Forecast Discussions mentioning any of
"HRRR" "RR" "RUC13" "RUC" received at GSD on 12/18/11
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
402 PM EST FRI DEC 16 2011
.SYNOPSIS...
HIGH PRESSURE BUILDING OVER THE AREA HAS PUSHED A FRONTAL SYSTEM
WELL TO OUR SOUTH. A WAVE OF LOW PRESSURE WILL MOVE EAST ALONG THE
FRONT OVERNIGHT AND LIKELY BRING SOME LIGHT RAIN OR SNOW TO DELMARVA
AND FAR SOUTHERN NEW JERSEY. HIGH PRESSURE WILL THEN BRING FAIR
WEATHER FOR THE WEEKEND AND EARLY NEXT WEEK WITH A WARMING TREND
AFTER SUNDAY. LOW PRESSURE APPROACHING FROM THE SOUTHWEST COULD
BRING MORE RAIN AROUND THE MIDDLE OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
HIGH POPS FOR MID LVL FGEN GENERATED SNOW MELTING IN THE BL OVER S
DE TO CAPE MAP NJ BETWEEN 23Z-08Z. THE 12Z/16 EC WHICH IS RELATIVELY
DRY AT 950 AND 850 MB IS STILL OFFERING QPF WHERE WE HAVE IT IN THE
GRIDS FOR 3 SUCCESSIVE 6 HR PERIODS. THIS PLUS THE QPF EVALUATION
BELOW SUPPORT THE HIGH PROB LOW QPF EVENT FAR S EDGE OF THE FA FOR A
TIME TONIGHT.
18Z 6 HR PCPN EVALUATION FROM 12Z/16 MODELS: THE UKMET APPEARS
TO BE TOO SLOW AND TOO FAR SOUTH AT 18Z WITH ITS MASS FIELDS OF RH.
THEREFORE IT WAS NOT A SIGNIFICANT CONSIDERATION IN THE AFTERNOON
FCST. NAM WAS TOO SLOW AND TOO FAR SOUTH AS WELL. 18Z NAM LOOKS
BETTER AND CONTINUES THE QPF TREND OF ITS PREDECESSOR TO VCNTY
KDOV-KWWD LINE TONIGHT.
15Z SREF HAS COME AROUND TO THE FURTHER N SOLN...USUALLY HANGING ON
THE COATTAILS OF ITS 12Z NAM RUN. SO...THE 12Z GFS OP AND 12Z/16 EC
COMBO LOOK BEST FOR RAPID EXTRAPOLATION ENEWD WITH CONTD SUPPORT
FROM THE 18Z NAM AND 15Z SREF. THE 12Z GEFS PROB FOR .05 WAS VERY
GOOD AT 18Z AND THE 98 PCT PROB FOR .05 IN S DE ENDING AT 06Z LOOKS
LIKE A VERY GOOD FCST ATTM. 15Z SREF .01 PROB NOW UP TO 70 PCT IN S
DE.
SO WHILE A COUPLE OF 12Z/16 NON NCEP MODELS APPEAR TOO SLOW AND
TOO FAR SOUTH ... CONFIDENCE FOR A CATEGORICAL EVENT IS A LITTLE
LESS THAN IDEAL BUT STILL ABOVE AVG FOR S DE AND POSSIBLY CAPE MAY
NJ.
MESOSCALE MODELS: 12Z SPC WRF IS A DECENT FIT FOR REALITY AT 18Z AND
A FCST WHICH IS FASTER AND FURTHER N THAN ITS 00Z VSN. STILL LOOKS A
LITTLE SLOW AT 20Z! 17Z HRRR LOOKS SLOW AND LIGHT IN SW VA BUT EVEN
IT SPREADS QPF INTO S DE BY 03Z!
FGEN ON THE 12Z GFS LOOKS DECENT IN MID ATLC STATES S AND SE OF PHL
TONIGHT.
INITIALLY RAIN ONSET LATE THIS AFTN IN FAR SW DEL BUT COLUMN WET
BULBING DURING HEAVIER PCPN TONIGHT SHOULD PERMIT A CHG TO MIXED OR
ALL SNOW FOR A TIME WHERE IT HEAVIEST...ESP FAR S DE. EXCT DENDRITIC
GROWTH EARLY ON WITH UP TO 20MB LIFT IN THE SATURATED IDEAL DENDRITE
GROWTH ZONE BUT ALAS...BL TOO WARM IN S DE ON THE EARLY SIDE OF THE
PCPN EVENT.
STILL WONT BE SURPRISED AT ISOLATED .5 INCH SNOW ACC IN S DE BETWEEN
03Z-08Z. SNOW TOOLS OFFER .2.
BASED ON HOW DRY THE AIRMASS LOOKS TO BE...NORTH OF A KILG-KACY LINE
THE FORECAST WILL STILL BE DRY.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
SATURDAY...MIXED SUN AND CLOUDS WITH AN INCREASINGLY GUSTY NW WIND
TO 20 OR 25 MPH SEASONABLY COOL TEMPS AS HIGH PRES SLOWLY EDGES INTO
THE REGION. DECENT LOW LVL LAPSE RATES FOR MOMENTUM TRANSFER...NOT
THAT MUCH WIND IN THE COLUMN.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
THIS FCST PERIOD STARTS OUT WITH AN UPPER TROF OVER THE EASTERN US
BUT THE TROF AXIS SHIFTS OFFSHORE BY SUNDAY NIGHT. A SHRTWV DIGGING
SEWD FROM THE WERN GRTLKS ON SUNDAY WILL BRING SOME CLOUDINESS BUT
DOESN`T HAVE ENOUGH MOISTURE TO WORK WITH TO CAUSE ANY SGFNT PRECIP.
THE COLDEST TEMPS...JUST SLIGHTLY BELOW NORMAL...WILL BE ON SUNDAY.
THEN WARMER AIR ADVECTS IN FROM WEST FOR MONDAY.
CONDITIONS SHOULD BE DRY FOR EARLY NEXT WEEK, BUT THEN POPS INCREASE
TOWARD MID-WEEK AS THE UPPER LOW NOW OVER SOCAL IS KICKED OUT AND
THE ASSOCD TROF MOVES INTO THE ERN U.S. THE 12Z RUNS OF THE GFS AND
ECMWF ARE ACTUALLY IN RATHER GOOD AGREEMENT ON THE TIMING OF THIS
SYSTEM MOVG ACROSS THE MID-ATLANTIC ON WED. WE HAVE SLGT CHC POPS
FOR TUES AS A COLD FRONT PUSHES S ACROSS THE ARRE AND THEN STALL.
HWVR...THE BEST LIKELIHOOD IS TUES NIGHT INTO WED AS SFC LOW PRES
TRACKS FROM THE MID MISS VLY NEWD INTO THE LOWER GRTLKS. TEMPS
SHOULD BE WARM ENOUGH DURG THIS TIME FOR ALL RAIN...EXCEPT PERHAPS
SOME MIXED PRECIP AT THE BEGINNING OR END OVER NEPA/NWNJ.
THE GFS AND ECMWF DIFFER CONSIDERABLE ON THE SYSTEM WHICH COULD
AFFECT US LATE NEXT WEEK...WITH THE ECMWF KEEPING MOST PRECIP AWAY
TO OUR SOUTH. WE FOLLOW THE HPC GUIDANCE FOR FRIDAY WHICH HAS CHC
POPS OVER OUR AREA. TEMPS AGAIN LOOK TOO WARM FOR SNOW WITH A
CONTINUING PATTERN OF ABOVE NORMAL WARMTH.
&&
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
REMAINDER OF THIS AFTERNOON...VFR WITH CIGS AOA 12000 FT. TPHL VWP
HAS A NICE LOOK TO THE LOWERING CIRRUS DECK.
GUSTY NW WINDS GUSTY TO LESS THAN 18 KTS AND DIMINISHING FURTHER
THIS AFTN.
FOR TONIGHT...VFR CIGS AOA 5000 FT. LIGHT MOSTLY NW WIND.
OVER PHL...IT SHOULD BE SNOWING DOWN TO ABOUT 3000 OR 4000 FT BEFORE
EVAPORATING /VWP AT TPHL SHOULD BE HELPFUL/. KILG LOW PROBABILITY MAY
SEE AN HR OF RAIN OR R/S 03Z-05Z TIME FRAME?
OTRW...S DEL SHOULD SEE SNOW ALOFT CHANGE TO RAIN OR MXD SNOW/RAIN AT
THE SFC BUT NOT IMPOSSIBLE TO SEE AN HR OF 1MI WET SNOW VCNTY KGED TWD
05Z?
SATURDAY...VFR. SCT-BKN CLDS AOA 5000 FT EXPECTED. NW WIND SHOULD
GRADUALLY INCREASE WITH GUSTS TO 20 KTS.
OUTLOOK...
MAINLY VFR FLYING CONDITIONS EXPECTED SATUDAY NIGHT THROUGH
TUESDAY. CONDS WILL LIKELY BECOME WORSE TUESDAY NIGHT INTO
WEDNESDAY AS A LOW PRESSURE SYSTEM BRINGS RAIN INTO THE AREA.
&&
.MARINE...
SCA FOR DE ATLC WATERS EXTENDED TIL 6P. OTRW NO HEADLINES THRU AT
LEAST 18Z SAT.
A WEAK SURFACE LOW WILL PASS WELL SOUTH OF THE WATERS TONIGHT.
THE GRADIENT BEHIND THE LOW WILL NOT INCREASE UNTIL LATE TONIGHT.
NW WINDS ON SATURDAY MAY INCREASE TO SCA CRITERIA...ESP DE WATERS
AND ESP SAT AFTN...BUT FOR NOW MULTI MODEL TOOLS DO NOT OFFER MUCH
SUPPORT FOR AN SCA.
OUTLOOK...
NW WINDS SATURDAY NIGHT WILL DIMINISH AS HIGH PRES MOVES OVER THE
AREA...THEN WILL BECOME SW AND INCREASE ON MONDAY AS THE HIGH
MOVES OFFSHORE. SCA CONDS ARE POSSIBLE AROUND DTHIS TIME.
A FRONTAL SYSTEM WILL CROSS THE AREA TUESDAY BUT ASSOCD WINDS
SHOULD BE RELATIVELY LIGHT. WINDS SHOULD INCR AGAIN FROM THE SW
AND THEN SHIFT TO NW WED NIGHT AS LOW PRES AND ASSOCD CDFNT MOVE
ACROSS THE AERA. SCA CONDS ARE AGAIN POSSIBLE AT THIS TIME.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ454-
455.
&&
$$
SYNOPSIS...AMC
NEAR TERM...DRAG
SHORT TERM...DRAG
LONG TERM...AMC
AVIATION...DRAG
MARINE...AMC/DRAG
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
905 PM EST Sat Dec 17 2011
.UPDATE...
02Z water vapor and H4 RUC analysis shows a somewhat amplified
northern stream flow in place across North America. Flow arrives
over the British Columbia coast as it crests the top of a large and
dominant ridge in place across the western CONUS. The flow then
dives back to the southeast across the northern plains/northern MS
valley into amplified troughing along the eastern seaboard. The
base of the eastern US trough extends down into northern AL/GA with
a more zonal flow pattern still in place along the Northern Gulf
Coast. Only other feature of note, is a large cutoff low spinning
over southern CA and the Baja region.
Pleasant evening underway across the forecast area as surface high
pressure slowly builds in from the west. Surface high is actually
quite strong with pressures around 1030mb centered near the Arklatex
region. Continue to see a slow advection of cooler and drier air
into the region in the wake of this morning`s cold front. Skies are
clear out there this evening, and one look at the 00Z KTLH sounding
shows why. The profile aloft is very dry through the column with a
PW of only around 0.2". This value is only about 20% of climatology
for the middle of December.
With all this in mind, the rest of the overnight will feature dry,
clear, and cool conditions. Temperatures will be slowly falling
through the night reaching generally the middle 30s north and middle
30s to lower 40s in the south. Previous forecast still looks on
track, and don`t see much reason to make significant changes based
on the 18Z guidance package. Agree with the previous forecast
philosophy of keeping temps up a couple of degrees from the MAV
numbers. The gradient in place on the east side of the high will
likely prevent boundary layer de-coupling, and therefore do not
anticipate any freezing or subfreezing temperatures. Really not
anticipating much frost either, despite temps in the middle 30s. The
light winds, and the fact that dewpoint depressions by sunrise are
expected to range from 5-8 degrees, suggests significant frost
formation will be difficult.
A dry and seasonable day on tap for your Sunday. Expecting plenty of
sunshine and high temperatures in the 60s.
&&
.AVIATION...thru 00z Mon.
Expect VFR condition thru the period. Light northwest winds will
increase to north 5 to 10 mph after 9am est Sun.
&&
.MARINE...High pressure across the Mid Mississippi River Valley will
keep the pressure gradient tight across the marine area overnight.
The tighter gradient and continued cold air advection should support
a period of advisory winds across the offshore waters later tonight,
with cautionary level winds closer to the coast. These winds are
expected to subside by Sunday afternoon as high pressure gets a
little closer to the marine area. Winds will be on the increase out
of the southeast by Tuesday as the pressure gradient tightens ahead
of the next weather system. Cautionary to advisory level winds
appear possible with this next system as well.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 35 64 35 69 51 / 0 0 0 0 05
Panama City 41 63 44 67 56 / 0 0 0 0 10
Dothan 34 61 35 68 51 / 0 0 0 0 10
Albany 33 61 34 68 51 / 0 0 0 0 05
Valdosta 35 63 36 70 48 / 0 0 0 0 05
Cross City 38 66 38 72 48 / 0 0 0 0 05
Apalachicola 42 63 43 67 55 / 0 0 0 0 05
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
AL...None.
GA...None.
FL...None.
GM...Small Craft Advisory from Midnight tonight to 10 AM EST Sunday
from Destin to the Suwannee River between 20 and 60 nautical
miles from shore.
&&
$$
UPDATE/MARINE...MROCZKA
AVIATION...BLOCK
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
918 PM CST SAT DEC 17 2011
.DISCUSSION...
849 PM CST
FORECAST CONCERNS/CHALLENGES ARE WITH SKY COVER TONIGHT...AS I AM
LITTLE CONCERNED CLOUD COVER MAY LINGER A LITTLE BIT LONGER THAN
PREVIOUSLY THOUGHT...AS WELL AS FOG DEVELOPMENT.
LARGE SCALE TROUGH WILL CONTINUE TO PUSH EAST TONIGHT WITH
ATTENDANT TROUGH OF LOW PRESSURE TO THE NORTH QUICKLY SHIFTING
EAST THROUGH NORTHERN MICHIGAN. MEANWHILE ACROSS THE CWA...SURFACE
RIDGE AXIS WILL SHIFT OVERHEAD WITH WINDS BECOMING MORE LIGHT AND
VARIABLE. ALTHOUGH...WEAK RIDGING ALOFT COINCIDING WITH A WAVE
SHIFTING SOUTHEAST ACROSS CANADA WILL ALLOW LOW/MID LEVEL WINDS TO
BACK MORE TO THE WEST/SOUTHWEST...WITH LATEST RUC ANALYSIS ALREADY
SHOWING THIS BEGINNING TO OCCUR. THIS IS THE START OF A PERIOD OF
WAA ACROSS MUCH OF THE REGION. ITS THIS WAA/WEAK FORCING RIDING
OVER A MOIST BOUNDARY LAYER FROM HIGHER DEWPOINT AIR AS WELL AS
THE RECENT SNOW...WHICH COULD HELP PROVIDE THE REDEVELOPMENT OF
LOW CEILINGS TONIGHT. CLEARING CURRENTLY ONGOING ACROSS A PORTION
OF NORTHERN ILLINOIS AND NORTHWEST INDIANA MAY INITIALLY BE
HINDERED BY THE LARGE CLOUD SHIELD SHIFTING EAST/SOUTHEAST ACROSS
MUCH OF WISCONSIN. THIS CLOUD SHIELD HAS SHOWN MORE OF A SOUTHERLY
PUSH RECENTLY AND THINK THAT IT WILL LINGER INTO NORTHEAST
ILLINOIS AND NORTHWEST ILLINOIS OVER THE NEXT COUPLE OF HOURS
BEFORE IT COMPLETELY EXITS TO THE EAST. ALTHOUGH...ITS DURING THIS
CLEARING TREND THAT THE REDEVELOPMENT OF LOW CEILINGS/FOG WILL BE
POSSIBLE ACROSS MOST OF THE CWA. THIS CLEARING AND LIGHTER WINDS
IN PLACE WILL ALLOW FOR GOOD RADIATIONAL COOLING TO
CONTINUE...WITH SEVERAL SITES ALREADY SHOWING RAPID TEMPERATURE
DROPS THIS EVENING.
WITH THESE CONCERNS IN MIND...THE RUC/VSREF HAVE BEEN HINTING AT
THE POSSIBILITY OF LOW CEILINGS/VIS WITH LOCATIONS NEAR
DEKALB/ROCHELL ALREADY SHOWING THESE TRENDS. ALTHOUGH AREAS OF FOG
WILL CONTINUE TO DEVELOP TONIGHT WITH SOME SITES OBSERVING VIS
AROUND THE 1-2SM RANGE...DONT THINK VIS WILL REMAIN THIS LOW WITH
STRATUS THEN DEVELOPING. LATEST GUIDANCE CONTINUES TO SHOW THAT
THERE WILL BE ENOUGH MOMENTUM IN THE BOUNDARY LAYER TO FAVOR
STRATUS.
THERE IS STILL UNCERTAINTY WITH SKY COVER TONIGHT...BUT HAVE
TRENDED MORE PESSIMISTIC IN THE GRIDS AND HAVE STARTED THE TREND
TOWARDS MORE CLOUDY SKIES BY SUNDAY MORNING. WILL LEAVE PARTLY
CLOUDY SKIES LATE TONIGHT BUT WILL HAVE TO CONTINUE TO MONITOR
LATEST TRENDS AND ADJUST ACCORDINGLY. HAVE ONLY MADE SOME MINOR
TEMP ADJUSTMENTS TONIGHT...MAINLY TO ACCOUNT FOR THE RAPID COOLING
IN AREAS WHICH HAVE ALREADY OBSERVED CLEAR SKIES.
RODRIGUEZ
//PREV DISCUSSION...
350 PM
LATE AFTERNOON THROUGH MONDAY...
AT MID AFTERNOON ANOTHER SHORT WAVE TROUGH MOVING EAST-SOUTHEAST
ACROSS LAKE SUPERIOR AND THE U.P. OF MI...TRAILING RIGHT BEHIND
THE SHORT WAVE...CURRENTLY OVER THE SOUTH CENTRAL GREAT LAKES
REGION...THAT GAVE AN INCH OR TWO TO MUCH OF OF SNOW TO MUCH OF
NORTH CENTRAL AND FAR NORTHEAST IL LATE LAST NIGHT AND THIS
MORNING...WITH LESSER AMOUNTS FURTHER SOUTH. THIS SECOND SHORT
WAVE WILL TRACK TOO FAR TO OUR NORTH AND NORTHEAST TO THREATEN
THE LOCAL AREA WITH ANY ADDITIONAL LIGHT SNOWFALL TONIGHT.
WIDESPREAD STRATOCUMULUS EXTENDS FROM IND NORTHWESTWARD ACROSS
EAST CENTRAL AND NORTHERN IL...ALL OF WI AND THE SOUTHEAST CORNER
OF MN. WHILE MODEL FORECAST TEMPERATURE AND DEW POINT DEPRESSION
PROFILES AS WELL AS PLAN DISPLAYS OF LOWER LEVEL RH FIELDS SHOW
THESE CLOUDS GRADUALLY CLEARING WEST TO E DURING THE LATE EVENING
AND EARLY A.M. HOURS THIS APPEARS TO BE A BIT FAST AND DO NOT
EXPECT TO SEE SIGNIFICANT CLEARING OVER THE EASTERN PORTIONS OF
THE FORECAST AREA UNTIL THE PRE-DAWN HOURS WHEN THE SECOND SHORT
WAVE TROUGH REACHES THE CENTRAL GREAT LAKES AND A SURFACE RIDGE
SHIFTS EAST ACROSS THE MS RIVER AND OVER THE LOCAL AREA BY 12Z
SUN.
RIDGING ALOFT SPREADS EAST FROM THE NORTHERN PLAINS TO OVER THE
UPPER MIDWEST AND THE LOCAL FORECAST AREA DURING SUNDAY MORNING
BETWEEN THE DEPARTING GREAT LAKES TROUGH AND ANOTHER SHORT WAVE
DIGGING SOUTHEAST OVER ALBERTA AND NORTHERN SASKATCHEWAN. RIDGING
SURFACE AND ALOFT ALONG WITH LOWER LEVEL WINDS BACKING TO SOUTH-
SOUTHWEST AND SOUTHWEST SUNDAY EXPECTED TO BE MOSTLY SUNNY AND
MILD FOR MID DECEMBER WITH TEMPERATURES UP INTO THE LOWER AND
MID 40S FOR THE AFTERNOON. A COLD FRONT EXTENDING FROM A SURFACE
LOW ASSOCIATED WITH THE SECOND SHORT WAVE SWEEPS ACROSS THE
REGION MONDAY NIGHT RETURNING COLDER AIR BUT TEMPERATURES STILL
EXPECTED TO BE FROM AROUND TO A BIT ABOVE NORMALS FOR THE DATE.
TUESDAY THROUGH SATURDAY...
THOUGHTS TURN TO HOLIDAY TRAVEL PLANS FOR NEXT WEEK. AT THIS
POINT LOOKS TO BE PRETTY GOOD CONDITIONS FOR THE AREA AS NO MAJOR
WINTER WEATHER IS EXPECTED.
OVERALL THEME OF MODEL RUNS FROM LAST NIGHT WAS THE IDEA OF LESS
PHASING OF THE CUT-OFF UPPER LOW TO BE OVER THE AZ/MEXICO BORDER
LATE SUNDAY AND A NORTHERN JET STREAM SHORT WAVE MOVING FROM
SOUTHERN B.C. AND THE PACIFIC NORTHWEST SOUTHEASTWARD TO THE
NORTHERN PLAINS...AND THEN EASTWARD ACROSS THE NORTHERN PLAINS
AND THE UPPER MIDWEST...FINALLY REACHING THE WESTERN GREAT LAKES
TUESDAY EVENING. MODEL RUNS FROM THIS MORNING AND MIDDAY
INCLUDING INDIVIDUAL ENSEMBLE MEMBERS MAINTAIN THEIR MEMBER TO
MEMBER...RUN TO RUN...AND MODEL TO MODEL AGREEMENT LEADING TO A
MORE SINGULAR SOLUTION. HOPEFULLY THIS WILL TURN OUT TO BE A
DECENT SOLUTION IF NOT THE BEST.
THIS MORE UNIFIED SOLUTION HAS THE CUT-OFF CLOSED UPPER
LOW...WHICH TAKES UP RESIDENCE OVER OR JUST WEST OF THE NORTHERN
BAJA PENINSULA TONIGHT INTO SATURDAY STARTING TO BE EJECTED BY A
DISTURBANCE DROPPING SOUTH-SOUTHEAST FROM THE GULF OF AK ALONG THE
PACIFIC COAST LATE SUNDAY THROUGH MONDAY. IN RESPONSE THE UPPER
LOW LIFTS NORTHEASTWARD OVER THE CENTRAL PLAINS TUESDAY AND THEN
GRADUALLY OPENS TO AN OPEN WAVE BY LATE WED AS IT CROSSES THE MID
MS VALLEY.
AS THE UPPER LOW/OPEN WAVE MOVES FROM THE EASTERN CENTRAL PLAINS
ACROSS THE MID MS VALLEY AND THE LOWER OH VALLEY LATE TUESDAY
NIGHT THROUGH WEDNESDAY IT WILL BASICALLY BE TRACKING TO THE EAST.
THIS KEEPS THE MAX PRECIP AXIS FROM MO EAST ACROSS SOUTHERN AND
CENTRAL IL AND THEN ACROSS IND...SOUTH OF THE LOCAL FORECAST AREA.
WHILE NORTHERN EDGE OF THE PRECIPITATION SHIELD IS EXPECTED TO
GRADUALLY CREEP FAR ENOUGH NORTHWARD TO GIVE AT LEAST CHANCE
THREAT OF PRECIPITATION FROM LATER MONDAY THROUGH WEDNESDAY.
PRECIPITATION STILL LOOKS TO BE RAIN WITH ONLY A VERY SMALL
THREAT OF MIXED RAIN AND SNOW OR LIGHT SNOW ACROSS THE FAR NORTH
COUNTIES TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE
PRECIPITATION IS MOVING OFF TO THE EAST. LIQUID FORM FAVORED AS
SIGNIFICANT COLD AIR IS HELD AT BAY WITH QUICK PROGRESSION OF
DISTURBANCES MOVING THROUGH THE NORTHERN STREAM NOT PERMITTING
ANY STRONG COLD AIR ADVECTION TO OCCUR BEFORE FLOW BACKS AS THE
NEXT SHORT WAVE APPROACHES.
A RATHER SIGNIFICANT SHORT WAVE IS PROGGED TO DROP ACROSS THE
UPPER MIDWEST...UPPER AND MOD MO VALLEY...AND THE UPPER GREAT
LAKES WEDNESDAY NIGHT...MOVING TO OVER THE CENTRAL GREAT LAKES
BY MIDDAY FRIDAY. HOWEVER...DURING THIS TIME MODELS CONTINUE TO
SHOW A VERY LARGE STRONG ANTICYCLONE SPRAWLED FROM TX TO THE OH
VALLEY AND SOUTHERN GREAT LAKES. THIS WILL KEEP ANY SIGNIFICANT
AWAY FROM THE REGION WITH ONLY A POTENTIAL OF MAINLY LAKE EFFECT
SNOWS DOWNWIND OF THE LAKES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* MVFR CIGS THROUGH THIS EVENING...THEN POTENTIAL FOR FOG/STRATUS
DEVELOPMENT AND POSSIBLE IFR AFTER CLEARING OUT MVFR DECK AFTER
MIDNIGHT.
* LIGHT WEST-SOUTHWEST WINDS BECOMING SOUTHWEST SUNDAY AND
BECOMING GUSTY 15-20 KTS SUNDAY AFTERNOON.
RATZER
//DISCUSSION...UPDATED 03Z...
MVFR DECK AROUND 2500 FT HAS FILLED IN A LITTLE FARTHER SOUTH INTO
NORTHEAST IL THIS EVENING...ROUGHLY ALONG/NORTH OF A KFEP TO KIKK
LINE AT 03Z. TRAILING EDGE OF THIS DECK OVER SOUTH CENTRAL WI
MAKING STEADY PROGRESS TO THE EAST-SOUTHEAST...AND SHOULD CLEAR
KRFD AFTER 04Z...AND KORD/KDPA/KMDW SHORTLY AFTER 06Z. CONCERNS
REMAIN THAT ONCE CLEARING OCCURS...THAT RADIATIONAL COOLING OVER
NEW SNOW COVER IN SHALLOW/MOIST BOUNDARY LAYER WILL ALLOW FOG AND
LOW STRATUS TO DEVELOP...AS IT DID IN A FEW SPOTS ACROSS NORTH
CENTRAL IL EARLIER THIS EVENING. QUICK GLANCE AT NEW 00Z WRF RUN
CONTINUES TO DEPICT SATURATION OF SHALLOW BOUNDARY LAYER OVERNIGHT
PARTICULARLY AT KRFD/KDPA...SO EARLIER AMENDMENT FOR THIS
POSSIBILITY STILL APPEARS ON TRACK. WILL CONTINUE TO MONITOR
UPSTREAM TRENDS FOR ADDITIONAL DETAIL WITH 06Z ISSUANCE.
RATZER
PREVIOUS DISCUSSION FROM 00Z...
EXTENSIVE AREA OF MAINLY MVFR CEILINGS REMAIN OVER MUCH OF
WISCONSIN...FAR NORTHEAST ILLINOIS AND INDIANA EARLY THIS EVENING.
WHILE CLEARING HAS OCCURRED ACROSS PORTIONS OF NORTHERN ILLINOIS...
GOES IR SATELLITE IMAGERY INDICATES A SOUTHEASTWARD DRIFT OF MVFR
CLOUDS ALONG A ROUGHLY PRAIRIE DU CHIEN TO JANESVILLE TO CHICAGO
LINE WHICH SUGGESTS MVFR CONDITIONS MAY CONTINUE TO BE AN ISSUE
FOR TERMINALS THIS EVENING. MID-LEVEL TROUGH AXIS OVERHEAD WILL BE
MOVING EAST OF THE FORECAST AREA BY MID-LATE EVENING...WHICH
SHOULD OTHERWISE AID IN CLEARING WITH INCREASING DEEP SUBSIDENCE
OVERNIGHT. HOWEVER...LITTLE DRYING OCCURRING IN THE LOW LEVELS...
AND THIS COMBINED WITH LOWERING SUBSIDENCE INVERSION AND NEW SNOW
COVER MAY POSSIBLY RESULT IN DEVELOPMENT OF LOW STRATUS OVER
PORTIONS OF THE AREA THAT HAVE CLEARED OUT. MOST MODEL GUIDANCE
IS NOT REALLY HANDLING THE DETAILS OF CURRENT CLOUD TRENDS VERY
WELL...THOUGH SOME OF THE SHORT RANGE ENSEMBLE GUIDANCE INCLUDING
VSREF RUNS DO INDEED DEPICT HIGHER PROBABILITIES OF CIGS BELOW
2000 FT INCREASING IN AREA ACROSS NORTHERN IL OVERNIGHT. LOW
CONFIDENCE IN HOW THIS WILL PLAY OUT EXACTLY...SO HAVE INDICATED
AN MVFR CIG THROUGH THIS EVENING SCATTERING TO A 1000 FT LAYER
AFTER MIDNIGHT. IN LIEU OF ADDING AN IFR CIG AT THIS TIME...WILL
CONTINUE TO MONITOR SATELLITE TRENDS AND WILL REFINE WITH LATER
AMENDMENTS. ANOTHER CONCERN IS IF WE DO DEVELOP A LOW STRATUS
CEILING OVERNIGHT IS GETTING RID OF IT IN THE MORNING.
IGNORING ANY MORNING STRATUS...IF IT FORMS TONIGHT...WOULD EXPECT
SOME PATCHY VFR MID/HIGH CLOUDS ON SUNDAY AS WARM ADVECTION
INCREASES ALOFT IN ASSOCIATION IN ASSOCIATION WITH ANOTHER UPPER
DISTURBANCE ALONG THE CANADIAN BORDER. MAIN AFFECT FOR TERMINALS
WILL BE WINDS...WHICH WILL SHIFT SOUTHWEST AND BECOME SOMEWHAT
GUSTY IN THE AFTERNOON IN RESPONSE TO DEEPENING LOW PRESSURE OVER
ONTARIO. FORECAST SOUNDINGS INDICATE 15-20 KT GUST POTENTIAL IN
MIXED LAYER DURING THE AFTERNOON.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* MEDIUM-LOW CONFIDENCE ON POTENTIAL IFR CIG TRENDS AFTER
MIDNIGHT.
* HIGH CONFIDENCE IN WIND TRENDS THROUGH PERIOD.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN...PSBLY MIXED WITH SNOW AT
ONSET TUES. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
RATZER
&&
.MARINE...
