXPECTED TO BUILD IN FOR THE WEEKEND. A
LOW PRESSURE SYSTEM MAY MOVE THROUGH THE OHIO VALLEY EARLY NEXT
WEEK...AROUND MONDAY. A POTENTIALLY STRONGER SYSTEM MAY AFFECT THE
AREA TOWARDS THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /REST OF TONIGHT/...

ISSUED AT 1004 PM EST FRI DEC 21 2012

CLOUDS CONTINUE TO PERSIST ACROSS MUCH OF THE FORECAST AREA.
SATELLITE LOOPS SHOW LITTLE IN THE WAY OF CLEARING WORKING TOWARD
THE AREA AS CYCLONIC FLOW REMAINS DOMINANT.

LATEST HI RES MODEL DATA SHOW THAT CLOUDS LINGERING THROUGH MUCH
OF THE NIGHT ACROSS MUCH OF THE EASTERN HALF OF THE FORECAST AREA.
GIVEN ALL OF THE ABOVE HAVE INCREASED CLOUD COVER OVER MUCH OF THE
AREA THROUGH THE NIGHT.

WITH THE INCREASED CLOUD COVER HAVE BUMPED UP TEMPERATURES A
LITTLE WHERE CLOUDS WILL PERSIST. AM HESITANT TO RAISE TOO MUCH
THOUGH...AS TEMPERATURES WILL DROP QUICKLY WITH ANY BREAKS THAT DO
HAPPEN TO FORM.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...

ISSUED AT 152 PM EST FRI DEC 21 2012

MODELS INDICATE UPPER FLOW FLATTENING OUT AS THE DEEP UPPER TROUGH
LIFTS OFF INTO THE CANADIAN MARITIMES BY SUNDAY. CENTRAL INDIANA
WILL ENTER A QUIET FORECAST PERIOD THROUGH THE WEEKEND. TEMPERATURES
WILL MODERATE OVER THIS TIME BACK TO CLIMO...AND EVEN SLIGHT ABOVE
CLIMO BY SUNDAY AFTERNOON.

ONLY ITEM OF INTEREST WILL BE A POTENTIAL SHORT WAVE TROUGH THAT THE
MODELS BRING INTO THE MIDWEST BY LATE SUNDAY NIGHT. SOME OF THE
ENSEMBLE MEMBERS BRING A THREAT FOR SOME LIGHT RAIN OR MIXED
PRECIPITATION ACROSS THE NORTHERN COUNTIES DURING THE DAY MONDAY.
THIS FEATURE LOOKS WEAKER WITH LATEST MODELS RUNS...AND SOME MODELS
(THE GFS) BARELY EVEN DEPICT IT PRODUCING ANY PRECIPITATION FOR
CENTRAL INDIANA. HAVE THEREFORE BACKED OFF ON POP DURING THIS TIME.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...

ISSUED AT 239 PM EST FRI DEC 21 2012

FORECAST FOCUS IS ON SIGNIFICANT STORM SYSTEM MID WEEK...WHICH MAY
OR MAY NOT HIT CENTRAL INDIANA DEPENDING ON THE EXACT TRACK. QUITE A
BIT OF VARIABILITY IN MODEL SOLUTIONS WITH THIS SYSTEM. WITH HIGH
ENSEMBLE SPREAD AND THE GFS ENSEMBLE AVERAGE SOLUTION AND GEM
SOLUTION VARYING SIGNIFICANTLY FROM THE OPERATIONAL GFS AND 12Z
ECMWF THINK BEST COURSE OF ACTION IS TO GO WITH A CONSENSUS AND HOPE
VARIABILITY LESSENS AS SYSTEM APPROACHES.

MONDAY NIGHT A SYSTEM ALONG THE OHIO RIVER SHOULD BE PULLING AWAY
FROM THE AREA. COULD SEE A MIX OF RAIN AND SNOW IN THE SOUTH WITH
SNOW IN THE NORTH BRIEFLY BEFORE THE LOW PULLS FAR ENOUGH AWAY FROM
THE AREA TO BRING PRECIP TO AN END. CHRISTMAS DAY LOOKS LIKE HIGH
PRESSURE WILL BRIEFLY BE OVER THE AREA KEEPING CONDITIONS DRY.
CHRISTMAS NIGHT IS WHEN POPS START TO BE INTRODUCED WITH THE
AFOREMENTIONED SIGNIFICANT SYSTEM. LOW TRACKS VARY FROM UP THE
MISSISSIPPI RIVER THROUGH THE TENNESSEE VALLEY TO ACROSS THE FLORIDA
PANHANDLE AND UP THE EAST COAST. THIS LESSENS CONFIDENCE IN ANY
PARTICULAR SOLUTION. CONSENSUS POPS YIELD CHANCE FOR CHRISTMAS NIGHT
WITH LIKELY IN THE SOUTHEAST ON WEDNESDAY AND CHANCE WEDNESDAY
NIGHT. FOR PRECIP TYPE WILL GO WITH SNOW IN THE NORTH AND A MIX OF
RAIN AND SNOW IN THE SOUTH AS TRACK VARIABILITY IMPACTS THE ARRIVAL
OF THE COLD AIR AS WELL. TEMPERATURES SHOULD BE BELOW NORMAL AFTER
TUESDAY.

&&

.AVIATION /DISCUSSION FOR THE 220600Z IND TAFS/...

ISSUED AT 1118 PM EST FRI DEC 21 2012

MVFR EXPECTED TO  IMPROVE TO VFR DURING THIS TAF PERIOD.

IR IMAGES SHOW BACK EDGE OF THE LARGE CLOUD SHIELD ASSOCIATED WITH
THE STRONG AREA OF LOW PRESSURE TO THE NORTHEAST STILL LINGERING
ACROSS THE TAF SITES AT IND...LAF AND BMG. LATEST RAP INDICTATES
THAT THIS FEATURE SHOULD FINALLY DRIFT EAST AFTER 09Z...AND WILL
TREND TAFS THIS WAY.

MODELS SUGGEST MID LEVEL RIDGE BUILDING ACROSS THE AREA ON
SATURDAY...AS THIS SHOULD CERTAINLY PUSH THE CYCLONIC CLOUD SHIELD
EAST. TAF SITES SHOULD GO VFR ON SATURDAY AS FORECAST SOUNDINGS
AND TIME HEIGHT SECTIONS DRY OUT AND CONVECTIVE TEMPERATURES
REMAIN UNATTAINABLE.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...SMF
NEAR TERM...50
SHORT TERM...SMF
LONG TERM....CP
AVIATION...JP





AREA FORECAST DISCUSSION

NWS GOODLAND KS

 150 PM MST SAT DEC 22 2012

.SHORT TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 150 PM MST SAT DEC 22 2012

EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOWS BROAD RIDGE
ACROSS THE CENTRAL US EXTENDING NORTH INTO SOUTHERN CANADA...WITH
TROUGHS UP STREAM AND DOWN STREAM ALONG THE COASTS. AT THE SURFACE A
COLD FRONT CURRENTLY EXTENDS ACROSS CENTRAL NEBRASKA...WITH A
PREFRONTAL SURFACE TROUGH ACROSS CENTRAL KANSAS.

TONIGHT THROUGH SUNDAY...PATTERN REMAINS QUIET WITH VERY DRY AIR
MASS IN PLACE...HIGHLIGHTED BY DEWPOINT DEPRESSIONS GREATER THAN 20C
THROUGH ABOUT 400MB THROUGH SUNDAY AFTERNOON. WHILE THERE WILL BE
LARGE SCALE ASCENT ASSOCIATED WITH SHORTWAVE PASSAGE ACROSS NORTHERN
PLAINS AND ASSOCIATED COLD FRONT PASSAGE SUNDAY...I DO NOT THINK WE
WILL SEE MUCH OTHER THAN PASSING HIGH CLOUDS CONSIDERING THE DEEP
DRY AIR MASS. H85 TEMPS COOLING BY ABOUT 4-5C BY SUN MORNING WITH
MOST LOCATIONS 7-10F COOLER AND NEGATIVE VALUES POSSIBLE ACROSS THE
NORTHEAST. I DROPPED HIGH TEMPS A LITTLE SUNDAY ACROSS THE CWA
COMPARED TO THIS AFTERNOON TO ACCOUNT FOR THICKER CLOUD COVER AND
COOLER AIRMASS BEHIND FRONT. SNOWPACK CONTINUES TO MELT ACROSS THE
SW CWA AND WITH WINDS SHIFTING BACK TO THE WEST/SOUTHWEST SNOW PACK
SHOULD START TO HAVE LESS OF AN IMPACT EXCEPT IN THE FAR EAST.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 150 PM MST SAT DEC 22 2012

FORECAST CONCERNS WILL BE STORM AT THE BEGINNING OF NEXT WEEK...
NEXT STORM TOWARD THE END OF NEXT WEEK...AND HOW COLD TO MAKE IT
NEXT WEEK. SATELLITE SHOWING AN AMPLIFIED/AMPLIFYING FLOW FROM THE
PACIFIC INTO THE ATLANTIC. IN THIS IS A COMPLEX/COLD UPPER TROUGH
ALONG THE WEST COAST OF NORTH AMERICA WHICH HAS CAUSED AN UPPER
RIDGE OVER THE CENTRAL PORTION OF COUNTRY. VERY COLD LOW LEVEL AIR
MASS/COLD FRONT NOT TOO FAR TO OUR NORTH.

MODELS AT MID AND UPPER LEVELS APPEAR TO HAVE INITIALIZED FINE.
HOWEVER BASED ON SATELLITE...WOULD FAVOR THE SLIGHTLY MORE WEST
INITIALIZATION OF THE UPPER TROUGH NEAR THE WEST COAST. THE NAM AND
ECMWF WERE DOING THE BEST ON THE LOW LEVEL SURFACE WIND/PRESSURE
FIELD. OVERALL THE CANADIAN WAS DOING A LITTLE BETTER ON THE LOW
LEVEL THERMAL FIELD.

SUNDAY NIGHT/MONDAY...MAJOR TRANSITION BEGINS ON MONDAY. MID AND
UPPER LEVEL CLOUD COVER WILL INCREASE AT THE SAME TIME A FRONT
BACKDOORS INTO THE AREA. EASTERLY UPSLOPE INCREASES DURING THE DAY.
AS A RESULT HIGH TEMPERATURES WILL END UP BEING WELL BELOW NORMAL
WITH COLDEST TEMPERATURES IN THE NORTHEAST AND THE WARMEST IN THE
SOUTHWEST. GUIDANCE WAS CLUSTERING AROUND COOLER MAXES THAN WHAT
WAS IN THERE FOR PREVIOUS FORECAST. SO REDUCED THE MAXES.

MAIN LIFT AND DEEPER MOISTURE WILL WAIT UNTIL THE NIGHT TO GET HERE.
MORE THAN ONE MODEL SHOWS THE BOUNDARY LAYER SATURATING UP WITH A
DRY MID LAYER. IT WILL BE UNUSUAL BUT IT LOOKS LIKE FOG WILL
DEVELOP IN THE AFTERNOON AND POSSIBLE SOME FREEZING DRIZZLE. SO
INSERTED THAT INTO THE GRIDS.

MONDAY NIGHT/TUESDAY...IN GENERAL MODELS AGREE ON THE EVOLUTION OF
INCOMING SYSTEM WHICH IS TO DEVELOP THE UPPER TROUGH INTO A CLOSED
OFF CIRCULATION...MAINLY AT 700 MB...AS IT DIGS/MOVES TOWARD THE
SOUTHEAST. PREVIOUS EXPERIENCE HAS SHOWN ME THAT THIS USUALLY IS NOT
THE BEST SCENARIO FOR GETTING A SIGNIFICANT AMOUNT OF SNOW. BASED ON
THE PATTERN/SATELLITE IS INDICATING/SHOWING...BELIEVE THIS SYSTEM
WILL BE COMING IN SLOWER AND FURTHER SOUTH AND WEST. THIS FITS THE
BEST WITH THE ECMWF SOLUTION AND TO A LESSER DEGREE THE CANADIAN...
UKMET...AND GFS SOLUTION. THEY DO THE SAME THING BUT FASTER.

AM CONCERNED THAT WITH THE WAY THE PATTERN IS...THAT FUTURE MODEL
RUNS WILL TAKE THE SYSTEM FURTHER SOUTHWEST AND FURTHER DIMINISH THE
AMOUNT OF SNOW. FOR THE NIGHTTIME PERIOD AS IT STANDS NOW...THE
SOUTHWEST HALF OF THE AREA LOOKS TO HAVE THE BEST CHANCE FOR SNOW.
UNTIL THE SNOW STARTS...WILL KEEP THE FOG AND DRIZZLE GOING IN THE
EVENING PER THE REASONING GIVEN ABOVE.

DURING THE DAY TUESDAY...THE BEST CHANCE FOR SNOW WILL TRANSITION
INTO THE SOUTHERN THIRD IN THE MORNING BEFORE DECREASING AND ENDING
IN THE AFTERNOON. AMOUNTS STILL LOOK IN THE 1 TO 3 INCH RANGE WITH
THE SOUTHWEST HALF HAVING THE HIGHEST AMOUNTS. COMBINATION OF
CLOUDS...PRECIPITATION...AND VERY GOOD COLD AIR ADVECTION WILL MAKE
FOR AN EXTREMELY COLD DAY WITH WELL BELOW NORMAL TEMPERATURES.
TENDED TO GO WITH THE CLUSTERING OF GUIDANCE WHICH SUPPORTED
COOLING MAXES FROM PREVIOUS FORECAST. HOWEVER...SOME GUIDANCE IS
SHOWING THAT MAXES COULD BE EVEN COLDER.

TUESDAY NIGHT THROUGH SATURDAY...QUIET WEATHER WILL OCCUR THROUGH
THURSDAY. THE NEXT SYSTEM WILL MOVE THROUGH THE REGION THURSDAY
NIGHT AND FRIDAY. MODELS ARE IN GOOD AGREEMENT WITH THE SPEED OF THE
SYSTEM MOVING THROUGH BUT DIFFER ON THE AMPLITUDE OF THE SYSTEM. THE
ECMWF IS THE OUTLIER WITH A CUTOFF SOLUTION WITH THE REMAINING
DETERMINISTIC SOLUTIONS/ENSEMBLES SUPPORTING THE OPEN WAVE
SOLUTION. LIKE WHAT THE CRH_INIT GAVE ME DUE TO THE MODEL
DIFFERENCES. RIGHT NOW IT IS SLIGHT CHANCE TO CHANCE WHICH IS
REASONABLE BUT THERE IS POTENTIAL TO GO A LITTLE HIGHER. ONE THING
FOR SURE IS THAT HIGH TEMPERATURES WILL BE COLD THROUGH THE ENTIRE
WEAK AND THE INIT TEMPERATURES LOOKED REASONABLE AND MADE LITTLE TO
NO CHANGES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1046 AM MST SAT DEC 22 2012

VFR CONDITIONS ARE EXPECTED AT BOTH KGLD AND KMCK. WEST WINDS WILL
SHIFT TO THE NORTH DURING THE AFTERNOON AS A WEAK PROGRESSIVE COLD
FRONT DROPS SOUTH ACROSS THE AREA BEFORE SHIFTING BACK TO THE WEST
THIS EVENING. WINDS SHOULD GENERALLY REMAIN LESS THAN
12KT...THOUGH SOME HIGHER WINDS COULD BE RULED OUT THIS AFTERNOON
DEPENDING ON AFTERNOON MIXING. CONFIDENCE WAS TOO LOW TO
INCREASE WINDS TOO MUCH...SO WILL MONITOR THIS.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

SHORT TERM...DR
LONG TERM...BULLER
AVIATION...DR





AREA FORECAST DISCUSSION

NWS LOUISVILLE KY

 326 AM EST SAT DEC 22 2012

.Short Term (Today - Sunday)...
Issued at 325 AM EST Sat Dec 22 2012

Weather in the short-term period is rather quiet as we wait for our
next set of weather systems to track across the Ohio Valley. A
stratus deck lingers across south-central Indiana and extends
southeastward through eastern Kentucky. The southward push of this
deck has stalled and the back edge is now dissipating with
increasing dry air advection from the west. While most of the
forecast area will start the day clear/sunny, portions of southeast
Indiana, the Bluegrass, and east-central Kentucky will see the
clouds scatter out and head east as the morning progresses.

Otherwise, cold surface high pressure will quickly shift east over
the forecast area today. Being on the northern edge of this high,
northwest surface winds will back and become southwesterly at 5 to
10 mph by later this afternoon. Southwest winds will then remain in
place through the short-term period, allowing temperatures to
moderate a bit.

Temperatures are starting out in the 20s this morning, with wind
chill values in the teens. Temperatures are expected to range from
the mid 30s across southeast Indiana and the Bluegrass region to
lower 40s in the south and southwest CWA by this afternoon, but the
wind chill will make it feel several degrees cooler. For tonight,
guidance continues to indicate south and southwest winds will remain
slightly elevated and clouds should be on the increase from the
southwest late tonight. Low temperatures ranging from the mid 20s to
right around 30 degrees will be common, with normally cooler
locations dropping into the lower 20s. These temps may occur early
in the night, before moderating a bit closer to sunrise.

Clouds will continue to increase from the southwest Sunday, as a
shortwave and low pressure system develop to our west. Southwest
winds will pick up and could become locally breezy, which will help
max temperatures range from the mid 40s to lower 50s. While moisture
return is limited, isentropic lift will be ongoing ahead of this
system, which could spread some light rain across south-central
Kentucky late in the afternoon. With this warm-air advection
pattern, all precip will be in liquid form. Now on to the
interesting portion of the forecast, the long term!

.Long Term (Sunday Night - Friday)...
Issued at 320 AM EST Sat Dec 22 2012

...First Significant Snow Possible the Day after Christmas...

At the start of the period, a warm front will extend northeast of a
low pressure center in the Arklatex, stretching across or just north
of the Ohio Valley. The best isentropic lift indicated in the models
will remain across the southern forecast area, so will keep the
better rain chances down there. By evening, the low is forecast to
be east of the region, taking any light rains along with it. QPF
will be light for this event, as moisture return is limited ahead of
this feature.

After a quiet Christmas Day, the next big system looks to come into
play. Models have been run-to-run consistent and both the GFS and
ECMWF have been in pretty good agreement on this system, both
deterministic and ensembles. The Canadian GEM is farther south with
the system, but its trajectory is more typical of systems this time
of year, so its solution cannot be ruled out. By 00Z Wednesday, the
EC and GFS have the surface low deepening over Mississippi. This low
travels toward eastern Tennessee by daybreak Wednesday, with its
parent upper low over central Tennessee. This track would place a
band of moderate to heavy snow somewhere across our forecast area
Wednesday morning. Trying to get specific for one area and how much
snow it will get is too difficult at this point, but it is appearing
more likely that someone will get heavy snow on the back side of
this low, with the cold air in place. The Canadian GEM solution
brings the heavier snow to our southern forecast, whereas the GFS
has the band over southern Indiana. The ECMWF is in between. As we
have to put some snow in somewhere, have gone with southern Indiana
for now as having the highest snow totals...and that being 5-7
inches of snow. This is well under the foot of snow the GFS has in a
deformation band across southern Indiana. Again look for the peak
values likely to change both in intensity and location!

By Wednesday evening, the surface low will shift quickly to the mid
Atlantic coast, bringing an end to the significant precipitation.
Canadian high pressure will build into the region for Thursday and
Friday. Depending on where the heaviest snow falls, very cold
temperatures are possible Thursday night, as it looks ideal for
radiational cooling combined with a snowpack. Guidance is no help
here either, as it calls for lows around 20.  Would not be surprised
to see some single digits in places with the best snow pack, but
these numbers can be refined as the forecast becomes more precise.
Another factor could be some mid/high cloudiness coming in as a
ridge axis aloft crosses our region.

&&

.Aviation (06Z TAF Issuance)...
Issued at 1240 AM EST Sat Dec 22 2012

Strong surface low continues to move into Quebec with high pressure
becoming established across the Mississippi River Valley. The
resultant pressure gradient is starting to gradual weakening this
morning as the low continues to push northeast. Northwest winds will
back to a more west-southwesterly direction between 5 and 10 mph by
about mid morning, as the center of the surface high passes by to
our south.

Lingering cyclonic stratus deck is trying to make southward
progress. Do not think it will push too much further south, with SDF
remaining on the southern edge and LEX overcast until the deck
scatters and shifts northeast later this morning. Models are not
handling this situation well, with the RAP having the best solution.
However, it seems to be currently overdoing the clouds at SDF. Will
continue to monitor. Otherwise, only expect a few upper-level clouds
streaming overhead today.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
KY...NONE.
$$


Short Term.......MJP
Long Term........RJS
Aviation.........MJP






AREA FORECAST DISCUSSION

NWS LOUISVILLE KY

 1242 AM EST SAT DEC 22 2012

...Updated Aviation Discussion...

.Forecast Update...
Issued at 949 PM EST Fri Dec 21 2012

Winds have slackened across the region with gustiness subsiding as
well. May still have a few gusts for the next couple of hours. Main
reason for an update this evening is to reintroduce sky cover as
stratus deck has built back into the region with 925mb moisture
advection from the north. This will likely occur as far southwest as
a Salem, IN, to Louisville, to Somerset, KY line. Further southwest,
expect clear skies to persist. Stratus should remainder much of the
night, although surface high over the Mississippi River Valley should
start to push in toward dawn, with drier air working away at the
cloud cover. Overall, stratus should not have a huge impact on
overnight lows as steady cold air advection will win out. That being
said, did raise lows a degree or two underneath the expected cloud
cover. Updated products already out.

&&

.Short Term (Tonight - Saturday Night)...
Issued at 315 PM EST Fri Dec 21 2012

In coordination with other offices and since mesonet sites are still
gusting between 30-40 mph, will continue the SPS until 6 pm EST.
Wind gusts are expected to subside shortly after sunset.

Snow has ended across the region with storm totals generally between
a trace and a half inch over southern Indiana and east central
Kentucky.  Elsewhere over central KY, trace amounts to a few tenths
of snow were observed.  The highest snow accumulation reported was
0.9 inches reported in Harrison County KY.  See our
website...www.weather.gov/lmk...for more details on snow totals and
max wind gusts over the last 36-48 hours.

Skies will continue to clear from SW to NE across the area this
evening with sfc high pressure building in for Saturday.  As a
result we`ll see mostly clear skies through Sat night.  Tonight low
temperatures will drop pretty low in a very cold post-frontal
airmass.  However, they won`t reach their full radiational cooling
potential due to sfc and low level winds staying elevated
overnight.  Expect low temps in the upper teens and lower 20s
tonight...potentially colder than that in locations which still have
a light snow coating on the ground.

For Saturday, temperatures will rebound back into the upper 30s and
lower 40s for highs as the cold airmass will already be beginning to
moderate under sunny skies.

Saturday night expect another clear calm night with sfc winds
turning to the south ahead of the next weather system.  Lows will be
in the 20s to around 30.

.Long Term (Sunday - Friday)...
Issued at 320 PM EST Fri Dec 21 2012

...First Significant Snow Possible the Day after Christmas...

Sunday will be dry with temperatures a few degrees above normal
across the region. Clouds will be on the increase from the south as
a shortwave and low pressure system develop to the west. Rain will
spread into southern KY Sunday night and continue to overspread the
region Christmas Eve as the low tracks across the forecast area.
With decent warm air moving in with this system, it looks like it
will be an all rain event. Highs on Monday will be in the upper 40s
to lower 50s. The rain will move out Monday night and should be out
of the area by Christmas morning. Lows Christmas morning will be in
the mid to upper 30s. Christmas will be mainly dry, with just a few
showers moving into south central Kentucky during the afternoon as
the next low pressure system begins to move in. Highs will be in the
40s.

The more significant low pressure system will move through on
Wednesday. This low will track across east central Kentucky,
probably just west of the Appalachians through the day on Wednesday
and move up the east coast Wednesday night into Thursday morning.
This system will pull in much colder air on the back side of it. The
models have been fairly consistent in showing some accumulating snow
will be possible across the forecast area with this system. However,
the amount of snow we be will be highly dependent on the low track
and where the deformation band sets up on the back side of this low.
Precipitation will likely start off as all rain on Tuesday night and
then transition to a mix Wednesday morning and then all snow before
ending on Wednesday night. Anyone with travel plans for the day
after Christmas should be sure to check back for updates on this
system as we get closer to the event.

Thursday and Friday will be be much colder with highs in the 30s and
lows in the teens to twenties.

&&

.Aviation (06Z TAF Issuance)...
Issued at 1240 AM EST Sat Dec 22 2012

Strong surface low continues to move into Quebec with high pressure
becoming established across the Mississippi River Valley. The
resultant pressure gradient is starting to gradual weakening this
morning as the low continues to push northeast. Northwest winds will
back to a more west-southwesterly direction between 5 and 10 mph by
about mid morning, as the center of the surface high passes by to
our south.

Lingering cyclonic stratus deck is trying to make southward
progress. Do not think it will push too much further south, with SDF
remaining on the southern edge and LEX overcast until the deck
scatters and shifts northeast later this morning. Models are not
handling this situation well, with the RAP having the best solution.
However, it seems to be currently overdoing the clouds at SDF. Will
continue to monitor. Otherwise, only expect a few upper-level clouds
streaming overhead today.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
KY...NONE.
$$


Update...........BJS
Short Term.......AMS
Long Term........EER
Aviation.........MJP






AREA FORECAST DISCUSSION

NWS WAKEFIELD VA

 1003 PM EST SUN DEC 23 2012

.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTHEAST ACROSS THE MID ATLANTIC STATES
CHRISTMAS EVE...WITH HIGH PRESSURE REBUILDING OVER THE AREA FOR
CHRISTMAS DAY. A STRONGER AREA OF LOW PRESSURE TRACKS THROUGH THE
TENNESSEE VALLEY CHRISTMAS NIGHT...THEN CONTINUES ACROSS THE MID
ATLANTIC ON WEDNESDAY...WITH ITS ASSOCIATED COLD FRONT PUSHING
OFF THE COAST EARLY THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
LATEST WX ANALYSIS REVEALS BROAD AREA OF SFC HIGH PRESSURE, THE
CENTER OF WHICH WAS ORIENTED ALONG THE ATLANTIC COAST OF FLORIDA
AND OFF THE SOUTHEAST COAST. ALOFT, UA ANALYSIS SHOWS QUASI-ZONAL
FLOW CONTINUES ACROSS THE EASTERN 2/3 OF THE COUNTRY. FAST FLOW
ALOFT HAS ALLOWED FOR QUICK INCREASE OF MID TO HIGH LEVEL
CLOUDINESS AHEAD OF A DISTURBANCE ACROSS GA AND UPSTATE SC THIS
EVE, WITH INCREASING CLOUDS OVER THE SOUTHERN HALF OF THE FORECAST
AREA. FARTHER NORTH, CLEAR/MCLEAR SKY PERSISTS OVER FAR NORTHERN
TIER OF CWA. THIS CLEARING IS ALLOWING FOR BETTER RADIATING
CONDITIONS AND SIGNIFICANTLY COOLER CONDITIONS OVER THE LWR
EASTERN SHORE AND FARTHER NORTH INTO THE NORTH MID-ATLANTIC.

RADAR MOSAIC SHOWING SOME VERY LIGHT RETURNS OVER WESTERN
CAROLINAS IN ASSOCIATION WITH SOME WEAK FORCING AHEAD OF THE
SYSTEM. HOWEVER, ANTECEDENT DRY LLVL AIRMASS, AND DOWNSLOPE (WEST)
FLOW ALOFT, IS NOT ALLOWING MUCH OF THIS ACTIVITY TO REACH THE
GROUND THUS FAR. RUC SEEMS TO BE HANDLING THIS SLOWER ONSET OF
POPS WELL OVER OUR REGION, AND HAVE LEANED ON ITS GUIDANCE
OVERNIGHT. SINCE ACCUMULATING PCPN APPEARS RATHER UNLIKELY
OVERNIGHT, HV REMOVED MENTION OF POPS BEFORE 12Z/7AM MONDAY, BUT
NOT OUT OF THE QUESTION TO SEE A FEW SPRINKLES ACROSS THE PIEDMONT
NEAR DAWN MONDAY MORNING. ALL MINIMA ACROSS THIS AREA WILL BE
ABOVE FREEZING AND MDL THERMAL PROFILES RMN WARM ENOUGH TO
PRECLUDE ANY PRECIP TYPE ISSUES OVER THE LOCAL AREA WITH ANY LGT
PCPN THAT OCCURS. EARLY MORNING LOW TEMPS TO RANGE FROM U20S/NR 30
ACROSS THE EASTERN SHORE TO U30S/NR 40 ACROSS SE VA/NE NC.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
LO PRES CONTS TO MOVE TO THE NE TWD/INTO NEW ENG MON AFTN/NGT.
ASSOCIATED MSTR AXIS TO SWING (W-E) ACRS THE FA DURG MON...W/
HIGHEST POPS (60-70%) NW PORTION OF FA...TAPERING TO TO 25-30%
XTRM SE VA/CSTL NE NC. QUITE THE TEMP GRADIENT XPCD ON MON...W/ HI
TEMPS FM THE L/M40S FAR NW...TO THE M/U50S SE. DRYING OUT QUICKLY
FM SW TO NE MON NGT...LEADING TO DRY WX ON TUE W/ TEMPS AVGG A
FEW DEGS F ABV NRML (TOPPING OUT IN THE L/M50S).

NEXT STRONGER LO PRES SYS WILL BE DVLPG INVOF W/CNTRL GULF STATES
LT TUE INTO TUE NGT...THEN IS FCST TO TRACK TO THE NE INTO THE ERN
OH VLY BY WED AFTN. MDLS CONT TO TREND WARMER AND HAVE PARENT LO W
OF THE MTNS (ON ITS WAY NE). WRMFNT TO LIFT N INTO/THROUGH THE FA ON
WED AIDED BY INCRSG SE THEN S WNDS. MAIN AREA OF MID LVL DYNAMICS
TO REACH THE FA WED AFTN AS RIBBON OF HIGHER SFC DEWPTS/LLVL
INSTABILITY WOULD BE SURGING NWD. THEREFORE...THOUGH IT BEING LT
DEC...CONCERN IS FOR PSBL CNVTN AND PD OF MDT/HVY RA AHD OF/WITH
CDFNT TO THE AREA DURG WED AFTN. WILL (STRNG) T PTNTL BE INCRSD BY
TRIPLE POINT LO MOVING NNE OVR THE PIEDMONT? FOR NOW...WILL HAVE
80% POPS...AND INCLUDE CHC T FOR SRN HALF OF VA/NE NC (WED AFTN).
HI TEMPS WED FM THE U40S/ARND 50F NW (WELL INLAND)...TO THE U60S/ARND
70F IN XTRM SE VA/CSTL NE NC.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
DECENT MODEL AGREEMENT WED NIGHT WITH A QUICK COLD FRONTAL PASSAGE
AS DEEPENING LOW PRESSURE QUICKLY MOVES NORTHEAST OF THE REGION.
KEPT CHC EVE POPS AHEAD OF FROPA. CAA KICKS IN ALLOWING DRY SLOT TO
PUNCH NE AND CUT PCPN OFF AFTR MIDNITE. LOWS IN THE 30S.

THURSDAY APPEARS TO BE ANOTHER DAY LIKE SATURDAY WAS. STRNG PRS
GRDNT ARND DEPARTING LOW RESULTS IN A BREEZY/WINDY DAY WITH PTNTL
FOR GUSTS OVER 30 MPH INLAND AND GALE FORCE WINDS OVER THE WATERS.
PT SUNNY AS COLD AIR ALOFT RESULTS IN SC DVLPMNT DRNG THE DAY. KEPT
IT DRY WITH HIGHS IN THE 40S TO L50S SERN CNTYS.

HIGH PRS BUILDS INTO THE AREA THURS NITE & FRI. THIS KEEPS IT DRY
WITH DMNSHG WINDS. LOWS THURS NITE M20S-L30S. HIGHS FRI IN THE 40S.

MODELS THEN DIVERGE BY NEXT WEEKEND AS YET ANTHR (WEAKER) SYSTM
EJECTS OUT OF SW THEN MOVES ACROSS THE SRN CONUS. ECMWF QUICKER IN
BRINGING PCPN IN FRI NITE WITH THE GFS GIVING THE REGION THE OLD
SPLIT IN PCPN BATCHES SAT. WILL KEEP LOW CHC (LIQUID) POPS IN FOR
SAT. SOME P-TYPE ISSUES ARE PSBL IF PCPN COMES IN A BIT FASTER FRI
NITE. LOWS FRI NITE U20S-M30S. HIGHS SAT IN THE 40S AND 50S. COLDER
BEHIND SYSTM SUNDAY. LOWS SAT NITE M20S-M30S. HIGHS SUN IN THE
40S.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
MID AND HIGH LEVEL CLOUDS WILL CONTINUE TO INCREASE OVERNIGHT. WINDS
WILL REMAIN LIGHT OVERNIGHT AS A WEAK BACK DOOR BOUNDARY WILL MOVE
SOUTH TO THE VA/NC BORDER DURING THE EARLY MORNING HOURS...TURNING
WINDS TO THE NE/E. THE BOUNDARY WASHES OUT IN OUR AREA AS LOW
PRESSURE MOVES THE TENNESSEE AND OHIO VALLEYS AND TURNS WINDS TO THE
SE/S. AN AREA OF LIGHT RAIN WILL SPREAD INTO THE MID ATLANTIC STATES
...MAINLY AFFECTING WRN AND NRN PORTIONS OF THE AREA. CONDITIONS MAY
LOWER TO MVFR ESPECIALLY AT RIC/SBY. THERE IS LITTLE INDICATION OF
ANY IFR MONDAY.

OUTLOOK...THE PRECIPITATION QUICKLY MOVES OUT OF THE AREA MONDAY
EVENING. MVFR CONDS MAY LINGER MONDAY NIGHT WITH VFR BY TUESDAY
MORNING.

A MORE SIGNIFICANT WEATHER SYSTEM WILL AFFECT THE REGION LATE TUE
NIGHT THRU WED WITH PERIODS OF RAIN AND AREAS OF IFR LIKELY.

&&

.MARINE...
SW WINDS INCREASED THIS EVENING TO AROUND 15 KNOTS ACROSS THE
BAY. THESE WINDS SHOULD SLOWLY DIMINISH AS A WEAK COLD FRONT
APPROACHES AND THEN MOVES THROUGH DURING THE EARLY MORNING HOURS.
A BRIEF SURGE DOWN THE BAY (FROM THE NORTH) PSBL FOLLOWING THE
FRONTAL PASSAGE DURING THE PREDAWN HOURS...EXPECT THIS TO REMAIN
AOB 15 KTS. VRBL WIND FLOW AOB 15 KTS SETS UP MON AND TUES AS NEXT
SYSTEM MOVES ACROSS THE AREA.

NEXT STRONGER SYSTEM PROGGED TO MOVE ACROSS THE RGN BY MID WEEK.
INCRSG E-SE FLOW AHEAD OF IT WILL LIKELY RESULT IN SCA HEADLINES
BEGINNING WED. STRONG CAA BEHIND A COLD FRONT RESULTS IN A STRONG
SCA WED NITE AND THURS WITH POTENTIAL FOR GALE FORCE GUSTS THURS.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...ALB/MAM
NEAR TERM...ALB/MAM
SHORT TERM...ALB
LONG TERM...MPR
AVIATION...LSA
MARINE...LSA/MPR







AREA FORECAST DISCUSSION

NWS WAKEFIELD VA

 1001 PM EST SUN DEC 23 2012

.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTHEAST ACROSS THE MID ATLANTIC STATES
CHRISTMAS EVE...WITH HIGH PRESSURE REBUILDING OVER THE AREA FOR
CHRISTMAS DAY. A STRONGER AREA OF LOW PRESSURE TRACKS THROUGH THE
TENNESSEE VALLEY CHRISTMAS NIGHT...THEN CONTINUES ACROSS THE MID
ATLANTIC ON WEDNESDAY...WITH ITS ASSOCIATED COLD FRONT PUSHING
OFF THE COAST EARLY THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
LATEST WX ANALYSIS REVEALS BROAD AREA OF SFC HIGH PRESSURE, THE
CENTER OF WHICH WAS ORIENTED ALONG THE ATLANTIC COAST OF FLORIDA
AND OFF THE SOUTHEAST COAST. ALOFT, UA ANALYSIS SHOWS QUASI-ZONAL
FLOW CONTINUES ACROSS THE EASTERN 2/3 OF THE COUNTRY. FAST FLOW
ALOFT HAS ALLOWED FOR QUICK INCREASE OF MID TO HIGH LEVEL
CLOUDINESS AHEAD OF A DISTURBANCE ACROSS GA AND UPSTATE SC THIS
EVE, WITH INCREASING CLOUDS OVER THE SOUTHERN HALF OF THE FORECAST
AREA. FARTHER NORTH, CLEAR/MCLEAR SKY PERSISTS OVER FAR NORTHERN
TIER OF CWA. THIS CLEARING IS ALLOWING FOR BETTER RADIATING
CONDITIONS AND SIGNIFICANTLY COOLER CONDITIONS OVER THE LWR
EASTERN SHORE AND FARTHER NORTH INTO THE NORTH MID-ATLANTIC.

RADAR MOSAIC SHOWING SOME VERY LIGHT RETURNS OVER WESTERN
CAROLINAS IN ASSOCIATION WITH SOME WEAK FORCING AHEAD OF THE
SYSTEM. HOWEVER, ANTECEDENT DRY LLVL AIRMASS, AND DOWNSLOPE (WEST)
FLOW ALOFT, IS NOT ALLOWING MUCH OF THIS ACTIVITY TO REACH THE
GROUND THUS FAR. RUC SEEMS TO BE HANDLING THIS SLOWER ONSET OF
POPS WELL OVER OUR REGION, AND HAVE LEANED ON ITS GUIDANCE
OVERNIGHT. SINCE ACCUMULATING PCPN APPEARS RATHER UNLIKELY
OVERNIGHT, HV REMOVED MENTION OF POPS BEFORE 12Z/7AM MONDAY, BUT
NOT OUT OF THE QUESTION TO SEE A FEW SPRINKLES ACROSS THE PIEDMONT
NEAR DAWN MONDAY MORNING. ALL MINIMA ACROSS THIS AREA WILL BE
ABOVE FREEZING AND MDL THERMAL PROFILES RMN WARM ENOUGH TO
PRECLUDE ANY PRECIP TYPE ISSUES OVER THE LOCAL AREA WITH ANY LGT
PCPN THAT OCCURS. EARLY MORNING LOW TEMPS TO RANGE FROM U20S/NR 30
ACROSS THE EASTERN SHORE TO U30S/NR 40 ACROSS SE VA/NE NC.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
LO PRES CONTS TO MOVE TO THE NE TWD/INTO NEW ENG MON AFTN/NGT.
ASSOCIATED MSTR AXIS TO SWING (W-E) ACRS THE FA DURG MON...W/
HIGHEST POPS (60-70%) NW PORTION OF FA...TAPERING TO TO 25-30%
XTRM SE VA/CSTL NE NC. QUITE THE TEMP GRADIENT XPCD ON MON...W/ HI
TEMPS FM THE L/M40S FAR NW...TO THE M/U50S SE. DRYING OUT QUICKLY
FM SW TO NE MON NGT...LEADING TO DRY WX ON TUE W/ TEMPS AVGG A
FEW DEGS F ABV NRML (TOPPING OUT IN THE L/M50S).

NEXT STRONGER LO PRES SYS WILL BE DVLPG INVOF W/CNTRL GULF STATES
LT TUE INTO TUE NGT...THEN IS FCST TO TRACK TO THE NE INTO THE ERN
OH VLY BY WED AFTN. MDLS CONT TO TREND WARMER AND HAVE PARENT LO W
OF THE MTNS (ON ITS WAY NE). WRMFNT TO LIFT N INTO/THROUGH THE FA ON
WED AIDED BY INCRSG SE THEN S WNDS. MAIN AREA OF MID LVL DYNAMICS
TO REACH THE FA WED AFTN AS RIBBON OF HIGHER SFC DEWPTS/LLVL
INSTABILITY WOULD BE SURGING NWD. THEREFORE...THOUGH IT BEING LT
DEC...CONCERN IS FOR PSBL CNVTN AND PD OF MDT/HVY RA AHD OF/WITH
CDFNT TO THE AREA DURG WED AFTN. WILL (STRNG) T PTNTL BE INCRSD BY
TRIPLE POINT LO MOVING NNE OVR THE PIEDMONT? FOR NOW...WILL HAVE
80% POPS...AND INCLUDE CHC T FOR SRN HALF OF VA/NE NC (WED AFTN).
HI TEMPS WED FM THE U40S/ARND 50F NW (WELL INLAND)...TO THE U60S/ARND
70F IN XTRM SE VA/CSTL NE NC.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
DECENT MODEL AGREEMENT WED NIGHT WITH A QUICK COLD FRONTAL PASSAGE
AS DEEPENING LOW PRESSURE QUICKLY MOVES NORTHEAST OF THE REGION.
KEPT CHC EVE POPS AHEAD OF FROPA. CAA KICKS IN ALLOWING DRY SLOT TO
PUNCH NE AND CUT PCPN OFF AFTR MIDNITE. LOWS IN THE 30S.

THURSDAY APPEARS TO BE ANOTHER DAY LIKE SATURDAY WAS. STRNG PRS
GRDNT ARND DEPARTING LOW RESULTS IN A BREEZY/WINDY DAY WITH PTNTL
FOR GUSTS OVER 30 MPH INLAND AND GALE FORCE WINDS OVER THE WATERS.
PT SUNNY AS COLD AIR ALOFT RESULTS IN SC DVLPMNT DRNG THE DAY. KEPT
IT DRY WITH HIGHS IN THE 40S TO L50S SERN CNTYS.

HIGH PRS BUILDS INTO THE AREA THURS NITE & FRI. THIS KEEPS IT DRY
WITH DMNSHG WINDS. LOWS THURS NITE M20S-L30S. HIGHS FRI IN THE 40S.

MODELS THEN DIVERGE BY NEXT WEEKEND AS YET ANTHR (WEAKER) SYSTM
EJECTS OUT OF SW THEN MOVES ACROSS THE SRN CONUS. ECMWF QUICKER IN
BRINGING PCPN IN FRI NITE WITH THE GFS GIVING THE REGION THE OLD
SPLIT IN PCPN BATCHES SAT. WILL KEEP LOW CHC (LIQUID) POPS IN FOR
SAT. SOME P-TYPE ISSUES ARE PSBL IF PCPN COMES IN A BIT FASTER FRI
NITE. LOWS FRI NITE U20S-M30S. HIGHS SAT IN THE 40S AND 50S. COLDER
BEHIND SYSTM SUNDAY. LOWS SAT NITE M20S-M30S. HIGHS SUN IN THE
40S.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
SW WINDS INCREASED THIS EVENING TO AROUND 15 KNOTS ACROSS THE
BAY. THESE WINDS SHOULD SLOWLY DIMINISH AS A WEAK COLD FRONT
APPROACHES AND THEN MOVES THROUGH DURING THE EARLY MORNING HOURS.
A BRIEF SURGE DOWN THE BAY (FROM THE NORTH) PSBL FOLLOWING THE
FRONTAL PASSAGE DURING THE PREDAWN HOURS...EXPECT THIS TO REMAIN
AOB 15 KTS. VRBL WIND FLOW AOB 15 KTS SETS UP MON AND TUES AS NEXT
SYSTEM MOVES ACROSS THE AREA.

NEXT STRONGER SYSTEM PROGGED TO MOVE ACROSS THE RGN BY MID WEEK.
INCRSG E-SE FLOW AHEAD OF IT WILL LIKELY RESULT IN SCA HEADLINES
BEGINNING WED. STRONG CAA BEHIND A COLD FRONT RESULTS IN A STRONG
SCA WED NITE AND THURS WITH POTENTIAL FOR GALE FORCE GUSTS THURS.

&&

.MARINE...
NO HEADLINES IN THE SHORT TERM DESPITE A COLD FRONT PASSAGE TONIGHT.
NOT MUCH CAA EXPECTED BUT LATEST DATA SUGGESTS A BRIEF SURGE DOWN
THE BAY PSBL AFTER MIDNIGHT...EXPECT THIS TO REMAIN AOB 15 KTS.
VRBL WND FLOW AOB 15 KTS SETS UP MON AND TUES AS NEXT SYSTM MOVES
ACROSS THE AREA.

NEXT STRNGR SYSTM PROGGED TO MOVE ACROSS THE RGN BY MID WEEK. INCRG
E-SE FLOW AHEAD OF IT WILL LIKELY RESULT IN SCA HEADLINES BEGINNING
WED. STRNG CAA BEHIND A COLD FRONT RESULTS IN A STRNG SCA WED NITE
AND THURS WITH PTNTL FOR GALE FORCE GUSTS THURS.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...ALB/MAM
NEAR TERM...ALB/MAM
SHORT TERM...ALB
LONG TERM...MPR
AVIATION...LSA
MARINE...MPR









AREA FORECAST DISCUSSION

NWS MARQUETTE MI

 608 PM EST SUN DEC 23 2012

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 350 PM EST SUN DEC 23 2012

WV IMAGERY AND RUC ANALYSIS INDICATED CONFLUENT WNW MID/UPPER LEVEL
FLOW THROUGH THE NRN GREAT LAKES BETWEEN A TROUGH FROM JAMES BAY
INTO QUEBEC AND A RIDGE INTO THE UPPER MS VALLEY. AN UPSTREAM
SHORTWAVE TROUGH OVER NORTH DAKOTA SUPPORTED AN AREA OF SNOW OVER
WRN AND NRN ND. NW FLOW LES HAD DIMINISHED OVER CNTRL UPPER MI AS A
SFC RIDGE BUILDS INTO THE AREA WITH DRY ADVECTION...LOWERING
INVERSION HEIGHTS...BACKING WINDS AND INCREASING ACYC FLOW. FARTHER
EAST...LES LINGERED INTO THE EAST(ERY/ANJ) WITH VSBY STILL IN THE
2-4SM RANGE.

DEVELOPING LAND BREEZES TONIGHT COULD PROVIDE FOCUS FOR LES BANDS
OVER SHORELINE AREAS EAST OF MUNISING IN WNW FLOW...BUT WILL ONLY
MAINTAIN SLIGHT CHANCE POPS GIVEN MARGINAL INSTABILITY WITH LAKE 850
MB TEMPS NEAR -12C AND DRY LOW-LVL AIR BLO LOW INVERSION HEIGHTS OF
4K FT.

LATE TONIGHT AND MONDAY...AS THE ND SHRTWV MOVES THROUGH UPPER MS
VALLEY TONIGHT INTO WI ON MONDAY...THE STRONGEST 700-300 MB QVECTOR
CONV IS EXPECTED TO REMAIN TO THE SOUTH WITH THE MOST FAVORABLE
MOISTURE PROFILE FOR PCPN THROUGH NRN WI AND FAR SRN UPPER MI. MODELS
CONSENSUS QPF AND FAVORS CONTINUATION OF HIGHEST POPS THROUGH THE
SRN TIER OF COUNTIES. EVEN THOUGH PCPN AMOUNTS OF ONLY AROUND 0.05
INCH OR SNOWFALL OF AN INCH OR LESS IS EXPECTED...POPS WERE BOOSTED
INTO THE 50-65 RANGE OVER THE SOUTH. WITH 850 MB TEMPS TO NEAR
-14C...SOME ADDITIONAL LES WILL BE POSSIBLE FOR NW FLOW FAVORED
LOCATIONS DOWNWIND OF LAKE SUPERIOR. LOW INVERSION HEIGHTS AOB 4K FT
AND AN UPSTREAM 850-800 MB DRY LAYER WILL LIMIT LES INTENSITY AND
ONLY CHANCE POPS WERE MENTIONED.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 350 PM EST SUN DEC 23 2012

CHRISTMAS EVE NIGHT/CHRISTMAS/CHRISTMAS NIGHT...WAVE THAT BRINGS LGT
SNOW TO PORTIONS OF THE AREA ON MONDAY EXITS CHRISTMAS EVE EVENING.
H85-H6 MOISTURE LINGERS OVER EASTERN CWA MONDAY EVENING BUT THERE
REALLY IS NOT MUCH LIFT WITHIN THE DEEPER MOISTURE. NORTHWEST WINDS
RESULT IN POTENTIAL LK EFFECT ALONG LK SUPERIOR. SOUNDINGS A BIT
MORE FAVORABLE OVER ALGER/NORTHERN SCHOOLCRAFT DUE TO SLIGHTLY
HIGHER INVERSION AROUND 5KFT AND TEMPS AT INVERSION TOP AROUND -16C.
NAM AT MUNISING/P53 SHOWS LAKE INDUCED CAPES OVER 300 J/KG WITH
PORTION OF LAKE CLOUD LAYER IN DGZ. WITH EXPECTED SFC WINDS FAVORING
ENAHNCED CONVERGENCE...INCREASED POPS TO LIKELY OVR ALGER AND
NORTHERN SCHOOLCRAFT INTO TUESDAY MORNING. ACCUMS WILL MAINLY BE
LIGHT BUT THERE COULD BE A FEW INCHES OF SNOW. DESPITE BEING LK
EFFECT...SLR/S STAY MORE TOWARD 15:1. LOWER INVERSIONS FCST IN THE
WEST AND NOT AS MUCH MOISTURE WILL LIMIT LK EFFECT OVER THE WEST. BY
LATER ON CHRISTMAS DAY WINDS BACK TO MORE OF A WEST NORTHWEST
DIRECTION. KEPT POPS IN THE HIGH CHANCE/LOWER LIKELY RANGE BUT
ADJUSTED BASED ON EXPECTED LOW-LEVEL WIND DIRECTION. AWAY FM THE LK
EFFECT CONCERNS...A MORE WEST WIND INITIALLY TUESDAY NIGHT WILL
ALLOWS INTERIOR AREAS TO HAVE CHANCE OF FALLING BLO ZERO FOR MIN
TEMPS. WINDS TURN MORE NORTHERLY LATE...BUT GIVEN LIGHT SYNOPTIC
WINDS AND PWATS BLO 50 PCT OF NORMAL...TEMPS OVER INLAND AREAS COULD
STILL FALL OFF VERY QUICKLY IN THE EVENING. INTRODUCED SOME SUB ZERO
LOWS ALONG WI BORDER...BUT WHERE SKIES ARE MOSTLY  CLEAR...COULD SEE
READINGS THIS LOW CLOSER TO LK SUPERIOR AND OVER INTERIOR EAST AS
WELL.

WEDNESDAY THROUGH THURSDAY...LATEST RUN OF GFS REMAINS CONSISTENT IN
INDICATING SOUTHERN PLAINS INTO LOWER MISSISSIPPI RIVER VALLEY
SNOWSTORM TRACKING FARTHER WEST AS IT HEADS TOWARD GREAT LAKES
MIDWEEK. LATEST GFS BRINGS SFC LOW JUST SOUTHEAST OF DETROIT
WEDNESDAY AFTN AS DOES THE NAM. HPC GUIDANCE INDICATES SEVERAL
INCHES OF SNOW OVER SOUTHEAST LOWER MICHIGAN WITH THIS STORM. GFS
ALSO ALLOWS ENOUGH OF CONNECTION OF NORTHERN AND SOUTHERN BRANCH
WAVES TO RESULT IN STRONGER INVERTED TROUGH ACROSS THE UPPER GREAT
LAKES REGION THROUGH THURSDAY MORNING. RESULT IS SYNOPTIC SNOW
SHIELD GRAZING EASTERN CWA WEDNESDAY AFTN AND PUSHING AS FAR WEST AS
ESC/MNM/SAW WEDNESDAY NIGHT. ECMWF AND GEM-NHEM FARTHER TO THE
EAST...AS ARE ENSEMBLES OF GFS/ECMWF AND CANADIAN. FARTHER WEST IDEA
ALSO HAS BEARING ON ONGOING LK EFFECT. GFS DOES NOT SHOW ALL THAT
MUCH RESPONSE FOR THE NORTHEAST FLOW LK EFFECT AS INVERSION HEIGHTS
STAY BLO 5KFT INTO THURSDAY. COULD SEE GFS IDEA SUPPORTING SEEDER
FEEDER ENHANCED SNOW ALONG LK SUPERIOR. LITTLE CHANGE IN
INVERSION/LAKE INSTABILITY...SO WENT FOR SIMILAR LOOK TO LK EFFECT
POPS AS IS IN THE FORECAST FOR MONDAY NIGHT THROUGH TUESDAY NIGHT.
DEPENDING ON THE LOW-LEVEL WINDS...ISOLD SPOTS MAY PICK UP A FEW
MORE INCHES OF LK EFFECT SNOW. EVENTUALLY... LK EFFECT SHOULD BECOME
MORE DISORGANIZED LATER THURSDAY/THURSDAY NIGHT AS SFC-H85 WINDS
SHOW MORE SHEAR AND ARE NOT AGREED UPON WELL BY ECMWF OR GFS. WILL
CONTINUE PREVIOUS SHIFTS IDEA OF TRENDING DOWN THE LK EFFECT BY
THURSDAY.

FRIDAY THROUGH NEXT WEEKEND...RECENT RUNS OF ECMWF HAD BEEN
INDICATING PHASING OF SOUTHERN BRANCH AND NORTHERN BRANCH WAVES
HELPING TO PUSH SFC LOW INTO CNTRL GREAT LAKES FOR SATURDAY WITH
SYNOPTIC SNOW OVER UPR MICHIGAN. 00Z ECMWF WAS SLIGHTLY FARTHER
SOUTH WITH MID-LEVEL/SFC LOWS AND SLOWER WITH ARRIVAL OF SNOW. 12Z
ECMWF CONTINUES THAT TREND AND NOW LOOKS MORE LIKE OTHER GUIDANCE
INCLUDING GFS/GEM/ECMWF ENSEMBLES BY SHOWING LESS PHASING AND A MORE
SUPRESSED SFC LOW MOVING FROM SOUTHERN PLAINS ACROSS OHIO VALLEY
FRIDAY AND TOWARD EAST COAST ON SATURDAY. SHORTWAVE TROUGH THAT WILL
BE RESPONSIBLE FOR THIS SYSTEM IS STILL OVER PACIFIC SOUTH OF THE
ALLUTIAN ISLANDS...SO OBVIOUSLY PLENTY OF TIME FOR CHANGES TO OCCUR.
LOW CHANCE CONSENSUS POPS WORK FOR NOW GIVEN THE UNCERTAINTY WITH
THE SYSTEM AND POSSIBLE LK EFFECT ALONG LK SUPERIOR.
&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 608 PM EST SUN DEC 23 2012

WITH A STRONG INVERSION OVER THE AREA...THE CLOUDS AND MVFR CIG WILL
PERSIST TONIGHT INTO MONDAY. A SHORTWAVE TROUGH MOVING TOWARD THE
REGION MONDAY WILL BRING THE POTENTIAL FOR MORE WIDESPREAD SNOW WITH
MVFR VISIBILITIES IN LIGHT SNOW AT ALL SITES.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 350 PM EST SUN DEC 23 2012

A TIGHT PRES GRADIENT BTWN A RIDGE INTO THE UPPER MS VALLEY AND LOW
PRESSURE OVER HUDSON BAY RESULTING NORTHWEST WINDS TO 30 KNOTS OVER
EASTERN LAKE SUPERIOR WILL WEAKEN THIS EVENING ALLOWING WINDS TO
DIMINISH. A HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL
BUILD INTO THE UPPER GREAT LAKES FROM TONIGHT INTO THE MIDDLE OF
NEXT WEEK...KEEPING WINDS AT OR BELOW 25 KNOTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...JLB
LONG TERM...JLA
AVIATION...07
MARINE...JLB







AREA FORECAST DISCUSSION

NWS MARQUETTE MI

 344 PM EST SAT DEC 22 2012

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 341 PM EST SAT DEC 22 2012

WV IMAGERY AND RUC ANALYSIS INDICATED NW MID/UPPER LEVEL FLOW
BETWEEN A TROUGH OVER JAMES BAY INTO QUEBEC AND A RIDGE OVER THE
WESTERN PLAINS. A SHORTWAVE TROUGH WAS LOCATED OVER NW ONTARIO
BETWEEN LAKE WINNIPEG AND THUNDER BAY ONTARIO. THE SHRTWV AND AN
ASSOCIATED COLD FRONT INTO NRN MN SUPPORTED SOME LIGHT SNOW OR
FLURRIES INTO FAR NRN WITH VISIBILITIES GENERALLY AT OR ABOVE 5SM.
VIS SATELLITE LOOP SHOWED MAINLY JUST MID CLOUDS SPREADING ACROSS
UPPER MI ASSOCIATED WITH 285K-295K ISENTROPIC LIFT AHEAD OF THE
TROUGH.

AS THE SHRTWV DIVES TO THE ESE AND PULLS THE COLD FRONT THROUGH
UPPER MI...WINDS WILL VEER FROM W TO NNW. 925-850 MB MOISTURE WILL
ALSO QUICKLY INCREASE ACROSS THE AREA. DESPITE THE RELATIVELY
SHALLOW COLD AIR MASS WITH INVERSION HEIGHTS OF ONLY 4K-5K
FT...EXPECT LES TO INCREASE THIS EVENING AND PEAK LATE TONIGHT AND
EARLY SUNDAY. LAKE INDUCED CAPES BUILD INTO THE 200-300 J/KG RANGE
BUT THE CLOUD LAYER REMAINS MAINLY BELOW THE DGZ. SO...ONLY INCLUDED
SCT/CHANCE POPS WITH ANY ACCUMULATIONS AT OR BELOW A HALF INCH.

LES SHOULD DIMINISH FROM WEST TO EAST BY MIDDAY INTO SUNDAY
AFTERNOON AS HIGH PRES BUILDS INTO THE REGION WITH LOWERING
INVERSION HEIGHTS TO AROUND 3K FT AND INCREASINGLY
ANTICYCLONIC/DIVERGENT LOW LEVEL FLOW.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 341 PM EST SAT DEC 22 2012

SPLIT FLOW IN PLACE TO START THE LONG TERM. SUBTROPICAL H2 JET IS
ALONG SOUTHERN TIER OF CONUS WHILE NORTHERN STREAM H4-H3 JET RIDES
ACROSS CANADA WITH BROAD UPPER LOW FM HUDSON BAY ACROSS QUEBEC. CORE
OF LOW-LEVEL COLD AIR BENEATH THAT LOW...BUT DEVELOPING NW WINDS IN
WAKE OF FRONT THAT PASSES ACROSS TONIGHT...RESULTS IN ENOUGH OVER
WATER INSTABILITY WITH LAKE-900MB DELTA T/S AOA 15C FOR LK EFFECT SNOW
SHOWERS. AS MENTIONED IN THE SHORT TERM DISCUSSION...INVERSIONS LESS
THAN 5KFT RESULTING FM LARGE SCALE RISING HEIGHTS/SUBSIDENCE AND
ANTICYCLONIC FLOW WILL BE LIMITING FACTORS FOR ANYTHING OTHER THAN
LIGHT SNOW ACCUMS...MAINLY UNDER 1 INCH.

LATER SUNDAY NIGHT AND INTO MONDAY COUPLE OF SHORTWAVES EMERGE
ACROSS MIDDLE CONUS...ONE DIGGING FROM WYOMING TO NORTHERN ILLINOIS
AND THE OTHER SLIDING FROM OK/TX PANHANDLE TO TENNESSEE. OVERALL
MODELS HAVE TRENDED STRONGER WITH NORTHERN WAVE. GFS/NAM/UKMET
STRONGER WITH NORTHERN ONE INITIALLY BUT LAST COUPLE RUNS OF ECMWF
ALSO SHOW SOME IMPACT FOR UPR MICHIGAN ON CHRISTMAS EVE DAY. HAVE
LOW CHANCE POPS EVERYWHERE DUE TO SYSTEM SNOW AND/OR LK EFFECT.
IF TRENDS CONTINUE...POPS MAY NEED INCREASING FOR HIGH POP/LOW QPF
SETUP. MOISTURE IS LIMITED WITH NORTHERN END OF SYSTEM SO ANY SNOW
AMOUNTS WILL BE LESS THAN AN INCH. LK EFFECT AREAS MAY SEE A BIT
MORE SNOW DUE TO WEAK LAKE ENHANCEMENT...THOUGH GFS/NAM SOUNDINGS
REALLY DO NOT SHOW MUCH LAKE RESPONSE FROM THE SYSTEM IN TERMS OF A
HIGHER INVERSION.

LK EFFECT MAY PICK UP SLIGHTLY IN WAKE OF SYSTEM MOVING THROUGH
ON MONDAY AS ECMWF/GFS/NAM INDICATE H85 TEMPS FALLING TO AROUND -15C
MONDAY NIGHT AND TUESDAY. INVERSIONS REMAIN LOWER THAN 5KFT THOUGH
WHICH WILL LIMIT SNOW ACCUMS TO JUST A FEW INCHES. VERY LITTLE
CHANGES IN LARGE SCALE/MESOSCALE PATTERN THROUGH THURSDAY SO EXPECT
PERSISTENT/STEADY STATE LIGHT LK EFFECT ALONG LK SUPERIOR. LATEST
GFS/ECMWF RUNS IN GOOD AGREEMENT WITH TRACK OF SFC LOW LIFTING FM
TENNESSEE RIVER VALLEY ACROSS THE NORTHEAST CONUS WEDNESDAY INTO
THURSDAY. SYNOPTIC SNOW ON NORTHWEST PERIFERY OF SYSTEM STAYS MAINLY
TO THE EAST OF UPR MICHIGAN. 12Z GFS FARTHER NORTHWEST...GRAZING
EASTERN CWA WITH LGT QPF ON WEDNESDAY. GFS IS AN OUTLIER COMPARED TO
ECMWF/GEM-NHEM AND EVEN PREVIOUS RUNS OF GFS. WILL JUST STICK WITH
SCATTERED POPS FOR NORTH-NORTHWEST FLOW LK EFFECT. NUDGED POPS UP
SOME ALONG LK SUPERIOR OVER THE CONSENSUS WITH EXPECTED LK EFFECT.