219 PM CST
A PROGRESSIVE WEATHER PATTERN ACROSS THE GREAT LAKES WILL CONTINUE
TO USHER MULTIPLE GUSTY SYSTEMS OVER THE REGION THE NEXT COUPLE OF
DAYS. THE FIRST ONE CENTERED OVER NORTHERN ONTARIO TONIGHT WILL
SWING A TROUGH THROUGH LAKE MICHIGAN THROUGH THE EVENING...TURNING
WINDS TO THE WEST...EVEN SLIGHTLY NORTHWEST IN PARTS OF THE OPEN
WATER. SOME WINDS UP TO 30 KTS ARE POSSIBLE WITH THIS
REGIME...MAINLY IN THE NORTH CLOSER TO THE SYSTEM. A STRONGER LOW
PRESSURE NORTH OF LAKE SUPERIOR WILL RACE EAST ON SUNDAY AFTERNOON
AND EVENING...SWEEPING A COLD FRONT THROUGH THE LAKE SUNDAY NIGHT
INTO EARLY MONDAY. THE TIGHT GRADIENT AROUND THIS LOW AND DEEPER
MIXING WILL SUPPORT GALES ACROSS THE LAKE BEGINNING LATE SUNDAY
AFTERNOON OVER THE NORTH AND SUNDAY EVENING OVER THE SOUTH. THE
WINDOW OF TIME FOR THE GALES WILL BE SHORT...ONLY THROUGH SUNDAY
NIGHT...DUE TO THE QUICK MOVEMENT OF THE SYSTEM. PREVAILING WAVES
UP TO 14 FT ARE EXPECTED ACROSS OPEN WATERS OF THE FAR NORTH. THE
NORTHWEST FLOW BEHIND THE FRONT WILL STILL BE BREEZY ON MONDAY
DESPITE THE WIND SPEEDS GRADUALLY DIMINISHING. HIGH PRESSURE WILL
MOVE OVER THE LAKE MONDAY NIGHT INTO THE DAY TUESDAY.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
850 PM CST SAT DEC 17 2011
.DISCUSSION...
849 PM CST
FORECAST CONCERNS/CHALLENGES ARE WITH SKY COVER TONIGHT...AS I AM
LITTLE CONCERNED CLOUD COVER MAY LINGER A LITTLE BIT LONGER THAN
PREVIOUSLY THOUGHT...AS WELL AS FOG DEVELOPMENT.
LARGE SCALE TROUGH WILL CONTINUE TO PUSH EAST TONIGHT WITH
ATTENDANT TROUGH OF LOW PRESSURE TO THE NORTH QUICKLY SHIFTING
EAST THROUGH NORTHERN MICHIGAN. MEANWHILE ACROSS THE CWA...SURFACE
RIDGE AXIS WILL SHIFT OVERHEAD WITH WINDS BECOMING MORE LIGHT AND
VARIABLE. ALTHOUGH...WEAK RIDGING ALOFT COINCIDING WITH A WAVE
SHIFTING SOUTHEAST ACROSS CANADA WILL ALLOW LOW/MID LEVEL WINDS TO
BACK MORE TO THE WEST/SOUTHWEST...WITH LATEST RUC ANALYSIS ALREADY
SHOWING THIS BEGINNING TO OCCUR. THIS IS THE START OF A PERIOD OF
WAA ACROSS MUCH OF THE REGION. ITS THIS WAA/WEAK FORCING RIDING
OVER A MOIST BOUNDARY LAYER FROM HIGHER DEWPOINT AIR AS WELL AS
THE RECENT SNOW...WHICH COULD HELP PROVIDE THE REDEVELOPMENT OF
LOW CEILINGS TONIGHT. CLEARING CURRENTLY ONGOING ACROSS A PORTION
OF NORTHERN ILLINOIS AND NORTHWEST INDIANA MAY INITIALLY BE
HINDERED BY THE LARGE CLOUD SHIELD SHIFTING EAST/SOUTHEAST ACROSS
MUCH OF WISCONSIN. THIS CLOUD SHIELD HAS SHOWN MORE OF A SOUTHERLY
PUSH RECENTLY AND THINK THAT IT WILL LINGER INTO NORTHEAST
ILLINOIS AND NORTHWEST ILLINOIS OVER THE NEXT COUPLE OF HOURS
BEFORE IT COMPLETELY EXITS TO THE EAST. ALTHOUGH...ITS DURING THIS
CLEARING TREND THAT THE REDEVELOPMENT OF LOW CEILINGS/FOG WILL BE
POSSIBLE ACROSS MOST OF THE CWA. THIS CLEARING AND LIGHTER WINDS
IN PLACE WILL ALLOW FOR GOOD RADIATIONAL COOLING TO
CONTINUE...WITH SEVERAL SITES ALREADY SHOWING RAPID TEMPERATURE
DROPS THIS EVENING.
WITH THESE CONCERNS IN MIND...THE RUC/VSREF HAVE BEEN HINTING AT
THE POSSIBILITY OF LOW CEILINGS/VIS WITH LOCATIONS NEAR
DEKALB/ROCHELL ALREADY SHOWING THESE TRENDS. ALTHOUGH AREAS OF FOG
WILL CONTINUE TO DEVELOP TONIGHT WITH SOME SITES OBSERVING VIS
AROUND THE 1-2SM RANGE...DONT THINK VIS WILL REMAIN THIS LOW WITH
STRATUS THEN DEVELOPING. LATEST GUIDANCE CONTINUES TO SHOW THAT
THERE WILL BE ENOUGH MOMENTUM IN THE BOUNDARY LAYER TO FAVOR
STRATUS.
THERE IS STILL UNCERTAINTY WITH SKY COVER TONIGHT...BUT HAVE
TRENDED MORE PESSIMISTIC IN THE GRIDS AND HAVE STARTED THE TREND
TOWARDS MORE CLOUDY SKIES BY SUNDAY MORNING. WILL LEAVE PARTLY
CLOUDY SKIES LATE TONIGHT BUT WILL HAVE TO CONTINUE TO MONITOR
LATEST TRENDS AND ADJUST ACCORDINGLY. HAVE ONLY MADE SOME MINOR
TEMP ADJUSTMENTS TONIGHT...MAINLY TO ACCOUNT FOR THE RAPID COOLING
IN AREAS WHICH HAVE ALREADY OBSERVED CLEAR SKIES.
RODRIGUEZ
&&
.PREV DISCUSSION...
350 PM
LATE AFTERNOON THROUGH MONDAY...
AT MID AFTERNOON ANOTHER SHORT WAVE TROUGH MOVING EAST-SOUTHEAST
ACROSS LAKE SUPERIOR AND THE U.P. OF MI...TRAILING RIGHT BEHIND
THE SHORT WAVE...CURRENTLY OVER THE SOUTH CENTRAL GREAT LAKES
REGION...THAT GAVE AN INCH OR TWO TO MUCH OF OF SNOW TO MUCH OF
NORTH CENTRAL AND FAR NORTHEAST IL LATE LAST NIGHT AND THIS
MORNING...WITH LESSER AMOUNTS FURTHER SOUTH. THIS SECOND SHORT
WAVE WILL TRACK TOO FAR TO OUR NORTH AND NORTHEAST TO THREATEN
THE LOCAL AREA WITH ANY ADDITIONAL LIGHT SNOWFALL TONIGHT.
WIDESPREAD STRATOCUMULUS EXTENDS FROM IND NORTHWESTWARD ACROSS
EAST CENTRAL AND NORTHERN IL...ALL OF WI AND THE SOUTHEAST CORNER
OF MN. WHILE MODEL FORECAST TEMPERATURE AND DEW POINT DEPRESSION
PROFILES AS WELL AS PLAN DISPLAYS OF LOWER LEVEL RH FIELDS SHOW
THESE CLOUDS GRADUALLY CLEARING WEST TO E DURING THE LATE EVENING
AND EARLY A.M. HOURS THIS APPEARS TO BE A BIT FAST AND DO NOT
EXPECT TO SEE SIGNIFICANT CLEARING OVER THE EASTERN PORTIONS OF
THE FORECAST AREA UNTIL THE PRE-DAWN HOURS WHEN THE SECOND SHORT
WAVE TROUGH REACHES THE CENTRAL GREAT LAKES AND A SURFACE RIDGE
SHIFTS EAST ACROSS THE MS RIVER AND OVER THE LOCAL AREA BY 12Z
SUN.
RIDGING ALOFT SPREADS EAST FROM THE NORTHERN PLAINS TO OVER THE
UPPER MIDWEST AND THE LOCAL FORECAST AREA DURING SUNDAY MORNING
BETWEEN THE DEPARTING GREAT LAKES TROUGH AND ANOTHER SHORT WAVE
DIGGING SOUTHEAST OVER ALBERTA AND NORTHERN SASKATCHEWAN. RIDGING
SURFACE AND ALOFT ALONG WITH LOWER LEVEL WINDS BACKING TO SOUTH-
SOUTHWEST AND SOUTHWEST SUNDAY EXPECTED TO BE MOSTLY SUNNY AND
MILD FOR MID DECEMBER WITH TEMPERATURES UP INTO THE LOWER AND
MID 40S FOR THE AFTERNOON. A COLD FRONT EXTENDING FROM A SURFACE
LOW ASSOCIATED WITH THE SECOND SHORT WAVE SWEEPS ACROSS THE
REGION MONDAY NIGHT RETURNING COLDER AIR BUT TEMPERATURES STILL
EXPECTED TO BE FROM AROUND TO A BIT ABOVE NORMALS FOR THE DATE.
TUESDAY THROUGH SATURDAY...
THOUGHTS TURN TO HOLIDAY TRAVEL PLANS FOR NEXT WEEK. AT THIS
POINT LOOKS TO BE PRETTY GOOD CONDITIONS FOR THE AREA AS NO MAJOR
WINTER WEATHER IS EXPECTED.
OVERALL THEME OF MODEL RUNS FROM LAST NIGHT WAS THE IDEA OF LESS
PHASING OF THE CUT-OFF UPPER LOW TO BE OVER THE AZ/MEXICO BORDER
LATE SUNDAY AND A NORTHERN JET STREAM SHORT WAVE MOVING FROM
SOUTHERN B.C. AND THE PACIFIC NORTHWEST SOUTHEASTWARD TO THE
NORTHERN PLAINS...AND THEN EASTWARD ACROSS THE NORTHERN PLAINS
AND THE UPPER MIDWEST...FINALLY REACHING THE WESTERN GREAT LAKES
TUESDAY EVENING. MODEL RUNS FROM THIS MORNING AND MIDDAY
INCLUDING INDIVIDUAL ENSEMBLE MEMBERS MAINTAIN THEIR MEMBER TO
MEMBER...RUN TO RUN...AND MODEL TO MODEL AGREEMENT LEADING TO A
MORE SINGULAR SOLUTION. HOPEFULLY THIS WILL TURN OUT TO BE A
DECENT SOLUTION IF NOT THE BEST.
THIS MORE UNIFIED SOLUTION HAS THE CUT-OFF CLOSED UPPER
LOW...WHICH TAKES UP RESIDENCE OVER OR JUST WEST OF THE NORTHERN
BAJA PENINSULA TONIGHT INTO SATURDAY STARTING TO BE EJECTED BY A
DISTURBANCE DROPPING SOUTH-SOUTHEAST FROM THE GULF OF AK ALONG THE
PACIFIC COAST LATE SUNDAY THROUGH MONDAY. IN RESPONSE THE UPPER
LOW LIFTS NORTHEASTWARD OVER THE CENTRAL PLAINS TUESDAY AND THEN
GRADUALLY OPENS TO AN OPEN WAVE BY LATE WED AS IT CROSSES THE MID
MS VALLEY.
AS THE UPPER LOW/OPEN WAVE MOVES FROM THE EASTERN CENTRAL PLAINS
ACROSS THE MID MS VALLEY AND THE LOWER OH VALLEY LATE TUESDAY
NIGHT THROUGH WEDNESDAY IT WILL BASICALLY BE TRACKING TO THE EAST.
THIS KEEPS THE MAX PRECIP AXIS FROM MO EAST ACROSS SOUTHERN AND
CENTRAL IL AND THEN ACROSS IND...SOUTH OF THE LOCAL FORECAST AREA.
WHILE NORTHERN EDGE OF THE PRECIPITATION SHIELD IS EXPECTED TO
GRADUALLY CREEP FAR ENOUGH NORTHWARD TO GIVE AT LEAST CHANCE
THREAT OF PRECIPITATION FROM LATER MONDAY THROUGH WEDNESDAY.
PRECIPITATION STILL LOOKS TO BE RAIN WITH ONLY A VERY SMALL
THREAT OF MIXED RAIN AND SNOW OR LIGHT SNOW ACROSS THE FAR NORTH
COUNTIES TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE
PRECIPITATION IS MOVING OFF TO THE EAST. LIQUID FORM FAVORED AS
SIGNIFICANT COLD AIR IS HELD AT BAY WITH QUICK PROGRESSION OF
DISTURBANCES MOVING THROUGH THE NORTHERN STREAM NOT PERMITTING
ANY STRONG COLD AIR ADVECTION TO OCCUR BEFORE FLOW BACKS AS THE
NEXT SHORT WAVE APPROACHES.
A RATHER SIGNIFICANT SHORT WAVE IS PROGGED TO DROP ACROSS THE
UPPER MIDWEST...UPPER AND MOD MO VALLEY...AND THE UPPER GREAT
LAKES WEDNESDAY NIGHT...MOVING TO OVER THE CENTRAL GREAT LAKES
BY MIDDAY FRIDAY. HOWEVER...DURING THIS TIME MODELS CONTINUE TO
SHOW A VERY LARGE STRONG ANTICYCLONE SPRAWLED FROM TX TO THE OH
VALLEY AND SOUTHERN GREAT LAKES. THIS WILL KEEP ANY SIGNIFICANT
AWAY FROM THE REGION WITH ONLY A POTENTIAL OF MAINLY LAKE EFFECT
SNOWS DOWNWIND OF THE LAKES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 02Z...
* POTENTIAL FOR PERSISTING MVFR/IFR CIGS TONIGHT.
* LIGHT WEST-SOUTHWEST WINDS BECOMING SOUTHWEST SUNDAY AND
BECOMING GUSTY 15-20 KTS SUNDAY AFTERNOON.
RATZER
//DISCUSSION...UPDATED 02Z...
AS DISCUSSED AT 00Z...AREAS WHICH CLEARED OUT DURING THE EARLY
EVENING HAVE QUICKLY DEVELOPED FOG/PATCH LOW STRATUS ACROSS
PORTIONS OF NORTHERN IL. SATELLITE TRENDS CONTINUE TO INDICATE AN
APPROXIMATELY RFD TO ORD LINE TO BE IN AND OUT OF MVFR CLOUD COVER
THROUGH THE EVENING...WHILE AREAS SOUTH OF THAT LINE WILL LIKELY
SEE VISIBILITIES DROPPING AND AT LEAST PATCHY IFR/LIFR CIGS IN
FOG. TRAILING EDGE OF MORE SOLID CLOUD DECK ACROSS WESTERN WI
LOOKS TO GET THROUGH RFD AROUND 04Z AND THROUGH CHICAGO TERMINALS
IN 06-08Z RANGE...AFTER WHICH FOG/LOW STRATUS MAY BECOME A
PROBLEM. HAVE ISSUED AMENDMENTS TO ACCOUNT FOR CURRENT TRENDS AND
THINKING...INCLUDING POTENTIAL FOR SOME IFR/LIFR FOG/STRATUS INTO
SUNDAY MORNING.
RATZER
PREVIOIUS DISCUSSION FROM 00Z...
EXTENSIVE AREA OF MAINLY MVFR CEILINGS REMAIN OVER MUCH OF
WISCONSIN...FAR NORTHEAST ILLINOIS AND INDIANA EARLY THIS EVENING.
WHILE CLEARING HAS OCCURRED ACROSS PORTIONS OF NORTHERN ILLINOIS...
GOES IR SATELLITE IMAGERY INDICATES A SOUTHEASTWARD DRIFT OF MVFR
CLOUDS ALONG A ROUGHLY PRAIRIE DU CHIEN TO JANESVILLE TO CHICAGO
LINE WHICH SUGGESTS MVFR CONDITIONS MAY CONTINUE TO BE AN ISSUE
FOR TERMINALS THIS EVENING. MID-LEVEL TROUGH AXIS OVERHEAD WILL BE
MOVING EAST OF THE FORECAST AREA BY MID-LATE EVENING...WHICH
SHOULD OTHERWISE AID IN CLEARING WITH INCREASING DEEP SUBSIDENCE
OVERNIGHT. HOWEVER...LITTLE DRYING OCCURRING IN THE LOW LEVELS...
AND THIS COMBINED WITH LOWERING SUBSIDENCE INVERSION AND NEW SNOW
COVER MAY POSSIBLY RESULT IN DEVELOPMENT OF LOW STRATUS OVER
PORTIONS OF THE AREA THAT HAVE CLEARED OUT. MOST MODEL GUIDANCE
IS NOT REALLY HANDLING THE DETAILS OF CURRENT CLOUD TRENDS VERY
WELL...THOUGH SOME OF THE SHORT RANGE ENSEMBLE GUIDANCE INCLUDING
VSREF RUNS DO INDEED DEPICT HIGHER PROBABILITIES OF CIGS BELOW
2000 FT INCREASING IN AREA ACROSS NORTHERN IL OVERNIGHT. LOW
CONFIDENCE IN HOW THIS WILL PLAY OUT EXACTLY...SO HAVE INDICATED
AN MVFR CIG THROUGH THIS EVENING SCATTERING TO A 1000 FT LAYER
AFTER MIDNIGHT. IN LIEU OF ADDING AN IFR CIG AT THIS TIME...WILL
CONTINUE TO MONITOR SATELLITE TRENDS AND WILL REFINE WITH LATER
AMENDMENTS. ANOTHER CONCERN IS IF WE DO DEVELOP A LOW STRATUS
CEILING OVERNIGHT IS GETTING RID OF IT IN THE MORNING.
IGNORING ANY MORNING STRATUS...IF IT FORMS TONIGHT...WOULD EXPECT
SOME PATCHY VFR MID/HIGH CLOUDS ON SUNDAY AS WARM ADVECTION
INCREASES ALOFT IN ASSOCIATION IN ASSOCIATION WITH ANOTHER UPPER
DISTURBANCE ALONG THE CANADIAN BORDER. MAIN AFFECT FOR TERMINALS
WILL BE WINDS...WHICH WILL SHIFT SOUTHWEST AND BECOME SOMEWHAT
GUSTY IN THE AFTERNOON IN RESPONSE TO DEEPENING LOW PRESSURE OVER
ONTARIO. FORECAST SOUNDINGS INDICATE 15-20 KT GUST POTENTIAL IN
MIXED LAYER DURING THE AFTERNOON.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM-LOW CONFIDENCE ON CIG TRENDS TONIGHT.
* HIGH CONFIDENCE IN WIND TRENDS THROUGH PERIOD.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN...PSBLY MIXED WITH SNOW AT
ONSET TUES. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
RATZER
&&
.MARINE...
219 PM CST
A PROGRESSIVE WEATHER PATTERN ACROSS THE GREAT LAKES WILL CONTINUE
TO USHER MULTIPLE GUSTY SYSTEMS OVER THE REGION THE NEXT COUPLE OF
DAYS. THE FIRST ONE CENTERED OVER NORTHERN ONTARIO TONIGHT WILL
SWING A TROUGH THROUGH LAKE MICHIGAN THROUGH THE EVENING...TURNING
WINDS TO THE WEST...EVEN SLIGHTLY NORTHWEST IN PARTS OF THE OPEN
WATER. SOME WINDS UP TO 30 KTS ARE POSSIBLE WITH THIS
REGIME...MAINLY IN THE NORTH CLOSER TO THE SYSTEM. A STRONGER LOW
PRESSURE NORTH OF LAKE SUPERIOR WILL RACE EAST ON SUNDAY AFTERNOON
AND EVENING...SWEEPING A COLD FRONT THROUGH THE LAKE SUNDAY NIGHT
INTO EARLY MONDAY. THE TIGHT GRADIENT AROUND THIS LOW AND DEEPER
MIXING WILL SUPPORT GALES ACROSS THE LAKE BEGINNING LATE SUNDAY
AFTERNOON OVER THE NORTH AND SUNDAY EVENING OVER THE SOUTH. THE
WINDOW OF TIME FOR THE GALES WILL BE SHORT...ONLY THROUGH SUNDAY
NIGHT...DUE TO THE QUICK MOVEMENT OF THE SYSTEM. PREVAILING WAVES
UP TO 14 FT ARE EXPECTED ACROSS OPEN WATERS OF THE FAR NORTH. THE
NORTHWEST FLOW BEHIND THE FRONT WILL STILL BE BREEZY ON MONDAY
DESPITE THE WIND SPEEDS GRADUALLY DIMINISHING. HIGH PRESSURE WILL
MOVE OVER THE LAKE MONDAY NIGHT INTO THE DAY TUESDAY.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
645 PM EST SAT DEC 17 2011
.AVIATION...
SEVERAL CONCERNS FOR CIGS OVERNIGHT AT TERMINAL SITES IN LIGHT OF
LATEST SATELLITE TRENDS AND SOME LATEST HIGH RESOLUTION MODEL DATA.
SATELLITE SHOWS AREA OF MIXED VFR AND MVFR CIGS FROM INDIANA BACK
THROUGH WI WHILE SUBSIDENCE BEHIND FAST MOVING SHORT WAVE TO OUR
SOUTH HAS HELPED CLEAR SKIES ACROSS NORTHERN IL. CLEARING WORKING
EAST BUT WI CLOUDS MAKING PROGRESS SOUTHEAST. LATEST 20Z HRRR MODEL
SHOWING STRATUS DEVELOPING IN NE IL EARLY THIS EVENING WHERE WINDS
BECOMING LIGHT AND LOW LEVEL MOISTURE IS HIGH FROM SNOW TODAY. 18Z
NAM12 BUFKIT SOUNDINGS ALSO CONCERNING SHOWING DEVELOPMENT OF
SHALLOW STRATUS LATER THIS EVENING AT TAF SITES. UNCERTAINTY ABOUNDS
WITH STRATUS DEVELOPMENT GIVEN VERY SHALLOW LAYER BEING DEPICTED AND
NO SIGNS YET WHERE HRRR SHOWS DEVELOPMENT. FOR NOW PLAN TO INTRODUCE
MVFR CIGS BASED ON CURRENT SATELLITE TRENDS AND MONITOR SATELLITE
AND OBS FOR ANY SIGNS OF STRATUS DEVELOPMENT THROUGH THE EVENING.
THIS WILL RESULT IN SKIES CLEARING LATE OVERNIGHT AS DRIER AIR WORKS
IN ALOFT. ADDED SOME MVFR VIS WITH CLEARING AROUND DAYBREAK.
SOUTHWEST WINDS INCREASE SUNDAY WITH RETURN FLOW AND INCREASING
GRADIENT.
&&
.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT
DIMINISHING SNOW THIS EVENING...FOLLOWED BY MODERATING TREND FOR
SUNDAY WILL BE THE MAIN FORECAST ITEMS OF INTEREST FOR THE SHORT
TERM.
WATER VAPOR IMAGERY EARLY THIS EVENING INDICATING A COUPLE OF SHORT
WAVES TO IMPACT THE REGION. THE FIRST OF THESE SHORT WAVES WHICH
ENHANCED LIGHT SNOW ACROSS PORTIONS OF NORTH CENTRAL/NORTHWEST
INDIANA AND SOUTHERN LOWER MICHIGAN IS EXITING EAST CENTRAL INDIANA
AT THIS TIME. A MORE SHEARED IN NATURE UPSTREAM VORT ACROSS THE
UPPER MS RIVER VALLEY WILL TRACK SOUTHEAST INTO THE SOUTHERN GREAT
LAKES THIS EVENING. ASCENT WITH THIS SECONDARY SHORT WAVE IS
EXPECTED TO BE QUITE WEAK AND HAVE JUST CONTINUED CHANCE POPS INTO
THIS EVENING MAINLY ACROSS THE NORTH/NORTHEAST. AFTER 00Z...HAVE
MAINTAINED HIGHEST CHANCE POPS IN FAR SOUTHWESTERN LOWER MICHIGAN
WHERE MARGINAL DELTA TEMPS AND WESTERLY FLOW OFF LAKE MICHIGAN
SHOULD ALLOW FOR AT LEAST SCATTERED LIGHT SNOW SHOWERS TO PERSIST.
THERMODYNAMIC PROFILES SHOULD BECOME INCREASINGLY UNFAVORABLE FOR
SIGNIFICANT LAKE ENHANCEMENT AS LOW LEVEL WARM FRONT SHIFTS ACROSS
THE WESTERN GREAT LAKES LIMITING LAKE INDUCED INSTABILITY. ANY
ADDITIONAL ACCUMULATIONS ACROSS THE FAR NORTH AND NORTHEAST THIS
EVENING SHOULD BE GENERALLY LESS THAN A HALF INCH. OTHERWISE...SKIES
SHOULD CLEAR FROM WEST TO EAST LATE EVENING INTO THE OVERNIGHT AS
SYNOPTIC SUBSIDENCE INCREASES BEHIND THIS SHEARED VORT MAX. WITH
TREND TO CLEARING SKIES OVERNIGHT...DID TEND TO FAVOR COOLER MAV
GUIDANCE FOR LOWS TONIGHT.
HEIGHTS TO BUILD ACROSS THE UPPER MS RIVER VALLEY INTO THE GREAT
LAKES REGION FOR SUNDAY AS NEXT FAST MOVING SOUTHWEST CANADIAN
PACIFIC UPPER LEVEL SHORT WAVE BEGINS TO INDUCE SFC CYCLOGENESIS
ACROSS SOUTHWEST ONTARIO. GRADIENT WILL REMAIN RELATIVELY LIGHT
THROUGH MOST OF THE AFTERNOON...BUT BY LATE AFTERNOON INTO THE
EVENING LOW LEVEL FLOW/SFC WINDS WILL RAMP UP IN RESPONSE TO THIS
CYCLOGENESIS AND SFC PRESSURE FALLS TO THE NORTH. CONTINUED WARM
ADVECTION ON SUNDAY WILL RESULT IN A STRONG LOW LEVEL INVERSION AND
THUS NOT DRAMATIC SENSIBLE WARMING AT THE SURFACE...BUT WOULD
SUSPECT TEMPS COULD RISE INTO THE LOWER 40S ACROSS WESTERN PORTIONS.
LOW LEVEL THETAE RIDGE TO ADVECT INTO WESTERN PORTIONS OF THE
FORECAST AREA LATE SUNDAY NIGHT IN ADVANCE OF COLD FRONTAL BOUNDARY.
DEEPER MOISTURE PROFILES LOOK QUITE MEAGER HOWEVER AND WITH LARGE
SCALE FORCING FOR ASCENT STILL OFF TO THE WEST AND NORTH...MAY HAVE
TO CONTEND WITH SOME PATCHY DRIZZLE GIVEN SHALLOW NATURE OF
MOISTURE. WITH LOWER CONFIDENCE IN MEASURABLE PRECIP SUNDAY
NIGHT...WILL KEEP DRY. TEMPS LIKELY TO BE STEADY OR EVEN SLOWLY
RISING THROUGH THE NIGHT AHEAD OF THE COLD FRONT.
&&
.LONG TERM... / MONDAY THROUGH SATURDAY /
POTENT NORTHERN STREAM SHORTWAVE WILL TRACK SEWD THROUGH SOUTHEAST
CANADA FORCING A SFC CDFNT THROUGH OUR AREA ON MONDAY. DRIZZLE OR A
PERIOD OF LIGHT RAIN MAY ACCOMPANY THE FRONT...WITH BEST CHANCES FOR
MEASURABLE RAIN BEING ACROSS SOUTHERN AREAS. MOISTURE LOOKS VERY
SHALLOW AND LIMITED INITIALLY...ALTHOUGH DEVELOPING FAVORABLE RIGHT
ENTRANCE REGION UPPER JET DYNAMICS AND SHALLOW CONVERGENCE ALONG
BOUNDARY MAY BE ENOUGH TO WRING OUT SOME LIGHT RAIN. CONFLUENT FLOW
WILL ALLOW SFC HIGH PRESSURE TO BRIEFLY BUILD INTO THE GREAT LAKES
MONDAY NIGHT INTO TUESDAY MORNING AS THE AFOREMENTIONED FRONTAL
BOUNDARY STALLS INVOF THE OHIO RIVER. 12Z MODEL SUITE IS IN GENERAL
AGREEMENT ON THIS...WITH TRENDS SEEN IN PREVIOUS GUIDANCE. AS A
RESULT DROPPED POPS MONDAY NIGHT ACROSS THE NORTHERN TWO THIRDS OF
THE FA...RETAINING LOWER POPS IN THE SOUTH WHERE SOME RAIN MAY
LINGER.
ATTENTION WILL THEN TURN TO A CLOSED LOW STILL SPINNING NEAR FAR
SOUTHERN CALIFORNIA. 12Z ENSEMBLES AND DETERMINISTIC MODELS HAVE
TRENDED SLOWER OVERALL WITH KICKING THIS FEATURE EWD INTO THE
CENTRAL PLAINS TUESDAY...AND INTO THE NORTHERN OH VALLEY BY
WEDNESDAY. THIS APPROACHING POSITIVE PV ANOMALY WILL SUPPORT BACKING
FLOW AND INCREASING ISENTROPIC LIFT...WHICH WHEN COMBINED WITH
DIFFLUENT FLOW ALOFT WILL SUPPORT INCREASING CHANCES FOR
PRECIPITATION TUESDAY INTO WEDNESDAY LOCALLY. LACK OF ANY PHASE WITH
THE NORTHERN STREAM WILL KEEP THERMAL PROFILES ON THE WARM SIDE WITH
MAINLY RAIN ANTICIPATED. HOWEVER...CANNOT RULE OUT A BRIEF PERIOD OF
WET SNOW IN THE NORTH TUESDAY...AND THEN AGAIN ON THE BACKSIDE OF
THIS SYSTEM COME LATE WEDNESDAY AFTERNOON/EVENING. LITTLE TO NO SNOW
ACCUMULATION IS ANTICIPATED. RAINFALL WILL BE ON THE LIGHT SIDE FOR
MOST OF THE EVENT...ALTHOUGH A PERIOD OF MODERATE RAIN WILL BE
POSSIBLE WITHIN THE DEVELOPING MID LVL DEFORMATION AXIS BY LATER
TUESDAY NIGHT AND WEDNESDAY. THIS MAY CREATE SOME RENEWED RIVER
FLOODING.
12Z GUIDANCE RETAINED SOME CONTINUITY OVERALL IN TRENDING TOWARDS
MORE TYPICAL DECEMBER TEMPS BY LATE NEXT WEEK INTO SATURDAY AS A
MORE AMPLIFIED NORTHERN STREAM UPPER TROUGH DIGS INTO THE CENTRAL
AND EASTERN CONUS. ATTM...IT APPEARS AS IF THIS PERIOD WILL
FEATURE PRIMARILY DRY CONDITIONS AS POSITIVE TILT TO TROUGH SHOULD
KEEP DEEPER MOISTURE SHUNTED WELL SOUTH AND EAST OF THE REGION.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...GALE WARNING FROM 4 PM SUNDAY TO 7 AM EST MONDAY FOR LMZ043-046.