NEXT CHANCE OF WIDESPREAD SYNOPTIC SNOW COULD BE FRIDAY NIGHT INTO
NEXT SATURDAY IF ECMWF IS CORRECT. ECMWF REMAINS CONSISTENT SHOWING
ACTIVE SOUTHERN STREAM SENDING ANOTHER UPR TROUGH/SFC LOW OUT OF THE
PLAINS ACROSS THE WESTERN GREAT LAKES. NORTHERN STREAM WAVE DIGGING
INTO THE NORTH SIDE SYSTEM AS WELL. GEM-NHEM SIMILAR THROUGH 12Z
FRIDAY BUT GFS IS STUBBORNLY NOT DEVELOPING THE SYSTEM AS IT IS NOT
AS WRAPPED UP WITH SOUTHERN STREAM WAVE COMPARED TO ECMWF AND IT
ALSO HAS MORE SEPARATION BTWN THE NORTHERN AND SOUTHERN BRANCH
STREAMS THROUGH SATURDAY. GIVEN PAST TRACK RECORD IN DAYS 4-7...A
FEW CONSECUTIVE RUNS OF ECMWF SHOWING SOMETHING IS GOOD ENOUGH TO
INCLUDE IT IN EXTENDED. CONSENSUS POPS WERE NOT TOO BAD BUT DID
INCREASE THEM SLIGHTLY ON SATURDAY SO CHANCE FOR SNOW IS IN THERE
FOR ALL CWA. COLDER AIR BEHIND THE SYSTEM MAY RESULT IN PROLONGED LK
EFFECT EVENT JUST BEYOND DAY 7. CERTAINLY NO THAWS IN STORE FOR LAST
WEEK OF 2012 WITH DAYTIME HIGHS IN THE TEENS/20S AND NIGHTIME LOWS
IN SINGLE DIGITS TO TEENS. RECENTLY DEPOSITED SNOW WILL STAY AROUND
UNTIL FURTHER NOTICE.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1255 PM EST SAT DEC 22 2012

DRY WESTERLY FLOW WITH A SFC RIDGE MOVING INTO THE AREA HAS
SCOURED OUT MVFR CIGS LEAVING MAINLY MID CLOUDS OVER THE REGION.

AS A COLD FRONT SWEEPS ACROSS UPPER MICHIGAN THIS EVENING...WINDS
ARE EXPECTED TO VEER TO THE NORTHWEST AND LEAD TO MVFR CEILINGS AND
LAKE EFFECT SNOW AT KCMX/KIWD. WITH ONLY LIMITED CONFIDENCE ON
AMOUNT OF VISIBILITY RESTRICTION...FCST ONLY MENTIONS HIGH END MVFR
AT THIS POINT. EVEN THOUGH KSAW IS LESS LIKELY TO SEE LAKE EFFECT
SNOW WITH THE GENERALLY NORTHWEST WINDS...CIGS INTO THE MVFR RANGE
ARE STILL EXPECTED.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 341 PM EST SAT DEC 22 2012

WINDS ARE EXPECTED TO INCREASE UP TO 30 KNOTS OUT OF THE NORTHWEST
TONIGHT INTO SUNDAY AS A COLD FRONT SWEEPS SOUTHEAST ACROSS LAKE
SUPERIOR. A HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL THEN
BUILD INTO THE UPPER GREAT LAKES FROM SUNDAY NIGHT INTO THE
THE FIRST HALF OF NEXT WEEK...KEEPING WINDS AT OR BELOW 25 KNOTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...JLB
LONG TERM...JLA
AVIATION...JLB
MARINE...JLB









AREA FORECAST DISCUSSION

NWS MARQUETTE MI

 1256 PM EST SAT DEC 22 2012

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 451 AM EST SAT DEC 22 2012

FAIRLY QUIET WEATHER PATTERN IN STORE FOR TODAY AND TONIGHT AS A
WEAK HIGH PRESSURE RIDGE CONTINUES TO SLIDE ACROSS THE CWA TODAY
AND THEN A WEAK COLD FRONT MOVES THROUGH TONIGHT.

THE WEAK HIGH PRESSURE RIDGE IS ASSOCIATED WITH AN UPPER RIDGE THAT
IS CURRENTLY PUSHING INTO WESTERN UPPER MICHIGAN THIS MORNING AND IS
EXPECTED TO QUICKLY SLIDE SOUTHEAST AND DISSIPATE AS A SHORTWAVE
DIVES SOUTHEAST FROM LAKE WINNIPEG TONIGHT. AT THE PRESENT
TIME...PLENTY OF LAKE EFFECT CLOUDS OVER CENTRAL AND EASTERN LAKE
SUPERIOR...AS RAP ANALYZED H925 TEMPS ARE AROUND -10C AND THERE IS
PLENTY OF MOISTURE TRAPPED UNDER THE SUBSIDENCE INVERSION. RADAR
NOT REALLY PICKING UP ON MUCH SNOW...DUE TO THE INVERSION BEING
AT/AROUND 3.5KFT...BUT THERE HAS BEEN LIGHT SNOW/FLURRIES AT THE
OFFICE EARLY THIS MORNING. FARTHER WEST...THE DRIER AIR SEEN ON THE
00Z KINL SOUNDING HAS CONTINUED TO EAT AWAY AT THE LAKE EFFECT OVER
THE WESTERN LAKE AND ALL THAT REMAINS OVER THE THIRD OF WESTERN
UPPER MICHIGAN IS STRATUS TRAPPED BELOW THE INVERSION. RAP/NAM H925
MOISTURE FIELDS SEEM TO HAVE A GOOD HANDLE ON THE BACK EDGE OF THIS
MOISTURE AND WILL FOLLOW THE IDEA OF THE CLOUD EDGE GRADUALLY
PUSHING TO THE NORTHEAST THROUGH THE DAY TODAY AS THE H925 RIDGE
BACKS WINDS TO THE WEST-SOUTHWEST. SINCE UPSTREAM MID/HIGH CLOUDS
WILL LIKELY AFFECT THE AREAS WHERE THE LOW CLOUDS DEPART...WON/T GO
WITH A SUNNY FORECAST AND KEEP IN MOSTLY SUNNY TO PARTLY CLOUDY
AREA.

AS FOR THE LAKE EFFECT CLOUDS AND --SHSN...MODELS NOT REALLY SHOWING
THE H925 RIDGE HAVING TOO MUCH AFFECT ON IT UNTIL THIS
AFTERNOON...EXCEPT OVER NORTH CENTRAL UPPER MICHIGAN. THE DRIER
AIR SHOULD CAUSE THE SUBSIDENCE INVERSION TO LOWER FURTHER AND
TOWARDS 2-2.5KFT OVER EASTERN LAKE SUPERIOR AND UPPER MICHIGAN.
THUS...LIKED THE PREVIOUS SHIFTS HANDLING OF PUSHING THE ISOLATED
SNOW SHOWERS EAST THROUGH THE DAY AND MAINLY FOCUSED EAST OF GRAND
MARAIS THIS AFTERNOON.

TONIGHT...FRONT ARRIVES SHORTLY AFTER SUNSET OVER THE WEST AND H925
MOISTURE SURGES BACK OVER THE AREA AND INCREASES CLOUDS. OVER THE
EAST...THERE COULD BE A BRIEF PERIOD WHERE THE SNOW COMPLETELY
ENDS LATE THIS AFTERNOON OR EARLY EVENING BEFORE THE NEXT WAVE
ARRIVES. THIS FRONT WILL DROP SOUTHEAST ACROSS THE REST OF THE CWA
DURING THE EVENING AND THE FIRST PART OF THE OVERNIGHT HOURS. WITH
WINDS VEERING TO THE NORTHWEST BEHIND THE FRONT AND COLDER AIR
SURGING BACK IN...ENHANCED BY SURFACE LOW DEVELOPING OVER
THE EASTERN LAKE...EXPECT THE LAKE EFFECT CLOUDS AND POTENTIAL SNOW
SHOWERS TO REDEVELOP LATE IN THE EVENING AND CONTINUE OVERNIGHT FOR
THE NORTHWEST TO NORTH-NORTHWEST FAVORED LOCATIONS. BEST LOW LEVEL
LAPSE RATES ARE SEEN OVER EASTERN LAKE SUPERIOR /TO 8.5C/KM /.
MODELS SHOWING SOME DIRECTIONAL SHEAR OVER THE EAST /NORTHWEST H850
WINDS AND NORTH WINDS BELOW H900/...WHICH COMBINED WITH THE FAIRLY
DRY SUB CLOUD LAYER WILL KEEP THE LAKE EFFECT FROM BECOMING
TOO STRONG /LIMITS CLOUD DEPTH TO A FEW KFT EVEN THOUGH INVERSION
HEIGHT IS NEAR 6KFT/ AND COULD ALSO INFLUENCE DEVELOPMENT. THIS IS
ESPECIALLY PREVALENT OVER THE SOUTH CENTRAL LAKE AND NORTH CENTRAL
UPPER MICHIGAN WITH THE LATEST NAM...WHILE THE GFS HAS LESS SHEAR
AND OUR LOCAL REGIONAL WRF HAS BETTER MOISTURE AND UNIDIRECTIONAL
WINDS. WITH THE DIFFERENCES...WILL CONTINUE TO MENTION A
SLIGHT/CHANCE OF SNOW SHOWERS OVER THE NORTH CENTRAL AND EAST
FAVORED LOCATIONS...WITH THE HIGHEST POPS OVER LUCE COUNTY WHERE
INCREASED CONVERGENCE WILL OCCUR WITH THE DEVELOPING SURFACE LOW.
FARTHER WEST...LAKE EFFECT CONDITIONS ARE MORE FAVORABLE IN THE
EVENING WITH BETTER LOW LEVEL MOISTURE AND INVERSION HEIGHTS TO
4.5KFT. WILL CONTINUE CHANCE POPS FOR THAT PERIOD AND THEN START TO
DIMINISH OVERNIGHT AS DRIER AIR WORKS IN. OVERALL...EXPECT MOST
LOCATIONS TO SEE LESS THAN AN INCH OF SNOW.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 451 AM EST SAT DEC 22 2012

SUNDAY AND SUNDAY NIGHT...LES CONDITIONS WILL BE LESS FAVORABLE AS
LOW-LVL FLOW BECOMES INCREASINGLY ANTICYCLONIC AND DIVERGENT AS SFC
RIDGE BUILDS INTO THE NRN PLAINS AND UPPER GREAT LAKES AREA.
INCREASING SUBSIDENCE AND INVERSION HEIGHTS LOWERING AOB 3KFT WILL
MAKE IT HARD FOR ACCUMULATING SNOW ESPECIALLY BY SUNDAY NIGHT. KEPT
IN JUST MAINLY 20-30 PCT POPS...HIGHEST EAST WHERE FETCH WILL BE
GREATER ACROSS LAKE SUPERIOR IN NW FLOW.

MON-TUE...MODELS CONTINUE TO TREND SOUTH WITH SHORTWAVE MOVING IN FM
THE NRN PLAINS LATE MONDAY INTO MON NIGHT. SOME WEAK FORCING
ASSOCIATED WITH THIS SHORTWAVE MAY PRODUCE SOME LIGHT SNOW MON INTO
MON EVENING MAINLY OVER SRN PORTIONS OF THE CWA. WITH MODELS SHOWING
850 MB TEMPS DROPPING TO -14C/-15C IN THE WAKE OF THIS
SHORTWAVE...THE ADDED INSTABILITY COULD ALSO PROVIDE A BOOST TO NNW
FLOW LES.

TUE NIGHT-THU...MODELS CONTINUE TO KEEP NEXT SYSTEM EMERGING OUT OF
SRN PLAINS/LWR MS VALLEY WELL SOUTH AND EAST OF THE GREAT LAKES
REGION WITH NO SYNOPTIC SNOW EXPECTED FOR OUR AREA. A MID-LVL TROF
AXIS FROM LOW OVER NRN CANADA IS FCST TO MOVE THROUGH THE UPPER
GREAT LAKES WED NIGHT AND THU...BUT FORCING WITH THIS FEATURE LOOKS
MINIMAL. WITH 850 MB TEMPS OF -10C/-11C CONTRIBUTING TO MARGINAL
INSTABILITY AND A WEAK NRLY FLOW...SOME LIGHT SCT LES IS POSSIBLE
DOWNWIND OF LAKE SUPERIOR OVER NRN COUNTIES. WL MAINTAIN SLIGHT CHC
POPS FOR THESE AREAS.

FRI...MODELS SHOW POTENTIAL FOR ANOTHER SIGNIFICANT MID LEVEL TROUGH
TO MOVE THROUGH THE CNTRL CONUS FOR LATE WEEK. UNCERTAINTY STILL
EXISTS WITH MODELS CONCERNING TRACK OF THIS SYSTEM. THE 00Z ECMWF
CONTINUES TO TREND WITH A MORE AMPLIFIED PATTERN THAN THE GFS...AND
WOULD INDICATE A MORE NRN TRACK WITH LEAD SHORTWAVE EMERGING OUT OF
WRN CONUS TROF. THE ECMWF SCENARIO WOULD RESULT IN A BETTER CHC OF
PCPN FOR LATE FRIDAY INTO FRIDAY NIGHT FOR OUR CWA THAN THE GFS. AT
THIS POINT...GIVEN UNCERTAINTY WILL MAINTAIN JUST SLIGHT CHC POPS
FOR LIGHT SNOW TOWARD FRI EVENING.  HOWEVER..WOULD NOT BE SURPRISED
GIVEN RECENT TRENDS...ESPECIALLY WITH THE ECMWF...THAT POPS MAY NEED
TO RAISED FOR LATE WEEK.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1255 PM EST SAT DEC 22 2012

DRY WESTERLY FLOW WITH A SFC RIDGE MOVING INTO THE AREA HAS
SCOURED OUT MVFR CIGS LEAVING MAINLY MID CLOUDS OVER THE REGION.

AS A COLD FRONT SWEEPS ACROSS UPPER MICHIGAN THIS EVENING...WINDS
ARE EXPECTED TO VEER TO THE NORTHWEST AND LEAD TO MVFR CEILINGS AND
LAKE EFFECT SNOW AT KCMX/KIWD. WITH ONLY LIMITED CONFIDENCE ON
AMOUNT OF VISIBILITY RESTRICTION...FCST ONLY MENTIONS HIGH END MVFR
AT THIS POINT. EVEN THOUGH KSAW IS LESS LIKELY TO SEE LAKE EFFECT
SNOW WITH THE GENERALLY NORTHWEST WINDS...CIGS INTO THE MVFR RANGE
ARE STILL EXPECTED.

&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 451 AM EST SAT DEC 22 2012

WINDS HAVE FALLEN BELOW GALES THIS MORNING AS THE PRESSURE GRADIENT
CONTINUES TO RELAX WITH WEAK HIGH PRESSURE RIDGE MOVING THROUGH
TODAY. WINDS ARE EXPECTED TO INCREASE UP TO 25KTS OUT OF THE
NORTHWEST TONIGHT AS A COLD FRONT SWEEPS SOUTHEAST ACROSS LAKE
SUPERIOR. HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL TRY
TO NOSE INTO THE UPPER GREAT LAKES FOR SUNDAY AND THE FIRST HALF OF
NEXT WEEK...KEEPING WINDS BELOW 25KTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...SRF
LONG TERM...VOSS
AVIATION...JLB
MARINE...SRF







AREA FORECAST DISCUSSION

NWS MARQUETTE MI

 629 AM EST SAT DEC 22 2012

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 451 AM EST SAT DEC 22 2012

FAIRLY QUIET WEATHER PATTERN IN STORE FOR TODAY AND TONIGHT AS A
WEAK HIGH PRESSURE RIDGE CONTINUES TO SLIDE ACROSS THE CWA TODAY
AND THEN A WEAK COLD FRONT MOVES THROUGH TONIGHT.

THE WEAK HIGH PRESSURE RIDGE IS ASSOCIATED WITH AN UPPER RIDGE THAT
IS CURRENTLY PUSHING INTO WESTERN UPPER MICHIGAN THIS MORNING AND IS
EXPECTED TO QUICKLY SLIDE SOUTHEAST AND DISSIPATE AS A SHORTWAVE
DIVES SOUTHEAST FROM LAKE WINNIPEG TONIGHT. AT THE PRESENT
TIME...PLENTY OF LAKE EFFECT CLOUDS OVER CENTRAL AND EASTERN LAKE
SUPERIOR...AS RAP ANALYZED H925 TEMPS ARE AROUND -10C AND THERE IS
PLENTY OF MOISTURE TRAPPED UNDER THE SUBSIDENCE INVERSION. RADAR
NOT REALLY PICKING UP ON MUCH SNOW...DUE TO THE INVERSION BEING
AT/AROUND 3.5KFT...BUT THERE HAS BEEN LIGHT SNOW/FLURRIES AT THE
OFFICE EARLY THIS MORNING. FARTHER WEST...THE DRIER AIR SEEN ON THE
00Z KINL SOUNDING HAS CONTINUED TO EAT AWAY AT THE LAKE EFFECT OVER
THE WESTERN LAKE AND ALL THAT REMAINS OVER THE THIRD OF WESTERN
UPPER MICHIGAN IS STRATUS TRAPPED BELOW THE INVERSION. RAP/NAM H925
MOISTURE FIELDS SEEM TO HAVE A GOOD HANDLE ON THE BACK EDGE OF THIS
MOISTURE AND WILL FOLLOW THE IDEA OF THE CLOUD EDGE GRADUALLY
PUSHING TO THE NORTHEAST THROUGH THE DAY TODAY AS THE H925 RIDGE
BACKS WINDS TO THE WEST-SOUTHWEST. SINCE UPSTREAM MID/HIGH CLOUDS
WILL LIKELY AFFECT THE AREAS WHERE THE LOW CLOUDS DEPART...WON/T GO
WITH A SUNNY FORECAST AND KEEP IN MOSTLY SUNNY TO PARTLY CLOUDY
AREA.

AS FOR THE LAKE EFFECT CLOUDS AND --SHSN...MODELS NOT REALLY SHOWING
THE H925 RIDGE HAVING TOO MUCH AFFECT ON IT UNTIL THIS
AFTERNOON...EXCEPT OVER NORTH CENTRAL UPPER MICHIGAN. THE DRIER
AIR SHOULD CAUSE THE SUBSIDENCE INVERSION TO LOWER FURTHER AND
TOWARDS 2-2.5KFT OVER EASTERN LAKE SUPERIOR AND UPPER MICHIGAN.
THUS...LIKED THE PREVIOUS SHIFTS HANDLING OF PUSHING THE ISOLATED
SNOW SHOWERS EAST THROUGH THE DAY AND MAINLY FOCUSED EAST OF GRAND
MARAIS THIS AFTERNOON.

TONIGHT...FRONT ARRIVES SHORTLY AFTER SUNSET OVER THE WEST AND H925
MOISTURE SURGES BACK OVER THE AREA AND INCREASES CLOUDS. OVER THE
EAST...THERE COULD BE A BRIEF PERIOD WHERE THE SNOW COMPLETELY
ENDS LATE THIS AFTERNOON OR EARLY EVENING BEFORE THE NEXT WAVE
ARRIVES. THIS FRONT WILL DROP SOUTHEAST ACROSS THE REST OF THE CWA
DURING THE EVENING AND THE FIRST PART OF THE OVERNIGHT HOURS. WITH
WINDS VEERING TO THE NORTHWEST BEHIND THE FRONT AND COLDER AIR
SURGING BACK IN...ENHANCED BY SURFACE LOW DEVELOPING OVER
THE EASTERN LAKE...EXPECT THE LAKE EFFECT CLOUDS AND POTENTIAL SNOW
SHOWERS TO REDEVELOP LATE IN THE EVENING AND CONTINUE OVERNIGHT FOR
THE NORTHWEST TO NORTH-NORTHWEST FAVORED LOCATIONS. BEST LOW LEVEL
LAPSE RATES ARE SEEN OVER EASTERN LAKE SUPERIOR /TO 8.5C/KM /.
MODELS SHOWING SOME DIRECTIONAL SHEAR OVER THE EAST /NORTHWEST H850
WINDS AND NORTH WINDS BELOW H900/...WHICH COMBINED WITH THE FAIRLY
DRY SUB CLOUD LAYER WILL KEEP THE LAKE EFFECT FROM BECOMING
TOO STRONG /LIMITS CLOUD DEPTH TO A FEW KFT EVEN THOUGH INVERSION
HEIGHT IS NEAR 6KFT/ AND COULD ALSO INFLUENCE DEVELOPMENT. THIS IS
ESPECIALLY PREVALENT OVER THE SOUTH CENTRAL LAKE AND NORTH CENTRAL
UPPER MICHIGAN WITH THE LATEST NAM...WHILE THE GFS HAS LESS SHEAR
AND OUR LOCAL REGIONAL WRF HAS BETTER MOISTURE AND UNIDIRECTIONAL
WINDS. WITH THE DIFFERENCES...WILL CONTINUE TO MENTION A
SLIGHT/CHANCE OF SNOW SHOWERS OVER THE NORTH CENTRAL AND EAST
FAVORED LOCATIONS...WITH THE HIGHEST POPS OVER LUCE COUNTY WHERE
INCREASED CONVERGENCE WILL OCCUR WITH THE DEVELOPING SURFACE LOW.
FARTHER WEST...LAKE EFFECT CONDITIONS ARE MORE FAVORABLE IN THE
EVENING WITH BETTER LOW LEVEL MOISTURE AND INVERSION HEIGHTS TO
4.5KFT. WILL CONTINUE CHANCE POPS FOR THAT PERIOD AND THEN START TO
DIMINISH OVERNIGHT AS DRIER AIR WORKS IN. OVERALL...EXPECT MOST
LOCATIONS TO SEE LESS THAN AN INCH OF SNOW.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 451 AM EST SAT DEC 22 2012

SUNDAY AND SUNDAY NIGHT...LES CONDITIONS WILL BE LESS FAVORABLE AS
LOW-LVL FLOW BECOMES INCREASINGLY ANTICYCLONIC AND DIVERGENT AS SFC
RIDGE BUILDS INTO THE NRN PLAINS AND UPPER GREAT LAKES AREA.
INCREASING SUBSIDENCE AND INVERSION HEIGHTS LOWERING AOB 3KFT WILL
MAKE IT HARD FOR ACCUMULATING SNOW ESPECIALLY BY SUNDAY NIGHT. KEPT
IN JUST MAINLY 20-30 PCT POPS...HIGHEST EAST WHERE FETCH WILL BE
GREATER ACROSS LAKE SUPERIOR IN NW FLOW.

MON-TUE...MODELS CONTINUE TO TREND SOUTH WITH SHORTWAVE MOVING IN FM
THE NRN PLAINS LATE MONDAY INTO MON NIGHT. SOME WEAK FORCING
ASSOCIATED WITH THIS SHORTWAVE MAY PRODUCE SOME LIGHT SNOW MON INTO
MON EVENING MAINLY OVER SRN PORTIONS OF THE CWA. WITH MODELS SHOWING
850 MB TEMPS DROPPING TO -14C/-15C IN THE WAKE OF THIS
SHORTWAVE...THE ADDED INSTABILITY COULD ALSO PROVIDE A BOOST TO NNW
FLOW LES.

TUE NIGHT-THU...MODELS CONTINUE TO KEEP NEXT SYSTEM EMERGING OUT OF
SRN PLAINS/LWR MS VALLEY WELL SOUTH AND EAST OF THE GREAT LAKES
REGION WITH NO SYNOPTIC SNOW EXPECTED FOR OUR AREA. A MID-LVL TROF
AXIS FROM LOW OVER NRN CANADA IS FCST TO MOVE THROUGH THE UPPER
GREAT LAKES WED NIGHT AND THU...BUT FORCING WITH THIS FEATURE LOOKS
MINIMAL. WITH 850 MB TEMPS OF -10C/-11C CONTRIBUTING TO MARGINAL
INSTABILITY AND A WEAK NRLY FLOW...SOME LIGHT SCT LES IS POSSIBLE
DOWNWIND OF LAKE SUPERIOR OVER NRN COUNTIES. WL MAINTAIN SLIGHT CHC
POPS FOR THESE AREAS.

FRI...MODELS SHOW POTENTIAL FOR ANOTHER SIGNIFICANT MID LEVEL TROUGH
TO MOVE THROUGH THE CNTRL CONUS FOR LATE WEEK. UNCERTAINTY STILL
EXISTS WITH MODELS CONCERNING TRACK OF THIS SYSTEM. THE 00Z ECMWF
CONTINUES TO TREND WITH A MORE AMPLIFIED PATTERN THAN THE GFS...AND
WOULD INDICATE A MORE NRN TRACK WITH LEAD SHORTWAVE EMERGING OUT OF
WRN CONUS TROF. THE ECMWF SCENARIO WOULD RESULT IN A BETTER CHC OF
PCPN FOR LATE FRIDAY INTO FRIDAY NIGHT FOR OUR CWA THAN THE GFS. AT
THIS POINT...GIVEN UNCERTAINTY WILL MAINTAIN JUST SLIGHT CHC POPS
FOR LIGHT SNOW TOWARD FRI EVENING.  HOWEVER..WOULD NOT BE SURPRISED
GIVEN RECENT TRENDS...ESPECIALLY WITH THE ECMWF...THAT POPS MAY NEED
TO RAISED FOR LATE WEEK.
&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 628 AM EST SAT DEC 22 2012

LAKE EFFECT CLOUDS WILL AFFECT KCMX/KSAW THROUGH THE MORNING HOURS
BEFORE WINDS BACK TO THE WEST AND BRING DRIER AIR IN THIS
AFTERNOON. HAVE SHOWN BOTH KSAW/KCMX SCATTERING OUT THIS
AFTERNOON...BUT KSAW SEEMS MOST LIKELY TO SCATTER OUT DUE TO
WINDS ORIGINATING OFF LAND. MEANWHILE...KIWD WILL LIKELY
JUST SEE MID CLOUDS STREAMING THROUGH SINCE THEY CLEARED YESTERDAY
EVENING.

AS A COLD FRONT SWEEPS ACROSS UPPER MICHIGAN THIS EVENING...WINDS
ARE EXPECTED TO TURN TO THE NORTHWEST AND LEAD TO MVFR CEILINGS AND
LAKE EFFECT SNOW AT KCMX/KIWD. NOT OVERLY CONFIDENT ON AMOUNT OF
VISIBILITY RESTRICTIONS AND OPTED TO MENTION HIGH END MVFR AT THIS
POINT. KSAW IS A LITTLE MORE IFFY ON LAKE EFFECT SNOW WITH THE
GENERALLY NORTHWEST WINDS...SO WILL GO WITH BORDERLINE MVFR/VFR
CEILINGS.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 451 AM EST SAT DEC 22 2012

WINDS HAVE FALLEN BELOW GALES THIS MORNING AS THE PRESSURE GRADIENT
CONTINUES TO RELAX WITH WEAK HIGH PRESSURE RIDGE MOVING THROUGH
TODAY. WINDS ARE EXPECTED TO INCREASE UP TO 25KTS OUT OF THE
NORTHWEST TONIGHT AS A COLD FRONT SWEEPS SOUTHEAST ACROSS LAKE
SUPERIOR. HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL TRY
TO NOSE INTO THE UPPER GREAT LAKES FOR SUNDAY AND THE FIRST HALF OF
NEXT WEEK...KEEPING WINDS BELOW 25KTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...SRF
LONG TERM...VOSS
AVIATION...SRF
MARINE...SRF







AREA FORECAST DISCUSSION

NWS MARQUETTE MI

 453 AM EST SAT DEC 22 2012

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 451 AM EST SAT DEC 22 2012

FAIRLY QUIET WEATHER PATTERN IN STORE FOR TODAY AND TONIGHT AS A
WEAK HIGH PRESSURE RIDGE CONTINUES TO SLIDE ACROSS THE CWA TODAY
AND THEN A WEAK COLD FRONT MOVES THROUGH TONIGHT.

THE WEAK HIGH PRESSURE RIDGE IS ASSOCIATED WITH AN UPPER RIDGE THAT
IS CURRENTLY PUSHING INTO WESTERN UPPER MICHIGAN THIS MORNING AND IS
EXPECTED TO QUICKLY SLIDE SOUTHEAST AND DISSIPATE AS A SHORTWAVE
DIVES SOUTHEAST FROM LAKE WINNIPEG TONIGHT. AT THE PRESENT
TIME...PLENTY OF LAKE EFFECT CLOUDS OVER CENTRAL AND EASTERN LAKE
SUPERIOR...AS RAP ANALYZED H925 TEMPS ARE AROUND -10C AND THERE IS
PLENTY OF MOISTURE TRAPPED UNDER THE SUBSIDENCE INVERSION. RADAR
NOT REALLY PICKING UP ON MUCH SNOW...DUE TO THE INVERSION BEING
AT/AROUND 3.5KFT...BUT THERE HAS BEEN LIGHT SNOW/FLURRIES AT THE
OFFICE EARLY THIS MORNING. FARTHER WEST...THE DRIER AIR SEEN ON THE
00Z KINL SOUNDING HAS CONTINUED TO EAT AWAY AT THE LAKE EFFECT OVER
THE WESTERN LAKE AND ALL THAT REMAINS OVER THE THIRD OF WESTERN
UPPER MICHIGAN IS STRATUS TRAPPED BELOW THE INVERSION. RAP/NAM H925
MOISTURE FIELDS SEEM TO HAVE A GOOD HANDLE ON THE BACK EDGE OF THIS
MOISTURE AND WILL FOLLOW THE IDEA OF THE CLOUD EDGE GRADUALLY
PUSHING TO THE NORTHEAST THROUGH THE DAY TODAY AS THE H925 RIDGE
BACKS WINDS TO THE WEST-SOUTHWEST. SINCE UPSTREAM MID/HIGH CLOUDS
WILL LIKELY AFFECT THE AREAS WHERE THE LOW CLOUDS DEPART...WON/T GO
WITH A SUNNY FORECAST AND KEEP IN MOSTLY SUNNY TO PARTLY CLOUDY
AREA.

AS FOR THE LAKE EFFECT CLOUDS AND --SHSN...MODELS NOT REALLY SHOWING
THE H925 RIDGE HAVING TOO MUCH AFFECT ON IT UNTIL THIS
AFTERNOON...EXCEPT OVER NORTH CENTRAL UPPER MICHIGAN. THE DRIER
AIR SHOULD CAUSE THE SUBSIDENCE INVERSION TO LOWER FURTHER AND
TOWARDS 2-2.5KFT OVER EASTERN LAKE SUPERIOR AND UPPER MICHIGAN.
THUS...LIKED THE PREVIOUS SHIFTS HANDLING OF PUSHING THE ISOLATED
SNOW SHOWERS EAST THROUGH THE DAY AND MAINLY FOCUSED EAST OF GRAND
MARAIS THIS AFTERNOON.

TONIGHT...FRONT ARRIVES SHORTLY AFTER SUNSET OVER THE WEST AND H925
MOISTURE SURGES BACK OVER THE AREA AND INCREASES CLOUDS. OVER THE
EAST...THERE COULD BE A BRIEF PERIOD WHERE THE SNOW COMPLETELY
ENDS LATE THIS AFTERNOON OR EARLY EVENING BEFORE THE NEXT WAVE
ARRIVES. THIS FRONT WILL DROP SOUTHEAST ACROSS THE REST OF THE CWA
DURING THE EVENING AND THE FIRST PART OF THE OVERNIGHT HOURS. WITH
WINDS VEERING TO THE NORTHWEST BEHIND THE FRONT AND COLDER AIR
SURGING BACK IN...ENHANCED BY SURFACE LOW DEVELOPING OVER
THE EASTERN LAKE...EXPECT THE LAKE EFFECT CLOUDS AND POTENTIAL SNOW
SHOWERS TO REDEVELOP LATE IN THE EVENING AND CONTINUE OVERNIGHT FOR
THE NORTHWEST TO NORTH-NORTHWEST FAVORED LOCATIONS. BEST LOW LEVEL
LAPSE RATES ARE SEEN OVER EASTERN LAKE SUPERIOR /TO 8.5C/KM /.
MODELS SHOWING SOME DIRECTIONAL SHEAR OVER THE EAST /NORTHWEST H850
WINDS AND NORTH WINDS BELOW H900/...WHICH COMBINED WITH THE FAIRLY
DRY SUB CLOUD LAYER WILL KEEP THE LAKE EFFECT FROM BECOMING
TOO STRONG /LIMITS CLOUD DEPTH TO A FEW KFT EVEN THOUGH INVERSION
HEIGHT IS NEAR 6KFT/ AND COULD ALSO INFLUENCE DEVELOPMENT. THIS IS
ESPECIALLY PREVALENT OVER THE SOUTH CENTRAL LAKE AND NORTH CENTRAL
UPPER MICHIGAN WITH THE LATEST NAM...WHILE THE GFS HAS LESS SHEAR
AND OUR LOCAL REGIONAL WRF HAS BETTER MOISTURE AND UNIDIRECTIONAL
WINDS. WITH THE DIFFERENCES...WILL CONTINUE TO MENTION A
SLIGHT/CHANCE OF SNOW SHOWERS OVER THE NORTH CENTRAL AND EAST
FAVORED LOCATIONS...WITH THE HIGHEST POPS OVER LUCE COUNTY WHERE
INCREASED CONVERGENCE WILL OCCUR WITH THE DEVELOPING SURFACE LOW.
FARTHER WEST...LAKE EFFECT CONDITIONS ARE MORE FAVORABLE IN THE
EVENING WITH BETTER LOW LEVEL MOISTURE AND INVERSION HEIGHTS TO
4.5KFT. WILL CONTINUE CHANCE POPS FOR THAT PERIOD AND THEN START TO
DIMINISH OVERNIGHT AS DRIER AIR WORKS IN. OVERALL...EXPECT MOST
LOCATIONS TO SEE LESS THAN AN INCH OF SNOW.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 451 AM EST SAT DEC 22 2012

SUNDAY AND SUNDAY NIGHT...LES CONDITIONS WILL BE LESS FAVORABLE AS
LOW-LVL FLOW BECOMES INCREASINGLY ANTICYCLONIC AND DIVERGENT AS SFC
RIDGE BUILDS INTO THE NRN PLAINS AND UPPER GREAT LAKES AREA.
INCREASING SUBSIDENCE AND INVERSION HEIGHTS LOWERING AOB 3KFT WILL
MAKE IT HARD FOR ACCUMULATING SNOW ESPECIALLY BY SUNDAY NIGHT. KEPT
IN JUST MAINLY 20-30 PCT POPS...HIGHEST EAST WHERE FETCH WILL BE
GREATER ACROSS LAKE SUPERIOR IN NW FLOW.

MON-TUE...MODELS CONTINUE TO TREND SOUTH WITH SHORTWAVE MOVING IN FM
THE NRN PLAINS LATE MONDAY INTO MON NIGHT. SOME WEAK FORCING
ASSOCIATED WITH THIS SHORTWAVE MAY PRODUCE SOME LIGHT SNOW MON INTO
MON EVENING MAINLY OVER SRN PORTIONS OF THE CWA. WITH MODELS SHOWING
850 MB TEMPS DROPPING TO -14C/-15C IN THE WAKE OF THIS
SHORTWAVE...THE ADDED INSTABILITY COULD ALSO PROVIDE A BOOST TO NNW
FLOW LES.

TUE NIGHT-THU...MODELS CONTINUE TO KEEP NEXT SYSTEM EMERGING OUT OF
SRN PLAINS/LWR MS VALLEY WELL SOUTH AND EAST OF THE GREAT LAKES
REGION WITH NO SYNOPTIC SNOW EXPECTED FOR OUR AREA. A MID-LVL TROF
AXIS FROM LOW OVER NRN CANADA IS FCST TO MOVE THROUGH THE UPPER
GREAT LAKES WED NIGHT AND THU...BUT FORCING WITH THIS FEATURE LOOKS
MINIMAL. WITH 850 MB TEMPS OF -10C/-11C CONTRIBUTING TO MARGINAL
INSTABILITY AND A WEAK NRLY FLOW...SOME LIGHT SCT LES IS POSSIBLE
DOWNWIND OF LAKE SUPERIOR OVER NRN COUNTIES. WL MAINTAIN SLIGHT CHC
POPS FOR THESE AREAS.

FRI...MODELS SHOW POTENTIAL FOR ANOTHER SIGNIFICANT MID LEVEL TROUGH
TO MOVE THROUGH THE CNTRL CONUS FOR LATE WEEK. UNCERTAINTY STILL
EXISTS WITH MODELS CONCERNING TRACK OF THIS SYSTEM. THE 00Z ECMWF
CONTINUES TO TREND WITH A MORE AMPLIFIED PATTERN THAN THE GFS...AND
WOULD INDICATE A MORE NRN TRACK WITH LEAD SHORTWAVE EMERGING OUT OF
WRN CONUS TROF. THE ECMWF SCENARIO WOULD RESULT IN A BETTER CHC OF
PCPN FOR LATE FRIDAY INTO FRIDAY NIGHT FOR OUR CWA THAN THE GFS. AT
THIS POINT...GIVEN UNCERTAINTY WILL MAINTAIN JUST SLIGHT CHC POPS
FOR LIGHT SNOW TOWARD FRI EVENING.  HOWEVER..WOULD NOT BE SURPRISED
GIVEN RECENT TRENDS...ESPECIALLY WITH THE ECMWF...THAT POPS MAY NEED
TO RAISED FOR LATE WEEK.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1231 AM EST SAT DEC 22 2012

CONDITIONS WILL STAY VFR THROUGH SAT FOR IWD UNTIL THE WIND SWITCHES
TO THE NW BY EVENING BRINGING IN AN MVFR LAKE EFFECT CLOUD DECK
AGAIN. FOR CMX...WITH WESTERLY FLOW...MVFR LAKE EFFECT CLOUDS WILL
STAY THROUGH THE WHOLE PERIOD. FOR SAW...UNTIL THE WIND BECOMES
WESTERLY...MVFR LAKE EFFECT CLOUDS WILL STAY. WEST WINDS ON SAT
SHOULD ALLOW THE LOW CLOUDS TO MOVE OUT OF SAW BY AFTERNOON AND VFR
CONDITIONS WILL THEN PREVAIL UNTIL THE END OF THE TAF PERIOD.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 451 AM EST SAT DEC 22 2012

WINDS HAVE FALLEN BELOW GALES THIS MORNING AS THE PRESSURE GRADIENT
CONTINUES TO RELAX WITH WEAK HIGH PRESSURE RIDGE MOVING THROUGH
TODAY. WINDS ARE EXPECTED TO INCREASE UP TO 25KTS OUT OF THE
NORTHWEST TONIGHT AS A COLD FRONT SWEEPS SOUTHEAST ACROSS LAKE
SUPERIOR. HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL TRY
TO NOSE INTO THE UPPER GREAT LAKES FOR SUNDAY AND THE FIRST HALF OF
NEXT WEEK...KEEPING WINDS BELOW 25KTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...SRF
LONG TERM...VOSS
AVIATION...07
MARINE...SRF







AREA FORECAST DISCUSSION

NWS TWIN CITIES/CHANHASSEN MN

 200 PM CST SAT DEC 22 2012

.DISCUSSION...

CDFNT NOW JUST W OF MSP AND CONTG TO PUSH EAST WITH NICE AREA OF SFC
PRESSURE RISES ACROSS THE DKTS INTO W MN. NOT MUCH CLOUD COVER IN
WAKE OF FNT WITH MAIN AREA OF CLDS AND --SN PUSHING ESE ACROSS N MN
WITH WEAK UPPER AIR DISTURBANCE NOW PUSHING ACRS NW MN.

EXPANSIVE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA OUT OF
CANADA KEEPING KEEPING TEMPS COOL THRU THE WEEK.  A PIECE OF ENERGY
FROM STRONG NW COAST TROUGH WILL PUSH ACROSS THE NORTHERN ROCKIES
TONIGHT AND THEN ACRS OUR AREA SUNDAY NIGHT/MONDAY.  LOOKING PRETTY
GUD FOR A PERIOD OF -SN WITH FAIRLY STRONG UPPER TROF MOVING THRU
AREA...BUT MOISTURE PRETTY LIMITED.  UPPED POPS A BIT FOR UP TO AN
INCH OF SNOW.  BEST CHC FOR ANY ACCUM SEEMS TO BE ACRS N CWA NEAR
PATH OF MID LEVEL LOW.

ECMWF IN PARTICULAR REMAINS AGGRESSIVE ON POSSIBLE SNOW EVENT FOR
LATE FRIDAY INTO SATURDAY BRINGING MORE OF A SW WAVE INTO AREA AND
ASSOCIATED DEEP SURFACE LOW PRESSURE.  MAINTAINED POPS IN THE MID
CHC RANGE AS IN PREVIOUS PACKAGE.

&&

.AVIATION.../18Z TAF ISSUANCE/

RATHER DIFFUSE COLD FRONT IN THE PROCESS OF WORKING THROUGH
STC AND MSP RIGHT NOW. BIGGEST ISSUE ASSOCIATED WITH THIS
BOUNDARY IS WHAT HAPPENS WITH POST FRONTAL STRATUS NOW WORKING
SOUTH ACROSS NRN NODAK/MN. FOLLOWED THE RAP 925-850 RH FOR MOVING
THESE CLOUDS ACROSS THE TERMINALS. FOLLOWING THIS IDEA...EXPECT
THESE CLOUDS TO THIN ALONG THE 925-850 RIDGE AXIS GOING INTO ERN
MN/WRN WI...WITH MOST SIGNIFICANT SWATH OF LOW CLOUDS RIDING SOUTH
THROUGH THE DAKOTAS. CURRENT LAMP GUIDANCE FOLLOWS THIS RAP IDEA
WITH FIRST BATCH OF CIGS COMING IN BETWEEN 00Z AND 06Z. SECOND
ROUND OF MVFR CIGS INDICATED BY THE GFSLAMP SUNDAY MORNING IS A
BIT HARDER TO BELIEVE AT THIS POINT LOOKING AT HOW DRY SOUNDINGS
ARE. THINK THIS SECOND BATCH MAY BE A RESULT OF CLIMATOLOGY
WORKING INTO THE GUIDANCE...AS WIND BECOME NE SUNDAY MORNING.
GIVEN THE SOURCE REGION FOR THOSE NORTHEAST WINDS IS A DRY ARCTIC
HIGH OVER CANADA...ANY CLOUDS ASSOCIATED WITH IT WILL BE
ORIGINATING FROM LAKE SUPERIOR. LOOKING AT NAM RH AROUND 925
MB...ONLY EAU WILL HAVE A SHOT AT SEEING THOSE CLOUDS...WITH
EVERYONE ELSE EXPECTED TO BE SAFELY VFR.

KMSP...BEST SHOT AT SEEING MVFR CIGS WOULD BE 3-8Z WHEN A SCT MVFR
LAYER IS MENTIONED. THE LAST FEW RUNS OF THE GFSLAMP HAVE BEEN
BRINGING SOME MVFR CIGS IN DURING THIS TIMEFRAME. HOWEVER...WITH
ONLY A NARROW STRIP OF HIGHER RH NOTED AT 925 SWINGING THROUGH
DURING THIS TIME ON THE RAP...CONFIDENCE IN THEM OCCURRING STILL TOO
LOW TO BRING IN A CIG. AT THIS TIME...IT LOOKS LIKE A TEMPO MVFR
CIG IN THIS PERIOD WOULD PROBABLY COVER THINGS. AS FOR THE RETURN
TO MVFR CIGS SUNDAY MORNING IN THE GFSLAMP...THIS HAS LITTLE MERIT
WHEN LOOKING AT LOW LEVEL RH FROM THE GFS/NAM OR PROBS FOR MVFR
CIGS OFF THE SREF...SO HAVE THINGS VFR SUNDAY.

/OUTLOOK FOR KMSP/
MON...MVFR CIGS/VSBYS IN -SN POSSIBLE EARLY...THEN VFR.
      WINDS N 6 TO 8 KTS.
TUE...VFR. NW 6 TO 8 KTS.
WED...VFR. WINDS NW 5 KTS.

&&

MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.

$$

BAP/MPG









AREA FORECAST DISCUSSION

NWS TWIN CITIES/CHANHASSEN MN

 1134 AM CST SAT DEC 22 2012

.UPDATE...

18Z AVIATION DISCUSSION ADDED BELOW.

&&

.PREV DISCUSSION...
/ISSUED 602 AM CST SAT DEC 22 2012/

MAIN HIGHLIGHTS OF THIS FORECAST PACKAGE INCLUDE A CHANCE OF LIGHT
SNOW MONDAY...BELOW NORMAL TEMPERATURES FOR MOST OF THE NEXT WEEK
/MAINLY NEXT WEEK...MONDAY THROUGH WEDNESDAY ESPECIALLY/...AND A
CHANCE OF SNOW FOR NEXT WEEKEND.

EARLY THIS MORNING TEMPERATURES WERE ACTUALLY BEGINNING TO
INCREASE ACROSS THE WESTERN HALF OF THE CWA. SURFACE RIDGE AXIS
HAS MOVED INTO WESTERN WISCONSIN...SO WINDS WERE INCREASING TO
WEST OF THAT AREA. ONGOING LOW LEVEL WARM AIR ADVECTION /925 AND
850MB/ COUPLED WITH INCREASING SSE WIND SPEEDS HAS HELPED
TEMPERATURES BEGIN TO RISE SEVERAL HOURS BEFORE DAYBREAK. A WEAK
SURFACE LOW WILL DROP SOUTH FROM ONTARIO ACROSS THE UPPER GREAT
LAKES TODAY...AND WILL DRAG A COLD FRONT THROUGH THE CWA BY THIS
EVENING. NO PRECIPITATION IS EXPECTED WITH THIS BOUNDARY DUE TO
VERY DRY AIR AND LACK OF LIFT. AFTER THIS WEAK FRONT MOVES
THROUGH...DAILY HIGH TEMPERATURES WILL GET COLDER FROM DAY TO
DAY...THROUGH THE MIDDLE OF NEXT WEEK...MEANING TODAY WILL QUITE
POSSIBLY BE THE WARMEST OF THE NEXT 7 DAYS. SUNDAY WILL REMAIN DRY
AND SLIGHTLY COOLER THAN TODAY.

THE NEXT SHOT AT MEASURABLE PRECIPITATION IS ON MONDAY...AS AN
UPPER LEVEL SHORTWAVE TROUGH MOVES OVER THE AREA. MODEL
DISAGREEMENT ON TIMING AND PLACEMENT OF ANY PRECIPITATION IS
EVIDENT BETWEEN THE GFS...ECMWF...AND NAM. THE GEM LOOKS MORE IN
LINE WITH THE GFS...AND ULTIMATELY LEANED IN THE DIRECTION OF THE
GFS/GEM AS FAR AS PLACEMENT OF QPF...BUT SLOWED TIMING DOWN A FEW
HOURS AS THE NAM AND ECMWF INDICATED. THERE IS GOOD AGREEMENT
AMONG THE VARIOUS MODELS THAT TEND TO LIMIT QPF AS THE WAVE MOVES
ACROSS THE EASTERN HALF OF THE FA. IT LOOKS LIKE THE REASON FOR
THIS IS DUE TO THE FORCING SIMPLY OUTRUNNING THE SATURATED
AIR...ESPECIALLY MONDAY AFTERNOON. FOR NOW...INDICATED SLIGHT
CHANCE AND CHANCE POPS ACROSS PORTIONS OF THE CWA. WOULD LIKE TO
SEE SATURATION AND AND FORCING LINE UP IN FUTURE MODEL
RUNS...WHICH WOULD GIVE HIGHER CONFIDENCE IN SEEING MEASURABLE
PRECIPITATION. DUE TO THIS...AND THE CURRENT MODEL
DISAGREEMENT...CONFIDENCE IN THE FORECAST FOR MONDAY IS BELOW NORMAL.

CHRISTMAS DAY THROUGH THURSDAY...MID NEXT WEEK LOOKS COLD BEHIND THE
WAVE THAT MOVES THROUGH ON MONDAY. HIGH PRESSURE WILL OOZE
SOUTHWARD FROM CANADA AND PROVIDE THE REGION WITH COLD AND CLEAR
CONDITIONS FOR A FEW DAYS. CHRISTMAS DAY IS FORECAST TO BE THE
COLDEST DAY OF THE FORECAST PERIOD...ESPECIALLY ACROSS THE WEST
WHERE HIGH TEMPERATURES WILL STRUGGLE TO GET ABOVE ZERO. HIGHS IN
THE LOWER TEENS WILL BE SEEN ACROSS THE EAST.

FRIDAY...A POTENT UPPER WAVE WILL MOVE OVER THE INTER MOUNTAIN
WEST...AND SURFACE CYCLOGENESIS WILL ENSUE ON THE LEE OF THE ROCKY
MOUNTAINS. THIS LOW WILL EJECT FROM THE COLORADO/NEW MEXICO REGION
AND CURL ENE WITH THROUGH THE MIDWEST AND PROVIDES THE FA WITH THE
BEST CHANCE OF ACCUMULATING SNOWFALL OVER THE FORECAST PERIOD.
SOUTHERLY SURFACE WINDS AHEAD OF THIS SYSTEM WILL HELP WARM
TEMPERATURES TO NEAR SEASONABLE NORMALS BY THE END OF THE WEEK.

&&

.AVIATION.../18Z TAF ISSUANCE/

RATHER DIFFUSE COLD FRONT IN THE PROCESS OF WORKING THROUGH
STC AND MSP RIGHT NOW. BIGGEST ISSUE ASSOCIATED WITH THIS
BOUNDARY IS WHAT HAPPENS WITH POST FRONTAL STRATUS NOW WORKING
SOUTH ACROSS NRN NODAK/MN. FOLLOWED THE RAP 925-850 RH FOR MOVING
THESE CLOUDS ACROSS THE TERMINALS. FOLLOWING THIS IDEA...EXPECT
THESE CLOUDS TO THIN ALONG THE 925-850 RIDGE AXIS GOING INTO ERN
MN/WRN WI...WITH MOST SIGNIFICANT SWATH OF LOW CLOUDS RIDING SOUTH
THROUGH THE DAKOTAS. CURRENT LAMP GUIDANCE FOLLOWS THIS RAP IDEA
WITH FIRST BATCH OF CIGS COMING IN BETWEEN 00Z AND 06Z. SECOND
ROUND OF MVFR CIGS INDICATED BY THE GFSLAMP SUNDAY MORNING IS A
BIT HARDER TO BELIEVE AT THIS POINT LOOKING AT HOW DRY SOUNDINGS
ARE. THINK THIS SECOND BATCH MAY BE A RESULT OF CLIMATOLOGY
WORKING INTO THE GUIDANCE...AS WIND BECOME NE SUNDAY MORNING.
GIVEN THE SOURCE REGION FOR THOSE NORTHEAST WINDS IS A DRY ARCTIC
HIGH OVER CANADA...ANY CLOUDS ASSOCIATED WITH IT WILL BE
ORIGINATING FROM LAKE SUPERIOR. LOOKING AT NAM RH AROUND 925
MB...ONLY EAU WILL HAVE A SHOT AT SEEING THOSE CLOUDS...WITH
EVERYONE ELSE EXPECTED TO BE SAFELY VFR.

KMSP...BEST SHOT AT SEEING MVFR CIGS WOULD BE 3-8Z WHEN A SCT MVFR
LAYER IS MENTIONED. THE LAST FEW RUNS OF THE GFSLAMP HAVE BEEN
BRINGING SOME MVFR CIGS IN DURING THIS TIMEFRAME. HOWEVER...WITH
ONLY A NARROW STRIP OF HIGHER RH NOTED AT 925 SWINGING THROUGH
DURING THIS TIME ON THE RAP...CONFIDENCE IN THEM OCCURRING STILL TOO
LOW TO BRING IN A CIG. AT THIS TIME...IT LOOKS LIKE A TEMPO MVFR
CIG IN THIS PERIOD WOULD PROBABLY COVER THINGS. AS FOR THE RETURN
TO MVFR CIGS SUNDAY MORNING IN THE GFSLAMP...THIS HAS LITTLE MERIT
WHEN LOOKING AT LOW LEVEL RH FROM THE GFS/NAM OR PROBS FOR MVFR
CIGS OFF THE SREF...SO HAVE THINGS VFR SUNDAY.

/OUTLOOK FOR KMSP/
MON...MVFR CIGS/VSBYS IN -SN POSSIBLE EARLY...THEN VFR.
      WINDS N 6 TO 8 KTS.
TUE...VFR. NW 6 TO 8 KTS.
WED...VFR. WINDS NW 5 KTS.

&&

MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.

$$

SPD/MPG






AREA FORECAST DISCUSSION

NWS OMAHA/VALLEY NE

 341 PM CST SAT DEC 22 2012

.SHORT TERM...TONIGHT THROUGH CHRISTMAS DAY.

THE FORECAST CONCERNS IN THE SHORT TERM WILL BE THE CLOUDS...POTENTIAL
FOR FLURRIES OR LIGHT SNOW WITH A NORTHERN STREAM WAVE SUNDAY
NIGHT AND THE SOUTHERN STREAM WAVE CHRISTMAS EVE AND CHRISTMAS
DAY...AND TEMPERATURES.

SUNSHINE AND WARM H85 TEMPERATURES HAVE TRANSLATED INTO READINGS IN
THE 30S AND A FEW 40S FOR MUCH OF THE FORECAST AREA.  THE SURFACE
WINDSHIFT TO THE NORTHWEST HAD MADE TO THE VALLEY NWS BY 130PM AND
COOLING IN TEMPERATURES WERE NOTICED FROM YANKTON TO ONEILL.

THE STORM SYSTEM OF INTEREST FOR OUR WEATHER LATER THIS WEEKEND AND
EARLY NEXT WEEK IS JUST STARTING TO BECOME SAMPLED BY THE WEST COAST
STATIONS IN THE 12Z RUNS.  AT THIS POINT...THERE IS GOOD AGREEMENT
IN THE SHORT RANGE MODELS THAT LEAD ENERGY FROM THIS SYSTEM WILL
MOVES ACROSS THE NORTHERN ROCKIES...INTO THE PLAINS TONIGHT AND
SUNDAY...FLATTENING THE MID LEVEL RIDGE AND ALLOWING VERY COLD AIR
FROM CANADA TO MOVE SOUTHWARD ACROSS THE DAKOTAS...MINNESOTA...AND
IOWA...WITH SOMEWHAT OF A GLANCING BLOW LOCALLY.  AT THIS
TIME...THERE IS AN AREA OF STRATUS AND FLURRIES ACROSS NORTHERN
NORTH DAKOTA.  A LOOK AT THE 18Z STLT AND THE 18Z PROJECTIONS FOR
NAM/GFS AND MOST RECENT HRRR SEEM TO BE OVERDOING THE LOW LEVEL RH.
THE 12Z EC SEEMS TO HAVE A BETTER HANDLE ON THE LOW LEVEL RH.

THE WATER VAPOR SATELLITE IMAGERY AND A LOOK AT WINDS ALOFT AND
HEIGHTS SHOW ONE JET SEGMENT WEST OF THE TROF OFF THE WEST COAST AND
ANOTHER JET SEGMENT OVER THE SOUTHWEST U.S. WITH MOISTURE FROM THE
TROPICS STREAMING INTO THE SOUTHERN ROCKIES AND SOUTHERN PLAINS.
HIGH LEVEL CLOUDS WILL BE ON THE INCREASE DURING THE OVERNIGHT HOURS
AND CONTINUE INTO SUNDAY.  STRATUS DEVELOPMENT IS LESS CERTAIN...AND
FOR NOW THE BEST CHANCE FOR STRATUS APPEARS TO BE INTO NORTH CENTRAL
NEBRASKA OVERNIGHT WITH SOME STRATUS DEVELOPING OVER PARTS OF THE
FORECAST AREA SUNDAY. THERE IS GOOD MID LEVEL WARM AIR ADVECTION
WELL TO THE NORTH OF THE AREA AND THERE COULD BE SOME FLURRIES IN
THE FAR NORTH/NORTHEAST TOWARD MACY AND MAPLETON WITH THE CLOUDS AND
ALSO AS THE SHORTWAVE IS TRACKING FROM THE DAKOTAS INTO IOWA.
TONIGHT...SURFACE HIGH PRESSURE WILL BUILD IN AND HAVE LOWS IN THE
SINGLE DIGITS AND TEENS.  HIGHS SUNDAY SHOULD BE COLDER...ONLY IN
THE TEENS AND 20S.  THE SHORTWAVE TROF SUNDAY NIGHT BRINGS A
WINDSHIFT THRU AND MUCH COLDER TEMPERATURES.  HIGHS MONDAY SHOULD
MAINLY BE IN THE TEENS.

THE NEXT STRONGER...LARGER STORM SYSTEM JUST MOVING ONTO THE WEST
COAST IS FORECAST TO TRACK ACROSS THE ROCKIES INTO THE PLAINS
CHRISTMAS EVE AND CHRISTMAS DAY.  THE SURFACE LOW TRACKS WELL TO THE
SOUTH OVER TEXAS...AND THE BETTER LIFT IS ALSO WELL TO THE SOUTH.
THERE IS SOME BROAD MID AND UPPER LEVEL LIFT AND WITH THE COLD
AIRMASS IS IN PLACE THERE MAY BE SOME FLURRIES OR LIGHT SNOW. FOR
NOW HAVE SOME CHANCE PROB OF PRECIPITATION TOWARD
ALBION...COLUMBUS...AND SEWARD...WITH SLIGHT CHANCE FOR LIGHT SNOW
AND CHANCE OF FLURRIES MENTIONED ACROSS PARTS OF . HIGHS MONDAY
AND TUESDAY LOOK TO HOLD IN THE TEENS.

ZAPOTOCNY

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY.

NEW MEDIUM RANGE MODELS INDICATING GOING FCST IS IN GOOD
SHAPE...THUS ONLY MINOR ADJUSTMENT MADE. LARGE SCALE FLOW IS
ADVERISED TO BE RATHER PROGRESSIVE THRU THE EXTENDED PDS.

MODELS PROG A LONGWAVE TROF EXITING EWD OF THE REGION TUESDAY NIGHT
WITH ITS AXIS PRETTY MUCH CUTTING DOWN THE MS VLY. MEANWHILE...
UPSTREAM SHORTWAVE TROF OFF THE PAC NW COAST WILL BE THE NEXT SYSTEM
OF INTEREST FOR POSSIBLE ACTIVE WX. THE ECM CONTINUES TO BE THE MOST
ROBUST PUSHING THE SYSTEM ACROSS CA INTO THE INTERMOUNTAIN WEST WED
NIGHT/THURS MORNING WITH 500 MB HGT FALLS AROUND 160M AND INCREASING
DPVA INDUCING SFC CYCLOGENESIS NEAR THE OK PANHANDLE. SYNOPTIC LIFT
INCREASES INTO THURSDAY NIGHT AS NARROW CHANNEL OF VORTICIY ROUNDS
THE BASE OF THE TROF. THIS IN COMBINATION WITH A RELATIVELY WEAK
LOW/MID LYR FRONTOGENETIC CIRCULATION AND MODEST 280K ISENTROPIC
UPGLIDE...THE ECM FOCUSES PCPN INITIATION FROM ABOUT SWRN SD TO NERN
CO THEN PUSHES IT EWD THRU THE DAY ON FRIDAY. AM INCLINED AT THIS
POINT TO FAVOR ECM SOLUTION OVER THE GFS. THEREFORE WILL MAINTAIN
SMALL SNOW POPS THURSDAY NIGHT AND FRIDAY. FRIDAY EVENING...ANY SNOW
ACTIVITY SHOULD BE COMING TO A QUICK END AS CAA/SUBSIDENCE
SUPPRESSES ANY DYNAMIC FORCING. OTHERWISE...BOTH ECM MOS AND MEX
ADVERTISING WELL BELOW NORMAL TEMPS DAYS 4-7.

DEE
&&

.AVIATION...
18Z TAFS FOR KOFK...KOMA AND KLNK. VFR CONDITIONS

VFR CONDITIONS WILL CONTINUE UNTIL THIS EVENING AFTER A COLD FRONT
MOVES ACROSS THE AREA. MVFR TO IFR CEILINGS ARE EXPECTED AFTER
09-10Z ACROSS THE AREA WITH STRATUS AND FOG OCCUR BEHIND THE
FRONT.

SMITH

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$




AREA FORECAST DISCUSSION

NWS WILMINGTON OH

 841 PM EST SUN DEC 23 2012

.SYNOPSIS...
WEAK LOW PRESSURE TRAVELING THROUGH KENTUCKY AND SOUTHEAST OHIO
WILL BRING AN AREA OF PRECIPITATION LATE TONIGHT THROUGH MONDAY.
WEAK HIGH PRESSURE WILL RESULT IN DRY WEATHER ON CHRISTMAS DAY. A
VIGOROUS LOW PRESSURE SYSTEM IS EXPECTED TO DUMP A WINTRY MIX OF
PRECIPITATION OVER THE REGION ON WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
LOW PRESSURE OVER NW ARKANSAS WILL MOVE NORTHEAST TO WESTERN
KENTUCKY BY MORNING. LATEST NAM...RAP AND HRRR INDICATE THAT THE
BEST WARM...MOIST ASCENT/ISENTROPIC LIFT WILL OCCUR ALONG AND
SOUTH OF THE OHIO RIVER LATE. THIS MOIST FLOW WILL CAUSE LOW LEVEL
CLOUDS TO INCREASE FROM SOUTH TO NORTH OVERNIGHT WITH CLOUDY SKIES
EXPECTED ALONG AND SOUTH OF THE OHIO RIVER BY MORNING. THERE HAS
BEEN A CONCERN ON HOW FAST PRECIPITATION WILL MOVE INTO OUR AREA
VERSUS SURFACE TEMPERATURES BEING AT OR BELOW FREEZING BY THE TIME
IT ARRIVES. IT NOW APPEARS THAT PRECIPITATION SHOULD PRETTY MUCH
ARRIVE FROM SOUTH TO NORTH AS TEMPERATURES AND DEWPOINTS
RISE...AND NOT MUCH IN THE WAY OF FREEZING RAIN IS EXPECTED. HAVE
SHOWN THIS IN THE LATEST GRIDS AND ZONES WHICH IS TO KEEP A DRY
FORECAST PRETTY MUCH ACRS THE WHITEWATER/MIAMI VALLEYS...WEST
CENTRAL OHIO AND CENTRAL OHIO OVERNIGHT. LOWS WILL OCCUR THIS
EVENING AND EARLY MORNING...THEN THEY SHOULD RISE AS CLOUDS
THICKEN AND THE WIND INCREASES SOME FROM THE EAST AHEAD OF THE
SURFACE LOW.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
WITH THE WEAK LOW MOVING TO EASTERN OHIO...RAIN WILL BE LIKELY
MONDAY IN SOUTHERN AND EASTERN COUNTIES...WITH A GOOD CHANCE OF
RAIN IN THE NORTH AND WEST. THE WINDOW OF OPPORTUNITY FOR FREEZING
PRECIPITATION SEEMS MINIMAL MONDAY MORNING ALONG AND NORTH OF I-70 AS
TEMPERATURES AND DEWPOINTS RISE AS THE PRECIPITATION ARRIVES.
THERE COULD BE A BRIEF PERIOD OF FREEZING RAIN AT THE ONSET BUT IT
SHOULD NOT LAST VERY LONG AND SHOULD HAVE LITTLE IF ANY IMPACT.
A RISE INTO THE 40S IS FORECAST FOR MOST LOCATIONS MONDAY
AFTERNOON.

RAIN WILL BE ENDING MONDAY EVENING WITH THE LOW EXITING TO THE
EAST. A FEW SNOW SHOWERS MAY OCCUR NORTH OF DAYTON BEFORE
PRECIPITATION CHANCES END AROUND MIDNIGHT TUESDAY. AFTER WEAK HIGH
PRESSURE ARRIVES FOR A SHORT STAY...CLOUDS WILL INCREASE AGAIN ON
TUESDAY AHEAD OF THE STRONG LOW. HIGHS AROUND 40 ARE EXPECTED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
FOCUS IS ON THE WINTER STORM WHICH WILL AFFECT THE REGION AT MID
WEEK. VIGOROUS MID LEVEL S/W TO LIFT FROM THE SRN PLAINS INTO THE
LOWER OH VLY TUESDAY NIGHT AND ACRS THE REGION WEDNESDAY. NUMERICAL
MODEL SOLNS CONTINUE TO SHOW SPREAD REGARDING THE EXACT TRACK OF THE
ASSOCIATED SFC WAVE WHICH LIFTS NE THRU THE REGION ON WEDNESDAY. IN
GENERAL THE GFS DETERMINISTIC SOLNS HAVE BEEN THE FURTHEST WEST AND
THEREFORE BRING MORE WARM AIR INTO ILN/S FA. THE ECMWF SOLN HAS BEEN
MORE CONSISTENT WITH THE LATEST 12Z DETERMINISTIC RUN TRENDING A
LITTLE WEST AND THEREFORE ALLOWING A LTL MORE INTRUSION OF WARM AIR.
GFS ENSEMBLE MEAN SOLN IS PLACED A LTL EAST OF ITS DETERMINISTIC
RUN.

HAVE TRENDED THE LATEST FCST TOWARD THE A SLIGHTLY MODIFIED (WARMER)
SOLN THAN 12Z ECMWF RUN GIVEN TRENDS AND CONSISTENCY.

HAVE SPREAD LKLY POPS IN FROM THE SOUTH TUESDAY NIGHT AND THEN
BUMPED UP POPS TO CATEGORICAL EARLY WEDNESDAY.

USING AT TOP DOWN TECHNIQUE APPLIED TO MODIFIED ECMWF SOLN HAVE FAR
WEST CENTRAL OHIO (NORTHWEST OF DAYTON) STAYING ALL SNOW BUT HAVE A
MIX SPREADING INTO THE REMAINDER OF ILN/S FA AND RAIN SE OF I-71
DURING THE DAY ON WED. AS COLDER AIR WRAPS INTO THE SYSTEM...HAVE
ALL PRECIP CHANGE BACK TO SNOW WEDNESDAY NIGHT. THIS SYSTEM HAS THE
POTENTIAL TO PRODUCE 6 INCHES OR MORE OF SNOW AND SIGNIFICANT ICE.
AT THIS TIME IT LOOKS LIKE A STORM TOTAL 4 TO 6 INCH SNOW BAND IS
PSBL FROM EAST CENTRAL INDIANA THRU FAR W CNTRL OHIO. THERE WILL
LKLY BE A SHARP CUT OFF TO THE SE WITH 1 TO 2 INCHES ALONG AND JUST
WEST OF I-71 AND LESS THAN AN INCH SE OF I-71.

GIVEN THE HIGH DEGREE OF UNCERTAINTY REGARDING THE EXACT TRACK...
WILL CONTINUE TO HIGHLIGHT THIS THREAT IN THE HWO PRODUCT.

AS THIS WINTER STORM LIFTS NE WILL TAPER OFF SNOW EARLY ON THURSDAY.
UPPER LEVEL RIDGING AND SFC RIDGING TO BUILD IN PROVIDING DRY WX
CONDITIONS LATER THURSDAY AND FRIDAY.

MODEL SOLN DIFFERENCES REGARDING THE WEATHER SYSTEM NEXT WEEKEND.
PREV GFS WAS KEEPING PCPN TO OUR SOUTH BUT LATEST RUN BRINGS IN
PRECIP BUT IS WEAKER AND ALLOWS FOR LESS WARM AIR. ECMWF SOLNS HAVE
BEEN STRONGER AND ALLOW FOR MORE INITIAL WARM AIR INTRUSION. HAVE
SPREAD CHC POPS IN FRIDAY NIGHT AND THEN CONT HIGH CHC POPS ON
SATURDAY. HAVE ALLOWED FOR A MIX OF RAIN AND SNOW OVER THE SE HALF
AND KEPT ALL SNOW NW. SOME LINGERING SNOW SHOWERS WILL BE PSBL ON
SUNDAY WITH THE BEST CHC ACRS THE NORTH.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
WITH THE LOW PRESSURE SYSTEM OVER EASTERN OK TO TRACK QUICKLY
NORTH OVERNIGHT...THE ASSOCIATED WARM FRONT WILL PROGRESS TO NEAR
THE OHIO RIVER BY 12Z MONDAY. VFR WITH ONLY HIGH CLOUDS THROUGH
ABOUT 09Z OR SO IN THE SOUTH. EARLIER THOUGHTS ON A PERIOD OF FZRA FOR
KLUK/KCVG NOW NOT LOOKING LIKELY AT ALL WITH THE WARM TEMPERATURES
TODAY IN THIS AREA...ALONG WITH OVERNIGHT LOWS NOT EXPECTED TO
COINCIDE WITH PRECIPITATION ONSET. OVERNIGHT LOWS WILL BE NEAR
FREEZING PRIOR TO 06Z...AND THEN SLIGHTLY WARMING TEMPERATURES
TOWARD DAYBREAK SO THAT PRECIPITATION SHOULD BE ALL RAIN HERE.

FURTHER NORTH TOWARD KILN/KDAY...OVERNIGHT LOWS WILL FOLLOW A MORE
DIURNAL PATTERN...SO THAT THE LOWER TEMPERATURE PROFILES WILL
SUFFICIENTLY COLDER NORTH OF THE WARM FRONT TO ALLOW A 13-15Z
PERIOD OF POTENTIAL FZRA. AFTER 15Z...ALL RAIN. FOR
KCMH/KLCK...PRECIP ONSET LIKELY TO OCCUR WHEN THE TEMPERATURES
HAVE WARMED...BUT CANNOT RULE OUT A LATE MORNING BRIEF PERIOD OF
FZRA OR A MIX OF FZRA/RA.

MVFR CIGS/VSBYS AND EVEN IFR CIGS TO IMMEDIATELY PRECEDE AND
ACCOMPANY PRECIPITATION IN THE 09Z ONWARD AT THE SOUTHERN
LOCATIONS...AND THE 12-14Z AND ONWARD TIME PERIODS FOR THE
NORTHERN TAF LOCATIONS.

OUTLOOK...MVFR CEILINGS AND VSBYS POSSIBLE INTO MONDAY NIGHT. IFR
CEILINGS AND VISIBILITIES POSSIBLE WEDNESDAY...LIFTING TO MVFR
THURSDAY.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.

&&

$$
SYNOPSIS...CONIGLIO/HICKMAN
NEAR TERM...HICKMAN
SHORT TERM...CONIGLIO/HICKMAN
LONG TERM...AR
AVIATION...HICKMAN







AREA FORECAST DISCUSSION

NWS GREEN BAY WI

 527 PM CST SUN DEC 23 2012

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY

THE LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW ARCTIC HIGH
PRESSURE STRETCHING FROM NORTHERN ALBERTA TO THE WESTERN GREAT LAKES
EARLY THIS AFTERNOON.  LOW LEVEL STRATO-CU RAPIDLY DISSIPATED LATE
THIS MORNING ACROSS ALL BUT FAR NORTH-CENTRAL WISCONSIN.  MEANWHILE
UPSTREAM...A SHORTWAVE TROUGH IS MOVING EAST OVER NORTH-DAKOTA WHERE
IT IS PRODUCING 1-3SM IN LIGHT SNOW.  MID AND HIGH CLOUDS ARE
ALREADY ENTERING WESTERN WISCONSIN AHEAD OF THIS SYSTEM.  AS THE
SHORTWAVE CONTINUES TO MOVE EAST THROUGH THE REGION LATE TONIGHT AND
TOMORROW...PRECIP CHANCES ARE THE MAIN FORECAST CONCERN.

TONIGHT...HIGH PRESSURE WILL BE IN PLACE FOR THE FIRST PART OF THE
EVENING WITH ONLY LIGHT NORTHWEST FLOW CREATING LOW STRATO-CU OVER
FAR N-C WISCONSIN.  HOWEVER...MID AND HIGH CLOUDS WILL BE ON THE
INCREASE AND LOWERING THROUGH THE NIGHT AHEAD OF A SHORTWAVE TROUGH
MOVING EAST OVER THE NORTHERN PLAINS.  THIS WAVE WILL BE APPROACHING
THE NORTHERN MISSISSIPPI VALLEY LATE TONIGHT...AND WILL PUSH DECENT
MID AND UPPER FORCING INTO THE REGION.  850MB LOW AND SURFACE
INVERTED TROUGH WILL HANG BACK OVER NE IOWA AND SOUTHEAST MINNESOTA
WHERE LOW LEVEL MOISTURE ARRIVES BY 12Z MONDAY.  AS A
RESULT...PROGGED SOUNDINGS INDICATE A PROMINENT DRY WEDGE BETWEEN
925 AND 700MB THAT WILL HAVE TO SATURATE BEFORE PRECIP ARRIVES.
KEPT A SMALL CHANCE OF LIGHT SNOW OVER N-C WISCONSIN WHERE LOW
STRATO-CU COULD BECOME SEEDED BY THE LOWERING MID-DECK LATE.  BUT THINK
THE REMAINING PART OF THE CWA WILL HAVE TO WAIT UNTIL MONDAY MORNING
FOR PRECIP CHANCES.  LOWS IN THE MIDDLE SINGLE DIGITS NORTH TO THE
MID TEENS SOUTH.

MONDAY...THE SHORTWAVE TROUGH WILL MOVE ACROSS THE STATE THROUGH
ABOUT MID-AFTERNOON BEFORE DEPARTING TO THE EAST.  WILL SEE
INCREASING AMOUNTS OF LOW AND MID-LEVEL MOISTURE...AND THE DRY WEDGE
IN THE SOUNDINGS ERODES OVER THE COURSE OF THE MORNING.  DESPITE THE
850MB LOW AND INVERTED SURFACE TROUGH PASSING BY TO OUR
SOUTH...THINK WILL HAVE ENOUGH LIFT ABOVE 700MB FOR AT LEAST A
CHANCE OF LIGHT SNOW EVERYWHERE.  THE BEST CHANCES WILL REMAIN OVER
N-C WISCONSIN AND THE LAKE MICHIGAN SHORELINE DUE TO THE AID OF A
SMALL LAKE EFFECT COMPONENT.  THOUGH THE FORCING WILL EXIT THE STATE
DURING THE AFTERNOON...IT SEEMS THAT ENOUGH LOW LEVEL MOISTURE WILL
LINGER TO KEEP SKIES CLOUDY WITH SCATTERED FLURRY ACTIVITY.  WILL
SHOW A HALF INCH TO AN INCH OF ACCUMULATION OVER N-C AND FAR NE
WISCONSIN.  HIGHS MAINLY IN THE LOW TO MID 20S.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY.

WESTERN GREAT LAKES REGION LOOKS TO REMAIN ON THE NORTHERN
PERIPHERY OF RATHER ACTIVE SOUTHERN STREAM. OTHER THAN SOME
LINGERING LIGHT SNOW OR FLURRIES ACROSS THE FAR EASTERN SECTION OF
THE FORECAST AREA MONDAY EVENING WITH DEPARTING DISTURBANCE...GENERALLY
BENIGN WEATHER EXPECTED OVER THE FORECAST AREA THROUGH MOST OF THE
WORK WEEK. EXCEPTION WILL BE SOME MARGINAL LAKE EFFECT SNOW
CHANCES ALONG THE LAKE MICHIGAN SHORELINE AND THE TRADITIONAL LAKE
SUPERIOR SNOW BELT REGION. DAYTIME TEMPERATURES WILL START OUT A
FEW DEGREES BELOW NORMAL EARLY IN THE WEEK THEN GRADUALLY REBOUND
TO NEAR OR SLIGHTLY ABOVE NORMAL BY THE END OF THE WEEK.

MODELS CONTINUE TO MAINTAIN THAT AN IMPRESSIVE STORM SYSTEM WILL
TAKE SHAPE OVER THE SOUTHERN MISSISSIPPI VALLEY TUESDAY NIGHT THEN
HEAD NORTHEAST ACROSS THE OHIO VALLEY. SYSTEM WILL LIKELY GET
CLOSE ENOUGH TO BRING MID-HIGH CLOUDS INTO THE AREA LATE TUESDAY
NIGHT INTO WEDNESDAY. LIGHT STRATIFORM PRECIPITATION MAY CLIP
SOUTHEAST CORNER OF WISCONSIN...BUT SHOULD STAY SOUTH OF THE
FORECAST AREA. HOWEVER...WILL NEED TO KEEP AN EYE ON THIS SYSTEM
AS A SLIGHT JOG TO THE WEST COULD BRING A LITTLE LIGHT SNOW INTO
FAR SOUTHEAST PORTION OF THE FORECAST AREA. IN ADDITION...WEAK
NORTHERN STREAM DISTURBANCE IS ALSO FORECAST TO APPROACH THE
FORECAST AREA LATE WEDNESDAY AND POSSIBLY PHASE WITH MAIN SYSTEM
OVER LOWER MICHIGAN. THIS WEAK DISTURBANCE COULD ALSO BRING A
LITTLE LIGHT SNOW OR FLURRIES OVER EASTERN WISCONSIN LATE ON
WEDNESDAY. FINALLY...A PERIPHERAL EFFECT OF SYSTEM MOVING ACROSS
THE OHIO VALLEY WILL BE THAT A DEEP LAYER OF NORTHEAST WINDS WILL
DEVELOP AFTER 06Z WEDNESDAY AND PERSIST UNTIL ABOUT 06Z THURSDAY.
DESPITE A SOMEWHAT FAVORABLE OVERWATER FETCH...LOW-LEVEL
INSTABLITY NOT IMPRESSIVE. LOOKS LIKE THE MOST FAVORABLE WINDOW
FOR MARGINAL LES WOULD BE FROM 06Z TO 18Z WEDNESDAY. MAINTAINED
LOW CHANCE POPS ALONG THE LAKESHORE ESPECIALLY FROM KEWAUNEE
SOUTHWARD.

MEDIUM RANGE MODELS STILL HINTING AT ANOTHER SOUTHERN STREAM SYSTEM
TO EVOLVE OVER THE SOUTHERN MISSISSIPPI VALLEY FRIDAY...IN ADDITION
TO ANOTHER WEAKER PEICE OF NORTHERN STREAM ENERGY FORECAST TO
WORK ACROSS THE NORTHERN PLAINS. ALTHOUGH CONFIDENCE STILL LOW
WITH RESPECT ANY INTERACTION WITH THESE FEATURES...IT APPEARS THAT
A BROAD WAA REGIME DOWNSTREAM MAY GENERATE SOME LIGHT SNOW OVER
THE CENTRAL MISSISSIPPI VALLEY THAT COULD SPREAD INTO WISCONSIN
SOMETIME ON FRIDAY. FOR NOW...MAINTAINED CHANCE POPS FRIDAY INTO
SATURDAY.
&&

.AVIATION...THICKENING MID TO HIGH LEVEL CLOUDS BUT VFR CONDITIONS
WILL PREVAIL TONIGHT. A WEAK DISTURBANCE DROPPING OVER THE
NORTHERN GREAT LAKES REGION ON MONDAY WILL BRING LIGHT SNOW TO
MUCH OF WISCONSIN. CIGS WILL LOWER TO MVFR LEVELS AS THE MVFR TYPE
LIGHT SNOW SPREADS FROM WEST TO EAST ACROSS THE STATE.

TDH
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 505 PM CST SUN DEC 23 2012

.SHORT TERM...TONIGHT THROUGH WEDNESDAY
237 PM CST SUN DEC 23 2012

MAIN FORECAST CONCERNS REMAIN ON LIGHT PRECIPITATION CHANCES TONIGHT
THROUGH MONDAY...WITH THE POTENTIAL FOR SOME LIGHT FREEZING DRIZZLE
SOUTH OF INTERSTATE 90.

LATEST WATER VAPOR IMAGERY SHOWED A SHORTWAVE TROUGH MOVING INTO THE
WESTERN DAKOTAS MOVING EAST. A BROAD UPPER LOW WAS CENTERED OVER
JAMES BAY WITH NORTHWEST FLOW ALOFT NOTED ACROSS MUCH OF THE
WESTERN GREAT LAKES. SURFACE OBSERVATIONS SHOWED PERSISTENT
STRATUS STRETCHING ACROSS PORTIONS OF NORTHEAST IOWA THROUGH MUCH
OF SOUTHERN WISCONSIN. A FEW LAKE EFFECT CLOUDS WERE STREAMING
INTO FAR NORTHERN WISCONSIN ON NORTHERLY FLOW NEAR THE SURFACE.
SCATTED HIGH CIRRUS WILL CONTINUE FLOWING IN FROM THE WEST AHEAD
OF THE APPROACHING SHORTWAVE.

THE SHORTWAVE WILL MOVE EAST AND INTO THE UPPER MISSISSIPPI RIVER
VALLEY LATE TONIGHT. FORECAST MODELS CONTINUE TO BRING LIGHT
PRECIPITATION INTO THE AREA AND THIS HAS BEEN A CONSISTENT SIGNAL.
THERE IS A CONCERN TONIGHT REGARDING WEATHER OR NOT THERE WILL BE
ICE PRESENT ALOFT FOR THE PRODUCTION OF SNOW. FORECAST SOUNDINGS
SUGGEST THERE MAY NOT BE ICE DURING THE ONSET OF PRECIPITATION
SOUTH OF INTERSTATE 90. THIS APPEARS TO BE MORE OF AN ISSUE ALONG
AND EAST OF THE MISSISSIPPI RIVER DURING THE DAY ON MONDAY. 12Z KBLR
NAM SOUNDING SHOWS THE TOP OF THE CLOUD LAYER AROUND -8C BY 11Z
MONDAY MORNING...THEN COOLS AND DEEPENS RATHER QUICKLY DURING THE
MORNING HOURS WITH -10C AT THE TOP OF THE CLOUD BY 15Z. CANNOT RULE
OUT A PERIOD OF LIGHT FREEZING DRIZZLE ON MONDAY...WITH THE HIGHEST
CHANCES SOUTH OF INTERSTATE 90 AND MAINLY EAST OF THE MISSISSIPPI
RIVER. LOCATIONS NORTH OF INTERSTATE 90 WILL SEE LIGHT SNOW LATE
TONIGHT THROUGH MONDAY MORNING WITH ACCUMULATIONS OF UP TO 1 INCH
POSSIBLE. THE SHORTWAVE QUICKLY PUSHES INTO EASTERN WISCONSIN MONDAY
AFTERNOON BUT AN INVERTED SURFACE TROUGH LINGERS ACROSS SOUTHWEST
INTO CENTRAL WISCONSIN. THERE IS EXCELLENT AGREEMENT IN THE FORECAST
MODELS WITH THIS FEATURE REGARDING PLACEMENT...TIMING...AND
PRECIPITATION AMOUNT. DECIDED TO INCLUDE A STRIP OF LIKELY
PRECIPITATION CHANCES EXTENDING FROM CENTRAL WISCONSIN INTO FAR
SOUTHWEST WISCONSIN. WITH THE TOP OF THE CLOUD LAYER NOT REALLY
TAPPING INTO ICE WILL MAINTAIN PATCHY FREEZING DRIZZLE IN THE
FORECAST. PLAN ON MOSTLY CLOUDY SKIES ON MONDAY WITH HIGH
TEMPERATURES RANGING FROM THE LOWER 20S ACROSS NORTHERN WISCONSIN TO
THE UPPER TEENS ACROSS WESTERN SECTIONS OF NORTHEAST IOWA.

WEAK SURFACE HIGH PRESSURE WILL BUILD INTO THE UPPER MISSISSIPPI
RIVER VALLEY LATE CHRISTMAS EVE AND WILL REMAIN OVER THE REGION
THROUGH CHRISTMAS DAY. COLDER AIR IS EXPECTED TO MOVE INTO THE
REGION CHRISTMAS EVE WITH OVERNIGHT LOWS RANGING FROM THE UPPER
SINGLE DIGITS ACROSS FAR SOUTHWEST WISCONSIN TO THE THE SINGLE
DIGITS BLOW ZERO ACROSS PORTIONS OF SOUTHEAST MINNESOTA THROUGH
NORTH CENTRAL WISCONSIN. PLAN ON PARTLY SUNNY SKIES ACROSS THE AREA
ON CHRISTMAS DAY WITH HIGHS MAINLY IN THE TEENS. A FEW LOCATIONS
ACROSS CENTRAL INTO FAR SOUTHWEST WISCONSIN MAY APPROACH 20. A
POTENT UPPER TROUGH WILL MOVE ACROSS THE SOUTHERN PLAINS ON TUESDAY
AND LIFT INTO THE OHIO RIVER VALLEY REGION ON WEDNESDAY AND
EVENTUALLY INTO NEW ENGLAND WEDNESDAY NIGHT. THIS SYSTEM STILL LOOKS
TO STAY WELL EAST OF THE REGION. HIGH PRESSURE WILL REMAIN IN
CONTROL THROUGH WEDNESDAY NIGHT WITH DRY AND COOL CONDITIONS
EXPECTED. PLAN ON HIGHS ON WEDNESDAY RANGING FROM THE LOWER TEENS
ACROSS PORTIONS OF SOUTHEAST MINNESOTA TO THE LOWER 20S OVER CENTRAL
WISCONSIN

.LONG TERM...THURSDAY THROUGH SUNDAY
237 PM CST SUN DEC 23 2012

23.12 MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT THROUGH
THURSDAY. THE ECMWF AND GFS ARE LEANING TOWARD SIMILAR SOLUTIONS
FRIDAY INTO SATURDAY WITH THE EVOLUTION OF A NORTHERN AND SOUTHERN
STREAM TROUGH. THE ECMWF WAS PREVIOUSLY TRYING TO MERGE THESE TWO
FEATURES OVER THE UPPER MISSISSIPPI RIVER VALLEY...POTENTIALLY
BRINGING SIGNIFICANT SNOW ACCUMULATIONS TO THE AREA ON SATURDAY.
THE ECMWF NOW SHOWS THE SOUTHERN WAVE DRIVING MUCH FURTHER EAST.
THE LATEST ECMWF SHOWS A VIGOROUS UPPER LOW TAKING SHAPE OVER THE
OHIO RIVER VALLEY ON SATURDAY. THE GFS CONTINUES TO KEEP A SERIES
OF OPEN WAVES AS THEY PROGRESS OVER THE FORECAST AREA. THE
NORTHERN WAVE LOOKS TO MOVE ACROSS THE UPPER MISSISSIPPI RIVER
VALLEY FRIDAY INTO SATURDAY BRINGING CHANCES FOR LIGHT SNOW TO THE
AREA. MAJOR DIFFERENCES NOTED SUNDAY WITH THE ECMWF BUILDING A
RIDGE OVER THE CENTRAL CONUS AND THE GFS SHOWING COOL NORTHWEST
FLOW ALOFT OVER THE AREA. WILL LEAN TOWARD A MODEL CONSENSUS BLEND
THROUGH NEXT WEEKEND.

&&

.AVIATION...
505 PM CST SUN DEC 23 2012

CLOUDS WILL BE ON THE INCREASE TONIGHT AS AN UPPER LEVEL SHORTWAVE
APPROACHES FROM THE PLAINS. CIGS WILL LOWER OVERNIGHT...WITH
RAP13/NAM12 RH FIELDS/BUFKIT SOUNDINGS POINTING TO AN INCREASE IN
LOW LEVEL SATURATION. RAP LOOKS A BIT OVERDONE COMPARED TO SATELLITE
IMAGERY AND SFC OBS. WILL HAVE TO RELY ON SATELLITE/OBS TRENDS TO
BRING IN LOWER CIGS. PCPN WILL COME WITH THE SHORTWAVE...BUT WHAT
AND HOW MUCH IS IN QUESTION. TIME/HEIGHT X-SECTIONS AND BUFKIT
SOUNDINGS BOTH HAVE A DRY LAYER BETWEEN 900-750 MB...WHICH WOULD
NEED TO BE SATURATED FOR SNOW...OR SHALLOW ENOUGH FOR A
SEEDER/FEEDER PROCESS. IF NOT...THERE APPEARS TO BE ENOUGH
ISENTROPIC UPGLIDE IN THE LOW/NEAR SFC SATURATION THAT FREEZING
DRIZZLE COULD BE POSSIBLE. WILL STICK WITH SNOW FOR KRST/KLSE FOR
NOW...THE MORE PROBABLE OUTCOME. ANY SNOW ACCUMS WOULD BE MINIMAL.

THE SNOW SHOULD CLEAR TO THE EAST BY 21Z OR SO...BUT SOUNDINGS
CONTINUE TO FAVOR KEEPING LOW SATURATION UNDER AN INVERSION FOR THE
NIGHTTIME HOURS. THINK THERE SHOULD BE SOME IMPROVEMENT IN
CIGS...BUT COULD STAY AT LEAST MVFR THROUGH MUCH OF THE NIGHT...WITH
CLEARING THEN FOR CHRISTMAS DAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
237 PM CST SUN DEC 23 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...WETENKAMP
LONG TERM....WETENKAMP
AVIATION.....RIECK












AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 500 PM CST SAT DEC 22 2012

.SHORT TERM...TONIGHT THROUGH CHRISTMAS DAY
247 PM CST SAT DEC 22 2012

MAIN FORECAST CONCERNS REMAIN ON LOW CLOUD POTENTIAL TONIGHT AND
LIGHT SNOW CHANCES SUNDAY NIGHT THROUGH MONDAY.

LATEST WATER VAPOR IMAGERY SHOWED A BROAD UPPER LEVEL RIDGE OVER THE
CENTRAL CONUS...WITH A DEEP TROUGH OVER THE EASTERN U.S. AND
ANOTHER TROUGH OFF OF THE WEST COAST MOVING INTO THE PACIFIC
NORTHWEST. WEST/NORTHWEST FLOW ALOFT WAS NOTED ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. AN EMBEDDED SHORTWAVE WAS MOVING
SOUTHEAST ACROSS SOUTHERN MANITOBA...HEADED FOR NORTHERN
MINNESOTA. SURFACE OBSERVATIONS SHOWED A WEAK TROUGH EXTENDING
FROM SOUTHWEST ONTARIO...NEAR THE MN/ONTARIO BORER...SOUTH THROUGH
CENTRAL MINNESOTA INTO FAR SOUTHEAST SOUTH DAKOTA....DRIFTING
SOUTHEAST.

THE SURFACE TROUGH WILL CONTINUE ITS SOUTHEAST PROGRESSION...MOVING
ACROSS THE FORECAST AREA THIS EVENING WITH THE MAIN IMPACT BEING A
WIND SWITCH TO THE NORTH/NORTHWEST AND THE POSSIBILITY OF SEEING
SOME LOW CLOUD DEVELOPMENT. THE NAM CONTINUES TO SHOW 925 MB
RELATIVE HUMIDITY INCREASING INTO THE 90-94 PERCENT RANGE THIS
EVENING. THE RUC IS ALSO HINTING AT THIS INCREASE IN RELATIVE
HUMIDITY BUT ITS A LITTLE LATER THAN THE NAM. THINKING A SCATTERED
TO BROKEN LOW STRATUS DECK WILL DEVELOP. PLAN ON MOSTLY CLEAR SKIES
THIS EVENING...POSSIBLY BECOMING PARTLY CLOUDY LATE THIS EVENING
THROUGH THE LATE NIGHT HOURS IF THE STRATUS DEVELOPS. LOOK FOR LOW
TEMPERATURES TO FALL INTO THE SINGLE DIGITS.

WEAK HIGH PRESSURE WILL ATTEMPTS TO BUILD INTO THE UPPER MISSISSIPPI
RIVER VALLEY ON SUNDAY. NORTHERLY FLOW WILL BRING LAKE EFFECT CLOUDS
TO MUCH OF NORTHERN WISCONSIN OFF OF LAKE SUPERIOR. ALSO...HIGH AND
MID LEVEL CLOUDS WILL BE ON THE INCREASE ON SUNDAY AS A SHORTWAVE
TROUGH MOVES ACROSS THE DAKOTAS AND HEADS EAST TOWARD THE UPPER
MISSISSIPPI RIVER VALLEY. COOLER AIR WILL MOVE OVER THE AREA ON
SUNDAY WITH HIGHS IN THE UPPER TEENS TO LOWER 20S. THE TROUGH IS
EXPECTED TO PUSH INTO WESTERN MINNESOTA/NORTHWEST IOWA LATE SUNDAY
NIGHT THEN INTO CENTRAL IOWA AND SOUTHWEST WISCONSIN DURING THE DAY
ON MONDAY. THE LATEST MODEL GUIDANCE SUGGEST A SLIGHTLY MORE
SOUTHWESTERLY TRACK. THE NAM TAKES THE MAIN PVA...IN THE 300-500 MB
LAYER...ACROSS IOWA JUST BRUSHING SOUTHEAST MINNESOTA AND FAR
SOUTHWEST WISCONSIN. THE GFS IS ALSO LEANING TOWARD A MORE SOUTHERLY
TRACK BUT BRINGS TWO PIECES OF ENERGY THROUGH THE AREA. THE FIRST
PASSES ACROSS SOUTHWESTERN PARTS OF THE FORECAST AREA MAINLY MONDAY
MORNING WITH A SECONDARY WAVE MOVING ACROSS NORTHERN WISCONSIN.
MUCH OF THE FORECAST AREA SHOULD SEE LIGHT SNOW OUT OF THIS SYSTEM
LATE SUNDAY NIGHT INTO MONDAY MORNING. THE HIGHEST CHANCES FOR
MEASURABLE SNOW LOOKS TO BE SOUTH OF INTERSTATE 94. THINKING UP TO
AN INCH IS POSSIBLE ACROSS THESE AREAS SO WILL BE INCREASING
PRECIPITATION CHANCES. WILL MAINTAIN OCCASIONAL VERY LIGHT SNOW
WORDING. HIGH TEMPERATURES ON MONDAY WILL RANGE FROM THE LOWER 20S
ACROSS NORTHERN WISCONSIN TO THE MID TEENS ACROSS WESTERN SECTIONS
OF NORTHEAST IOWA INTO PORTIONS OF SOUTHEAST MINNESOTA. COLDER AIR
WILL SLIDE BACK INTO THE REGION MONDAY NIGHT WITH LOWS FALLING INTO
THE SINGLE DIGITS ABOVE ZERO. FAVORED COLD SPOTS COULD FALL INTO THE
SINGLE DIGITS BELOW ZERO. COOL HIGH PRESSURE WILL REMAIN OVER THE
AREA ON TUESDAY PROVIDING PARTLY SUNNY SKIES AND HIGHS MAINLY IN THE
TEENS. A POTENT UPPER TROUGH IS EXPECTED TO MOVE ACROSS THE SOUTHERN
PLAINS TUESDAY AND HEAD TOWARDS THE LOWER TO MIDDLE MISSISSIPPI
RIVER VALLEY.

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
247 PM CST SAT DEC 22 2012

22.12 MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT TUESDAY NIGHT
INTO WEDNESDAY SHOWING THE SOUTHERN STREAM TROUGH LIFTING NORTH INTO
THE OHIO RIVER VALLEY AND CLOSING INTO AN UPPER LOW. THIS SYSTEM IS
EXPECTED TO REMAIN WELL TO THE EAST OF THE AREA AS IT LIFTS INTO NEW
ENGLAND WEDNESDAY NIGHT INTO THURSDAY. HIGH PRESSURE WILL MAINTAIN
COOL AND QUIET WEATHER THROUGH THURSDAY WITH HIGHS IN THE TEENS AND
LOWS RANGING FROM THE SINGLE DIGITS BELOW ZERO TO SINGLE DIGITS
ABOVE ZERO. ANOTHER TROUGH WILL CROSS THE ROCKIES ONT THURSDAY AND
MOVE INTO THE PLAINS DURING THE DAY ON FRIDAY. FORECAST MODELS START
TO DIVERGE FRIDAY INTO SATURDAY ON THE EVOLUTION OF THIS TROUGH. THE
ECMWF CONTINUES TO WRAP THIS SYSTEM INTO AN UPPER LOW AS IT LIFTS
INTO THE GREAT LAKES AND MERGES WITH A TROUGH MOVING SOUTHEAST
ACROSS SOUTHERN ALBERTA/SASKATCHEWAN. THE ECMWF SOLUTION WOULD BRING
A PROLONGED PERIOD OF LIGHT SNOW TO THE FORECAST AREA. THE GFS KEEPS
THESE TWO SYSTEMS FROM MERGING AND BRINGS THE NORTHERN STREAM TROUGH
ACROSS THE FORECAST AREA DURING THE DAY ON SATURDAY. GIVEN THE
VARYING MODEL SOLUTIONS DECIDED TO LEAN TOWARD A MODEL CONSENSUS
BLEND APPROACH WITH CHANCES FOR LIGHT SNOW FRIDAY THROUGH
SATURDAY.

&&

.AVIATION...
500 PM CST SAT DEC 22 2012

THE CONCERN TONIGHT IS FOR THE POTENTIAL OF A LOW STRATUS LAYER.
RAP13/NAM12 SHOW AN AREA OF LOW LEVEL SATURATION ACROSS THE
DAKOTAS/NORTHWEST MN...BRINGING THIS SOUTH THROUGH THE NIGHT. THE
RAP13 IS MORE AGGRESSIVE IN ITS EASTWARD EXTENT ON THE STRATUS...AND
WOULD HAVE IT IMPACT KRST OVERNIGHT. SOME SFC OBS OVER WESTERN MN
INDICATE CIGS AROUND 1 KFT...ALTHOUGH NOTHING SEEN ON FOG/STRATUS
SATELLITE IMAGERY. A CLOSER LOOK AT VSBY DURING THE DAYLIGHT HOURS
DOES SHOW SOME VERY SHALLOW CLOUDS STREETS THAT COULD BE RESPONSIBLE
FOR THE OBS. OR...IT COULD ALSO BE SUSPENDED ICE CRYSTALS IN THE
COLDER AIR. BUFKIT SOUNDINGS HAVE A LOW LEVEL INVERSION INTO SUN
MORNING. IF ANY MOISTURE COULD POOL UNDER THAT...STRATUS AND
POSSIBLY SOME BR COULD DEVELOP. CONFIDENCE NOT OVERLY HIGH AT THE
MOMENT THOUGH...AND WILL KEEP ANY CIGS WEST OF THE KRST/KLSE
TONIGHT.

HIGH CLOUDS WILL BE THE INCREASE SUN AFTERNOON...AHEAD OF AN
APPROACHING UPPER LEVEL SHORTWAVE TROUGH. THE CLOUDS WILL GRADUALLY
THICKEN...WITH SOME LOWERING BY MONDAY MORNING. S-- LOOKS LIKE A
GOOD BET LATE SUN NIGHT/MON MORNING...BUT MINIMAL IF ANY
ACCUMULATION. BUFKIT SOUNDINGS SUGGEST MVFR/IFR CIGS WILL RETURN BY
MONDAY MORNING...WHICH COULD HANG AROUND FOR MUCH OF THE DAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
247 PM CST SAT DEC 22 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...WETENKAMP
LONG TERM....WETENKAMP
AVIATION.....RIECK










AREA FORECAST DISCUSSION

NWS GREEN BAY WI

 307 PM CST SAT DEC 22 2012

.SHORT TERM...TONIGHT AND SUNDAY.

LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A COUPLE WEAK
SHORTWAVES...ONE OVER SOUTHEAST SOUTH DAKOTA AND ANOTHER OVER
SOUTHWEST ONTARIO...AND THEY ARE PUSHING AN EQUALLY WEAK COLD FRONT
OVER NORTHWEST WISCONSIN EARLY THIS AFTERNOON. WIDELY SCT FLURRY
ACTIVITY WAS REPORTED IN THE OBS EARLIER TODAY OVER EASTERN NORTH
DAKOTA AND NORTHERN MINNESOTA...BUT NOTHING SO FAR CLOSER TO
WISCONSIN.  OTHERWISE...JUST HAVE SOME CIRRUS PASSING OVER CENTRAL
AND SOUTHERN PORTIONS OF THE STATE...AND A BATCH OF MID CLOUDS OVER
NORTHERN WISCONSIN AND THE UPPER PENINSULA.  THE MAIN FORECAST
CONCERNS ARE CLOUDS AND LAKE EFFECT SNOW SHOWERS AS WINDS SHIFT TO
THE NORTHWEST FOLLOWING THE PASSAGE OF THE COLD FRONT.

TONIGHT...THE WEAK COLD FRONT WILL PASS ACROSS THE REGION THIS
EVENING WHICH WILL SHIFT WINDS BACK TO THE NORTH-NORTHWEST.  THIN
RIBBON OF MID-LEVEL MOISTURE WILL GET STRETCHED OUT ALONG THE FRONT
THIS EVENING WHICH SHOULD LEAVE MOSTLY CLEAR TO PARTLY CLOUDY
CONDITIONS ACROSS THE REGION.  BEHIND THE FRONT...A SHALLOW ARCTIC
AIRMASS WILL FILTER SOUTHEAST ACROSS THE NORTHERN WISCONSIN.
STEEPENING LOW LEVEL LAPSE RATES BENEATH A SHARP INVERSION WILL
PROMOTE THE ADVECTION OF LAKE EFFECT CLOUDS OFF LAKE SUPERIOR INTO
NORTHERN WISCONSIN.  CAN SEE FLURRIES OR LIGHT SNOW SHOWERS
IMPACTING THE VILAS AND NORTHERN PARTS OF ONEIDA AND FOREST
COUNTY...MAINLY AFTER MIDNIGHT WITH ONLY VERY SMALL ACCUMULATIONS
EXPECTED.  THE CLOUDS MAY MAKE A RUN AT WAUSAU/SHAWANO AND CRIVITZ
LATE.  LOW LEVEL WINDS OF 15-20 KTS IS MARGINAL FOR DECOUPLING...BUT
CLOUDS ACROSS THE NORTH SHOULD KEEP THEM WARMER THAN LAST NIGHT.
WILL GO WITH LOWS FROM THE MID-SINGLE DIGITS OVER CENTRAL
WISCONSIN...TO THE LOWER 20S NEAR THE LAKE MICHIGAN SHORELINE.

SUNDAY...CANADIAN HIGH PRESSURE WILL GRADUALLY BUILD INTO THE REGION
THROUGH THE DAY.  MVFR STRATO-CU WILL LIKELY CREATE A PARTLY TO
MOSTLY CLOUDY START TO THE DAY NORTHWEST OF A AUW TO MNM LINE AS
FLOW WILL REMAIN OUT OF THE NW FOR A GOOD CHUNK OF THE DAY.  AM
COUNTING ON WEAK MIXING TO FORCE THE LOW CLOUDS TO RETREAT SOMEWHAT
DURING THE AFTERNOON BUT WILL KEEP PARTLY SUNNY TO MOSTLY CLOUDY
WORDING IN THE GRIDS OVER N-C WISCONSIN.  THE RIGHT REAR QUAD OF A JET
STREAK THEN SHIFTS EAST FROM THE NORTHERN PLAINS AND ACROSS THE
STATE DURING THE AFTERNOON.  PLENTY OF DRY AIR IN THE MID-LEVELS
WILL KEEP THE AREA PRECIP FREE...BUT SHOULD SEE A DECENT CIRRUS
SHIELD ARRIVE.  TEMPS WILL FALL ABOUT 5 DEGREES UP NORTH COMPARED TO
TODAY...PLACING HIGHS IN THE LOW TO MID 20S ACROSS THE REGION.

.LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY.

MODELS SHOWED A MORE ACTIVE WEATHER PATTERN DURING THE PERIOD WITH
LOW AMPLITUDE UPPER LEVEL FLOW THROUGH EARLY NEXT WEEK BEFORE A
WEST COAST TROUGH PUSHES EASTWARD. MODELS WERE IN GOOD AGREEMENT
IN TAKING A 500MB TROUGH THROUGH THE WESTERN GREAT LAKES REGION ON
MONDAY...BUT MOST OF THE ENERGY WITH THAT SHORT WAVE REMAINS SOUTH
OF THE FORECAST AREA. HAVE INCLUDED SOME LOW END CHANCE POPS TO
COVER THAT EVENT. NOT SO MUCH AGREEMENT ON THE PATH OF A STRONGER
SYSTEM THAT WILL BE MOVING NORTHEAST OUT OF THE SOUTHERN PLAINS
MIDWEEK. 12Z ECMWF WOULD HAVE IT MISS THE AREA WHILE THE 12Z GFS
BRINGS QPF TO THE SOUTHEAST 1/3 TO 1/2 OF THE AREA. THERE IS
SLIGHTLY BETTER AGREEMENT IN TAKING A TROUGH ACROSS THE REGION AT
THE END OF THE PERIOD. SO HAVE CHANCE POPS FRIDAY NIGHT AND SATURDAY.

TEMPERATURES SHOULD START THE PERIOD SLIGHTLY BELOW NORMAL BUT
WARM TO NEAR NORMAL BY NEXT WEEKEND.
&&

.AVIATION...A WEAK COLD FRONT WILL PASS ACROSS THE REGION THIS
EVENING.  MID AND HIGH CLOUDS WILL PASS OVERHEAD AHEAD OF THE FRONT
LEAVING VFR CONDITIONS THROUGH MUCH OF THE EVENING.  WINDS WILL
SHIFT TO THE NNW BEHIND THE FRONT...BRINGING IN A SHALLOW ARCTIC
AIRMASS AS WELL AS LAKE CLOUDS OFF LAKE SUPERIOR.  THESE MVFR CLOUDS
WILL PUSH SOUTHEAST THROUGH THE NIGHT...FROM ABOUT AUW TO MNM BY
EARLY SUNDAY MORNING. THESE CLOUDS WILL LIKELY RETREAT A BIT MIDDAY
ONWARD ON SUNDAY.

MPC
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$
MPC/MG





AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 247 PM CST SAT DEC 22 2012

.SHORT TERM...TONIGHT THROUGH CHRISTMAS DAY
247 PM CST SAT DEC 22 2012

MAIN FORECAST CONCERNS REMAIN ON LOW CLOUD POTENTIAL TONIGHT AND
LIGHT SNOW CHANCES SUNDAY NIGHT THROUGH MONDAY.

LATEST WATER VAPOR IMAGERY SHOWED A BROAD UPPER LEVEL RIDGE OVER THE
CENTRAL CONUS...WITH A DEEP TROUGH OVER THE EASTERN U.S. AND
ANOTHER TROUGH OFF OF THE WEST COAST MOVING INTO THE PACIFIC
NORTHWEST. WEST/NORTHWEST FLOW ALOFT WAS NOTED ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. AN EMBEDDED SHORTWAVE WAS MOVING
SOUTHEAST ACROSS SOUTHERN MANITOBA...HEADED FOR NORTHERN
MINNESOTA. SURFACE OBSERVATIONS SHOWED A WEAK TROUGH EXTENDING
FROM SOUTHWEST ONTARIO...NEAR THE MN/ONTARIO BORER...SOUTH THROUGH
CENTRAL MINNESOTA INTO FAR SOUTHEAST SOUTH DAKOTA....DRIFTING
SOUTHEAST.

THE SURFACE TROUGH WILL CONTINUE ITS SOUTHEAST PROGRESSION...MOVING
ACROSS THE FORECAST AREA THIS EVENING WITH THE MAIN IMPACT BEING A
WIND SWITCH TO THE NORTH/NORTHWEST AND THE POSSIBILITY OF SEEING
SOME LOW CLOUD DEVELOPMENT. THE NAM CONTINUES TO SHOW 925 MB
RELATIVE HUMIDITY INCREASING INTO THE 90-94 PERCENT RANGE THIS
EVENING. THE RUC IS ALSO HINTING AT THIS INCREASE IN RELATIVE
HUMIDITY BUT ITS A LITTLE LATER THAN THE NAM. THINKING A SCATTERED
TO BROKEN LOW STRATUS DECK WILL DEVELOP. PLAN ON MOSTLY CLEAR SKIES
THIS EVENING...POSSIBLY BECOMING PARTLY CLOUDY LATE THIS EVENING
THROUGH THE LATE NIGHT HOURS IF THE STRATUS DEVELOPS. LOOK FOR LOW
TEMPERATURES TO FALL INTO THE SINGLE DIGITS.

WEAK HIGH PRESSURE WILL ATTEMPTS TO BUILD INTO THE UPPER MISSISSIPPI
RIVER VALLEY ON SUNDAY. NORTHERLY FLOW WILL BRING LAKE EFFECT CLOUDS
TO MUCH OF NORTHERN WISCONSIN OFF OF LAKE SUPERIOR. ALSO...HIGH AND
MID LEVEL CLOUDS WILL BE ON THE INCREASE ON SUNDAY AS A SHORTWAVE
TROUGH MOVES ACROSS THE DAKOTAS AND HEADS EAST TOWARD THE UPPER
MISSISSIPPI RIVER VALLEY. COOLER AIR WILL MOVE OVER THE AREA ON
SUNDAY WITH HIGHS IN THE UPPER TEENS TO LOWER 20S. THE TROUGH IS
EXPECTED TO PUSH INTO WESTERN MINNESOTA/NORTHWEST IOWA LATE SUNDAY
NIGHT THEN INTO CENTRAL IOWA AND SOUTHWEST WISCONSIN DURING THE DAY
ON MONDAY. THE LATEST MODEL GUIDANCE SUGGEST A SLIGHTLY MORE
SOUTHWESTERLY TRACK. THE NAM TAKES THE MAIN PVA...IN THE 300-500 MB
LAYER...ACROSS IOWA JUST BRUSHING SOUTHEAST MINNESOTA AND FAR
SOUTHWEST WISCONSIN. THE GFS IS ALSO LEANING TOWARD A MORE SOUTHERLY
TRACK BUT BRINGS TWO PIECES OF ENERGY THROUGH THE AREA. THE FIRST
PASSES ACROSS SOUTHWESTERN PARTS OF THE FORECAST AREA MAINLY MONDAY
MORNING WITH A SECONDARY WAVE MOVING ACROSS NORTHERN WISCONSIN.
MUCH OF THE FORECAST AREA SHOULD SEE LIGHT SNOW OUT OF THIS SYSTEM
LATE SUNDAY NIGHT INTO MONDAY MORNING. THE HIGHEST CHANCES FOR
MEASURABLE SNOW LOOKS TO BE SOUTH OF INTERSTATE 94. THINKING UP TO
AN INCH IS POSSIBLE ACROSS THESE AREAS SO WILL BE INCREASING
PRECIPITATION CHANCES. WILL MAINTAIN OCCASIONAL VERY LIGHT SNOW
WORDING. HIGH TEMPERATURES ON MONDAY WILL RANGE FROM THE LOWER 20S
ACROSS NORTHERN WISCONSIN TO THE MID TEENS ACROSS WESTERN SECTIONS
OF NORTHEAST IOWA INTO PORTIONS OF SOUTHEAST MINNESOTA. COLDER AIR
WILL SLIDE BACK INTO THE REGION MONDAY NIGHT WITH LOWS FALLING INTO
THE SINGLE DIGITS ABOVE ZERO. FAVORED COLD SPOTS COULD FALL INTO THE
SINGLE DIGITS BELOW ZERO. COOL HIGH PRESSURE WILL REMAIN OVER THE
AREA ON TUESDAY PROVIDING PARTLY SUNNY SKIES AND HIGHS MAINLY IN THE
TEENS. A POTENT UPPER TROUGH IS EXPECTED TO MOVE ACROSS THE SOUTHERN
PLAINS TUESDAY AND HEAD TOWARDS THE LOWER TO MIDDLE MISSISSIPPI
RIVER VALLEY.

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
247 PM CST SAT DEC 22 2012

22.12 MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT TUESDAY NIGHT
INTO WEDNESDAY SHOWING THE SOUTHERN STREAM TROUGH LIFTING NORTH INTO
THE OHIO RIVER VALLEY AND CLOSING INTO AN UPPER LOW. THIS SYSTEM IS
EXPECTED TO REMAIN WELL TO THE EAST OF THE AREA AS IT LIFTS INTO NEW
ENGLAND WEDNESDAY NIGHT INTO THURSDAY. HIGH PRESSURE WILL MAINTAIN
COOL AND QUIET WEATHER THROUGH THURSDAY WITH HIGHS IN THE TEENS AND
LOWS RANGING FROM THE SINGLE DIGITS BELOW ZERO TO SINGLE DIGITS
ABOVE ZERO. ANOTHER TROUGH WILL CROSS THE ROCKIES ONT THURSDAY AND
MOVE INTO THE PLAINS DURING THE DAY ON FRIDAY. FORECAST MODELS START
TO DIVERGE FRIDAY INTO SATURDAY ON THE EVOLUTION OF THIS TROUGH. THE
ECMWF CONTINUES TO WRAP THIS SYSTEM INTO AN UPPER LOW AS IT LIFTS
INTO THE GREAT LAKES AND MERGES WITH A TROUGH MOVING SOUTHEAST
ACROSS SOUTHERN ALBERTA/SASKATCHEWAN. THE ECMWF SOLUTION WOULD BRING
A PROLONGED PERIOD OF LIGHT SNOW TO THE FORECAST AREA. THE GFS KEEPS
THESE TWO SYSTEMS FROM MERGING AND BRINGS THE NORTHERN STREAM TROUGH
ACROSS THE FORECAST AREA DURING THE DAY ON SATURDAY. GIVEN THE
VARYING MODEL SOLUTIONS DECIDED TO LEAN TOWARD A MODEL CONSENSUS
BLEND APPROACH WITH CHANCES FOR LIGHT SNOW FRIDAY THROUGH
SATURDAY.

&&

.AVIATION...THIS AFTERNOON THROUGH SUNDAY
1133 AM CST SAT DEC 22 2012

GOOD VFR CONDITIONS WILL CONTINUE THIS AFTERNOON INTO THIS
EVENING...EVEN AS A WEAK TROUGH SLIDES SOUTHEAST ACROSS THE REGION.
MAIN IMPACT WITH THIS FEATURE WILL BE A WIND SHIFT FROM LIGHT SOUTH
TO LIGHT NORTHWEST AND NORTH. MODELS CONTINUE TO SHOW AND INCREASE
OF VERY LOW LEVEL MOISTURE ACROSS THE AREA TONIGHT BEHIND THE
TROUGH...TRAPPED IN/UNDER A STRONG SFC-850MB INVERSION. MODELS PROG
THIS MOISTURE IN THE SFC-950MB LAYER...ON/NEAR SFC. NEAREST LOW
CLOUDS BEHIND THE TROUGH AT MID-DAY ARE IN NORTHERN ND. SUSPECT
MODELS ARE LOADING THE LOWEST LEVELS WITH SUBLIMATION MOISTURE FROM
THE SNOW COVER...WHICH IS THEN TRAPPED UNDER THE STRONG INVERSION.
LIMITED MENTION OF THIS MOISTURE TO SCT010-012 STRATO-CU CLOUDS IN
THE 03Z TO 10-12Z TIME-FRAME WHEN SKIES ABOVE WILL BE SCT200 OR
LESS...AND SOME MVFR VSBYS IN BR AT KRST FOR A FEW HOURS CENTERED ON
12Z SUN.

INCREASING HIGH LEVEL MOISTURE/THICKENING CIRRUS SPREAD EAST ACROSS
THE AREA LATE TONIGHT AND FOR SUN. ONCE THIS BKN-OVC CIRRUS DECK
MOVES IN LATE TONIGHT...ANY LOWER LEVEL STRATO-CU SHOULD DISSIPATE
BUT BR AT KRST WOULD BE A BIT MORE PERSISTENT INTO THE MID MORNING
HOURS. REMAINDER OF SUNDAY LOOKS VFR WITH BKN-OVC150-200 CIGS.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
247 PM CST SAT DEC 22 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION.....RRS







AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 1133 AM CST SAT DEC 22 2012

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
233 AM CST SAT DEC 22 2012

MAIN FORECAST CONCERNS ARE ON LOW CLOUD POTENTIAL TONIGHT INTO
SUNDAY AND POTENTIAL FOR SOME LIGHT SNOW SUNDAY NIGHT INTO MONDAY.

CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED DEEP TROUGHING APPROACHING THE WESTERN U.S. COAST...RIDGING
ACROSS THE PLAINS AND DEEP TROUGHING ALONG THE U.S. EAST COAST. ON
TOP OF THE RIDGE...A SHORTWAVE WAS PRESENT ACROSS CENTRAL PORTIONS
OF SASKATCHEWAN AND MANITOBA. THE FORECAST AREA LIES CLOSER TO THE
INFLECTION POINT BETWEEN THE RIDGE AND EAST COAST TROUGH...YIELDING
HIGH PRESSURE AT THE SURFACE. OTHER THAN SOME SCATTERED HIGH CLOUDS
ASSOCIATED WITH A COMBINATION OF PACIFIC MOISTURE TOPPING THE RIDGE
AND A 100 KT JET NEAR THE TROPOPAUSE...SKIES WERE MOSTLY CLEAR
ACROSS THE FORECAST AREA. DRY AIR AND SUBSIDENCE SEEN ON THE 00Z
ABR...MPX AND DVN SOUNDINGS ARE HELPING TO PRODUCE THE MOSTLY CLEAR
SKIES. WITH LIGHT WINDS UNDER THE SURFACE RIDGE AND THE FRESH SNOW
COVER...TEMPERATURES HAVE MOSTLY FALLEN INTO THE SINGLE DIGITS ABOVE
ZERO. BLACK RIVER FALLS AND SPARTA HAVE EVEN DROPPED BELOW ZERO. TO
THE NORTHWEST...A COLD FRONT WAS LOCATED OVER MANITOBA AND THE
DAKOTAS ASSOCIATED WITH THE SOUTH CENTRAL CANADA SHORTWAVE. LOW
CLOUDS WERE PRESENT ACROSS SOUTH CENTRAL CANADA AS WELL BEHIND THE
FRONT.

TODAY AND TONIGHT...THE SHORTWAVE SEEN OVER SOUTH CENTRAL CANADA IS
PROGGED TO SLIDE SOUTHEAST ACROSS EASTERN LAKE SUPERIOR THIS
EVENING...DRIVING THE COLD FRONT ACROSS THE DAKOTAS THROUGH THE
FORECAST AREA. NO PRECIPITATION IS EXPECTED WITH OR BEHIND THE FRONT
GIVEN THE DRY AIRMASS PRESENT...AS WELL AS ALL THE FORCING LOCATED
WELL NORTHEAST OF THE AREA. MAIN CONCERNS WITH THE FRONT IS THE
WARMING AHEAD OF IT AND IF ANY LOW CLOUDS COME IN BEHIND IT.
REGARDING THE WARMING...GFS/NAM/ECMWF 925MB TEMPERATURE PROGS SHOW
THEM CLIMBING FROM -3 TO -6C CURRENTLY TO -2 TO -4C. WITH SOME SUN
THROUGH HIGH CLOUDS AND A SOUTHWEST BREEZE...TEMPERATURES SHOULD
EASILY CLIMB INTO THE 20S EVERYWHERE. SOME LOCATIONS IN WISCONSIN...
PARTICULARLY IN VALLEY AREAS...COULD EXCEED 30 THANKS TO LOWER
ALBEDO PRESENT. DECENT COLD ADVECTION LOOKS TO OCCUR TONIGHT BEHIND
THE FRONT AS 925MB TEMPS FALL TO -6 TO -10C BY 12Z SUNDAY ON 15-20
KT NORTHERLY BREEZE. CERTAINLY LOOKS GOOD FOR LAKE EFFECT OFF
SUPERIOR WHICH THE BREEZE WOULD THEN SEND THE CLOUDS SOUTHWARD AT
LEAST INTO THE NORTHERN HALF OF WISCONSIN AFTER MIDNIGHT. IN
ADDITION...SOME OF THE LOW CLOUDS IN GENERAL BEHIND THE FRONT COULD
END UP BEING SENT SOUTH. AS A RESULT...HAVE RAISED CLOUD COVER...
ESPECIALLY ACROSS TAYLOR AND CLARK COUNTIES GIVEN THE BETTER CHANCE
OF BEING IMPACTED BY LAKE EFFECT CLOUDS. GIVEN CLOUDS AND THE WINDS
BEHIND THE FRONT...FOLLOWED A BLEND OF GUIDANCE FOR LOWS.

SUNDAY AND SUNDAY NIGHT...FOCUS SHIFTS TO THE TROUGHING APPROACHING
THE WEST COAST. MODELS TAKE A FAIRLY SIGNIFICANT PORTION OF THE
TROUGH CROSSING THE NORTHERN ROCKIES DURING THE NEXT 24 TO 36 HOURS.
THE QUESTION IS WHAT HAPPENS WITH THE TROUGH FROM THERE. THE 22.00Z
NAM/UKMET ARE A WEAKER SCENARIO WITH THE TROUGH...STRETCHING FROM
NORTHEAST SOUTH DAKOTA INTO CENTRAL IOWA BY 12Z MONDAY.
MEANWHILE...THE 22.00Z GFS/CANADIAN DEPICT A MORE POTENT TROUGH THAT
ENDS UP CROSSING NEBRASKA AND BECOMING SITUATED DOWN IN SOUTHERN
IOWA INTO THE ST LOUIS AREA BY 12Z MONDAY. ALL SCENARIOS YIELD AN
INVERTED TROUGH AT THE SURFACE...JUST THE MORE POTENT GFS/CANADIAN
GROUP WOULD HAVE A BETTER SHOT OF YIELDING PRECIPITATION
DEVELOPMENT. GIVEN THE STRENGTH OF THE TROUGH RIGHT NOW OFF THE WEST
COAST...NOTED TOO BY NUMEROUS LIGHTNING STRIKES...WILL FAVOR THE
MORE POTENT GROUP. THIS MEANS 20 PERCENT CHANCES ARE NEEDED AFTER
MIDNIGHT SUNDAY NIGHT WEST OF THE MISSISSIPPI RIVER TO ACCOUNT FOR
THE DPVA AHEAD OF THE POTENT TROUGH...AS WELL AS ISENTROPIC LIFT.
DID NOT GO HIGHER THAN 20 BECAUSE OF INITIAL DRY AIR TO OVERCOME
SINCE THE SNOW THAT DOES FALL WILL COME OUT OF A MID CLOUD DECK.
OTHERWISE...THE ONLY OTHER CONCERN IS CLOUD COVER. THE LOW CLOUDS
OVER NORTHERN WI AT 12Z SUNDAY COULD END UP EXPANDING SOUTHWESTWARD
THROUGH THE DAY...WHILE MID AND HIGH CLOUDS INCREASE DOWNSTREAM OF
THE POTENT TROUGH. THUS AN INCREASING CLOUD TREND SEEMS APPROPRIATE.
THESE CLOUDS PLUS COLDER 925MB TEMPS IN THE -8 TO -10C RANGE WILL
DEFINITELY YIELD A COLDER DAY. ON THE POSITIVE SIDE...THE CLOUDS
SHOULD HELP HOLD TEMPERATURES UP SUNDAY NIGHT.