&&
$$
SHORT TERM...MARSILI
LONG TERM...STEINWEDEL
AVIATION...LASHLEY
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
314 PM CST FRI DEC 16 2011
.SYNOPSIS...
12Z UA ANALYSIS HAS A SHORTWAVE ACROSS THE DAKOTAS WITH AN 850MB
ARCTIC FRONT FROM CENTRAL MINNESOTA INTO UPPER MICHIGAN. A RIDGE
EXTENDED FROM MINNESOTA INTO WEST TEXAS. SATELLITE AND RADAR TRENDS
THROUGH MID AFTERNOON SHOW LOW CLOUDS ACROSS PARTS OF THE DAKOTAS
INTO MINNESOTA WITH MID AND HIGH CLOUDS FROM NEBRASKA INTO
WISCONSIN. SOME LIGHT SNOW WAS OCCURRING IN WESTERN MINNESOTA WHERE
THE STRONGEST WAA WAS OCCURRING.
18Z SFC ANALYSIS HAS A WEAK CLIPPER SYSTEM LOW AT KMHE WITH A WARM
FRONT INTO NORTHWEST IOWA. A COLD FRONT EXTENDED FROM THE LOW IN
CENTRAL AND WESTERN NEBRASKA WHILE A TROF RAN FROM THE LOW INTO
SOUTHEAST COLORADO. DEW POINTS WERE IN THE TEENS AND 20S ACROSS MUCH
OF THE MIDWEST WITH 30 AND HIGHER DEW POINTS FROM THE SOUTHERN
PLAINS INTO THE DEEP SOUTH.
&&
.SHORT TERM...TONIGHT AND SATURDAY...
A WEAK CLIPPER SYSTEM WILL MOVE ACROSS THE AREA TONIGHT AND VERY
EARLY SATURDAY. THIS SYSTEM WILL BRING SOME SNOW TO ROUGHLY THE
NORTHERN QUARTER OF THE CWFA.
BASED ON THE OVERALL FORCING AND CONDENSATION PRESSURE DEFICITS THIS
SNOW EVENT WILL ONLY LAST ABOUT 6 TO POSSIBLY 8 HOURS ONCE IT BEGINS.
NOW...ALL MODELS INITIALIZED TOO MOIST WITH MOISTURE IN THE NORTHERN
PLAINS THIS MORNING. THAT COMBINED WITH THE VERY DRY ATMOSPHERE OVER
THE AREA WILL RESULT IN LOWER SNOW AMOUNTS. THE RUC HAS BEEN VERY
USEFUL SO FAR TODAY DEPICTING WHAT HAS BEEN HAPPENING ON THE 280K
CONDENSATION PRESSURE DEFICIT LAYER WHEN COMBINED WITH
FRONTOGENETICAL FORCING AND F VECTOR CONVERGENCE.
USING THE RUC AS A TREND...THE EARLY EVENING HOURS SHOULD REMAIN
DRY. BETWEEN 03Z AND 06Z FLURRIES OR POSSIBLY SOME VERY LIGHT SNOW
SHOULD MOVE IN OR DEVELOP NORTH OF A KVTI TO KSQI LINE. THE MOST
FAVORED AREA WOULD BE RIGHT ALONG AND NORTH OF HWY 20. HOWEVER...
FCST SOUNDINGS FROM THE RUC AT KDBQ STILL SHOW CONSIDERABLE AMOUNTS
OF DRY AIR BELOW 800MB SO PRECIPITATION CHANCES ARE STILL IN
QUESTION PRIOR TO MIDNIGHT.
AFTER MIDNIGHT THE MAIN VORT MAX MOVES THROUGH THE AREA. FROM JUST
BEFORE MIDNIGHT TO ROUGHLY 10Z WILL BE THE MOST LIKELY TIME FOR SNOW
TO OCCUR. AREAS NORTH OF A KALO TO KRPJ LINE SHOULD SEE -SN WITH
AREAS NORTH OF A KIIB TO KDKB LINE...OR EAST OF MANCHESTER ON THE
HIGHWAY 20 CORRIDOR...HAVING THE BEST CHANCE AT ANY ACCUMULATION.
AMOUNTS WILL BE LIGHT AND SHOULD BE NO MORE THAN 0.5 INCHES. AREAS
IMMEDIATELY NORTH OF THE CWFA MAY SEE AMOUNTS APPROACHING AN INCH.
SATURDAY...SOME LINGERING FLURRIES MAY OCCUR THROUGH SUNRISE IN THE
FAR NORTHEAST PART OF THE CWFA. OTHERWISE...DRY CONDITIONS WITH A
DECREASE IN CLOUDS SHOULD BE SEEN THROUGH THE DAY. TEMPERATURES
SHOULD BE AROUND OR A LITTLE ABOVE NORMAL.
..08..
.LONG TERM...SATURDAY NIGHT THROUGH NEXT FRIDAY...
SATURDAY NIGHT THROUGH MONDAY...OUR CWA WILL SPEND ANOTHER FEW DAYS
WELL ABOVE NORMAL...WITH TEMPERATURES MUCH MORE REPRESENTATIVE OF
LATE FALL VS MID DECEMBER. HIGHS SUNDAY AND MONDAY IN THE LOWER TO
UPPER 40S LOOK TO BE A STRONG BET...WHILE OVERNIGHT LIGHTS SATURDAY
NIGHT ONLY DIPS TO THE MID 20S AND SUNDAY NIGHT MAY HOLD IN THE
UPPER 30S TO LOWER 40S PENDING CLOUD COVER. WE WILL GO WITH LOWER TO
MID 30S BANKING ON SOME POTENTIAL CLEAR SKIES FOR NOW.
AFTER THE QUIET MILD WEATHER...OUR ATTENTION TURNS TO THE FORECAST
PROBLEMATIC STORM SYSTEM FOR MONDAY AND TUESDAY. MODELS ARE SHIFTING
THIS LOW FARTHER NORTH AGAIN. THIS IS NOT DUE TO SOME SORT OF
CONVECTIVE FEEDBACK OR ANYTHING...BUT RATHER THE INITIALIZATION OF A
STRONG SHORT WAVE OVER THE CENTRAL PACIFIC OCEAN. THE LATITUDE OF
THIS SHORT WAVE AS SEEN ON WATER VAPOR IMAGERY...IS ABOUT 30 TO 35
NORTH...LONGITUDE 155 WEST. THIS PLACEMENT IS A BIT SOUTH OF GLOBAL
MODELS AS OF 18Z. THE IMPACT WILL BE HUGE ON WHETHER THEY HANDLE
THIS WAVE CORRECTLY. OVER TOPPING THE WESTERN RIDGE WOULD RESULT IN
A SOUTHERN LOW TRACK...AND LITTLE OR NO QPF FROM THE STORM MONDAY
AND TUESDAY. A PHASED TRACK IS LIKELY IF THE LOW MAKES A ENTRY INTO
THE CANADIAN AND CONUS NEAR OR SOUTH OF 50 NORTH. THIS COULD BRING
THE SURFACE LOW AS FAR NORTH AS OVERHEAD...PRODUCING A SIGNIFICANT
RAIN EVENT. OUR POPS ARE IN THE CHANCE RANGE FOR MONDAY THROUGH
TUESDAY...WITH THE HIGHEST SOUTH. A TRANSITION FROM RAIN TO SNOW IS
FORECAST FOR MONDAY EVENING NORTH...TO TUESDAY MORNING SOUTH. WHILE
ACCUMULATION ARE POSSIBLE...THE COLD AIR IS LACKING TO THE STORM IN
A PHASED LOW FORECAST. THUS...WE WILL REMAIN VERY VAGUE ON
ACCUMULATION POTENTIAL AT THIS TIME ON PURPOSE.
WEDNESDAY THROUGH FRIDAY REMAINS NEAR OUR BLENDED MODEL FORECAST.
OVER ALL...ANOTHER LARGE TROUGH SHOULD APPROACH THE MIDWEST
THURSDAY...RESULTING IN A CHANCE FOR SNOW...AND POSSIBLY RAIN SNOW
MIX.
..ERVIN..
&&
.AVIATION...
VFR WX IS EXPECTED THROUGH 06Z/17. A CLIPPER TYPE STORM SYSTEM WILL
MOVE THROUGH THE WESTERN GREAT LAKES AFT 06Z/17. KCID/KMLI/KBRL ARE
EXPECTED TO REMAIN VFR THROUGH 00Z/18. KDBQ SHOULD REMAIN VFR WITH
-SN. THERE IS A POSSIBILITY OF A BRIEF PERIOD OF 3-5SM AND 3KFT AGL
CIGS AT KDBQ IN THE 04Z-09Z/17 TIME FRAME.
..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1147 AM CST FRI DEC 16 2011
.AVIATION...
VFR WX WILL BE SEEN THROUGH 03Z/17. AFT 03Z/17 A CLIPPER TYPE
STORM SYSTEM WILL MOVE INTO THE AREA. KCID/KMLI/KBRL SHOULD
CONTINUE TO SEE VFR CONDITIONS. KDBQ IS EXPECTED TO REMAIN VFR
WITH -SN. THE SNOW AT KDBQ IS ONLY EXPECTED TO LAST ABOUT 6 HRS.
ALTHOUGH LOW...THERE IS A POSSIBILITY OF A BRIEF 3-5SM -SN AND
CIGS ARND 3KFT AGL AT KDBQ IN THE 04Z-10Z/17 TIME FRAME.
..08..
&&
.PREV DISCUSSION... /ISSUED 1028 AM CST FRI DEC 16 2011/
UPDATE...
AN UPDATE TO THE OVERALL FORECAST FOR TODAY WILL BE AVAILABLE SHORTLY.
BASED ON DATA THROUGH 15Z...MAX TEMPERATURES LOOK A LITTLE TOO
WARM FOR TODAY AND WERE LOWERED A FEW DEGREES. RUC TRENDS
INDICATE THE RETURN WAA DOES NOT DEVELOP UNTIL CLOSE TO MID
AFTERNOON IN THE WESTERN CWFA WHICH IS RIGHT AROUND MAX HEATING
FOR THIS TIME OF YEAR.
AS FOR TONIGHT...FURTHER EVALUATION IS NEEDED REGARDING
PRECIPITATION CHANCES. HOWEVER...CURRENT DATA IS PLACING SOME
DOUBT ON THE CHANCE FOR SNOW.
.08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1028 AM CST FRI DEC 16 2011
.UPDATE...
AN UPDATE TO THE OVERALL FORECAST FOR TODAY WILL BE AVAILABLE SHORTLY.
BASED ON DATA THROUGH 15Z...MAX TEMPERATURES LOOK A LITTLE TOO
WARM FOR TODAY AND WERE LOWERED A FEW DEGREES. RUC TRENDS
INDICATE THE RETURN WAA DOES NOT DEVELOP UNTIL CLOSE TO MID
AFTERNOON IN THE WESTERN CWFA WHICH IS RIGHT AROUND MAX HEATING
FOR THIS TIME OF YEAR.
AS FOR TONIGHT...FURTHER EVALUATION IS NEEDED REGARDING
PRECIPITATION CHANCES. HOWEVER...CURRENT DATA IS PLACING SOME
DOUBT ON THE CHANCE FOR SNOW.
..08..
&&
.PREV DISCUSSION... /ISSUED 544 AM CST FRI DEC 16 2011/
AVIATION... /ISSUED 324 AM CST FRI DEC 16 2011/
HIGH PRESSURE WILL REMAIN OVER THE MIDWEST TODAY...RESULTING IN VFR
CONDITIONS AND LIGHT WINDS. AFTER 06Z TONIGHT...A WEAK WAVE WILL
BRING MVFR CLOUDS TO AREAS MAINLY ALONG AND NORTH OF I80 WITH A
CHANCE FOR LIGHT SNOW ACCUMULATIONS AND MVFR VISIBILITY
REDUCTIONS. THE LOWER ATMOSPHERE IS EXTREMELY DRY...AND THERE IS
SIGNIFICANT UNCERTAINTY IN WHETHER IT WILL BE ABLE TO SATURATE
ENOUGH TO ALLOW ANY SNOW TO CAUSE VISIBILITY REDUCTIONS. ..DMD..
PREV DISCUSSION... /ISSUED 324 AM CST FRI DEC 16 2011/
SYNOPSIS...
SPLIT FLOW DOMINATES THE LONG WAVE PATTERN...WITH A CUT OFF LOW OVER
THE BAJA PENINSULA WHILE THE NORTHERN STREAM PROVIDES AN ACTIVE
NORTHWEST FLOW PATTERN FOR THE UPPER MIDWEST. WATER VAPOR LOOP
SHOWS A SHORT WAVE LIFTING ACROSS OKLAHOMA IN THE SOUTHERN STREAM
AND ANOTHER DROPPING INTO EASTERN MONTANA IN THE NORTHERN STREAM. AT
THE SURFACE...AREA TEMPERATURES HAVE FALLEN INTO THE 20S WITH DEW
POINTS ANYWHERE FROM THE MID TEENS TO MID 20S. COLD ADVECTION
CONTINUES WITH TEMPS IN THE TEENS AND DEW POINTS IN THE LOWER TO MID
TEENS UPSTREAM IN NORTH CENTRAL IOWA. ..DMD..
SHORT TERM...TODAY AND TONIGHT...
MAIN FOCUS THIS MORNING IS ON POTENTIAL FOR LIGHT SNOW WITH TONIGHTS
SHORT WAVE. SATELLITE TRENDS SUGGEST MORE ORGANIZATION TO THE WAVE
THAN THE MODELS WOULD PERHAPS INITIALLY IMPLY. 00Z GFS AND ECMWF
RUNS BOTH INDICATE ENOUGH FORCING TO SUPPORT LOW POPS OVER EXTREME
NORTHEAST IOWA INTO SOUTHERN WISCONSIN AND NORTHERN ILLINOIS. THE
00Z AND 06Z NAM RUNS ALSO PICK UP ON THE FRONTOGENETICAL FORCING BUT
ARE LESS OPTIMISTIC ABOUT MOISTURE. TIME-HEIGHT CROSS SECTIONS OF
ALL MODELS IN FACT SHOW THAT THE LIFT AND FORCING MAY BE EXITING THE
AREA BEFORE THE LOWER ATMOSPHERE HAS MUCH OPPORTUNITY TO SATURATE.
END RESULT IS THAT ONLY AREAS CLOSER TO MAXIMUM LIFT...THAT IS NEAR
THE TRI-STATE REGION NORTH OF THE QUAD CITIES...THERE IS A CHANCE FOR
A LIGHT ACCUMULATION. HOWEVER...DIFFICULTY IN OVERCOMING THE DRY
BOUNDARY LAYER AND SHORT DURATION OF FORCING WILL LIMIT AMOUNTS.
HAVE INTRODUCED LOW POPS FOR TONIGHT FOR THIS SCENARIO. ..DMD..
LONG TERM...SATURDAY THROUGH THURSDAY...
THE PERIOD WILL GET OFF TO A QUIET START...UNDER THE INFLUENCE OF
DRY BUT MILD FLATTENING NORTHWEST FLOW. FOR EARLY NEXT WEEK
THOUGH...UNCERTAINTY STILL REIGNS CONCERNING THE POTENTIAL FOR
RAIN AND/OR SNOW EVENT OVER THE AREA WITH MODELS STILL GIVING
DIFFERING SOLUTIONS ON THE INTERACTION OF THE EJECTING
SOUTHWESTERN U.S. CUTOFF LOW AND A NORTHERN STREAM S/W. FOR
MID/LATE WEEK THERE IS A CONCENSUS AMONG THE GFS/ECMWF THAT THE
WESTERN U.S. TROF WILL REDEVELOP.
FOR SATURDAY AND SUNDAY NIGHT...THE REGION WILL BE EMBEDDED IN NORTHWEST
FLOW BETWEEN A WESTERN U.S. RIDGE AND AN OHIO VALLEY/GREAT LAKES
TROF. A S/W TRACKING THROUGH THE WESTERN GREAT LAKES SHOULD BE FAR
ENOUGH EAST TO KEEP ANY SNOW WELL EAST OF THE CWFA SATURDAY
AFTERNOON AND EVENING. TEMPERATURES SHOULD REMAIN NEAR TO ABOVE
NORMAL FOR THE WEEKEND. SOME SUN ON SATURDAY SHOULD HELP BOOST
READINGS IN THE MID 30S TO AROUND 40. FOR SUNDAY NIGHT
TEMPERATURES SHOULD BE ABLE TO RADIATE OUT WITH A SURFACE RIDGE
MOVING THROUGH THE AREA...SO SKEWED LOWS TOWARD THE COLDER
GUIDANCE. WITH THE RIDGE EAST OF THE AREA SUNDAY...RETURN FLOW
SETS UP SO TEMPS ARE EXPECTED TO RECOVER INTO THE LOW TO MID 40S.
INCREASING SOUTHWEST FLOW AHEAD OF COLD FRONT DROPPING INTO
NORTHWEST IOWA SUNDAY NIGHT...AS WELL INCREASING SURFACE DEW POINTS
AND CLOUDS WILL KEEP TEMPERATURES FROM FALLING MUCH BY MONDAY
MORNING...SO KEPT MINS IN THE LOW TO MID 30S.
FOR MONDAY THROUGH TUESDAY NIGHT THE MODELS ARE STILL OFFERING
DIFFERENT SOLUTIONS CONCERNING THE EJECTING SOUTHWEST LOW AND HOW
IT IS INFLUENCED BY A NORTHERN STREAM S/W. THE 00Z GFS IS STILL
LOCKED INTO THE MORE NORTHERN SOLUTION WITH THE EJECTING UPPER
LOW...WHICH GIVES THE AREA ANOTHER MODERATE PRECIPITATION EVENT.
THE 12Z AND 00Z ECMWF ARE STILL HOLDING ON TO A MORE SOUTHERN
TRACK OF THE UPPER LOW...WHICH KEEPS A LEAST THE NORTHER HALF OF
THE AREA DRY. THE ONLY CHANGES TO THE PREVIOUS FORECAST THEN
CONCERNING POPS AND THE DIFFERING SOLUTIONS WAS TO INCREASE POPS
TO HIGH CHANCE IN THE SOUTH WITH THE LATEST ECMWF MOVING THE
NORTHERN EDGE OF IT/S PRECIPITATION SHIELD A LITTLE FURTHER NORTH
TUESDAY AND LOWERING POPS TO SLIGHT CHANCE MONDAY AND MONDAY NIGHT
IN THE NORTH WITH THE GFS MOVING ITS NORTHERN EDGE A LITTLE MORE
SOUTH THAN THE PREVIOUS RUNS. PRECIPITATION TYPE IS STILL HARD TO
PIN DOWN WITH THE DIFFERING SOLUTIONS SO MAINTAINED THE RAIN OR
RAIN/SNOW WORDING AS THE SYSTEM APPROACHES MONDAY THEN SNOW
SPREADING SOUTHEAST MONDAY NIGHT AND TUESDAY WITH SYSTEM PULLING
AWAY FROM THE REGION.
BOTH THE GFS/ECMWF SHOW ANOTHER UPPER TROF DEVELOPING OVER THE
WESTERN U.S. BY THE END OF THE WEEK. EXPECT DRY WEATHER DURING THE
TRANSITION WITH INCREASING SOUTHWESTERLY FLOW SUPPORTING ABOVE
NORMAL TEMPERATURES. ..DLF..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1152 PM CST THU DEC 15 2011
.AVIATION...
CLEAR VFR CONDITIONS HAVE RETURNED TO THE AREA ALONG WITH MUCH
COLDER AND DRIER AIR MOVING IN ON THE HEELS OF LAST NIGHTS COLD
FRONT. A WEAK SHORTWAVE TO MOVE FROM MINNESOTA TO NORTHERN
ILLINOIS FRIDAY NIGHT WHICH SHOULD BRING VFR CLOUDS TO THE
TERMINALS. FLURRIES MAY BE POSSIBLE AT KDBQ OR KMLI. ..LE..
&&
.PREV DISCUSSION... /ISSUED 244 PM CST THU DEC 15 2011/
SYNOPSIS...
12Z UA ANALYSIS HAS A LLJ RUNNING FROM OKLAHOMA INTO NEW ENGLAND.
SEVERAL TROFS RAN FROM THE WESTERN GREAT LAKES INTO THE NORTHERN
PLAINS WHERE ANOTHER LLJ WAS LOCATED. SATELLITE TRENDS THROUGH EARLY
AFTERNOON SHOW THE CLOUDS BEGINNING TO BREAK UP AS STRONG SUBSIDENCE
DEVELOPS ACROSS THE PLAINS AND UPPER MISSISSIPPI VALLEY.
18Z SFC ANALYSIS HAS THE COLD FRONT FROM LAKE HURON INTO EASTERN
TEXAS WITH HIGH PRESSURE IN THE PLAINS. SEVERAL TROFS RAN FROM THE
WESTERN LAKES INTO THE UPPER MISSISSIPPI VALLEY. DEW POINTS AHEAD OF
THE FRONT WERE IN THE 50S AND 60S WITH 30S AND 40S IMMEDIATELY
BEHIND THE FRONT. DEW POINTS IN THE TEENS AND 20S WERE IN THE PLAINS
AND PARTS OF THE MIDWEST.
SHORT TERM...TONIGHT AND FRIDAY...
QUIET WX WITH SEASONABLE TEMPERATURES WILL BE SEEN TONIGHT AND
FRIDAY. WINDS WILL CONTINUE TO DECREASE LATE THIS AFTERNOON AND
EVENING AS THE STRONGEST ISALLOBARIC CHANGE CONTINUES TO MOVE EAST
OF THE AREA. RUC TRENDS INDICATE THAT STRONG SUBSIDENCE IS
DEVELOPING BEHIND THE DEPARTING SHORTWAVE AND SATELLITE DOES SHOW
MORE BREAKS BEGINNING TO DEVELOP IN THE CLOUD SHIELD.
BASED ON CURRENT SATELLITE AND RUC TRENDS...CLOUDS WILL CONTINUE TO
SLOWLY BREAK UP FOR THE REMAINDER OF THE AFTERNOON WITH CLEARING
DEVELOPING ACROSS THE CWFA LATE THIS AFTERNOON OR EVENING.
08..
LONG TERM...FRIDAY NIGHT THROUGH NEXT THURSDAY...
A WEAK CLIPPER SHOULD SLIDE SOUTHEAST FRIDAY EVENING...BRINGING SOME
MID CLOUDS TO THE CWA...AND AN OUTSIDE CHANCE FOR A SNOW
SHOWER...BUT MORE LIKELY FLURRIES IN THE NORTH. THIS VERY MINOR
EVENT PASSES QUICKLY FRIDAY NIGHT AND LEAVES SATURDAY AND SUNDAY
WITH VERY PLEASANT LATE FALL WEATHER. HIGHS IN THE MID TO UPPER 30S
SATURDAY AND LOWER TO MID 40S SUNDAY. THIS ENDS THE PERIOD OF HIGH
CONFIDENCE IN THE EXTENDED.
THE MODELS ARE IN TWO CAMPS NOW WITH RESPECT TO THE MONDAY THROUGH
WEDNESDAY STORM. THE GEM...UKMET...AND GFS RUNS SINCE 00Z LAST NIGHT
HAVE GONE FARTHER NORTH...AND BRING A SIMILAR STORM TO THE MIDWEST
THAN WAS SEEN IN THE PAST 2 DAYS. HOWEVER...THE ECMWF HAS TRENDED
SOUTH...AND CLIPS THE CWA WITH LIGHT SNOW ON TUESDAY/TUESDAY NIGHT.
THE MAJOR DIFFERENCE BETWEEN THESE MODELS BOILS DOWN TO HOW THEY
HANDLE A SEPARATE SHORT WAVE THAT ENTERS THE PACIFIC NORTHWEST
SATURDAY. THE GEM/UK/GFS ALL BRING THAT STORM INTO THE WA/OR
COAST...AND PHASE THAT WAVE/KICK THE CLOSED LOW NORTHEASTWARD AND
THEREFORE DEVELOP A SIGNIFICANT MIDWEST STORM. THE ECMWF BRINGS THIS
WAVE INTO CENTRAL BRITISH COLUMBIA...AND AS IT MOVES IT EAST...IT
OVER TOPS THE RIDGE ON THE WEST COAST VS KICKING THE LOW OUT WITH
IT. AFTER OVERTOPPING...IT SWEEPS HIGH PRESSURE AND COLD AIR DOWN
INTO THE MIDWEST FOR EARLY WEEK AND THEREFORE SUPPRESSES THE STORM
SYSTEM SOUTH. SUCH A SMALL DIFFERENCE...RESULTS IN A MAJOR
DIFFERENCES IN OUR WEATHER. THIS WAVE IN QUESTION IS REAL...BUT
FOUND OVER THE NORTH CENTRAL PACIFIC OCEAN AS OF NOW...AND IS WITHIN
A FAST BAND OF WESTERLY FLOW SOUTH OF A MAJOR ALEUTIAN LOW.
THUS...GLOBAL MODELS WILL NO LIKELY LOCK CORRECTLY ONTO ITS POSITION
AND STRENGTH FOR SOME DAYS. PREDICTING THE WEATHER IS A
CHALLENGE...BUT THIS ONE WILL TAKE TIME TO BE WORKED OUT. UNTIL WE
KNOW FOR SURE WHAT LATITUDE THIS WAVE MAKES LANDFALL IN THE PAC
NORTHWEST...WE WILL NO KNOW WHETHER IT OVERTOPS OR PHASES/KICKS OUT
OUR CLOSED LOW IN THE SOUTHWEST. TIME WILL CERTAINLY TELL.
OUR FORECAST REMAINS WET TO START...AND SNOWY TO END THIS
STORM...POPS ARE LOW...BUT SHOULD THE NORTHERN TRACK BY CORRECT...WE
NEED MUCH HIGHER POPS FOR THIS EVENT.
WEDNESDAY AND THURSDAY...ALL GLOBAL MODELS SHOW THE PATTERN
RELOADING FOR ANOTHER CUT OFF LOW IN THE SOUTHWEST. THIS SHOULD
PROVIDE ANOTHER DAY OR TWO OF QUIET WEATHER BEFORE ANOTHER POTENTIAL
EVENT.
ERVIN..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
227 PM MST FRI DEC 16 2011
.DISCUSSION...
227 PM MST FRI DEC 16 2011
MAIN FORECAST PROBLEM WILL BE STORM FOR THE BEGINNING OF NEXT WEEK
WITH SECONDARY PROBLEMS OF HOW MUCH TO WARM IT UP BEFORE THIS NEXT
UPPER LOW FOLLOWED BY WHAT KIND OF WEATHER THE NEXT COMPLICATED UPPER
TROUGH/S WILL BRING TO THE AREA THE END OF NEXT WEEK. SATELLITE
SHOWING AN AMPLIFIED/AMPLIFYING PATTERN FROM THE PACIFIC INTO NORTH
AMERICA. DUE TO DEEPENING TROUGH OVER THE WESTERN PACIFIC...SOUTHERN
END OF EASTERN PACIFIC TROUGH IS DEEPENING AND CAUSING THE WESTERN
RIDGE TO BUILD. THIS AND HEIGHT FALL ANALYSIS SHOWS UPPER LOW OVER
BAJA SINKING SOUTH AND WEST. THIS IS PART OF SPLIT FLOW/MEAN TROUGH
THAT EXISTS OVER MOST OF THE REST OF THE COUNTRY.
IN REGARDS TO THE JET OVER THE NORTHEAST PACIFIC AND ROUNDING OVER
THE TOP OF THE RIDGE...THE MODELS LOOK UNDERDONE ON SPEEDS. ON THE
SEGMENT THAT EXTENDS FROM MONTANA TO THE NORTHWEST OF THE UPPER LOW
THE MODELS TENDED TO BE SLIGHTLY UNDERDONE AND TOO FAR EAST AND
SOUTH WITH THE SEGMENT. THE NAM WAS DOING THE BEST FOLLOWED BY THE
UKMET AND THE CANADIAN. SAME THING AT MID LEVELS WITH THE NAM DOING
SLIGHTLY BETTER THAN THE CANADIAN AND UKMET. AT THE SURFACE...THE
ECMWF WAS DOING SLIGHTLY BETTER THAN THE NAM. ON THE LOW LEVEL
THERMAL FIELD THE NAM AND GFS WERE DOING SLIGHTLY BETTER THAN THE
REMAINING OUTPUT.
TONIGHT...CURRENT SURFACE OBSERVATIONS SHOW A SURFACE TROUGH MOVING
EAST ACROSS THE TRI-STATE AREA. WINDS HAVE REMAINED LIGHT TO
BREEZY...BUT A FEW GUSTS HAVE APPROACHED 25 MPH AHEAD AND BEHIND THE
TROUGH. RUC UPPER AIR ANALYSIS SHOWS AN UPPER LEVEL TROUGH
FOLLOWING THE SURFACE FEATURE...AND SATELLITE IMAGERY CONTINUES TO
SHOW A FEW MID AND HIGH CLOUDS ON EITHER SIDE OF THE UPPER LEVEL
TROUGH. FURTHER WEST THE CLOSED LOW REMAINS POSITIONED OVER THE
BAJA PENINSULA AND HAS BEEN SLOWLY RETROGRADING TO THE WEST THROUGH
THE DAY.
NORTHWEST WINDS WILL GRADUALLY TURN TO THE WEST DURING THE EVENING...
AS A SURFACE RIDGE OF HIGH PRESSURE MOVES ACROSS THE TRI-STATE AREA
BEHIND THE SURFACE TROUGH. RELATIVE HUMIDITY VALUES WILL BE NEAR 100
PERCENT OVER THE SNOW FIELD FOR THE MCCOOK AND OBERLIN AREA. HOWEVER
THE LIGHT WEST WINDS AND DRY AIR ABOVE THE SURFACE WOULD SUPPORT NO
FOG FORMING. OTHERWISE LOWS WILL BE SIMILAR TO LAST NIGHT.
SATURDAY/SATURDAY NIGHT...AREA REMAINS UNDER SUBSIDENCE AND
INFLUENCE FROM THE MID/UPPER RIDGE. WILL BE DOWNSLOPE WINDS BUT
MOSTLY LIGHT. DID WARM UP TEMPERATURES BUT POTENTIAL IS THERE TO BE
WARMER THAN WHAT I HAVE. DURING THE NIGHT DOWNSLOPE WINDS ARE IN
PLACE AND CLOUDS DO INCREASE A LITTLE.