MONDAY INTO MONDAY NIGHT...FOLLOWING THE MORE POTENT TROUGH LOOK AS
MENTIONED IN THE SUNDAY/SUNDAY NIGHT DISCUSSION...THE GFS AND
CANADIAN SEND THE TROUGH SOUTHEAST INTO OHIO BY 00Z TUESDAY. CHANCES
OF SNOW STILL LOOK APPROPRIATE FOR MONDAY WITH ISENTROPIC LIFT AND
DPVA PERSISTING...THOUGH THIS SHOULD BE DIMINISHING IN THE AFTERNOON
AS THE TROUGH SHIFTS EAST AND CANADIAN HIGH PRESSURE BUILDS SOUTH
INTO THE DAKOTAS IN ITS WAKE. AS SUCH...MONDAY NIGHT IS LIKELY TO
END UP DRY. REGARDING THE ACTUAL CHANCES...LINGERING LOWER LEVEL DRY
AIR IS A BIG CONCERN...AS WELL AS THE TRACK OF THE TROUGH DROPPING
MORE TO OUR SOUTH. AS A RESULT...KEPT CHANCES IN A 20-30 RANGE.
LOOKS GOOD FOR MOST OF THE AREA TO PICK UP A LITTLE SNOW...BE IT
ACTUAL ACCUMULATING SNOW OR FLURRIES...SO USED OCCASIONAL VERY LIGHT
SNOW VERBIAGE. GIVEN CANADIAN HIGH PRESSURE BUILDING SOUTH...ONE CAN
EXPECT COLDER LOW LEVEL AIR. THIS IS VERY WELL REPRESENTED BY 925MB
TEMPS WHICH FALL TO -10 TO -14C BY 00Z TUESDAY AND -12 TO -14C TO
START OFF CHRISTMAS MORNING. TRENDED BOTH HIGHS AND LOWS COLDER...
CLOSER TO GUIDANCE.

.LONG TERM...CHRISTMAS DAY THROUGH FRIDAY NIGHT
233 AM CST SAT DEC 22 2012

GOOD AGREEMENT CONTINUES FROM YESTERDAY ON THE GENERAL UPPER LEVEL
PATTERN THROUGH THE LONG TERM PERIOD. 22.00Z ECMWF/GFS/CANADIAN AND
UKMET CONTINUE TO SHOW A STRONG TROUGH AND STORM SYSTEM TRACKING
FROM THE SOUTHERN PLAINS ON TUESDAY INTO THE MID-ATLANTIC REGION BY
EARLY THURSDAY. THE FORECAST AREA REMAINS PLENTY FAR AWAY FROM THIS
SYSTEM...KEEPING US IN SUBSIDENCE AND MORE UNDER THE INFLUENCE OF
CANADIAN HIGH PRESSURE. IN FACT...THIS PERIOD FROM CHRISTMAS DAY
THROUGH WEDNESDAY NIGHT LOOKS SEASONABLY COOL...DUE TO 925MB TEMPS
REMAINING BETWEEN -10 AND -14C. WILL REALLY HAVE TO WATCH LOW
TEMPERATURES FOR CLEAR SKIES AND LIGHT WINDS...AS THE SNOW COVER NOW
IN PLACE FAVORS PLUMMETING. HAVE ADJUSTED BOTH HIGH AND LOW
TEMPERATURES DOWNWARD FROM THE PREVIOUS FORECAST ABOUT 5 DEGREES OR
SO...BUT FURTHER LOWERING MAY BE NEEDED...ESPECIALLY WITH LOWS. FOR
THURSDAY ONWARDS...ANOTHER DEEP TROUGH IS PROGGED TO FORM OVER THE
SOUTHWESTERN U.S...BUT THIS ONE GETS EJECTED NORTHEASTWARD TOWARDS
THE FORECAST AREA FOR FRIDAY AND INTO THE WEEKEND. AT THIS POINT
THERE DOES NOT APPEAR TO BE ANY BIG STORM PER SE WITH THIS
TROUGH...BUT SOME WARM ADVECTION SNOW IS SUGGESTED FOR FRIDAY INTO
FRIDAY NIGHT. THUS...30-40 PERCENT CHANCES OF PRECIPITATION ARE IN
THE FORECAST. THE APPROACH OF THE TROUGH SHOULD ALSO HELP TO BRING
WARMER AIR INTO THE FORECAST AREA...AND THIS IS NOTED BY 925MB TEMPS
PROGGED TO CLIMB TO -8 TO -10C AT 00Z FRIDAY AND -6 TO -9C AT 00Z
SATURDAY. FOLLOWED MODEL CONSENSUS FOR HIGHS AND LOWS FROM THURSDAY
ONWARDS...WHICH BRINGS TEMPERATURES BACK UP TO NORMAL FOR FRIDAY.

&&

.AVIATION...THIS AFTERNOON THROUGH SUNDAY
1133 AM CST SAT DEC 22 2012

GOOD VFR CONDITIONS WILL CONTINUE THIS AFTERNOON INTO THIS
EVENING...EVEN AS A WEAK TROUGH SLIDES SOUTHEAST ACROSS THE REGION.
MAIN IMPACT WITH THIS FEATURE WILL BE A WIND SHIFT FROM LIGHT SOUTH
TO LIGHT NORTHWEST AND NORTH. MODELS CONTINUE TO SHOW AND INCREASE
OF VERY LOW LEVEL MOISTURE ACROSS THE AREA TONIGHT BEHIND THE
TROUGH...TRAPPED IN/UNDER A STRONG SFC-850MB INVERSION. MODELS PROG
THIS MOISTURE IN THE SFC-950MB LAYER...ON/NEAR SFC. NEAREST LOW
CLOUDS BEHIND THE TROUGH AT MID-DAY ARE IN NORTHERN ND. SUSPECT
MODELS ARE LOADING THE LOWEST LEVELS WITH SUBLIMATION MOISTURE FROM
THE SNOW COVER...WHICH IS THEN TRAPPED UNDER THE STRONG INVERSION.
LIMITED MENTION OF THIS MOISTURE TO SCT010-012 STRATO-CU CLOUDS IN
THE 03Z TO 10-12Z TIME-FRAME WHEN SKIES ABOVE WILL BE SCT200 OR
LESS...AND SOME MVFR VSBYS IN BR AT KRST FOR A FEW HOURS CENTERED ON
12Z SUN.

INCREASING HIGH LEVEL MOISTURE/THICKENING CIRRUS SPREAD EAST ACROSS
THE AREA LATE TONIGHT AND FOR SUN. ONCE THIS BKN-OVC CIRRUS DECK
MOVES IN LATE TONIGHT...ANY LOWER LEVEL STRATO-CU SHOULD DISSIPATE
BUT BR AT KRST WOULD BE A BIT MORE PERSISTENT INTO THE MID MORNING
HOURS. REMAINDER OF SUNDAY LOOKS VFR WITH BKN-OVC150-200 CIGS.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
233 AM CST SAT DEC 22 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...AJ
LONG TERM....AJ
AVIATION.....RRS










AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 555 AM CST SAT DEC 22 2012

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
233 AM CST SAT DEC 22 2012

MAIN FORECAST CONCERNS ARE ON LOW CLOUD POTENTIAL TONIGHT INTO
SUNDAY AND POTENTIAL FOR SOME LIGHT SNOW SUNDAY NIGHT INTO MONDAY.

CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED DEEP TROUGHING APPROACHING THE WESTERN U.S. COAST...RIDGING
ACROSS THE PLAINS AND DEEP TROUGHING ALONG THE U.S. EAST COAST. ON
TOP OF THE RIDGE...A SHORTWAVE WAS PRESENT ACROSS CENTRAL PORTIONS
OF SASKATCHEWAN AND MANITOBA. THE FORECAST AREA LIES CLOSER TO THE
INFLECTION POINT BETWEEN THE RIDGE AND EAST COAST TROUGH...YIELDING
HIGH PRESSURE AT THE SURFACE. OTHER THAN SOME SCATTERED HIGH CLOUDS
ASSOCIATED WITH A COMBINATION OF PACIFIC MOISTURE TOPPING THE RIDGE
AND A 100 KT JET NEAR THE TROPOPAUSE...SKIES WERE MOSTLY CLEAR
ACROSS THE FORECAST AREA. DRY AIR AND SUBSIDENCE SEEN ON THE 00Z
ABR...MPX AND DVN SOUNDINGS ARE HELPING TO PRODUCE THE MOSTLY CLEAR
SKIES. WITH LIGHT WINDS UNDER THE SURFACE RIDGE AND THE FRESH SNOW
COVER...TEMPERATURES HAVE MOSTLY FALLEN INTO THE SINGLE DIGITS ABOVE
ZERO. BLACK RIVER FALLS AND SPARTA HAVE EVEN DROPPED BELOW ZERO. TO
THE NORTHWEST...A COLD FRONT WAS LOCATED OVER MANITOBA AND THE
DAKOTAS ASSOCIATED WITH THE SOUTH CENTRAL CANADA SHORTWAVE. LOW
CLOUDS WERE PRESENT ACROSS SOUTH CENTRAL CANADA AS WELL BEHIND THE
FRONT.

TODAY AND TONIGHT...THE SHORTWAVE SEEN OVER SOUTH CENTRAL CANADA IS
PROGGED TO SLIDE SOUTHEAST ACROSS EASTERN LAKE SUPERIOR THIS
EVENING...DRIVING THE COLD FRONT ACROSS THE DAKOTAS THROUGH THE
FORECAST AREA. NO PRECIPITATION IS EXPECTED WITH OR BEHIND THE FRONT
GIVEN THE DRY AIRMASS PRESENT...AS WELL AS ALL THE FORCING LOCATED
WELL NORTHEAST OF THE AREA. MAIN CONCERNS WITH THE FRONT IS THE
WARMING AHEAD OF IT AND IF ANY LOW CLOUDS COME IN BEHIND IT.
REGARDING THE WARMING...GFS/NAM/ECMWF 925MB TEMPERATURE PROGS SHOW
THEM CLIMBING FROM -3 TO -6C CURRENTLY TO -2 TO -4C. WITH SOME SUN
THROUGH HIGH CLOUDS AND A SOUTHWEST BREEZE...TEMPERATURES SHOULD
EASILY CLIMB INTO THE 20S EVERYWHERE. SOME LOCATIONS IN WISCONSIN...
PARTICULARLY IN VALLEY AREAS...COULD EXCEED 30 THANKS TO LOWER
ALBEDO PRESENT. DECENT COLD ADVECTION LOOKS TO OCCUR TONIGHT BEHIND
THE FRONT AS 925MB TEMPS FALL TO -6 TO -10C BY 12Z SUNDAY ON 15-20
KT NORTHERLY BREEZE. CERTAINLY LOOKS GOOD FOR LAKE EFFECT OFF
SUPERIOR WHICH THE BREEZE WOULD THEN SEND THE CLOUDS SOUTHWARD AT
LEAST INTO THE NORTHERN HALF OF WISCONSIN AFTER MIDNIGHT. IN
ADDITION...SOME OF THE LOW CLOUDS IN GENERAL BEHIND THE FRONT COULD
END UP BEING SENT SOUTH. AS A RESULT...HAVE RAISED CLOUD COVER...
ESPECIALLY ACROSS TAYLOR AND CLARK COUNTIES GIVEN THE BETTER CHANCE
OF BEING IMPACTED BY LAKE EFFECT CLOUDS. GIVEN CLOUDS AND THE WINDS
BEHIND THE FRONT...FOLLOWED A BLEND OF GUIDANCE FOR LOWS.

SUNDAY AND SUNDAY NIGHT...FOCUS SHIFTS TO THE TROUGHING APPROACHING
THE WEST COAST. MODELS TAKE A FAIRLY SIGNIFICANT PORTION OF THE
TROUGH CROSSING THE NORTHERN ROCKIES DURING THE NEXT 24 TO 36 HOURS.
THE QUESTION IS WHAT HAPPENS WITH THE TROUGH FROM THERE. THE 22.00Z
NAM/UKMET ARE A WEAKER SCENARIO WITH THE TROUGH...STRETCHING FROM
NORTHEAST SOUTH DAKOTA INTO CENTRAL IOWA BY 12Z MONDAY.
MEANWHILE...THE 22.00Z GFS/CANADIAN DEPICT A MORE POTENT TROUGH THAT
ENDS UP CROSSING NEBRASKA AND BECOMING SITUATED DOWN IN SOUTHERN
IOWA INTO THE ST LOUIS AREA BY 12Z MONDAY. ALL SCENARIOS YIELD AN
INVERTED TROUGH AT THE SURFACE...JUST THE MORE POTENT GFS/CANADIAN
GROUP WOULD HAVE A BETTER SHOT OF YIELDING PRECIPITATION
DEVELOPMENT. GIVEN THE STRENGTH OF THE TROUGH RIGHT NOW OFF THE WEST
COAST...NOTED TOO BY NUMEROUS LIGHTNING STRIKES...WILL FAVOR THE
MORE POTENT GROUP. THIS MEANS 20 PERCENT CHANCES ARE NEEDED AFTER
MIDNIGHT SUNDAY NIGHT WEST OF THE MISSISSIPPI RIVER TO ACCOUNT FOR
THE DPVA AHEAD OF THE POTENT TROUGH...AS WELL AS ISENTROPIC LIFT.
DID NOT GO HIGHER THAN 20 BECAUSE OF INITIAL DRY AIR TO OVERCOME
SINCE THE SNOW THAT DOES FALL WILL COME OUT OF A MID CLOUD DECK.
OTHERWISE...THE ONLY OTHER CONCERN IS CLOUD COVER. THE LOW CLOUDS
OVER NORTHERN WI AT 12Z SUNDAY COULD END UP EXPANDING SOUTHWESTWARD
THROUGH THE DAY...WHILE MID AND HIGH CLOUDS INCREASE DOWNSTREAM OF
THE POTENT TROUGH. THUS AN INCREASING CLOUD TREND SEEMS APPROPRIATE.
THESE CLOUDS PLUS COLDER 925MB TEMPS IN THE -8 TO -10C RANGE WILL
DEFINITELY YIELD A COLDER DAY. ON THE POSITIVE SIDE...THE CLOUDS
SHOULD HELP HOLD TEMPERATURES UP SUNDAY NIGHT.

MONDAY INTO MONDAY NIGHT...FOLLOWING THE MORE POTENT TROUGH LOOK AS
MENTIONED IN THE SUNDAY/SUNDAY NIGHT DISCUSSION...THE GFS AND
CANADIAN SEND THE TROUGH SOUTHEAST INTO OHIO BY 00Z TUESDAY. CHANCES
OF SNOW STILL LOOK APPROPRIATE FOR MONDAY WITH ISENTROPIC LIFT AND
DPVA PERSISTING...THOUGH THIS SHOULD BE DIMINISHING IN THE AFTERNOON
AS THE TROUGH SHIFTS EAST AND CANADIAN HIGH PRESSURE BUILDS SOUTH
INTO THE DAKOTAS IN ITS WAKE. AS SUCH...MONDAY NIGHT IS LIKELY TO
END UP DRY. REGARDING THE ACTUAL CHANCES...LINGERING LOWER LEVEL DRY
AIR IS A BIG CONCERN...AS WELL AS THE TRACK OF THE TROUGH DROPPING
MORE TO OUR SOUTH. AS A RESULT...KEPT CHANCES IN A 20-30 RANGE.
LOOKS GOOD FOR MOST OF THE AREA TO PICK UP A LITTLE SNOW...BE IT
ACTUAL ACCUMULATING SNOW OR FLURRIES...SO USED OCCASIONAL VERY LIGHT
SNOW VERBIAGE. GIVEN CANADIAN HIGH PRESSURE BUILDING SOUTH...ONE CAN
EXPECT COLDER LOW LEVEL AIR. THIS IS VERY WELL REPRESENTED BY 925MB
TEMPS WHICH FALL TO -10 TO -14C BY 00Z TUESDAY AND -12 TO -14C TO
START OFF CHRISTMAS MORNING. TRENDED BOTH HIGHS AND LOWS COLDER...
CLOSER TO GUIDANCE.

.LONG TERM...CHRISTMAS DAY THROUGH FRIDAY NIGHT
233 AM CST SAT DEC 22 2012

GOOD AGREEMENT CONTINUES FROM YESTERDAY ON THE GENERAL UPPER LEVEL
PATTERN THROUGH THE LONG TERM PERIOD. 22.00Z ECMWF/GFS/CANADIAN AND
UKMET CONTINUE TO SHOW A STRONG TROUGH AND STORM SYSTEM TRACKING
FROM THE SOUTHERN PLAINS ON TUESDAY INTO THE MID-ATLANTIC REGION BY
EARLY THURSDAY. THE FORECAST AREA REMAINS PLENTY FAR AWAY FROM THIS
SYSTEM...KEEPING US IN SUBSIDENCE AND MORE UNDER THE INFLUENCE OF
CANADIAN HIGH PRESSURE. IN FACT...THIS PERIOD FROM CHRISTMAS DAY
THROUGH WEDNESDAY NIGHT LOOKS SEASONABLY COOL...DUE TO 925MB TEMPS
REMAINING BETWEEN -10 AND -14C. WILL REALLY HAVE TO WATCH LOW
TEMPERATURES FOR CLEAR SKIES AND LIGHT WINDS...AS THE SNOW COVER NOW
IN PLACE FAVORS PLUMMETING. HAVE ADJUSTED BOTH HIGH AND LOW
TEMPERATURES DOWNWARD FROM THE PREVIOUS FORECAST ABOUT 5 DEGREES OR
SO...BUT FURTHER LOWERING MAY BE NEEDED...ESPECIALLY WITH LOWS. FOR
THURSDAY ONWARDS...ANOTHER DEEP TROUGH IS PROGGED TO FORM OVER THE
SOUTHWESTERN U.S...BUT THIS ONE GETS EJECTED NORTHEASTWARD TOWARDS
THE FORECAST AREA FOR FRIDAY AND INTO THE WEEKEND. AT THIS POINT
THERE DOES NOT APPEAR TO BE ANY BIG STORM PER SE WITH THIS
TROUGH...BUT SOME WARM ADVECTION SNOW IS SUGGESTED FOR FRIDAY INTO
FRIDAY NIGHT. THUS...30-40 PERCENT CHANCES OF PRECIPITATION ARE IN
THE FORECAST. THE APPROACH OF THE TROUGH SHOULD ALSO HELP TO BRING
WARMER AIR INTO THE FORECAST AREA...AND THIS IS NOTED BY 925MB TEMPS
PROGGED TO CLIMB TO -8 TO -10C AT 00Z FRIDAY AND -6 TO -9C AT 00Z
SATURDAY. FOLLOWED MODEL CONSENSUS FOR HIGHS AND LOWS FROM THURSDAY
ONWARDS...WHICH BRINGS TEMPERATURES BACK UP TO NORMAL FOR FRIDAY.

&&

.AVIATION...TODAY AND TONIGHT
555 AM CST SAT DEC 22 2012

FIRST CONCERN WILL BE STRATUS DECK OVER THE MISSISSIPPI RIVER
CHANNEL AND WHETHER IT WILL AFFECT THE KLSE TAF SITE THIS MORNING.
STRATUS DECK FAIRLY EXPANSIVE ON OUR WEBCAM ATOP THE LA CROSSE
RIDGE AND FEEL IT WILL LIKELY IMPACT KLSE THROUGH 15Z THIS
MORNING WITH TEMPO 3SM BR BKN003 CONDITIONS. OTHERWISE...A WEAK
TROUGH OF LOW PRESSURE WILL DRIFT SOUTHEAST ACROSS THE KRST/KLSE
TAF SITES BY THIS EVENING SHIFTING THE WINDS FROM LIGHT SOUTHERLY
TO A LIGHT NORTHERLY DIRECTION. MODELS ARE INDICATING INCREASING
MOISTURE AHEAD OF THE TROUGH WHICH MAY MANIFEST ITSELF IN
SCATTERED STRATOCUMULUS WITH BASES AROUND 1.5KFT AGL AFTER 19Z.
ONCE THE TROUGH IS THROUGH THIS EVENING WILL HAVE TO WATCH A
NORTHERLY FETCH OFF OF LAKE SUPERIOR WHICH MAY ADVECT SOME MORE
STRATOCUMULUS TOWARD THE TAF SITES DURING THE OVERNIGHT HOURS. HAVE
KEPT SCT015 MENTION IN FOR NOW THROUGH THE NIGHT TO ACCOUNT FOR
THIS. WILL PASS ALONG TO THE DAY SHIFT TO ASSESS FURTHER.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
233 AM CST SAT DEC 22 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...AJ
LONG TERM...AJ
AVIATION...DAS







AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 233 AM CST SAT DEC 22 2012

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
233 AM CST SAT DEC 22 2012

MAIN FORECAST CONCERNS ARE ON LOW CLOUD POTENTIAL TONIGHT INTO
SUNDAY AND POTENTIAL FOR SOME LIGHT SNOW SUNDAY NIGHT INTO MONDAY.

CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED DEEP TROUGHING APPROACHING THE WESTERN U.S. COAST...RIDGING
ACROSS THE PLAINS AND DEEP TROUGHING ALONG THE U.S. EAST COAST. ON
TOP OF THE RIDGE...A SHORTWAVE WAS PRESENT ACROSS CENTRAL PORTIONS
OF SASKATCHEWAN AND MANITOBA. THE FORECAST AREA LIES CLOSER TO THE
INFLECTION POINT BETWEEN THE RIDGE AND EAST COAST TROUGH...YIELDING
HIGH PRESSURE AT THE SURFACE. OTHER THAN SOME SCATTERED HIGH CLOUDS
ASSOCIATED WITH A COMBINATION OF PACIFIC MOISTURE TOPPING THE RIDGE
AND A 100 KT JET NEAR THE TROPOPAUSE...SKIES WERE MOSTLY CLEAR
ACROSS THE FORECAST AREA. DRY AIR AND SUBSIDENCE SEEN ON THE 00Z
ABR...MPX AND DVN SOUNDINGS ARE HELPING TO PRODUCE THE MOSTLY CLEAR
SKIES. WITH LIGHT WINDS UNDER THE SURFACE RIDGE AND THE FRESH SNOW
COVER...TEMPERATURES HAVE MOSTLY FALLEN INTO THE SINGLE DIGITS ABOVE
ZERO. BLACK RIVER FALLS AND SPARTA HAVE EVEN DROPPED BELOW ZERO. TO
THE NORTHWEST...A COLD FRONT WAS LOCATED OVER MANITOBA AND THE
DAKOTAS ASSOCIATED WITH THE SOUTH CENTRAL CANADA SHORTWAVE. LOW
CLOUDS WERE PRESENT ACROSS SOUTH CENTRAL CANADA AS WELL BEHIND THE
FRONT.

TODAY AND TONIGHT...THE SHORTWAVE SEEN OVER SOUTH CENTRAL CANADA IS
PROGGED TO SLIDE SOUTHEAST ACROSS EASTERN LAKE SUPERIOR THIS
EVENING...DRIVING THE COLD FRONT ACROSS THE DAKOTAS THROUGH THE
FORECAST AREA. NO PRECIPITATION IS EXPECTED WITH OR BEHIND THE FRONT
GIVEN THE DRY AIRMASS PRESENT...AS WELL AS ALL THE FORCING LOCATED
WELL NORTHEAST OF THE AREA. MAIN CONCERNS WITH THE FRONT IS THE
WARMING AHEAD OF IT AND IF ANY LOW CLOUDS COME IN BEHIND IT.
REGARDING THE WARMING...GFS/NAM/ECMWF 925MB TEMPERATURE PROGS SHOW
THEM CLIMBING FROM -3 TO -6C CURRENTLY TO -2 TO -4C. WITH SOME SUN
THROUGH HIGH CLOUDS AND A SOUTHWEST BREEZE...TEMPERATURES SHOULD
EASILY CLIMB INTO THE 20S EVERYWHERE. SOME LOCATIONS IN WISCONSIN...
PARTICULARLY IN VALLEY AREAS...COULD EXCEED 30 THANKS TO LOWER
ALBEDO PRESENT. DECENT COLD ADVECTION LOOKS TO OCCUR TONIGHT BEHIND
THE FRONT AS 925MB TEMPS FALL TO -6 TO -10C BY 12Z SUNDAY ON 15-20
KT NORTHERLY BREEZE. CERTAINLY LOOKS GOOD FOR LAKE EFFECT OFF
SUPERIOR WHICH THE BREEZE WOULD THEN SEND THE CLOUDS SOUTHWARD AT
LEAST INTO THE NORTHERN HALF OF WISCONSIN AFTER MIDNIGHT. IN
ADDITION...SOME OF THE LOW CLOUDS IN GENERAL BEHIND THE FRONT COULD
END UP BEING SENT SOUTH. AS A RESULT...HAVE RAISED CLOUD COVER...
ESPECIALLY ACROSS TAYLOR AND CLARK COUNTIES GIVEN THE BETTER CHANCE
OF BEING IMPACTED BY LAKE EFFECT CLOUDS. GIVEN CLOUDS AND THE WINDS
BEHIND THE FRONT...FOLLOWED A BLEND OF GUIDANCE FOR LOWS.

SUNDAY AND SUNDAY NIGHT...FOCUS SHIFTS TO THE TROUGHING APPROACHING
THE WEST COAST. MODELS TAKE A FAIRLY SIGNIFICANT PORTION OF THE
TROUGH CROSSING THE NORTHERN ROCKIES DURING THE NEXT 24 TO 36 HOURS.
THE QUESTION IS WHAT HAPPENS WITH THE TROUGH FROM THERE. THE 22.00Z
NAM/UKMET ARE A WEAKER SCENARIO WITH THE TROUGH...STRETCHING FROM
NORTHEAST SOUTH DAKOTA INTO CENTRAL IOWA BY 12Z MONDAY.
MEANWHILE...THE 22.00Z GFS/CANADIAN DEPICT A MORE POTENT TROUGH THAT
ENDS UP CROSSING NEBRASKA AND BECOMING SITUATED DOWN IN SOUTHERN
IOWA INTO THE ST LOUIS AREA BY 12Z MONDAY. ALL SCENARIOS YIELD AN
INVERTED TROUGH AT THE SURFACE...JUST THE MORE POTENT GFS/CANADIAN
GROUP WOULD HAVE A BETTER SHOT OF YIELDING PRECIPITATION
DEVELOPMENT. GIVEN THE STRENGTH OF THE TROUGH RIGHT NOW OFF THE WEST
COAST...NOTED TOO BY NUMEROUS LIGHTNING STRIKES...WILL FAVOR THE
MORE POTENT GROUP. THIS MEANS 20 PERCENT CHANCES ARE NEEDED AFTER
MIDNIGHT SUNDAY NIGHT WEST OF THE MISSISSIPPI RIVER TO ACCOUNT FOR
THE DPVA AHEAD OF THE POTENT TROUGH...AS WELL AS ISENTROPIC LIFT.
DID NOT GO HIGHER THAN 20 BECAUSE OF INITIAL DRY AIR TO OVERCOME
SINCE THE SNOW THAT DOES FALL WILL COME OUT OF A MID CLOUD DECK.
OTHERWISE...THE ONLY OTHER CONCERN IS CLOUD COVER. THE LOW CLOUDS
OVER NORTHERN WI AT 12Z SUNDAY COULD END UP EXPANDING SOUTHWESTWARD
THROUGH THE DAY...WHILE MID AND HIGH CLOUDS INCREASE DOWNSTREAM OF
THE POTENT TROUGH. THUS AN INCREASING CLOUD TREND SEEMS APPROPRIATE.
THESE CLOUDS PLUS COLDER 925MB TEMPS IN THE -8 TO -10C RANGE WILL
DEFINITELY YIELD A COLDER DAY. ON THE POSITIVE SIDE...THE CLOUDS
SHOULD HELP HOLD TEMPERATURES UP SUNDAY NIGHT.

MONDAY INTO MONDAY NIGHT...FOLLOWING THE MORE POTENT TROUGH LOOK AS
MENTIONED IN THE SUNDAY/SUNDAY NIGHT DISCUSSION...THE GFS AND
CANADIAN SEND THE TROUGH SOUTHEAST INTO OHIO BY 00Z TUESDAY. CHANCES
OF SNOW STILL LOOK APPROPRIATE FOR MONDAY WITH ISENTROPIC LIFT AND
DPVA PERSISTING...THOUGH THIS SHOULD BE DIMINISHING IN THE AFTERNOON
AS THE TROUGH SHIFTS EAST AND CANADIAN HIGH PRESSURE BUILDS SOUTH
INTO THE DAKOTAS IN ITS WAKE. AS SUCH...MONDAY NIGHT IS LIKELY TO
END UP DRY. REGARDING THE ACTUAL CHANCES...LINGERING LOWER LEVEL DRY
AIR IS A BIG CONCERN...AS WELL AS THE TRACK OF THE TROUGH DROPPING
MORE TO OUR SOUTH. AS A RESULT...KEPT CHANCES IN A 20-30 RANGE.
LOOKS GOOD FOR MOST OF THE AREA TO PICK UP A LITTLE SNOW...BE IT
ACTUAL ACCUMULATING SNOW OR FLURRIES...SO USED OCCASIONAL VERY LIGHT
SNOW VERBIAGE. GIVEN CANADIAN HIGH PRESSURE BUILDING SOUTH...ONE CAN
EXPECT COLDER LOW LEVEL AIR. THIS IS VERY WELL REPRESENTED BY 925MB
TEMPS WHICH FALL TO -10 TO -14C BY 00Z TUESDAY AND -12 TO -14C TO
START OFF CHRISTMAS MORNING. TRENDED BOTH HIGHS AND LOWS COLDER...
CLOSER TO GUIDANCE.

.LONG TERM...CHRISTMAS DAY THROUGH FRIDAY NIGHT
233 AM CST SAT DEC 22 2012

GOOD AGREEMENT CONTINUES FROM YESTERDAY ON THE GENERAL UPPER LEVEL
PATTERN THROUGH THE LONG TERM PERIOD. 22.00Z ECMWF/GFS/CANADIAN AND
UKMET CONTINUE TO SHOW A STRONG TROUGH AND STORM SYSTEM TRACKING
FROM THE SOUTHERN PLAINS ON TUESDAY INTO THE MID-ATLANTIC REGION BY
EARLY THURSDAY. THE FORECAST AREA REMAINS PLENTY FAR AWAY FROM THIS
SYSTEM...KEEPING US IN SUBSIDENCE AND MORE UNDER THE INFLUENCE OF
CANADIAN HIGH PRESSURE. IN FACT...THIS PERIOD FROM CHRISTMAS DAY
THROUGH WEDNESDAY NIGHT LOOKS SEASONABLY COOL...DUE TO 925MB TEMPS
REMAINING BETWEEN -10 AND -14C. WILL REALLY HAVE TO WATCH LOW
TEMPERATURES FOR CLEAR SKIES AND LIGHT WINDS...AS THE SNOW COVER NOW
IN PLACE FAVORS PLUMMETING. HAVE ADJUSTED BOTH HIGH AND LOW
TEMPERATURES DOWNWARD FROM THE PREVIOUS FORECAST ABOUT 5 DEGREES OR
SO...BUT FURTHER LOWERING MAY BE NEEDED...ESPECIALLY WITH LOWS. FOR
THURSDAY ONWARDS...ANOTHER DEEP TROUGH IS PROGGED TO FORM OVER THE
SOUTHWESTERN U.S...BUT THIS ONE GETS EJECTED NORTHEASTWARD TOWARDS
THE FORECAST AREA FOR FRIDAY AND INTO THE WEEKEND. AT THIS POINT
THERE DOES NOT APPEAR TO BE ANY BIG STORM PER SE WITH THIS
TROUGH...BUT SOME WARM ADVECTION SNOW IS SUGGESTED FOR FRIDAY INTO
FRIDAY NIGHT. THUS...30-40 PERCENT CHANCES OF PRECIPITATION ARE IN
THE FORECAST. THE APPROACH OF THE TROUGH SHOULD ALSO HELP TO BRING
WARMER AIR INTO THE FORECAST AREA...AND THIS IS NOTED BY 925MB TEMPS
PROGGED TO CLIMB TO -8 TO -10C AT 00Z FRIDAY AND -6 TO -9C AT 00Z
SATURDAY. FOLLOWED MODEL CONSENSUS FOR HIGHS AND LOWS FROM THURSDAY
ONWARDS...WHICH BRINGS TEMPERATURES BACK UP TO NORMAL FOR FRIDAY.

&&

.AVIATION...
1100 PM CST FRI DEC 21 2012

HIGH PRESSURE WILL CONTINUE TO BUILD ACROSS THE REGION...RESULTING
IN LIGHT WINDS AND MOSTLY CLEAR/PARTLY CLOUDY SKIES THROUGH
SATURDAY. SOME HIGH CLOUDS WILL SPILL ACROSS AN UPPER LEVEL RIDGE...
BUT WON/T HAVE AN AVIATION IMPACT. WINDS WILL BECOME MORE SOUTHERLY
ON SAT AS THE HIGH SLIDES OFF TO THE EAST...GRADUALLY BECOMING
NORTHERLY SATURDAY NIGHT.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
233 AM CST SAT DEC 22 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RIECK









AREA FORECAST DISCUSSION

NWS NORTHERN INDIANA

 100 AM EST MON DEC 24 2012

.AVIATION... /06 UTC TAFS/
WEAK FRONTAL SYSTEM TO EJECT FM CNTL ARKANSAS THROUGH THE OHIO
VALLEY TODAY...AND INTO SERN OHIO BY MON EVENING. WEAK
FORCING/MOISTURE PROFILES TO PRECLUDE SIG PRECIP ACCUM.
HOWEVER...ANTICIPATE CIGS TO LWR TO BLO FUEL ALT BY MID AFTERNOON.
BEST LLVL MOISTURE FOR RAIN...POSSIBLY MIXED WITH SNOW ACRS NERN
IN/KFWA...WITH CIGS LKLY CONTG TO DETERIORATE INTO IFR RANGE AS
COLDER AIR DEEPENS IN WAKE OF SYSTEM THIS EVENING. NEAR
KSBN...AMOUNT OF LIFT MAY PROVE TOO WEAK FOR PRECIP DEVELOPMENT...
THOUGH PROFILES TO SUPPORT LIGHT FROZEN PRECIP SHOULD IT
EXTEND/DEVELOP FARTHER NW.

&&

.PREV DISCUSSION... /ISSUED 338 PM EST SUN DEC 23 2012/

SHORT TERM.../TONIGHT THROUGH MONDAY NIGHT/

LATEST SFC ANALYSIS HAS WEAK FRONTAL BOUNDARY JUST TO THE SOUTH
OF THE CWA EXTENDING BACK TO DEVELOPING FRONTAL WAVE IN EASTERN
OKLAHOMA. WATER VAPOR IMAGERY ALONG WITH LATEST RAP ANALYSIS
DEPICTING SPLIT FLOW PATTERN ACROSS THE EASTERN TWO THIRDS OF THE
CONUS...EACH WITH THEIR OWN WEAK DISTURBANCE THAT WILL MOVE ACROSS
THE REGION ON MONDAY. NORTHERN STREAM SHORT WAVE CURRENTLY MOVING
THROUGH THE DAKOTAS IS EXPECTED TO CONTINUE EASTWARD INTO THE
GREAT LAKES REGION WHILE SOUTHERN STREAM SHORT WAVE WILL MOVE INTO
THE TN VALLEY. MODEL TRENDS HAVE CONTINUED TOWARD A LACK OF
PHASING WITH THESE DISTURBANCES...RESULTING IN CONCERN OVER
FORCING AND AVAILABLE MOISTURE WITH PRECIP CHANCES MONDAY.
CONSENSUS FAVORS A SPLIT OVER OUR CWA IN BOTH MOISTURE AND
DYNAMICS AS WEAKER SOUTHERN STREAM MOVES QUICKLY INTO EAST TN BY
MONDAY AFTERNOON WHILE NORTHERN STREAM WAVE DIGS INTO THE CENTRAL
GREAT LAKES REGION AND WILL PROVIDE SOME DECENT FORCING IN OUR NE
CWA WITH 500MB HT FALLS OF 60-80M POSSIBLE. PROBLEM IS THAT BEST
MOISTURE WILL BE CONFINED TO THE NORTH. HAVE THEREFORE OPTED TO
KEEP POPS IN HIGH CHANCE RANGE IN EASTERN THIRD OF CWA WHERE BEST
CHANCE FOR PRECIP WILL MATERIALIZE. PRECIP TYPE WILL ALSO COME
INTO PLAY FOR THE E/SE CWA AS TEMPS EXPECTED TO REACH THE MID 30S
AND TIMING OF SYSTEM HAS BEST CHANCE FOR PRECIP AT MAX HEATING.
THIS WILL ALL ACT TO HOLD ANY ACCUMULATING SNOW IN CHECK WITH LESS
THAN AN INCH OVER THE NORTHERN CWA. SYSTEM QUICKLY EXITS THE
REGION MONDAY NIGHT...MAY GET CLIPPED WITH BRIEF LAKE EFFECT IN
ITS WAKE IN FAR NW CORNER BEFORE FLOW BECOMES MORE NE AND SHIFTS ANY
BANDS WEST OF THE AREA.

LONG TERM.../TUESDAY THROUGH SATURDAY/

FOCUS OF THE EXTENDED FORECAST WILL BE ON THE POTENTIAL OF SNOWFALL
ACROSS THE AREA WEDNESDAY.

FORECAST PERIOD BEGINS TUESDAY WILL QUASI ZONAL FLOW ACROSS GREAT
LAKES REGION IN ADVANCE OF SHARPENING H5 TROF AND DEEPENING SFC LOW
ACROSS WRN TX. RAISED HI TEMPS ACROSS THE SOUTHERN 3/4THS OF THE
AREA TUESDAY SLIGHTLY...AND RAISED LOWS SLIGHTLY ON TUESDAY
NIGHT...OTHERWISE NO MAJOR CHANGES TO FORECAST. H5 CUT OFF LOW WILL
DEVELOP OVER ARKLATEX REGION LATE TUESDAY AS UPPER TROF BECOMES
NEGATIVELY TILTED AND EJECTS NORTHEASTWARD THROUGH THE MID
MISSISSIPPI VALLEY INTO THE OHIO VALLEY BY WEDNESDAY. THE EXACT
TRACK OF THE SYSTEM WILL HAVE HUGE IMPLICATIONS FOR SNOWFALL AMOUNTS
ACROSS OUR AREA.

DECENT SPREAD BETWEEN DIFFERENT MODEL SYSTEM TRACKS...NOT TO BE
UNEXPECTED 72+ HOURS OUT. 12Z NAM AND 09Z/15Z SREF ARE FURTHEST NW
W/ SFC LOW TRACK INVOF CINCINNATI...WHILE THE 00Z/12Z ECMWF IS
FURTHER SE WITH A JACKSON KY TO CHARLESTON WV SFC LOW TRACK. THE 12Z
GFS/GEFS IS A NICE COMPROMISE AMONG THE SOLUTIONS...WITH A FRANKFORT
KY TO CHILLICOTHE OH TRACK. OVERALL...RECENT MODEL TRENDS HAVE
SUBTLY SHIFTED THE SYSTEM TRACK NW WITH A SLIGHTLY SLOWER
SOLUTION...WHICH IS NOT UNCOMMON WITH NEGATIVELY TILTED PANHANDLE
HOOK TYPE SYSTEMS.

A LEAN TOWARD A 12Z GFS/GEFS LOW TRACK WOULD BRING THE POTENTIAL FOR
SIGNIFICANT SNOWFALL ACROSS A PORTION OF THE AREA...WITH BROAD
SATURATED ASCENT IN THE NW QUADRANT OF THE SYSTEM. THERMAL PROFILES
WOULD BE CONDUCIVE FOR ALL SNOW WITH THE ONSET OF THE SYSTEM FOR THE
DURATION OF THE EVENT. HOWEVER...A FURTHER NW SOLUTION OR STRONGER
SYSTEM COULD WRAP WARMER AIR INTO SE PORTIONS OF THE AREA AND IN
TURN MIXED PRECIPITATION POTENTIAL. THERE IS ALSO SOME EVIDENCE FOR
HEAVIER BANDED PRECIPITATION ACROSS A PORTION OF THE AREA. STRONG
H75-H6 FRONTOGENESIS...WITH NEAR ZERO OR NEGATIVE EPV ALOFT...AND
STRONG OMEGA IMPINGING ON THE DGZ WOULD SUGGEST INGREDIENTS FOR A
POSSIBLE BAND OF HEAVY SNOWFALL...HOWEVER GIVEN UNCERTAINTIES THIS
FAR OUT...CAN NOT RESOLVE THIS IN THE FORECAST AT THIS TIME. INITIAL
THINKING IS THAT A WIDESPREAD 2-4" EVENT...WITH LOWEST AMOUNTS
WEST/NW...WITH THE POTENTIAL FOR A NARROW BAND OF 4-6" WITH LOCALLY
HIGHER AMOUNTS SOMEWHERE ACROSS THE CENTRAL TO EASTERN/SOUTHEASTERN
PORTION OF THE AREA. CONTEMPLATED A WINTER STORM WATCH WITH THIS
FCST ISSUANCE...BUT DECIDED TO DEFER TO THE NEXT SHIFT TO CAPTURE
LATEST MODEL TRENDS AND POTENTIAL INCREASED CONFIDENCE.

FORECAST WISE...INCREASED POPS WEST/NWWARD WITH GIVEN MODEL
SOLUTIONS LATE TUESDAY NIGHT THROUGH WEDNESDAY...WITH A PERIOD OF
CAT POPS FAR SE WEDNESDAY. LEFT EXPECTED PTYPE ALL SNOW AT THIS
JUNCTURE GIVEN PREFERRED MODEL SOLUTION/TRACK/INTENSITY.

SYSTEM WILL EXIT THE REGION WEDNESDAY NIGHT INTO THURSDAY. SOME
POTENTIAL FOR LIGHT LAKE EFFECT SNOW THURSDAY INTO THURSDAY NIGHT
ACROSS FAR NW PORTIONS OF THE AREA WITH NORTHERLY FLOW IN THE WAKE
OF THIS SYSTEM. OTHERWISE CONDITIONS WILL BE DRY WITH COOLER
TEMPS...ESPECIALLY EAST WITH EXPECTED FRESH SNOWPACK. LOWS THURSDAY
NIGHT COULD DROP INTO THE LOWER TEENS EAST.

NEXT SYSTEM OF INTEREST WILL ARRIVE FRIDAY NIGHT INTO SATURDAY.
ECMWF AND GFS DISAGREE WITH THE OVERALL EVOLUTION OF THE
SYSTEM...BUT BOTH HAVE THE GENERAL IDEA AND IMPACT ON OUR AREA.
ECMWF SEPARATES THE NORTHERN AND SOUTHERN STREAM ENERGY...ALLOWING
FOR SHARPENING TROUGH AND LEE CYCLOGENESIS...SIMILAR TO MIDWEEK
PANHANDLE HOOK SYSTEM. GFS HOWEVER COMBINES BOTH NORTHERN AND
SOUTHERN STREAM ENERGY WITH BROAD UPPER TROF OVER ERN CONUS AND MORE
SUBTLE SHORTWAVE. NEVERTHELESS...TEMPERATURE PROFILES SUPPORT AN ALL
SNOW TYPE EVENT.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SHORT TERM...JAL
LONG TERM...NG
AVIATION...MURPHY






AREA FORECAST DISCUSSION

NWS PITTSBURGH PA

 237 AM EST MON DEC 24 2012

.SYNOPSIS...
A WEAK SURFACE LOW WILL PUSH ACROSS THE AREA TODAY...BRINGING A
LIGHT WINTRY MIX OF PRECIPITATION ACROSS THE RIDGES AND NORTH OF
PITTSBURGH WITH MOSTLY RAIN ELSEWHERE. WEAK HIGH PRESSURE WILL PASS
NORTHWEST OF THE AREA AND ALLOW FOR A MOSTLY DRY CHRISTMAS DAY. THE
NEXT LOW WILL THE BRING A WINTRY MIX ACROSS THE AREA WEDNESDAY INTO
THURSDAY.

&&

.NEAR TERM /THROUGH TODAY/...
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A PAIR OF SHORT WAVES
UPSTREAM ALONG THE SAME AXIS OF A BROAD UPPER TROUGH. THE NORTHERN
WAVE IS THE STRONGER OF THE TWO AND IS DIVING SOUTHEASTWARD FROM THE
NORTHERN PLAINS INTO THE UPPER MIDWEST. THE SOUTHERN WAVE IS MOVING
ACROSS THE ARKLATEX REGION. IN THE LOWER LEVELS...850MB FLOW IS
SHIFTING TO MORE SOUTHWESTERLY AHEAD OF A TROUGH THAT EXTENDS FROM
LAKE MICHIGAN ACROSS THE TENNESSEE VALLEY. WEAK WAA AHEAD OF THIS
FEATURE HAS INITIATED...WITH 850 TEMPS AT -1C TO 1C ACROSS THE AREA
AND A WARMER TEMPS AT 2-3C SURGING NORTHWARD INTO SOUTHERN WV. AT
THE SURFACE...A 1009MB LOW IS MOVING INTO WESTERN TN WITH A FRONTAL
BOUNDARY EXTENDING NORTHEAST OF THIS FEATURE INTO SOUTHERN OHIO AND
BECOMING MORE WASHED OUT INTO SW PA.

TODAY...THE SURFACE LOW WILL LIFT NORTHEASTWARD INTO THE OHIO
VALLEY AND PHASE WITH THE NORTHERN SHORT WAVE TROUGH AS IT REACHES
WESTERN PA AROUND 00Z TUESDAY. WEAK FORCING FROM 285-300K LAYER
ISENTROPIC LIFT...MID-LEVEL SHORT WAVE ENERGY AND THE LOW WILL BE
SUFFICIENT FOR SHOWERS TO BEGIN PUSHING IN FROM THE SOUTHWEST AROUND
15Z AND CONTINUING THROUGH MUCH OF THE DAY. A MODEL CONSENSUS
INDICATES GENERALLY A FEW HUNDREDTHS TO A TENTH OF AN INCH OF PRECIP
SOUTHWEST OF PITTSBURGH BEFORE 18Z AND THEN AN ADDITIONAL TENTH OF
AN INCH ACROSS THE AREA THROUGH 00Z. THUS...ONLY HAVE A TENTH TO A
QUARTER OF AN INCH FORECAST FOR QPF TODAY. FOR TEMPS...HAVE GONE
WITH THE WARMER NAM SOLUTION SOUTH OF PITTSBURGH AND LAMP GUIDANCE
ELSEWHERE.

FOR PRECIP TYPE TODAY...GFS/NAM/ECMWF ARE ALL IN AGREEMENT IN THE
LOW REMAINING RELATIVELY WEAK AS IT TRACKS ALONG THE OHIO RIVER.
DESPITE MODEL SIMILARITIES IN SURFACE LOW TRACK AND INTENSITY WITH
THIS INITIAL LOW...SOUNDINGS INDICATE VARYING THERMAL
PROFILES...MAKING FOR A CHALLENGING PRECIP TYPE FORECAST TODAY.

THE BEGINNING OF PRECIP HAS TRENDED SLOWER...WHICH HAS FAVORED
SURFACE TEMPS WARMING ENOUGH THIS MORNING FOR MOSTLY RAIN IN
EASTERN OHIO AND NORTHERN WV. THE EXCEPTION WOULD BE ACROSS THE
EASTERN RIDGES...WHERE COLD AIR DAMMING WILL KEEP TEMPS BELOW
FREEZING AND THUS ALLOW FOR LIGHT FREEZING RAIN AND LIGHT ICE
ACCUMULATION. 00Z THERMAL PROFILES SUPPORT MORE OF A MIX OF SLEET
AND SNOW WITH FREEZING RAIN ACROSS THE RIDGES. ALONG THE I-80
CORRIDOR...PRECIP IS FORECAST TO REMAIN MOSTLY SNOW AS DENDRITIC
GROWTH ZONE BECOMES SATURATED AND MELTING LAYER IS TOO WEAK. ANY
ICE ACCUMULATION ACROSS THE RIDGES WILL BE LIGHT...LESS THAN A
TENTH OF AN INCH. SNOW AND SLEET MAY MIX IN FOR LESS THAN AN INCH
OF ADDITIONAL ACCUMULATION FOR THE RIDGES. PRIMARILY NORTH OF
I-80...1-2 INCHES OF SNOW ACCUMULATION IS FORECAST.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
PER RECENT SREF MODEL OUTPUT...CONTINUED MENTION OF PRECIPITATION
TONIGHT...CHRISTMAS EVE...AS PASSING LOW PRESSURE CENTER WILL
NOT EXIT NORTHEAST UNTIL LATE MONDAY NIGHT.

PRECIPITATION TYPE WILL VARY FROM RAIN MOST PLACES TO LIGHT SNOW
ACROSS THE I-80 CORRIDOR AND LINGERING PATCHES OF LIGHT FREEZING
DRIZZLE OR DRIZZLE FOR THE HIGHER WV-MD MOUNTAINS. SREF MODEL PROFILES
SUGGEST DRYING ALOFT CAN LEAD TO THE LIGHT PRECIPITATION BECOMING
LITTLE MORE THAN A LIGHT DRIZZLE BY MIDNIGHT...UNLESS SEEDER
FEEDER MECHANISMS COME INTO PLAY. WHERE SURFACE TEMPERATURES SLIP
BELOW FREEZING...THIS COULD BE LIGHT FREEZING DRIZZLE.

SREF MODEL OUTPUT SHOWS A DRY BREAK FOR CHRISTMAS DAY DUE TO
PASSING HIGH PRESSURE.

LOWS CHRISTMAS MORNING WILL BE NEAR OR SLIGHTLY COLDER THAN
FREEZING. HIGHS CHRISTMAS AFTERNOON CAN BE NEAR OR SLIGHTLY WARMER
THAN NORMAL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
DEVELOPING LOW PRES WL MOVE NE FM THE MS VLY RGN TUE NT...BRINGING A MIX
OF PCPN TO THE AREA LATE TUE NT THRU WED. STILL CONSIDERABLE
UNCERTAINTY IN THE DETAILS OF THIS SYSTEM. REGENERATION OF THE LOW
IS EXPECTED OVR NRN VA WED EVE. NAM DELAYS THIS REGENERATION
PROCESS...WHICH RESULTS IN WARMER AIR WRAPPED INTO THE SYSTEM WED.
BELIEVE NAM IS TAKING TOO LONG TO DEPICT THIS TRANSITION GIVEN
VERTICAL STACKING OF SFC AND UL LOWS ERLY WED...SO LEANED CLOSER TO
SREFS AND GFS FOR FCST DETAILS.

THIS RESULTS IN A WINTRY MIX OF FZRA...RAIN...SLEET AND SNOW WED
INTO WED EVE. CRITICAL THICKNESSES AND SOUNDING PROFILES INDICATE
MUCH OF THE PCPN WL CHG TO RAIN FOR AREAS FM PIT SWD. EXPECT MORE
SNOW INITIALLY N OF PIT...EVENTUALLY MIXING WITH SLEET/RAIN/FZRA.
WL MONITOR FOR CHANGING DETAILS NEXT COUPLE OF DAYS.
OTRW...COLDER AIR MOVING IN BEHIND THE LOW WED NT-THU WL RESULT
IN SNOW SHOWERS...WITH SOME ACCUMULATION LIKELY ESP IN LK ENHANCED
AND HIGHER TERRAIN AREAS. BLEND OF GEFS/NAEFS/HPC CHARTS DEPICT A
SFC LOW MOVG ACRS THE OH VLY SAT...WITH AN UL TROF FOR SUN. A CHC
OF SNOW SHOWERS RETURNS FOR THESE SYSTEMS. OVERALL TEMPS EXPD TO
AVG BLW NORMAL THRU THE PD.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
THICKENING HIGH CLOUDS WILL QUICKLY BE REPLACED BY LOW MVFR CIGS
ON MONDAY AFTERNOON. A RATHER DISJOINTED AREA OF DISTURBED WEATHER
WILL MOVE ACROSS THE AREA...WITH THE SOUTHERN TERMINALS FALLING
INTO A WARMER REGIME THAN THE NORTHERN TERMINALS. AS SUCH...LIGHT
RAIN WILL TRANSITION TO DRIZZLE TOMORROW NIGHT IN THE
SOUTH...WHILE LIGHT SNOW WILL END AS A PERIOD OF DRIZZLE OR
FREEZING DRIZZLE TO THE NORTH. IFR CONDITIONS ARE HIGHLY LIKELY
WITH THE PASSAGE OF THE SYSTEM AS LOW LEVEL MOISTURE SEEMS LIKELY
TO LINGER WELL BEYOND SIGNIFICANT PRECIPITATION.

.OUTLOOK.../MONDAY NIGHT THROUGH FRIDAY/...
LIGHT RAIN AND SNOW TAPERING OFF MONDAY NIGHT INTO TUESDAY MORNING
COULD BRIEFLY CAUSE MVFR CONDITIONS BEFORE VFR RETURNS FOR THE
REST OF CHRISTMAS DAY.

ANOTHER LOW PRESSURE SYSTEM APPROACHING FROM THE SOUTHWEST ON
WEDNESDAY WITH MIXED PRECIPITATION WILL CAUSE IFR CONDITIONS
THROUGH THURSDAY BEFORE VFR CONDITIONS RETURN ON FRIDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FREEZING RAIN ADVISORY FROM 8 AM THIS MORNING TO 6 PM EST THIS
     EVENING FOR MDZ001.
OH...NONE.
PA...NONE.
WV...FREEZING RAIN ADVISORY FROM 8 AM THIS MORNING TO 6 PM EST THIS
     EVENING FOR WVZ041.

&&

$$

SYNOPSIS...WOODRUM
NEAR TERM...WOODRUM







AREA FORECAST DISCUSSION

NWS WAKEFIELD VA

 136 AM EST MON DEC 24 2012

.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTHEAST ACROSS THE MID ATLANTIC STATES
CHRISTMAS EVE...WITH HIGH PRESSURE REBUILDING OVER THE AREA FOR
CHRISTMAS DAY. A STRONGER AREA OF LOW PRESSURE TRACKS THROUGH THE
TENNESSEE VALLEY CHRISTMAS NIGHT...THEN CONTINUES ACROSS THE MID
ATLANTIC ON WEDNESDAY...WITH ITS ASSOCIATED COLD FRONT PUSHING
OFF THE COAST EARLY THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LATEST WX ANALYSIS REVEALS BROAD AREA OF SFC HIGH PRESSURE, THE
CENTER OF WHICH WAS ORIENTED ALONG THE ATLANTIC COAST OF FLORIDA
AND OFF THE SOUTHEAST COAST. ALOFT, UA ANALYSIS SHOWS QUASI-ZONAL
FLOW CONTINUES ACROSS THE EASTERN 2/3 OF THE COUNTRY. FAST FLOW
ALOFT HAS ALLOWED FOR QUICK INCREASE OF MID TO HIGH LEVEL
CLOUDINESS AHEAD OF A DISTURBANCE ACROSS GA AND UPSTATE SC THIS
EVE, WITH INCREASING CLOUDS OVER THE SOUTHERN HALF OF THE FORECAST
AREA. FARTHER NORTH, CLEAR/MCLEAR SKY PERSISTS OVER FAR NORTHERN
TIER OF CWA. THIS CLEARING IS ALLOWING FOR BETTER RADIATING
CONDITIONS AND SIGNIFICANTLY COOLER CONDITIONS OVER THE LWR
EASTERN SHORE AND FARTHER NORTH INTO THE NORTH MID-ATLANTIC.

RADAR MOSAIC SHOWING SOME VERY LIGHT RETURNS OVER WESTERN
CAROLINAS IN ASSOCIATION WITH SOME WEAK FORCING AHEAD OF THE
SYSTEM. HOWEVER, ANTECEDENT DRY LLVL AIRMASS, AND DOWNSLOPE (WEST)
FLOW ALOFT, IS NOT ALLOWING MUCH OF THIS ACTIVITY TO REACH THE
GROUND THUS FAR. RUC SEEMS TO BE HANDLING THIS SLOWER ONSET OF
POPS WELL OVER OUR REGION, AND HAVE LEANED ON ITS GUIDANCE
OVERNIGHT. SINCE ACCUMULATING PCPN APPEARS RATHER UNLIKELY
OVERNIGHT, HV REMOVED MENTION OF POPS BEFORE 12Z/7AM MONDAY, BUT
NOT OUT OF THE QUESTION TO SEE A FEW SPRINKLES ACROSS THE PIEDMONT
NEAR DAWN MONDAY MORNING. ALL MINIMA ACROSS THIS AREA WILL BE
ABOVE FREEZING AND MDL THERMAL PROFILES RMN WARM ENOUGH TO
PRECLUDE ANY PRECIP TYPE ISSUES OVER THE LOCAL AREA WITH ANY LGT
PCPN THAT OCCURS. EARLY MORNING LOW TEMPS TO RANGE FROM U20S/NR 30
ACROSS THE EASTERN SHORE TO U30S/NR 40 ACROSS SE VA/NE NC.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/...
LO PRES CONTS TO MOVE TO THE NE TWD/INTO NEW ENG MON AFTN/NGT.
ASSOCIATED MSTR AXIS TO SWING (W-E) ACRS THE FA DURG MON...W/
HIGHEST POPS (60-70%) NW PORTION OF FA...TAPERING TO TO 25-30%
XTRM SE VA/CSTL NE NC. QUITE THE TEMP GRADIENT XPCD ON MON...W/ HI
TEMPS FM THE L/M40S FAR NW...TO THE M/U50S SE. DRYING OUT QUICKLY
FM SW TO NE MON NGT...LEADING TO DRY WX ON TUE W/ TEMPS AVGG A
FEW DEGS F ABV NRML (TOPPING OUT IN THE L/M50S).

NEXT STRONGER LO PRES SYS WILL BE DVLPG INVOF W/CNTRL GULF STATES
LT TUE INTO TUE NGT...THEN IS FCST TO TRACK TO THE NE INTO THE ERN
OH VLY BY WED AFTN. MDLS CONT TO TREND WARMER AND HAVE PARENT LO W
OF THE MTNS (ON ITS WAY NE). WRMFNT TO LIFT N INTO/THROUGH THE FA ON
WED AIDED BY INCRSG SE THEN S WNDS. MAIN AREA OF MID LVL DYNAMICS
TO REACH THE FA WED AFTN AS RIBBON OF HIGHER SFC DEWPTS/LLVL
INSTABILITY WOULD BE SURGING NWD. THEREFORE...THOUGH IT BEING LT
DEC...CONCERN IS FOR PSBL CNVTN AND PD OF MDT/HVY RA AHD OF/WITH
CDFNT TO THE AREA DURG WED AFTN. WILL (STRNG) T PTNTL BE INCRSD BY
TRIPLE POINT LO MOVING NNE OVR THE PIEDMONT? FOR NOW...WILL HAVE
80% POPS...AND INCLUDE CHC T FOR SRN HALF OF VA/NE NC (WED AFTN).
HI TEMPS WED FM THE U40S/ARND 50F NW (WELL INLAND)...TO THE U60S/ARND
70F IN XTRM SE VA/CSTL NE NC.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
DECENT MODEL AGREEMENT WED NIGHT WITH A QUICK COLD FRONTAL PASSAGE
AS DEEPENING LOW PRESSURE QUICKLY MOVES NORTHEAST OF THE REGION.
KEPT CHC EVE POPS AHEAD OF FROPA. CAA KICKS IN ALLOWING DRY SLOT TO
PUNCH NE AND CUT PCPN OFF AFTR MIDNITE. LOWS IN THE 30S.

THURSDAY APPEARS TO BE ANOTHER DAY LIKE SATURDAY WAS. STRNG PRS
GRDNT ARND DEPARTING LOW RESULTS IN A BREEZY/WINDY DAY WITH PTNTL
FOR GUSTS OVER 30 MPH INLAND AND GALE FORCE WINDS OVER THE WATERS.
PT SUNNY AS COLD AIR ALOFT RESULTS IN SC DVLPMNT DRNG THE DAY. KEPT
IT DRY WITH HIGHS IN THE 40S TO L50S SERN CNTYS.

HIGH PRS BUILDS INTO THE AREA THURS NITE & FRI. THIS KEEPS IT DRY
WITH DMNSHG WINDS. LOWS THURS NITE M20S-L30S. HIGHS FRI IN THE 40S.

MODELS THEN DIVERGE BY NEXT WEEKEND AS YET ANTHR (WEAKER) SYSTM
EJECTS OUT OF SW THEN MOVES ACROSS THE SRN CONUS. ECMWF QUICKER IN
BRINGING PCPN IN FRI NITE WITH THE GFS GIVING THE REGION THE OLD
SPLIT IN PCPN BATCHES SAT. WILL KEEP LOW CHC (LIQUID) POPS IN FOR
SAT. SOME P-TYPE ISSUES ARE PSBL IF PCPN COMES IN A BIT FASTER FRI
NITE. LOWS FRI NITE U20S-M30S. HIGHS SAT IN THE 40S AND 50S. COLDER
BEHIND SYSTM SUNDAY. LOWS SAT NITE M20S-M30S. HIGHS SUN IN THE
40S.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
MID AND HIGH LEVEL CLOUDS WILL CONTINUE TO INCREASE EARLY THIS
MORNING...AS LIGHT WSW WINDS SHIFT TO THE NE BETWEEN 10-12Z. WEAK LOW
PRESSURE MOVES FROM THE TENNESSEE AND OHIO VALLEYS AND TURNS
WINDS TO THE SE OR S LATER THIS AFTN/EVENING. WILL CARRY -RA IN
THE TAFS AT SOME PT TODAY (EARLIEST AT KRIC). THE RAIN IS
EXPECTED TO BE LIGHT AND VSBYS/CIGS LOOK TO DROP TO MVFR RANGE AT
WORST. THERE COULD BE A FEW HRS OF IFR CIGS/ < 1 K FT TONIGHT
BETWEEN 03-09Z/25 IN LIGHT SW FLOW AND LINGERING LOW LEVEL MOISTURE.

OTHERWISE SKIES CLEAR OUT FOR CHRISTMAS MORNING W/ VFR CONDITIONS
PREVAILING UNTIL A MORE SIGNIFICANT WEATHER SYSTEM BEGINS TO AFFECT
THE REGION LATE TUE NIGHT THRU WED WITH A FAIRLY LONG PERIOD OF
RAIN AND LOWS CIGS/VSBYS LIKELY AT KRIC/SBY (MORE VARIABLE
CONDITIONS POSSIBLE FOR KPHF/KORF/KECG WITH PRECIP BECOMING MORE
SHOWERY). BREEZY E/SE FLOW WED AFTN GRADUALLY TURNS SSW LATE WED
NIGHT INTO THURSDAY MORNING.

&&

.MARINE...
SW WINDS 10-15 KNOTS SHOULD SLOWLY TURN TO THE NNE BEFORE 12Z AS A
WEAK COLD FRONT APPROACHES AND THEN MOVES THROUGH DURING THE EARLY
MORNING HOURS. A BRIEF SURGE DOWN THE BAY (FROM THE NORTH) PSBL
FOLLOWING THE FRONTAL PASSAGE DURING THE PREDAWN HOURS...EXPECT
THIS TO REMAIN AOB 15 KTS. VRBL WIND FLOW AOB 15 KTS SETS UP MON
AND TUES AS NEXT SYSTEM MOVES ACROSS THE AREA.

NEXT STRONGER SYSTEM PROGGED TO MOVE ACROSS THE RGN BY MID WEEK.
INCRSG E-SE FLOW AHEAD OF IT WILL LIKELY RESULT IN SCA HEADLINES
BEGINNING WED. STRONG CAA BEHIND A COLD FRONT RESULTS IN A STRONG
SCA WED NITE AND THURS WITH POTENTIAL FOR GALE FORCE GUSTS THURS.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...ALB/MAM
NEAR TERM...ALB/MAM
SHORT TERM...ALB
LONG TERM...MPR
AVIATION...LKB
MARINE...MPR







AREA FORECAST DISCUSSION

NWS WILMINGTON OH

 134 AM EST MON DEC 24 2012

.SYNOPSIS...
WEAK LOW PRESSURE TRAVELING THROUGH KENTUCKY AND SOUTHEAST OHIO
WILL BRING AN AREA OF PRECIPITATION LATE TONIGHT THROUGH MONDAY.
WEAK HIGH PRESSURE WILL RESULT IN DRY WEATHER ON CHRISTMAS DAY. A
VIGOROUS LOW PRESSURE SYSTEM IS EXPECTED TO DUMP A WINTRY MIX OF
PRECIPITATION OVER THE REGION ON WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LOW PRESSURE OVER NW ARKANSAS WILL MOVE NORTHEAST TO WESTERN
KENTUCKY BY MORNING. LATEST NAM...RAP AND HRRR INDICATE THAT THE
BEST WARM...MOIST ASCENT/ISENTROPIC LIFT WILL OCCUR ALONG AND
SOUTH OF THE OHIO RIVER LATE. THIS MOIST FLOW WILL CAUSE LOW LEVEL
CLOUDS TO INCREASE FROM SOUTH TO NORTH OVERNIGHT WITH CLOUDY SKIES
EXPECTED ALONG AND SOUTH OF THE OHIO RIVER BY MORNING. THERE HAS
BEEN A CONCERN ON HOW FAST PRECIPITATION WILL MOVE INTO OUR AREA
VERSUS SURFACE TEMPERATURES BEING AT OR BELOW FREEZING BY THE TIME
IT ARRIVES. IT NOW APPEARS THAT PRECIPITATION SHOULD PRETTY MUCH
ARRIVE FROM SOUTH TO NORTH AS TEMPERATURES AND DEWPOINTS
RISE...AND NOT MUCH IN THE WAY OF FREEZING RAIN IS EXPECTED. HAVE
SHOWN THIS IN THE LATEST GRIDS AND ZONES WHICH IS TO KEEP A DRY
FORECAST PRETTY MUCH ACRS THE WHITEWATER/MIAMI VALLEYS...WEST
CENTRAL OHIO AND CENTRAL OHIO OVERNIGHT. LOWS WILL OCCUR THIS
EVENING AND EARLY MORNING...THEN THEY SHOULD RISE AS CLOUDS
THICKEN AND THE WIND INCREASES SOME FROM THE EAST AHEAD OF THE
SURFACE LOW.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
WITH THE WEAK LOW MOVING TO EASTERN OHIO...RAIN WILL BE LIKELY
MONDAY IN SOUTHERN AND EASTERN COUNTIES...WITH A GOOD CHANCE OF
RAIN IN THE NORTH AND WEST. THE WINDOW OF OPPORTUNITY FOR FREEZING
PRECIPITATION SEEMS MINIMAL MONDAY MORNING ALONG AND NORTH OF I-70 AS
TEMPERATURES AND DEWPOINTS RISE AS THE PRECIPITATION ARRIVES.
THERE COULD BE A BRIEF PERIOD OF FREEZING RAIN AT THE ONSET BUT IT
SHOULD NOT LAST VERY LONG AND SHOULD HAVE LITTLE IF ANY IMPACT.
A RISE INTO THE 40S IS FORECAST FOR MOST LOCATIONS MONDAY
AFTERNOON.

RAIN WILL BE ENDING MONDAY EVENING WITH THE LOW EXITING TO THE
EAST. A FEW SNOW SHOWERS MAY OCCUR NORTH OF DAYTON BEFORE
PRECIPITATION CHANCES END AROUND MIDNIGHT TUESDAY. AFTER WEAK HIGH
PRESSURE ARRIVES FOR A SHORT STAY...CLOUDS WILL INCREASE AGAIN ON
TUESDAY AHEAD OF THE STRONG LOW. HIGHS AROUND 40 ARE EXPECTED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
FOCUS IS ON THE WINTER STORM WHICH WILL AFFECT THE REGION AT MID
WEEK. VIGOROUS MID LEVEL S/W TO LIFT FROM THE SRN PLAINS INTO THE
LOWER OH VLY TUESDAY NIGHT AND ACRS THE REGION WEDNESDAY. NUMERICAL
MODEL SOLNS CONTINUE TO SHOW SPREAD REGARDING THE EXACT TRACK OF THE
ASSOCIATED SFC WAVE WHICH LIFTS NE THRU THE REGION ON WEDNESDAY. IN
GENERAL THE GFS DETERMINISTIC SOLNS HAVE BEEN THE FURTHEST WEST AND
THEREFORE BRING MORE WARM AIR INTO ILN/S FA. THE ECMWF SOLN HAS BEEN
MORE CONSISTENT WITH THE LATEST 12Z DETERMINISTIC RUN TRENDING A
LITTLE WEST AND THEREFORE ALLOWING A LTL MORE INTRUSION OF WARM AIR.
GFS ENSEMBLE MEAN SOLN IS PLACED A LTL EAST OF ITS DETERMINISTIC
RUN.

HAVE TRENDED THE LATEST FCST TOWARD THE A SLIGHTLY MODIFIED (WARMER)
SOLN THAN 12Z ECMWF RUN GIVEN TRENDS AND CONSISTENCY.

HAVE SPREAD LKLY POPS IN FROM THE SOUTH TUESDAY NIGHT AND THEN
BUMPED UP POPS TO CATEGORICAL EARLY WEDNESDAY.

USING AT TOP DOWN TECHNIQUE APPLIED TO MODIFIED ECMWF SOLN HAVE FAR
WEST CENTRAL OHIO (NORTHWEST OF DAYTON) STAYING ALL SNOW BUT HAVE A
MIX SPREADING INTO THE REMAINDER OF ILN/S FA AND RAIN SE OF I-71
DURING THE DAY ON WED. AS COLDER AIR WRAPS INTO THE SYSTEM...HAVE
ALL PRECIP CHANGE BACK TO SNOW WEDNESDAY NIGHT. THIS SYSTEM HAS THE
POTENTIAL TO PRODUCE 6 INCHES OR MORE OF SNOW AND SIGNIFICANT ICE.
AT THIS TIME IT LOOKS LIKE A STORM TOTAL 4 TO 6 INCH SNOW BAND IS
PSBL FROM EAST CENTRAL INDIANA THRU FAR W CNTRL OHIO. THERE WILL
LKLY BE A SHARP CUT OFF TO THE SE WITH 1 TO 2 INCHES ALONG AND JUST
WEST OF I-71 AND LESS THAN AN INCH SE OF I-71.

GIVEN THE HIGH DEGREE OF UNCERTAINTY REGARDING THE EXACT TRACK...
WILL CONTINUE TO HIGHLIGHT THIS THREAT IN THE HWO PRODUCT.

AS THIS WINTER STORM LIFTS NE WILL TAPER OFF SNOW EARLY ON THURSDAY.
UPPER LEVEL RIDGING AND SFC RIDGING TO BUILD IN PROVIDING DRY WX
CONDITIONS LATER THURSDAY AND FRIDAY.

MODEL SOLN DIFFERENCES REGARDING THE WEATHER SYSTEM NEXT WEEKEND.
PREV GFS WAS KEEPING PCPN TO OUR SOUTH BUT LATEST RUN BRINGS IN
PRECIP BUT IS WEAKER AND ALLOWS FOR LESS WARM AIR. ECMWF SOLNS HAVE
BEEN STRONGER AND ALLOW FOR MORE INITIAL WARM AIR INTRUSION. HAVE
SPREAD CHC POPS IN FRIDAY NIGHT AND THEN CONT HIGH CHC POPS ON
SATURDAY. HAVE ALLOWED FOR A MIX OF RAIN AND SNOW OVER THE SE HALF
AND KEPT ALL SNOW NW. SOME LINGERING SNOW SHOWERS WILL BE PSBL ON
SUNDAY WITH THE BEST CHC ACRS THE NORTH.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
ANY RAIN THAT BEGINS TOWARDS DAYBREAK TODAY WILL FALL WHERE
TEMPERATURES ARE ABOVE FREEZING AND ICY CONDITIONS ARE NOT
EXPECTED TO OCCUR AT THIS MOMENT IN TIME. LOW CIGS WILL SLIDE INTO
THE CINCY METRO AREA JUST BEFORE DAYBREAK AND RAIN WILL FOLLOW
SHORTLY AFTER. SLIGHTLY LATER TIMING IS EXPECTED AT KDAY/KILN AND
BY LATE MORNING IN COLUMBUS METRO AREA.

SHOWERS SHOULD TAPER OFF IN THE EARLY AFTERNOON...LATE MORNING
FURTHER SOUTHWEST...BUT CLOUD COVER WILL REMAIN IN THE 1-2KFT
RANGE. NORTHWEST WINDS AND LOW CLOUD COVER WILL PERSIST OVERNIGHT.

OUTLOOK...IFR CEILINGS AND VISIBILITIES ARE POSSIBLE
WEDNESDAY...LIFTING TO MVFR THURSDAY.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.

&&

$$
SYNOPSIS...CONIGLIO/HICKMAN
NEAR TERM...CONIGLIO/HICKMAN
SHORT TERM...CONIGLIO
LONG TERM...AR
AVIATION...FRANKS







AREA FORECAST DISCUSSION

NWS STATE COLLEGE PA

 440 AM EST MON DEC 24 2012

.SYNOPSIS...
WEAK LOW PRESSURE WILL TRACK NORTHEAST UP THE OHIO RIVER VALLEY
TODAY...CROSSING THE REGION LATE TONIGHT. THIS WEATHER FEATURE WILL
BRING MOST AREAS OF CENTRAL PENNSYLVANIA JUST ENOUGH SNOW FOR A
WHITE CHRISTMAS. A RIDGE OF HIGH PRESSURE WILL FOLLOW FOR CHRISTMAS
DAY...WITH PLENTY OF CLOUDS AND LIGHT NORTHERLY WINDS. A MORE
SIGNIFICANT AND WIDESPREAD WINTER STORM WILL TAKE AIM ON THE ENTIRE
NORTHEAST U.S. FOR WEDNESDAY AND THURSDAY. THE POTENTIAL EXISTS FOR
HEAVY SNOWFALL ACROSS THE NORTHWEST HALF OF PENNSYLVANIA...WITH A
GRADUAL INCREASE IN MIXED PRECIPITATION HEADING SOUTHEAST TOWARD THE
LOWER SUSQUEHANNA VALLEY. BLUSTERY AND COLD CONDITIONS WITH
FLURRIES...AND MOUNTAIN SNOW SHOWERS WILL FOLLOW FOR THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
A SHALLOW WEDGE OF COLDER AIR HAS ADVECTED SOUTH TO COVER MUCH OF
THE REGION EARLY TODAY. SLIGHTLY MILDER/ABOVE FREEZING AIR AT 850 MB
WAS ADVANCING EAST ACROSS THE GREATER PITTSBURGH AREA ATTM...JUST
ABOVE THE NEARLY STALLED OUT...EAST TO WEST 925 MB FRONT. HIGH RES
NAM AND RUC MODELS SHOW THAT A BKN-OVC STRATO CU LAYER AROUND 2-3KFT
AGL WILL PERSIST THE NEXT FEW HOURS ACROSS THE NRN TIER COUNTIES...
BEFORE ERODING AROUND SUNRISE. HIGH CLOUDS WILL STREAM IN FROM THE
WSW AND THICKEN UP LATER THIS MORNING.

TEMPS AT DAYBREAK WILL BE COLDEST ACROSS THE SOUTHERN HALF OF THE
STATE /MAINLY IN THE LOWER 20S/...WHILE THE CLOUD BLANKET ACROSS THE
NORTH RESULTS IN SLIGHTLY WARMER MINS IN THE MID 20S.

00Z MODEL SUITE AND LATEST ENSEMBLE GUIDANCE SHOWS A HIGH
PROBABILITY FOR A LIGHT SNOWFALL OF AN INCH OR TWO ACROSS THE REGION
THIS AFTERNOON INTO TONIGHT AS A WEAK AREA OF LOW PRESSURE MOVES ENE
UP THE OHIO RIVER VALLEY. HIGH RES MODEL THERMAL/WET BULB THERMAL
PROFILES WITHIN 2 KFT AGL INDICATE THAT MUCH OF THE LIGHT PRECIP
WILL FALL IN THE FORM OF SNOW. THE LOWEST 1 KFT AGL MAY WARM BRIEFLY
INTO THE MID AND UPPER 30S ACROSS THE SOUTHEAST VALLEYS TO CAUSE THE
LIGHT SNOW TO MIX WITH LIGHT RAIN.

OTHERWISE...925-850 MB WET-BULB TEMPS WILL BE A FEW TO SVRL DEG C
BELOW ZERO FOR THE DURATION OF THIS EVENT...SUPPORT PRIMARILY SNOW.

THE ONLY LOCATION AT THIS POINT THAT WILL SEE A LAYER OF SLIGHTLY
ABOVE FREEZING AIR ALOFT WILL BE PORTIONS OF THE LAUREL HIGHLANDS.
THERE...SOME LIGHT FREEZING RAIN AND SLEET SHOULD MIX IN AT
TIMES...PERHAPS LEADING TO TREACHEROUS HOLIDAY TRAVEL. A WINTER
WEATHER ADVISORY WAS POSTED FOR SOMERSET COUNTY FROM 17Z TODAY
THROUGH 06Z CHRISTMAS.

SFC TEMPS THIS AFTERNOON IN THE LOWER TO MID 30S ACROSS MUCH OF THE
REMAINDER OF CENTRAL PENN SHOULD ALLOW TREATED/PRIMARY ROADS TO STAY
MAINLY WET AS SNOWFALL RATES SHOULD BE QUITE LIGHT...PERHAPS AROUND
0.25 INCH PER HOUR.

AFTER THE MAIN WAVE OF PRECIP COMES THROUGH EARLY THIS EVENING...
VERY WEAK FORCING AND SPOTTY LIGHT PRECIP WILL CONTINUE
OVERNIGHT...AND LLVL WINDS GO WESTERLY. THIS WILL PROLONG THE
NEAR-FREEZING TEMPS AND POSSIBILITY FOR -FZDZ ACROSS THE AREA...ESP
THE WRN MTS. ALL OF THE HIGH/COLD CLOUDS GO AWAY IMMEDIATELY AFTER
THE MAIN PUSH...SO GOOD SEEDING OF ICE CRYSTALS IS GONE AND MUCH OF
THE AREA COULD SEE PATCHY FZDZ. AGAIN...ALL TOO FAR AWAY AND MINOR
PRECIP AMOUNTS TO MAKE A CALL ON THIS YET.

TEMPS GREETING SANTA AND HIS REINDEER TEAM EARLY CHRISTMAS MORNING
WILL VARY FROM THE L20S UP NORTH...TO THE MID AND UPPER 20S ACROSS
CENTRAL AND SOUTHERN PENN.
&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
A WEAK RIDGE OF HIGH PRESSURE DRIFTING EAST ACROSS THE STATE WILL
PROVIDE A RATHER SHORT WINDOW OF ONLY 24-30 HOURS WITH IMPROVED
TRAVEL CONDITIONS FROM LATER CHRISTMAS MORNING INTO EARLY WEDNESDAY.

MAX TEMPS CHRISTMAS AFTERNOON WILL BE AROUND 30F ACROSS THE NW
MTNS...AND MID 30S TO LOWER 40S ELSEWHERE.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A SIGNIFICANT WINTER STORM WILL BEGIN TO STRENGTHEN ACROSS THE LOWER
MISS AND TENN VALLEYS CHRISTMAS NIGHT AND HEAD NORTHEAST...SPREADING
THE LEADING EDGE OF A LARGE SHIELD OF PRECIPITATION OVER THE SWRN
PART OF REGION DURING THE MIDDAY HOURS WEDNESDAY...AND BEGINNING
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS ELSEWHERE.

PRECIP TYPE SHOULD BE SNOW FOR AT LEAST A FEW TO SVRL HOURS IN ALL
LOCATIONS /AS 925-850 MB WET BULB TEMPS EVEN IN THE SE WILL BE -2 TO
-4C AND NOTABLY COLDER FURTHER TO THE NORTH/ THANKS TO INCREASINGLY
STRONG LLVL NORTHERLY AGEOS FLOW.

23/21Z THROUGH 24/06Z OPERATIONAL U.S. AND EURO MODEL RUNS /AND
THEIR RESPECTIVE ENSEMBLES/ ARE COMING INTO PRETTY GOOD AGREEMENT
TRACKING A DYING PRIMARY LOW NE ACROSS THE OHIO VALLEY WITH A
SECONDARY LOW RAPIDLY INTENSIFYING JUST INLAND FROM THE DELMARVA
PENINSULA LATE WEDNESDAY NIGHT.

WILL MAKE JUST SOME MINOR MODIFICATIONS TO THE PRECIP TYPE AND
AMOUNT ACROSS THE CWA FOR WEDNESDAY INTO THURSDAY.

THIS APPARENT/POTENT MILLER-B TYPE EVENT WILL EVOLVE AS THE TRANSFER
OF ENERGY TO THE DELMARVA COAST OCCURS WEDNESDAY NIGHT AT THE NOSE
OF A STRONG UPPER LEVEL JET /THAT WILL BE ROUNDING THE BASE OF THE
AMPLIFYING AND SLIGHTLY NEGATIVE TILT UPPER TROUGH/ AIMED AT THE
VA/MID ATLANTIC COAST.

WILL KEEP LAYER-CAKE PRECIP TYPES PAINTED FROM NW TO SE FOR THE
WEDNESDAY AFTERNOON/NIGHT PERIOD AS THE LATEST 06Z NAM STILL
INDICATES THAT A RATHER SHALLOW LAYER OF NEAR TO SLIGHTLY ABOVE
FREEZING AIR SURGE NWD INTO AT LEAST CENTRAL AND SRN PENN IN THE
800-750 MB LAYER AS THE ENERGY BEGINS TO TRANSFER ACROSS THE CENTRAL
APPALACHIANS.

HOWEVER...STRONG UVVEL AND DYNAMIC COOLING IN THE INCREASINGLY
DIVERGENT UPPER FLOW COULD KEEP THE PRECIP MAINLY MDT TO HVY SNOW
ACROSS THE REGION NORTH OF KAOO...KUNV AND KBGM FOR THE BULK OF THE
STORM.

QUITE A BIT OF UNCERTAINTY CONTINUES TO EXIST ON THIS KEY FEATURE
WHICH IS THE EXTENT AND DEPTH OF THE WARMER AIR INTRUSION AND ITS
ULTIMATE EFFECTS ON CENTRAL/EASTERN PORTIONS OF CWA.

THE BEST FORECAST REMAINS A LIKELY MODERATE TO HEAVY SNOWFALL ACROSS
THE NRN AND WESTERN MTNS...WITH MODERATE AMOUNTS OF SNOW/SLEET
IMPACT THE SUSQ VALLEY AND PORTIONS OF THE SCENT MTNS.

AS A RESULT OF THE HIGHLY ANOMALOUS...APPROX PLUS 4 SIGMA SERLY 850
MB JET AND 1-2 SIGMA PWATS ACCOMPANYING THIS STORM...LIQUID
EQUIVALENT QPF FOR THIS EVENT LOOKS TO BE 1-1.25 INCHES ACROSS MUCH
OF THE FCST AREA...WITH AROUND 1.5 INCHES OVER THE SOUTH AND EAST.
24/03Z SREF SHOWS A 30-50 PROBABILITY FOR STORM TOTAL PRECIP OF 2
INCHES IN OUR FAR SERN ZONES.

STORM TOTAL SNOWFALL HAS THE POTENTIAL TO BE IN THE 6-10 INCH RANGE
ACROSS THE NW/NCENT MTNS AND LAURELS...SEVERAL INCHES OF SNOW AND
SIGNIFICANT SLEET THROUGHOUT THE CENTRAL ZONES...AND A GENERAL MIXED
BAG MESS ACROSS THE LOWER SUSQ REGION...AFTER AN INITIAL PERIOD OF
SNOW. THIS CONCURS WITH HPC/S LATEST WINTER WEATHER GRAPHICS.

COLD AND BLUSTERY NORTHWEST FLOW REGIME DEVELOPS BEHIND THE
DEPARTING STORM THU AND FRI WITH CENTRAL AND SERN PENN FLURRIES AND
SCTD SNOW SHOWERS...WITH UPSLOPE SNOW AND LES IMPACTING THE LAURELS
AND NW MTNS.

ANOTHER WEAKER STORM PROGGED FOR NEXT WEEKEND LOOKS COLD ENOUGH
FOR A GENERALLY LIGHT SNOW EVENT SAT INTO SUN.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
LOW LVL MOISTURE TRAPPED BENEATH INVERSION WILL CREATE MVFR STRATOCU
ACROSS THE N MTNS EARLY THIS MORNING. ACROSS SOUTHERN PA...MCLEAR
SKIES AND A NEARLY CALM WIND COULD CREATE SOME VALLEY FOG ACROSS THE
LAUREL HIGHLANDS. HOWEVER...JST/S RIDGETOP LOCATION SHOULD PRECLUDE
FOG AT THE AIRPORT.

A LOW PRES SYSTEM RIDING UP THE OHIO VALLEY WILL SPREAD LOWERING
CLOUDS AND LGT SNOW ACROSS THE REGION THIS AFTN AND EVENING.
LATEST MDL DATA SUGGESTS A RAPID DETERIORATION IN VSBYS AS SNOW
ARRIVES ARND 18Z AT JST...THEN SPREADS NORTHEAST ACROSS THE REST
OF CENTRAL PA BY 00Z. A 4 TO 6 HR PERIOD OF SNOW WITH VSBYS BTWN
1-2SM APPEARS LIKELY AT MOST LOCATIONS. EVEN AFTER PRECIP WINDS
DOWN LATE THIS EVENING...RESIDUAL MOISTURE AND LGT WINDS SHOULD
RESULT IN LINGERING FOG/LOW CIGS ACROSS THE REGION.

OUTLOOK...
TUE...AM LOW CIGS POSS W MTNS.
WED...WINTRY MIX WITH LOW CIGS/VSBYS POSSIBLE.
THU...WINDY WITH WINTRY MIX/LOW CIGS POSS EARLY. PM SHSN POSS W MTNS.
FRI...NO SIG WX EXPECTED.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM NOON TODAY TO 1 AM EST TUESDAY
FOR PAZ033.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/RXR
AVIATION...FITZGERALD










AREA FORECAST DISCUSSION

NWS BLACKSBURG VA

 1200 AM EST MON DEC 24 2012

.SYNOPSIS...
A FAST MOVING AREA OF LOW PRESSURE WILL TRACK ACROSS THE AREA
LATE TONIGHT AND MONDAY. A STRONGER...MORE ROBUST STORM SYSTEM IS
LIKELY TO IMPACT THE REGION FOR THE MIDDLE PORTION OF THE WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 1140 PM EST SUNDAY...

LIGHT RAIN MAY SCRAPE THE SE CWA BUT OVERALL SHOULD STAY MAINLY
DRY OVERNIGHT OUTSIDE OF THE SWRN CWA. RAIN SHOULD OVERSPREAD THE
MTNS AND FOOTHILLS BY MID MORNING MONDAY. STILL LOOKS LIKE MAINLY
A FREEZING RAIN OR RAIN SCENARIO NORTH OF I-64...WITH POCKETS OF
SNOW OR SLEET FURTHER NORTH. NO CHANGES TO THE WINTER WX ADVISORY.

PREVIOUS DISCUSSION...
GETTING A FEW SPRINKLES OR LIGHT RAIN INTO
THE NC MTNS. REGIONAL RADAR CONTINUES TO SHOW MAIN AXIS OF RAIN
FROM NORTHEAST TN SOUTHWEST TO NRN AL. AGAIN THE 12Z ECMWF AND THE
19Z WRF AND 21Z RUC SHOW THE BEST MATCH FOR THE CURRENT SCENARIO.
WITH THIS IN MIND THINK THE GFS/NAM OVERDONE ON QPF AND SPEED...SO
TIMED THE ONSET OF PRECIP A COUPLE TO 4 HOURS LATER. THIS IN HAS
ALLOWED TEMPS TO DROP LOWER THAN FORECAST INTO THE ALLEGHANY
HIGHLANDS AND GREENBRIER COUNTY WV AREA...AS HIGH CLOUDS UP THERE
HAVE BEEN THIN.

OVERNIGHT...THE CLOUD COVER THICKENS. ONE PIECE OF ENERGY WILL
MOVE EAST ALONG THE NC/VA BORDER WITH A SLIGHT CHANCE OF RAIN
HERE...BEFORE BETTER OMEGA ARRIVES INTO THE MTNS BY 12Z. MODEL
SOUNDINGS AND THERMAL PROFILES INDICATE A MAINLY RAIN/FREEZING
RAIN SCENARIO IN THE WINTER WX ADVISORY AREA...SOME SLEET OR SNOW
POSSIBLE MAINLY NRN BATH COUNTY/NRN GREENBRIER COUNTY. DESPITE THE
SLOW DOWN OF ONSET WILL LEAVE BEGINNING TIME OF ADVISORY AS IS.
MAY NEED TO EXTEND THE ADVISORY IN TIME TIL NOON BUT
OVERALL...WINTERY WX APPEARS TO BE ALL BUT GONE BY 10 AM...OUTSIDE
THE GREENBRIER/POCOHONTAS BORDER. WILL TAKE A LOOK AT NEWER DATA
TO SEE IF THE ADVISORY NEEDS TO BE EXTENDED IN TIME. MAIN CONCERN
IS THE COOLER TEMPS NOW AND THE FACT THAT THE SFC WIND BECOMES
MORE NE ACROSS THE HIGHLANDS AND ADJACENT VALLEYS BY MORNING.


COLD RAIN CONTINUES THROUGH THE DAY. MODEL QPF...WHICH MAY BE ON
THE HIGH SIDE...DURING THE RAIN IS ON THE ORDER OF A QUARTER TO A
THIRD OF AN INCH. WITH CLOUDS AND PRECIPITATION PLAYED HIGH
TEMPERATURES MONDAY ON THE COOLER SIDE OF MOS WITH READINGS FROM
THE MID 30S IN THE NORTH TO THE MID 40S IN THE SOUTHEAST.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 310 PM EST SUNDAY...

THE INFLUENCE OF A WEAK AREA OF LOW PRESSURE WILL BE WANING
CHRISTMAS EVE AS THE SYSTEM DEPARTS THE UPPER OHIO VALLEY AND FILLS
AS IT HEADS INTO NEW ENGLAND. A TRAILING COLD FRONT WILL PUSH ACROSS
THE CWA OVERNIGHT WITH LITTLE OR NO COLD AIR ADVECTION BEHIND
IT..H85 TEMPS REMAIN IN THE +2 TO +4 RANGE...SO DO NOT EXPECT POST-
FRONTAL UPSLOPE PRECIPITATION ISSUES. SKIES WILL CLEAR AT LEAST
PARTIALLY TOWARDS CHRISTMAS MORNING WITH TEMPS ONLY FALLING OFF INTO
LOW 30S IN COOLER MOUNTAIN VALLEYS TO UPPER 30S PIEDMONT...GENERALLY
5 TO 10F ABOVE CLIMO. WITH WEAK AND TRANSITORY SHORT-WAVE RIDGING
OVER THE AREA SHOULD START CHRISTMAS DAY UNDER CLEAR TO PARTLY
CLOUDY SKIES AND REMAINING FAIRLY MILD AS WELL WITH HIGHS INTO THE
40S MOUNTAINS AND LOW 50S PIEDMONT...AGAIN POSITIVE DEPARTURES OF
5F TO 10F. RAPID CHANGES LOOK TO BE IN THE OFFING HOWEVER AS ALL
MODELS ARE CONSISTENT IN DEVELOPING SURFACE LOW PRESSURE WHICH
STRENGTHENS IN THE GULF COAST AREA IN RESPONSE TO A VIGOROUS UPPER
JET DIGGING INTO THE SOUTHERN HIGH PLAINS LATE ON CHRISTMAS DAY.
MAY PRODUCE A WHITE CHRISTMAS NIGHT ACROSS PORTIONS OF
OKLAHOMA/ARKANSAS AREA. LOW IS FORECAST BY ALL DETERMINISTIC
MODELS (INCLUDING CMC WHICH HELD TO EASTERN TRACK YESTERDAY) AND
MAJORITY OF GFS ENSEMBLES TO TRACK WEST OF APPALACHIANS AND INTO
THE OHIO VALLEY WITH A BROAD AREA OF OVERRUNNING PRECIP LIFTING
NORTHWARD INTO THE REGION. PWATS SURGE FROM AROUND 0.5 INCHES TO
NEAR 1 INCH BY EARLY WEDNESDAY (APPROX +2 SD ABOVE NORMAL) SO
SHOULD BE PLENTY OF MOISTURE AVAILABLE. STORM TOTAL QPF 1 TO 1.5
INCHES NOT OUT OF THE QUESTION BY WEDNESDAY EVENING. WHILE THIS IS
EXPECTED TO BE PRIMARILY A RAIN EVENT...P- TYPE ISSUES MAY EXIST
AT THE OUTSET MAINLY IN THE FAR NW AS TRAPPED COLD AIR AT THE
SURFACE BRINGS A PERIOD OF SLEET OR MIXED PRECIP AND AGAIN IN THE
WAKE OF THE LOW AS UPSLOPE PRECIP DEVELOPS IN THE COLD AIR
ADVECTION. REGARDING THE INITIAL PERIOD...CLOUDS SPREADING IN
QUICKLY ON TUESDAY NIGHT MAY PRECLUDE MUCH OPPORTUNITY FOR TEMPS
TO RADIATE OFF FROM DAYTIME HIGHS WHICH SHOULD BE WELL ABOVE
FREEZING HENCE LIMITING FROZEN PCPN CHANCES. USING MODEL BLEND MIN
TEMPS FOR TUES NIGHT YIELDS SUB-32 LOWS IN ONLY FAR NW
GREENBRIER..BATH AND ROCKBRIDGE COUNTIES. MUCH COLDER WRAPS IN
BEHIND THE LOW WEDNESDAY NIGHT AS H85 TEMPS FALL TO -4C TO -8C
DEPENDING ON MODEL OF CHOICE AND NORTHWEST FLOW INCREASES..VERY
LIKELY TO SEE MOUNTAIN SNOWS IN FAVORED AREAS WITH ONLY FLURRIES
TOWARD THE BLUE RIDGE AND NEW RIVER VALLEYS.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 255 PM EST SUNDAY...

DURING THE THURSDAY AND THURSDAY NIGHT PORTION OF THE FORECAST...THE
REGION WILL BE UNDER THE INFLUENCE OF STRONG NORTHWEST FLOW ON THE
BACKSIDE OF THE EXITING SYSTEM. THIS PATTERN WILL PROVIDE FOR VERY
GUSTY WINDS...ESPECIALLY AT THE RIDGE TOPS. WINDS AT 850 MB ARE
PROGGED TO BE IN THE 40 TO 50 KT RANGE. THIS MAY TRANSLATE TO
SURFACE GUSTS ONCE AGAIN IN THE ADVISORY TO NEAR WARNING LEVEL
RANGE. THE UPSLOPE SNOW MACHINE WILL AGAIN BE SWITCHED ON WITH THE
PREFERRED WEST FACING SLOPES OF WESTERN GREENBRIER COUNTY WEST
VIRGINIA...SOUTH INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA
EXPERIENCING MEASURABLE SNOWFALL. SOME AREAS MAY SEE ENHANCED SNOW
BANDS AS 850 MB TRAJECTORIES MAY TAP LAKE MICHIGAN.

THIS SYSTEM WINDS DOWN ON FRIDAY AS AN UPPER SHORTWAVE RIDGE PASSES
ACROSS THE REGION. THE BREAK IN THE PRECIPITATION WILL BE SHORT
LIVED. BY FRIDAY NIGHT...OVERRUNNING PRECIPITATION IN ADVANCE OF THE
NEXT SYSTEM MOVING THROUGH THE MID MISSISSIPPI VALLEY WILL REACH OUR
REGION. THE 12Z...7AM GFS IS ABOUT SIX HOURS SLOWER AS COMPARED TO
THE 12Z...7AM ECMWF SOLUTION BUT NOT ENOUGH TO FEEL RELATIVELY
CONFIDENT TO HAVE A LATE FRIDAY NIGHT START TIME FOR MOST OF THE
FORECAST REGION. WILL HAVE A SLIGHT CHANCE IN THE FAR WEST AND
SOUTHWEST BEFORE MIDNIGHT.

THE GFS/ECMWF BOTH HAVE THE FOCUS FOR GREATEST POTENTIAL OF
PRECIPITATION ACROSS THE AREA ON SATURDAY...WITH THE ECWMF JUST
SLIGHTLY QUICKER ON THE DEPARTURE OF THE MAIN AREA OF PRECIPITATION.

THE BIGGEST QUESTION DURING THE THURSDAY NIGHT AND FRIDAY TIME FRAME
IS PRECIPITATION TYPE. BOTH THE GFS AND ECMWF HAVE ENOUGH SUBTLE
DIFFERENCES WITH THE LOW LEVEL TEMPERATURE PROFILE THAT A MIXED BAG
OF PRECIPITATION IS POSSIBLE ACROSS THE AREA. THE MODEL GUIDANCE
FROM YESTERDAY FAVORED MORE OF A RAIN VERSUS FREEZING RAIN SCENARIO.
GUIDANCE FROM TODAY OFFERS A TREND TOWARD SLIGHTLY MILDER SURFACE
TEMPERATURES WITH THE 0C 850 MB ISOTHERM IN THE VICINITY OF THE
MIDDLE OF THE FORECAST AREA...THUS OPENING THE FULL GAMBIT OF
WEATHER OPTIONS. WITH A TREND TOWARD WARMER SURFACE
TEMPERATURES...WILL OFFER A RAIN VERSUS SNOW SOLUTION ACROSS THE
AREA BASED UPON SURFACE TEMPERATURES.

SATURDAY NIGHT INTO SUNDAY...WE SWITCH ON THE UPSLOPE SNOW MACHINE
AGAIN IN THE WAKE OF THE FRI/SAT SYSTEM. 850 MB WINDS ARE NOT
PROGGED TO BE AS ROBUST AS COMPARED TO THOSE ANTICIPATED THURSDAY
AND THURSDAY NIGHT. AS SUCH...BOTH SURFACE WIND GUSTS AND SNOW
AMOUNTS MAY NOT BE AS GREAT COMPARATIVELY.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 1150 PM EST SUNDAY...

LOWER CLOUDS ARRIVED QUICKER OVER BLF MAINLY DUE TO BREAK IN THE
HIGHER CLOUDS AND INCREASE DEWPOINTS FROM THE SOUTHWEST. STILL
LOOKING AT POOR FLYING CONDITIONS AT ALL TAF SITES BETWEEN 12Z AND
15Z LASTING THROUGH THIS TAF PERIOD. SOME LIGHT FREEZING RAIN IS
POSSIBLE AROUND 12Z AT LWB OTHERWISE RAIN AND FOG...TAPERING TO
DRIZZLE BY MONDAY EVENING.


CONDITIONS SHOULD IMPROVE SLOWLY LATE MONDAY NIGHT WITH VFR
EXPECTED BY CHRISTMAS DAY. HOWEVER THIS IS SHORT LIVED AS A
ANOTHER STORM SYSTEM MOVES INTO THE TN VALLEY FROM THE SOUTHWEST.
THIS MID WEEK STORM LOOKS TO BE MUCH STRONGER...WITH MODELS
DEEPENING THIS SYSTEM RAPIDLY AS IT MOVES ALONG THE SPINE OF THE
APPALACHIANS. THIS STORM WILL LIKELY HAVE A MUCH WIDER AREAL
IMPACT COMPARED TO MONDAYS WEAKER SYSTEM...WITH IMPLICATIONS THAT
IT WILL BECOME A MAJOR WINTER STORM FOR PARTS OF THE APPALACHIAN
SPINE INTO NEW ENGLAND...IMPACTING AIR TRAVEL FOR THE POST
HOLIDAY. ANOTHER LOW CENTER ARRIVE AROUND THE END OF THE WEEK.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY FROM 4 AM TO 10 AM EST MONDAY FOR
     VAZ019-020.
NC...NONE.
WV...WINTER WEATHER ADVISORY FROM 4 AM TO 10 AM EST MONDAY FOR
     WVZ045.

&&

$$
SYNOPSIS...PM
NEAR TERM...KK/WP
SHORT TERM...PC
LONG TERM...DS
AVIATION...KK/PM/WP




AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 255 AM CST MON DEC 24 2012

.SHORT TERM...TODAY THROUGH WEDNESDAY
255 AM CST MON DEC 24 2012

IMMEDIATE FORECAST CONCERN IS FOCUSED ON LIGHT SNOW CHANCES TODAY
WITH THE POSSIBILITY OF SOME FREEZING DRIZZLE OVER A PORTION OF
NORTHEAST IA INTO FAR SOUTHWEST WI.

WATER VAPOR/IR IMAGERY SHOW A MID-LEVEL SHORTWAVE CIRCULATION
CENTERED NEAR THE ND/SD/MN BORDER. OUR FORECAST WAS AREA UNDER A
MIXTURE OF LOW/MID/HIGH CLOUDS AHEAD OF THE WAVE WHILE RADAR MOSAIC
SHOWED SOME LIGHT SNOW IMMEDIATELY TIED TO THE WAVE ACROSS CENTRAL
MN INTO EASTERN ND/SD.

THIS MID-LEVEL WAVE WILL MOVE EAST ACROSS THE AREA TODAY. MODELS
CONTINUE TO BE IN AGREEMENT IN PRODUCING VERY LIGHT QPF WITH THIS
FEATURE...WITH THE GFS MOST WIDESPREAD IN NATURE. MEANWHILE...HIRES
ARW/NMM MODELS SHOW A GENERAL BLOSSOMING DURING THE LATE MORNING
INTO THE AFTERNOON HOURS ACROSS THE SOUTHEAST HALF OF WI. THIS SEEMS
TO BE TIED WITH INCREASING LOW-LEVEL FETCH OF MOISTURE OFF LAKE
MICHIGAN COMBINED WITH CONVERGENCE ALONG AN INVERTED SURFACE TROUGH
WHICH IS A SURFACE REFLECTION OF THE MID-LEVEL WAVE. DIMINISHED
FREEZING DRIZZLE TO A SLIGHT CHANCE MENTION OVER PORTIONS OF
NORTHEAST IA INTO FAR SOUTHWEST WI DUE TO MODEL SOUNDINGS SHOWING
MORE ICE NOW FOR SNOW PRODUCTION. GENERALLY EXPECTING A COUPLE
TENTHS TO PERHAPS A HALF INCH OF SNOW ACCUMULATION ACROSS THE AREA
THROUGH TODAY.

HIGH PRESSURE WILL MOVE INTO THE AREA TONIGHT BEHIND THE DEPARTING
MID-LEVEL WAVE FOE DECREASING CLOUDS WITH TEMPERATURES DROPPING INTO
THE -1 TO +10F RANGE.

HIGH PRESSURE WILL REMAIN IN CONTROL ACROSS THE FORECAST AREA
THROUGH WEDNESDAY WHILE A STRONG LOW PRESSURE SYSTEM MAKES ITS WAY
THROUGH THE SOUTHERN PLAINS INTO THE APPALACHIANS. CLOUDS COULD BE
KIND OF TRICKY DUE TO A NORTHEAST AIRFLOW ACROSS LAKE SUPERIOR. THIS
MAY DRAG STRATUS/STRATOCUMULUS SOUTHWARD INTO THE AREA FROM TIME TO
TIME. KEPT SKIES PARTLY CLOUDY THROUGH THIS PERIOD FOR NOW.
OTHERWISE...TEMPERATURES CHRISTMAS DAY WILL BE ON THE CHILLY SIDE
WITH HIGHS ONLY TOPPING OFF IN THE SINGLE DIGITS TO THE TEENS.
WEDNESDAY LOOKS TO BE A FEW DEGREES WARMER BUT REMAINING BELOW
NORMAL WITH HIGHS IN THE TEENS TO THE MIDDLE 20S.

.LONG TERM...THURSDAY THROUGH SUNDAY
255 AM CST MON DEC 24 2012

24.00Z ECMWF/GFS REMAIN IN GOOD AGREEMENT THROUGH SUNDAY. BOTH
MODELS SHOW A RIDGE OF HIGH PRESSURE OVER THE AREA THROUGH
THURSDAY...THEN BRING A FAIRLY VIGOROUS MID-LEVEL TROUGH EJECTING
NORTHEAST OUT OF THE CENTRAL ROCKIES INTO THE AREA FRIDAY THROUGH
FRIDAY NIGHT FOR A CHANCE OF LIGHT SNOW. ANOTHER TROUGH OF LOW
PRESSURE DROPS SOUTHEAST OUT OF CANADA INTO THE AREA DURING THE DAY
SATURDAY FOR ANOTHER SHOT AT SOME LIGHT SNOW. A WEAK RIDGE OF HIGH
PRESSURE MOVES INTO THE AREA SATURDAY NIGHT/SUNDAY...PUSHING SNOW
CHANCES EASTWARD INTO THE GREAT LAKES REGION. OTHERWISE...APPEARS
TEMPERATURES WILL BE RIGHT AROUND NORMAL WITH LOWS IN THE TEENS AND
HIGHS IN THE 20S FOR THURSDAY THROUGH SATURDAY...THEN SLIPPING TO
BELOW NORMAL ON SUNDAY WITH HIGHS STRUGGLING INTO THE TEENS AND
LOWER 20S.

&&

.AVIATION...
1105 PM CST SUN DEC 23 2012

CLOUDS WILL BE ON THE INCREASE AND LOWER OVERNIGHT AS AN
UPPER LEVEL SHORTWAVE APPROACHES FROM THE PLAINS. LATEST FOG/STRATUS
SATELLITE IMAGERY AND SFC OBS POINT TO AN AREA OF SUB 3 KFT CLOUDS
OVER SD...HEADING SOUTHEAST. ANOTHER BAND OF LOW CLOUDS HUNG
WEST-EAST ACROSS IOWA...BUT WILL LIKELY STAY THERE. RAP13 DOING A
PRETTY DECENT JOB WITH THE LOW SATURATION...COMPARING RH TO
SATELLITE AND SOUNDINGS TO LAPS. RAP WOULD BRING THE LOW CLOUDS DUE
EAST THOUGH. SOME SAG SOUTH WITH THE UPPER LEVEL SHORTWAVE - PER
LATEST WATERVAPOR IMAGERY - BUT MORE EAST. WILL LEAN TOWARD A MORE
ESE MOVEMENT FOR THE LOW CLOUDS FOR NOW. PCPN WILL COME WITH THE
SHORTWAVE...AND IT LOOKS LIKE S-- FOR KRST/KLSE. BUFKIT SOUNDINGS
VIA THE RAP13/NAM12 SUGGESTIVE OF SOME POTENTIAL FOR -FZDZ TO THE
SOUTH EARLY MONDAY MORNING...BUT SOUTH OF THE TAF SITES. WILL STICK
WITH LIGHT SNOW FOR NOW. ANY SNOW ACCUMS WOULD BE MINIMAL.

THE SNOW SHOULD CLEAR TO THE EAST BY 18-21Z...BUT SOUNDINGS
CONTINUE TO FAVOR KEEPING LOW SATURATION UNDER AN INVERSION FOR THE
NIGHTTIME HOURS. THINK THERE SHOULD BE SOME IMPROVEMENT IN
CIGS...BUT COULD STAY AT LEAST MVFR THROUGH MUCH OF THE NIGHT...WITH
CLEARING THEN FOR CHRISTMAS DAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
255 AM CST MON DEC 24 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...DAS
LONG TERM....DAS
AVIATION.....RIECK















AREA FORECAST DISCUSSION

NWS LA CROSSE WI

 1105 PM CST SUN DEC 23 2012

.SHORT TERM...TONIGHT THROUGH WEDNESDAY
237 PM CST SUN DEC 23 2012

MAIN FORECAST CONCERNS REMAIN ON LIGHT PRECIPITATION CHANCES TONIGHT
THROUGH MONDAY...WITH THE POTENTIAL FOR SOME LIGHT FREEZING DRIZZLE
SOUTH OF INTERSTATE 90.

LATEST WATER VAPOR IMAGERY SHOWED A SHORTWAVE TROUGH MOVING INTO THE
WESTERN DAKOTAS MOVING EAST. A BROAD UPPER LOW WAS CENTERED OVER
JAMES BAY WITH NORTHWEST FLOW ALOFT NOTED ACROSS MUCH OF THE
WESTERN GREAT LAKES. SURFACE OBSERVATIONS SHOWED PERSISTENT
STRATUS STRETCHING ACROSS PORTIONS OF NORTHEAST IOWA THROUGH MUCH
OF SOUTHERN WISCONSIN. A FEW LAKE EFFECT CLOUDS WERE STREAMING
INTO FAR NORTHERN WISCONSIN ON NORTHERLY FLOW NEAR THE SURFACE.
SCATTED HIGH CIRRUS WILL CONTINUE FLOWING IN FROM THE WEST AHEAD
OF THE APPROACHING SHORTWAVE.

THE SHORTWAVE WILL MOVE EAST AND INTO THE UPPER MISSISSIPPI RIVER
VALLEY LATE TONIGHT. FORECAST MODELS CONTINUE TO BRING LIGHT
PRECIPITATION INTO THE AREA AND THIS HAS BEEN A CONSISTENT SIGNAL.
THERE IS A CONCERN TONIGHT REGARDING WEATHER OR NOT THERE WILL BE
ICE PRESENT ALOFT FOR THE PRODUCTION OF SNOW. FORECAST SOUNDINGS
SUGGEST THERE MAY NOT BE ICE DURING THE ONSET OF PRECIPITATION
SOUTH OF INTERSTATE 90. THIS APPEARS TO BE MORE OF AN ISSUE ALONG
AND EAST OF THE MISSISSIPPI RIVER DURING THE DAY ON MONDAY. 12Z KBLR
NAM SOUNDING SHOWS THE TOP OF THE CLOUD LAYER AROUND -8C BY 11Z
MONDAY MORNING...THEN COOLS AND DEEPENS RATHER QUICKLY DURING THE
MORNING HOURS WITH -10C AT THE TOP OF THE CLOUD BY 15Z. CANNOT RULE
OUT A PERIOD OF LIGHT FREEZING DRIZZLE ON MONDAY...WITH THE HIGHEST
CHANCES SOUTH OF INTERSTATE 90 AND MAINLY EAST OF THE MISSISSIPPI
RIVER. LOCATIONS NORTH OF INTERSTATE 90 WILL SEE LIGHT SNOW LATE
TONIGHT THROUGH MONDAY MORNING WITH ACCUMULATIONS OF UP TO 1 INCH
POSSIBLE. THE SHORTWAVE QUICKLY PUSHES INTO EASTERN WISCONSIN MONDAY
AFTERNOON BUT AN INVERTED SURFACE TROUGH LINGERS ACROSS SOUTHWEST
INTO CENTRAL WISCONSIN. THERE IS EXCELLENT AGREEMENT IN THE FORECAST
MODELS WITH THIS FEATURE REGARDING PLACEMENT...TIMING...AND
PRECIPITATION AMOUNT. DECIDED TO INCLUDE A STRIP OF LIKELY
PRECIPITATION CHANCES EXTENDING FROM CENTRAL WISCONSIN INTO FAR
SOUTHWEST WISCONSIN. WITH THE TOP OF THE CLOUD LAYER NOT REALLY
TAPPING INTO ICE WILL MAINTAIN PATCHY FREEZING DRIZZLE IN THE
FORECAST. PLAN ON MOSTLY CLOUDY SKIES ON MONDAY WITH HIGH
TEMPERATURES RANGING FROM THE LOWER 20S ACROSS NORTHERN WISCONSIN TO
THE UPPER TEENS ACROSS WESTERN SECTIONS OF NORTHEAST IOWA.

WEAK SURFACE HIGH PRESSURE WILL BUILD INTO THE UPPER MISSISSIPPI
RIVER VALLEY LATE CHRISTMAS EVE AND WILL REMAIN OVER THE REGION
THROUGH CHRISTMAS DAY. COLDER AIR IS EXPECTED TO MOVE INTO THE
REGION CHRISTMAS EVE WITH OVERNIGHT LOWS RANGING FROM THE UPPER
SINGLE DIGITS ACROSS FAR SOUTHWEST WISCONSIN TO THE THE SINGLE
DIGITS BLOW ZERO ACROSS PORTIONS OF SOUTHEAST MINNESOTA THROUGH
NORTH CENTRAL WISCONSIN. PLAN ON PARTLY SUNNY SKIES ACROSS THE AREA
ON CHRISTMAS DAY WITH HIGHS MAINLY IN THE TEENS. A FEW LOCATIONS
ACROSS CENTRAL INTO FAR SOUTHWEST WISCONSIN MAY APPROACH 20. A
POTENT UPPER TROUGH WILL MOVE ACROSS THE SOUTHERN PLAINS ON TUESDAY
AND LIFT INTO THE OHIO RIVER VALLEY REGION ON WEDNESDAY AND
EVENTUALLY INTO NEW ENGLAND WEDNESDAY NIGHT. THIS SYSTEM STILL LOOKS
TO STAY WELL EAST OF THE REGION. HIGH PRESSURE WILL REMAIN IN
CONTROL THROUGH WEDNESDAY NIGHT WITH DRY AND COOL CONDITIONS
EXPECTED. PLAN ON HIGHS ON WEDNESDAY RANGING FROM THE LOWER TEENS
ACROSS PORTIONS OF SOUTHEAST MINNESOTA TO THE LOWER 20S OVER CENTRAL
WISCONSIN

.LONG TERM...THURSDAY THROUGH SUNDAY
237 PM CST SUN DEC 23 2012

23.12 MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT THROUGH
THURSDAY. THE ECMWF AND GFS ARE LEANING TOWARD SIMILAR SOLUTIONS
FRIDAY INTO SATURDAY WITH THE EVOLUTION OF A NORTHERN AND SOUTHERN
STREAM TROUGH. THE ECMWF WAS PREVIOUSLY TRYING TO MERGE THESE TWO
FEATURES OVER THE UPPER MISSISSIPPI RIVER VALLEY...POTENTIALLY
BRINGING SIGNIFICANT SNOW ACCUMULATIONS TO THE AREA ON SATURDAY.
THE ECMWF NOW SHOWS THE SOUTHERN WAVE DRIVING MUCH FURTHER EAST.
THE LATEST ECMWF SHOWS A VIGOROUS UPPER LOW TAKING SHAPE OVER THE
OHIO RIVER VALLEY ON SATURDAY. THE GFS CONTINUES TO KEEP A SERIES
OF OPEN WAVES AS THEY PROGRESS OVER THE FORECAST AREA. THE
NORTHERN WAVE LOOKS TO MOVE ACROSS THE UPPER MISSISSIPPI RIVER
VALLEY FRIDAY INTO SATURDAY BRINGING CHANCES FOR LIGHT SNOW TO THE
AREA. MAJOR DIFFERENCES NOTED SUNDAY WITH THE ECMWF BUILDING A
RIDGE OVER THE CENTRAL CONUS AND THE GFS SHOWING COOL NORTHWEST
FLOW ALOFT OVER THE AREA. WILL LEAN TOWARD A MODEL CONSENSUS BLEND
THROUGH NEXT WEEKEND.

&&

.AVIATION...
1105 PM CST SUN DEC 23 2012

CLOUDS WILL BE ON THE INCREASE AND LOWER OVERNIGHT AS AN UPPER LEVEL
SHORTWAVE APPROACHES FROM THE PLAINS. LATEST FOG/STRATUS SATELLITE
IMAGERY AND SFC OBS POINT TO AN AREA OF SUB 3 KFT CLOUDS OVER
SD...HEADING SOUTHEAST. ANOTHER BAND OF LOW CLOUDS HUNG WEST-EAST
ACROSS IOWA...BUT WILL LIKELY STAY THERE. RAP13 DOING A PRETTY
DECENT JOB WITH THE LOW SATURATION...COMPARING RH TO SATELLITE AND
SOUNDINGS TO LAPS. RAP WOULD BRING THE LOW CLOUDS DUE EAST THOUGH.
SOME SAG SOUTH WITH THE UPPER LEVEL SHORTWAVE - PER LATEST
WATERVAPOR IMAGERY - BUT MORE EAST. WILL LEAN TOWARD A MORE ESE
MOVEMENT FOR THE LOW CLOUDS FOR NOW. PCPN WILL COME WITH THE
SHORTWAVE...AND IT LOOKS LIKE S-- FOR KRST/KLSE. BUFKIT SOUNDINGS
VIA THE RAP13/NAM12 SUGGESTIVE OF SOME POTENTIAL FOR -FZDZ TO THE
SOUTH EARLY MONDAY MORNING...BUT SOUTH OF THE TAF SITES. WILL STICK
WITH LIGHT SNOW FOR NOW. ANY SNOW ACCUMS WOULD BE MINIMAL.

THE SNOW SHOULD CLEAR TO THE EAST BY 18-21Z...BUT SOUNDINGS
CONTINUE TO FAVOR KEEPING LOW SATURATION UNDER AN INVERSION FOR THE
NIGHTTIME HOURS. THINK THERE SHOULD BE SOME IMPROVEMENT IN
CIGS...BUT COULD STAY AT LEAST MVFR THROUGH MUCH OF THE NIGHT...WITH
CLEARING THEN FOR CHRISTMAS DAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
237 PM CST SUN DEC 23 2012

WI...NONE.
MN...NONE.
IA...NONE.

&&

$$

SHORT TERM...WETENKAMP
LONG TERM....WETENKAMP
AVIATION.....RIECK















AREA FORECAST DISCUSSION

NWS GREEN BAY WI

 1055 PM CST SUN DEC 23 2012

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY

THE LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW ARCTIC HIGH
PRESSURE STRETCHING FROM NORTHERN ALBERTA TO THE WESTERN GREAT LAKES
EARLY THIS AFTERNOON.  LOW LEVEL STRATO-CU RAPIDLY DISSIPATED LATE
THIS MORNING ACROSS ALL BUT FAR NORTH-CENTRAL WISCONSIN.  MEANWHILE
UPSTREAM...A SHORTWAVE TROUGH IS MOVING EAST OVER NORTH-DAKOTA WHERE
IT IS PRODUCING 1-3SM IN LIGHT SNOW.  MID AND HIGH CLOUDS ARE
ALREADY ENTERING WESTERN WISCONSIN AHEAD OF THIS SYSTEM.  AS THE
SHORTWAVE CONTINUES TO MOVE EAST THROUGH THE REGION LATE TONIGHT AND
TOMORROW...PRECIP CHANCES ARE THE MAIN FORECAST CONCERN.

TONIGHT...HIGH PRESSURE WILL BE IN PLACE FOR THE FIRST PART OF THE
EVENING WITH ONLY LIGHT NORTHWEST FLOW CREATING LOW STRATO-CU OVER
FAR N-C WISCONSIN.  HOWEVER...MID AND HIGH CLOUDS WILL BE ON THE
INCREASE AND LOWERING THROUGH THE NIGHT AHEAD OF A SHORTWAVE TROUGH
MOVING EAST OVER THE NORTHERN PLAINS.  THIS WAVE WILL BE APPROACHING
THE NORTHERN MISSISSIPPI VALLEY LATE TONIGHT...AND WILL PUSH DECENT
MID AND UPPER FORCING INTO THE REGION.  850MB LOW AND SURFACE
INVERTED TROUGH WILL HANG BACK OVER NE IOWA AND SOUTHEAST MINNESOTA
WHERE LOW LEVEL MOISTURE ARRIVES BY 12Z MONDAY.  AS A
RESULT...PROGGED SOUNDINGS INDICATE A PROMINENT DRY WEDGE BETWEEN
925 AND 700MB THAT WILL HAVE TO SATURATE BEFORE PRECIP ARRIVES.
KEPT A SMALL CHANCE OF LIGHT SNOW OVER N-C WISCONSIN WHERE LOW
STRATO-CU COULD BECOME SEEDED BY THE LOWERING MID-DECK LATE.  BUT THINK
THE REMAINING PART OF THE CWA WILL HAVE TO WAIT UNTIL MONDAY MORNING
FOR PRECIP CHANCES.  LOWS IN THE MIDDLE SINGLE DIGITS NORTH TO THE
MID TEENS SOUTH.

MONDAY...THE SHORTWAVE TROUGH WILL MOVE ACROSS THE STATE THROUGH
ABOUT MID-AFTERNOON BEFORE DEPARTING TO THE EAST.  WILL SEE
INCREASING AMOUNTS OF LOW AND MID-LEVEL MOISTURE...AND THE DRY WEDGE
IN THE SOUNDINGS ERODES OVER THE COURSE OF THE MORNING.  DESPITE THE
850MB LOW AND INVERTED SURFACE TROUGH PASSING BY TO OUR
SOUTH...THINK WILL HAVE ENOUGH LIFT ABOVE 700MB FOR AT LEAST A
CHANCE OF LIGHT SNOW EVERYWHERE.  THE BEST CHANCES WILL REMAIN OVER
N-C WISCONSIN AND THE LAKE MICHIGAN SHORELINE DUE TO THE AID OF A
SMALL LAKE EFFECT COMPONENT.  THOUGH THE FORCING WILL EXIT THE STATE
DURING THE AFTERNOON...IT SEEMS THAT ENOUGH LOW LEVEL MOISTURE WILL
LINGER TO KEEP SKIES CLOUDY WITH SCATTERED FLURRY ACTIVITY.  WILL
SHOW A HALF INCH TO AN INCH OF ACCUMULATION OVER N-C AND FAR NE
WISCONSIN.  HIGHS MAINLY IN THE LOW TO MID 20S.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY.

WESTERN GREAT LAKES REGION LOOKS TO REMAIN ON THE NORTHERN
PERIPHERY OF RATHER ACTIVE SOUTHERN STREAM. OTHER THAN SOME
LINGERING LIGHT SNOW OR FLURRIES ACROSS THE FAR EASTERN SECTION OF
THE FORECAST AREA MONDAY EVENING WITH DEPARTING DISTURBANCE...GENERALLY
BENIGN WEATHER EXPECTED OVER THE FORECAST AREA THROUGH MOST OF THE
WORK WEEK. EXCEPTION WILL BE SOME MARGINAL LAKE EFFECT SNOW
CHANCES ALONG THE LAKE MICHIGAN SHORELINE AND THE TRADITIONAL LAKE
SUPERIOR SNOW BELT REGION. DAYTIME TEMPERATURES WILL START OUT A
FEW DEGREES BELOW NORMAL EARLY IN THE WEEK THEN GRADUALLY REBOUND
TO NEAR OR SLIGHTLY ABOVE NORMAL BY THE END OF THE WEEK.

MODELS CONTINUE TO MAINTAIN THAT AN IMPRESSIVE STORM SYSTEM WILL
TAKE SHAPE OVER THE SOUTHERN MISSISSIPPI VALLEY TUESDAY NIGHT THEN
HEAD NORTHEAST ACROSS THE OHIO VALLEY. SYSTEM WILL LIKELY GET
CLOSE ENOUGH TO BRING MID-HIGH CLOUDS INTO THE AREA LATE TUESDAY
NIGHT INTO WEDNESDAY. LIGHT STRATIFORM PRECIPITATION MAY CLIP
SOUTHEAST CORNER OF WISCONSIN...BUT SHOULD STAY SOUTH OF THE
FORECAST AREA. HOWEVER...WILL NEED TO KEEP AN EYE ON THIS SYSTEM
AS A SLIGHT JOG TO THE WEST COULD BRING A LITTLE LIGHT SNOW INTO
FAR SOUTHEAST PORTION OF THE FORECAST AREA. IN ADDITION...WEAK
NORTHERN STREAM DISTURBANCE IS ALSO FORECAST TO APPROACH THE
FORECAST AREA LATE WEDNESDAY AND POSSIBLY PHASE WITH MAIN SYSTEM
OVER LOWER MICHIGAN. THIS WEAK DISTURBANCE COULD ALSO BRING A
LITTLE LIGHT SNOW OR FLURRIES OVER EASTERN WISCONSIN LATE ON
WEDNESDAY. FINALLY...A PERIPHERAL EFFECT OF SYSTEM MOVING ACROSS
THE OHIO VALLEY WILL BE THAT A DEEP LAYER OF NORTHEAST WINDS WILL
DEVELOP AFTER 06Z WEDNESDAY AND PERSIST UNTIL ABOUT 06Z THURSDAY.
DESPITE A SOMEWHAT FAVORABLE OVERWATER FETCH...LOW-LEVEL
INSTABLITY NOT IMPRESSIVE. LOOKS LIKE THE MOST FAVORABLE WINDOW
FOR MARGINAL LES WOULD BE FROM 06Z TO 18Z WEDNESDAY. MAINTAINED
LOW CHANCE POPS ALONG THE LAKESHORE ESPECIALLY FROM KEWAUNEE
SOUTHWARD.