SUNDAY...MAIN JET IS STILL FAR AWAY FROM THE AREA. DUE TO THE UPPER
LOW STILL BEING VERY FAR AWAY...MID LEVEL RIDGING AND DRYING WILL
BE IN PLACE. BY THIS TIME...WHATEVER SNOW IS HERE NOW SHOULD NOT BE
A FACTOR IN MAXES. MODELS DIFFER ON THE AMOUNT OF WARMUP WITH THE
ECMWF SHOWING THE MOST. THERE IS WEAK DOWNSLOPING OF THE WINDS WITH
THE MODELS SHOWING LITTLE IF ANY MIXING. ALSO BECAUSE OF THE
MID/UPPER LEVEL RIDGING IN PLACE...IT LOOKS LIKE THERE WILL BE A LOT
OF SUNSHINE. SO IT LOOKS LIKE MODELS ARE UNDERDOING THE WARMING AT
THIS TIME. RAISED MAXES BUT TEMPERED IT SOMEWHAT BASED ON
COLLABORATION AND THRESHOLDS. HOWEVER...THE POTENTIAL FOR BEING
MUCH WARMER THAN WHAT IS CURRENTLY IN THERE IS PRETTY HIGH. IF THE
MIXING GETS CLOSER TO 700 MB...TEMPERATURES COULD SORE INTO THE 60S
BUT I DEFINITELY DID NOT GO THAT FAR.
SUNDAY NIGHT/MONDAY...WEAKER LEFT FRONT QUADRANT OF THE SOUTHERN JET
LOOKS TO START AFFECT THE SOUTHEAST PORTION OF THE AREA LATE IN THE
NIGHT. OF NOTE HIGHER JET SPEEDS ARE STILL BEHIND INCOMING SYSTEM
AS OF 12Z MONDAY. MOST OF THE DETERMINISTIC AND ENSEMBLE DATA SHOW
THE NEXT SYSTEM COMING FURTHER SOUTH AND SLOWER WITH STILL SOMEWHAT
OF A SPREAD. THE NAM AND GEFS MEAN ARE THE FASTEST AND FURTHEST
NORTH WITH THE CANADIAN AND ECMWF FURTHEST SOUTH. IT IS STARTING TO
LOOK LIKE FURTHER SOUTH IS APPEARING MORE LIKELY. THAT SAID WITH
LITTLE IF ANY LIFT AND SOUNDINGS SHOWING AIR MASS STILL DRY...THE
DRY FORECAST FOR SUNDAY NIGHT STILL LOOKS GOOD.
LEFT FRONT QUADRANT OF THE JET AFFECTS MAINLY SOUTHEAST HALF OF THE
AREA EARLY IN THE DAY. MOST OF THE FORCING STILL LOOKS TO BE OVER
TH SOUTHERN PORTION OF THE AREA. IF NAM/GEFS RIGHT...PRECIPITATION
CHANCE WILL BE GREATER. IF ECMWF AND ESPECIALLY THE CANADIAN IS
RIGHT...PRECIPITATION WILL BE LOWER. SINCE THERE IS STILL A LOT OF
MODEL SPREAD AND CURRENT MODEL DATA SUPPORTS THE ONGOING FORECAST...
DID NOT CHANGE MONDAYS PRECIPITATION FORECAST. IT WILL DEFINITELY
WILL BE WINDY AND COLDER ON MONDAY. IF CURRENT TRENDS CONTINUE IT IS
POSSIBLE THAT MAXES WILL NEED TO BE LOWERED MORE.
MONDAY NIGHT THROUGH FRIDAY...SPREAD ON THE DETERMINISTIC AND
ENSEMBLE OUTPUT EARLY ON THROUGH TUESDAY IS PRETTY LARGE. THINKING
THAT THE SYSTEM IS LOOKING TO BE FURTHER SOUTH...PRECIPITATION
SHOULD BE DONE OR MOSTLY DONE BY 12Z TUESDAY. MODERATION OF
TEMPERATURES THEN OCCUR AS THE WESTERN TROUGH RELOADS AND MODELS TRY
TO DECIDE WHAT TO DO WITH THE NEXT SYSTEM. SPREAD IN DETERMINISTIC
AND ENSEMBLE OUTPUT CONTINUES WITH THIS NEXT SET OF STORM SYSTEMS AS
WELL.
ON THURSDAY ALL THE MODELS DO BRING A MID LEVEL TROUGH THROUGH
BUT DIFFER ON THE STRENGTH AND SPEED. IF ECMWF WERE TO VERIFY THEN
PRECIPITATION MAY NEED TO BE EXPANDED FROM WHERE IT IS AT NOW. MODELS
SHOW A FRONT MOVE THROUGH LATE WEDNESDAY NIGHT INTO THURSDAY BUT
DIFFER ON TIME. DUE TO ITS HANDLING OF THE SYSTEM AT MID LEVELS...
THE ECMWF IS MORE AGGRESSIVE WITH THE COOLING...AND LOOKS LIKE IT
IS THE BEST SOLUTION...TEMPERATURES WILL BE COOLED MORE FROM THEY
ARE AT NOW. FRIDAY LOOKS DRY AT THIS TIME BUT WITH MODEL SPREAD
THAT COULD CHANGE. COLDER WORKS ITS WAY INTO THE AREA...COLD MAXES
IN GRIDS LOOK GOOD.
THANKS TO ALL THAT COLLABORATED.
BULLER
&&
.AVIATION...
1020 AM MST FRI DEC 16 2011
VFR CONDITIONS CAN BE EXPECTED FOR THE 12Z TAFS. CURRENT SURFACE
OBSERVATIONS SHOW A SURFACE TROUGH MOVING ACROSS NEBRASKA AND
NORTHWEST KANSAS. UPPER AIR ANALYSIS SHOWS AN UPPER LEVEL TROUGH
FOLLOWING THE SURFACE FEATURE. AS THE TROUGH MOVES THROUGH THE WINDS
HAVE QUICKLY SHIFTED FROM THE WEST TO THE NORTH OR NORTHWEST. WITH
LITTLE MOISTURE TO WORK WITH...A FEW MID AND HIGH CLOUDS CAN BE
EXPECTED AS THE TROUGH MOVES THROUGH. DURING THE EVENING HOURS
WINDS WILL TURN BACK TO THE WEST AS A SURFACE RIDGE OF HIGH
PRESSURE BUILDS INTO WESTERN KANSAS. OVERNIGHT TEMPERATURES WILL
APPROACH THE DEW POINT. AM NOT CONFIDENT ENOUGH FOG WILL FORM TO
PLACE IT IN THE TAFS AS TEMPERATURE AND DEW POINT LOOK TO DROP IN
UNISON DURING THE NIGHT.
JTL
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
NE...NONE.
CO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1028 AM MST FRI DEC 16 2011
.SHORT TERM (TODAY-SUNDAY)...
233 AM MST FRI DEC 16 2011
EARLY MORNING WV IMAGERY AND RUC H5 ANALYSIS SHOW SPLIT-FLOW PATTERN
ACROSS THE EASTERN CONUS...WITH CUTOFF LOW OVER THE BAJA PENINSULA.
CWA CURRENTLY BETWEEN SHORTWAVE TROUGHS...WITH LARGE SCALE
SUBSIDENCE CURRENTLY IN PLACE.
EARLY THIS MORNING...FOG CHANCES HAVE DIMINISHED ACROSS EASTERN
COLORADO. 06Z NAM WOULD KEEP AND FOG/STRATUS SW OF CWA. LATEST RUC
DOESNT BRING BL RH VALUES ABOVE 75% ANYWHERE IN EASTERN COLORADO. I
COULDNT COMPLETELY RULE OUT ISOLATED POCKETS OF FOG NEAR SUNRISE IN
NEAR EXTREME SW PART OF CWA...BUT CONFIDENCE IS TOO LOW TO KEEP
MENTION IN FORECAST FOR NOW.
TODAY-SUNDAY NIGHT...SHORTWAVE TROUGH CURRENTLY OVER SE WYOMING WILL
SWING ACROSS THE CWA TODAY. WITH DEEP DRY LAYER IN PLACE...WILL
ONLY SEE PERIOD OF MID-HIGH CLOUDS. SHORTWAVE RIDGE BUILDS OVER CWA
SAT AND SUNDAY...WITH WARM AND DRY CONDITIONS EXPECTED. HIGHS IN LOW
50S ACROSS MOST SOUTH AND WESTERN LOCATIONS SEEMS REASONABLE SAT. I
MAY STILL BE GIVING LINGERING SNOW COVER TOO MUCH CREDIT ACROSS THE NE
PART OF CWA ON SAT AFTER ANOTHER DAY OF MELTING TODAY. GUIDANCE
SHOWING GOOD WAA SUNDAY AHEAD OF CUTOFF LOW AS IT BEGINS TO MOVE
TOWARDS FOUR CORNERS REGION. H85 TEMPS AROUND 10C ACROSS CWA PROGGED
BY MOST GUIDANCE...AND NO LINGERING IMPACTS FROM SNOW COVER
EXPECTED. I CURRENTLY HAVE MID-UPPER 50S IN THE SOUTH AND LOWER 50S
IN THE NORTH WHICH STILL MAY END UP BEING TOO LOW.
DR
.LONG TERM (MONDAY-THURSDAY)...
233 AM MST FRI DEC 16 2011
THE GFS AND NAM ARE IN BETTER AGREEMENT AND MORE PROGRESSIVE THAN
IN THE ECMWF IN BRINGING THE UPPER LOW CENTER INTO THE CENTRAL
TEXAS PANHANDLE REGION BY MID DAY MONDAY. THE ECMWF IS DELAYED
SEVERAL HOURS AND DOESN`T BRING IT INTO A SIMILAR POSITION UNTIL
MONDAY EVENING. THE LOW CENTER IS AS DEEP ON THE ECMWF AS THE
GFS...BUT THE TROUGH THE LOW IN PHASING INTO...AND THE SUBSEQUENT
SECONDARY TROUGH AXIS ACTING AS THE KICKER...ISN`T AS DEEP ON THE
ECMWF. THEREFORE...WHILE CONFIDENCE IS INCREASING FOR MONDAY`S
SOLUTION...CONFIDENCE DIMINISHES THROUGH THE WEEK.
CURRENTLY...IT APPEARS THE SURFACE LOW CENTER EMERGES IN EASTERN NEW
MEXICO AND TRACKS THROUGH THE TEXAS PANHANDLE REGION ON MONDAY WITH
PRECIPITATION SPREADING NORTHWARD INTO THE FORECAST AREA THROUGH THE
DAY AND THEN TAPERING OFF FROM WEST TO EAST AS THE LOW CONTINUES TO
THE EAST NORTHEAST. EXPECT GOOD COLD AIR ADVECTION DURING THE DAY
WITH SOME OVERRUNNING EARLY MONDAY MORNING FOR A POSSIBLE RAIN AND
SNOW MIX THAT CHANGES OVER TO ALL SNOW BY LATE IN THE DAY.
CURRENTLY...ONLY 1-2 INCHES OF SNOW AT THE MOST IS EXPECTED
PRIMARILY ACROSS THE SOUTHEAST PORTION OF THE FORECAST AREA. EXPECT
CLEARING OVERNIGHT MONDAY NIGHT AS THE SYSTEM MOVES FAIRLY QUICKLY
OFF TO THE EAST.
TEMPERATURES WILL WARM SOME TUESDAY AND WEDNESDAY AS A SHORT WAVE
RIDGE ALOFT MOVES ACROSS THE REGION WITH TEMPERATURES EXPECTED TO
COOL AGAIN LATE IN THE WEEK AS THE JET SAGS SOUTH AND ANOTHER TROUGH
TRANSITIONS THE CENTRAL HIGH PLAINS REGION THURSDAY AND FRIDAY.
LOCKHART
&&
.AVIATION...
1020 AM MST FRI DEC 16 2011
VFR CONDITIONS CAN BE EXPECTED FOR THE 12Z TAFS. CURRENT SURFACE
OBSERVATIONS SHOW A SURFACE TROUGH MOVING ACROSS NEBRASKA AND NORTHWEST
KANSAS. UPPER AIR ANALYSIS SHOWS AN UPPER LEVEL TROUGH FOLLOWING
THE SURFACE FEATURE. AS THE TROUGH MOVES THROUGH THE WINDS HAVE
QUICKLY SHIFTED FROM THE WEST TO THE NORTH OR NORTHWEST. WITH
LITTLE MOISTURE TO WORK WITH...A FEW MID AND HIGH CLOUDS CAN BE
EXPECTED AS THE TROUGH MOVES THROUGH. DURING THE EVENING HOURS
WINDS WILL TURN BACK TO THE WEST AS A SURFACE RIDGE OF HIGH
PRESSURE BUILDS INTO WESTERN KANSAS. OVERNIGHT TEMPERATURES WILL
APPROACH THE DEW POINT. AM NOT CONFIDENT ENOUGH FOG WILL FORM TO
PLACE IT IN THE TAFS AS TEMPERATURE AND DEW POINT LOOK TO DROP IN
UNISON DURING THE NIGHT.
JTL
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
NE...NONE.
CO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
620 AM MST FRI DEC 16 2011
.SHORT TERM (TODAY-SUNDAY)...
233 AM MST FRI DEC 16 2011
EARLY MORNING WV IMAGERY AND RUC H5 ANALYSIS SHOW SPLIT-FLOW PATTERN
ACROSS THE EASTERN CONUS...WITH CUTOFF LOW OVER THE BAJA PENINSULA.
CWA CURRENTLY BETWEEN SHORTWAVE TROUGHS...WITH LARGE SCALE
SUBSIDENCE CURRENTLY IN PLACE.
EARLY THIS MORNING...FOG CHANCES HAVE DIMINISHED ACROSS EASTERN
COLORADO. 06Z NAM WOULD KEEP AND FOG/STRATUS SW OF CWA. LATEST RUC
DOESNT BRING BL RH VALUES ABOVE 75% ANYWHERE IN EASTERN COLORADO. I
COULDNT COMPLETELY RULE OUT ISOLATED POCKETS OF FOG NEAR SUNRISE IN
NEAR EXTREME SW PART OF CWA...BUT CONFIDENCE IS TOO LOW TO KEEP
MENTION IN FORECAST FOR NOW.
TODAY-SUNDAY NIGHT...SHORTWAVE TROUGH CURRENTLY OVER SE WYOMING WILL
SWING ACROSS THE CWA TODAY. WITH DEEP DRY LAYER IN PLACE...WILL
ONLY SEE PERIOD OF MID-HIGH CLOUDS. SHORTWAVE RIDGE BUILDS OVER CWA
SAT AND SUNDAY...WITH WARM AND DRY CONDITIONS EXPECTED. HIGHS IN LOW
50S ACROSS MOST SOUTH AND WESTERN LOCATIONS SEEMS REASONABLE SAT. I
MAY STILL BE GIVING LINGERING SNOW COVER TOO MUCH CREDIT ACROSS THE NE
PART OF CWA ON SAT AFTER ANOTHER DAY OF MELTING TODAY. GUIDANCE
SHOWING GOOD WAA SUNDAY AHEAD OF CUTOFF LOW AS IT BEGINS TO MOVE
TOWARDS FOUR CORNERS REGION. H85 TEMPS AROUND 10C ACROSS CWA PROGGED
BY MOST GUIDANCE...AND NO LINGERING IMPACTS FROM SNOW COVER
EXPECTED. I CURRENTLY HAVE MID-UPPER 50S IN THE SOUTH AND LOWER 50S
IN THE NORTH WHICH STILL MAY END UP BEING TOO LOW.
DR
.LONG TERM (MONDAY-THURSDAY)...
233 AM MST FRI DEC 16 2011
THE GFS AND NAM ARE IN BETTER AGREEMENT AND MORE PROGRESSIVE THAN
IN THE ECMWF IN BRINGING THE UPPER LOW CENTER INTO THE CENTRAL
TEXAS PANHANDLE REGION BY MID DAY MONDAY. THE ECMWF IS DELAYED
SEVERAL HOURS AND DOESN`T BRING IT INTO A SIMILAR POSITION UNTIL
MONDAY EVENING. THE LOW CENTER IS AS DEEP ON THE ECMWF AS THE
GFS...BUT THE TROUGH THE LOW IN PHASING INTO...AND THE SUBSEQUENT
SECONDARY TROUGH AXIS ACTING AS THE KICKER...ISN`T AS DEEP ON THE
ECMWF. THEREFORE...WHILE CONFIDENCE IS INCREASING FOR MONDAY`S
SOLUTION...CONFIDENCE DIMINISHES THROUGH THE WEEK.
CURRENTLY...IT APPEARS THE SURFACE LOW CENTER EMERGES IN EASTERN NEW
MEXICO AND TRACKS THROUGH THE TEXAS PANHANDLE REGION ON MONDAY WITH
PRECIPITATION SPREADING NORTHWARD INTO THE FORECAST AREA THROUGH THE
DAY AND THEN TAPERING OFF FROM WEST TO EAST AS THE LOW CONTINUES TO
THE EAST NORTHEAST. EXPECT GOOD COLD AIR ADVECTION DURING THE DAY
WITH SOME OVERRUNNING EARLY MONDAY MORNING FOR A POSSIBLE RAIN AND
SNOW MIX THAT CHANGES OVER TO ALL SNOW BY LATE IN THE DAY.
CURRENTLY...ONLY 1-2 INCHES OF SNOW AT THE MOST IS EXPECTED
PRIMARILY ACROSS THE SOUTHEAST PORTION OF THE FORECAST AREA. EXPECT
CLEARING OVERNIGHT MONDAY NIGHT AS THE SYSTEM MOVES FAIRLY QUICKLY
OFF TO THE EAST.
TEMPERATURES WILL WARM SOME TUESDAY AND WEDNESDAY AS A SHORT WAVE
RIDGE ALOFT MOVES ACROSS THE REGION WITH TEMPERATURES EXPECTED TO
COOL AGAIN LATE IN THE WEEK AS THE JET SAGS SOUTH AND ANOTHER TROUGH
TRANSITIONS THE CENTRAL HIGH PLAINS REGION THURSDAY AND FRIDAY.
LOCKHART
&&
.AVIATION...
609 AM MST FRI DEC 16 2011
VFR CONDITIONS WILL PREVAIL AT KMCK AND KGLD THROUGH FRIDAY AND
SATURDAY. LIGHT SOUTHWEST WINDS WILL TURN NORTHWEST DURING THE DAY
TODAY...AND BACK TO THE WEST SOUTHWEST AGAIN AFTER ABOUT 03Z THIS EVENING.
LOCKHART
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
NE...NONE.
CO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
236 AM MST FRI DEC 16 2011
.SHORT TERM (TODAY-SUNDAY)...
233 AM MST FRI DEC 16 2011
EARLY MORNING WV IMAGERY AND RUC H5 ANALYSIS SHOW SPLIT-FLOW PATTERN
ACROSS THE EASTERN CONUS...WITH CUTOFF LOW OVER THE BAJA PENINSULA.
CWA CURRENTLY BETWEEN SHORTWAVE TROUGHS...WITH LARGE SCALE
SUBSIDENCE CURRENTLY IN PLACE.
EARLY THIS MORNING...FOG CHANCES HAVE DIMINISHED ACROSS EASTERN
COLORADO. 06Z NAM WOULD KEEP AND FOG/STRATUS SW OF CWA. LATEST RUC
DOESNT BRING BL RH VALUES ABOVE 75% ANYWHERE IN EASTERN COLORADO. I
COULDNT COMPLETELY RULE OUT ISOLATED POCKETS OF FOG NEAR SUNRISE IN
NEAR EXTREME SW PART OF CWA...BUT CONFIDENCE IS TOO LOW TO KEEP
MENTION IN FORECAST FOR NOW.
TODAY-SUNDAY NIGHT...SHORTWAVE TROUGH CURRENTLY OVER SE WYOMING WILL
SWING ACROSS THE CWA TODAY. WITH DEEP DRY LAYER IN PLACE...WILL
ONLY SEE PERIOD OF MID-HIGH CLOUDS. SHORTWAVE RIDGE BUILDS OVER CWA
SAT AND SUNDAY...WITH WARM AND DRY CONDITIONS EXPECTED. HIGHS IN LOW
50S ACROSS MOST SOUTH AND WESTERN LOCATIONS SEEMS REASONABLE SAT. I
MAY STILL BE GIVING LINGERING SNOW COVER TOO MUCH CREDIT ACROSS THE NE
PART OF CWA ON SAT AFTER ANOTHER DAY OF MELTING TODAY. GUIDANCE
SHOWING GOOD WAA SUNDAY AHEAD OF CUTOFF LOW AS IT BEGINS TO MOVE
TOWARDS FOUR CORNERS REGION. H85 TEMPS AROUND 10C ACROSS CWA PROGGED
BY MOST GUIDANCE...AND NO LINGERING IMPACTS FROM SNOW COVER
EXPECTED. I CURRENTLY HAVE MID-UPPER 50S IN THE SOUTH AND LOWER 50S
IN THE NORTH WHICH STILL MAY END UP BEING TOO LOW.
DR
.LONG TERM (MONDAY-THURSDAY)...
233 AM MST FRI DEC 16 2011
THE GFS AND NAM ARE IN BETTER AGREEMENT AND MORE PROGRESSIVE THAN
IN THE ECMWF IN BRINGING THE UPPER LOW CENTER INTO THE CENTRAL
TEXAS PANHANDLE REGION BY MID DAY MONDAY. THE ECMWF IS DELAYED
SEVERAL HOURS AND DOESN`T BRING IT INTO A SIMILAR POSITION UNTIL
MONDAY EVENING. THE LOW CENTER IS AS DEEP ON THE ECMWF AS THE
GFS...BUT THE TROUGH THE LOW IN PHASING INTO...AND THE SUBSEQUENT
SECONDARY TROUGH AXIS ACTING AS THE KICKER...ISN`T AS DEEP ON THE
ECMWF. THEREFORE...WHILE CONFIDENCE IS INCREASING FOR MONDAY`S
SOLUTION...CONFIDENCE DIMINISHES THROUGH THE WEEK.
CURRENTLY...IT APPEARS THE SURFACE LOW CENTER EMERGES IN EASTERN NEW
MEXICO AND TRACKS THROUGH THE TEXAS PANHANDLE REGION ON MONDAY WITH
PRECIPITATION SPREADING NORTHWARD INTO THE FORECAST AREA THROUGH THE
DAY AND THEN TAPERING OFF FROM WEST TO EAST AS THE LOW CONTINUES TO
THE EAST NORTHEAST. EXPECT GOOD COLD AIR ADVECTION DURING THE DAY
WITH SOME OVERRUNNING EARLY MONDAY MORNING FOR A POSSIBLE RAIN AND
SNOW MIX THAT CHANGES OVER TO ALL SNOW BY LATE IN THE DAY.
CURRENTLY...ONLY 1-2 INCHES OF SNOW AT THE MOST IS EXPECTED
PRIMARILY ACROSS THE SOUTHEAST PORTION OF THE FORECAST AREA. EXPECT
CLEARING OVERNIGHT MONDAY NIGHT AS THE SYSTEM MOVES FAIRLY QUICKLY
OFF TO THE EAST.
TEMPERATURES WILL WARM SOME TUESDAY AND WEDNESDAY AS A SHORT WAVE
RIDGE ALOFT MOVES ACROSS THE REGION WITH TEMPERATURES EXPECTED TO
COOL AGAIN LATE IN THE WEEK AS THE JET SAGS SOUTH AND ANOTHER TROUGH
TRANSITIONS THE CENTRAL HIGH PLAINS REGION THURSDAY AND FRIDAY.
LOCKHART
&&
.AVIATION...
950 PM MST THU DEC 15 2011
FOR THE 06Z TAFS...AN OUTSIDE CHANCE FOR MVFR-LEVEL REDUCED VIS
EXISTS OVERNIGHT PRIMARILY AT KMCK MAINLY DUE TO LIGHTER WIND
SPEEDS HERE WITH AN EXISTING SNOW PACK. WILL INSERT A LOW VFR VIS
GROUP TO INDICATE AS SUCH. SHOULD SUB-VFR VIS MATERIALIZE IT WILL
RAPIDLY SCATTER SHORTLY AFTER SUNRISE. OTHERWISE VFR CONDITIONS
WILL PREVAIL THROUGH THE PERIOD. WIND SPEEDS WILL REMAIN
RELATIVELY LIGHT THROUGHOUT BUT WILL SHIFT FROM THE S/SW OVERNIGHT
TO THE W/NW BY LATE MORNING/EARLY AFTERNOON AS A WEAK COLD FRONT
PUSHES ACROSS THE AREA.
050
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
NE...NONE.
CO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1011 PM EST SAT DEC 17 2011
.SYNOPSIS...
SNOW SHOWERS WILL SLOWLY END AS WEAK LOW PRESSURE ALOFT EXITS
SUNDAY MORNING. A SLOWING MIDWEST COLD FRONT WILL PROVIDE RAIN
MONDAY AFTERNOON INTO WEDNESDAY WITH PERHAPS A CHANCE OF SNOW
TUESDAY MORNING.
&&
.NEAR TERM /THROUGH SUNDAY/...
PER RECENT SURFACE AND RADAR DATA, COUPLED WITH HRRR AND NAM MODEL
OUTPUT, EXPECT EXITING WEAK LOW PRESSURE ALOFT TO CAUSE LIGHT
SNOW SHOWERS TO SLOWLY END WEST TO EAST OVERNIGHT INTO SUNDAY
MORNING. MOST PLACES WILL GET LITTLE IF ANY ADDED SNOW
ACCUMULATION, WITH PERHAPS UP TO AN INCH ACROSS THE MOUNTAINS.
THE ONLY APPARENT HAZARD AT THIS TIME IS LINGERING BLACK ICE ON
UNTREATED PAVEMENTS.
FORECASTED TEMPERATURES TO BE NEAR NORMAL THIS PERIOD PER RECENT
GFS AND NAM MOS BLEND.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
DRY AND COOL SUNDAY NIGHT INTO EARLY MONDAY AS SURFACE RIDGE MOVES
OFF THE SOUTHEAST ATLANTIC COAST. BY MONDAY AFTERNOON A COLD FRONT WILL
MOVE INTO NORTHWEST PENNSYLVANIA AND CROSS THE REGION MONDAY
NIGHT. THE FRONT WILL STALL OVER NORTHERN WEST VIRGINIA BEFORE
MOVING NORTHWARD TUESDAY AS DEVELOPING LOW PRESSURE MOVES
NORTHEAST OUT OF TEXAS.
MODELS ARE NOW IN GOOD AGREEMENT ON ENOUGH COLD AIR BEHIND FRONT
FOR RAIN TO MIX WITH SNOW FROM PITTSBURGH SOUTH LATER MONDAY NIGHT
INTO TUESDAY MORNING WITH A PERIOD OF ALL SNOW FROM PITTSBURGH
NORTH AS 1000-850MB THICKNESS FALLS BELOW CRITICAL VALUES. BULK OF
PRECIPITATION STILL LOOKS TO BE RAIN AND SNOW ACCUMULATION LOOKS
TO BE LIMITED AS DEEPER MOISTURE WILL BE IN A FAIRLY NARROW BAND
ALONG AND JUST BEHIND THE FRONT. POPS WERE KEPT HIGH CHANCE TO LOW
LIKELY AS EXACT PLACEMENT OF WHERE BOUNDARY STALLS MONDAY NIGHT
WILL DETERMINE WHERE HIGHEST QPF WILL BE. TEMPERATURES TRENDED A
BIT LOWER ON AVERAGE WITH BETTER PUSH OF COLD AIR NOW EXPECTED.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE FORECAST PERIOD BEGINS WITH REASONABLE GFSE/ECMWF/CANADIAN
AGREEMENT THAT THE CUT OFF LOW OFF OF CALIFORNIA WILL EJECT INTO THE
CENTRAL PLAINS BY TUESDAY NIGHT AND PUSH INTO THE UPPER OHIO VALLEY
AS A TROUGH BY WEDNESDAY NIGHT. A FRONTAL BOUNDARY IN THE VICINITY
OF THE AREA ALONG WITH A MID-LEVEL SOUTHWESTERLY FLOW AHEAD OF THIS
SYSTEM WILL ALLOW FOR LIKELY POPS TUESDAY NIGHT INTO EARLY
WEDNESDAY. HIGH CHANCE POPS ARE FORECAST WEDNESDAY AS THE TROUGH
CROSSES THE AREA. GFS/ECMWF INDICATE CRITICAL THICKNESS LINES FOR
WINTRY PRECIP WILL BE WELL NORTH OF THE AREA AND THUS THE FORECAST
IS PREDOMINATELY IN THE FORM OF RAIN UNTIL THE TROUGH SHIFTS EAST
AND ADVECTS COLD AIR IN BEHIND IT. ON THE BACK SIDE OF THE TROUGH, A
MIX OF RAIN AND SNOW SHOWERS ARE FORECAST WEDNESDAY NIGHT BEFORE
PRECIPITATION COMES TO AN END.
THE TROUGH WILL SHIFT WELL EAST OF THE AREA WITH A DRY FORECAST FOR
THURSDAY. GFSE/ECMWF SOLUTIONS ARE HINTING AT A LOW PRESSURE SYSTEM
CLIPPING THE AREA AS IT PASSES TO THE SOUTHEAST ON FRIDAY. THUS HAVE
CHANCE POPS SOUTH OF PITTSBURGH. AFTER THIS POINT, FORECAST IS
CLOSEST TO THE ECMWF WITH ANOTHER TROUGH PASSING THROUGH AND SCHC
POPS FOR SATURDAY. TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE
NORMAL UNTIL SATURDAY WHEN A CANADIAN HIGH USHERS COLDER AIR INTO
THE REGION AND BRINGS TEMPS CLOSER TO SEASONAL NORMALS.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
PER RECENT SURFACE AND RADAR DATA, EXPECT MVFR SNOW SHOWERS TO
CONTINUE TO DECREASE WEST TO EAST OVERNIGHT. STRATOCUMULUS
CEILINGS, CURRENTLY VARYING BETWEEN MVFR AND VFR, WILL BECOME
MAINLY VFR BY DAYTIME SUNDAY, EXCEPT FOR LINGERING MVFR ACROSS THE
I-80 CORRIDOR INTO MIDDAY.
OUTLOOK...SUNDAY NIGHT THROUGH THURSDAY...
HIGH PRESSURE WILL RETURN VFR CONDITIONS SUNDAY NIGHT INTO MONDAY.
THE NEXT LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHWEST MONDAY
NIGHT, RETURNING THE CHANCE OF SHOWERS WITH RESTRICTIONS THROUGH
THURSDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
622 PM EST SAT DEC 17 2011
.SYNOPSIS...
PASSING LOW PRESSURE WILL PROVIDE SNOW SHOWERS WITH A LIGHT SNOW
ACCUMULATION OVERNIGHT ALONG WITH TEMPERATURES IN THE 20S. A
SLOWING MIDWEST COLD FRONT WILL PROVIDE RAIN MONDAY AFTERNOON INTO
WEDNESDAY WITH PERHAPS A CHANCE OF SNOW TUESDAY MORNING.
&&
.NEAR TERM /THROUGH SUNDAY/...
PER RECENT SURFACE AND RADAR DATA, COUPLED WITH HRRR AND NAM MODEL
OUTPUT, EXPECT PASSING WEAK LOW PRESSURE ALOFT WITH LIGHT SNOW
SHOWERS, THAT CAN DEPOSIT A SMALL ACCUMULATION OF SNOW ACROSS THE
UPPER OHIO VALLEY OVERNIGHT. MOST ACCUMULATIONS SHOULD BE AN INCH
OR LESS, EXCEPT POSSIBLE 2 INCH ACCUMULATIONS ON THE HIGHER
RIDGES.