MEDIUM RANGE MODELS STILL HINTING AT ANOTHER SOUTHERN STREAM SYSTEM
TO EVOLVE OVER THE SOUTHERN MISSISSIPPI VALLEY FRIDAY...IN ADDITION
TO ANOTHER WEAKER PEICE OF NORTHERN STREAM ENERGY FORECAST TO
WORK ACROSS THE NORTHERN PLAINS. ALTHOUGH CONFIDENCE STILL LOW
WITH RESPECT ANY INTERACTION WITH THESE FEATURES...IT APPEARS THAT
A BROAD WAA REGIME DOWNSTREAM MAY GENERATE SOME LIGHT SNOW OVER
THE CENTRAL MISSISSIPPI VALLEY THAT COULD SPREAD INTO WISCONSIN
SOMETIME ON FRIDAY. FOR NOW...MAINTAINED CHANCE POPS FRIDAY INTO
SATURDAY.
&&

.AVIATION...THICKENING MID TO HIGH LEVEL CLOUDS VFR CONDITIONS
WILL CONTINUE OVERNIGHT.  A WEAK DISTURBANCE DROPPING OVER THE
NORTHERN GREAT LAKES REGION ON MONDAY WILL BRING LIGHT SNOW TO
MUCH OF WISCONSIN. CIGS WILL LOWER TO MVFR LEVELS AS THE LIGHT
SNOW SPREADS FROM WEST TO EAST ACROSS THE STATE. VSBYS MAY LOWER
TO MVFR LEVELS FOR A FEW HOURS IN THE MORNING OVER NORTHERN
WISCONSIN.

TDH
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








AREA FORECAST DISCUSSION...corrected

NWS TALLAHASSEE FL

 1017 AM EST Mon Dec 24 2012

...The Potential for a Significant Severe Weather Outbreak (with
Damaging Winds and Possible Tornadoes) exists across the Region from
later Christmas Day into Wednesday...with a higher end "Slight Risk"
issued from the Storm Prediction Center...

.NEAR TERM [Through Tonight]...
The large scale pattern is highlighted by a longwave trough over Wrn
states and a shortwave trough exiting LWR MS Valley. In Srn stream
weak ridging persists over NE Gulf region. Weak impulses
(shortwaves) embedded in a jet streak seen on satellite moving Ewd
from TX to SE Coast. This generating mid/high clouds and apparently
virga from radar returns but also sct rain moving across mainly
coastal panhandle. At surface,above shortwave impulses have
commenced generating a meso-low across SE LA coast with ample Gulf
moisture spreading NEWD ahead of this low across WRN/Cntrl Gulf
region. Low over WRN TN Valley with cold front SWD across NRN MS to
this meso low over LA then to SE TX. Warm front extends from TN
Valley low SEWD thru Cntrl AL and into Gulf of Mex. High well of NE
FL/SE GA coast. All this reflected in local dew points that continue
to moisten especially west of the Apalachicola River, to 60-63
degrees or 20 to 25 degrees wetter than same time yesterday across
Panhandle.

During rest of today, the shortwave trough will move rapidly ESE
from LWR MS Valley into Gulf region. As a result, at surface, TN
Valley low will ride E then NEWD towards New England into tonight.
This will serve to drag trailing cold front into Wrn/Cntrl gulf
coast becoming stationary tonight and at same time allow meso low to
lift NEWD with warm front also lifting NEWD towards local area. This
combination will help to continue to evacuate much of the very dry
air which had become entrenched across our region over the weekend,
and it will spread scattered showers, and eventually some
thunderstorms across the CWA today. The best chances for rain will
be across the NW third of the region. Although current rain low top,
and the threat for strong storms today is low, peripheral influence
of the approaching shortwave, rising dew points and warming and
destabilization of warm sector especially if higher deck vacates as
implied in SE AL this morning will bring elevated and some surface
based convection and gusty winds mainly to our NW most counties
later today. RUC13 shows 180-200 j/kg here. Based on current radar
trend, will modify POP grids with higher pops for our panhandle
counties and adjacent waters. Will go with sharp 70-20% NW-SE pop
gradient. This clearly demonstrated on local WRF. Within warm
sector, temps will be warmer today with highs approaching 70 degrees
in many locations.

Tonight, strong shortwave begins to move out of SRN Plains and
sharpen SEWD. This briefly resulting in enhanced ridging over local
region allowing cold front to stall with a brief lull in the
weather yielding low pops tonight. Shwrs and tstms will commence
around sunrise as low pivots newd and isentropic lift and elevated
convection commences ahead of lifting warm front to be shortly
replaced by surface based convection (see below). Expect lows in the
low to mid 50s. Will insert fog into GRIDS ern counties after
06z..also expect fog or mist with the light rain across wrn counties
but will exclude for now from grids.

At the area beaches today, increasing onshore flow will create a
High Risk for Rip Currents along the Panhandle Coast, with a
Moderate Risk of Rip Currents at the Big Bend Beaches. A High Risk
is expected at all of our beaches that experience surf on Tuesday,
and a High Surf Advisory will likely be needed on Tuesday night into
Wednesday. A coastal flood advisory remains possible;e, however
latest guidance shows that best chance of flooding would occur at
low tide from Apalachicola to Cedar Key (The area most susceptible
to flooding) so will hold off on issuing this product.

&&

.SHORT TERM [Tuesday Through Wednesday]...After this weak low
pressure system moves through our region, a MUCH more potent Upper
Level Shortwave will begin its rapid approach from the NW. This
shortwave, which has just entered the Pacific Northwest early this
morning, will quickly dive southeastward to a position near northern
TX by Christmas morning. This Upper Low will continue to charge
eastward then northeastward through the short term period, spawning
a rapidly deepening Sfc Low which will head off to our NE later on
Christmas into at least the first half of Wednesday, eventually
sweeping a strong Cold Front through the region. This system will
produce a very highly sheared environment which will be conducive
for Severe Weather (mainly in the form of damaging wind gusts and
possible tornadoes). Although the "primary" threat for severe storms
will occur along the squall line itself on Tuesday Night into
Wednesday (where the "timing" may keep the greatest severe
probabilities just off to our west), we are still a bit concerned
for potential Discrete SuperCell development along the initial Warm
Frontal boundary, which will move through parts of the FL Panhandle
and Southeast AL on Tuesday Afternoon. It is this Warm Front (where
the low level winds will back to the E and SE) which could be the
focus of the greatest Tornadic threat. At this time, however, we
believe that the greatest threat will be just to the West of our CWA
Christmas Afternoon, but all interests are urged to keep abreast of
this rapidly developing situation and be prepared to take action if
needed.

&&

.AVIATION...
[Through 12z Tuesday] Mainly VFR conditions are expected to prevail
with southwest winds around 10 knots developing during the day with
gusts a bit higher. However, an increase in shower activity and
possibly some isolated convection is expected to develop during the
late morning and afternoon hours and spread from from NW-SE as an
upper level disturbance moves through. The greatest chances for rain
and any storms with gusty winds will be around ECP and DHN with rain
starting around 16z and tempo for tstms 18z-22z. at ABY, tstms will
probably hold off. the rain will shut off after sundown thru rest of
period except for possibly chc shra/isold tstm at DHN around 12z.
MVFR CIGs will commence around 08z with possible IFR cigs
developing near sunrise.

&&

.MARINE...Onshore winds and seas will be on the increase to high
end cautionary levels across the western legs of the coastal waters
rest of today, and moderate levels to the east ahead of a weak
approaching frontal system. This front will stall north of the
coastal waters tonight as a much stronger low pressure system begins
to develop off to our west. South to Southwest winds ahead of this
front will quickly ramp up to strong Small Craft Advisory levels, as
a squall line of showers and and thunderstorms (some strong to
severe), pushes eastward across the marine area Tuesday Night and
Wednesday. Also, a period of Gale Force winds cannot be ruled out at
this time, before winds shift to the northwest and slowly subside.
Much lighter winds and lower seas are expected by late this week.

&&

.FIRE WEATHER...
Moist and unsettled conditions are expected through the middle of
the week as a strong storm system moves through the region. Drier
air will move in behind the front, but red flag conditions are not
currently expected for the next several days.

&&

.HYDROLOGY...Much of the region is expected to receive between 1 and
2 inches of rainfall during the next few days (except around 0.5"
over the SE FL Big Bend). This may cause some minor rises along area
rivers, but due to low flows in area basins, no significant rises
are expected at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   70  55  72  59  66 / 20  20  50  60  60
Panama City   70  61  71  61  63 / 40  20  60  70  50
Dothan        69  56  70  55  59 / 50  30  80  80  50
Albany        68  53  70  56  61 / 40  20  70  80  60
Valdosta      69  52  70  57  65 / 20  10  40  60  70
Cross City    70  53  72  58  69 / 10  10  20  40  70
Apalachicola  69  60  70  63  66 / 30  20  40  60  60

&&

.TAE WATCHES/WARNINGS/ADVISORIES...

FL...High Risk of Rip Currents today along the beaches of Walton,
     Bay, and Gulf Counties.
GA...None.
AL...None.
GM...None.

&&

$$
NEAR TERM...Block/Gould
SHORT TERM...Gould
AVIATION...Block
MARINE...Block
FIRE WEATHER...DVD
HYDROLOGY...Gould









AREA FORECAST DISCUSSION...UPDATED

NWS PEACHTREE CITY GA

 1020 AM EST MON DEC 24 2012

.UPDATE...
QUICK UPDATE TO ADD TSRA TO FCST GRIDS TODAY...MAINLY OVER AREAS
ALONG AND SOUTH OF I-20. RAP MUCAPE ANALYSIS CONTINUES TO SHOW
VALUES OF 200-400 J/KG OVER THE AREA. RADAR AND NLDN CG DATA ALSO
INDICATE MOSTLY ELEVATED TSRA BUT A LITTLE MORE VIGOROUS THAN
EXPECTED. WHILE NEAR TERM THIS WILL DIMINISH AS THE WEAK SHORT
WAVE AND FRONT MOVE TO THE EAST...WILL HAVE TO INCLUDE CONVECTION
THROUGH MOST OF THE DAY. REST OF FCST LOOKS GOOD. FAVORABLE
PATTERN FOR DENSE FOG AFTER MIDNIGHT TONIGHT. HAVE TWEAKED GRIDS
FURTHER TO SHOW THIS. BETWEEN THE RAIN TODAY...DENSE FOG TONIGHT
...SHRA/TSRA XMAS DAY AND SVR QLCS EVENT TUE NIGHT/WED MORNING...
TRAVEL WILL BE NEGATIVELY IMPACTED FOR A WHILE!

MEDIA...COULD YOU PLEASE ASK RESIDENTS CHECK THE BATTERIES IN THEIR
NOAA WX RADIOS OR INSTALL A SEVERE WEATHER ALERTING APP ON THEIR
SMART PHONES? TUE NIGHT COULD BE A LONG NIGHT. THANKS.

SNELSON

&&

.PREV DISCUSSION... /ISSUED 615 AM EST MON DEC 24 2012/

SHORT TERM /TODAY THROUGH TUESDAY/...

SHORT WAVE MOVES ACROSS THE AREA TODAY AS A WEAK COLD FRONT MOVES
INTO N GA AND BECOMES STATIONARY ACROSS THE N-CENTRAL GA AREA
TONIGHT BEFORE MOVING N AS A WARM FRONT ON TUESDAY.

RAIN/SHOWERS CURRENTLY MOVING ACROSS N GA AND INTO W GA...WILL
CONTINUE ACROSS MUCH OF THE AREA TODAY...DIMINISHING DURING THE
AFTERNOON HOURS FROM W TO E. WHILE YOU CAN NOT COMPLETELY RULE OUT A
A BRIEF THUNDERSTORM...MUCAPES ARE RUNNING LESS THAN 400 AND NO
LIGHTNING HAS BEEN OBSERVED SO FAR. PASSAGE OF THE SHORT WAVE LOOKS
TO CREATE A LULL OF PRECIP POTENTIAL TONIGHT WITH ONLY SMALL CHANCES
OF LIGHT RAIN ACROSS CENTRAL GA. HOWEVER WIDESPREAD FOG IS EXPECTED
TO DEVELOP AND WE WILL NEED TO WATCH FOR POSSIBLE DENSE FOG.

AS THE NEXT SURFACE LOW PRESSURE SYSTEM MOVES ACROSS THE LOWER MS
VALLEY ON TUESDAY...RAIN/SHOWERS WILL DEVELOP ACROSS THE AREA
THROUGH THE DAY ON TUESDAY...POSSIBLY STARTING ACROSS PORTIONS OF
CENTRAL GA LATE TONIGHT. INSTABILITY IS LOW FOR TUESDAY SO
THUNDERSTORM POTENTIAL IS LOW.

FORECAST HIGH TEMPERATURES ARE RUNNING SLIGHTLY BELOW NORMAL AT AHN
TO 5 DEGREES ABOVE NORMAL AT CSG. FORECAST HIGH TEMPERATURES ARE
RUNNING 2-8 DEGREES ABOVE ON TUESDAY AND WILL BE HIGHLY DEPENDENT ON
THE RAIN AND WARM FRONT. FORECAST LOW TEMPERATURES RUNNING 7-14
DEGREES ABOVE NORMAL TONIGHT.

OVERALL CONFIDENCE IS MEDIUM TO HIGH.

BDL

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

.SEVERE WEATHER LIKELY CHRISTMAS NIGHT...

EXTENDED PERIOD INITIALIZES QUITE ACTIVE FOR CHRISTMAS NIGHT WITH
THE INCREASING LIKELIHOOD OF SEVERE WX ACROSS THE AREA. A MODERATE
RISK OF SEVERE STORMS HAS NOW BEEN POSTED BY SPC WITH SLIGHT RISK
ENCOMPASSING MOST OF WEST GEORGIA FOR DAY 2. MODELS IN EXCELLENT
AGREEMENT IN SHOWING A DEVELOPING 995 LOW OVER THE TENNESSEE
VALLEY PROGRESSING NNE...LEAVING THE LOCAL AREA IN THE WARM SECTOR
BY 06Z WED WITH DEWPOINTS LIKELY IN THE UPPER 50S TO LOWER 60S.
ALTHOUGH RESULTANT CAPE VALUES WILL NOT BE AS HIGH AS LOCATIONS TO
THE WEST...EXPECT DYNAMICS OF SYSTEM ALONE INCLUDING IMPRESSIVE
DIFFLUENT PATTERN ALOFT TO COMPENSATE LACK OF CONVECTIVE FORCING.
SHEAR WILL NOT BE AN ISSUE WITH THIS SYSTEM WITH A 60 KT 850MB JET
TRAVERSING THE AREA AND 0-1KM HELICITY OF 400 M2/S2 TO 600 M2/S2.

AS IS MOST TIMES THE CASE...INSTABILITY WILL BE THE KEY AND MODELS
DO SHOW A DROP OFF AS SYSTEM MOVES THROUGH THE LOCAL AREA. FEEL AT
THIS POINT THIS WILL MEAN A LIMIT TO OVERALL EXTENT OF SEVERE
WEATHER EVENT BUT WILL NOT PRECLUDE SEVERE WEATHER ENTIRELY. IN
FACT ANY TORNADOES ABLE TO FORM WILL BE CAPABLE OF ACHIEVING F2
STATUS OR PERHAPS GREATER AND EXHIBIT LONG LIFE CYCLES GIVEN STP
OVER 2 INDICATED BY MOST MODELS. TOOK A LOOK AT THE CIPS ANALOG
SITE FOR THIS EVENT AND SEEMS MOST SIMILAR EVENTS DID PRODUCE
SEVERE WEATHER OVER THE AREA INCLUDING TORNADOES WITH THE EMPHASIS
ON THE SOUTHERN CWA.

SYSTEM PROGRESSES RAPIDLY EAST AND DISCOUNTING SLOWER NAM12 FOR
NOW AS IT SEEMS AN OUTLIER. WRAPAROUND IS VERY SHALLOW WITH THIS
SYSTEM BUT ENOUGH FORCING TO WARRANT A MIX FOR THE FIRST PART OF
WED NIGHT. NEXT SYSTEM SLATED FOR NEXT SAT WITH THE ECMWF THE MOST
AGGRESSIVE BUT BOTH MODELS TARGETING THE SOUTHERN TIER FOR
HIGHEST POPS AND HAVE CONFIGURED LONG TERM GRIDS AS SUCH.

DEESE

AVIATION...
12Z UPDATE...
MAIN CONCERN WILL BE LOWERING OF CEILINGS TO IFR-MVFR LEVELS WITH
PRECIP AS IT MOVES ACROSS THE AREA TODAY. LOW CONFIDENCE FORECAST
FOR WHEN AND HOW LONG BUT POTENTIAL IS THERE. SMALL CHANCES FOR
BRIEF THUNDERSTORMS BUT NO CONFIDENCE FOR WHERE AND WHEN THEY
COULD AFFECT THE TAF SITES. SURFACE WINDS VARYING AROUND SOUTH AT
10 KTS OR LESS AND LIGHT AND VARIABLE TONIGHT. EXCELLENT POTENTIAL
FOR IFR OR LIFR CONDITIONS TONIGHT DUE TO FOG.

//ATL CONFIDENCE...12Z UPDATE...
MEDIUM TO HIGH CONFIDENCE FOR WINDS.
LOW TO MEDIUM CONFIDENCE ALL OTHER ELEMENTS.

BDL

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          52  41  56  49 / 100  20 100 100
ATLANTA         56  48  60  50 / 100  20 100 100
BLAIRSVILLE     49  42  55  47 / 100  20 100 100
CARTERSVILLE    56  41  58  48 / 100  20 100 100
COLUMBUS        63  52  66  52 /  80  30 100 100
GAINESVILLE     50  42  54  47 / 100  20 100 100
MACON           60  48  63  55 /  90  30 100  90
ROME            56  42  59  51 / 100  20 100 100
PEACHTREE CITY  58  43  61  49 / 100  20 100 100
VIDALIA         63  53  68  56 /  50  30  70  70

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...SNELSON
LONG TERM....01
AVIATION...SNELSON






AREA FORECAST DISCUSSION

NWS CHICAGO/ROMEOVILLE IL

 812 AM CST MON DEC 24 2012

.DISCUSSION...
334 AM CST

FORECAST CHALLENGES THIS MORNING INCLUDE PRECIP POTENTIAL
TODAY...PERSISTENT MARGINAL LAKE EFFECT SET-UP TONIGHT THROUGH
TUESDAY NIGHT...THEN THE BOXING DAY STORM PROGGED TO GIVE OUR AREA A
GLANCING BLOW (LITERALLY AND FIGURATIVELY!).

PAIR OF SHORTWAVE TROUGHS MOVING EAST THIS MORNING...ONE LOOKING
FAIRLY VIGOROUS IN SATELLITE IMAGERY OVER SOUTHERN MINNESOTA WITH
THE OTHER IN THE RED RIVER VALLEY. SOUTHERN WAVE IS PROGGED TO LIFT
ENE INTO THE OHIO VALLEY TODAY AS SOUTHERN MN VORT SLIDES ESE INTO
WI. SOME OF THE GUIDANCE SUGGESTS THAT THE NORTHERN STREAM WAVE
COULD PULL THE PRECIP WITH THE SOUTHERN STREAM NORTHWARD ENOUGH TO
CLIP OUR SE COUNTIES THIS MORNING. FARTHER NORTH DEPTH OF THE
MOISTURE IS DEFINITELY LACKING...THOUGH MODELS ARE FAIRLY INSISTENT
ON DEEPENING THE SATURATED/MOIST LAYER LATER THIS MORNING INTO THE
AFTERNOON. NOT OVERLY EXCITED ABOUT PRECIP POTENTIAL AND PLAN TO
JUST CARRY SLIGHT CHANCE OF FLURRIES OR FRDZ FOR NORTHWEST CWA.

AS THIS WAVE APPROACHES TODAY FORECAST SOUNDINGS SUGGEST THAT
INVERSION HEIGHTS WILL RISE A BIT AND SETS THE STAGE FOR A MARGINAL
LAKE EFFECT SET-UP STARTING LATER THIS AFTERNOON AND GENERALLY
CONTINUING WITH PERSISTENT NE WINDS THROUGH TUESDAY NIGHT.
LAKE-850MB DELTA-T VALUES ARE PROGGED TO BE SOMEWHAT FAVORABLE
(15-17C)...BUT INVERSION HEIGHTS ARE NOTHING TO GET TINGLY ABOUT
GENERALLY STAYING BELOW 6KFT. IN ADDITION...TEMPS AT THE TOP OF THE
LAKE INDUCED CONVECTIVE LAYER ARE ONLY PROGGED TO BE -8C TO -10C
WHICH SUGGESTS VERY LOW PROB OF ICE NUCLEI IN THE CLOUDS. SO WHAT
LAKE EFFECT PRECIP DOES FORM SHOULD NOT BE SIGNIFICANT AND PROBABLY
MORE TINY SNOW GRAINS GIVEN THE ANTICIPATED LACK OF ICE IN THE
CLOUDS. SHIP OBS AND SATELLITE DATA SUGGEST THAT LAKE SST ARE
GENERALLY IN THE MID 40S...SO WITH A WIND OFF THE LAKE AIR TEMPS
NEAR THE LAKE WILL PROBABLY HANG OUT JUST ABOVE THE FREEZING MARK
CUTTING DOWN ON CHANCE OF ANY LIGHT ACCUMS. WHILE I EXPECT THERE
WILL LIKELY BE LIGHT LAKE EFFECT PRECIP AROUND THINK THE CHANCES OF
MEASURABLE PRECIP ARE LOW AND HAVE CUT BACK ON POPS.

ATTENTION THEN TURNS TO THE POWERFUL SOUTHERN STREAM SYSTEM PROGGED
TO RESULT IN SURFACE CYCLONE SPINNING UP OVER TEXAS TUESDAY BEFORE
LIFTING NORTHEAST INTO THE UPPER OHIO VALLEY BY MIDDAY
WEDNESDAY...THEN RE-FORMING AS SECONDARY CYCLOGENESIS TAKES PLACE
ALONG THE MID ATLANTIC COAST. SYSTEM SHOULD BE ABLE TO DRAG A
FORMIDABLE SLUG OF MOISTURE NORTHWARD INTO DEVELOPING DEFORMATION
ZONE WHICH IS PROGGED TO REACH THE SE 1/3 TO 1/4 OF OUR CWA. BUFKIT
FORECAST SOUNDINGS FROM KLAF SUGGEST THAT THIS SYSTEM MAY NOT BE THE
MOST EFFICIENT SNOW PRODUCER WITH DEEP ISOTHERMAL LAYER AROUND -5C
FROM THE SURFACE TO OVER 700MB AND A FAIRLY SHALLOW FAVORABLE
DENDRITIC GROWTH LAYER. IN ADDITION...T/H CROSS SECTIONS SHOW STRONG
OMEGA WILL BE ABOVE THE MOST FAVORED SNOW GROWTH REGION.
FINALLY...SURFACE TEMPS ALSO LOOK MARGINAL AND POSSIBLY FLIRTING
WITH 32F OR JUST ABOVE OUTSIDE OF THE HEAVIER PRECIP WHICH WILL ALSO
TEND TO LIMIT ACCUMS AND BLOW-ABILITY OF THE SNOW. BASED ON CURRENT
FORECAST TRACK AND WHAT COULD BE A BIT GENEROUS 10:1 SLR USING A
CONSENSUS QPF VALUE THERE STILL LOOKS TO BE THE POTENTIAL FOR
COUPLE/FEW INCHES OF SNOW OVER FAR SE CWA WITH AMOUNTS QUICKLY
TAPERING OFF TO THE NORTHWEST. STRONG WINDS ARE LIKELY TO RESULT IN
A WIND WHIPPED SNOW AND COULD SEE THE EVENTUAL NEED FOR A FEW OF OUR
SE COUNTIES TO POTENTIAL GET A WINTER WX ADVISORY AS THE EVENT NEARS.

LAKE EFFECT/ENHANCEMENT POTENTIAL DOES EXIST ON WEDNESDAY...HOWEVER
THERMODYNAMICALLY THE SET-UP DOES NOT IMPROVE MUCH WEDNESDAY. BUT
WITH THE LIKELY ADDITION OF ICE INTO THE CLOUDS VIA MOISTURE BEING
FLUNG NORTH AROUND THE PERIPHERY OF THE OHIO VALLEY LOW AS WELL AS
SOME ADDED LARGE SCALE ASCENT FELT COMFORTABLE MAINTAINING LIKELY
POPS WEDNESDAY DOWNWIND OF THE LAKE. HOWLING NORTHEAST WIND OFF THE
UNSEASONABLY MILD LAKE WEDNESDAY COULD MAKE IT HARD FOR TEMPS TO GET
BELOW FREEZING WHICH WOULD AGAIN CUT DOWN ON OUR ACCUMULATION
POTENTIAL IN THE CITY.

SOMEWHAT UNSETTLED PATTERN LIKELY TO CONTINUE INTO THE WEEKEND WITH
ANOTHER SHORTWAVE APPROACHING FRI NIGHT INTO SATURDAY. AT THIS
DISTANCE MEDIUM RANGE MODELS ARE SHOWING THIS SYSTEM TO BE ANYTHING
TO WRITE HOME ABOUT...BUT CONSIDERING CHICAGO`S SEASONAL SNOWFALL
TOTAL IS 0.3" I SUPPOSE EVEN AN INCH MIGHT AT LEAST WORTHY OF AN
EMAIL HOME! ECMWF IS TRYING TO DRAG A SLUG OF ARCTIC AIR DOWN LATE
IN THE WEEKEND...BUT THE ECMWF HAS BEEN DOING THAT A LOT IN THE DAYS
5+ TIME FRAME ONLY TO BACK OFF ON THE INTENSITY OF THE COLD AS
"EVENT" NEARS. DIDNT MAKE ANY REAL CHANGES TO GOING FORECAST FOR THE
WEEKEND WHICH FEATURES NEAR/SLIGHT BELOW AVG TEMPS AND LITTLE PRECIP
AFTER FRI NIGHT/SAT MORNING SYSTEM PASSES BY.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS THROUGH THE REMAINDER OF THE DAY AND TONIGHT.

* SMALL CHANCE FOR SOME -DZ...BUT TOO SMALL A CHANCE TO INCLUDE IN
  TAFS AT THIS TIME.

* NNELY WINDS BECOMING NLY THIS AFTERNOON. SPEEDS REMAINING LESS
  THAN 10KT.

//DISCUSSION...UPDATED 12Z...

AN UPPER TROUGH CONTINUES TO MOVE E ACROSS MID AMERICA EARLY THIS
MORNING...LOCATED OVER THE MS VALLEY AT 11Z. WITHING THIS TROUGH
ARE TWO DISTINCT FEATURES. IN THE NORTHERN PORTION MOVING E
ACROSS THE UPPER MIDWEST IS A MID LEVEL LOW WHILE IN THE SOUTHERN
SECTION A SHORT WAVE IS MOVING E OVER THE OZARKS. THE MAIN
SURFACE FEATURE...A WEAK SURFACE LOW IN FAR WESTERN KY...IS
ASSOCIATED WITH THE SOUTHERN SHORT WAVE.

THE STRATUS/STRATOCU HAD CLEARED FROM ORD AND MDW DURING THE
PREDAWN...THOUGH BASED ON RUC13 OUTPUT WHICH HAD THE CLEARING
TREND WELL HANDLED...BRINGS THE LOW LEVEL MOISTURE BACK ACROSS
THE ORD AND MDW AREAS 16Z-17Z SO HAVE MVFR CEILINGS RETURNING
AROUND THAT TIME.

PROSPECTS FOR ANY PRECIPITATION OUTSIDE OF ANYTHING VERY LIGHT
AND INSIGNIFICANT ARE LOW. WITH A LACK OF MOISTURE FOR ABOUT 4KM
ABOVE THE LOW LEVEL MOISTURE TRAPPED UNDER THE INVERSION AND WITH
THE UPPER TROUGH PASSING OVER AND TO THE E OF THE LOCAL AREA BY
18Z HAVE ELIMINATED ALL MENTION OF PRECIPITATION FROM 12Z TAF
ISSUANCE.

A LARGE RIDGE OF HIGH PRESSURE CENTERED OVER NORTHERN ALBERTA WILL
CONTINUE TO SLOWLY BUILD S ACROSS THE PLAINS TODAY AND TONIGHT.
THIS SHOULD RESULT IN LOCAL SURFACE WINDS CURRENTLY FROM THE ENE
TO BACK TO A NNE TO N DIRECTION BY EARLY TO MID AFTERNOON.

TRS

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN DZ CHANCES.

* MEDIUM CONFIDENCE IN CIG AND WIND DIRECTION TRENDS.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SLIGHT CHANCE OF LIGHT LAKE EFFECT SNOW AND
ASSOCIATED MVFR CIGS AND VSBYS.

WEDNESDAY...LAKE EFFECT ENHANCED SNOW LIKELY WITH ASSOCIATED IFR
CONDITIONS.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...CHANCE OF LIGHT SNOW WITH MVFR/OCCASIONAL IFR.

SUNDAY...VFR

TRS

&&

.MARINE...
216 AM CST

A RIDGE OF HIGH PRESSURE CENTERED OVER THE NORTHERN CANADIAN
PRAIRIE WILL CONTINUE TO BUILD S ACROSS THE NORTHERN AND CENTRAL
PLAINS TO THE LOWER MS VALLEY TODAY KEEPING A MODERATE TO FRESH
BREEZE ON THE NORTH PART OF THE LAKE THROUGH TUESDAY NIGHT.
WINDS ON THE SOUTH PORTION OF THE LAKE INCREASE TO FRESH TO
STRONG BREEZES TONIGHT AND UP TO NEAR GALE OR GALE FORCE BY
WEDNESDAY AS LOW PRESSURE DEEPENS AS IT MOVES FROM E TX TO THE
LOWER MS VALLEY TUESDAY. THE LOW THE TURNS NE TOWARD TO THE
TENNESSEE VALLEY TUESDAY NIGHT THEN MOVES EAST TO EASTERN VIRGINA
DURING WEDNESDAY.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$





AREA FORECAST DISCUSSION

NWS CHICAGO/ROMEOVILLE IL

 625 AM CST MON DEC 24 2012

.DISCUSSION...
334 AM CST

FORECAST CHALLENGES THIS MORNING INCLUDE PRECIP POTENTIAL
TODAY...PERSISTENT MARGINAL LAKE EFFECT SET-UP TONIGHT THROUGH
TUESDAY NIGHT...THEN THE BOXING DAY STORM PROGGED TO GIVE OUR AREA A
GLANCING BLOW (LITERALLY AND FIGURATIVELY!).

PAIR OF SHORTWAVE TROUGHS MOVING EAST THIS MORNING...ONE LOOKING
FAIRLY VIGOROUS IN SATELLITE IMAGERY OVER SOUTHERN MINNESOTA WITH
THE OTHER IN THE RED RIVER VALLEY. SOUTHERN WAVE IS PROGGED TO LIFT
ENE INTO THE OHIO VALLEY TODAY AS SOUTHERN MN VORT SLIDES ESE INTO
WI. SOME OF THE GUIDANCE SUGGESTS THAT THE NORTHERN STREAM WAVE
COULD PULL THE PRECIP WITH THE SOUTHERN STREAM NORTHWARD ENOUGH TO
CLIP OUR SE COUNTIES THIS MORNING. FARTHER NORTH DEPTH OF THE
MOISTURE IS DEFINITELY LACKING...THOUGH MODELS ARE FAIRLY INSISTENT
ON DEEPENING THE SATURATED/MOIST LAYER LATER THIS MORNING INTO THE
AFTERNOON. NOT OVERLY EXCITED ABOUT PRECIP POTENTIAL AND PLAN TO
JUST CARRY SLIGHT CHANCE OF FLURRIES OR FRDZ FOR NORTHWEST CWA.

AS THIS WAVE APPROACHES TODAY FORECAST SOUNDINGS SUGGEST THAT
INVERSION HEIGHTS WILL RISE A BIT AND SETS THE STAGE FOR A MARGINAL
LAKE EFFECT SET-UP STARTING LATER THIS AFTERNOON AND GENERALLY
CONTINUING WITH PERSISTENT NE WINDS THROUGH TUESDAY NIGHT.
LAKE-850MB DELTA-T VALUES ARE PROGGED TO BE SOMEWHAT FAVORABLE
(15-17C)...BUT INVERSION HEIGHTS ARE NOTHING TO GET TINGLY ABOUT
GENERALLY STAYING BELOW 6KFT. IN ADDITION...TEMPS AT THE TOP OF THE
LAKE INDUCED CONVECTIVE LAYER ARE ONLY PROGGED TO BE -8C TO -10C
WHICH SUGGESTS VERY LOW PROB OF ICE NUCLEI IN THE CLOUDS. SO WHAT
LAKE EFFECT PRECIP DOES FORM SHOULD NOT BE SIGNIFICANT AND PROBABLY
MORE TINY SNOW GRAINS GIVEN THE ANTICIPATED LACK OF ICE IN THE
CLOUDS. SHIP OBS AND SATELLITE DATA SUGGEST THAT LAKE SST ARE
GENERALLY IN THE MID 40S...SO WITH A WIND OFF THE LAKE AIR TEMPS
NEAR THE LAKE WILL PROBABLY HANG OUT JUST ABOVE THE FREEZING MARK
CUTTING DOWN ON CHANCE OF ANY LIGHT ACCUMS. WHILE I EXPECT THERE
WILL LIKELY BE LIGHT LAKE EFFECT PRECIP AROUND THINK THE CHANCES OF
MEASURABLE PRECIP ARE LOW AND HAVE CUT BACK ON POPS.

ATTENTION THEN TURNS TO THE POWERFUL SOUTHERN STREAM SYSTEM PROGGED
TO RESULT IN SURFACE CYCLONE SPINNING UP OVER TEXAS TUESDAY BEFORE
LIFTING NORTHEAST INTO THE UPPER OHIO VALLEY BY MIDDAY
WEDNESDAY...THEN RE-FORMING AS SECONDARY CYCLOGENESIS TAKES PLACE
ALONG THE MID ATLANTIC COAST. SYSTEM SHOULD BE ABLE TO DRAG A
FORMIDABLE SLUG OF MOISTURE NORTHWARD INTO DEVELOPING DEFORMATION
ZONE WHICH IS PROGGED TO REACH THE SE 1/3 TO 1/4 OF OUR CWA. BUFKIT
FORECAST SOUNDINGS FROM KLAF SUGGEST THAT THIS SYSTEM MAY NOT BE THE
MOST EFFICIENT SNOW PRODUCER WITH DEEP ISOTHERMAL LAYER AROUND -5C
FROM THE SURFACE TO OVER 700MB AND A FAIRLY SHALLOW FAVORABLE
DENDRITIC GROWTH LAYER. IN ADDITION...T/H CROSS SECTIONS SHOW STRONG
OMEGA WILL BE ABOVE THE MOST FAVORED SNOW GROWTH REGION.
FINALLY...SURFACE TEMPS ALSO LOOK MARGINAL AND POSSIBLY FLIRTING
WITH 32F OR JUST ABOVE OUTSIDE OF THE HEAVIER PRECIP WHICH WILL ALSO
TEND TO LIMIT ACCUMS AND BLOW-ABILITY OF THE SNOW. BASED ON CURRENT
FORECAST TRACK AND WHAT COULD BE A BIT GENEROUS 10:1 SLR USING A
CONSENSUS QPF VALUE THERE STILL LOOKS TO BE THE POTENTIAL FOR
COUPLE/FEW INCHES OF SNOW OVER FAR SE CWA WITH AMOUNTS QUICKLY
TAPERING OFF TO THE NORTHWEST. STRONG WINDS ARE LIKELY TO RESULT IN
A WIND WHIPPED SNOW AND COULD SEE THE EVENTUAL NEED FOR A FEW OF OUR
SE COUNTIES TO POTENTIAL GET A WINTER WX ADVISORY AS THE EVENT NEARS.

LAKE EFFECT/ENHANCEMENT POTENTIAL DOES EXIST ON WEDNESDAY...HOWEVER
THERMODYNAMICALLY THE SET-UP DOES NOT IMPROVE MUCH WEDNESDAY. BUT
WITH THE LIKELY ADDITION OF ICE INTO THE CLOUDS VIA MOISTURE BEING
FLUNG NORTH AROUND THE PERIPHERY OF THE OHIO VALLEY LOW AS WELL AS
SOME ADDED LARGE SCALE ASCENT FELT COMFORTABLE MAINTAINING LIKELY
POPS WEDNESDAY DOWNWIND OF THE LAKE. HOWLING NORTHEAST WIND OFF THE
UNSEASONABLY MILD LAKE WEDNESDAY COULD MAKE IT HARD FOR TEMPS TO GET
BELOW FREEZING WHICH WOULD AGAIN CUT DOWN ON OUR ACCUMULATION
POTENTIAL IN THE CITY.

SOMEWHAT UNSETTLED PATTERN LIKELY TO CONTINUE INTO THE WEEKEND WITH
ANOTHER SHORTWAVE APPROACHING FRI NIGHT INTO SATURDAY. AT THIS
DISTANCE MEDIUM RANGE MODELS ARE SHOWING THIS SYSTEM TO BE ANYTHING
TO WRITE HOME ABOUT...BUT CONSIDERING CHICAGO`S SEASONAL SNOWFALL
TOTAL IS 0.3" I SUPPOSE EVEN AN INCH MIGHT AT LEAST WORTHY OF AN
EMAIL HOME! ECMWF IS TRYING TO DRAG A SLUG OF ARCTIC AIR DOWN LATE
IN THE WEEKEND...BUT THE ECMWF HAS BEEN DOING THAT A LOT IN THE DAYS
5+ TIME FRAME ONLY TO BACK OFF ON THE INTENSITY OF THE COLD AS
"EVENT" NEARS. DIDNT MAKE ANY REAL CHANGES TO GOING FORECAST FOR THE
WEEKEND WHICH FEATURES NEAR/SLIGHT BELOW AVG TEMPS AND LITTLE PRECIP
AFTER FRI NIGHT/SAT MORNING SYSTEM PASSES BY.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* RETURN OF MVFR CEILINGS

* POTENTIAL FOR LIGHT PRECIPITATION THIS MORNING

TRS

//DISCUSSION...UPDATED 12Z...

AN UPPER TROUGH CONTINUES TO MOVE E ACROSS MID AMERICA EARLY THIS
MORNING...LOCATED OVER THE MS VALLEY AT 11Z. WITHING THIS TROUGH
ARE TWO DISTINCT FEATURES. IN THE NORTHERN PORTION MOVING E
ACROSS THE UPPER MIDWEST IS A MID LEVEL LOW WHILE IN THE SOUTHERN
SECTION A SHORT WAVE IS MOVING E OVER THE OZARKS. THE MAIN
SURFACE FEATURE...A WEAK SURFACE LOW IN FAR WESTERN KY...IS
ASSOCIATED WITH THE SOUTHERN SHORT WAVE.

THE STRATUS/STRATOCU HAD CLEARED FROM ORD AND MDW DURING THE
PREDAWN...THOUGH BASED ON RUC13 OUTPUT WHICH HAD THE CLEARING
TREND WELL HANDLED...BRINGS THE LOW LEVEL MOISTURE BACK ACROSS
THE ORD AND MDW AREAS 16Z-17Z SO HAVE MVFR CEILINGS RETURNING
AROUND THAT TIME.

PROSPECTS FOR ANY PRECIPITATION OUTSIDE OF ANYTHING VERY LIGHT
AND INSIGNIFICANT ARE LOW. WITH A LACK OF MOISTURE FOR ABOUT 4KM
ABOVE THE LOW LEVEL MOISTURE TRAPPED UNDER THE INVERSION AND WITH
THE UPPER TROUGH PASSING OVER AND TO THE E OF THE LOCAL AREA BY
18Z HAVE ELIMINATED ALL MENTION OF PRECIPITATION FROM 12Z TAF
ISSUANCE.

A LARGE RIDGE OF HIGH PRESSURE CENTERED OVER NORTHERN ALBERTA WILL
CONTINUE TO SLOWLY BUILD S ACROSS THE PLAINS TODAY AND TONIGHT.
THIS SHOULD RESULT IN LOCAL SURFACE WINDS CURRENTLY FROM THE ENE
TO BACK TO A NNE TO N DIRECTION BY EARLY TO MID AFTERNOON.

TRS


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

*MEDIUM CONFIDENCE ALL FORECAST ELEMENTS.

TRS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SLIGHT CHANCE OF LIGHT LAKE EFFECT SNOW AND
ASSOCIATED MVFR CIGS AND VSBYS.

WEDNESDAY...LAKE EFFECT ENHANCED SNOW LIKELY WITH ASSOCIATED IFR
CONDITIONS.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...CHANCE OF LIGHT SNOW WITH MVFR/OCCASIONAL IFR.

SUNDAY...VFR

TRS

&&

.MARINE...
216 AM CST

A RIDGE OF HIGH PRESSURE CENTERED OVER THE NORTHERN CANADIAN
PRAIRIE WILL CONTINUE TO BUILD S ACROSS THE NORTHERN AND CENTRAL
PLAINS TO THE LOWER MS VALLEY TODAY KEEPING A MODERATE TO FRESH
BREEZE ON THE NORTH PART OF THE LAKE THROUGH TUESDAY NIGHT.
WINDS ON THE SOUTH PORTION OF THE LAKE INCREASE TO FRESH TO
STRONG BREEZES TONIGHT AND UP TO NEAR GALE OR GALE FORCE BY
WEDNESDAY AS LOW PRESSURE DEEPENS AS IT MOVES FROM E TX TO THE
LOWER MS VALLEY TUESDAY. THE LOW THE TURNS NE TOWARD TO THE
TENNESSEE VALLEY TUESDAY NIGHT THEN MOVES EAST TO EASTERN VIRGINA
DURING WEDNESDAY.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$









AREA FORECAST DISCUSSION

NWS PITTSBURGH PA

 619 AM EST MON DEC 24 2012

.SYNOPSIS...
A WEAK SURFACE LOW WILL PUSH ACROSS THE AREA TODAY...BRINGING A
LIGHT WINTRY MIX OF PRECIPITATION ACROSS THE RIDGES AND NORTH OF
PITTSBURGH WITH MOSTLY RAIN ELSEWHERE. WEAK HIGH PRESSURE WILL PASS
NORTHWEST OF THE AREA AND ALLOW FOR A MOSTLY DRY CHRISTMAS DAY. THE
NEXT LOW WILL THE BRING A WINTRY MIX ACROSS THE AREA WEDNESDAY INTO
THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A PAIR OF SHORT WAVES
UPSTREAM ALONG THE SAME AXIS OF A BROAD UPPER TROUGH. THE NORTHERN
WAVE IS THE STRONGER OF THE TWO AND IS DIVING SOUTHEASTWARD FROM THE
NORTHERN PLAINS INTO THE UPPER MIDWEST. THE SOUTHERN WAVE IS MOVING
ACROSS THE ARKLATEX REGION. IN THE LOWER LEVELS...850MB FLOW IS
SHIFTING TO MORE SOUTHWESTERLY AHEAD OF A TROUGH THAT EXTENDS FROM
LAKE MICHIGAN ACROSS THE TENNESSEE VALLEY. WEAK WAA AHEAD OF THIS
FEATURE HAS INITIATED...WITH 850 TEMPS AT -1C TO 1C ACROSS THE AREA
AND A WARMER TEMPS AT 2-3C SURGING NORTHWARD INTO SOUTHERN WV. AT
THE SURFACE...A 1009MB LOW IS MOVING INTO WESTERN TN WITH A FRONTAL
BOUNDARY EXTENDING NORTHEAST OF THIS FEATURE INTO SOUTHERN OHIO.

TODAY...THE SURFACE LOW WILL LIFT NORTHEASTWARD INTO THE OHIO
VALLEY AND PHASE WITH THE NORTHERN SHORT WAVE TROUGH AS IT REACHES
WESTERN PA AROUND 00Z TUESDAY. WEAK FORCING FROM 285-300K LAYER
ISENTROPIC LIFT...MID-LEVEL SHORT WAVE ENERGY AND THE LOW WILL BE
SUFFICIENT FOR SHOWERS TO BEGIN PUSHING IN FROM THE SOUTHWEST AROUND
15Z AND CONTINUING THROUGH MUCH OF THE DAY. A MODEL CONSENSUS
INDICATES GENERALLY A FEW HUNDREDTHS TO A TENTH OF AN INCH OF PRECIP
SOUTHWEST OF PITTSBURGH BEFORE 18Z AND THEN AN ADDITIONAL TENTH OF
AN INCH ACROSS THE AREA THROUGH 00Z. THUS...ONLY HAVE A TENTH TO A
QUARTER OF AN INCH FORECAST FOR QPF TODAY. FOR TEMPS...HAVE GONE
WITH THE WARMER NAM SOLUTION SOUTH OF PITTSBURGH AND LAMP GUIDANCE
ELSEWHERE.

FOR PRECIP TYPE TODAY...GFS/NAM/ECMWF ARE ALL IN AGREEMENT IN THE
LOW REMAINING RELATIVELY WEAK AS IT TRACKS ALONG THE OHIO RIVER.
DESPITE MODEL SIMILARITIES IN SURFACE LOW TRACK AND INTENSITY WITH
THIS INITIAL LOW...SOUNDINGS INDICATE VARYING THERMAL
PROFILES...MAKING FOR A CHALLENGING PRECIP TYPE FORECAST TODAY.

THE BEGINNING OF PRECIP HAS TRENDED SLOWER...WHICH HAS FAVORED
SURFACE TEMPS WARMING ENOUGH THIS MORNING FOR MOSTLY RAIN IN
EASTERN OHIO AND NORTHERN WV. THE EXCEPTION WOULD BE ACROSS THE
EASTERN RIDGES...WHERE COLD AIR DAMMING WILL KEEP TEMPS BELOW
FREEZING AND THUS ALLOW FOR LIGHT FREEZING RAIN AND LIGHT ICE
ACCUMULATION. 00Z THERMAL PROFILES SUPPORT MORE OF A MIX OF SLEET
AND SNOW WITH FREEZING RAIN ACROSS THE RIDGES. ALONG THE I-80
CORRIDOR...PRECIP IS FORECAST TO REMAIN MOSTLY SNOW AS DENDRITIC
GROWTH ZONE BECOMES SATURATED AND MELTING LAYER IS TOO WEAK. ANY
ICE ACCUMULATION ACROSS THE RIDGES WILL BE LIGHT...LESS THAN A
TENTH OF AN INCH. SNOW AND SLEET MAY MIX IN FOR LESS THAN AN INCH
OF ADDITIONAL ACCUMULATION FOR THE RIDGES. PRIMARILY NORTH OF
I-80...1-2 INCHES OF SNOW ACCUMULATION IS FORECAST.

PRESTON COUNTY HAS BEEN ADDED TO THE FREEZING RAIN ADVISORY THIS
MORNING...AS RADIATIONAL COOLING HAS MADE VALLEYS ESPECIALLY
SUSCEPTIBLE TO A LIGHT ICING TODAY. WILL NEED TO CONTINUE TO
MONITOR RADAR TRENDS FOR THE POSSIBLE EXPANSION OF THE ADVISORY TO
OTHER LOCATIONS.

TONIGHT...THE SURFACE LOW WILL PULL EAST OF THE AREA. GFS/NAM
MODEL SOUNDINGS SUPPORT DRIZZLE/FREEZING DRIZZLE BEHIND THE LOW TONIGHT
ACROSS THE AREA WITH A DRY DENDRITIC GROWTH ZONE. FREEZING DRIZZLE
WILL BE CONFINED TO MOSTLY LOCATIONS NORTH AND EAST OF PITTSBURGH
WITH LOWS BELOW FREEZING THERE. WITH THIS IN MIND...THE FREEZING RAIN
ADVISORY HAS BEEN EXTENDED TO MIDNIGHT TONIGHT FOR THE RIDGES OF WV/MD.
LOWS TONIGHT ARE CLOSE TO LAMP GUIDANCE...RANGING FROM THE UPPER
20S TO LOWER 30S ACROSS MOST OF THE AREA.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
MODELS ARE IN AGREEMENT THAT A FEW LINGERING SNOW SHOWERS WILL BE
POSSIBLE ACROSS THE RIDGES EARLY ON CHRISTMAS DAY AS LOW-LEVEL
MOISTURE LINGERS IN THE WAKE OF THE LOW. HOWEVER...WEAK HIGH PRESSURE
PASSING NORTHWEST OF THE AREA WILL ALLOW MOST OF THE AREA A BRIEF
RESPITE FROM PRECIPITATION BEFORE THE NEXT SYSTEM APPROACHES FROM
THE SOUTHWEST.

A MODEL CONSENSUS CURRENTLY INDICATES A DEEP TROUGH ENTERING THE
CENTRAL PLAINS ON TUESDAY AND CLOSING OFF INTO A LOW. THIS CLOSED
LOW IS PROGGED TO TRACK ACROSS THE TN VALLEY TUESDAY NIGHT INTO
WEDNESDAY. THERE ARE STILL A RANGE OF SOLUTIONS WITH THE TRACK OF
THIS SYSTEM...AND PRECIPITATION TYPE WILL BE HIGHLY DEPENDENT ON
THE TRACK AND HOW A WARM WEDGE WRAPS IN FROM THE SOUTHEAST AND AROUND
THE LOW. SOLUTIONS RANGE FROM THE COLDER ECMWF TAKING THE SURFACE LOW
SOUTHEAST OF THE RIDGES TO THE NAM TRACKING THE LOW INTO WESTERN
PA.

FUTURE FORECASTS WILL NEED TO MONITOR HOW WARM AIR WRAPS INTO THE
LOW...AS THIS WILL DRIVE THE PRECIP TYPE. CURRENT FORECAST
REFLECTS THE WARM 850MB WEDGE OF AIR ADVECTING INTO SOUTHWEST PA.
THIS WOULD LEAD TO THE PITTSBURGH METRO BEING RIGHT ON THE EDGE OF
THE HEAVY SNOW ACCUMULATION TO THE NORTH...A WINTRY MIX CHANGING
TO RAIN TO THE SOUTH...AND ICE ACCUMULATIONS BETWEEN THE TWO.
THERE IS THE POTENTIAL FOR AN INITIAL SHOT OF HEAVY ACCUMULATING
SNOW ACROSS A GOOD PORTION OF THE AREA...HOWEVER THE DURATION OF
THIS SNOW IS STILL UNCERTAIN. BEST CHANCE FOR OVER 6 INCHES LOOKS
TO BE NORTH OF PITTSBURGH...BUT WILL HOLD OFF ON A WINTER STORM
WATCH FOR NOW WITH STILL SOME UNCERTAINTY ON THE NORTHWARD
PROGRESSION OF THE WARM WEDGE...DRY SLOT...AND POTENTIAL ICE
ACCUMULATIONS. IT SHOULD HOWEVER BE NOTED THAT THIS SYSTEM HAS THE
POTENTIAL TO BRING SNOW AND ICE ACCUMULATION THAT COULD LEAD TO
SIGNIFICANT IMPACTS TO HOLIDAY TRAVEL THE DAY AFTER CHRISTMAS.

WEDNESDAY NIGHT INTO THURSDAY...THE CLOSED LOW WILL SHIFT INTO THE
MID-ATLANTIC...WITH CAA ENSUING IN ITS WAKE. THIS WILL ALLOW FOR
PRECIP TO TURN OVER TO ALL SNOW WEDNESDAY NIGHT...WITH SOME LAKE
EFFECT AND UPSLOPING SNOW SHOWERS CONTINUING INTO THE DAY ON
THURSDAY.

FOR TEMPS...HIGHS ON CHRISTMAS WILL BE NEAR NORMAL SEASONAL VALUES
WITH LITTLE THERMAL ADVECTION. WAA DEPENDENT ON THE LOW COULD
BRING TEMPS AROUND 10 DEGREES ABOVE NORMAL SOUTH OF
PITTSBURGH...WITH NEAR SEASONAL NORMALS ELSEWHERE. BEHIND THE
LOW...TEMPS WILL BE AROUND 5 DEGREES BELOW NORMAL.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
BLEND OF GEFS/NAEFS/HPC CHARTS DEPICT A HIGH PRESSURE BUILDING
INTO THURSDAY NIGHT INTO FRIDAY. SFC LOW WILL MOVE ACRS THE OH VLY
SAT...WITH AN UL TROF FOR SUN. A CHC OF SNOW SHOWERS RETURNS FOR
THESE SYSTEMS. OVERALL TEMPS EXPD TO AVG BLW NORMAL THRU THE PD.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
THICKENING HIGH CLOUDS WILL QUICKLY BE REPLACED BY LOW MVFR CIGS
ON MONDAY AFTERNOON. A RATHER DISJOINTED AREA OF DISTURBED WEATHER
WILL MOVE ACROSS THE AREA...WITH THE SOUTHERN TERMINALS FALLING
INTO A WARMER REGIME THAN THE NORTHERN TERMINALS. AS SUCH...LIGHT
RAIN WILL TRANSITION TO DRIZZLE TOMORROW NIGHT IN THE
SOUTH...WHILE LIGHT SNOW WILL END AS A PERIOD OF DRIZZLE OR
FREEZING DRIZZLE TO THE NORTH. IFR CONDITIONS ARE HIGHLY LIKELY
WITH THE PASSAGE OF THE SYSTEM AS LOW LEVEL MOISTURE SEEMS LIKELY
TO LINGER WELL BEYOND SIGNIFICANT PRECIPITATION.

.OUTLOOK.../MONDAY NIGHT THROUGH FRIDAY/...
LIGHT RAIN AND SNOW TAPERING OFF MONDAY NIGHT INTO TUESDAY MORNING
COULD BRIEFLY CAUSE MVFR CONDITIONS BEFORE VFR RETURNS FOR THE
REST OF CHRISTMAS DAY.

ANOTHER LOW PRESSURE SYSTEM APPROACHING FROM THE SOUTHWEST ON
WEDNESDAY WITH MIXED PRECIPITATION WILL CAUSE IFR CONDITIONS
THROUGH THURSDAY BEFORE VFR CONDITIONS RETURN ON FRIDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FREEZING RAIN ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ001.
OH...NONE.
PA...NONE.
WV...FREEZING RAIN ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ023-
     041.

&&

$$

SYNOPSIS...WOODRUM
NEAR TERM...WOODRUM
SHORT TERM...WOODRUM
AVIATION...FRIES





AREA FORECAST DISCUSSION

NWS STATE COLLEGE PA

 649 AM EST MON DEC 24 2012

.SYNOPSIS...
WEAK LOW PRESSURE WILL TRACK NORTHEAST UP THE OHIO RIVER VALLEY
TODAY...CROSSING THE REGION LATE TONIGHT. THIS WEATHER FEATURE WILL
BRING MOST AREAS OF CENTRAL PENNSYLVANIA JUST ENOUGH SNOW FOR A
WHITE CHRISTMAS. A RIDGE OF HIGH PRESSURE WILL FOLLOW FOR CHRISTMAS
DAY...WITH PLENTY OF CLOUDS AND LIGHT NORTHERLY WINDS. A MORE
SIGNIFICANT AND WIDESPREAD WINTER STORM WILL TAKE AIM ON THE ENTIRE
NORTHEAST U.S. FOR WEDNESDAY AND THURSDAY. THE POTENTIAL EXISTS FOR
HEAVY SNOWFALL ACROSS THE NORTHWEST HALF OF PENNSYLVANIA...WITH A
GRADUAL INCREASE IN MIXED PRECIPITATION HEADING SOUTHEAST TOWARD THE
LOWER SUSQUEHANNA VALLEY. BLUSTERY AND COLD CONDITIONS WITH
FLURRIES...AND MOUNTAIN SNOW SHOWERS WILL FOLLOW FOR THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
A SHALLOW WEDGE OF COLDER AIR HAS ADVECTED SOUTH TO COVER MUCH OF
THE REGION EARLY TODAY. SLIGHTLY MILDER/ABOVE FREEZING AIR AT 850 MB
WAS ADVANCING EAST ACROSS THE GREATER PITTSBURGH AREA ATTM...JUST
ABOVE THE NEARLY STALLED OUT...EAST TO WEST 925 MB FRONT. HIGH RES
NAM AND RUC MODELS SHOW THAT A BKN-OVC STRATO CU LAYER AROUND 2-3KFT
AGL WILL PERSIST THE NEXT FEW HOURS ACROSS THE NRN TIER COUNTIES...
BEFORE ERODING AROUND SUNRISE. HIGH CLOUDS WILL STREAM IN FROM THE
WSW AND THICKEN UP LATER THIS MORNING.

TEMPS AT DAYBREAK WILL BE COLDEST ACROSS THE SOUTHERN HALF OF THE
STATE /MAINLY IN THE LOWER 20S/...WHILE THE CLOUD BLANKET ACROSS THE
NORTH RESULTS IN SLIGHTLY WARMER MINS IN THE MID 20S.

00Z MODEL SUITE AND LATEST ENSEMBLE GUIDANCE SHOWS A HIGH
PROBABILITY FOR A LIGHT SNOWFALL OF AN INCH OR TWO ACROSS THE REGION
THIS AFTERNOON INTO TONIGHT AS A WEAK AREA OF LOW PRESSURE MOVES ENE
UP THE OHIO RIVER VALLEY. HIGH RES MODEL THERMAL/WET BULB THERMAL
PROFILES WITHIN 2 KFT AGL INDICATE THAT MUCH OF THE LIGHT PRECIP
WILL FALL IN THE FORM OF SNOW. THE LOWEST 1 KFT AGL MAY WARM BRIEFLY
INTO THE MID AND UPPER 30S ACROSS THE SOUTHEAST VALLEYS TO CAUSE THE
LIGHT SNOW TO MIX WITH LIGHT RAIN.

OTHERWISE...925-850 MB WET-BULB TEMPS WILL BE A FEW TO SVRL DEG C
BELOW ZERO FOR THE DURATION OF THIS EVENT...SUPPORT PRIMARILY SNOW.

THE ONLY LOCATION AT THIS POINT THAT WILL SEE A LAYER OF SLIGHTLY
ABOVE FREEZING AIR ALOFT WILL BE PORTIONS OF THE LAUREL HIGHLANDS.
THERE...SOME LIGHT FREEZING RAIN AND SLEET SHOULD MIX IN AT
TIMES...PERHAPS LEADING TO TREACHEROUS HOLIDAY TRAVEL. A WINTER
WEATHER ADVISORY WAS POSTED FOR SOMERSET COUNTY FROM 17Z TODAY
THROUGH 06Z CHRISTMAS.

SFC TEMPS THIS AFTERNOON IN THE LOWER TO MID 30S ACROSS MUCH OF THE
REMAINDER OF CENTRAL PENN SHOULD ALLOW TREATED/PRIMARY ROADS TO STAY
MAINLY WET AS SNOWFALL RATES SHOULD BE QUITE LIGHT...PERHAPS AROUND
0.25 INCH PER HOUR.

AFTER THE MAIN WAVE OF PRECIP COMES THROUGH EARLY THIS EVENING...
VERY WEAK FORCING AND SPOTTY LIGHT PRECIP WILL CONTINUE
OVERNIGHT...AND LLVL WINDS GO WESTERLY. THIS WILL PROLONG THE
NEAR-FREEZING TEMPS AND POSSIBILITY FOR -FZDZ ACROSS THE AREA...ESP
THE WRN MTS. ALL OF THE HIGH/COLD CLOUDS GO AWAY IMMEDIATELY AFTER
THE MAIN PUSH...SO GOOD SEEDING OF ICE CRYSTALS IS GONE AND MUCH OF
THE AREA COULD SEE PATCHY FZDZ. AGAIN...ALL TOO FAR AWAY AND MINOR
PRECIP AMOUNTS TO MAKE A CALL ON THIS YET.

TEMPS GREETING SANTA AND HIS REINDEER TEAM EARLY CHRISTMAS MORNING
WILL VARY FROM THE L20S UP NORTH...TO THE MID AND UPPER 20S ACROSS
CENTRAL AND SOUTHERN PENN.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
A WEAK RIDGE OF HIGH PRESSURE DRIFTING EAST ACROSS THE STATE WILL
PROVIDE A RATHER SHORT WINDOW OF ONLY 24-30 HOURS WITH IMPROVED
TRAVEL CONDITIONS FROM LATER CHRISTMAS MORNING INTO EARLY WEDNESDAY.

MAX TEMPS CHRISTMAS AFTERNOON WILL BE AROUND 30F ACROSS THE NW
MTNS...AND MID 30S TO LOWER 40S ELSEWHERE.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A SIGNIFICANT WINTER STORM WILL BEGIN TO STRENGTHEN ACROSS THE LOWER
MISS AND TENN VALLEYS CHRISTMAS NIGHT AND HEAD NORTHEAST...SPREADING
THE LEADING EDGE OF A LARGE SHIELD OF PRECIPITATION OVER THE SWRN
PART OF REGION DURING THE MIDDAY HOURS WEDNESDAY...AND BEGINNING
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS ELSEWHERE.