THE GREATER HAZARD AT THIS TIME IS THE DEVELOPMENT OF BLACK ICE
THIS EVENING DUE TO UNTREATED PAVEMENTS, WET FROM THE ALL DAY
LIGHT SNOWFALL, NOW BECOMING ICY AS TEMPERATURES HAVE DROPPED A
COUPLE DEGREES COLDER THAN FREEZING. A SPECIAL WEATHER STATEMENT
HAS BEEN ISSUED HIGHLIGHTING THIS HAZARD.
AS SYSTEM EXITS EAST AND WINDS BACK INTO THE WEST AND SOUTHWEST,
EXPECT LIGHT SNOW SHOWERS TO END, WEST TO EAST, DAYTIME SUNDAY.
FORECASTED TEMPERATURES TO BE NEAR NORMAL THIS PERIOD PER RECENT
GFS AND NAM MOS BLEND.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
DRY AND COOL SUNDAY NIGHT INTO EARLY MONDAY AS SURFACE RIDGE MOVES
OFF THE SOUTHEAST ATLANTIC COAST. BY MONDAY AFTERNOON A COLD FRONT WILL
MOVE INTO NORTHWEST PENNSYLVANIA AND CROSS THE REGION MONDAY
NIGHT. THE FRONT WILL STALL OVER NORTHERN WEST VIRGINIA BEFORE
MOVING NORTHWARD TUESDAY AS DEVELOPING LOW PRESSURE MOVES
NORTHEAST OUT OF TEXAS.
MODELS ARE NOW IN GOOD AGREEMENT ON ENOUGH COLD AIR BEHIND FRONT
FOR RAIN TO MIX WITH SNOW FROM PITTSBURGH SOUTH LATER MONDAY NIGHT
INTO TUESDAY MORNING WITH A PERIOD OF ALL SNOW FROM PITTSBURGH
NORTH AS 1000-850MB THICKNESS FALLS BELOW CRITICAL VALUES. BULK OF
PRECIPITATION STILL LOOKS TO BE RAIN AND SNOW ACCUMULATION LOOKS
TO BE LIMITED AS DEEPER MOISTURE WILL BE IN A FAIRLY NARROW BAND
ALONG AND JUST BEHIND THE FRONT. POPS WERE KEPT HIGH CHANCE TO LOW
LIKELY AS EXACT PLACEMENT OF WHERE BOUNDARY STALLS MONDAY NIGHT
WILL DETERMINE WHERE HIGHEST QPF WILL BE. TEMPERATURES TRENDED A
BIT LOWER ON AVERAGE WITH BETTER PUSH OF COLD AIR NOW EXPECTED.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE FORECAST PERIOD BEGINS WITH REASONABLE GFSE/ECMWF/CANADIAN
AGREEMENT THAT THE CUT OFF LOW OFF OF CALIFORNIA WILL EJECT INTO THE
CENTRAL PLAINS BY TUESDAY NIGHT AND PUSH INTO THE UPPER OHIO VALLEY
AS A TROUGH BY WEDNESDAY NIGHT. A FRONTAL BOUNDARY IN THE VICINITY
OF THE AREA ALONG WITH A MID-LEVEL SOUTHWESTERLY FLOW AHEAD OF THIS
SYSTEM WILL ALLOW FOR LIKELY POPS TUESDAY NIGHT INTO EARLY
WEDNESDAY. HIGH CHANCE POPS ARE FORECAST WEDNESDAY AS THE TROUGH
CROSSES THE AREA. GFS/ECMWF INDICATE CRITICAL THICKNESS LINES FOR
WINTRY PRECIP WILL BE WELL NORTH OF THE AREA AND THUS THE FORECAST
IS PREDOMINATELY IN THE FORM OF RAIN UNTIL THE TROUGH SHIFTS EAST
AND ADVECTS COLD AIR IN BEHIND IT. ON THE BACK SIDE OF THE TROUGH, A
MIX OF RAIN AND SNOW SHOWERS ARE FORECAST WEDNESDAY NIGHT BEFORE
PRECIPITATION COMES TO AN END.
THE TROUGH WILL SHIFT WELL EAST OF THE AREA WITH A DRY FORECAST FOR
THURSDAY. GFSE/ECMWF SOLUTIONS ARE HINTING AT A LOW PRESSURE SYSTEM
CLIPPING THE AREA AS IT PASSES TO THE SOUTHEAST ON FRIDAY. THUS HAVE
CHANCE POPS SOUTH OF PITTSBURGH. AFTER THIS POINT, FORECAST IS
CLOSEST TO THE ECMWF WITH ANOTHER TROUGH PASSING THROUGH AND SCHC
POPS FOR SATURDAY. TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE
NORMAL UNTIL SATURDAY WHEN A CANADIAN HIGH USHERS COLDER AIR INTO
THE REGION AND BRINGS TEMPS CLOSER TO SEASONAL NORMALS.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
COVERAGE OF SNOW IS BEGINNING TO DIMINISH ON AREA RADARS. THINK THAT
THE BULK OF LIGHT-MODERATE SNOW WILL CONCLUDE DURING THE EVENING
HOURS...TAPERING TO SNOW SHOWERS AFTER MIDNIGHT. BULK OF SNOW SHOWER
COVERAGE AFTER MIDNIGHT SHOULD REMAIN NORTH AND EAST OF PITTSBURGH.
ALONG THE INTERSTATE 80 CORRIDOR...CONDITIONS SHOULD REMAIN IFR
OVERNIGHT WITH CONVERGENCE BAND OF SNOW REMAINING FIXED OVER FKL AND
DUJ. ELSEWHERE...CONDITIONS SHOULD BE MVFR OVERNIGHT EXCEPT FOR IFR
VISIBILITIES IN HEAVIER SNOW SHOWERS THIS EVENING.
SNOW SHOWERS SHOULD BE OVER BY SUNDAY MORNING...AND CONDITIONS
WILL GRADUALLY IMPROVE TO VFR AT ALL LOCATIONS SUNDAY AFTERNOON.
OUTLOOK...SUNDAY NIGHT THROUGH THURSDAY...
HIGH PRESSURE WILL RETURN VFR CONDITIONS SUNDAY NIGHT INTO MONDAY.
THE NEXT LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHWEST MONDAY
NIGHT, RETURNING THE CHANCE OF SHOWERS WITH RESTRICTIONS THROUGH
THURSDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
401 AM EST FRI DEC 16 2011
.SYNOPSIS...
MUCH COLDER AIR WILL SETTLE IN OVER THE UPPER OHIO VALLEY THIS
WEEKEND. A WEAK STORM SYSTEM WILL BRING THE CHANCE FOR SNOW
SHOWERS SATURDAY NIGHT AND SUNDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
COLDER AIR HAS SETTLED IN OVER THE AREA. WILL CONTINUE WITH A DRY
FORECAST TODAY. AREA OF VERY DRY MID-LEVEL AIR IS PROGGED TO MOVE
IN OVER THE UPPER OHIO VALLEY THIS MORNING. THIS WILL CONTINUE TO
LOWER INVERSIONS AND PREVENT LES SHOWERS FROM DEVELOPING.
EXPECT A DECREASE IN CLOUD COVER LATER THIS MORNING, WHICH WILL
ALLOW FOR SOME SUNSHINE.
TEMPERATURES WILL BE BELOW NORMAL TODAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
HIGH PRESSURE WILL ALLOW FOR MAINLY DRY WEATHER TONIGHT. WILL
NEED TO INCLUDE A MENTION OF CHC/SCHC POPS LATE TONIGHT AND SAT
MORNING ACROSS THE NORTH AND RIDGES AS MID-LEVEL TROUGH WILL
BRING ANOTHER SHOT OF CAA AND REINFORCE THE NW FLOW.
COLD FRONT WILL CROSS THE AREA SATURDAY NIGHT. PLENTY OF UL
SUPPORT WITH THIS BOUNDARY AND CAA. WILL INCREASE POPS EVERYWHERE
SATURDAY NIGHT INTO SUNDAY MORNING. THERE MAY BE SOME
ACCUMULATIONS, MAINLY ACROSS THE NORTH AND RIDGES.
ON SUNDAY, LOWER AND MID LEVEL FLOW WILL BEGIN TO TURN WESTERLY
AND SNOW SHOWERS WILL DIMINISH WITH TEMPERATURES AGAIN AROUND
NORMAL.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE MODELS CONTINUE TO FLIP-FLOP ON SOLUTIONS FOR SYSTEM
WHICH WILL EFFECT THE REGION NEXT WEEK. WILL MAKE ONLY MINOR
CHANGES TO LONG TERM.
&&
.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
PER RECENT SURFACE AND SATELLITE DATA PLUS HRRR AND NAM MODEL
OUTPUT, EXPECT BRISK WESTERLY LOWLEVEL WINDS TO PRODUCE SCATTERED TO
BROKEN STRATOCUMULUS AT MAINLY VFR LEVELS. NAM MODEL PROFILES SHOW
SURFACE WINDS CAN GUST TO 30 KTS AT TIMES UNTIL 08Z-12Z, THEN
SLACKEN TO MAINLY 10-15 KTS DAYTIME FRIDAY.
OUTLOOK... FRIDAY NIGHT THROUGH TUESDAY...
SURFACE RIDGE SHOULD PROVIDE GENERALLY VFR CONDITIONS FRIDAY NIGHT
INTO EARLY SATURDAY. A SHORT WAVE TROUGH AND ASSOCIATED WEAK SURFACE
FRONT, MOVING ACROSS THE GREAT LAKES, WILL BRING SCATTERED SNOW
SHOWERS AND THE POTENTIAL FOR RESTRICTIONS SATURDAY AFTERNOON INTO
SUNDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS PITTSBURGH PA
114 AM EST FRI DEC 16 2011
.SYNOPSIS...
MUCH COLDER AIR WILL MOVE INTO THE UPPER OHIO VALLEY THIS WEEKEND.
A WEAK SYSTEM WILL BRING THE CHANCE FOR SNOW SHOWERS SATURDAY
NIGHT AND SUNDAY.
&&
.NEAR TERM /THROUGH TODAY/...
COLD FRONT HAS PASSED TO THE EAST OF THE AREA AND COLDER AIR IS
RAPIDLY POURING IN. WILL GO WITH A DRY FORECAST FOR THE REMAINDER
OF THE NIGHT. WILL NEED TO WATCH ACROSS THE NORTH AS SOME LES
SHOWERS COULD DEVELOP BEFORE DAWN, BUT INVERSIONS ARE SINKING AS
VERY DRY MID-LEVEL AIR IS CROSSING THE REGION.
COLD DAY WITH SOME SUNSHINE AS MID-LEVEL NORTHWEST FLOW WILL
CONTINUE TO PROVIDE CAA. WITH PLENTY OF DRY AIR IN THE MID-LEVELS,
DO NOT EXPECT ANY LES TO DEVELOP.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY/...
HIGH PRESSURE WILL ALLOW FOR MAINLY DRY WEATHER TONIGHT. WILL
NEED TO INCLUDE A MENTION OF CHC/SCHC POPS LATE TONIGHT AND SAT
MORNING ACROSS THE NORTH AND RIDGES AS MID-LEVEL TROUGH WILL
BRING ANOTHER SHOT OF CAA AND REINFORCE THE NW FLOW.
COLD FRONT WILL CROSS THE AREA SATURDAY NIGHT. PLENTY OF UL
SUPPORT WITH THIS BOUNDARY AND CAA. WILL INCREASE POPS EVERYWHERE
SATURDAY NIGHT INTO SUNDAY MORNING. THERE MAY BE SOME
ACCUMULATIONS, MAINLY ACROSS THE NORTH AND RIDGES.
ON SUNDAY, LOWER AND MID LEVEL FLOW WILL BEGIN TO TURN WESTERLY
AND SNOW SHOWERS WILL DIMINISH WITH TEMPERATURES AGAIN AROUND
NORMAL.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE MODELS CONTINUE TO FLIP-FLOP ON SOLUTIONS FOR SYSTEM
WHICH WILL EFFECT THE REGION NEXT WEEK. WILL MAKE ONLY MINOR
CHANGES TO LONG TERM.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
PER RECENT SURFACE AND SATELLITE DATA PLUS HRRR AND NAM MODEL
OUTPUT, EXPECT BRISK WESTERLY LOWLEVEL WINDS TO PRODUCE SCATTERED TO
BROKEN STRATOCUMULUS AT MAINLY VFR LEVELS. NAM MODEL PROFILES SHOW
SURFACE WINDS CAN GUST TO 30 KTS AT TIMES UNTIL 08Z-12Z, THEN
SLACKEN TO MAINLY 10-15 KTS DAYTIME FRIDAY.
OUTLOOK... FRIDAY NIGHT THROUGH TUESDAY...
SURFACE RIDGE SHOULD PROVIDE GENERALLY VFR CONDITIONS FRIDAY NIGHT
INTO EARLY SATURDAY. A SHORT WAVE TROUGH AND ASSOCIATED WEAK SURFACE
FRONT, MOVING ACROSS THE GREAT LAKES, WILL BRING SCATTERED SNOW
SHOWERS AND THE POTENTIAL FOR RESTRICTIONS SATURDAY AFTERNOON INTO
SUNDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1231 PM EST FRI DEC 16 2011
UPDATED AVIATION DISCUSSION FOR 18Z TAFS
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW RIDGING INTO WRN CANADA
AND A DOWNSTREAM TROF EXTENDING S INTO THE NRN PLAINS/GREAT LAKES.
FLOW IS SPLIT WITH A WEAKER SRN STREAM FEATURING A MID LEVEL LOW
OVER SRN CA AND A WEAK SHORTWAVE OVER THE SRN PLAINS. A POTENT
SHORTWAVE PASSED THRU THE UPPER GREAT LAKES LAST EVENING...BRINGING
A BOUT OF STRONG WINDS OVER LAKE SUPERIOR AND LAKE ENHANCED SNOW IN
ITS WAKE. WINDS GUSTED TO 58MPH AT GRAND MARAIS AND 61MPH AT
STANNARD ROCK. LES HAS NOTABLY DIMINISHED OVER THE LAST FEW HRS AS
FAST WNW FLOW IS PUSHING SYSTEMS ALONG QUICKLY. NEXT WEAK SHORTWAVE
TROF IS MOVING INTO THE DAKOTAS AND MANITOBA. A MORE IMPORTANT
SHORTWAVE IS TOPPING THE WRN CANADA RIDGE OVER NRN BRITISH COLUMBIA
AND THE SRN YUKON.
&&
.DISCUSSION...
WEATHER THRU THIS FCST PERIOD WILL BE DOMINATED BY A MEAN RIDGE OF
VARYING AMPLITUDE OVER WRN CANADA AND A DOWNSTREAM POLAR VORTEX IN
THE VCNTY OF NRN HUDSON BAY/BAFFIN ISLAND. END RESULT SHOULD BE
SEVERAL QUICK MOVING NRN STREAM SHORTWAVES WITH VERY LITTLE PCPN
OUTSIDE OF AREAS AFFECTED BY SOME LAKE EFFECT/LAKE ENHANCED SNOW
ASSOCIATED WITH PASSING WAVES. FLOW ALSO LOOKS TO REMAIN SPLIT WITH
SRN STREAM WAVES AND ASSOCIATED PCPN PASSING S OF UPPER MI.
OVERALL...IT WILL NOT BE AN ESPECIALLY WINTRY PATTERN HEADING TOWARD
THE LATTER PORTION OF DEC AS NORTHERLY POSITION OF POLAR VORTEX
LARGELY HOLDS ARCTIC AIR N OF THE AREA. ONLY BRIEF INTRUSIONS OF
COLDER AIR WILL OCCUR OVER THE NEXT 7 DAYS.
FOR TODAY...DESPITE 850MB TEMPS IN THE -14 TO -16C RANGE...ONGOING
LES WILL HAVE TO FIGHT DRY AIR/LOW INVERSION. 00Z KINL SOUNDING
SHOWED INVERSION BASED AROUND 875MB/4000FT MSL. NAM/GFS FCST
SOUNDINGS HAVE A GOOD HANDLE ON THIS. ALTHOUGH CONVECTION WILL BE
SHALLOW...THE DENDRITIC SNOW GROWTH TEMP ZONE WILL BE WITHIN THE
CONVECTIVE LAYER. SO...THERE SHOULD BE SOME LIGHT FLUFFY SNOW
ACCUMULATION TODAY OF AN INCH...MAYBE TWO...WHERE LES IS MORE
PERSISTENT. WEAK SHORTWAVE OVER THE DAKOTAS/MANITOBA WILL HAVE
LITTLE IMPACT ON LES THIS AFTN/EVENING AS WEAK QVECTOR DIVERGENCE
DOMINATES. GFS/NAM HAVE ALSO BACKED OFF ON DEEPENING OF MOISTURE
PROFILE WITH PASSING WAVE. LES AFFECTING NW/WNW FLOW FAVORED AREAS
TODAY WILL SHIFT TONIGHT AS WINDS BACK SW AHEAD OF STRONGER
SHORTWAVE (CURRENTLY OVER NRN BRITISH COLUMBIA/SRN YUKON) DROPPING
SE THRU SASKATCHEWAN/MANITOBA.
AS SHORTWAVE DROPS SE THRU THE UPPER GREAT LAKES SAT...HEALTHY DEEP
LAYER FORCING PER QVECTORS WILL OVERSPREAD THE AREA. COMBINED WITH
STEEP MIDLEVEL LAPSE RATES UPWARDS OF 7.5C/KM...WAVE MAY BE ABLE TO
SQUEEZE OUT A BRIEF PERIOD OF LIGHT SNOW AT MOST LOCATIONS. ANY
SYNOPTIC SNOW ACCUMULATION SHOULD BE UNDER AN INCH. 850MB TEMPS
AROUND -10C WILL SUPPORT SOME LAKE ENHANCEMENT OVER WRN UPPER MI AS
WINDS SHIFT FROM SW TO NW. A FEW INCHES OF SNOW CERTAINLY POSSIBLE
OVER THE NW SAT AFTN INTO EARLY SAT EVENING. BRIEF ENHANCEMENT WILL
SHIFT INTO AREAS E OF KMQT SAT EVENING AS WINDS SHIFT NW. THERE MAY
BE SOME LAKE ENHANCEMENT OFF NRN LAKE MICHIGAN INTO THE FAR ERN FCST
AREA SAT AFTN IN THE SW FLOW AHEAD OF THE SHORTWAVE. RIGHT NOW...IT
APPEARS WINDS WILL HAVE TOO MUCH A WRLY COMPONENT TO OFFER MUCH
ENHANCEMENT POTENTIAL FOR SCHOOLCRAFT/LUCE COUNTIES. NW FLOW LES
WILL RAPIDLY DIMINISH SAT NIGHT FROM W TO E AS AIRMASS QUICKLY DRIES
AND INVERSION CRASHES TO 4KFT OR LOWER.
WAA WILL BE UNDERWAY SUN AS NEXT SHORTWAVE MOVES ACROSS SCNTRL
CANADA. ALL GUIDANCE SHOW ASSOCIATED SFC LOW PASSING N OF UPPER MI
SUN NIGHT. WAA/ISENTROPIC ASCENT IS STRONG SUN WITH 40+KT WINDS
ORIENTED PERPENDICULAR TO TIGHTLY SPACED ISOBARS. HOWEVER..AIRMASS
IS VERY DRY AT THE LOWER LEVELS. AT THIS POINT...PLAN TO CARRY A DRY
FCST SUN/SUN NIGHT WITH ANY PCPN N OF UPPER MI. SHALLOW MOISTURE
DROPPING INTO THE AREA BEHIND COLD FRONT WITH 850MB TEMPS FALLING
PERHAPS TO AROUND -12C MAY SUPPORT SOME LIGHT LES/FLURRIES OFF LAKE
SUPERIOR MON INTO MON NIGHT.
TWO MORE SHORTWAVES WILL PASS ACROSS THE AREA DURING THE MIDDLE OF
NEXT WEEK...TUE AND THU. PCPN CHANCES APPEAR LIMITED...AND AIR MASS
MAY NOT EVEN BE COLD ENOUGH TO SUPPORT MUCH IF ANY LAKE EFFECT.
&&
.AVIATION /FOR THE 18Z TAF ISSUANCE/...
NORTHWEST WINDS FLOWING ACROSS LAKE SUPERIOR WILL KEEP CHANCES OF
LAKE EFFECT SNOWS ACROSS MUCH OF UPPER MICHIGAN. OCCASIONAL FLURRIES
WITH MVFR CONDITIONS ARE IN FCST AT ALL SITES INTO THIS EVENING. BY
TONIGHT...JUST SOME MID CLOUDS WILL BE PUSHING ACROSS THE UPPER
LAKES. EXPECT VFR CONDITIONS AT ALL THE TAF SITES TONIGHT. CEILINGS
WILL BEGIN TO LOWER FROM WEST TO EAST STARTING SAT MORNING AHEAD OF
AN UPPER LEVEL DISTURBANCE...BUT SHOULD NOT FALL BELOW VFR LEVELS
UNTIL AFTER THE END OF THIS TAF PERIOD.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
STRONG GALE EVENT WITH EVEN SOME STORM FORCE GUSTS HAS WOUND DOWN.
WINDS BECOME LESS THAN 20 KTS THROUGH TONIGHT AS HIGH PRESSURE
RIDGE SETTLES ACROSS. LIGHT WINDS ARE BRIEF THOUGH AS STRONG AND
QUITE CHANGEABLE WINDS ARE THEN EXPECTED THROUGH EARLY NEXT WEEK.
SOUTHWEST WINDS INCREASE TO 30 KTS ON SATURDAY AS LOW PRESSURE
TROUGH APPROACHES. DESPITE WARM AIR ADVECTION AND HIGHER
STABILITY...STRONG PRESSURE FALLS NORTH OF LK SUPERIOR MAY LEAD TO
GALE FORCE GUSTS OVR CNTRL LK SUPERIOR BTWN KEWEENAW AND ISLE ROYALE
SATURDAY AFTERNOON AND EVENING. WINDS SHIFT NORTHWEST BEHIND TROUGH
BUT THE ARRIVAL OF YET ANOTHER TROUGH FM NORTHWEST ON SUNDAY LEADS
TO MORE STRONG SOUTHWEST WINDS SUNDAY AFTERNOON AND EVENING. GALES
APPEAR POSSIBLE OVR CNTRL LK SUPERIOR ONCE AGAIN. WINDS STAY BTWN
20-30 KTS FOR EARLY NEXT WEEK AS ANOTHER TROUGH IS FORECAST TO MOVE
ACROSS THE AREA.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SYNOPSIS...ROLFSON
DISCUSSION...ROLFSON
AVIATION...TITUS
MARINE...JLA
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
646 AM EST FRI DEC 16 2011
UPDATED AVIATION DISCUSSION FOR 12Z TAFS
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW RIDGING INTO WRN CANADA
AND A DOWNSTREAM TROF EXTENDING S INTO THE NRN PLAINS/GREAT LAKES.
FLOW IS SPLIT WITH A WEAKER SRN STREAM FEATURING A MID LEVEL LOW
OVER SRN CA AND A WEAK SHORTWAVE OVER THE SRN PLAINS. A POTENT
SHORTWAVE PASSED THRU THE UPPER GREAT LAKES LAST EVENING...BRINGING
A BOUT OF STRONG WINDS OVER LAKE SUPERIOR AND LAKE ENHANCED SNOW IN
ITS WAKE. WINDS GUSTED TO 58MPH AT GRAND MARAIS AND 61MPH AT
STANNARD ROCK. LES HAS NOTABLY DIMINISHED OVER THE LAST FEW HRS AS
FAST WNW FLOW IS PUSHING SYSTEMS ALONG QUICKLY. NEXT WEAK SHORTWAVE
TROF IS MOVING INTO THE DAKOTAS AND MANITOBA. A MORE IMPORTANT
SHORTWAVE IS TOPPING THE WRN CANADA RIDGE OVER NRN BRITISH COLUMBIA
AND THE SRN YUKON.
&&
.DISCUSSION...
WEATHER THRU THIS FCST PERIOD WILL BE DOMINATED BY A MEAN RIDGE OF
VARYING AMPLITUDE OVER WRN CANADA AND A DOWNSTREAM POLAR VORTEX IN
THE VCNTY OF NRN HUDSON BAY/BAFFIN ISLAND. END RESULT SHOULD BE
SEVERAL QUICK MOVING NRN STREAM SHORTWAVES WITH VERY LITTLE PCPN
OUTSIDE OF AREAS AFFECTED BY SOME LAKE EFFECT/LAKE ENHANCED SNOW
ASSOCIATED WITH PASSING WAVES. FLOW ALSO LOOKS TO REMAIN SPLIT WITH
SRN STREAM WAVES AND ASSOCIATED PCPN PASSING S OF UPPER MI.
OVERALL...IT WILL NOT BE AN ESPECIALLY WINTRY PATTERN HEADING TOWARD
THE LATTER PORTION OF DEC AS NORTHERLY POSITION OF POLAR VORTEX
LARGELY HOLDS ARCTIC AIR N OF THE AREA. ONLY BRIEF INTRUSIONS OF
COLDER AIR WILL OCCUR OVER THE NEXT 7 DAYS.
FOR TODAY...DESPITE 850MB TEMPS IN THE -14 TO -16C RANGE...ONGOING
LES WILL HAVE TO FIGHT DRY AIR/LOW INVERSION. 00Z KINL SOUNDING
SHOWED INVERSION BASED AROUND 875MB/4000FT MSL. NAM/GFS FCST
SOUNDINGS HAVE A GOOD HANDLE ON THIS. ALTHOUGH CONVECTION WILL BE
SHALLOW...THE DENDRITIC SNOW GROWTH TEMP ZONE WILL BE WITHIN THE
CONVECTIVE LAYER. SO...THERE SHOULD BE SOME LIGHT FLUFFY SNOW
ACCUMULATION TODAY OF AN INCH...MAYBE TWO...WHERE LES IS MORE
PERSISTENT. WEAK SHORTWAVE OVER THE DAKOTAS/MANITOBA WILL HAVE
LITTLE IMPACT ON LES THIS AFTN/EVENING AS WEAK QVECTOR DIVERGENCE
DOMINATES. GFS/NAM HAVE ALSO BACKED OFF ON DEEPENING OF MOISTURE
PROFILE WITH PASSING WAVE. LES AFFECTING NW/WNW FLOW FAVORED AREAS
TODAY WILL SHIFT TONIGHT AS WINDS BACK SW AHEAD OF STRONGER
SHORTWAVE (CURRENTLY OVER NRN BRITISH COLUMBIA/SRN YUKON) DROPPING
SE THRU SASKATCHEWAN/MANITOBA.
AS SHORTWAVE DROPS SE THRU THE UPPER GREAT LAKES SAT...HEALTHY DEEP
LAYER FORCING PER QVECTORS WILL OVERSPREAD THE AREA. COMBINED WITH
STEEP MIDLEVEL LAPSE RATES UPWARDS OF 7.5C/KM...WAVE MAY BE ABLE TO
SQUEEZE OUT A BRIEF PERIOD OF LIGHT SNOW AT MOST LOCATIONS. ANY
SYNOPTIC SNOW ACCUMULATION SHOULD BE UNDER AN INCH. 850MB TEMPS
AROUND -10C WILL SUPPORT SOME LAKE ENHANCEMENT OVER WRN UPPER MI AS
WINDS SHIFT FROM SW TO NW. A FEW INCHES OF SNOW CERTAINLY POSSIBLE
OVER THE NW SAT AFTN INTO EARLY SAT EVENING. BRIEF ENHANCEMENT WILL
SHIFT INTO AREAS E OF KMQT SAT EVENING AS WINDS SHIFT NW. THERE MAY
BE SOME LAKE ENHANCEMENT OFF NRN LAKE MICHIGAN INTO THE FAR ERN FCST
AREA SAT AFTN IN THE SW FLOW AHEAD OF THE SHORTWAVE. RIGHT NOW...IT
APPEARS WINDS WILL HAVE TOO MUCH A WRLY COMPONENT TO OFFER MUCH
ENHANCEMENT POTENTIAL FOR SCHOOLCRAFT/LUCE COUNTIES. NW FLOW LES
WILL RAPIDLY DIMINISH SAT NIGHT FROM W TO E AS AIRMASS QUICKLY DRIES
AND INVERSION CRASHES TO 4KFT OR LOWER.
WAA WILL BE UNDERWAY SUN AS NEXT SHORTWAVE MOVES ACROSS SCNTRL
CANADA. ALL GUIDANCE SHOW ASSOCIATED SFC LOW PASSING N OF UPPER MI
SUN NIGHT. WAA/ISENTROPIC ASCENT IS STRONG SUN WITH 40+KT WINDS
ORIENTED PERPENDICULAR TO TIGHTLY SPACED ISOBARS. HOWEVER..AIRMASS
IS VERY DRY AT THE LOWER LEVELS. AT THIS POINT...PLAN TO CARRY A DRY
FCST SUN/SUN NIGHT WITH ANY PCPN N OF UPPER MI. SHALLOW MOISTURE
DROPPING INTO THE AREA BEHIND COLD FRONT WITH 850MB TEMPS FALLING
PERHAPS TO AROUND -12C MAY SUPPORT SOME LIGHT LES/FLURRIES OFF LAKE
SUPERIOR MON INTO MON NIGHT.
TWO MORE SHORTWAVES WILL PASS ACROSS THE AREA DURING THE MIDDLE OF
NEXT WEEK...TUE AND THU. PCPN CHANCES APPEAR LIMITED...AND AIR MASS
MAY NOT EVEN BE COLD ENOUGH TO SUPPORT MUCH IF ANY LAKE EFFECT.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
NORTHWEST WINDS FLOWING ACROSS LK SUPERIOR WILL KEEP CHANCES OF LK
EFFECT SNOWS ACROSS MUCH OF UPR MICHIGAN. EXPECT IFR CONDITIONS IN
THE MORNING AT KCMX AS UPPER WAVE MOVES ACROSS AND ENHANCES ONGOING
SNOW SHOWERS. OTHERWISE...OCCASIONAL FLURRIES WITH MVFR CONDITIONS
ARE IN FCST AT KIWD AND KSAW. BY TONIGHT...JUST SOME MID CLOUDS WILL
BE PUSHING ACROSS THE UPPER LAKES. EXPECT VFR CONDITIONS AT ALL THE
TAF SITES TONIGHT.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
STRONG GALE EVENT WITH EVEN SOME STORM FORCE GUSTS HAS WOUND DOWN.
WINDS BECOME LESS THAN 20 KTS THROUGH TONIGHT AS HIGH PRESSURE
RIDGE SETTLES ACROSS. LIGHT WINDS ARE BRIEF THOUGH AS STRONG AND
QUITE CHANGEABLE WINDS ARE THEN EXPECTED THROUGH EARLY NEXT WEEK.
SOUTHWEST WINDS INCREASE TO 30 KTS ON SATURDAY AS LOW PRESSURE
TROUGH APPROACHES. DESPITE WARM AIR ADVECTION AND HIGHER
STABILITY...STRONG PRESSURE FALLS NORTH OF LK SUPERIOR MAY LEAD TO
GALE FORCE GUSTS OVR CNTRL LK SUPERIOR BTWN KEWEENAW AND ISLE ROYALE
SATURDAY AFTERNOON AND EVENING. WINDS SHIFT NORTHWEST BEHIND TROUGH
BUT THE ARRIVAL OF YET ANOTHER TROUGH FM NORTHWEST ON SUNDAY LEADS
TO MORE STRONG SOUTHWEST WINDS SUNDAY AFTERNOON AND EVENING. GALES
APPEAR POSSIBLE OVR CNTRL LK SUPERIOR ONCE AGAIN. WINDS STAY BTWN
20-30 KTS FOR EARLY NEXT WEEK AS ANOTHER TROUGH IS FORECAST TO MOVE
ACROSS THE AREA.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SYNOPSIS...ROLFSON
DISCUSSION...ROLFSON
AVIATION...JLA
MARINE...JLA
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
455 AM EST FRI DEC 16 2011
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW RIDGING INTO WRN CANADA
AND A DOWNSTREAM TROF EXTENDING S INTO THE NRN PLAINS/GREAT LAKES.
FLOW IS SPLIT WITH A WEAKER SRN STREAM FEATURING A MID LEVEL LOW
OVER SRN CA AND A WEAK SHORTWAVE OVER THE SRN PLAINS. A POTENT
SHORTWAVE PASSED THRU THE UPPER GREAT LAKES LAST EVENING...BRINGING
A BOUT OF STRONG WINDS OVER LAKE SUPERIOR AND LAKE ENHANCED SNOW IN
ITS WAKE. WINDS GUSTED TO 58MPH AT GRAND MARAIS AND 61MPH AT
STANNARD ROCK. LES HAS NOTABLY DIMINISHED OVER THE LAST FEW HRS AS
FAST WNW FLOW IS PUSHING SYSTEMS ALONG QUICKLY. NEXT WEAK SHORTWAVE
TROF IS MOVING INTO THE DAKOTAS AND MANITOBA. A MORE IMPORTANT
SHORTWAVE IS TOPPING THE WRN CANADA RIDGE OVER NRN BRITISH COLUMBIA
AND THE SRN YUKON.
&&
.DISCUSSION...
WEATHER THRU THIS FCST PERIOD WILL BE DOMINATED BY A MEAN RIDGE OF
VARYING AMPLITUDE OVER WRN CANADA AND A DOWNSTREAM POLAR VORTEX IN
THE VCNTY OF NRN HUDSON BAY/BAFFIN ISLAND. END RESULT SHOULD BE
SEVERAL QUICK MOVING NRN STREAM SHORTWAVES WITH VERY LITTLE PCPN
OUTSIDE OF AREAS AFFECTED BY SOME LAKE EFFECT/LAKE ENHANCED SNOW
ASSOCIATED WITH PASSING WAVES. FLOW ALSO LOOKS TO REMAIN SPLIT WITH
SRN STREAM WAVES AND ASSOCIATED PCPN PASSING S OF UPPER MI.
OVERALL...IT WILL NOT BE AN ESPECIALLY WINTRY PATTERN HEADING TOWARD
THE LATTER PORTION OF DEC AS NORTHERLY POSITION OF POLAR VORTEX
LARGELY HOLDS ARCTIC AIR N OF THE AREA. ONLY BRIEF INTRUSIONS OF
COLDER AIR WILL OCCUR OVER THE NEXT 7 DAYS.
FOR TODAY...DESPITE 850MB TEMPS IN THE -14 TO -16C RANGE...ONGOING
LES WILL HAVE TO FIGHT DRY AIR/LOW INVERSION. 00Z KINL SOUNDING
SHOWED INVERSION BASED AROUND 875MB/4000FT MSL. NAM/GFS FCST
SOUNDINGS HAVE A GOOD HANDLE ON THIS. ALTHOUGH CONVECTION WILL BE
SHALLOW...THE DENDRITIC SNOW GROWTH TEMP ZONE WILL BE WITHIN THE
CONVECTIVE LAYER. SO...THERE SHOULD BE SOME LIGHT FLUFFY SNOW
ACCUMULATION TODAY OF AN INCH...MAYBE TWO...WHERE LES IS MORE
PERSISTENT. WEAK SHORTWAVE OVER THE DAKOTAS/MANITOBA WILL HAVE
LITTLE IMPACT ON LES THIS AFTN/EVENING AS WEAK QVECTOR DIVERGENCE
DOMINATES. GFS/NAM HAVE ALSO BACKED OFF ON DEEPENING OF MOISTURE
PROFILE WITH PASSING WAVE. LES AFFECTING NW/WNW FLOW FAVORED AREAS
TODAY WILL SHIFT TONIGHT AS WINDS BACK SW AHEAD OF STRONGER
SHORTWAVE (CURRENTLY OVER NRN BRITISH COLUMBIA/SRN YUKON) DROPPING
SE THRU SASKATCHEWAN/MANITOBA.
AS SHORTWAVE DROPS SE THRU THE UPPER GREAT LAKES SAT...HEALTHY DEEP
LAYER FORCING PER QVECTORS WILL OVERSPREAD THE AREA. COMBINED WITH
STEEP MIDLEVEL LAPSE RATES UPWARDS OF 7.5C/KM...WAVE MAY BE ABLE TO
SQUEEZE OUT A BRIEF PERIOD OF LIGHT SNOW AT MOST LOCATIONS. ANY
SYNOPTIC SNOW ACCUMULATION SHOULD BE UNDER AN INCH. 850MB TEMPS
AROUND -10C WILL SUPPORT SOME LAKE ENHANCEMENT OVER WRN UPPER MI AS
WINDS SHIFT FROM SW TO NW. A FEW INCHES OF SNOW CERTAINLY POSSIBLE
OVER THE NW SAT AFTN INTO EARLY SAT EVENING. BRIEF ENHANCEMENT WILL
SHIFT INTO AREAS E OF KMQT SAT EVENING AS WINDS SHIFT NW. THERE MAY
BE SOME LAKE ENHANCEMENT OFF NRN LAKE MICHIGAN INTO THE FAR ERN FCST
AREA SAT AFTN IN THE SW FLOW AHEAD OF THE SHORTWAVE. RIGHT NOW...IT
APPEARS WINDS WILL HAVE TOO MUCH A WRLY COMPONENT TO OFFER MUCH
ENHANCEMENT POTENTIAL FOR SCHOOLCRAFT/LUCE COUNTIES. NW FLOW LES
WILL RAPIDLY DIMINISH SAT NIGHT FROM W TO E AS AIRMASS QUICKLY DRIES
AND INVERSION CRASHES TO 4KFT OR LOWER.
WAA WILL BE UNDERWAY SUN AS NEXT SHORTWAVE MOVES ACROSS SCNTRL
CANADA. ALL GUIDANCE SHOW ASSOCIATED SFC LOW PASSING N OF UPPER MI
SUN NIGHT. WAA/ISENTROPIC ASCENT IS STRONG SUN WITH 40+KT WINDS
ORIENTED PERPENDICULAR TO TIGHTLY SPACED ISOBARS. HOWEVER..AIRMASS
IS VERY DRY AT THE LOWER LEVELS. AT THIS POINT...PLAN TO CARRY A DRY
FCST SUN/SUN NIGHT WITH ANY PCPN N OF UPPER MI. SHALLOW MOISTURE
DROPPING INTO THE AREA BEHIND COLD FRONT WITH 850MB TEMPS FALLING
PERHAPS TO AROUND -12C MAY SUPPORT SOME LIGHT LES/FLURRIES OFF LAKE
SUPERIOR MON INTO MON NIGHT.
TWO MORE SHORTWAVES WILL PASS ACROSS THE AREA DURING THE MIDDLE OF
NEXT WEEK...TUE AND THU. PCPN CHANCES APPEAR LIMITED...AND AIR MASS
MAY NOT EVEN BE COLD ENOUGH TO SUPPORT MUCH IF ANY LAKE EFFECT.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
AT KSAW...EXPECT MVFR CONDITIONS TO PREVAIL THROUGH THE FCST PD.
SOME LINGERING SNOW IS POSSIBLE INTO THE EARLY OVERNIGHT WITH A
STRONG NW FLOW...BUT AS NW WINDS DECREASE LATE TONIGHT AND DRIER AIR
MOVES IN FROM THE WEST EXPECT SNOW TO TAPER OFF TO SCT FLURRIES.
AT KCMX AND KIWD...EXPECT MVFR CONDITIONS TO PREVAIL THROUGH THE
PERIOD IN A WNW FLOW. ANY LINGERING IFR VBSYS IN SNOW AND BLOWING
SNOW THIS EVENING SHOULD IMPROVE TO MVFR BY TAF TIME AS WIND GUSTS
DECREASE AND DRIER AIR MOVES IN FROM THE WEST.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
STRONG GALE EVENT WITH EVEN SOME STORM FORCE GUSTS HAS WOUND DOWN.
WINDS BECOME LESS THAN 20 KTS THROUGH TONIGHT AS HIGH PRESSURE
RIDGE SETTLES ACROSS. LIGHT WINDS ARE BRIEF THOUGH AS STRONG AND
QUITE CHANGEABLE WINDS ARE THEN EXPECTED THROUGH EARLY NEXT WEEK.
SOUTHWEST WINDS INCREASE TO 30 KTS ON SATURDAY AS LOW PRESSURE
TROUGH APPROACHES. DESPITE WARM AIR ADVECTION AND HIGHER
STABILITY...STRONG PRESSURE FALLS NORTH OF LK SUPERIOR MAY LEAD TO
GALE FORCE GUSTS OVR CNTRL LK SUPERIOR BTWN KEWEENAW AND ISLE ROYALE
SATURDAY AFTERNOON AND EVENING. WINDS SHIFT NORTHWEST BEHIND TROUGH
BUT THE ARRIVAL OF YET ANOTHER TROUGH FM NORTHWEST ON SUNDAY LEADS
TO MORE STRONG SOUTHWEST WINDS SUNDAY AFTERNOON AND EVENING. GALES
APPEAR POSSIBLE OVR CNTRL LK SUPERIOR ONCE AGAIN. WINDS STAY BTWN
20-30 KTS FOR EARLY NEXT WEEK AS ANOTHER TROUGH IS FORECAST TO MOVE
ACROSS THE AREA.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS...ROLFSON
DISCUSSION...ROLFSON
AVIATION...VOSS
MARINE...JLA
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
1140 PM EST THU DEC 15 2011
LATEST UPDATE...AVIATION...
.SYNOPSIS...(340 PM EST THU DEC 15 2011)
A COLDER AIRMASS CONTINUES TO FILTER INTO SOUTHWEST LOWER MICHIGAN
IN THE WAKE OF A THURSDAY MORNING COLD FRONTAL PASSAGE. WEST TO
NORTHWEST WINDS WILL DROP LOWS INTO THE 20S IN MOST LOCATIONS
TONIGHT. IT WILL BE WINDY THIS EVENING BEFORE WINDS SUBSIDE
CONSIDERABLY OVERNIGHT. LAKE EFFECT SNOW SHOWERS ARE EXPECTED THIS
EVENING AND AGAIN FRIDAY NIGHT INTO SATURDAY. ACCUMULATIONS WILL BE
LIGHT TONIGHT ON THE ORDER OF A DUSTING TO POSSIBLY A HALF INCH IN A
FEW SPOTS. LOCALIZED ACCUMULATIONS FRIDAY NIGHT INTO SATURDAY MAY
REACH AN INCH OR TWO...BUT MOST LOCATIONS WILL SEE VERY LITTLE
ACCUMULATION. EVEN WITH THE COOL DOWN...TEMPERATURES WILL REMAIN
SLIGHTLY ABOVE NORMAL INTO THE WEEKEND.
&&
.SHORT TERM...(1100 PM EST THU DEC 15 2011)
(TONIGHT THROUGH SATURDAY NIGHT)
WE ARE ALLOWING THE WIND ADVISORY HEADLINE FOR OUR LAKESHORE
COUNTIES
TO EXPIRE AT 11 PM. AT 04Z SFC OBS INDICATE WIND SPEEDS ARE STARTING
TO DECREASE SOMEWHAT AND THE DIMINISHING TREND OF WINDS WILL
CONTINUE OVERNIGHT.
REMAINDER OF PREVIOUS SHORT TERM FCST DISCUSSION FOLLOWS...AS FOR
LAKE EFFECT SNOW CHANCES...THERE ARE TWO TIME FRAMES OF
POTENTIAL. THE FIRST BEING THIS EVENING...WHERE DEEPER MOISTURE
INTERACTS WITH INCREASING INSTABILITY. THE DEEPER MOISTURE IS ONLY
IN PLACE THROUGH THE 03Z TO 06Z TIME FRAME THOUGH AFTER WHICH TIME
IT DWINDLES TO 4000-5000FT OR LESS. THIS EVENING...EXPECT SNOW
SHOWER ACTIVITY WITH LIGHT ACCUMULATIONS (INCH OR LESS) ACROSS
CENTRAL LOWER MICHIGAN AND POSSIBLY ALONG THE HIGHWAY 131 CORRIDOR
(GIVEN THE STIFF WESTERLY WINDS DISPLACING BANDS INLAND A BIT). A
WET WARM GROUND WILL COUNTERACT THE SNOW SHOWERS SOME.
RELATIVE HUMIDITY IS QUITE LACKING IN THE OVERNIGHT THROUGH FRIDAY
EVENING TIME FRAME AND THEREFORE NOT EXPECTING MUCH IN THE WAY OF
SNOW SHOWERS DESPITE DELTA T/S IN THE MIDDLE TEENS C.
A COUPLE OF SHORTWAVE TROUGHS ROTATE THROUGH THE REGION FRIDAY NIGHT
INTO SATURDAY WHICH SHOULD GIVE A BOOST TO LAKE EFFECT CLOUDS AND
SNOW SHOWERS. SOME MINOR ACCUMULATIONS ARE POSSIBLE ALONG AND WEST
OF HIGHWAY 131. ENVISION DUSTING TO HALF INCH ACCUMS IN MOST
AREAS...BUT SOME LOCALIZED ACCUMS OF AN INCH OR TWO WILL BE
POSSIBLE.
&&
.LONG TERM...(340 PM EST THU DEC 15 2011)
(SUNDAY THROUGH THURSDAY)
SUNDAY LOOKS DRY AS A SFC HIGH AND NW FLOW ALOFT PRODUCES SOME
SUNSHINE ACROSS THE GREAT LAKES.
MODELS CONTINUE TO BE ON DIFFERENT PAGES WRT THE SRN STREAM LOW
MONDAY AND TUESDAY. BOTH THE ECMWF/GFS SHOW A SRN STREAM SHORT WAVE
BEING KICKED NEWD BY A NRN STREAM WAVE. THE ECMWF HOWEVER TAKES THE
LOW MORE EWD THROUGH THE OHIO VALLEY VS THE GFS THAT TAKES THE LOW
OVER LWR MI. BASED ON THE UPPER WAVE TRACK I TEND TO BUY THE GFS
TRACK MORE. THIS TRACK WOULD ALSO BRING WARMER AIR INTO THE CWA.
THUS WE/LL KEEP THE RAIN/SNOW MIX MON-TUE NIGHT. LIGHT SNOW POSSIBLE
ON THE BACK SIDE OF THE SYSTEM WEDNESDAY AS H8 TEMPS FALL TO -5C IN
NW FLOW. TEMPS WILL CONTINUE TO BE A FEW DEGREES WARMER THAN NORMAL
THROUGH THE PERIOD.
&&
.AVIATION...(1140 PM EST THU DEC 15 2011)
GUSTY WINDS WILL CONTINUE TO DIMINISH THROUGH 09Z AS THE PRESSURE
GRADIENT WEAKENS. CLOUDS SHOULD REMAIN VFR AT THE TAF SITES BUT
SOMEWHAT LOWER CONDITIONS POSSIBLE FURTHER NORTH TOWARD KRQB AND
KCAD. WE WILL BE BETWEEN SYSTEMS FRIDAY SO THE WEATHER IS EXPECTED
TO REMAIN VFR THROUGH THE DAY.
&&
.MARINE...(340 PM EST THU DEC 15 2011)
WILL MAINTAIN THE GALE WARNING THROUGH THIS EVENING AS THE CORE OF
THE WIND LOOKS TO COME THROUGH BETWEEN 400PM AND 1000PM. WE WILL
EXTEND THE GALE SLIGHTLY TO GIVE A LITTLE BIT OF A BUFFER ON THE
BACK END...THROUGH 100 AM. RUC OVERVIEW/S ALONG THE
COAST ARE SHOWING 40 KNOTS OF WIND DOWN TO AROUND 1000FT...WHICH
SHOULD TRANSLATE INTO FREQUENT GALE FORCE GUSTS AT THE COASTAL
SITES. WINDS WILL DROP BELOW GALE FORCE AFTER MIDNIGHT AND WE WILL
NEED A SMALL CRAFT ADVISORY THAT WILL STRETCH INTO THE DAYLIGHT
HOURS OF FRIDAY. SUB SMALL CRAFT ADVISORIES CONDITIONS ARE EXPECTED
FROM FRIDAY EVENING INTO SUNDAY.
&&
.HYDROLOGY...(340 PM EST THU DEC 15 2011)
ONE RIVER FLOOD WARNING (VICKSBURG) AND THREE RIVER FLOOD ADVISORIES
(IONIA...BURLINGTON AND HOLT) ARE CURRENTLY IN EFFECT. WE ARE NOT
EXPECTING MUCH IN THE WAY OF CHANGES TO RIVER HEADLINES AT THIS
POINT GIVEN THE RAINFALL HAS OCCURRED AND IS MAKING IT/S WAY INTO
THE RIVERS. RAINFALL TOTALS RANGED FROM A HALF INCH TO SLIGHTLY OVER
ONE INCH FOR THE LAST 24 HOURS OR SO. COLDER AIR IS NOW SURGING INTO
THE AREA AND THIS WILL ACT TO SLIGHTLY SUPPRESS RUN OFF SLIGHTLY.
SO...BOTTOM LINE RISES WILL CONTINUE THE NEXT COUPLE OF DAYS WITH
MOST SITES IN THE AREA REMAINING UNDER BANKFULL.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...GALE WARNING ENTIRE NEARSHORE AREA THROUGH 100 AM.
&&
$$
SYNOPSIS: DUKE
SHORT TERM: DUKE/LAURENS
LONG TERM: 93
AVIATION: MJS
MARINE: DUKE
HYDROLOGY: DUKE
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1206 PM CST FRI DEC 16 2011
.UPDATE...
18Z AVIATION DISCUSSION ADDED BELOW.
&&
.DISCUSSION...
DECENT BUT NOT STRONG WARM ADVECTION PATTERN WITH SYSTEM OVER THE
DAKOTAS AND THERE HAVE BEEN A FEW OBSERVATIONS WITH VSBYS LESS
THAN 3SM. THE WARM ADVECTION PATTERN APPEARS TO BECOME A BIT MORE
BROAD AS IT SPREADS SOUTHEAST...BUT THE LATEST RUC DOES HOLD ON TO
A CENTER OF QG INSTANTANEOUS PRECIP RATE INTO WEST CENTRAL AND SOUTH
CENTRAL MINNESOTA DURING THE AFTERNOON. THE CHANCES OF MEASURABLE
SNOW ARE SLIM BUT THERE IS ENOUGH OF A SIGNAL TO INCLUDE A SMALL
AREA OF POPS ON A TRACK THROUGH THE ABOVE MENTIONED AREA...WITH
FLURRIES OVER A LARGER AREA. THIS FEATURED MAY STILL BE AFFECTING
SOUTH CENTRAL OR SOUTHEAST MINNESOTA THIS EVENING. A STRONGER WARM
ADVECTION PATTERN WITH ANOTHER WAVE DROPPING SOUTHEAST THROUGH
NORTHWEST ONTARIO INTO THE GREAT LAKES...MAY BRUSH NORTHWEST
WISCONSIN WITH LIGHT SNOW MID DAY ON SATURDAY.
THIS WILL SET UP MOST OF THE CWA IN THE WARM SECTOR SATURDAY NIGHT
AND SUNDAY. IT IT STILL LOOKS WARM...ALTHOUGH THE STRENGTH OF THE
850 MB TEMP ANOMALY IS NOT TOO EXTREME. IT SHOULD BE WARMER THAN
MOST OF THE STANDARD GUIDANCE BUT CLOSER TO THE ECMWF AND A FEW
OF THE BIAS CORRECTED VALUES. A DRY COLD FRONT IS THEN FORECAST TO
MOVE THROUGH LATE SUNDAY NIGHT WITH GUSTY WINDS FOR MONDAY. STILL
NO SIGNIFICANT CHANCE FOR PRECIP WITH THE SPLIT FLOW...WITH OUR
AREA JUST AFFECTED BY SYSTEMS MOVING ACROSS SOUTHERN CANADA IN
THE WEST TO NORTHWEST FLOW. THERE WILL BE ANOTHER CHANCE OF A
MILD DAY MID WEEK...AHEAD OF THE NEXT IN A SERIES FRONTS MOVING
ACROSS THE AREA. THERE MAY A CHANCE OF SOME INTERACTION WITH THE
SOUTHERN STREAM AFTER THE FRONT MOVES THOUGH MID WEEK. WE ONLY
HAVE A SMALL CHANCE OF SNOW OVER MAINLY THE SOUTHERN CWA ON
THURSDAY.
&&
.AVIATION.../18Z TAF ISSUANCE/
WEAK SHORTWAVE MOVING INTO MN LATE THIS MORNING IS SHAKING OUT
SOME SNOW SHOWERS. HAVE SEEN NUMEROUS 2-4SM OBS TO THE WEST
/INCLUDING AXN/ SO BEEFED UP SNOW MENTION AT MANY FIELDS. 850-700
MB RH/FGEN ON THE GFS HANDLING CURRENT SNOW WELL...SO USED IT FOR
MOVING SNOW ACROSS THE AREA TODAY. BASED ON THIS...SNOW SHOULD
MOVE DUE SE FROM ITS CURRENT LOCATION...GRAZING STC/RNH/EAU. BASED
ON WEBCAMS OUT WEST...COULD SEE A HALF INCH OF SNOW OUT OF
THIS...ESPECIALLY AT AXN/RWF. CIGS THROUGH THIS EVENING WILL ALSO
BOUNCE AROUND BETWEEN 020 AND 040...WITH MN TERMINALS BOUNCING IN
AND OUT OF MVFR CONDITIONS. LATE TONIGHT...ANOTHER WAVE WILL MOVE
INTO NRN MN...THEN INTO NRN WI SAT MORNING. SREF PROBS HAVE AN
AREA OF MVFR CIGS MOVING FORM NRN MN INTO CENTRAL WI WITH THIS
FEATURE. IN ADDITION...GFSLAMP AT RNH/EAU SHOW MVFR CIGS
RETURNING SATURDAY MORNING...SO ENDED THE WI TAFS WITH RESTRICTED
CIGS. WINDS WILL REMAIN LGT AND VRB THROUGH TONIGHT...BUT WILL
BEGIN TO APPROACH 10 KTS OUT OF THE S TO W ACROSS MN AS THE SECOND
SHORT WAVE DRIVES A WEAK COLD FRONT ACROSS THE AREA.
KMSP...WITH MVFR SN BEING REPORTED AS FAR NORTH AS AXN...DECIDED
TO INTRODUCE SOME TEMPO MVFR -SN. EXPECT THE NORTH EDGE OF THE SNOW
TO RUN DOWN I-94 INTO THE CITIES...BUT IT COULD REMAIN SOUTH OF
THE AREA. WITH THE SECOND WAVE DROPPING ACROSS MN TONIGHT...MAY
HAVE A PROLONGED PERIOD THROUGH ABOUT 15Z WHERE MSP COULD SEE
BOUTS OF SNOW AND MVFR CIGS...BUT EXPECT PREDOMINATE CONDITIONS TO
REMAIN VFR.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
MPG/JPR
AREA FORECAST DISCUSSION...UPDATED
NWS TWIN CITIES/CHANHASSEN MN
536 AM CST FRI DEC 16 2011
UPDATED FOR 12Z AVIATION DISCUSSION BELOW...
.DISCUSSION...
DECENT BUT NOT STRONG WARM ADEVCTION PATTERN WITH SYSTEM OVER THE
DAKOTAS AND THERE HAVE BEEN A FEW OBSERVATIONS WITH VSBYS LESS
THAN 3SM. THE WARM ADVECTION PATTERN APPEARS TO BECOME A BIT MORE
BROAD AS IT SPREADS SOUTHEAST...BUT THE LATEST RUC DOES HOLD ON TO
A CENTER OF QG INSTANTANEOUS PRECIP RATE INTO WEST CENTRAL AND SOUTH
CENTRAL MINNESOTA DURING THE AFTERNOON. THE CHANCES OF MEASURABLE
SNOW ARE SLIM BUT THERE IS ENOUGH OF A SIGNAL TO INCLUDE A SMALL
AREA OF POPS ON A TRACK THROUGH THE ABOVE MENTIONED AREA...WITH
FLURRIES OVER A LARGER AREA. THIS FEATURED MAY STILL BE AFFECTING
SOUTH CENTRAL OR SOUTHEAST MINNESOTA THIS EVENING. A STRONGER WARM
ADVECTION PATTERN WITH ANOTHER WAVE DROPPING SOUTHEAST THROUGH
NORTHWEST ONTARIO INTO THE GREAT LAKES...MAY BRUSH NORTHWEST
WISCONSIN WITH LIGHT SNOW MID DAY ON SATURDAY.
THIS WILL SET UP MOST OF THE CWA IN THE WARM SECTOR SATURDAY NIGHT
AND SUNDAY. IT IT STILL LOOKS WARM...ALTHOUGH THE STRENGTH OF THE
850 MB TEMP ANOMALY IS NOT TOO EXTREME. IT SHOULD BE WARMER THAN
MOST OF THE STANDARD GUIDANCE BUT CLOSER TO THE ECMWF AND A FEW
OF THE BIAS CORRECTED VALUES. A DRY COLD FRONT IS THEN FORECAST TO
MOVE THROUGH LATE SUNDAY NIGHT WITH GUSTY WINDS FOR MONDAY. STILL
NO SIGNIFICANT CHANCE FOR PRECIP WITH THE SPLIT FLOW..WITH OUR
AREA JUST AFFECTED BY SYSTEMS MOVING ACROSS SOUTHERN CANADA IN
THE WEST TO NORTHWEST FLOW. THERE WILL BE ANOTHER CHANCE OF A
MILD DAY MID WEEK...AHEAD OF THE NEXT IN A SERIES FRONTS MOVING
ACROSS THE AREA. THERE MAY A CHANCE OF SOME INTERACTION WITH THE
SOUTHERN STREAM AFTER THE FRONT MOVES THOUGH MID WEEK. WE ONLY
HAVE A SMALL CHANCE OF SNOW OVER MAINLY THE SOUTHERN CWA ON
THURSDAY.
&&
.AVIATION.../12Z TAF ISSUANCE/
LVFR TO HIGH END MVFR CEILINGS DEVELOPING OVER THE TAF SITES DURING
THE AFTERNOON. A COUPLE OF WEAK UPPER LEVEL DISTURBANCES WILL PASS
TO THE NORTH AND EAST OF OUR FORECAST AREA TODAY/SATURDAY. ANY LIGHT
SNOW OR FLURRIES THAT OCCURS FROM TIME TO TIME SHOULD NOT BE A
PROBLEM...VISIBILITIES SHOULD BE MORE THAN 5 MILES.
KMSP...VFR CONDITIONS WILL PREVAIL THROUGH LATER THIS AFTERNOON.
CEILING HEIGHTS LOWERING TO AROUND 3000 FEET AGL THIS EVENING.
WINDS LIGHT AND VARIABLE.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
JPR/JM
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
407 AM CST FRI DEC 16 2011
.DISCUSSION...
DECENT BUT NOT STRONG WARM ADEVCTION PATTERN WITH SYSTEM OVER THE
DAKOTAS AND THERE HAVE BEEN A FEW OBSERVATIONS WITH VSBYS LESS
THAN 3SM. THE WARM ADVECTION PATTERN APPEARS TO BECOME A BIT MORE
BROAD AS IT SPREADS SOUTHEAST...BUT THE LATEST RUC DOES HOLD ON TO
A CENTER OF QG INSTANTANEOUS PRECIP RATE INTO WEST CENTRAL AND SOUTH
CENTRAL MINNESOTA DURING THE AFTERNOON. THE CHANCES OF MEASURABLE
SNOW ARE SLIM BUT THERE IS ENOUGH OF A SIGNAL TO INCLUDE A SMALL
AREA OF POPS ON A TRACK THROUGH THE ABOVE MENTIONED AREA...WITH
FLURRIES OVER A LARGER AREA. THIS FEATURED MAY STILL BE AFFECTING
SOUTH CENTRAL OR SOUTHEAST MINNESOTA THIS EVENING. A STRONGER WARM
ADVECTION PATTERN WITH ANOTHER WAVE DROPPING SOUTHEAST THROUGH
NORTHWEST ONTARIO INTO THE GREAT LAKES...MAY BRUSH NORTHWEST
WISCONSIN WITH LIGHT SNOW MID DAY ON SATURDAY.
THIS WILL SET UP MOST OF THE CWA IN THE WARM SECTOR SATURDAY NIGHT
AND SUNDAY. IT IT STILL LOOKS WARM...ALTHOUGH THE STRENGTH OF THE
850 MB TEMP ANOMALY IS NOT TOO EXTREME. IT SHOULD BE WARMER THAN
MOST OF THE STANDARD GUIDANCE BUT CLOSER TO THE ECMWF AND A FEW
OF THE BIAS CORRECTED VALUES. A DRY COLD FRONT IS THEN FORECAST TO
MOVE THROUGH LATE SUNDAY NIGHT WITH GUSTY WINDS FOR MONDAY. STILL
NO SIGNIFICANT CHANCE FOR PRECIP WITH THE SPLIT FLOW..WITH OUR
AREA JUST AFFECTED BY SYSTEMS MOVING ACROSS SOUTHERN CANADA IN
THE WEST TO NORTHWEST FLOW. THERE WILL BE ANOTHER CHANCE OF A
MILD DAY MID WEEK...AHEAD OF THE NEXT IN A SERIES FRONTS MOVING
ACROSS THE AREA. THERE MAY A CHANCE OF SOME INTERACTION WITH THE
SOUTHERN STREAM AFTER THE FRONT MOVES THOUGH MID WEEK. WE ONLY
HAVE A SMALL CHANCE OF SNOW OVER MAINLY THE SOUTHERN CWA ON
THURSDAY.
&&
.AVIATION.../06Z TAF ISSUANCE/
SFC WINDS HAVE DECREASED MARKEDLY DURING THE EVENING AS SURFACE HIGH
HAS ADVANCED TO W MN BORDER. SFC RIDGE WILL CONTINUE TO MOVE EAST
TO NEAR WI BORDER BY 18Z. SKC ATTM BUT CLOUDS HAVE BEEN ADVANCING
ACROSS THE DKTS AHEAD OF WEAK UPPER TROF NOW INTO NW NODAK. MODELS
HAVE TURNED DRIER ON PCPN WITH THIS SYSTEM AS MOVES ACROSS AREA ON
FRIDAY...BUT MAY SEE SOME FLURRIES IN WAA AHEAD OF TROF. KEPT VSBYS
ABOVE 6SM AT TAF SITES. CLOUDS IN LOW END VFR OR HIGH END MVFR
SHOULD REACH AXN AROUND 11Z AND THEN SPREAD EASTWARD DURING THE
MORNING/EARLY AFTN.