PRECIP TYPE SHOULD BE SNOW FOR AT LEAST A FEW TO SVRL HOURS IN ALL
LOCATIONS /AS 925-850 MB WET BULB TEMPS EVEN IN THE SE WILL BE -2 TO
-4C AND NOTABLY COLDER FURTHER TO THE NORTH/ THANKS TO INCREASINGLY
STRONG LLVL NORTHERLY AGEOS FLOW.

23/21Z THROUGH 24/06Z OPERATIONAL U.S. AND EURO MODEL RUNS /AND
THEIR RESPECTIVE ENSEMBLES/ ARE COMING INTO PRETTY GOOD AGREEMENT
TRACKING A DYING PRIMARY LOW NE ACROSS THE OHIO VALLEY WITH A
SECONDARY LOW RAPIDLY INTENSIFYING JUST INLAND FROM THE DELMARVA
PENINSULA LATE WEDNESDAY NIGHT.

WILL MAKE JUST SOME MINOR MODIFICATIONS TO THE PRECIP TYPE AND
AMOUNT ACROSS THE CWA FOR WEDNESDAY INTO THURSDAY.

THIS APPARENT/POTENT MILLER-B TYPE EVENT WILL EVOLVE AS THE TRANSFER
OF ENERGY TO THE DELMARVA COAST OCCURS WEDNESDAY NIGHT AT THE NOSE
OF A STRONG UPPER LEVEL JET /THAT WILL BE ROUNDING THE BASE OF THE
AMPLIFYING AND SLIGHTLY NEGATIVE TILT UPPER TROUGH/ AIMED AT THE
VA/MID ATLANTIC COAST.

WILL KEEP LAYER-CAKE PRECIP TYPES PAINTED FROM NW TO SE FOR THE
WEDNESDAY AFTERNOON/NIGHT PERIOD AS THE LATEST 06Z NAM STILL
INDICATES THAT A RATHER SHALLOW LAYER OF NEAR TO SLIGHTLY ABOVE
FREEZING AIR SURGE NWD INTO AT LEAST CENTRAL AND SRN PENN IN THE
800-750 MB LAYER AS THE ENERGY BEGINS TO TRANSFER ACROSS THE CENTRAL
APPALACHIANS.

HOWEVER...STRONG UVVEL AND DYNAMIC COOLING IN THE INCREASINGLY
DIVERGENT UPPER FLOW COULD KEEP THE PRECIP MAINLY MDT TO HVY SNOW
ACROSS THE REGION NORTH OF KAOO...KUNV AND KBGM FOR THE BULK OF THE
STORM.

QUITE A BIT OF UNCERTAINTY CONTINUES TO EXIST ON THIS KEY FEATURE
WHICH IS THE EXTENT AND DEPTH OF THE WARMER AIR INTRUSION AND ITS
ULTIMATE EFFECTS ON CENTRAL/EASTERN PORTIONS OF CWA.

THE BEST FORECAST REMAINS A LIKELY MODERATE TO HEAVY SNOWFALL ACROSS
THE NRN AND WESTERN MTNS...WITH MODERATE AMOUNTS OF SNOW/SLEET
IMPACT THE SUSQ VALLEY AND PORTIONS OF THE SCENT MTNS.

AS A RESULT OF THE HIGHLY ANOMALOUS...APPROX PLUS 4 SIGMA SERLY 850
MB JET AND 1-2 SIGMA PWATS ACCOMPANYING THIS STORM...LIQUID
EQUIVALENT QPF FOR THIS EVENT LOOKS TO BE 1-1.25 INCHES ACROSS MUCH
OF THE FCST AREA...WITH AROUND 1.5 INCHES OVER THE SOUTH AND EAST.
24/03Z SREF SHOWS A 30-50 PROBABILITY FOR STORM TOTAL PRECIP OF 2
INCHES IN OUR FAR SERN ZONES.

STORM TOTAL SNOWFALL HAS THE POTENTIAL TO BE IN THE 6-10 INCH RANGE
ACROSS THE NW/NCENT MTNS AND LAURELS...SEVERAL INCHES OF SNOW AND
SIGNIFICANT SLEET THROUGHOUT THE CENTRAL ZONES...AND A GENERAL MIXED
BAG MESS ACROSS THE LOWER SUSQ REGION...AFTER AN INITIAL PERIOD OF
SNOW. THIS CONCURS WITH HPC/S LATEST WINTER WEATHER GRAPHICS.

COLD AND BLUSTERY NORTHWEST FLOW REGIME DEVELOPS BEHIND THE
DEPARTING STORM THU AND FRI WITH CENTRAL AND SERN PENN FLURRIES AND
SCTD SNOW SHOWERS...WITH UPSLOPE SNOW AND LES IMPACTING THE LAURELS
AND NW MTNS.

ANOTHER WEAKER STORM PROGGED FOR NEXT WEEKEND LOOKS COLD ENOUGH
FOR A GENERALLY LIGHT SNOW EVENT SAT INTO SUN.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
LOW LVL MOISTURE TRAPPED BENEATH INVERSION IS CREATING MVFR STRATOCU
ACROSS THE N MTNS EARLY THIS MORNING. HOWEVER...MDLS INDICATE THIS
INVERSION AND RESULTING STRATOCU WILL BREAK UP BY LATE AM.

A LOW PRES SYSTEM RIDING UP THE OHIO VALLEY WILL SPREAD LOWERING
CLOUDS AND LGT SNOW ACROSS THE REGION THIS AFTN AND EVENING.
LATEST MDL DATA SUGGESTS A RAPID DETERIORATION IN VSBYS AS SNOW
ARRIVES ACROSS THE SOUTHERN PA AIRFIELDS BTWN 19Z-22Z...THEN
SPREADS NORTHEAST ACROSS THE REST OF CENTRAL PA BY 00Z. A 4-6 HOUR
PERIOD OF SNOW WITH VSBYS BTWN 1-3SM APPEARS LIKELY AT MOST
LOCATIONS. EVEN AFTER PRECIP WINDS DOWN LATE THIS EVENING...RESIDUAL
MOISTURE AND LGT WINDS SHOULD RESULT IN LINGERING FOG/LOW CIGS
ACROSS THE REGION.

AS LOW DEPARTS THE AREA LATE TONIGHT...EXPECT A WESTERLY BREEZE TO
DEVELOP...RESULTING IN IMPROVING CIGS/VSBYS EAST OF THE MTNS...BUT
CONTINUED LOW CIGS WHERE THE FLOW ASCENDS THE ALLEGHENIES AT BFD
AND JST.

OUTLOOK...
TUE...AM LOW CIGS POSS W MTNS.
WED...WINTRY MIX WITH LOW CIGS/VSBYS POSSIBLE.
THU...WINDY WITH WINTRY MIX/LOW CIGS POSS EARLY. PM SHSN POSS W MTNS.
FRI...NO SIG WX EXPECTED.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM NOON TODAY TO 1 AM EST TUESDAY
FOR PAZ033.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/RXR
AVIATION...FITZGERALD







AREA FORECAST DISCUSSION

NWS NASHVILLE TN

 929 AM CST MON DEC 24 2012

.UPDATE...FOR AVIATION FORECAST AT 15Z

EVEN THOUGH SURFACE LOW AND MID LEVEL SHORT WAVE ARE MOVING
THROUGH MIDDLE TENNESSEE AT 15Z SOME DRYING WILL TAKE PLACE IN THE
MID LEVELS WHILE MOISTURE IS EXPECTED TO REMAIN IN THE LOWER LEVELS.

FORECAST SOUNDINGS OFF THE LATEST RUC RUN KEEP LOW LEVEL MOISTURE
ACROSS THE MID STATE WHILE DRYING OUT MID LEVELS THROUGH A GOOD
PART OF THE DAY KEEPING MVFR AND OCCASIONAL IFR CONDTIONS AT BOTH
CLARKSVILLE AND NASHVILLE AND BASICALLY IFR CONDITIONS AT
CROSSVILLE LIKELY THROUGH THE DAYLIGHT HOURS. SATELLITE DOES SHOW
OCCASIONAL BREAKS IN THE OVERCAST (BINOVC) BUT THEY FILL IN RATHER
QUICKLY. LOW CLOUDS EXTEND ALL THE WAY BACK TO THE MISSISSIPPI
RIVER AT THIS TIME.


BOYD




&&

.AVIATION...

&&

.PREV DISCUSSION... /ISSUED 525 AM CST MON DEC 24 2012/

UPDATE...ADDED AVIATION SECTION FOR 12Z TAF`S.

AVIATION...BNA/CKV/CSV...COLD FRONT MOVING ACROSS MIDDLE
TENNESSEE THIS MORNING, BRINGING LIGHT TO MODERATE RAINFALL,
FOG, AND LOW CIGS. EXPECT IFR CONDITIONS FOR MUCH OF THE MORNING,
WITH CIGS IMPROVING DURING THE AFTERNOON AND EVENING AT BNA AND
CKV, AND REMAINING VFR OVERNIGHT. CSV WILL LIKELY EXPERIENCE LOW
CIGS THROUGHOUT THE DAY, WITH POSSIBLE LIFR CONDITIONS DEVELOPING
OVERNIGHT AS VV`S DROP TO NEAR ZERO AND VSBY AS LOW AS 1/2 MILE.

PREV DISCUSSION... /ISSUED 401 AM CST MON DEC 24 2012/

DISCUSSION...LOW PRESSURE SYSTEM CENTERED OVER THE MID MS VALLEY WILL
CONTINUE NEWD TODAY WITH RAIN CHANCES DIMINISHING DURING THE DAY.
COOLER TONIGHT WITH LOWS IN THE 30S BUT NO PRECIP EXPECTED.

NEXT SYSTEM DEVELOPS OVER TX ON TUE IN RESPONSE TO A VIGOROUS
UPPER WAVE THAT DIVES SEWD THROUGH THE ROCKIES EARLY TUE. THE SFC
LOW THEN MOVES NEWD THROUGH THE LOWER MS VALLEY TO A POSITION NEAR
MACON COUNTY EARLY WED MORNING. THIS IS A STRONG SFC LOW AND IS
PUSHING CONSIDERABLE MOISTURE AHEAD OF IT. THUS HPC IS SPITTING
OUT 1.25 TO 2.00 INCHES OF RAINFALL OVER THE AREA FOR THE DAY 1-3
TIME PERIOD. HAVE ALSO INCLUDED A MENTION OF TSTMS FOR SRN/SERN
COUNTIES ON TUE PM.

SO...HOW MUCH OF THAT RAINFALL WILL BE SNOW...APPARENTLY VERY
LITTLE. THE TRACK OF THE SFC LOW SEEMS TO BE A BIT FURTHER TO THE
WEST COMPARED WITH LAST NIGHTS RUN. THUS ANY SNOW AMOUNTS HAVE
BEEN REDUCED. IT APPEARS NOW THAT THE FAR NERN COUNTIES COULD GET
25 TO .50 INCHES OF SNOW LATE TUE NIGHT AND WED AM WITH THE NRN
CUMBERLAND PLATEAU GETTING LESS THAN A HALF INCH LATE WED AND WED
EVENING. ELSEWHERE A DUSTING IS POSSIBLE WED PM/EVE.

OF COURSE IT WILL BE TURNING COLDER FOR WED NGT AND THU WITH HIGHS
ON THU IN THE UPPER 30S TO NEAR 40 AND LOWS THU NGT IN THE MID 20S.
NO SIGNIFICANT WEATHER EXPECTED FOR THU THROUGH FRI AM.

SELY FLOW RETURNS THU NGT AS THE NEXT SYSTEM DEVELOPS OVER THE
LOWER PLAINS. MOISTURE PUSHES BACK INTO THE AREA ON FRI WITH A
CHANCE OF RAIN FOR FRI PM AND BEYOND. ONE CAUTION HERE...WITH THE
COLD AIR MASS STILL IN PLACE...IF THE PRECIP COMES IN EARLIER THAN
EXPECTED IT WOULD LIKELY HAVE A FREEZING RAIN COMPONENT.

RAIN CHANCES CONTINUE THROUGH FRI AND WILL LIKELY BE A MIXED BAG
OF RAIN AND SNOW. COLD AIR MOVES IN ON SAT WITH A CHANCE OF SNOW
IN THE MIDDLE AND EAST SECTION ON SAT NGT. HIGH PRESSURE OVER THE
AREA THROUGH SUN.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

01






AREA FORECAST DISCUSSION

NWS MILWAUKEE/SULLIVAN WI

 952 AM CST MON DEC 24 2012

.UPDATE...FREEZING DRIZZLE WEST AND SW OF MADISON IS VERY ISOLATED
AND WILL CONTINUE TO KEEP IT OUT OF THE FORECAST FOR THE AFTERNOON
WHEN TOP OF STRATUS LAYER EXTENDS UPWARD TO THE -10C LEVEL
RESULTING IN SNOW FLAKES VERSUS DRIZZLE. FOR THIS AFTERNOON...THE
NAM12 AND HRRR MODELS DEVELOP A BAND OF LIGHT SNOW NEAR AND WITHIN
THE SFC-925 MB TROUGH OVER SW WI INCLUDING
IOWA...LAFAYETTE...GREEN COUNTIES AND PORTIONS OF THE ADJACENT
COUNTIES. MAYBE A HALF AN INCH OF SNOW ACCUMULATION IN THESE
AREAS. OTHERWISE SMALL CHANCES OF SNOW OVER THE REMAINDER OF THE
AREA INCLUDING NEAR LAKE MI VIA VERY LIGHT LES.


&&

.PREV DISCUSSION... /ISSUED 405 AM CST MON DEC 24 2012/

TODAY...FORECAST CONFIDENCE IS MEDIUM.

MODELS HAVE BACKED OFF FREEZING DRIZZLE POTENTIAL AS COLUMN
MOISTENS FROM BELOW INTO THE -10C RANGE TO PROVIDE ENOUGH ICE
CRYSTALS FOR LIGHT SNOW. DRY MID LAYERS WILL LIMIT AMOUNTS...AS
BEST DEEP LAYER OMEGA WITH SHORT WAVE MOVES THROUGH THE REGION
PRIOR TO 18Z...BEFORE THE DRY LAYER SATURATES. COULD SEE SOME
SEEDER-FEEDER...BUT BEST CHANCE FOR ANY MEASURABLE QPF IS IN THE
WESTERN CWA IN REGION OF LOW-LEVEL CONVERGENCE ALONG AXIS OF
INVERTED SURFACE TROUGH.

LAKE-EFFECT SNOW SHOWER POTENTIAL ALSO HAS LESSENED AS DRY
DENDRITE GROWTH ZONE AND REDUCED FETCH LENGTH REDUCES PROBABILITY.
LOW-LEVEL LAPSE RATES ARE DECENT BUT DELTA T/S ARE CONDITIONAL SO
WILL LEAVE CHANCE PROBABILITY GOING. CLOUDS HAVE HELD OVERNIGHT
TEMPS UP AND EASTERLY FLOW SUPPORT BLENDED HIGH TEMPERATURES IN
THE MID 20S NW TO LOW TO MID 30S SOUTHEAST.

TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

LAKE-EFFECT SNOW POTENTIAL FADES DUE TO WINDS BACKING TO THE
NORTH...KEEPING ANY LAKE BANDS OFFSHORE. WILL KEEP A SLIGHT CHANCE
RIGHT ALONG THE SHORE IN THE EVENING. COLD AIR ADVECTION DROPS
OVERNIGHT LOWS TO AROUND 10 ABOVE NORTHWEST...TOT HE LOW MID 20S
RIGHT ALONG THE LAKE MICHIGAN SHORE.

CHRISTMAS DAY THROUGH WEDNESDAY NIGHT...FORECAST CONFIDENCE IS
MEDIUM.

WEST SOUTHWEST FLOW AT 500MB ON SHORT TERM MODELS CHRISTMAS DAY
GIVES WAY TO A SHORTWAVE TROUGH PASSING THROUGH LATER ON
WEDNESDAY. THIS IS IN RESPONSE TO A CLOSED UPPER LOW MOVING
NORTHEASTWARD...BUT WELL SOUTHEAST OF THE AREA. RIDGING THEN
MOVES INTO THE REGION WEDNESDAY NIGHT.

AT THE SURFACE...CANADIAN HIGH PRESSURE LINGERS ACROSS THE
NORTHERN PLAINS INTO MINNESOTA CHRISTMAS DAY AND TUESDAY
NIGHT...BEFORE A HIGH PRESSURE RIDGE AXIS LINGERS IN MINNESOTA AND
IOWA WEDNESDAY AND WEDNESDAY NIGHT. STRONG LOW PRESSURE MOVES
NORTHEAST...BUT WELL SOUTHEAST OF THE AREA WEDNESDAY. NAM/GFS HAVE
OUTER EDGE OF PRECIPITATION SHIELD JUST MISSING FAR SOUTHEAST
WISCONSIN AT 00Z THURSDAY.

MAIN ISSUE CONTINUES TO BE LAKE EFFECT SNOW IN FAR SOUTHEAST
WISCONSIN FOR CHRISTMAS DAY THROUGH WEDNESDAY NIGHT.
MILWAUKEE/KENOSHA FORECAST SOUNDINGS FROM NAM/GFS CONTINUE TO SHOW
NORTHEAST LOW LEVEL FLOW...WITH MOISTURE AND PERSISTENT LOW LEVEL
CONVERGENCE PER GFS SURFACE TO 850MB FRONTOGENESIS RESPONSE.
FAVORABLE DELTA T VALUES OF 13 TO 16 DEGREES CELSIUS ARE
EXPECTED.

CHANCES FOR THESE LAKE EFFECT SNOW SHOWERS CHRISTMAS DAY/TUESDAY
NIGHT AND WEDNESDAY NIGHT HAVE LOWERED...AS THE LOW LEVEL MOISTURE
IS QUESTIONABLE WITH THE -10 DEGREE CELSIUS LEVEL NOT BEING
TAPPED. THIS WOULD RESULT IN CLOUDS WITH A FEW LIGHT SNOW
SHOWERS...WHICH WOULD NOT DROP ACCUMULATING SNOW PER LAKE EFFECT
SNOW FLOW CHART.

BEST SHOT IS WEDNESDAY...WITH THE BEST LOW LEVEL MOISTURE TAPPING
THE -10 DEGREE CELSIUS ICE CRYSTAL LAYER...AND MORE MID LEVEL
MOISTURE TO USE WITH PASSING SYSTEM TO THE SOUTHEAST. THIS SHOULD
RESULT IN ON AND OFF LIGHT LAKE EFFECT SNOW SHOWERS...ESPECIALLY
AROUND AND SOUTH OF MILWAUKEE. THESE LAKE EFFECT BANDS CAN BE
TRICKY TO FORECAST THIS FAR OUT...SO SOME MODIFICATION OF THE
FORECAST MAY OCCUR.

LAKE EFFECT SNOW FLOW CHART/SNOW TO LIQUID RATIOS SUGGESTS LIGHT
ACCUMULATIONS OF UP TO AN INCH WEDNESDAY SOUTH OF MILWAUKEE...WITH
LOWER AMOUNTS ELSEWHERE NEAR THE LAKE. THESE AMOUNTS COULD BE
HIGHER IF BAND PERSISTS ACROSS A LOCALIZED AREA...SO STAY TUNED TO
THE FORECAST.

THE REST OF THE AREA SHOULD SEE QUIET WEATHER...UNDER MOSTLY
CLOUDY SKIES. TEMPERATURES WILL CONTINUE TO BE AROUND OR JUST
BELOW SEASONAL NORMALS DURING THIS PERIOD.

THURSDAY THROUGH SUNDAY...FORECAST CONFIDENCE IS MEDIUM.

ECMWF/GFS BOTH SHOW A WEAK HIGH MOVING THROUGH THE REGION
THURSDAY...BRINGING QUIET WEATHER. THEY THEN GENERALLY SHOW A
SHORTWAVE TROUGH MOVING THROUGH THE REGION FRIDAY AND FRIDAY
NIGHT...WITH ANOTHER FOR SATURDAY INTO EARLY SATURDAY NIGHT.

A WEAK SURFACE LOW DEVELOPS IN THE CENTRAL PLAINS THURSDAY...AND
MOVES NORTHEAST ACROSS NORTHERN ILLINOIS FRIDAY NIGHT. THE ECMWF
IS MORE AGGRESSIVE WITH QPF THURSDAY NIGHT...WITH THE GFS/ECMWF
THEN IN GENERAL AGREEMENT WITH QPF FRIDAY INTO SATURDAY NIGHT.

USED CONSENSUS APPROACH WITH POPS AND TEMPERATURES IN THIS
PERIOD...WITH CHANCES FOR LIGHT SNOW AND COOL TEMPERATURES. HIGH
PRESSURE SLIDING INTO THE NORTHERN PLAINS SHOULD THEN BRING DRY
AIR INTO THE REGION SUNDAY.

AVIATION/12Z TAFS/...

WILL KEEP MVFR/IFR CONDITIONS GOING RIGHT THROUGH THE FORECAST
PERIOD AS STUBBORN LOW-LEVEL MOISTURE HANGS OVER REGION. FREEZING
DRIZZLE POTENTIAL TODAY HAS BEEN REDUCED WITH FORECAST SOUNDINGS
SHOWING MOISTENING UP FROM BELOW INTO THE -10C LEVEL...WHICH WOULD
PRODUCE SMALL ICE CRYSTALS VERSUS SUPER-COOLED DROPLETS. STILL A
CHANCE THIS MORNING WITH DEEP SYNOPTIC LIFT CROSSING THE REGION THIS
MORNING BUT NOT HIGH ENOUGH TO GO CATEGORICAL SO WILL LEAVE AS A
TEMPO ALONG WITH LIGHT SNOW.

DRY MID-LAYERS WILL LIMIT ANY SNOW AMOUNTS...WITH THE BEST CHANCE OF
MEASURABLE MAINLY IN THE SOUTHWEST FORECAST AREA CLOSE TO THE AXIS
OF INVERTED SURFACE TROUGH. WILL AGAIN LEAVE AS TEMPO VERSUS
CATEGORICAL. CONDITIONAL 850MB-WATER SURFACE TEMPERATURE
DIFFERENTIAL AND LITTLE TO NO MOISTENING ABOVE THE -10C LEVEL ON
FORECAST SOUNDINGS WILL LIMIT LAKE-EFFECT SNOW POTENTIAL AT KMKE AND
KENW.

MARINE...

WINDS AND WAVES WILL APPROACH SMALL CRAFT ADVISORY LEVELS
TUESDAY...AND WILL LIKELY REACH CRITERIA TUESDAY NIGHT WITH
INCREASING NORTHEAST WINDS AS PRESSURE GRADIENT TIGHTENS OVER REGION
AS LOW PRESSURE MOVES THROUGH TO THE SOUTH OF THE WESTERN GREAT
LAKES. THERE IS A CHANCE FOR LAKE-EFFECT SNOW SHOWERS TODAY IN THE
NEARSHORE WATERS...WITH THE CHANCE MOVING OUT TOWARD MID-LAKE BY
THIS EVENING AS WINDS TURN TO THE NORTH.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$

UPDATE...GEHRING
TODAY/TONIGHT AND AVIATION/MARINE...REM
TUESDAY THROUGH SUNDAY...GEHRING







AREA FORECAST DISCUSSION...UPDATED

NWS PEACHTREE CITY GA

 138 PM EST MON DEC 24 2012

.PREV DISCUSSION... /ISSUED 1020 AM EST MON DEC 24 2012/

UPDATE...
QUICK UPDATE TO ADD TSRA TO FCST GRIDS TODAY...MAINLY OVER AREAS
ALONG AND SOUTH OF I-20. RAP MUCAPE ANALYSIS CONTINUES TO SHOW
VALUES OF 200-400 J/KG OVER THE AREA. RADAR AND NLDN CG DATA ALSO
INDICATE MOSTLY ELEVATED TSRA BUT A LITTLE MORE VIGOROUS THAN
EXPECTED. WHILE NEAR TERM THIS WILL DIMINISH AS THE WEAK SHORT
WAVE AND FRONT MOVE TO THE EAST...WILL HAVE TO INCLUDE CONVECTION
THROUGH MOST OF THE DAY. REST OF FCST LOOKS GOOD. FAVORABLE
PATTERN FOR DENSE FOG AFTER MIDNIGHT TONIGHT. HAVE TWEAKED GRIDS
FURTHER TO SHOW THIS. BETWEEN THE RAIN TODAY...DENSE FOG TONIGHT
..SHRA/TSRA XMAS DAY AND SVR QLCS EVENT TUE NIGHT/WED MORNING...
TRAVEL WILL BE NEGATIVELY IMPACTED FOR A WHILE!

MEDIA...COULD YOU PLEASE ASK RESIDENTS CHECK THE BATTERIES IN THEIR
NOAA WX RADIOS OR INSTALL A SEVERE WEATHER ALERTING APP ON THEIR
SMART PHONES? TUE NIGHT COULD BE A LONG NIGHT. THANKS.

SNELSON

PREV DISCUSSION... /ISSUED 615 AM EST MON DEC 24 2012/

SHORT TERM /TODAY THROUGH TUESDAY/...

SHORT WAVE MOVES ACROSS THE AREA TODAY AS A WEAK COLD FRONT MOVES
INTO N GA AND BECOMES STATIONARY ACROSS THE N-CENTRAL GA AREA
TONIGHT BEFORE MOVING N AS A WARM FRONT ON TUESDAY.

RAIN/SHOWERS CURRENTLY MOVING ACROSS N GA AND INTO W GA...WILL
CONTINUE ACROSS MUCH OF THE AREA TODAY...DIMINISHING DURING THE
AFTERNOON HOURS FROM W TO E. WHILE YOU CAN NOT COMPLETELY RULE OUT A
A BRIEF THUNDERSTORM...MUCAPES ARE RUNNING LESS THAN 400 AND NO
LIGHTNING HAS BEEN OBSERVED SO FAR. PASSAGE OF THE SHORT WAVE LOOKS
TO CREATE A LULL OF PRECIP POTENTIAL TONIGHT WITH ONLY SMALL CHANCES
OF LIGHT RAIN ACROSS CENTRAL GA. HOWEVER WIDESPREAD FOG IS EXPECTED
TO DEVELOP AND WE WILL NEED TO WATCH FOR POSSIBLE DENSE FOG.

AS THE NEXT SURFACE LOW PRESSURE SYSTEM MOVES ACROSS THE LOWER MS
VALLEY ON TUESDAY...RAIN/SHOWERS WILL DEVELOP ACROSS THE AREA
THROUGH THE DAY ON TUESDAY...POSSIBLY STARTING ACROSS PORTIONS OF
CENTRAL GA LATE TONIGHT. INSTABILITY IS LOW FOR TUESDAY SO
THUNDERSTORM POTENTIAL IS LOW.

FORECAST HIGH TEMPERATURES ARE RUNNING SLIGHTLY BELOW NORMAL AT AHN
TO 5 DEGREES ABOVE NORMAL AT CSG. FORECAST HIGH TEMPERATURES ARE
RUNNING 2-8 DEGREES ABOVE ON TUESDAY AND WILL BE HIGHLY DEPENDENT ON
THE RAIN AND WARM FRONT. FORECAST LOW TEMPERATURES RUNNING 7-14
DEGREES ABOVE NORMAL TONIGHT.

OVERALL CONFIDENCE IS MEDIUM TO HIGH.

BDL

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

SEVERE WEATHER LIKELY CHRISTMAS NIGHT...

EXTENDED PERIOD INITIALIZES QUITE ACTIVE FOR CHRISTMAS NIGHT WITH
THE INCREASING LIKELIHOOD OF SEVERE WX ACROSS THE AREA. A MODERATE
RISK OF SEVERE STORMS HAS NOW BEEN POSTED BY SPC WITH SLIGHT RISK
ENCOMPASSING MOST OF WEST GEORGIA FOR DAY 2. MODELS IN EXCELLENT
AGREEMENT IN SHOWING A DEVELOPING 995 LOW OVER THE TENNESSEE
VALLEY PROGRESSING NNE...LEAVING THE LOCAL AREA IN THE WARM SECTOR
BY 06Z WED WITH DEWPOINTS LIKELY IN THE UPPER 50S TO LOWER 60S.
ALTHOUGH RESULTANT CAPE VALUES WILL NOT BE AS HIGH AS LOCATIONS TO
THE WEST...EXPECT DYNAMICS OF SYSTEM ALONE INCLUDING IMPRESSIVE
DIFFLUENT PATTERN ALOFT TO COMPENSATE LACK OF CONVECTIVE FORCING.
SHEAR WILL NOT BE AN ISSUE WITH THIS SYSTEM WITH A 60 KT 850MB JET
TRAVERSING THE AREA AND 0-1KM HELICITY OF 400 M2/S2 TO 600 M2/S2.

AS IS MOST TIMES THE CASE...INSTABILITY WILL BE THE KEY AND MODELS
DO SHOW A DROP OFF AS SYSTEM MOVES THROUGH THE LOCAL AREA. FEEL AT
THIS POINT THIS WILL MEAN A LIMIT TO OVERALL EXTENT OF SEVERE
WEATHER EVENT BUT WILL NOT PRECLUDE SEVERE WEATHER ENTIRELY. IN
FACT ANY TORNADOES ABLE TO FORM WILL BE CAPABLE OF ACHIEVING F2
STATUS OR PERHAPS GREATER AND EXHIBIT LONG LIFE CYCLES GIVEN STP
OVER 2 INDICATED BY MOST MODELS. TOOK A LOOK AT THE CIPS ANALOG
SITE FOR THIS EVENT AND SEEMS MOST SIMILAR EVENTS DID PRODUCE
SEVERE WEATHER OVER THE AREA INCLUDING TORNADOES WITH THE EMPHASIS
ON THE SOUTHERN CWA.

SYSTEM PROGRESSES RAPIDLY EAST AND DISCOUNTING SLOWER NAM12 FOR
NOW AS IT SEEMS AN OUTLIER. WRAPAROUND IS VERY SHALLOW WITH THIS
SYSTEM BUT ENOUGH FORCING TO WARRANT A MIX FOR THE FIRST PART OF
WED NIGHT. NEXT SYSTEM SLATED FOR NEXT SAT WITH THE ECMWF THE MOST
AGGRESSIVE BUT BOTH MODELS TARGETING THE SOUTHERN TIER FOR
HIGHEST POPS AND HAVE CONFIGURED LONG TERM GRIDS AS SUCH.

DEESE

&&

.AVIATION...
18Z UPDATE...
MAIN PROBLEM IS IFR/LIFR CIGS/VSBYS THROUGH TUES. IFR CIGS APPEARS
LIKELY AS ONE SYSTEM MOVES AWAY BUT STRONGER SYSTEM APPROACHING
FROM THE WEST. WILL LIKELY SEE LIFR AROUND 03Z TUES MOST PLACES.
LARGE AREA OF RAIN WILL MOVE IN FROM THE SOUTH AROUND 15Z OVER
CSG/MCN AND 19Z AT ATL METRO AIRPORTS. SOME ELEVATED INSTABILITY
AGAIN DEVELOPS TONIGHT BUT LIKELIHOOD OF TSRA NOT HIGH ENOUGH TO
JUSTIFY MENTION IN TAF. MAY HAVE TO ADD TO CSG/MCN IN LATER
ISSUANCES FOR TUES AFTERNOON. SFC WINDS WILL BECOME LIGHT THEN
EAST AROUND 13-15Z THEN GRADUALLY INCREASE TO 5 TO 10KTS.

//ATL CONFIDENCE...18Z UPDATE...
MEDIUM CONFIDENCE FOR TIMING OF IFR/LIFR CIGS.
HIGH CONFIDENCE ON ALL OTHER ELEMENTS.


SNELSON

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          52  41  56  49 / 100  20 100 100
ATLANTA         56  48  60  50 / 100  20 100 100
BLAIRSVILLE     49  42  55  47 / 100  20 100 100
CARTERSVILLE    56  41  58  48 / 100  20 100 100
COLUMBUS        63  52  66  52 /  80  30 100 100
GAINESVILLE     50  42  54  47 / 100  20 100 100
MACON           60  48  63  55 /  90  30 100  90
ROME            56  42  59  51 / 100  20 100 100
PEACHTREE CITY  58  43  61  49 / 100  20 100 100
VIDALIA         63  53  68  56 /  50  30  70  70

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...SNELSON
LONG TERM....01
AVIATION...SNELSON






AREA FORECAST DISCUSSION

NWS WAKEFIELD VA

 447 PM EST MON DEC 24 2012

.SYNOPSIS...
LOW PRESSURE AND AN ASSOCIATED FRONTAL BOUNDARY WILL TRACK ACROSS
THE MID ATLANTIC STATES THROUGH TONIGHT. WEAK HIGH PRESSURE WILL
BUILD OVER THE AREA FOR CHRISTMAS DAY. A STRONGER AREA OF LOW
PRESSURE WILL TRACK THROUGH THE TENNESSEE VALLEY CHRISTMAS NIGHT...
THEN CONTINUE ACROSS THE MID ATLANTIC WEDNESDAY INTO WEDNESDAY
EVENING...WITH ITS ASSOCIATED COLD FRONT PUSHING OFF THE COAST BY
EARLY THURSDAY MORNING.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
LATEST MSAS SFC ANALYSIS SHOWS A STATIONARY FRONTAL BOUNDARY DRAPED
ACROSS SOUTHERN VIRGINIA...AND EXTENDING NE TO DEVELOPING LOW
PRESSURE OVER THE OHIO VALLEY. WAA OUT AHEAD OF THE SFC
LOW/MID-LEVEL SHORTWAVE HAS BROUGHT SOME LIGHT RAIN TO THE REGION
TODAY (ESPECIALLY THE NORTHERN/WESTERN FA). AS THE SHORTWAVE DRAWS
CLOSER AND MOVES OVER THE AREA THIS EVENING...AM EXPECTING SPOTTY
LIGHT RAIN TO CONTINUE WITH EMPHASIS ON NORTHERN/WESTERN
LOCATIONS. THIS RAIN MAY NOT HOLD TOGETHER LONG ENOUGH TO REACH
SERN PARTS OF THE FA THROUGH THIS EVENING (DUE TO WEAKENING WAA)...
THEREFORE WILL ONLY CARRY SLIGHT CHC POPS THERE THROUGH 06Z. WILL
HOLD HOLD TO LIKELY/CATEGORICAL POPS (60-90%) FOR NORTHERN
WESTERN/AREAS THROUGH 00Z...THEN TAPER TO CHC POPS (~30%) AFTER
00Z. SHORTWAVE TROUGH AND A WEAK SFC COLD FRONT EXIT THE REGION
AFTER 06Z ALLOWING DRIER ARE TO MOVE INTO THE AREA ALOFT. MODELS
SHOWS ABUNDANT LOW-LEVEL MOISTURE REMAINING IN PLACE OVERNIGHT...
SO LOW OVERCAST (STRATUS) IS EXPECTED TO BE PREVALENT. LOWS TEMPS
TONIGHT WILL NOT BE FAR FROM CURRENT READINGS IN NW PARTS OF THE
FA. LOWS NEAR FREEZING NE TO THE LOW 40S SERN COASTAL AREAS.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
DRY WEATHER IS EXPECTED ON CHRISTMAS DAY WITH THE SKY BECOMING AT
LEAST PARTLY SUNNY...AS WEAK SFC HIGH PRESSURE BUILDS OVER THE
REGION. MAX TEMPS WILL AVERAGE A FEW DEGREES ABOVE NORMAL...
RANGING FROM THE UPR 40S NE TO THE UPR 50S INTERIOR NE NC.

NEXT STRONGER LOW PRESSURE SYSTEM WILL BE DEVELOPING INVOF LOWER MS
VALLEY CHRISTMAS NIGHT...THEN IS FORECAST TO TRACK NE INTO EASTERN
KY BY WED AFTN. AHEAD OF THIS FEATURE...MODELS ARE INDICATED A
NICE WEDGE/CAD SETUP DEVELOPING ACROSS OUR FAR WESTERN/NW COUNTIES
EARLY WED MORNING. OVERRUNNING PRECIP AHEAD OF THE NE ADVANCING
LOW WILL MAKE FOR A TRICKY FORECAST LATE TUES NIGHT/WED MORNING
DUE TO POTENTIAL FOR SOME LIGHT WINTRY PRECIP ACROSS OUR NW
COUNTIES. LATEST BUFKIT DATA SUGGEST POTENTIAL FOR A PERIOD OF
SNOW/SLEET ALONG/NORTH OF A LINE FROM FVX-OFP-XSA LINE. P-TYPE WILL
ALL DEPEND ON EXTENT OF NEAR SFC COLD AIR BY THAT TIME AND JUST
HOW QUICKLY THE CAD ERODES. FOR NOW...HAVE ADDED IN A CHC FOR SOME
SLEET/SNOW ACROSS THE NW COUNTIES WED MORNING BUT WILL NOT SPEAK
OF ANY SNOW/SLEET ACCUMULATIONS ATTM AS IT`S STILL A LOW
CONFIDENCE FORECAST. HOPEFULLY...MODELS WILL HAVE A BETTER HANDLE
ON THIS BY THIS TIME TOMORROW.

OUR ATTENTION THIS TURNS TO A SECONDARY LOW DEVELOPING ESE OF THE
MAIN UPPER LOW THAT WILL TRACK ACROSS CENTRAL VA UP INTO EASTERN
MD LATE WED AFTN INTO WED NIGHT. A WARM FRONT WILL LIFT INTO/THRU
THE FA ON WED AFTN AIDED BY INCREASING SE THEN S WINDS. MAIN AREA
OF MID LEVEL DYNAMICS TO REACH THE FA WED AFTN...AS RIBBON OF
HIGHER SFC DEWPOINTS/LOW LEVEL INSTABILITY WOULD BE SURGING NWD.
THEREFORE...THOUGH IT BEING LATE DECEMBER...CONCERN IS FOR
POSSIBLE CONVECTION AND A PERIOD OF MODERATE/HEAVY RAIN AHEAD
OF/WITH THE COLD FRONT DURING WED AFTN/EVE. QUESTIONS REMAIN WITH
REGARDS TO JUST HOW MUCH TSTM POTENTIAL WILL BE INCREASED LATE WED
DUE TO TRIPLE POINT LOW MOVING NNE THROUGH CENTRAL/EASTERN VA.
THINK GREATEST THREAT FOR STRONG/SEVERE WX WILL REMAIN SOUTH OF
OUR FA IN AREA OF GREATER INSTABILITY...BUT CANNOT RULE OUT AN
ISOLATED STRONG STORM ACROSS OUR SOUTHERN TIER COUNTIES LATE IN
THE DAY. WILL STEADILY INCREASE POPS TUES NIGHT AND BY DAYBREAK
EXPECTED TO HAVE ONGOING PRECIP ACROSS SW AREAS AND SLIGHT CHC
POPS ON THE MD EASTERN SHORE. CATEGORICAL POPS (80-100%) ALL AREAS
ON WED. LOWS TUES NIGHT IN THE LOW 30S NW TO THE MID/UPR 40S SERN
COASTAL AREAS. HIGHS WED NEAR 40 NW TO THE LOW/MID 60S SERN
COASTAL AREAS. BRUNT OF PRECIP WITH THIS SYSTEM WILL COME WED
AFTN/EVENING WHEN HAVE QPF AMOUNTS BETWEEN 0.75"-1.5" WITH LOCALLY
HIGHER AMOUNTS POSSIBLE.

SFC LOW MOVES OFFSHORE WED NIGHT WITH TRAILING UPPER LOW MOVING
ACROSS NORTHERN VA. WILL LINGER POPS ACROSS MOST AREAS THROUGH 06Z
THURS...WITH CHANCE POPS ACROSS JUST THE NORTHERN TIER COUNTIES
AFTER 06Z. LOWS IN THE MID 30S TO MID 40S. CHILLY W/NW WINDS
DEVELOP ON THURSDAY AS THE UPPER LOW DEPARTS AND DRIER AREA
RETURNS. HIGHS THURSDAY IN THE MID 40S NW TO THE LOW 50S SE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
MODELS IN RELATIVELY GOOD AGREEMENT WITH A HIGH AMPLITUDE PATTERN
ACROSS THE U.S. UPPER LEVEL ENERGY DIGS INTO THE SW US AND MOVES
NORTHEAST ACROSS THE MID ATLANTIC. THE MAIN PROBLEM FOR THE
EXTENDED IS THE DEVELOPMENT OF LOW PRESSURE FOR SATURDAY INTO
SUNDAY. HPC WAS FOLLOWING A BLEND OF THE GFS AND ECMWF FOR THIS
DEVELOPING LOW. LOOKING AT THE 12Z GFS AND ECMWF THEY NOW BECOME
CLOSER IN AGREEMENT FOR OUR AREA WITH LOW PRESSURE DEVELOPING IN
THE SOUTHEASTERN US AND MOVING OFF THE MID ATLANTIC COAST SATURDAY
INTO SUNDAY. THERE ARE STILL QUESTIONS ABOUT THE TIMING AND
LOCATION OF THIS LOW. SO WENT VERY GENERIC WITH THE PRECIPITATION
TYPE FOR THIS STORM. THE MODELS ALL AGREE ENOUGH COLD AIR IN PLACE
TO START THE NORTHWEST SECTIONS OF THE AREA WITH EITHER SNOW OR A
MIX OF RAIN AND SNOW. MOST OF THE AREA LEANED TOWARD JUST RAIN FOR
NOW. WILL HAVE TO WATCH THIS SYSTEM AS IT DEVELOPS TOWARD THE
WEEKEND. TEMPERATURE FORECAST WENT CLOSE TO BOTH GRIDDED MOS AND
HPC WHICH WERE SIMILAR. OTHER THEN THE WEEKEND STORM MAINLY A DRY
FORECAST WITH TEMPERATURES NEAR TO A LITTLE BELOW NORMAL.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
CONTINUING TO HAVE LIGHT RAIN MOVING NORTHEAST AHEAD OF A PV MAX
IN THE OHIO VALLEY. THIS PRECIPITATION WILL MOVE OFF THE COAST
AROUND 00Z TONIGHT. HOWEVER THE COLD FRONT ACCOMPANYING THE
PRECIPITATION IS QUITE WEAK AND STILL CONTAINS PLENTY OF LOW LEVEL
MOISTURE. THIS WILL CAUSE CEILINGS TO LOWER AFTER THE RAIN ENDS
AND EXPECT IFR STRATUS OVERNIGHT AT ALL THE TAF SITES. THIS IS ON
THE LOW END OF MOST STATISTICAL GUIDANCE BUT THE RAP NAM AND GFS
BUFKIT SOUNDINGS DO SUPPORT THE LOWER CLOUD DECK. PLENTY OF DRYING
ALOFT TONIGHT. THIS WILL HELP IN THE MORNING AS WINDS SHOULD
INCREASE ENOUGH AND WITH THE SUNSHINE THE LOW CLOUDS WILL BREAK UP
DURING THE MORNING WITH VFR FOR THE REMAINDER OF THE DAY.

NEXT WEATHER SYSTEM WILL BE LOW PRESSURE MOVING THROUGH WEDNESDAY
INTO THURSDAY. THIS WILL LIKELY BRING SOME IFR CONDITIONS FOR A
TIME WEDNESDAY AND WEDNESDAY NIGHT AS RAIN MOVES ACROSS THE AREA.
COULD SEE ISOLATED THUNDERSTORMS OVER SOUTHEAST VIRGINIA WEDNESDAY
AFTERNOON OR EVENING. VFR CONDITIONS RETURN DURING THURSDAY WITH
NEXT CHANCE OF LOWER CIGS AND VSBY OVER THE WEEKEND BUT STILL
PLENTY OF UNCERTAINTY ON THIS.

&&

.MARINE...
NOT MANY CHANGES NECESSARY TO ONGOING MARINE FORECAST AS OF THIS
AFTN.

LOW PRESSURE CONTINUES TO TRACK NE FROM THE OH VALLEY INTO WRN PA
THIS EVENING AND WILL PUSH OFF THE NJ COAST BY CHRISTMAS MORNING.
WEAK ONSHORE FLOW EARLY THIS EVENING WILL BECOME WESTERLY BY LATE
THIS EVENING. A BACKDOOR FRONT THEN DEVELOPS TUE AFTN INTO TUE NIGHT
PRIOR TO A WARM FRONT LIFTING NWD ON WED. THIS BACKDOOR FRONT WILL
REINFORCE A NNW-N WIND DIRECTION OVER THE WATERS DURING THIS
TIME...HOWEVER CAA WILL BE RATHER WEAK AND WIND SPEEDS SHOULD STAY
GENERALLY AOB 15 KT ALL WATERS UNTIL LATE TUE NIGHT/EARLY WED
MORNING WHEN WINDS MAY FLIRT WITH LOW-END SCA FOR BAY/RIVERS/SOUND
(15-20 KT). CONFIDENCE NOT HIGH ENOUGH YET TO HOIST FLAGS ATTM.
EXPECT BAY WAVES AVERAGING 1-2 FT AND SEAS 2-4 FT TONIGHT THROUGH
TUE EVENING.

THE WARM FRONT WILL RAPIDLY WEAKEN THE BACKDOOR FRONT ON WED AS A
STRONG AND POTENT LOW PRESSURE SYSTEM LIFTS ENE INTO THE AREA FROM
THE TN VALLEY. AS STRONG HIGH PRESSURE REMAINS IN PLACE NORTH OF THE
GREAT LAKES IN CANADA...A STRONG PRESSURE GRADIENT WILL FORM BTWN
THE TWO SYSTEMS AND ESSENTIALLY OVER THE MID ATLANTIC REGION. SINCE
FORECAST MODELS TYPICALLY UNDERCUT NE WIND SPEEDS OVER THE MARINE
AREA...HAVE MADE LITTLE TO NO CHANGE TO ONGOING FORECAST. THE MAIN
FORECAST CHALLENGE IS TO DETERMINE HOW RAPIDLY THE LOW INTENSIFIES
AND SUBSEQUENTLY THE WINDS AS THE LOW MOVES TWD THE COAST BY WED
NIGHT. STILL EXPECTING A STRONG SCA EVENT ON WED...WITH POSSIBLE
GALES A FEW HOURS EITHER SIDE OF THE FRONTAL PASSAGE (ESPECIALLY
ALONG THE COAST N OF CAPE CHARLES). SEAS LIKELY BUILD TO 7-10 FT
OVER PORTIONS OF THE COASTAL WATERS AND 4-6 FT IN THE BAY. GALES
WILL CONTINUE TO BE POSSIBLE ON THU AS WINDS SHIFT TO THE W AND THE
LOW SLIDES OFFSHORE. CAA WILL BE RATHER WEAK ON THU AND IS NOT
EXPECTED TO BE THE DRIVING INFLUENCE ON WIND SPEEDS. CONDITIONS
WILL SLOWLY SUBSIDE THROUGH THU NIGHT AS THE LOW MOVES INTO THE
CANADIAN MARITIMES...WITH SEAS SLOWER TO FOLLOW INTO FRI.

&&

.TIDES/COASTAL FLOODING...
TIDAL FLOODING IS POSSIBLE DURING THE WED AFTN THROUGH THU AFTN
HIGH TIDE CYCLES (DEPENDING ON EXACT LOCATION). MDL AND CBOFS
FORECASTS CONTINUE TO SHOW TIDAL ANOMALIES OF 0.5-1.5 FT ABOVE
NORMAL AT VARIOUS LOCATIONS THROUGHOUT THE MD/VA LOWER EASTERN
SHORE DURING THIS TIMEFRAME. AT OCEAN CITY...TIDAL ANOMALIES ARE
FLIRTING WITH MINOR FLOODING THRESHOLDS NOW. CONSIDERING THAT THE
CURRENT DATA MAY BE UNDERDONE...WILL NEED TO CONTINUE TO MONITOR
AS THE FULL MOON PHASE APPROACHES EARLY FRI MORNING.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...JDM
NEAR TERM...JDM
SHORT TERM...JDM
LONG TERM...JAB
AVIATION...LKB/JAB
MARINE...BMD
TIDES/COASTAL FLOODING...AKQ










AREA FORECAST DISCUSSION

NWS WAKEFIELD VA

 359 PM EST MON DEC 24 2012

.SYNOPSIS...
LOW PRESSURE AND AN ASSOCIATED FRONTAL BOUNDARY WILL TRACK ACROSS
THE MID ATLANTIC STATES THROUGH TONIGHT. WEAK HIGH PRESSURE WILL BUILD
OVER THE AREA FOR CHRISTMAS DAY. A STRONGER AREA OF LOW PRESSURE
WILL TRACK THROUGH THE TENNESSEE VALLEY CHRISTMAS NIGHT...THEN
CONTINUE ACROSS THE MID ATLANTIC WEDNESDAY INTO WEDNESDAY
EVENING...WITH ITS ASSOCIATED COLD FRONT PUSHING OFF THE COAST BY
EARLY THURSDAY MORNING.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATEST MSAS SFC ANALYSIS SHOWS A STATIONARY FRONTAL BOUNDARY DRAPED
ACROSS SOUTHERN VIRGINIA...AND EXTENDING NE TO DEVELOPING LOW
PRESSURE OVER THE OHIO VALLEY. WAA OUT AHEAD OF THE SFC LOW/MID-
LEVEL SHORTWAVE HAS BROUGHT SOME LIGHT RAIN TO THE REGION TODAY
(ESPECIALLY THE NORTHERN/WESTERN FA). AS THE SHORTWAVE DRAWS
CLOSER AND MOVES OVER THE AREA THIS EVENING...AM EXPECTING SPOTTY
LIGHT RAIN TO CONTINUE WITH EMPHASIS ON NORTHERN/WESTERN
LOCATIONS. THIS RAIN MAY NOT HOLD TOGETHER LONG ENOUGH TO REACH
SERN PARTS OF THE FA THROUGH THIS EVENING (DUE TO WEAKENING WAA)...
THEREFORE WILL ONLY CARRY SLIGHT CHC POPS THERE THROUGH 06Z. WILL
HOLD HOLD TO LIKELY/CATEGORICAL POPS (60-90%) FOR NORTHERN
WESTERN/AREAS THROUGH 00Z...THEN TAPER TO CHC POPS (~30%) AFTER
00Z. SHORTWAVE TROUGH AND A WEAK SFC COLD FRONT EXIT THE REGION
AFTER 06Z ALLOWING DRIER ARE TO MOVE INTO THE AREA ALOFT. MODELS
SHOWS ABUNDANT LOW-LEVEL MOISTURE REMAINING IN PLACE
OVERNIGHT...SO LOW OVERCAST (STRATUS) IS EXPECTED TO BE PREVALENT.
LOWS TEMPS TONIGHT WILL NOT BE FAR FROM CURRENT READINGS IN NW
PARTS OF THE FA. LOWS NEAR FREEZING NE TO THE LOW 40S SERN COASTAL
AREAS.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
DRY WEATHER IS EXPECTED ON CHRISTMAS DAY WITH THE SKY BECOMING AT
LEAST PARTLY SUNNY...AS WEAK SFC HIGH PRESSURE BUILDS OVER THE REGION.
MAX TEMPS WILL AVERAGE A FEW DEGREES ABOVE NORMAL...RANGING FROM THE
UPR 40S NE TO THE UPR 50S INTERIOR NE NC.

NEXT STRONGER LOW PRESSURE SYSTEM WILL BE DEVELOPING INVOF LOWER MS
VALLEY CHRISTMAS NIGHT...THEN IS FORECAST TO TRACK NE INTO EASTERN
KY BY WED AFTN. AHEAD OF THIS FEATURE...MODELS ARE INDICATED A
NICE WEDGE/CAD SETUP DEVELOPING ACROSS OUR FAR WESTERN/NW COUNTIES
EARLY WED MORNING. OVERRUNNING PRECIP AHEAD OF THE NE ADVANCING
LOW WILL MAKE FOR A TRICKY FORECAST LATE TUES NIGHT/WED MORNING
DUE TO POTENTIAL FOR SOME LIGHT WINTRY PRECIP ACROSS OUR NW
COUNTIES. LATEST BUFKIT DATA SUGGEST POTENTIAL FOR A PERIOD OF
SNOW/SLEET ALONG/NORTH OF A LINE FROM FVX-OFP-XSA LINE. P-TYPE WILL
ALL DEPEND ON EXTENT OF NEAR SFC COLD AIR BY THAT TIME AND JUST
HOW QUICKLY THE CAD ERODES. FOR NOW...HAVE ADDED IN A CHC FOR SOME
SLEET/SNOW ACROSS THE NW COUNTIES WED MORNING BUT WILL NOT SPEAK
OF ANY SNOW/SLEET ACCUMULATIONS ATTM AS IT`S STILL A LOW
CONFIDENCE FORECAST. HOPEFULLY...MODELS WILL HAVE A BETTER HANDLE ON
THIS BY THIS TIME TOMORROW.

OUR ATTENTION THIS TURNS TO A SECONDARY LOW DEVELOPING ESE OF THE MAIN
UPPER LOW THAT WILL TRACK ACROSS CENTRAL VA UP INTO EASTERN MD LATE
WED AFTN INTO WED NIGHT. A WARM FRONT WILL LIFT INTO/THRU THE FA ON
WED AFTN AIDED BY INCREASING SE THEN S WINDS. MAIN AREA OF MID LEVEL
DYNAMICS TO REACH THE FA WED AFTN...AS RIBBON OF HIGHER SFC
DEWPOINTS/LOW LEVEL INSTABILITY WOULD BE SURGING NWD. THEREFORE...THOUGH
IT BEING LATE DECEMBER...CONCERN IS FOR POSSIBLE CONVECTION AND A
PERIOD OF MODERATE/HEAVY RAIN AHEAD OF/WITH THE COLD FRONT DURING WED
AFTN/EVE. QUESTIONS REMAIN WITH REGARDS TO JUST HOW MUCH TSTM
POTENTIAL WILL BE INCREASED LATE WED DUE TO TRIPLE POINT LOW
MOVING NNE THROUGH CENTRAL/EASTERN VA. THINK GREATEST THREAT FOR
STRONG/SEVERE WX WILL REMAIN SOUTH OF OUR FA IN AREA OF GREATER
INSTABILITY...BUT CANNOT RULE OUT AN ISOLATED STRONG STORM ACROSS
OUR SOUTHERN TIER COUNTIES LATE IN THE DAY. WILL STEADILY INCREASE
POPS TUES NIGHT AND BY DAYBREAK EXPECTED TO HAVE ONGOING PRECIP
ACROSS SW AREAS AND SLIGHT CHC POPS ON THE MD EASTERN SHORE.
CATEGORICAL POPS (80-100%) ALL AREAS ON WED. LOWS TUES NIGHT IN
THE LOW 30S NW TO THE MID/UPR 40S SERN COASTAL AREAS. HIGHS WED
NEAR 40 NW TO THE LOW/MID 60S SERN COASTAL AREAS. BRUNT OF PRECIP
WITH THIS SYSTEM WILL COME WED AFTN/EVENING WHEN HAVE QPF AMOUNTS
BETWEEN 0.75"-1.5" WITH LOCALLY HIGHER AMOUNTS POSSIBLE.

SFC LOW MOVES OFFSHORE WED NIGHT WITH TRAILING UPPER LOW MOVING
ACROSS NORTHERN VA. WILL LINGER POPS ACROSS MOST AREAS THROUGH 06Z
THURS...WITH CHANCE POPS ACROSS JUST THE NORTHERN TIER COUNTIES
AFTER 06Z. LOWS IN THE MID 30S TO MID 40S. CHILLY W/NW WINDS
DEVELOP ON THURSDAY AS THE UPPER LOW DEPARTS AND DRIER AREA
RETURNS. HIGHS THURSDAY IN THE MID 40S NW TO THE LOW 50S SE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
MODELS IN RELATIVELY GOOD AGREEMENT WITH A HIGH AMPLITUDE PATTERN
ACROSS THE U.S. UPPER LEVEL ENERGY DIGS INTO THE SW US AND MOVES
NORTHEAST ACROSS THE MID ATLANTIC. THE MAIN PROBLEM FOR THE EXTENDED
IS THE DEVELOPMENT OF LOW PRESSURE FOR SATURDAY INTO SUNDAY. HPC WAS
FOLLOWING A BLEND OF THE GFS AND ECMWF FOR THIS DEVELOPING LOW.
LOOKING AT THE 12Z GFS AND ECMWF THEY NOW BECOME CLOSER IN AGREEMENT
FOR OUR AREA WITH LOW PRESSURE DEVELOPING IN THE SOUTHEASTERN US AND
MOVING OFF THE MID ATLANTIC COAST SATURDAY INTO SUNDAY. THERE ARE
STILL QUESTIONS ABOUT THE TIMING AND LOCATION OF THIS LOW. SO WENT
VERY GENERIC WITH THE PRECIPITATION TYPE FOR THIS STORM. THE MODELS
ALL AGREE ENOUGH COLD AIR IN PLACE TO START THE NORTHWEST SECTIONS
OF THE AREA WITH EITHER SNOW OR A MIX OF RAIN AND SNOW. MOST OF THE
AREA LEANED TOWARD JUST RAIN FOR NOW. WILL HAVE TO WATCH THIS SYSTEM
AS IT DEVELOPS TOWARD THE WEEKEND. TEMPERATURE FORECAST WENT CLOSE
TO BOTH GRIDDED MOS AND HPC WHICH WERE SIMILAR. OTHER THEN THE
WEEKEND STORM MAINLY A DRY FORECAST WITH TEMPERATURES NEAR TO A
LITTLE BELOW NORMAL.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
CONTINUING TO HAVE LIGHT RAIN MOVING NORTHEAST AHEAD OF A PV MAX
IN THE OHIO VALLEY. THIS PRECIPITATION WILL MOVE OFF THE COAST
AROUND 00Z TONIGHT. HOWEVER THE COLD FRONT ACCOMPANYING THE
PRECIPITATION IS QUITE WEAK AND STILL CONTAINS PLENTY OF LOW LEVEL
MOISTURE. THIS WILL CAUSE CEILINGS TO LOWER AFTER THE RAIN ENDS
AND EXPECT IFR STRATUS OVERNIGHT AT ALL THE TAF SITES. THIS IS ON
THE LOW END OF MOST STATISTICAL GUIDANCE BUT THE RAP NAM AND GFS
BUFKIT SOUNDINGS DO SUPPORT THE LOWER CLOUD DECK. PLENTY OF DRYING
ALOFT TONIGHT. THIS WILL HELP IN THE MORNING AS WINDS SHOULD
INCREASE ENOUGH AND WITH THE SUNSHINE THE LOW CLOUDS WILL BREAK UP
DURING THE MORNING WITH VFR FOR THE REMAINDER OF THE DAY.

NEXT WEATHER SYSTEM WILL BE LOW PRESSURE MOVING THROUGH WEDNESDAY
INTO THURSDAY. THIS WILL LIKELY BRING SOME IFR CONDITIONS FOR A
TIME WEDNESDAY AND WEDNESDAY NIGHT AS RAIN MOVES ACROSS THE AREA.
COULD SEE ISOLATED THUNDERSTORMS OVER SOUTHEAST VIRGINIA WEDNESDAY
AFTERNOON OR EVENING. VFR CONDITIONS RETURN DURING THURSDAY WITH
NEXT CHANCE OF LOWER CIGS AND VSBY OVER THE WEEKEND BUT STILL
PLENTY OF UNCERTAINTY ON THIS.

&&

.MARINE...
WEAK COLD FRONT NOW DROPPING THROUGH NORTHERN PORTIONS OF THE MARINE
AREA...SHIFTING WINDS TO THE N. THUS FAR WIND SPEEDS HAVE BEEN 10 KT
OR LESS...AND EVEN W/ SOME INCREASE EXPECTED...SCA CONDITIONS ARE
NOT ANTICIPATED. BOUNDARY STALLS/DISSIPATES OVER SE VA/NE NC LATER
TODAY AS LOW PRESSURE TRACKS NE FROM THE OHIO VALLEY TO PA BY THIS
EVENING...AND OFF THE NJ COAST CHRISTMAS MORNING. WINDS WILL SHIFT
BACK TO THE SE AND THEN THE SW LATER TONIGHT AND ONCE AGAIN TURN
NORTHERLY DURING THE DAY CHRISTMAS. WIND SPEEDS NOT EXPECTED TO
REACH SCA THRESHOLDS DUE TO THE LACK OF COLD AIR MAKING IT SOUTH
INTO THE REGION (ALTHOUGH A FEW HRS WORTH OF WINDS GUSTING CLOSE TO
20 KT WILL BE POSSIBLE W/ THE FRONT EARLY TUE. BAY WAVES AVG 1-2 FT
AND SEAS 2-4 FT THROUGH TUE EVENING.

ON WED...A MUCH MORE POTENT SYSTEM WILL LIFT ENE FROM THE TENNESSEE
VALLEY...AS STRONG HIGH PRESSURE REMAINS IN PLACE NORTH OF THE GREAT
LAKES IN CANADA. THIS PATTERN YIELDS A STRONG PRESSURE GRADIENT AND
TYPICALLY MODELS ARE UNDERDONE OVER THE MARINE AREA W/ NE
WINDS...PARTICULARLY W/ RAPID INTENSIFICATION OF THE SFC LOW AS IT
MOVES TOWARDS THE COAST BY WED NIGHT. EXPECT AT LEAST A STRONG SCA
EVENT ON WED...WITH GALES A GOOD POSSIBILITY ALONG THE COAST
(ESPECIALLY N OF CAPE CHARLES). SEAS LIKELY BUILD TO 8-10 FT OVER
PORTIONS OF THE COASTAL WATERS AND 3-5 FT IN THE BAY. GALES WILL
CONTINUE TO BE POSSIBLE ON THU AS WINDS SHIFT TO THE W AS THE LOW
SLIDES OFFSHORE. COLD AIR ADVECTION IS NOT ALL THAT STRONG THOUGH SO
IT MAY NOT BE REAL LONG-LIVED.