KMSP...VFR CONDITIONS EXPECTED THROUGH THE PERIOD. MID/HIGH LEVEL
CLOUDS DEVELOPING AHEAD OF NEXT SYSTEM WITH CEILINGS LOWERING TO 4K
FEET AS SYSTEM MOVES INTO THE AREA FRI AFTERNOON. WILL MENTION SOME
FLURRIES AS SYSTEM DROPS SOUTH AND WEAKENS. NORTHWEST SURFACE WINDS
WILL CONTINUE TO WEAKEN OVERNIGHT AND MAY BECOME VARIABLE FOR A TIME
FRIDAY AFTERNOON BEFORE TURNING LIGHT SE.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
JPR/BAP
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
927 PM EST SAT DEC 17 2011
.SYNOPSIS...
MUCH COLDER TEMPERATURES CONTINUE FOR THE OVERNIGHT HOURS AS
TEMPERATURES DROP INTO THE SINGLE DIGITS ABOVE AND BELOW ZERO.
LOCALIZED LAKE CHAMPLAIN LAKE EFFECT SNOW SHOWERS WILL BE
POSSIBLE TONIGHT...WITH SOME LIGHT ACCUMULATION ACROSS THE
CHAMPLAIN VALLEY. MAINLY CLEAR SKIES WILL CONTINUE FOR
SUNDAY...BEFORE A WEAK WARM FRONT PRODUCES SOME CLOUDS AND A
CHANCE OF SNOW SHOWERS LATE SUNDAY INTO MONDAY.
&&
.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
AS OF 927 PM EST SATURDAY...MINOR UPDATE TO SNOW SHOWER/FLURRY
CHANCES ALONG LAKE CHAMPLAIN THROUGH THE REMAINDER OF THE NIGHT.
LOWERING INVERSION HEIGHT AND DRY AIR ADVECTION SHOULD LIMIT
ACTIVITY TO MAINLY VERY LIGHT ACTIVITY WITH LITTLE MORE THAN A
DUSTING OVERNIGHT IN FAVORED AREAS FROM SHELBURNE TO
CHARLOTTE...FERRISBURGH AND THE WESTERN LAKESHORE IN ESSEX COUNTY
NEW YORK FROM WILLSBORO TO WESTPORT. REST OF FCST UNCHANGED.
PRIOR DISCUSSION FROM 622 PM EST SATURDAY...
FORECAST ESSENTIALLY ON TRACK FOR THIS EVENING AND HAVE MADE ONLY
MODEST ADJUSTMENTS TO SKY COVER THROUGH THE EVENING/OVERNIGHT
HOURS BASED OFF IR SATELLITE DATA AND RUC13 850 HPA RH PROGS. THIS
WOULD SUGGEST SKIES TO REMAIN PTLY CLOUDY THROUGH MIDNIGHT OR
SO...THEN TRENDING MAINLY CLEAR IN MOST AREAS BY MORNING OUTSIDE
IMMEDIATE VCNTY OF LAKE CHAMPLAIN. RECENT AIRCRAFT DATA OUT OF
PIERRE TRUDEAU APT IN MONTREAL CONFIRM RUC/NAM/GFS 850 HPA TEMPS
OF AROUND -18C...SO SEE NO REASON TO DISCOUNT PRESENT CHILLY LOW
TEMP FORECAST IN THE -7 TO +7F RANGE BY SUNDAY MORNING...SLIGHTLY
MILDER SOUTH. IN REGARD TO THE CHAMPLAIN LAKE EFFECT...EVOLVING
NORTHERLY TRAJECTORIES AND LAKE-850 HPA AIR TEMP DIFFERENCE NEAR
24C MORE THAN SUFFICIENT TO ALLOW PERIODIC SNOW SHOWERS/FLURRIES
TO CONTINUE OVERNIGHT TO THE SOUTH AND EAST OF THE LAKE. LIMITING
FACTORS INCLUDING SHALLOW BOUNDARY LAYER AND DRY AIR ADVECTION
SHOULD PRECLUDE ANYTHING SUBSTANTIAL HOWEVER. AGAIN...PRESENT FCST
HAS THIS COVERED SO OTHER THAN SKY ADJUSTMENTS NOTED ABOVE...NO
OTHER CHANGES NEEDED AT THIS TIME. ENJOY YOUR EVENING.
&&
.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
AS OF 300 PM EST SATURDAY...MID/UPPER LEVEL RIDGE BUILDS ACROSS
OUR CWA AS SURFACE HIGH PRESSURE SHIFTS TOWARD EASTERN NEW
ENGLAND. GIVEN DEEP DRY LAYER AND PLENTY OF NVA FROM BUILDING
HGHTS...EXPECT MAINLY CLEAR SKIES WITH MAX TEMPS ON SUNDAY AROUND
TEN DEGREES BELOW NORMAL. TEMPS RETURN TO NEAR NORMAL BY SUNDAY
NIGHT AS 850 TEMPS SLOWLY WARM FROM THE NEGATIVE TEENS ON SUNDAY
TO NEGATIVE SINGLE DIGITS SUNDAY NIGHT. MONDAY WILL BEGIN DRY
WITH HIGH PRESSURE STILL IN PLAY...BUT BY LATE MONDAY...ANOTHER
SFC COLD FRNT APPROACHES OUR WESTERN CWA. WITH A GOOD RIBBON OF
850 TO 500MB MOISTURE AND STRONG SFC CONVERGENCE. THIS COMBINED
WITH STEEP 0 TO 2 KM AGL LAPSE RATES...AND POTENTIAL FOR SOME
LAKE MOISTURE INTERACTION...A BAND OF SNOW SHOWERS AND SNOW
SQUALLS LOOKS POSSIBLE LATE MONDAY AFTN INTO MONDAY NIGHT. WINDS
ALSO LOOK STRONG ON MONDAY AS 850 JET PEAKS AROUND 60 KTS DURING
THE AFTERNOON. HAVE CONTINUED WITH MENTION OF LIKELY POPS ACROSS
NORTHERN NY/VT BY 00Z...WITH A QUICK INCH OR TWO OF SNOW
POSSIBLE. TEMPERATURES WILL WARM BACK INTO THE 30S TO NEAR 40F ON
MONDAY...ASSOCIATED WITH SOUTHERLY FLOW AHEAD OF BOUNDARY.
OVERNIGHT MIN TEMPS WILL BE SLIGHTLY WARMER THAN NORMAL WITH
RESIDUAL CLOUDS FROM FRONT AND WINDS PROMOTING MIXING.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 247 PM EST SATURDAY...THE EXTENDED FCST PERIOD STARTS QUIET
AS SFC RIDGE OF HIGH PRESSURE CRESTS OVER NY AND NEW ENGLAND ON
TUESDAY. SHOULD SEE MOSTLY SUNNY SKIES TUESDAY WITH LIGHT WINDS
AND SEASONABLY TEMPS /HIGHS IN THE UPR 20S TO LOWER 30S/. RIDGE
AXIS SHIFTS EAST TUESDAY NIGHT WITH DEVELOPING S-SW WINDS. MAY
SEE TEMPS LEVELING OUT IN THE CHAMPLAIN AND ST. LAWRENCE VALLEYS
WITH INCREASED MIXING AND DEVELOPING WARM ADVECTION REGIME.
MODELS HAVE DIVERGED COMPARED TO PREVIOUS RUNS FOR POTENTIAL
PRECIPITATION SYSTEM WEDNESDAY INTO WEDNESDAY NIGHT. THE 12Z GFS
AND ECMWF SOLNS SHOW THAT THE NORTHERN AND SOUTHERN STREAMS ARE
NO LONGER IN PHASE...WITH SRN STREAM SHORTWAVE TROUGH PRECEDING
NORTHERN STREAM AS VORT MAX EMERGES FROM THE OHIO RIVER VALLEY.
THE 12Z GFS IS A BIT FASTER...WITH VORT PASSING THRU PA AND THEN
OFFSHORE SOUTH OF LONG ISLAND. THE BULK OF ASSOCIATED
PRECIPITATION REMAINS SOUTH OF THE NORTH COUNTRY AS WELL. HIGHEST
POPS WOULD OCCUR LATE TUESDAY NIGHT INTO WEDNESDAY. THE ECMWF IS
ABOUT 12 HRS SLOWER AND WARMER ALOFT...WITH 850MB TEMPS +5C AT
00Z THU. HAVE CUT BACK ON POPS TO 30-40 PERCENT...AND HAVE
INDICATED MIXED PRECIPITATION TYPES BASED. NOT EXPECTING A LOT OF
QPF AT THIS POINT BASED ON ABSENCE OF PHASING AND GFS TRACK. WILL
CONTINUE TO MONITOR...BUT SIGNIFICANT WEATHER IMPACTS LOOK LESS
LIKELY THAN THIS TIME YESTERDAY.
THE 12Z GFS MAINTAINS A MORE SIGNIFICANT UPPER TROUGH LATE NEXT
WEEK AND OFFERS A COLDER SOLN THU-FRI AS COMPARED TO THE ECMWF.
HAVE MADE SOME ADJUSTMENTS BETWEEN THE TWO MODELS...INDICATING
HIGHS MOSTLY IN THE 30S WITH LOWS IN THE 20S...SO SOMEWHAT ABOVE
CLIMO ON TEMPS. CAN`T RULE OUT SOME SNOW SHOWER ACTIVITY
THU/FRI...BUT OVERALL NO SIGNIFICANT WEATHER EXPECTED AT THIS
TIME.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
THROUGH 00Z MONDAY...WHILE 2.5-3KFT CEILINGS CONTINUE AT BTV AND
SLK OVER THE NEXT COUPLE HOURS EXPECT MAINLY VFR CONDITIONS TO
PREVAIL ACROSS THE TAFS THROUGH THE REST OF THE PERIOD.
HOWEVER...PERIODS OF SNOW SHOWERS AS COLD AIR ALOFT MOVES OVER
WARMER LAKE WATERS MAY BRING BRIEF IFR VISIBILITIES TO BTV THROUGH
THE OVERNIGHT. LIGHT/CALM WINDS EXPECTED TONIGHT AND INTO
TOMORROW...THOUGH SOUTH WINDS AROUND 6KTS ARE ANTICIPATED AT MSS.
OUTLOOK 00Z MONDAY THROUGH THURSDAY...HIGH PRESSURE BRINGS MAINLY VFR
CONDITIONS THRU 18Z MONDAY. COLD FRONT MONDAY AFTERNOON INTO
MONDAY NIGHT MAY BRING LOCALLY GUSTY W-NW WINDS TO 25 KTS AND
SCATTERED SNOW SHOWERS WITH A PERIOD OF MVFR OR BRIEF IFR
CONDITIONS. NEXT PRECIPITATION SYSTEM ARRIVES LATE TUESDAY NIGHT
INTO WEDNESDAY...THOUGH CURRENT INDICATIONS ARE THAT BULK OF
PRECIPITATION WILL SLIDE SOUTH OF THE NORTH COUNTRY. A PERIOD OF
SNOW OR MIXED PCPN IS EXPECTED TO BE LIGHT AT THIS TIME.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...NEILES
NEAR TERM...JMG
SHORT TERM...NEILES
LONG TERM...BANACOS
AVIATION...BANACOS/LOCONTO
AREA FORECAST DISCUSSION
NWS BISMARCK ND
1154 PM CST THU DEC 15 2011
.DISCUSSION...THE ADVERTISED WIDESPREAD LIGHT SNOW ACROSS WESTERN
NORTH DAKOTA CONTINUES TO PROGRESS EAST TONIGHT...NOW REACHING INTO
CENTRAL NORTH DAKOTA AND THE CITY OF BISMARCK. SURFACE LOW PRESSURE OVER
EASTERN MONTANA WILL WORK ITS WAY TO NEAR BISMARCK BY 12Z FRIDAY.
HAVE INCREASED POPS TO CATEGORICAL OVER MOST OF SOUTH CENTRAL NORTH
DAKOTA BASED ON LATEST SURFACE OBSERVATIONS AND RADAR TRENDS. THE
NAM TIME-HEIGHT CROSS SECTION CONTINUES TO SHOW THE BEST FORCING
APPROACHING TOWARD 12Z ACROSS KBIS. OVERALL SNOWFALL ACCUMULATIONS
OF AROUND ONE INCH OR LESS LOOKS ON TRACK. ALTHOUGH WE DID HAVE A
PUBLIC REPORT OF 1.5 INCHES AT WATFORD CITY EARLIER...BUT THE BACK
EDGE OF THE SNOW IS NOW APPROACHING THERE. MINOR UPDATES TO HOURLY
AND MINIMUM TEMPERATURES WHICH HAVE BEEN ADJUSTED BASED ON CLOUD
COVER AND UPSTREAM OBSERVATIONS. USED THE LATEST RUC TO UPDATE THE
HOURLY TEMPS THE REST OF THE NIGHT INTO FRIDAY MORNING.
&&
.AVIATION...AT 11 PM CST A LOW PRESSURE AREA OVER SOUTHEAST MONTANA
WAS ASSOCIATED WITH A WARM FRONT EXTENDING FROM THE LOW INTO
NORTHWEST SOUTH DAKOTA. THE LOW AND WARM FRONT WILL MOVE EAST
TONIGHT AND BE THE FOCUS FOR MVFR TO OCNL IFR CONDITIONS IN SNOW
THURSDAY NIGHT AND FRIDAY MORNING. KISN/KDIK/KMOT WILL BE MVFR IN
SNOW AND BR BETWEEN 06Z AND 12Z THEN IMPROVE TO VFR. KBIS CAN EXPECT
IFR CONDITIONS IN SNOW BETWEEN 06Z AND 10Z....IMPROVING TO MVFR
BETWEEN 10Z AND 16Z FRIDAY THEN VFR AFTER 18Z. KJMS WILL BECOME MVFR
AFTER 09Z IN SNOW...BECOMING VFR AFTER 18Z.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KS
AVIATION....WAA
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
957 PM EST SAT DEC 17 2011
.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE SOUTHERN APPALACHIANS THROUGH THE
WEEKEND...REACHING THE COAST ON MONDAY. A TRANSITION TO AN
ACTIVE PATTERN IS EXPECTED BY MID-WEEK...AS LOW PRESSURE MOVING
ACROSS THE OHIO VALLEY DRAGS A COLD FRONT ACROSS OUR REGION. AN AREA
OF LOW PRESSURE WILL THEN MOVE NORTHEAST OUT OF THE GULF COAST
REGION LATE IN THE WEEK.
&&
.NEAR TERM /THROUGH SUNDAY/...
AS OF 950 PM EST...LOWER DEWPOINTS CONTINUE THEIR SLOW TREK TO THE
SOUTH ACROSS THE FA. KCLT HAD A 10 DEG DEWPOINT DROP LAST HOUR...AND
WHILE FOG HAD BEEN DEVELOPING OVER THE NC PIEDMONT...IT/S STARTED TO
DISSIPATE WITH THE DRIER AIR. A POCKET OF MVFR FOG WILL CONTINUE FOR
A FEW MORE HOURS OVER THE NW SC PIEDMONT AND THE FAR SRN NC
PIEDMONT..WHICH HAS BEEN ADDED TO THE GRIDS. AND STRATO-CU IS
HOLDING ON IN A NARROW BAND OVER THE UPSTATE IN AN AXIS OF LLVL
CONVERGENCE. THE RUC INSISTS ON BRINGING IN DRIER AIR...AND I INSIST
ON FOLLOWING IT/S LEAD...SO THE CLOUDS SHOULD DISSIPATE IN A COUPLE
HOURS.
AS OF 725 PM EST...DEWPOINTS CONTINUE TO BE SLOW TO FALL OVER THE
SRN PART OF THE UPSTATE AND THE WRN NC PIEDMONT...THOUGH DRIER AIR
IS SLOWLY MOVING SOUTHWARD. THE GRIDS HAVE BEEN UPDATED TO REFLECT
THIS SLOWING TREND IN DRYING. THERE ARE EVEN A FEW SMALL BUT
PERSISTENT AREAS OF STRATO-CU OVER THE SRN UPSTATE AND ALONG THE
BLUE RIDGE. TWEAKED SKY A BIT TO ACCOUNT FOR THIS...BUT THERE ISN/T
MUCH I CAN DO WITH SUCH A SMALL AREA.
AS OF 430 PM EST...SKIES HAVE FINALLY CLEARED OVER MOST OF THE FA
AND THE GRIDS HAVE BEEN UPDATED TO REFLECT THIS. THERE IS A
CONSIDERABLE TEMPERATURE AND DEWPOINT GRADIENT OVER THE FA AS WELL.
THIS SHOULD GRADUALLY EVEN OUT DURING THE COURSE OF THE
EVENING...BUT SHORT TERM GRID TWEAKS HAVE BEEN MADE TO ACCOUNT FOR
THE CURRENT CONDITIONS.
PREVIOUS DISCUSSION...
NW FLOW HAS BEEN VERY LGT ACROSS THE PIEDMONT TODAY AND LOW CLOUDS
HAVE BEN SLOW TO DISSIPATE. MOISTURE WILL STILL CONTINUE TO SLOWLY
ERODE FROM THE NW AS HIGH PRES BUILDS IN FROM THE W WITH MCLR SKIES
EXPECTED ACROSS THE AREA BY LATE AFTN. SOME LOW LEVEL MOISTURE MAY
MOVE INTO THE TN BORDER MTNS LATE TONIGHT BUT DON`T EXPECT IT TO BE
DEEP ENOUGH FOR SNOW SHWRS. OTHERWISE EXPECT CLR SKIES AND LGT WINDS
OVERNIGHT WITH TEMPS COOLING TO SLIGHTLY BELOW AVG. HI PRES WILL
CONTINUE TO BUILD IN FROM THE W SUN AND WITH PLENTY OF SUNSHINE
HIGHS WILL WARM TO NEAR OR SLIGHTLY ABOVE AVG.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AT 2 PM EST SATURDAY...AN UPPER RIDGE WILL BUILD OVER THE SOUTHEAST
ON MONDAY...AHEAD OF AN UPPER LOW MOVING FROM NW MEXICO INTO TX.
THIS LOW TRACKS INTO THE CENTRAL PLAINS ON TUESDAY...WHILE THE UPPER
RIDGE AMPLIFIES FURTHER OVER THE SOUTHERN APPALACHIANS AND OH RIVER
VALLEY.
DRY HIGH PRESSURE WILL BE OVER THE CAROLINAS AND GA ON MONDAY. ON
TUESDAY THIS HIGH MOVES OFFSHORE...AND RETURN FLOW FROM THE GULF
BRINGS MOISTURE INTO OUR AREA...SUPPORTING A CHANCE OF SHOWERS. THE
HIGHEST POPS WILL BE ALONG THE SOUTH FACING BLUE RIDGE ESCARPMENT...
WHERE NC MEETS SC AND GA...IN UPSLOPE FLOW. AT THIS POINT...MODEL
INSTABILITY IS ALMOST ABSENT THROUGH TUESDAY AFTERNOON...WHILE
HELICITY IS MODEST AT BEST...AND THUNDERSTORMS WILL NOT BE CARRIED
IN THE FORECAST. MAXIMUM TEMPERATURES WILL RUN AROUND FIVE DEGREES
ABOVE NORMAL UNDER THE AMPLIFYING UPPER RIDGE. MINIMUM TEMPERATURES
WILL WARM FROM NEAR NORMAL ON MONDAY TO AROUND FIVE DEGREES ABOVE
NORMAL TUESDAY AS CLOUDS COVER AND MOISTURE INCREASE.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 145 PM SATURDAY...THE MODEL CONSENSUS SEEMS TO BE TRENDING A
LITTLE SLOWER WITH A LOW PRESSURE SYSTEM TRACKING NORTHEASTWARD
ACROSS THE MID MS VALLEY TUESDAY NIGHT THRU WEDNESDAY. THE
ASSOCIATED COLD FRONT MAY NOT EVEN ENTER THE CWFA UNTIL AFTER 12Z
WEDNESDAY. THIS TREND RESULTS IN A BIT MORE INSTBY ALONG THE FRONT
AS IT CROSSES THE CWFA WEDNESDAY AFTN (DURING PEAK HEATING). WITH
THAT SAID...BEST UPPER SUPPORT SHUD STILL BE TO THE NORTH OF THE
AREA WHERE A CLOSED H5 LOW WILL TRACK. SO I HAVE KEPT OUT ANY
MENTION OF THUNDER...BUT HOLD ONTO HIGHER POPS INTO WEDNESDAY AFTN.
TEMPS WILL BE WELL ABOVE NORMAL AHEAD OF THE FRONT.
WEDNESDAY NIGHT AND THURSDAY...THE HIGH PRESSURE IN THE WAKE OF THE
DEPARTING LOW WILL NOT BE ALL THAT STRONG...BUT THERE SHUD BE A
PERIOD OF MOSTLY CLEAR SKIES AND DRY CONDITIONS. TEMPS WILL REMAIN A
FEW CATEGORIES ABOVE NORMAL.
THURSDAY NIGHT THRU SATURDAY...SPLIT UPPER FLOW REGIME WILL
CONTINUE...WITH SOUTHERN STREAM SHORTWAVE ENERGY INITIATING A SFC
WAVE LIKELY SOMEWHERE INVOF THE GULF COAST ALONG A STALLED FRONTAL
BOUNDARY. MOISTURE AND LIFT WILL LIKELY WORK BACK NORTH ACROSS THE
REGION...WITH ANOTHER RELATIVELY QUICK SHOT OF PRECIP. LIKE THE
PREVIOUS SYSTEM...TEMPS/THICKNESSES WILL BE QUITE WARM FOR THIS TIME
OF YEAR...BUT INSTBY LOOKS TO REMAIN NEAR THE GULF COAST. I WENT
WITH A SOLID CHC POP FOR THURSDAY NIGHT AND FRIDAY WITH ABOVE NORMAL
TEMPS. HIGH PRESSURE BEGINS TO BUILD IN SATURDAY WITH DRYING AND
TEMPS BACK DOWN TOWARD NORMAL.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...HIGH PRESSURE WILL BUILD INTO THE REGION
TONIGHT AND SUNDAY. WINDS WILL GENERALLY BE OUT OF THE N TO NW
OVERNIGHT AT LIGHT SPEEDS. THE WINDS WILL GRADUALLY BACK TO THE W OR
SW DURING THE AFTN HOURS ON SUNDAY. THERE IS STILL A NARROW BAND OF
VFR CLOUDS A LITTLE SOUTHEAST OF KGSP...BUT IT SHOULD DISSIPATE
SHORTLY. WITH MUCH DRIER AIR WORKING INTO THE REGION THERE SHOULD BE
LITTLE FOG OVERNIGHT.
OUTLOOK...HIGH PRESSURE WILL REMAIN OVER THE AREA THRU MON. THE NEXT
SYSTEM WILL APPROACH FROM THE W TUE AND MOVE THRU TUE NIGHT-WED...
WITH RESTRICTIONS POSSIBLE.
AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...
WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...PAT
NEAR TERM...MCAVOY/RB
SHORT TERM...JAT
LONG TERM...ARK
AVIATION...MCAVOY
AREA FORECAST DISCUSSION
NWS LUBBOCK TX
1138 PM CST THU DEC 15 2011
.AVIATION...
DISTURBANCE CONTINUES MAKING PROGRESS EAST...NOW INTO WEST TX.
BACK EDGE OF ASSOCIATED MID CLOUD DECK SHOULD CLEAR KLBB TERMINAL
SHORTLY AFTER 08Z THEN KCDS BY 10Z. WINDS REMAIN LIGHT E-NE
OVERNIGHT. LATEST NAM AND RUC INDICATE SOME LIGHT FG DEVELOPING
AROUND SUNRISE ACROSS S PLAINS. ALSO MODEL RH PROGS SHOW CLOUD
DECK CURRENTLY IN ERN NM AND WRN SOUTH PLAINS MAKING SOME PROGRESS
EAST. HAVE LEFT THIS OUT OF KLBB TAF FOR NOW AS LIKLIHOOD LOW FOR
WIDESPREAD MVFR CONDITIONS THAT FAR E WITH ONLY WEAK TO NEUTRAL
ISENTROPIC LIFT AND GENERAL DRYING TAKING PLACE.
&&
.PREV DISCUSSION... /ISSUED 856 PM CST THU DEC 15 2011/
UPDATE...
SHRTWV TROUGH OVER SE NM WILL MOVE ACROSS W TX OVERNIGHT. RADAR
INDICATES ACTIVITY ASSOCIATED WITH THIS FEATURE REMAINS WEAKLY
ORGANIZED ACROSS THE SW PORTION OF THE SOUTH PLAINS INTO SOUTHEAST
NM AND THE PERMIAN BASIN. HAVE EXTENDED MENTION OF
SPRINKLES/FLURRIES ACROSS MUCH OF THE REMAINDER OF THE AREA
OVERNIGHT AS ENERGY SPREADS INTO THE ROLLING PLAINS. TEMP/DPT SPREADS
HAVE DECREASED IN A FEW LOCATIONS INDICATING SOME OF THE PRECIP
WILL HAVE BETTER CHANCE OF REACHING THE GROUND AS IT MOVES EAST
AND NORTHEAST BUT THIS SHOULD REMAIN LIMITED. WITH WETBULB TEMPS
DROPPING TO NEAR FREEZING SOME LIQUID PRECIP COULD CHANGE TO SNOW
BEFORE COMING TO AN END.
PREV DISCUSSION... /ISSUED 354 PM CST THU DEC 15 2011/
SHORT TERM...
UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY SHOW A POSITIVELY-TILTED
SHORTWAVE TROUGH IMMEDIATELY TO OUR WEST WITH WELL-DEFINED H5
VORTMAX LOCATED OVER SRN NM...WHICH WILL BE MOVING ACROSS WTX DURING
THE NEXT 6-9 HRS. MID-LVL ASCENT WITH THIS SYSTEM HAS RESULTED IN A
BAND OF LIGHT SHOWERS...MUCH OF WHICH VIRGA...FROM NEAR EL PASO
NEWD ACROSS SE NM...WHICH WERE EDGING CLOSE TO WRN COCHRAN AND
YOAKUM COUNTIES AT 3 PM. FARTHER EAST AND SOUTH...ISENTROPIC LIFT
OVER THIS MORNING/S COLD FRONT HAS MAINTAINED A BROAD EXPANSE OF
OVERCAST SKIES AND PERIODIC SHOWERS FROM THE ERN PERMIAN BASIN NEWD
THROUGH NORTH TEXAS. A FEW OF THESE SHOWERS HAVE PERIODICALLY
BRUSHED THE SRN ROLLING PLAINS. AT THE SFC...COOL AIR ADVECTION HAS
KEPT TEMPS IN THE LOWER 40S TO NEAR 50F RANGE ACROSS THE FA TODAY.
THIS EVENING...WHILE THE LARGE-SCALE LIFT CONTINUES...WE COULD SEE A
FEW VERY LIGHT SHOWERS MAINLY ACROSS SW AND SE PORTIONS OF THE FA.
WITH SFC DEWPOINT DEPRESSIONS RUNNING 15-20 DEGREES WE COULD EVEN
SEE A FEW FLURRIES MIX IN WITH THE SPRINKLES ON THE CAPROCK...BUT NO
ACCUMULATIONS ARE EXPECTED. PARTIAL CLEARING WILL FOLLOW THE EXITING
LIFT AFTER MIDNIGHT OR SO...AND A COOL EARLY MORNING IS IN STORE
AREA-WIDE WITH LIGHT E-NE WINDS. FRIDAY WILL FEATURE RIDGING AT THE
SFC AND ALOFT BRINGING MOSTLY SUNNY SKIES BUT CONTINUED COOL
TEMPS...WITH HIGHS MAINLY 45F TO 50F.
LONG TERM...
CONFIDENCE OVERALL HAS IMPROVED SUFFICIENTLY CONCERNING THE
BEHAVIOR OF AN IMPRESSIVE UPPER CYCLONE NOW CHURNING OVER SOCAL.
ALL MODELS ARE SURPRISINGLY IN GOOD HARMONY WITH THIS FEATURE
THROUGH THE WEEKEND BEFORE DEVIATIONS BECOME MORE EVIDENT ON
MONDAY. GFS ENSEMBLES ARE NOW TIGHTLY CLUSTERED WITH THE PATH OF
THE 500MB LOW THROUGH MONDAY NIGHT WITH MINIMAL NORTH-SOUTH
DEVIATION. SUCH STRONG AGREEMENT THIS FAR OUT IS UNUSUAL AND
CERTAINLY RAISES A FEW SUSPICIONS ESPECIALLY CONSIDERING THE FACT
THIS LOW HAS YET TO STALL OUT. THIS IS ONE FACTOR THAT THE MODELS
HAVE STRUGGLED WITH IN RECENT DAYS AS THEY HAVE ALL GRADUALLY
TRENDED SLOWER IN EJECTING THE UPPER CYCLONE. SO THERE REMAINS A
WINDOW FOR ADDITIONAL CHANGE IN LATER RUNS...BUT UNTIL THAT CHANGE
IS REALIZED AND PROVEN CREDIBLE...THIS FORECAST HAS TRENDED IN
LINE WITH A NORTHERLY UPPER LOW TRACK.
UPPER CYCLONE SHOULD TRACK GENERALLY NEAR OR JUST SOUTH OF I-40
ON MONDAY SUBJECTING ALL OF THE CWA TO WARM PHASE PRECIP BEFORE
DRY SLOTTING EMERGES MIDDAY. THEREAFTER...THERE REMAINS A WINDOW
FOR DEFORMATION ZONE PRECIP TO EXPAND SOUTHEAST INTO THE DRY SLOT
LATE MONDAY ACCOMPANIED BY CAA...HOWEVER DIMINISHED SATURATION
DEPTHS BY THIS TIME SHOULD CUT BACK ON SNOW AND SUBSEQUENT THREATS
FOR ACCUMULATION.
EC/GFS/CMC THEN DIVE ANOTHER CLOSED LOW INTO SOCAL BY EARLY NEXT
WEEK BEFORE QUICKLY LIFTING IT NORTHEAST AS AN OPEN WAVE. GIVEN
THE RECENT TENDENCY FOR MODELS THIS FAR OUT TO EJECT THESE CUTOFF
LOWS TOO SOON...WILL NOT ENTERTAIN POPS FOR MID-LATE WEEK YET AS
THIS SYSTEM COULD EASILY LINGER AROUND THE BAJA FOR AN EXTRA DAY
IF NOT LONGER.
&&
.PRELIMINARY POINT TEMPS/POPS...
FRIONA 21 44 25 50 29 / 0 0 0 0 10
TULIA 22 45 24 52 30 / 0 0 0 0 10
PLAINVIEW 23 46 25 52 32 / 10 0 0 0 20
LEVELLAND 24 47 25 52 34 / 10 0 0 0 20
LUBBOCK 24 47 26 53 34 / 10 0 0 0 20
DENVER CITY 25 46 25 50 35 / 10 0 0 0 20
BROWNFIELD 25 47 27 51 35 / 10 0 0 0 20
CHILDRESS 28 49 29 55 34 / 10 0 0 0 10
SPUR 28 49 30 54 38 / 10 0 0 0 20
ASPERMONT 31 50 31 55 40 / 20 10 0 0 20
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
24
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
355 PM EST FRI DEC 16 2011
.SYNOPSIS...