TIDAL FLOODING IS ALSO POSSIBLE BY WED/WED NIGHT...MDL AND CBOFS
GUIDANCE IS SHOWING ANOMALIES UP TO 1.5 FT AT OCEAN CITY (AND 1 FT
OR LESS ELSEWHERE). ALTHOUGH THIS WOULD NOT YIELD EVEN MINOR
FLOODING...IT IS PROBABLY A BIT UNDERDONE AS THE GUIDANCE TENDS TO
BE BEYOND 36 HRS. WILL CONTINUE TO MONITOR.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...TMG/JDM
NEAR TERM...JDM
SHORT TERM...JDM
LONG TERM...JAB
AVIATION...LKB/JAB
MARINE...
TIDES/COASTAL FLOODING...







AREA FORECAST DISCUSSION

NWS WAKEFIELD VA

 118 PM EST MON DEC 24 2012

.SYNOPSIS...
LOW PRESSURE AND AN ASSOCIATED FRONTAL BOUNDARY WILL TRACK ACROSS
THE MID ATLANTIC STATES TODAY INTO TONIGHT. WEAK HIGH PRESSURE
WILL BUILD OVER THE AREA FOR CHRISTMAS DAY. A STRONGER AREA OF
LOW PRESSURE WILL TRACK THROUGH THE TENNESSEE VALLEY CHRISTMAS
NIGHT...THEN CONTINUE ACROSS THE MID ATLANTIC WEDNESDAY INTO
WEDNESDAY EVENING...WITH ITS ASSOCIATED COLD FRONT PUSHING OFF
THE COAST BY EARLY THURSDAY MORNING.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WEAK LO PRES CURRENTLY MOVING INTO THE LWR OH VLY AND TN VLY WILL
TRACK ENE TODAY INTO TNGT PUSHING A WARM FRONT THEN A COLD FRONT
ACRS THE REGION. ASSOCIATED MOISTURE AXIS TO SWING (W-E) ACRS THE
FA TODAY INTO THIS EVENG...WITH HIGHEST POPS (70-100%) OVR THE NRN
AND WRN PORTIONS OF THE AREA...DECREASING TO 20-30% EXTRM SE
VA/CSTL NE NC. QUITE A DISCERNIBLE TEMP GRADIENT ACROSS THE FA
TODAY...WITH HI TEMPS FM NR 40 FAR NW...TO THE MID 50S EXTRM SE
VA AND NE NC.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
ALTHO PCPN WILL END BY VRY EARLY TUE MORNG...EXPECT SKY TO REMAIN
GENERALLY MSTLY CLDY IF NOT CLDY TNGT ACRS THE REGION...DUE TO
LIGHT WINDS AND NO REAL DRIER AIR FILTERING IN AT THE LO LVLS.
LOWS TNGT RANGING FM THE LWR 30S TO LWR 40S. DRY WX ON TUE WITH
THE SKY BECMG AT LEAST PRTLY SNY...AS WEAK HI PRES BLDS OVR THE
AREA. MAX TEMPS WILL AVERAGE A FEW DEGREES ABV NORMAL...RANGING FM
THE UPR 40S TO THE UPR 50S.

NEXT STRONGER LO PRES SYSTEM WILL BE DEVELOPING INVOF W/CNTRL
GULF STATES LATE TUE INTO TUE NGT...THEN IS FCST TO TRACK TO THE NE
INTO ERN KY BY WED AFTN. A SECONDARY LO ESE OF THE UPR LO WILL
THEN TRACK ACRS CNTRL VA UP INTO ERN MD LATE WED AFTN INTO WED
NGT. A WARM FRNT WILL LIFT INTO/THRU THE FA ON WED AIDED BY
INCREASING SE THEN S WINDS. MAIN AREA OF MID LVL DYNAMICS TO
REACH THE FA WED AFTN...AS RIBBON OF HIGHER SFC DEWPTS/LO LVL
INSTABILITY WOULD BE SURGING NWD. THEREFORE...THOUGH IT BEING LATE
DEC...CONCERN IS FOR POSSIBLE CONVECTION AND A PERIOD OF MDT/HVY
RAIN AHEAD OF/WITH THE COLD FRONT DURG WED AFTN. WILL (STRNG) TSTM
POTENTIAL BE INCREASED BY TRIPLE POINT LO MOVING NNE OVR THE
PIEDMONT? WILL HAVE 80% POPS...AND MAINTAIN CHC T FOR SRN HALF OF
VA/NE NC (WED AFTN). HI TEMPS WED FM THE UPR 40S/LWR 50S NW TO
THE MID TO UPR 60S IN EXTRM SE VA/CSTL NE NC.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
DECENT MODEL AGREEMENT WED NIGHT WITH A QUICK COLD FRONTAL PASSAGE
AS DEEPENING LOW PRESSURE QUICKLY MOVES NORTHEAST OF THE REGION.
KEPT CHC EVE POPS AHEAD OF FROPA. CAA KICKS IN ALLOWING DRY SLOT TO
PUNCH NE AND CUT PCPN OFF AFTR MIDNITE. LOWS IN THE 30S.

THURSDAY APPEARS TO BE ANOTHER DAY LIKE SATURDAY WAS. STRNG PRS
GRDNT ARND DEPARTING LOW RESULTS IN A BREEZY/WINDY DAY WITH PTNTL
FOR GUSTS OVER 30 MPH INLAND AND GALE FORCE WINDS OVER THE WATERS.
PT SUNNY AS COLD AIR ALOFT RESULTS IN SC DVLPMNT DRNG THE DAY. KEPT
IT DRY WITH HIGHS IN THE 40S TO L50S SERN CNTYS.

HIGH PRS BUILDS INTO THE AREA THURS NITE & FRI. THIS KEEPS IT DRY
WITH DMNSHG WINDS. LOWS THURS NITE M20S-L30S. HIGHS FRI IN THE 40S.

MODELS THEN DIVERGE BY NEXT WEEKEND AS YET ANTHR (WEAKER) SYSTM
EJECTS OUT OF SW THEN MOVES ACROSS THE SRN CONUS. ECMWF QUICKER IN
BRINGING PCPN IN FRI NITE WITH THE GFS GIVING THE REGION THE OLD
SPLIT IN PCPN BATCHES SAT. WILL KEEP LOW CHC (LIQUID) POPS IN FOR
SAT. SOME P-TYPE ISSUES ARE PSBL IF PCPN COMES IN A BIT FASTER FRI
NITE. LOWS FRI NITE U20S-M30S. HIGHS SAT IN THE 40S AND 50S. COLDER
BEHIND SYSTM SUNDAY. LOWS SAT NITE M20S-M30S. HIGHS SUN IN THE
40S.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
CONTINUING TO HAVE LIGHT RAIN MOVING NORTHEAST AHEAD OF A PV MAX
IN THE OHIO VALLEY. THIS PRECIPITATION WILL MOVE OFF THE COAST
AROUND 00Z TONIGHT. HOWEVER THE COLD FRONT ACCOMPANYING THE
PRECIPITATION IS QUITE WEAK AND STILL CONTAINS PLENTY OF LOW LEVEL
MOISTURE. THIS WILL CAUSE CEILINGS TO LOWER AFTER THE RAIN ENDS
AND EXPECT IFR STRATUS OVERNIGHT AT ALL THE TAF SITES. THIS IS ON
THE LOW END OF MOST STATISTICAL GUIDANCE BUT THE RAP NAM AND GFS
BUFKIT SOUNDINGS DO SUPPORT THE LOWER CLOUD DECK. PLENTY OF DRYING
ALOFT TONIGHT. THIS WILL HELP IN THE MORNING AS WINDS SHOULD
INCREASE ENOUGH AND WITH THE SUNSHINE THE LOW CLOUDS WILL BREAK UP
DURING THE MORNING WITH VFR FOR THE REMAINDER OF THE DAY.

NEXT WEATHER SYSTEM WILL BE LOW PRESSURE MOVING THROUGH WEDNESDAY
INTO THURSDAY. THIS WILL LIKELY BRING SOME IFR CONDITIONS FOR A
TIME WEDNESDAY AND WEDNESDAY NIGHT AS RAIN MOVES ACROSS THE AREA.
COULD SEE ISOLATED THUNDERSTORMS OVER SOUTHEAST VIRGINIA WEDNESDAY
AFTERNOON OR EVENING. VFR CONDITIONS RETURN DURING THURSDAY WITH
NEXT CHANCE OF LOWER CIGS AND VSBY OVER THE WEEKEND BUT STILL
PLENTY OF UNCERTAINTY ON THIS.


&&

.MARINE...
WEAK COLD FRONT NOW DROPPING THROUGH NORTHERN PORTIONS OF THE MARINE
AREA...SHIFTING WINDS TO THE N. THUS FAR WIND SPEEDS HAVE BEEN 10 KT
OR LESS...AND EVEN W/ SOME INCREASE EXPECTED...SCA CONDITIONS ARE
NOT ANTICIPATED. BOUNDARY STALLS/DISSIPATES OVER SE VA/NE NC LATER
TODAY AS LOW PRESSURE TRACKS NE FROM THE OHIO VALLEY TO PA BY THIS
EVENING...AND OFF THE NJ COAST CHRISTMAS MORNING. WINDS WILL SHIFT
BACK TO THE SE AND THEN THE SW LATER TONIGHT AND ONCE AGAIN TURN
NORTHERLY DURING THE DAY CHRISTMAS. WIND SPEEDS NOT EXPECTED TO
REACH SCA THRESHOLDS DUE TO THE LACK OF COLD AIR MAKING IT SOUTH
INTO THE REGION (ALTHOUGH A FEW HRS WORTH OF WINDS GUSTING CLOSE TO
20 KT WILL BE POSSIBLE W/ THE FRONT EARLY TUE. BAY WAVES AVG 1-2 FT
AND SEAS 2-4 FT THROUGH TUE EVENING.

ON WED...A MUCH MORE POTENT SYSTEM WILL LIFT ENE FROM THE TENNESSEE
VALLEY...AS STRONG HIGH PRESSURE REMAINS IN PLACE NORTH OF THE GREAT
LAKES IN CANADA. THIS PATTERN YIELDS A STRONG PRESSURE GRADIENT AND
TYPICALLY MODELS ARE UNDERDONE OVER THE MARINE AREA W/ NE
WINDS...PARTICULARLY W/ RAPID INTENSIFICATION OF THE SFC LOW AS IT
MOVES TOWARDS THE COAST BY WED NIGHT. EXPECT AT LEAST A STRONG SCA
EVENT ON WED...WITH GALES A GOOD POSSIBILITY ALONG THE COAST
(ESPECIALLY N OF CAPE CHARLES). SEAS LIKELY BUILD TO 8-10 FT OVER
PORTIONS OF THE COASTAL WATERS AND 3-5 FT IN THE BAY. GALES WILL
CONTINUE TO BE POSSIBLE ON THU AS WINDS SHIFT TO THE W AS THE LOW
SLIDES OFFSHORE. COLD AIR ADVECTION IS NOT ALL THAT STRONG THOUGH SO
IT MAY NOT BE REAL LONG-LIVED.

TIDAL FLOODING IS ALSO POSSIBLE BY WED/WED NIGHT...MDL AND CBOFS
GUIDANCE IS SHOWING ANOMALIES UP TO 1.5 FT AT OCEAN CITY (AND 1 FT
OR LESS ELSEWHERE). ALTHOUGH THIS WOULD NOT YIELD EVEN MINOR
FLOODING...IT IS PROBABLY A BIT UNDERDONE AS THE GUIDANCE TENDS TO
BE BEYOND 36 HRS. WILL CONTINUE TO MONITOR.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...TMG
NEAR TERM...JDM/TMG
SHORT TERM...ALB/TMG
LONG TERM...MPR
AVIATION...LKB/JAB
MARINE...LKB







AREA FORECAST DISCUSSION

NWS MARQUETTE MI

 436 PM EST MON DEC 24 2012

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 434 PM EST MON DEC 24 2012

WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL LOW OVER NRN
ONTARIO WITH A TROUGH EXTENDING INTO THE WESTERN GREAT LAKES. A
SHORTWAVE TROUGH WAS LOCATED OVER LOWER MI WHILE UPSTREAM A WEAKER
SHRTWV EXTENDED FROM THE SRN END OF JAMES BAY TO NEAR KINL. ALTHOUGH THE
STRONGEST 700-300 MB QVECTOR CONV REMAINED SOUTHEAST OF UPPER MI
WHILE...SOME WEAK TO MODERATE FORCING LINGERING OVER THE AREA
SUPPORTED AREAS OF LIGHT SNOW WITH VISIBILITIES GENERALLY AT OR
ABOVE 5SM. NW LOW LEVEL WINDS WITH 850 MB TEMPS AROUND -15C ALSO
SUPPORTED SOME LIGHT LES BANDS. A SIGNIFICANT LIMITING FACTOR FOR
LES INTENSITY WAS LOW INVERSION HEIGHTS AROUND 4K FT AND INFLUX OF
DRIER AIR BELOW THE INVERSION.

TONIGHT...INCREASING LOW-LVL CONVERGENCE AIDED BY DEVELOPING LAND
BREEZES SHOULD PROVIDE ADDITIONAL FOCUS FOR LES INTO ERN ALGER/NRN
SCHOOLCRAFT AND PERHAPS OVER THE PORCUPINE MOUNTAINS OVER THE WEST.
THE DRY AIR UPSTREAM AND LOW INVERSION HEIGHTS WILL LIMIT
AMOUNTS...ESPECIALLY OVER THE WEST...TO GENERALLY AN INCH OR LESS.
GREATER POPS WERE INCLUDED OVER THE ERN CWA WHERE THE LONGER FETCH
WILL HELP KEEP INVERSION HEIGHTS IN THE 5K-7K FT RANGE AND CLOUD
SUPPORT SLIGHTLY GREATER SNOWFALL AMOUNTS OF AN INCH OR TWO.

LES WILL CONTINUE INTO CHRISTMAS DAY AS 850 MB TEMPS REMAIN NEAR
-14C BUT SHOULD DIMINISH AS WINDS BACK TO WNW WITH SLOWLY LOWERING
INVERSION HEIGHTS AND MORE ANTICYCLONIC/DIVERGENT LOW LEVEL FLOW.
SNOWFALL INTENSITY/AMOUNTS WILL REMAIN GREATEST OVER THE EAST WHERE
AN ADDITIONAL INCH MAY ACCUMULATE.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 434 PM EST MON DEC 24 2012

NOT A LOT OF EXCITING WEATHER TO GO IN DEPTH ABOUT FOR THE LONG TERM
PERIOD /TUESDAY NIGHT THROUGH NEXT MONDAY/. WE WILL BE DOMINATED BY
NORTHERLY WINDS FOR MUCH OF THE PERIOD WITH SLIGHT TO LOW CHANCE
POPS NEAR LAKE SUPERIOR...AS THE STORM TRACK CONTINUES TO BE WELL TO
OUR S.

TUESDAY NIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW 0
THANKS TO A POCKET OF CLEARING NOTED BY SOME OF THE SMALLER SCALE
MODELS.

DID INCREASE THE FCST MODEL CONSENSUS POPS FOR SATURDAY NIGHT
THROUGH MONDAY...HEDGING THE FCST CLOSER TO THE ECMWF AND SLIGHTLY
HIGHER CONFIDENCE IN COLD AIR ROTATING IN ON MAINLY NW WINDS. THE
OUTLIER WAS THE GFS...PARTICULARLY FROM SUNDAY ON AS IT BROUGHT A
SFC LOW FROM CENTRAL CANADA TO ONTARIO SUNDAY NIGHT. A WEAKENING SFC
TROUGH CONTINUED FOR THE GFS...EXTENDING W FROM THE EXITING LOW OFF
THE COAST OF MAINE. THE ECMWF HAD FAIRLY STEADY 850MB TEMPS OF -15
TO -20C FROM SATURDAY NIGHT THROUGH MONDAY...WITH AT LEAST LIMITED
MOISTURE TO BRING IN A GOOD CHANCE OF SNOW SHOWERS.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1247 PM EST MON DEC 24 2012

WITH A STRONG INVERSION OVER THE AREA...THE STRATUS CLOUDS WILL
PERSIST THROUGH TONIGHT. LIGHT SNOW WITH VSBY DOWN TO AROUND 3SM AT
IWD IS EXPECTED TO MOVE OUT EARLY THIS AFTERNOON. OTHWERWISE...A NW
FLOW WILL BRING SOME OCCASIONAL LIGHT LAKE EFFECT SNOW TO THE TAF
SITES BUT VSBYS SHOULD NOT BE RESTRICTED BY IT. SO...EXPECT MVFR
CIGS AT BOTH KCMX AND KSAW THROUGH THE FCST PERIOD.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 434 PM EST MON DEC 24 2012

A HIGH PRESSURE RIDGE BUILDING IN FROM THE CANADIAN PRAIRIES TODAY
AND TONIGHT WILL LINGER THROUGH MUCH OF THE WEEK...KEEPING WINDS
AT OR BELOW 25 KNOTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...JLB
LONG TERM...KF
AVIATION...JLB
MARINE...JLB







AREA FORECAST DISCUSSION

NWS DETROIT/PONTIAC MI

 337 PM EST MON DEC 24 2012

.SHORT TERM...THIS EVENING AND TONIGHT

UPSTREAM LIGHT SNOW AND VIRGA HAVE BEEN STEADILY PUSHING INTO THE
AREA AHEAD OF THE COMPACT MID-LEVEL SHORTWAVE ROTATING ACROSS THE
LOWER PENINSULA THIS AFTERNOON. FOR SEVERAL HOURS NOW, A PERIOD OF
VIRGA HAS PRECEDED A RATHER BRIEF PERIOD OF LIGHT TO MODERATE
SNOWFALL.

ANALYSIS OF OBSERVATIONS AND SHORT TERM MODEL DATA INDICATE THAT THE
ONGOING SNOWFALL/VIRGA IS STRONGLY TIED TO TWO SEPARATE FEATURES.
THE FIRST, AND PRIMARY TO AFFECT SOUTHEAST MICHIGAN, IS THE BROAD
CORRIDOR OF ASCENT ASSOCIATED WITH DCVA PRECEDING THE WAVE ITSELF.
THE SECOND, MAINLY AFFECTING LOCATIONS SOUTH OF THE BORDER...PERHAPS
AS FAR NORTH AS THE I-94 CORRIDOR...IS A DEEP FRONTOLYTIC
CIRCULATION LEADING THE NOSE OF THE ASSOCIATED 80-KT JET STREAK.
THIS REGION OF FORCED COLD ASCENT HAS ALSO DRAWN UPON A POCKET OF WEAK
MID-LEVEL INSTABILITY TO PRODUCE A STRONGER CONVECTIVE RESPONSE TO
THE SOUTH AND OCCASIONAL ECHOES OF 40DBZ OVER NORTHERN IN.

THE NORTHWARD MIGRATION OF THE ELEVATED FRONTAL ZONE/THETA-E RIDGE
AS WELL AS SUB-850 EASTERLY MOISTURE ADVECTION WILL HELP TO ERODE
THE H85-H7 DRY LAYER APPARENT ON THIS MORNING`S 12Z DTX SOUNDING AND
ALLOW FOR A SUBSEQUENT EXPANSION OF LIGHT SNOW AND DECREASE IN VIRGA
OVER THE NEXT FEW HOURS. RECENT RADAR TRENDS CONFIRM THESE
EXPECTATIONS (AND YESTERDAY`S NMM CORE SOLUTIONS). RUC ANALYSIS
SUGGESTS THAT WHILE A BRIEF PERIOD OF CONVECTIVE PRECIP WILL BE
POSSIBLE ACROSS THE SOUTHERN CWA, THE BULK OF THE EVENT WILL LIKELY
TAKE PLACE ACROSS THE HEART OF THE FORECAST AREA AND WILL BE
CHARACTERIZED BY A FEW HOURS OF LIGHT SNOW WITH EMBEDDED MODERATE
BANDING OWING TO BOTH A VERY WEAKLY STATICALLY STABLE ATMOSPHERE
ABOVE THE LOW-LEVEL FRONT AND MARGINAL MID-LEVEL INSTABILITY. THE
FORECAST HAS THEREFORE BEEN AMENDED TO REFLECT A HIGHER POP SCENARIO
FROM APPROXIMATELY LIVINGSTON TO TO LAPEER COUNTIES WHERE A
WIDESPREAD HALF INCH OR SO IS STILL POSSIBLE. LOCATIONS AFFECTED BY
SAID BANDING WILL SEE A PORTION OF THE SNOW ACCUMULATE MORE QUICKLY
AS VSBYS FALL TO 1-2 MILES PER UPSTREAM OBS...RESULTING IN THE
POTENTIAL FOR A FEW ISOLATED 1" ACCUMS.

&&

.LONG TERM...

CHRISTMAS DAY WILL BE ON THE TRANQUIL SIDE OVERALL AROUND SE
MICHIGAN LEADING INTO AN ACTIVE PERIOD OF WINTER WEATHER AFTER THE
HOLIDAY. HIGHER END ADVISORY CRITERIA SNOWFALL AMOUNTS AND RATES ARE
ANTICIPATED FOR SE MICHIGAN WEDNESDAY THROUGH WEDNESDAY NIGHT WITH
THE TIMING ON THE DAY AFTER CHRISTMAS AND POTENTIAL TRAVEL IMPACTS
BEING THE NOTABLE ASPECT OF THE EVENT.

THE WEDNESDAY LOW PRESSURE SYSTEM WILL BE PRECEDED BY SOME LAKE
EFFECT SNOW SHOWERS MAKING INLAND PROGRESS OFF LAKE HURON DURING
CHRISTMAS DAY. INLAND PROGRESS COULD BE AS FAR SOUTH AS I-69 AND
WEST TO I-75 ON A SCATTERED BASIS WITH GREATER COVERAGE IN THE THUMB
CLOSER TO THE LAKE. INSTABILITY WILL BE MODEST WITH LAKE TO 850
DELTA-T RUNNING AROUND 15C BUT WITH INVERSION HEIGHT BOOSTED BY SOME
SEEDING FROM MID LEVEL MOISTURE TRAILING TODAY`S WAVE. THE BROAD
INVERTED SURFACE TROUGH WILL PROVIDE A FAVORABLE LOW LEVEL WIND
FIELD FOR FOCUSING NORTHERLY FLOW INTO THE THUMB FOR A FEW HOURS
BEFORE FILLING AND DRYING TOWARD EVENING.

THE MAIN CONCERN IN THE FORECAST REMAINS THE EVOLUTION OF A LARGE
LOW PRESSURE SYSTEM SET TO IMPACT MUCH OF THE COUNTRY EAST OF THE
MISSISSIPPI WEDNESDAY INTO THURSDAY. THIS SYSTEM IS EXPECTED TO
NEGATIVELY IMPACT POST HOLIDAY TRAVEL ACROSS THE REGION WITH
MODERATE SNOW ACCUMULATION REMAINING THE PRIMARY EXPECTATION IN SE
MICHIGAN. SUBJECT UPPER LEVEL ENERGY WAS MORE FULLY INLAND FROM THE
WEST COAST FOR THE MORNING UPPER AIR ANALYSIS, SO IT IS A GOOD SIGN
THAT THE 12Z MODEL CYCLE HAS NOT SHIFTED MUCH OFF OF EARLIER
SOLUTIONS AS THE SYSTEM DEVELOPS OVER THE WESTERN GULF COAST DURING
CHRISTMAS DAY AND DEEPENS INTO THE TENNESSEE VALLEY BY WEDNESDAY
MORNING. AGREEMENT BETWEEN THE NAM, GFS, ECMWF, AND LOCAL WRF GLOBAL
IS EXCELLENT BY THEN ON THE POSITION AND INTENSITY OF THE LARGE
SCALE FEATURES ASSOCIATED WITH THE SYSTEM. THE CANADIAN REMAINS
FASTER/FARTHER EAST IN THE SOLUTION SPACE PERHAPS REPRESENTING THE
STRONG INFLUENCE ON TRACK AND STRENGTH BY THE SOUTHWARD POSITION OF
THE UPPER JET AXIS FROM SOUTHERN CALIFORNIA TO THE CENTRAL GULF
COAST. THERE IS ALSO CONSIDERABLE LOW LEVEL BAROCLINICITY, GULF
MOISTURE, AND WARM SECTOR INSTABILITY IN ADVANCE OF THE WAVE FROM
THE TENNESSEE VALLEY TO THE MID ATLANTIC STATES. ALL OF THIS, ALONG
WITH A NEW ROUND OF UPPER LEVEL HEIGHT FALLS OVER THE WEST COAST,
FAVORS PROGRESSION AND THE TRANSFER OF CYCLOGENESIS TO THE EAST
COAST DURING WEDNESDAY.

CONFIDENCE IN THE MODEL SOLUTIONS ON THE BULK FEATURES DOES NOT GET
US OUT OF THE WOODS ON A WINTER EVENT OR SIMPLIFY THE FORECAST FOR
OUR AREA DURING WEDNESDAY INTO WEDNESDAY NIGHT AS A CONSIDERABLE
AMOUNT OF MOISTURE REMAINS ADVERTISED FOR THE REGION. WITH AN EASY
CALL ON ALL SNOW AS THE PRECIPITATION TYPE, THE QUESTION OF AMOUNT
REMAINS TIED TO THE CHARACTER AND DURATION OF MAX FORCING AND
MICROPHYSICAL ASPECTS OF THE SNOW OVER SE MICHIGAN DURING THE PEAK
OF THE EVENT WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING. THE
TRANSFER OF CYCLOGENESIS TO THE MID ATLANTIC COAST WILL SIPHON AT
LEAST SOME ENERGY AND MOISTURE OUT OF THE GREAT LAKES BUT A WELL
ORGANIZED TROWAL IS SHOWN TO BE IN PLACE OVER OUR AREA WITH A STRONG
HYBRID ATLANTIC/GULF MOISTURE CONVEYOR FEEDING INTO THE NORTH FLANK
OF THE SYSTEM. MODEL FIELDS OF SPECIFIC HUMIDITY INDICATE MORE THAN
ADEQUATE AMOUNTS OF 2-3 G/KG IN THE 850 TO 700 MB LAYER ASSOCIATED
WITH THE TROWAL AXIS. THIS LEAVES DURATION AS THE LIMITING FACTOR AS
FIELDS OF THETA-E INDICATE THE TROWAL SHRINKING EASTWARD QUICKLY BY
MIDNIGHT WEDNESDAY NIGHT. WILDCARDS TO CONSIDER THAT COULD SKEW
AMOUNTS HIGHER INCLUDE THE ACTUAL TIMING OF EAST COAST TRANSFER,
MESOSCALE BANDS WITHIN THE TROWAL, AND LAKE ENHANCEMENT. THE
POTENTIAL FOR LAKE ENHANCEMENT WILL BE THE MOST LIKELY EXTRA
CONTRIBUTOR BUT THAT WILL TEND TO STRETCH THE EVENT WELL INTO
THURSDAY AS SYNOPTIC FORCING WANES. THIS WILL CONTINUE TO BE
EVALUATED BUT THE PREPONDERANCE OF EVIDENCE FOR THIS FORECAST
PACKAGE, ALONG WITH MODEL SOUNDING DERIVED SNOW RATIO AVERAGING
11:1, SUGGESTS STORM TOTALS WILL REMAIN MOSTLY BELOW 6 INCHES DURING
THE 12 TO 18 HOUR EVENT ENDING BY SUNRISE THURSDAY.

AFTER A BREAK DURING THURSDAY AND MOST OF FRIDAY, THE ACTIVE LARGE
SCALE PATTERN WILL CONTINUE WITH THE NEXT PACIFIC SYSTEM REACHING
THE GREAT LAKES TO START THE WEEKEND. EARLY INDICATIONS ARE THIS
SYSTEM WILL BE LESS ORGANIZED AS IT MOVES THROUGH THE GREAT LAKES
BEFORE GAINING STRENGTH ALONG THE EAST COAST TOWARD SUNDAY.

&&

.MARINE...

LIGHT NORTHERLY WINDS TONIGHT OF 15 KNOTS OR LESS WILL TURN EASTERLY
AND BEGIN TO INCREASE ON TUESDAY NIGHT AS A STRONG LOW PRESSURE
SYSTEM LIFTS TOWARD THE REGION FROM THE SOUTH. THE PROLONGED PERIOD
OF ONSHORE FLOW WILL FAVOR ELEVATED WAVE CONDITIONS FOR ALL
NEARSHORE ZONES BETWEEN WEDNESDAY AND THURSDAY MORNING IN ADDITION
TO POTENTIAL FUNNELING INTO SAGINAW BAY. SMALL CRAFT ADVISORIES
APPEAR LIKELY AT THIS TIME. BY WEDNESDAY AFTERNOON INTO WEDNESDAY
NIGHT...GUSTS TO NEAR GALES WILL BE POSSIBLE ACROSS AREA WATERS.

&&

.AVIATION...ISSUED 1227 PM EST MON DEC 24 2012

//DISCUSSION...

STRATUS WILL CONTINUE TO AFFECT ALL THE TAF SITES. CURRENT SATELLITE
IMAGERY IS SHOWING A BRIEF BREAK...HOWEVER THIS BREAK IS SHORT LIVED
AS MORE STATUS MOVES IN FROM THE SOUTH FROM A WEAK LOW PRESSURE
SYSTEM MOVING THROUGH THE OHIO VALLEY.  THIS SYSTEM IS EXPECTED TO
BRING LIGHT SNOW TO FROM PTK SOUTHWARD...WITH THE NORTHERN TAF SITES
MOST LIKELY SEEING JUST LOW CLOUDS.  THIS IS IN PART DUE TO THE
DRIER MID LEVELS PER THE 12Z SOUNDING.  LOOKING AT VISIBILITIES AND
CEILINGS STAYING IN THE MVFR RANGE.  INTERMITTENT REDUCTION IN
VISIBILITIES BETWEEN 3-5SM WILL BE POSSIBLE WITH THE SNOW.

FOR DTW...ONLY MINOR ACCUMULATION POTENTIAL 21-03Z WITH THIS SNOW
GIVEN THE EXPECTED LOWER DURATION/INTENSITY.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5000 FT THROUGH TUESDAY MORNING.

* HIGH CONFIDENCE IN SNOW AS PRECIPITATION TYPE.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...JVC
LONG TERM....BT
MARINE.......JVC
AVIATION.....SS/JVC


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).









AREA FORECAST DISCUSSION

NWS NASHVILLE TN

 1208 PM CST MON DEC 24 2012

.UPDATE...FOR 18Z AVIATION FORECAST

&&

.AVIATION...
SURFACE LOW HAS MOVED NORTHEAST INTO SOUTHWEST OHIO WITH COLD
FRONT DOWN ALONG THE PLATEAU INTO NORTH ALABAMA AT 18Z. MID LEVEL
TROUGH HAS SHIFTED EAST WITH AXIS ALONG THE PLATEAU. NORMALLY WE
WOULD EXPECT CLEARING TO FOLLOW BUT NOT TODAY AS WINDS NEAR THE
SURFACE AND LOWER LEVELS OF THE TROPOSPHERE ARE VERY LIGHT ALONG
WITH A SURFACE INVESION KEEPING LOW CLOUDS LOCKED IN ACROSS
MIDDLE TENNESSEE AND ADJACENT AREAS. HOWEVER...WE ARE BEGINNING TO SEE
MORE BREAKS IN THE OVERCAST IN WESTERN MIDDLE TENNESSEE. LOW
CEILINGS WILL LIKELY REMAIN ACROSS THE AREA FOR MOST OF THE
DAYLIGHT HOURS WITH SOME IMPROVEMENT POSSIBLE AT LEAST TEMPORARILY
DURING THE EVENING. GENERALLY FOGGY CONDITIONS WILL REMAIN ALONG
THE PLATEAU PRETTY MUCH FOR THE NEXT 24 HOURS WITH IFR AND LIFR
CONDITIONS AT CROSSVILLE ALTHOUGH THERE COULD BE BRIEF TEMPORARILY
IMPROVEMENTS.


BOYD
&&

.PREV DISCUSSION... /ISSUED 929 AM CST MON DEC 24 2012/

UPDATE...FOR AVIATION FORECAST AT 15Z

EVEN THOUGH SURFACE LOW AND MID LEVEL SHORT WAVE ARE MOVING
THROUGH MIDDLE TENNESSEE AT 15Z SOME DRYING WILL TAKE PLACE IN THE
MID LEVELS WHILE MOISTURE IS EXPECTED TO REMAIN IN THE LOWER LEVELS.

FORECAST SOUNDINGS OFF THE LATEST RUC RUN KEEP LOW LEVEL MOISTURE
ACROSS THE MID STATE WHILE DRYING OUT MID LEVELS THROUGH A GOOD
PART OF THE DAY KEEPING MVFR AND OCCASIONAL IFR CONDTIONS AT BOTH
CLARKSVILLE AND NASHVILLE AND BASICALLY IFR CONDITIONS AT
CROSSVILLE LIKELY THROUGH THE DAYLIGHT HOURS. SATELLITE DOES SHOW
OCCASIONAL BREAKS IN THE OVERCAST (BINOVC) BUT THEY FILL IN RATHER
QUICKLY. LOW CLOUDS EXTEND ALL THE WAY BACK TO THE MISSISSIPPI
RIVER AT THIS TIME.

BOYD

AVIATION...

PREV DISCUSSION... /ISSUED 525 AM CST MON DEC 24 2012/

UPDATE...ADDED AVIATION SECTION FOR 12Z TAF`S.

AVIATION...BNA/CKV/CSV...COLD FRONT MOVING ACROSS MIDDLE
TENNESSEE THIS MORNING, BRINGING LIGHT TO MODERATE RAINFALL,
FOG, AND LOW CIGS. EXPECT IFR CONDITIONS FOR MUCH OF THE MORNING,
WITH CIGS IMPROVING DURING THE AFTERNOON AND EVENING AT BNA AND
CKV, AND REMAINING VFR OVERNIGHT. CSV WILL LIKELY EXPERIENCE LOW
CIGS THROUGHOUT THE DAY, WITH POSSIBLE LIFR CONDITIONS DEVELOPING
OVERNIGHT AS VV`S DROP TO NEAR ZERO AND VSBY AS LOW AS 1/2 MILE.

PREV DISCUSSION... /ISSUED 401 AM CST MON DEC 24 2012/

DISCUSSION...LOW PRESSURE SYSTEM CENTERED OVER THE MID MS VALLEY WILL
CONTINUE NEWD TODAY WITH RAIN CHANCES DIMINISHING DURING THE DAY.
COOLER TONIGHT WITH LOWS IN THE 30S BUT NO PRECIP EXPECTED.

NEXT SYSTEM DEVELOPS OVER TX ON TUE IN RESPONSE TO A VIGOROUS
UPPER WAVE THAT DIVES SEWD THROUGH THE ROCKIES EARLY TUE. THE SFC
LOW THEN MOVES NEWD THROUGH THE LOWER MS VALLEY TO A POSITION NEAR
MACON COUNTY EARLY WED MORNING. THIS IS A STRONG SFC LOW AND IS
PUSHING CONSIDERABLE MOISTURE AHEAD OF IT. THUS HPC IS SPITTING
OUT 1.25 TO 2.00 INCHES OF RAINFALL OVER THE AREA FOR THE DAY 1-3
TIME PERIOD. HAVE ALSO INCLUDED A MENTION OF TSTMS FOR SRN/SERN
COUNTIES ON TUE PM.

SO...HOW MUCH OF THAT RAINFALL WILL BE SNOW...APPARENTLY VERY
LITTLE. THE TRACK OF THE SFC LOW SEEMS TO BE A BIT FURTHER TO THE
WEST COMPARED WITH LAST NIGHTS RUN. THUS ANY SNOW AMOUNTS HAVE
BEEN REDUCED. IT APPEARS NOW THAT THE FAR NERN COUNTIES COULD GET
25 TO .50 INCHES OF SNOW LATE TUE NIGHT AND WED AM WITH THE NRN
CUMBERLAND PLATEAU GETTING LESS THAN A HALF INCH LATE WED AND WED
EVENING. ELSEWHERE A DUSTING IS POSSIBLE WED PM/EVE.

OF COURSE IT WILL BE TURNING COLDER FOR WED NGT AND THU WITH HIGHS
ON THU IN THE UPPER 30S TO NEAR 40 AND LOWS THU NGT IN THE MID 20S.
NO SIGNIFICANT WEATHER EXPECTED FOR THU THROUGH FRI AM.

SELY FLOW RETURNS THU NGT AS THE NEXT SYSTEM DEVELOPS OVER THE
LOWER PLAINS. MOISTURE PUSHES BACK INTO THE AREA ON FRI WITH A
CHANCE OF RAIN FOR FRI PM AND BEYOND. ONE CAUTION HERE...WITH THE
COLD AIR MASS STILL IN PLACE...IF THE PRECIP COMES IN EARLIER THAN
EXPECTED IT WOULD LIKELY HAVE A FREEZING RAIN COMPONENT.

RAIN CHANCES CONTINUE THROUGH FRI AND WILL LIKELY BE A MIXED BAG
OF RAIN AND SNOW. COLD AIR MOVES IN ON SAT WITH A CHANCE OF SNOW
IN THE MIDDLE AND EAST SECTION ON SAT NGT. HIGH PRESSURE OVER THE
AREA THROUGH SUN.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

01






AREA FORECAST DISCUSSION

NWS SPOKANE WA

 1154 AM PST Mon Dec 24 2012

.SYNOPSIS...
Snow will end over the region today.  Another storm system
will spread light snow into the Cascades Christmas morning,
reaching the Panhandle Christmas night.  Drier but colder
conditions will arrive for the end of the work week and into the
weekend.

&&

.DISCUSSION...
Update to let the advisories for the Palouse and Blue Mtns expire.
Moderate to heavy snow still falling south of St Maries so will
continue the warning for the Central Panhandle Mtns. Web cams on
the Camas Prairie indicate that snow has stopped there for the
time being but HRRR runs still show a threat of more snow there so
will continue that Advisory until this afternoon`s forecast package.

Still struggling with low temperature forecast for tonight.
Guidance is all over the place. Clear skies and fresh snow certainly
bode well for a very cold night. But surface dew points are rather
high (lower 30s in many locations) which will cause fog to form
quickly, keeping us warmer. More on this topic with the afternoon
discussion.  RJ

&&

.AVIATION...
18Z TAFS: Surface low over the central Panhandle continues to
produce snow over the southern Panhandle and southeast Washington.
This will gradually taper off this afternoon for improving
conditions at KPUW and KLWS. KGEG/KSFF/KCOE should continue to
improve as well with VFR weather this afternoon. Tough call is
tonight for fog and low clouds. Most TAF sites should see a few
hours of IFR conditions overnight, but conditions will likely be
quite variable between IFR and VFR hour to hour, so confidence is
low on the exact hours. By Tuesday morning the easterly winds
should cause improving conditions at KPUW/KCOE/KSFF/KGEG while
causing IFR weather at KEAT.  RJ

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  17  30  25  29  22 /   0  10  30  60  50  30
Coeur d`Alene  32  18  31  26  30  24 /  20  10  20  60  60  40
Pullman        33  24  32  29  33  27 /  50  20  30  70  60  40
Lewiston       38  28  39  33  39  29 /  30  20  30  60  50  30
Colville       37  18  31  25  30  24 /   0  10  20  80  50  30
Sandpoint      32  15  29  26  28  25 /   0  10  10  60  60  30
Kellogg        33  20  28  25  31  25 /  60  40  10  80  70  40
Moses Lake     38  23  33  27  32  25 /   0  10  80  70  40  20
Wenatchee      36  21  29  24  29  24 /   0  10  90  80  40  20
Omak           34  18  28  21  28  21 /   0  10  90  80  40  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Warning until 4 PM PST this afternoon for Central
     Panhandle Mountains.

     Winter Weather Advisory until 4 PM PST this afternoon for Lewis
     and Southern Nez Perce Counties.

WA...None.

&&

$$








AREA FORECAST DISCUSSION

NWS GREEN BAY WI

 304 PM CST MON DEC 24 2012

.SHORT TERM...TONIGHT AND TUESDAY.

LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A SHORTWAVE
TROUGH EXTENDING FROM NE WISCONSIN TO SOUTHERN LOWER MICHIGAN EARLY
THIS AFTERNOON.  COMMA HEAD PRECIP WITH A LITTLE HELP FROM A LIGHT
LAKE EFFECT COMPONENT PRODUCED AREAS OF LIGHT SNOW THAT LINGERED
ACROSS NORTHEAST AND EAST-CENTRAL WISCONSIN THROUGH MID-AFTERNOON
BUT IS CURRENTLY EXITING TO THE EAST.  WILL SHOW MOST OF THE PRECIP
ENDING BY 00Z THIS EVENING.  IMPROVING CONDITIONS ARE OCCURRING OVER
CENTRAL AND NORTH-CENTRAL WISCONSIN WHERE BREAKS IN THE OVERCAST ARE
GROWING LARGER.  HIGH PRESSURE IS BUILDING SOUTHWARD ACROSS THE
NORTHERN PLAINS WHERE SKIES ARE MOSTLY CLEAR AND COLD.  THE MAIN
FORECAST CONCERNS INCLUDE THE TIMING OF THE END OF THE PRECIP AND
CLEARING TRENDS TONIGHT.

TONIGHT...THE SHORTWAVE TROUGH WILL BE WELL EAST OF THE REGION OVER
LOWER MICHIGAN AT THE START OF THE PERIOD.  RESIDUAL MOISTURE WILL
TAKE AWHILE TO PUSH OUT OF THE REGION...SO WILL START THE EVENING
WITH MOSTLY CLOUDY CONDITIONS WITH A CHANCE OF FLURRIES OVER NE
WISCONSIN.  BUT STRONG DRY AIR ADVECTION OVER NORTHWEST WISCONSIN
WILL SLOWLY MOVE SOUTHEAST THROUGH THE NIGHT AND GRADUALLY CLEAR OUT
THE SKIES ACROSS THE MAJORITY OF THE REGION.  THE LONE EXCEPTION
WILL BE OVER N-C WISCONSIN WHERE LIGHT NW FLOW WILL CONTINUE TO
GENERATE LAKE EFFECT CLOUDS AND LIGHT SNOW SHOWERS.  TEMPS WILL FALL
TO NEAR ZERO OVER THE COLD SPOTS OF LINCOLN COUNTY WHERE SKIES WILL
CLEAR FIRST TO THE MIDDLE TEENS NEAR LAKE MICHIGAN WHERE CLOUDS WILL
CLEAR LAST.

TUESDAY...CANADIAN HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS THE
NORTHERN PLAINS AND NOSE ITS WAY ACROSS THE WESTERN GREAT LAKES.
LIGHT NORTHWEST FLOW WILL CONTINUE OFF LAKE SUPERIOR INTO N-C
WISCONSIN THROUGH THE MORNING...WHICH WILL KEEP SCT FLURRIES...AND
PARTLY TO MOSTLY CLOUDY CONDITIONS THERE.  ELSEWHERE...MOSTLY SUNNY
CONDITIONS SHOULD PREVAIL.  HIGHS RANGING FROM THE MID TEENS WEST TO
THE MID 20S EAST.

.LONG TERM...TUESDAY NIGHT THRU NEXT SUNDAY.

OVERALL...NO SIGNIFICANT CHANGES TO THE LONG TERM FORECAST. MAIN
FOCUS WAS TO TRY ADD A BIT MORE DETAIL REGARDING LES POTENTIAL
FOR LAKE MICHIGAN COUNTIES FOR WEDNESDAY.

MODELS CONTINUE TO BE IN FAIRLY GOOD AGREEMENT ON OVERALL TRACK OF
SOUTHERN STORM SYSTEM FORECAST TO TRACK TO THE OHIO VALLEY ON
WEDNESDAY. AS PREVIOUSLY FORECAST...THE NORTHERN FRINGE OF STRATIFORM
PRECIPITATION SHIELD WILL JUST CLIP EXTREME SOUTHEAST WISCONSIN
AND THE SOUTHERN PORTION OF LAKE MICHIGAN LATE WEDNESDAY. OTHER
THAN MIDDLE TO HIGH-LEVEL CLOUDS...THE MAIN IMPACT OF THIS SYSTEM
WILL BE TO CREATE A DEEP NORTHEASTERLY WIND FLOW EXTENDING FROM
THE SURFACE UP TO NEAR 700 MB. MAXIMUM OVERWATER BOUNDARY LAYER
FETCH ALSO IN PLACE BY 12Z WEDNESDAY. EXAMINATION OF MODIFIED
FORECAST GFS/NAM SOUNDINGS OVER LAKESHORE COUNTIES INDICATE A
FAIRLY DEEP MOIST AND UNSTABLE LAYER...WITH INVERSION HEIGHTS
APPROACHING 7000 FT AGL OVER WESTERN LAKE MICHIGAN. NAM/GFS ALSO
SUGGEST THAT MOIST LAYER MAY GROW DEEP ENOUGH TO PENETRATE INTO
FAVORABLE DENDRITIC GROWTH ZONE. WATER SURFACE TO 850 DELTA T
VALUES ON THE ORDER OF -16C TO -18C BY 12Z WEDNESDAY OVER THE
NORTHERN HALF OF LAKE MICHIGAN. GFS HAS BEEN FAIRLY CONSISTENT
LAST FEW RUNS...SPITTING OUT AREA OF QPF OVER NORTHERN LAKE
MICHIGAN AFTER 06Z WEDNESDAY AND BRINGING IT ONSHORE BY 12Z
WEDNESDAY. GIVEN OVERALL SYNOPTIC SETUP...NO REASON TO DISCOUNT
SIGNAL FROM GFS. BOTTOM LINE IS FAIRLY DECENT SET-UP FOR LAKE
EFFECT OVER MANITOWOC AND KEWAUNEE COUNTIES STARTING AROUND
DAYBREAK WEDNESDAY AND PERHAPS CONTINUING FOR MUCH OF THE DAY.
GIVEN BOUNDARY LAYER WINDS SPEEDS...WOULD EXPECT MULTIPLE AND SOMEWHAT
LES ORGANIZED LES BANDS RATHER THAN A SINGLE BAND. GIVEN THE
MESOSCALE NATURE OF LES PRECIPITATION WILL LET LATER SHIFTS TRY TO
REFINE THE DETAILS. FELT CONFIDENT ENOUGH AT THIS POINT TO AT
LEAST ADJUST POPS UPWARD INTO THE CHANCE CATEGORY ON WEDNESDAY.
FINALLY...GIVEN DEEP AND PERSISTENT NORHEASTERLY FLOW...ANY LES
BANDS THAT DEVELOP MAY BE ABLE TO PENETRATE AS FAR WEST AS THE FOX
RIVER VALLEY BEFORE WEAKNING. AS OHIO VALLEY STORM SYSTEM
CONTINUES TO MOVE NORTHEAST TO THE EASTERN SEABOARD...BOUNDARY
LAYER WINDS WILL BACK TO OFFSHORE WEDNESDAY NIGHT PUSHING ANY LES
BAND SOUTHWARD. FAIRLY TRANQUIL DAY ON THURSDAY AS WEAK HIGH
PRESSURE RIDGE MOVES ACROSS THE FORTECAST AREA.

THEN BY FRIDAY...SOUTHERN AND NORTHERN STREAM ENERGY BEGIN TO
APPROACH THE CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY.
UNCERTAINTY REMAINS AS TO HOW THESE FEATURES WILL INTERACT...WITH
CONCENSUS OF GUIDANCE SUGGESTING PERHAPS SOME PHASING OVER THE
OHIO VALLEY FRIDAY NIGHT. REGARDLESS...COMBINATION OF THESE
FEATURES SHOULD BE ABLE TO CREATE WAA ADVECTION REGIME AND DRAW
ADEQUATE MOISTURE NORTHWARD TOWARD THE FORECAST AREA TO GENERATE
BROAD AND GENERALLY LIGHT AREA OF QPF LIKELY TO SPREAD INTO THE
FORECAST AREA LATE ON FRIDAY INTO SATURDAY. LEANING MORE TOWARD
SOMEWHAT LESS ORGANIZED INVERTED TROUGH LOOK OF THE ECMWF AND
OPERATIONAL GFS FOR FRIDAY SYSTEM. INVERTED TROUGH AND CYCLONIC
FLOW MAY HANG BACK ACROSS THE WESTERN GREAT LAKES INTO
SATURDAY...THUS CONTINUE CHANCE POPS UNTIL THEN AS PER PREVIOUS
FORECAST.

DAYTIME TEMPERATURES SHOULD GRADUALLY MODERATE BY THE END OF THE
WEEK TO NEAR OF PERHAPS SLIGHTLY ABOVE NORMAL.
&&

.AVIATION...AN UPPER LEVEL DISTURBANCE WILL PASS ACROSS THE STATE
THIS AFTERNOON AND EXIT BY EARLY THIS EVENING.  SNOWFALL HAS BEEN
THE MOST VIGOROUS OVER NORTHEAST WISCONSIN WHERE VSBYS HAVE
OCCASIONALLY FALLEN BELOW A MILE.  THINK THIS WILL CONTINUE THROUGH
MID-AFTERNOON BEFORE DIMINISHING.  BUT WHATEVER SNOW FALLS SHOULD BE
LIGHT AND FLUFFY AND SHOULD BLOW OFF AIRCRAFT AND RUNWAYS EASILY.
CIGS ARE VARIABLE UPSTREAM OVER WESTERN WISCONSIN...BUT ONCE THE
SNOW EXITS...IMPROVEMENT IN CIGS SHOULD OCCUR TO MAINLY VFR EXCEPT
OVER N-C WISCONSIN WHERE FLOW WILL REMAIN OFF LAKE SUPERIOR.  LIGHT
SNOW SHOWERS AND FLURRIES WILL CONTINUE THERE FOR MUCH OF THE NIGHT
WHILE THE REST OF THE AREA WILL SEE CLEARING FROM NW TO SE.  MAINLY
VFR CONDITIONS ON TUESDAY WITH GOOD FLYING CONDITIONS.

MPC
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$
MPC/ESB







AREA FORECAST DISCUSSION

NWS MILWAUKEE/SULLIVAN WI

 1117 AM CST MON DEC 24 2012

.AVIATION/18Z TADS/...WIDESPREAD MFR CEILINGS WILL CONTINUE INTO
THE OVERNIGHT HOURS. ONE SHORTWAVE LIFTING OUT AND A SECONDARY
WAVE SWINGING THROUGH THIS AFTERNOON/EARLY EVENING MAINTAINING AT
LEAST A CHANCE OF LIGHT SNOW. APPEARS FZDZ POTENTIAL HAS WANED
WITH MODEL SOUNDINGS NOW SHOWING SATURATION TO THE -10C LEVEL.
HOWEVER HRRR MODEL WIPES OUT THE PRECIP WIPES THIS OUT AND
REDEVELOPS SECONDARY MAX IN SW WI. SOME FLURRIES COMING IN OFF THE
LAKE. TRAJECTORIES REMAIN FAVORABLE INTO TUESDAY MORNING THOUGH
DELTA T QUITE BORDERLINE. LOW LEVEL RH PROGS SHOW SOME CLEARING
TUESDAY MORNING.

PC

&&

.PREV DISCUSSION... /ISSUED 952 AM CST MON DEC 24 2012/

UPDATE...FREEZING DRIZZLE WEST AND SW OF MADISON IS VERY ISOLATED
AND WILL CONTINUE TO KEEP IT OUT OF THE FORECAST FOR THE AFTERNOON
WHEN TOP OF STRATUS LAYER EXTENDS UPWARD TO THE -10C LEVEL
RESULTING IN SNOW FLAKES VERSUS DRIZZLE. FOR THIS AFTERNOON...THE
NAM12 AND HRRR MODELS DEVELOP A BAND OF LIGHT SNOW NEAR AND WITHIN
THE SFC-925 MB TROUGH OVER SW WI INCLUDING
IOWA...LAFAYETTE...GREEN COUNTIES AND PORTIONS OF THE ADJACENT
COUNTIES. MAYBE A HALF AN INCH OF SNOW ACCUMULATION IN THESE
AREAS. OTHERWISE SMALL CHANCES OF SNOW OVER THE REMAINDER OF THE
AREA INCLUDING NEAR LAKE MI VIA VERY LIGHT LES.

GEHRING

PREV DISCUSSION... /ISSUED 405 AM CST MON DEC 24 2012/

TODAY...FORECAST CONFIDENCE IS MEDIUM.

MODELS HAVE BACKED OFF FREEZING DRIZZLE POTENTIAL AS COLUMN
MOISTENS FROM BELOW INTO THE -10C RANGE TO PROVIDE ENOUGH ICE
CRYSTALS FOR LIGHT SNOW. DRY MID LAYERS WILL LIMIT AMOUNTS...AS
BEST DEEP LAYER OMEGA WITH SHORT WAVE MOVES THROUGH THE REGION
PRIOR TO 18Z...BEFORE THE DRY LAYER SATURATES. COULD SEE SOME
SEEDER-FEEDER...BUT BEST CHANCE FOR ANY MEASURABLE QPF IS IN THE
WESTERN CWA IN REGION OF LOW-LEVEL CONVERGENCE ALONG AXIS OF
INVERTED SURFACE TROUGH.

LAKE-EFFECT SNOW SHOWER POTENTIAL ALSO HAS LESSENED AS DRY
DENDRITE GROWTH ZONE AND REDUCED FETCH LENGTH REDUCES PROBABILITY.
LOW-LEVEL LAPSE RATES ARE DECENT BUT DELTA T/S ARE CONDITIONAL SO
WILL LEAVE CHANCE PROBABILITY GOING. CLOUDS HAVE HELD OVERNIGHT
TEMPS UP AND EASTERLY FLOW SUPPORT BLENDED HIGH TEMPERATURES IN
THE MID 20S NW TO LOW TO MID 30S SOUTHEAST.

TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

LAKE-EFFECT SNOW POTENTIAL FADES DUE TO WINDS BACKING TO THE
NORTH...KEEPING ANY LAKE BANDS OFFSHORE. WILL KEEP A SLIGHT CHANCE
RIGHT ALONG THE SHORE IN THE EVENING. COLD AIR ADVECTION DROPS
OVERNIGHT LOWS TO AROUND 10 ABOVE NORTHWEST...TOT HE LOW MID 20S
RIGHT ALONG THE LAKE MICHIGAN SHORE.

CHRISTMAS DAY THROUGH WEDNESDAY NIGHT...FORECAST CONFIDENCE IS
MEDIUM.

WEST SOUTHWEST FLOW AT 500MB ON SHORT TERM MODELS CHRISTMAS DAY
GIVES WAY TO A SHORTWAVE TROUGH PASSING THROUGH LATER ON
WEDNESDAY. THIS IS IN RESPONSE TO A CLOSED UPPER LOW MOVING
NORTHEASTWARD...BUT WELL SOUTHEAST OF THE AREA. RIDGING THEN
MOVES INTO THE REGION WEDNESDAY NIGHT.

AT THE SURFACE...CANADIAN HIGH PRESSURE LINGERS ACROSS THE
NORTHERN PLAINS INTO MINNESOTA CHRISTMAS DAY AND TUESDAY
NIGHT...BEFORE A HIGH PRESSURE RIDGE AXIS LINGERS IN MINNESOTA AND
IOWA WEDNESDAY AND WEDNESDAY NIGHT. STRONG LOW PRESSURE MOVES
NORTHEAST...BUT WELL SOUTHEAST OF THE AREA WEDNESDAY. NAM/GFS HAVE
OUTER EDGE OF PRECIPITATION SHIELD JUST MISSING FAR SOUTHEAST
WISCONSIN AT 00Z THURSDAY.

MAIN ISSUE CONTINUES TO BE LAKE EFFECT SNOW IN FAR SOUTHEAST
WISCONSIN FOR CHRISTMAS DAY THROUGH WEDNESDAY NIGHT.
MILWAUKEE/KENOSHA FORECAST SOUNDINGS FROM NAM/GFS CONTINUE TO SHOW
NORTHEAST LOW LEVEL FLOW...WITH MOISTURE AND PERSISTENT LOW LEVEL
CONVERGENCE PER GFS SURFACE TO 850MB FRONTOGENESIS RESPONSE.
FAVORABLE DELTA T VALUES OF 13 TO 16 DEGREES CELSIUS ARE
EXPECTED.

CHANCES FOR THESE LAKE EFFECT SNOW SHOWERS CHRISTMAS DAY/TUESDAY
NIGHT AND WEDNESDAY NIGHT HAVE LOWERED...AS THE LOW LEVEL MOISTURE
IS QUESTIONABLE WITH THE -10 DEGREE CELSIUS LEVEL NOT BEING
TAPPED. THIS WOULD RESULT IN CLOUDS WITH A FEW LIGHT SNOW
SHOWERS...WHICH WOULD NOT DROP ACCUMULATING SNOW PER LAKE EFFECT
SNOW FLOW CHART.

BEST SHOT IS WEDNESDAY...WITH THE BEST LOW LEVEL MOISTURE TAPPING
THE -10 DEGREE CELSIUS ICE CRYSTAL LAYER...AND MORE MID LEVEL
MOISTURE TO USE WITH PASSING SYSTEM TO THE SOUTHEAST. THIS SHOULD
RESULT IN ON AND OFF LIGHT LAKE EFFECT SNOW SHOWERS...ESPECIALLY
AROUND AND SOUTH OF MILWAUKEE. THESE LAKE EFFECT BANDS CAN BE
TRICKY TO FORECAST THIS FAR OUT...SO SOME MODIFICATION OF THE
FORECAST MAY OCCUR.

LAKE EFFECT SNOW FLOW CHART/SNOW TO LIQUID RATIOS SUGGESTS LIGHT
ACCUMULATIONS OF UP TO AN INCH WEDNESDAY SOUTH OF MILWAUKEE...WITH
LOWER AMOUNTS ELSEWHERE NEAR THE LAKE. THESE AMOUNTS COULD BE
HIGHER IF BAND PERSISTS ACROSS A LOCALIZED AREA...SO STAY TUNED TO
THE FORECAST.

THE REST OF THE AREA SHOULD SEE QUIET WEATHER...UNDER MOSTLY
CLOUDY SKIES. TEMPERATURES WILL CONTINUE TO BE AROUND OR JUST
BELOW SEASONAL NORMALS DURING THIS PERIOD.

THURSDAY THROUGH SUNDAY...FORECAST CONFIDENCE IS MEDIUM.

ECMWF/GFS BOTH SHOW A WEAK HIGH MOVING THROUGH THE REGION
THURSDAY...BRINGING QUIET WEATHER. THEY THEN GENERALLY SHOW A
SHORTWAVE TROUGH MOVING THROUGH THE REGION FRIDAY AND FRIDAY
NIGHT...WITH ANOTHER FOR SATURDAY INTO EARLY SATURDAY NIGHT.

A WEAK SURFACE LOW DEVELOPS IN THE CENTRAL PLAINS THURSDAY...AND
MOVES NORTHEAST ACROSS NORTHERN ILLINOIS FRIDAY NIGHT. THE ECMWF
IS MORE AGGRESSIVE WITH QPF THURSDAY NIGHT...WITH THE GFS/ECMWF
THEN IN GENERAL AGREEMENT WITH QPF FRIDAY INTO SATURDAY NIGHT.

USED CONSENSUS APPROACH WITH POPS AND TEMPERATURES IN THIS
PERIOD...WITH CHANCES FOR LIGHT SNOW AND COOL TEMPERATURES. HIGH
PRESSURE SLIDING INTO THE NORTHERN PLAINS SHOULD THEN BRING DRY
AIR INTO THE REGION SUNDAY.

AVIATION/12Z TAFS/...

WILL KEEP MVFR/IFR CONDITIONS GOING RIGHT THROUGH THE FORECAST
PERIOD AS STUBBORN LOW-LEVEL MOISTURE HANGS OVER REGION. FREEZING
DRIZZLE POTENTIAL TODAY HAS BEEN REDUCED WITH FORECAST SOUNDINGS
SHOWING MOISTENING UP FROM BELOW INTO THE -10C LEVEL...WHICH WOULD
PRODUCE SMALL ICE CRYSTALS VERSUS SUPER-COOLED DROPLETS. STILL A
CHANCE THIS MORNING WITH DEEP SYNOPTIC LIFT CROSSING THE REGION THIS
MORNING BUT NOT HIGH ENOUGH TO GO CATEGORICAL SO WILL LEAVE AS A
TEMPO ALONG WITH LIGHT SNOW.

DRY MID-LAYERS WILL LIMIT ANY SNOW AMOUNTS...WITH THE BEST CHANCE OF
MEASURABLE MAINLY IN THE SOUTHWEST FORECAST AREA CLOSE TO THE AXIS
OF INVERTED SURFACE TROUGH. WILL AGAIN LEAVE AS TEMPO VERSUS
CATEGORICAL. CONDITIONAL 850MB-WATER SURFACE TEMPERATURE
DIFFERENTIAL AND LITTLE TO NO MOISTENING ABOVE THE -10C LEVEL ON
FORECAST SOUNDINGS WILL LIMIT LAKE-EFFECT SNOW POTENTIAL AT KMKE AND
KENW.

MARINE...

WINDS AND WAVES WILL APPROACH SMALL CRAFT ADVISORY LEVELS
TUESDAY...AND WILL LIKELY REACH CRITERIA TUESDAY NIGHT WITH
INCREASING NORTHEAST WINDS AS PRESSURE GRADIENT TIGHTENS OVER REGION
AS LOW PRESSURE MOVES THROUGH TO THE SOUTH OF THE WESTERN GREAT
LAKES. THERE IS A CHANCE FOR LAKE-EFFECT SNOW SHOWERS TODAY IN THE
NEARSHORE WATERS...WITH THE CHANCE MOVING OUT TOWARD MID-LAKE BY
THIS EVENING AS WINDS TURN TO THE NORTH.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$
TODAY/TONIGHT AND AVIATION/MARINE...REM
TUESDAY THROUGH SUNDAY...WOOD