A COLD FRONT IS MOVING SOUTHEAST ACROSS FORECAST AREA. THIS
FRONT WILL STALL ACROSS NORTH CAROLINA TODAY. A WAVE OF LOW
PRESSURE IS EXPECTED TO DEVELOP ALONG THE FRONT THIS
AFTERNOON...SPREADING RAIN NORTHWARD ACROSS THE AREA...AND THEN
MOVE OFF THE MID ATLANTIC COAST BY SATURDAY MORNING. HIGH PRESSURE
WILL BUILD BACK ACROSS THE AREA FOR THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 400 PM EST FRIDAY
RAIN CONTINUES TO MOVE ACROSS THE CWA THIS AFTERNOON. A SURGE OF DRY
AIR IN THE LOW LEVELS FROM THE NORTHEAST HAS ALLOWED SOME SLEET TO
MIX IN WITH THE RAIN NORTH OF ROUTE 460. THE BRIEF BREAK IN THE
PRECIP OVER WESTERN AREAS WILL FILL IN THIS AFTERNOON AND
EVENING AS THE SECOND AREA OF RAIN OVER EASTERN KENTUCKY AND
TENNESSEE MOVES ACROSS. THIS RAIN IS BEING CAUSED BY STRONG
ISENTROPIC LIFT IN THE LOWER AND MID LEVELS OUT AHEAD OF AN UPPER
LEVEL WAVE MOVING ACROSS EASTER MISSOURI AND ILLINOIS...AND OVER TOP
THE SURFACE COLD FRONT THAT HAS STALLED JUST TO OUR SOUTH. THIS AREA
OF ISENTROPIC LIFT PUSHES OFF TO OUR EAST PRETTY QUICKLY BETWEEN 7
AND 10 PM. HRRR HAS BEEN HANDLING THIS STORM FAIRLY WELL TODAY...AND
THE LATEST RUN SHOWS THAT THE UPPER LEVEL WAVE WILL CATCH UP WITH
OUR RAIN SHIELD AROUND 9 OR 10PM. ENOUGH MOISTURE WILL STILL BE
PRESENT IN THE COLUMN THAT THIS ADDITIONAL LIFT WILL LIKELY BRIEFLY
ENHANCE THE PRECIP SOMETIME BETWEEN 8PM AND MIDNIGHT. ONCE THIS WAVE
PUSHES ACROSS...RAIN WILL QUICKLY SHUT OFF...WITH IT CLEARING EASTERN
AREAS BY AROUND MIDNIGHT. UPSLOPE CLOUDS WILL PERSIST ACROSS THE
MOUNTAINS THROUGH THE NIGHT...WITH POSSIBLY A FEW SNOW SHOWERS...BUT
NOT EXPECTING MUCH AS MOISTURE BECOMES VERY SHALLOW. MAY SEE SOME
AREAS OF FREEZING DRIZZLE AND FREEZING FOG ACROSS THE HIGHER
ELEVATIONS...ESPECIALLY ACROSS WESTERN GREENBRIER AND NORTHWEST
NORTH CAROLINA. TEMPERATURES WILL DROP BELOW FREEZING IN NORTHWEST
NORTH CAROLINA TOWARDS MORNING...AND THEY WILL LIKELY BE STUCK IN A
THICK LOW CLOUD...WITH SOME ICING AND FREEZING DRIZZLE POSSIBLE.
ANY SNOW FROM THE MAIN BATCH OF PRECIP THIS AFTERNOON AND EVENING
WILL BE CONFINED TO THE HIGHER ELEVATIONS OF SOUTHEAST WEST VIRGINIA
AND THE ALLEGHENY HIGHLANDS. IT IS HERE WHERE TEMPERATURES ALOFT
COOL ENOUGH FOR SNOW THIS EVENING. LOWER ELEVATIONS IN THIS REGION
WILL BE ABOVE FREEZING...AND THUS EXPECT A NON ACCUMULATING RAIN
SNOW MIX. THE HIGHER ELEVATIONS OF
GREENBRIER...SUMMERS...MONROE...AND BATH COUNTIES MAY PICK UP AROUND
AN INCH. WHEN THE PRECIP EXITS...OTHER LOCATIONS WEST OF THE NEW
RIVER VALLEY MAY SEE A BRIEF CHANGE TO SNOW...BUT NOT MORE THAN A
COATING EXPECTED...AS PRECIP WILL BE ENDING AS THE COLD AIR ARRIVES.
WENT CLOSER TO THE WARMER MAV GUIDANCE FOR LOWS TONIGHT AS WINDS
WILL LIKELY STAY UP...WHICH COMBINED WITH SOME CLOUDS...SHOULD
PREVENT MOST AREAS FROM DECOUPLING. SATURDAY WILL BE A MOSTLY SUNNY
DAY...WITH LOW CLOUDS IN THE MOUNTAINS SLOWLY DISSIPATING BY
AFTERNOON. CAA AND 850MB TEMPS IN THE -3C TO -7C RANGE WILL MAKE FOR
A COLD DAY. WENT SLIGHTLY BELOW MOS GIVEN EXPECTED CAA
REGIME...WHICH GIVES TEMPERATURES AROUND 40 IN THE WEST...AND IN THE
MID TO UPPER 40S EAST...GENERALLY A FEW DEGREES BELOW AVERAGE.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/...
AS OF 300 PM EST FRIDAY...
TROUGH SHARPENS A BIT OVER THE MIDDLE ATLANTIC AS THE LAST SHRTWV
ENTERS IT BEFORE A MORE ZONAL UPPER FLOW PATTERN RETURNS EARLY NEXT
WEEK. ALTHOUGH MOISTURE IS SHALLOW...ENOUGH LIFT WITH THIS
DISTURBANCE...SUFFICIENTLY COLD AIR AND UPSLOPE FLOW WILL PRODUCE
SOME SNOW SHOWERS ALONG WESTERN GREENBRIER WITH POSSIBLY SOME
FLURRIES SURVIVING INTO THE SOUTHERN SHENANDOAH AND NEW RIVER VALLEY
INTO SUNDAY MORNING. NOTHING MORE THAN A QUICK COATING OF SNOW IS
EXPECTED THROUGH WESTERN GREENBRIER DURING THIS PERIOD. BASED ON H85
TEMPS GUIDANCE LOOKS A LITTLE WARM FOR SUNDAY. HIGH PRESSURE
ARRIVING BEHIND THIS WAVE SHOULD PRODUCE A VERY COLD MONDAY MORNING
WITH SOME UPPER TEENS POSSIBLY IN THE SHELTERED VALLEYS. SW RETURN
FLOW QUICKLY ARRIVES ON MONDAY AS HIGH PRESSURE MOVES SW TO THE
CAROLINA COAST...ALLOWING AFTERNOON READINGS TO TOUCH 50F AGAIN IF
HIGH CLOUDS HOLD OFF UNTIL MONDAY NIGHT.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 300 PM EST FRIDAY...
THE UPPER RIDGE THAT WAS OVER THE REGION ON MONDAY WILL BE SHORT
LIVED PRIOR TO THE REGION TRANSITIONING INTO A PROGRESSIVE PATTERN.
WE ARE EXPECTING THE CENTER OF THE UPPER RIDGE TO SHIFT SOUTHEAST TO
OVER THE CARIBBEAN BY THE MIDDLE OF NEXT WEEK. THIS WILL OPEN THE
DOOR FOR A PATTERN OF GENERAL TROUGHINESS ACROSS THE CENTER OF THE
COUNTRY WITH DISTINCT SYSTEMS ROUNDING THE BASE OF THE
TROUGH...COLLECTING SOME GULF OF MEXICO MOISTURE...AND THEN MOVING
ACROSS OUR REGION. MODEL GUIDANCE HAS BEEN SHOWING TO UNIQUE
ATTRIBUTES. THE GFS HAS BEEN MORE PROGRESSIVE WITH THE SYSTEMS
COMPARED RELATIVELY WITH THE ECWMF. BOTH SOLUTIONS HAVE BEEN
TRENDING SLOWER ON ARRIVAL TIMES AS COMPARED TO EARLIER MODEL RUNS.
THIS I BELIEVE SUPPORTS FAVORING THE SLOWER ECMWF SOLUTIONS...WITH
ANTICIPATION THAT IT TOO WILL CONTINUE TO TREND SLOWER TO SOME
DEGREE WITH EACH NEW MODEL RUN. THIS LINE OF THINKING IS
COMPARABLE...NOT NOT IDENTICAL TO THE GRIDDED GUIDANCE PUT FORTH BY
HPC. WILL USED A MODIFIED APPROACH TO THE HPC GUIDANCE
TODAY...KEEPING A SLOWER TREND OF SYSTEMS IN MIND.
GRADUALLY DURING THE DAY TUESDAY...EXPECT LIGHT RAIN TO GRADUALLY
SPREAD ACROSS THE REGION FROM WEST TO EAST IN ASSOCIATION WITH
DEVELOPING WARM FRONT JUST TO OUR NORTH. THE COVERAGE IS EXPECTED TO
INCREASE TUESDAY NIGHT AS ISENTROPIC LIFT INCREASES EVEN MORE. ON
WEDNESDAY...THE CENTER OF LOW PRESSURE WILL PASS NEAR WV/PA WITH AN
ASSOCIATED COLD FRONT MOVING ACROSS OUR REGION. ANTICIPATE THE
PRECIPITATION TO BECOME MORE SHOWERY. CONVECTIVE PARAMETERS ARE
SUGGESTING SOME VERY WEAK CAPE AND LI VALUES AROUND ZERO IN THE
AFTERNOON IN THE EASTERN PART OF THE ARE. NOT IMPRESSIVE NUMBERS FOR
THE SUMMERTIME...BUT FOR MID DECEMBER...I BELIEVE IT WARRANTS A
MENTION OF ISOLATED THUNDER. THIS SYSTEM WILL EXIT THE REGION
QUICKLY WEDNESDAY NIGHT WITH A BRIEF PERIOD OF UPSLOPE RA/SN SHOWERS
ACROSS SE WV.
DRY WEATHER BRIEFLY RETURNS ON THURSDAY. HOWEVER...FOR FRIDAY EXPECT
A SITUATION COMPARABLE TO WHAT IS EXPECTED FOR TUESDAY. INSENTROPIC
LIFT WILL BEGIN TO ORGANIZE IN ADVANCE OF ANOTHER QUICK MOVING
SYSTEM MOVING THROUGH THE WESTERN GULF COAST STATES. WHILE WE ONLY
MENTION RAIN OR SNOW FOR PRECIPITATION TYPES THIS FAR OUT IN THE
FORECAST BECAUSE OF THE UNCERTAINTY FACTOR...LATEST LOW LEVEL
TEMPERATURE AND MOISTURE PROFILES SUGGEST THAT FREEZING RAIN OR
SLEET COULD OCCUR ALONG AND NEAR THE I-64 CORRIDOR OF WV AND
NEIGHBORING SW VA WEST OF I-81 LATE THURSDAY NIGHT INTO FRIDAY
MORNING...BEFORE TRANSITIONING TO RAIN AS LOW LEVEL AND SURFACE
TEMPERATURES RISE THROUGHOUT THE DAY.
&&
.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
AS OF 1235 PM EST FRIDAY...
A SHORT WAVE MOVING QUICKLY ACROSS THE TENNESSEE VALLEY WILL BRING
AN AREA OF PRECIPITATION...AND ASSOCIATED MVFR CEILINGS...THROUGH
THE FORECAST AREA BEFORE 06Z TONIGHT. BASED ON RADAR TRENDS AT
17Z...THE LEADING EDGE OF THE RAINFALL WILL REACH DAN AND LYH
AROUND THE START OF THE 18Z TAF PERIOD.
COLDER AIR SINKING SOUTH THROUGH THE MID ATLANTIC REGION WILL COLL
THE AIR MASS THIS AFTERNOON AND TONIGHT. BUFKIT SOUNDINGS SHOWED
TEMPERATURES COOL ENOUGH FOR SNOW AT LWB...BLF AND POSSIBLY BCB BY
AROUND 00Z TONIGHT. ANY SNOW FALL AMOUNTS WILL REMAIN LIGHT WITH
THE PRECIPITATION ENDING AT THESE STATIONS BY 03Z.
LOWER CONFIDENCE WITH THREAT OF FOG OVERNIGHT ONCE THE
PRECIPITATION ENDS. IF CLOUDS CLEAR OUT QUICKLY THE PROBABILITY OF
MVFR TO IFR FOG WILL BE HIGHER.
A WEAK SHORT WAVE IN THE NORTHERN STREAM WILL BRIEFLY BRING MVFR
CEILINGS BACK INTO SOUTHEAST WEST VIRGINIA...INCLUDING BLF AND LWB
SATURDAY AFTERNOON AND EVENING...POSSIBLY WITH SOME LIGHT SNOW
SHOWERS. OTHERWISE...HIGH PRESSURE WILL THEN FOLLOW THIS SYSTEM
LATER SATURDAY INTO SUNDAY RESULTING IN A RETURN TO VFR ACROSS
THE REGION FOR THE END OF THE WEEKEND.
ANOTHER COLD FRONT AND LOW PRESSURE SYSTEM WILL APPROACH THE
REGION FROM THE WEST TUESDAY...AND MAY BRING SUB-VFR CONDITIONS BY
TUE NIGHT.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...JJ/MC
NEAR TERM...MC
SHORT TERM...KM
LONG TERM...DS
AVIATION...AMS/PM
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
901 PM CST SAT DEC 17 2011
.SHORT TERM...TONIGHT
901 PM CST SAT DEC 17 2011
THE MAIN CHANGE FOR OVERNIGHT WITH THE FORECAST WAS TO ADD IN SOME
FOG MENTION ACROSS THE REGION.
LOW LEVEL STRATUS HAS CLEARED MUCH OF THE FORECAST AREA WITH THE
BACK EDGE OF IT RUNNING THROUGH TAYLOR/NORTHEAST CLARK DOWN TO
JUNEAU AND ADAMS COUNTY. WITH WESTERLY LOW LEVEL WINDS IN
PLACE...THESE CLOUDS SHOULD CONTINUE TO MARCH EASTWARD OVER THE
NEXT FEW HOURS.
WITH THE COMBINATION OF CLEARING AND WARMER LOW LEVEL AIR
STARTING TO ADVECT INTO THE REGION...18.01Z RUC SOUNDINGS FROM THE
REGION ARE SHOWING A STEEP INVERSION SETTING UP OFF OF THE SURFACE
UP TO AROUND 1KFT. WITH A WEAK SURFACE RIDGE COMING
THROUGH...WINDS HAVE/WILL DROP OFF TO JUST A FEW KNOTS BEFORE
COMING AROUND TO THE SOUTH AROUND DAYBREAK TOMORROW MORNING. WITH
DEW POINTS STILL IN THE MID 20S...ANY RADIATIONAL COOLING SHOULD
LEAD TO SMALL SURFACE DEW POINT DEPRESSIONS.
THESE CONDITIONS ARE EXPECTED TO LEAD TO SOME FOG DEVELOPMENT
OVERNIGHT WITH PLATTEVILLE ALREADY DROPPING DOWN TO 3/4SM. THE TWO
HINDRANCES TO THE FOG DEVELOPMENT IS WITH THE WINDS EXPECTED TO
PICK UP THROUGH THE MORNING ALONG WITH SOME CIRRUS MOVING IN FROM
THE WEST THAT MAY LIMIT RADIATIONAL COOLING. REGARDLESS...IT LOOKS
LIKE ENOUGH OF A CHANCE TO WARRANT PUTTING IN THE FORECAST AT THIS
TIME. WITH TEMPERATURES BELOW FREEZING...THERE COULD BE SOME SLICK
SPOTS THAT DEVELOP ON AREA ROADS THOUGH MANY OF THEM HAVE BEEN
TREATED FOR THE SNOW THAT FELL LAST NIGHT. THERE COULD ALSO BE
SOME HOAR FROST THAT DEVELOPS IN ANY AREAS THAT SEES THE DENSER
FOG. AT THIS POINT...NOT EXPECTING TO HAVE TO ISSUE A DENSE FOG
ADVISORY OVERNIGHT...BUT CONDITIONS WILL BE MONITORED.
.LONG TERM...TUESDAY THROUGH SATURDAY
217 PM CST SAT DEC 17 2011
GOOD AGREEMENT EARLY IN THE PERIOD BETWEEN THE MODELS THAT THE
SURFACE LOW TRACKING ALONG THE COLD FRONT WILL STAY WELL SOUTH OF
THE REGION KEEPING THE AREA DRY THROUGH THE MIDDLE OF THE WEEK.
AFTER THAT THERE ARE SOME DIFFERENCES THAT SHOW UP. THE 17.00Z
ECMWF SHOWS ANOTHER LOW GETTING CUT OFF OVER THE DESERT SOUTHWEST
WITH A PRETTY STRONG NORTHERN STREAM SHORT WAVE TROUGH COMING
ACROSS THE UPPER MIDWEST THURSDAY THROUGH FRIDAY. THE 17.12Z GFS
AND GEM ALSO SHOW A TROUGH INTO THE DESERT SOUTHWEST BUT DO NOT
INDICATE A CUT OFF LOW NOR DO THEY HAVE THE NORTHERN STREAM WAVE.
AS A RESULT...THE ECMWF IS THE ONLY MODEL SHOWING ANY
PRECIPITATION ACROSS THE REGION FOR THURSDAY AND THURSDAY NIGHT.
INTERESTINGLY...THE 17.12Z GFS ENSEMBLE DOES SHOW A LOW PROBABILITY
OF SOME PRECIPITATION THURSDAY SIMILAR TO THE ECMWF. WILL CARRY
JUST A SLIGHT CHANCE OF SOME PRECIPITATION ACROSS THE NORTH TO
HONOR THE ECMWF SOLUTION.
&&
.AVIATION...TONIGHT AND SUNDAY
536 PM CST SAT DEC 17 2011
MVFR STRATUS HAS BEEN A BIT PESKY AT LSE ON THE BACK SIDE OF THE
UPPER LEVEL TROUGH...BUT SHOULD BE CLEAR OF THE SITE BY 0030-0100Z
BASED ON CURRENT EXTRAPOLATION OF THE BACK EDGE OF THE CLOUDS.
SKIES HAVE CLEARED AT RST ALREADY AND SHOULD REMAIN THAT WAY
THROUGH THE EVENING...ALONG WITH LSE ONCE THE LOW CLOUDS
LEAVE...BUT SOME HIGH CLOUDS WILL BEGIN MOVING IN AFTER MIDNIGHT
FROM THE WEST. THERE IS SOME CONCERN THAT FOG WILL DEVELOP TONIGHT
THOUGH THE FORECAST MODELS ARE NOT HINTING AT MUCH RIGHT NOW. DEW
POINTS ARE STILL INTO THE MID 20S WITH THE MODELS SUGGESTING THAT
THEY SHOULD BE IN THE UPPER TEENS TO AROUND 20. WITH WARM LOW
LEVEL AIR RAPIDLY DEVELOPING A STRONG LOW LEVEL INVERSION AS SKIES
CLEAR OUT AND SURFACE TEMPERATURES DROP...WOULD NOT BE SURPRISED
TO SEE SOME MVFR TO IFR FOG FORM. MUCH OF THIS HINGES ON HOW MUCH
THE WINDS DROP OFF TONIGHT...WHICH CURRENTLY APPEAR TO BE IN THE
3-5KT RANGE WITH A RIDGE OF HIGH PRESSURE MOVING THROUGH. GIVEN
THIS POSSIBILITY BUT LOW UNCERTAINTY...HAVE FOR THE TIME BEING
ADDED SOME 4-6SM VISIBILITIES TONIGHT AT BOTH LSE AND RST.
CONDITIONS WILL IMPROVE QUICKLY TOMORROW MORNING AS THE WINDS PICK
UP OUT OF THE SOUTH AHEAD OF THE NEXT SYSTEM WITH SOME GUSTS IN
THE 18-22KT RANGE IN THE AFTERNOON.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
217 PM CST SAT DEC 17 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
327 PM CST FRI DEC 16 2011
.SHORT TERM...
326 PM CST FRI DEC 16 2011
HAVE INCREASED SNOW CHANCES TONIGHT ACROSS THE SOUTH INTO LIKELY
CATEGORY. THIS WAS BASED ON 18Z NAM/LATEST RUC TRENDS WHICH NOW
SHOW COLUMN SATURATION SHOULD BE MUCH OF A PROBLEM GIVEN FAIRLY
STRONG PUSH OF ISENTROPIC LIFT AND MODERATE BAND OF 850-700MB
FRONTOGENESIS CENTERED AROUND 06Z. CURRENT THINKING IS THAT AROUND
A HALF INCH OF SNOW WILL BE POSSIBLE WITH THE MAIN AXIS EXTENDING
FROM NEAR ROCHESTER MN TO PLATTEVILLE WI.
REST OF PREVIOUS SHORT TERM DISCUSSION:
NORTHWEST FLOW CONTINUES TO AFFECT THE AREA ON SATURDAY AS YET
ANOTHER SHORTWAVE TROUGH ROTATES OUT OF CANADA TOWARD THE AREA. THIS
TIME IT APPEARS THE BEST FORCING WILL REMAIN NORTHEAST OF I-94...SO
KEPT CHANCE CONFINED ACROSS THAT AREA. THIS BEING SAID...IT APPEARS
LIKE ANOTHER VERY LIGHT SNOW EVENT WITH NOT MUCH MORE THAN A COUPLE
TENTHS OF AN INCH EXPECTED.
WITH MAIN UPPER LEVEL TROUGHINESS PUSHING EAST OF THE REGION ON
SUNDAY...HEIGHTS BUILD NICELY ACROSS THE PLAINS/UPPER MISSISSIPPI
RIVER REGION. THE NAM BRINGS 925MB AIR OF 4-8C INTO THE AREA WITH
AMPLE SUNSHINE. WITH BARE GROUND...THIS HEATING SHOULD WARM HIGHS
INTO THE 35-40 DEGREE RANGE NORTHEAST OF I-94...AND INTO THE 40-45
DEGREE RANGE ACROSS THE SOUTHWEST.
A COLD FRONT IS THEN SLATED TO MOVE ACROSS THE AREA SUNDAY
NIGHT/MONDAY. NAM DOES INDICATE AN INCREASE IN LOWER LEVEL 0.5-1KM
RH/STRATUS ACROSS THE AREA AS THE FRONT APPROACHES PASSES. MAY HAVE
TO KEEP AN EYE ON THIS FOR PERHAPS SOME DRIZZLE POTENTIAL...BUT WILL
KEEP DRY FOR NOW.
CLEARING THEN EXPECTED MONDAY NIGHT AS HIGH PRESSURE BUILDS IN FROM
THE NORTHERN PLAINS.
.LONG TERM...TUESDAY THROUGH FRIDAY
205 PM CST FRI DEC 16 2011
16.12Z GFS/ECMWF MAINTAIN A RATHER QUIET WEATHER REGIME ACROSS THE
REGION THROUGH THE PERIOD WITH SPLIT NORTHERN/SOUTHERN STREAM FLOW.
THIS KEEPS CYCLONE TRACKS ACROSS CANADA AND ACROSS THE SOUTHERN
PLAINS/SOUTHEAST WITH OUR AREA DRY THROUGH THURSDAY. MAY HAVE TO
WATCH FOR LAST-DITCH CHANCE FOR A WHITE CHRISTMAS CHANCE OF LIGHT
SNOW ON FRIDAY AS A MID-LEVEL TROUGH PASSES ACROSS THE AREA. THE
ECMWF REMAINS DRY WITH THIS FEATURE WHILE THE GFS SHOWS SOME
FRONTOGENESIS/BAND OF LIGHT SNOW POTENTIAL. WENT WITH THE MODEL
CONSENSUS/SLIGHT CHANCE POP FOR NOW.
&&
.AVIATION...THROUGH 18Z SATURDAY
1135 AM CST FRI DEC 16 2011
UPSTREAM SHORT WAVE TROUGH OVER THE DAKOTAS IS SET TO MOVE ACROSS
THE AREA TONIGHT. BOTH THE 16.12Z NAM AND GFS SUGGEST THIS WAVE
WILL BE STRONG ENOUGH TO PRODUCE SATURATION RESULTING IN SOME
LIGHT SNOW FOR BOTH TAF SITES. UPSTREAM OBSERVATIONS INDICATE THE
SNOW IS ENOUGH TO REDUCE THE VISIBILITY TO MVFR WITH SOME IFR
POSSIBLE AS WELL. WILL USE THESE OBSERVATIONS AS A STARTING POINT
AND TAKE THE VISIBILITY DOWN TO IFR FOR KRST AS THE QUICK MOVING
SNOW BAND COMES IN THIS EVENING. FOR NOW...WILL STAY WITH MVFR AT
KLSE BUT WILL GO SLIGHTLY LOWER THAN THE PREVIOUS FORECAST. THE
SNOW SHOULD END BEFORE SUNRISE FOR BOTH LOCATIONS WITH VFR
CONDITIONS QUICKLY RETURNING. ANOTHER SHORT WAVE WILL DROP OUT OF
CANADA SATURDAY...BUT THE FORCING AND MOISTURE FROM THIS WAVE
SHOULD STAY ACROSS THE GREAT LAKES WITH LITTLE IMPACT EXPECTED AT
EITHER TAF SITE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
205 PM CST FRI DEC 16 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...DAS
LONG TERM.... DAS
AVIATION..... 04
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
509 AM MST FRI DEC 16 2011
.AVIATION...12Z TAFS. THROUGH 16Z...AREAS OF IFR CEILINGS AND
VISIBILITIES IN FOG ACROSS FAR WESTERN CARBON COUNTY SOUTHWEST
OF RAWLINS...OTHERWISE VFR ELSEWHERE. BATCH OF SCATTERED TO
BROKEN MID LEVEL CLOUDS NEAR 10000 FEET AGL EAST OF A CHEYENNE TO
CHADRON LINE THROUGH 16Z...OTHERWISE FEW IF ANY CLOUDS. RUBIN
&&
.PREV DISCUSSION... /ISSUED 255 AM MST FRI DEC 16 2011/
SHORT TERM...FRIDAY THROUGH SUNDAY NIGHT
TRANQUIL CONDITIONS EXPECTED IN THE SHORT TERM WITH TEMPERATURES
BEING THE PRIMARY FORECAST CHALLENGE.
CURRENTLY...SPLIT FLOW OVER WYOMING THIS MORNING WITH AN UPPER
LEVEL SHORTWAVE TRACKING ACROSS MONTANA/DAKOTAS AND AN UPPER LEVEL
LOW PRESSURE SYSTEM MOVING INTO SOUTHERN CALIFORNIA. CLOUD BAND
WITH THE SOUTHERN EDGE OF THE SHORTWAVE OVER WYOMING HAS BEEN
SHEARING APART AND WARMING ON IR IMAGERY. MOSAIC RADAR SHOWING NO
PRECIPITATION ECHOES ANYWHERE OVER WYOMING OR NEBRASKA PANHANDLE.
FOR TODAY...SHORTWAVE CONTINUES TO SHEAR OUT AND PUSHES THROUGH
THE SOUTHERN PANHANDLE BY EARLY AFTERNOON. WE THEN WILL BE IN
NORTHWEST FLOW BEHIND THE SHORTWAVE. WORST CASE CONDITIONS WILL BE
MOSTLY CLOUDY SKIES THROUGH MUCH OF THE MORNING WITH GRADUAL
SCATTERING OUT BY LATE AFTERNOON. EXPECT HIGH TEMPERATURES IN THE
LOW 40S EAST OF THE LARAMIE RANGE WITH UPPER 20S WEST. SOME OF THE
HIGHER TERRAIN AREAS AND OUR WIND PRONE AREAS MAY SEE SOME GUSTY
WEST TO NORTHWEST WINDS...BUT WELL BELOW ANY HEADLINE CRITERIA.
700MB TEMPERATURES BEGIN TO WARM THIS EVENING INTO
SATURDAY...INCREASING FROM -9C THIS MORNING TO AROUND 0C SATURDAY
MORNING. AS A RESULT...LOOKS LIKE MODERATELY WARM HIGHS EXPECTED
FOR THE WEEKEND WITH 50 HIGHS IN THE PANHANDLE TO THE EASTERN
SLOPES OF THE LARAMIE RANGE...UPPER 30S WEST. BCCONSMOS GUIDANCE
SEEMS TO BE THE BEST PERFORMING ON TEMPERATURES THE PAST WEEK AND
HAVE BLENDED MORE TOWARDS THIS GUIDANCE WITH THE WARMER 700MB
TEMPERATURES. WARMEST DAY LOOKS TO BE SUNDAY AS 700MB TEMPERATURES
CLIMB TO +4C. MID TO UPPER 50S POSSIBLE IN THE
PANHANDLE...ESPECIALLY THE SOUTHERN PORTIONS NEAR SIDNEY. WINDS TO
BEGIN INCREASING SUNDAY AFTERNOON...POSSIBLY GUSTING INTO THE 40
MPH RANGE FOR OUR WIND PRONE AREAS. THESE STRONGER WINDS WILL ADD TO
DOWNSLOPE WARMING AND WE MAY NEED TO UP TEMPERATURES EVEN MORE OUT
IN THE PANHANDLE FOR SUNDAY AFTERNOON. BY SUNDAY EARLY EVENING...A
DRY COLD FRONT LOOKS TO MOVE THROUGH SOUTHEAST WYOMING....WITH MAIN
IMPACT BEING ON TEMPERATURES AS 700MB TEMPS FALL TO -6 TO -8C.
LONG TERM...MONDAY THROUGH THURSDAY. 500 MB SYNOPTIC PATTERNS
SIMILAR WITH THE 16/00Z GFS AND ECMWF RUNS...THOUGH THEY DIVERGE ON
THURSDAY. ON THURSDAY...16/00Z GFS TAKES ALL THE ENERGY WITH THE
SHORTWAVE TROUGH ALOFT INTO THE NORTHERN AND CENTRAL PLAINS STATES...
WHILE THE 16/00Z ECMWF KEEPS THE MAIN ENERGY WITH THE TROUGH ALOFT
BEGINNING TO CUT OFF OVER UTAH AND ARIZONA WITH THE WEAKER NORTHERN
PORTION OF THE TROUGH MOVING ACROSS THE NORTHERN PLAINS STATES.
SENSIBLE WEATHER FOR OUR COUNTIES WOULD CONTAIN MORE PRECIPITATION
AND CLOUDS FOR THURSDAY IF THE ECMWF SOLUTION VERIFIES CLOSER TO
REALITY VERSUS THE GFS SOLUTION.
MONDAY...CONSIDERABLY COLDER DAY TO START THE WEEK BEFORE CHRISTMAS
IN THE WAKE OF THE COLD FRONTAL PASSAGE. MAXIMUM TEMPERATURES IN THE
20S AND 30S WITH 1000-500 MB THICKNESSES NEAR 5310 METERS. FAIRLY
WIDESPREAD COVERAGE OF SNOW SHOWERS OVER THE NORTHERN LARAMIE...SNOWY
AND SIERRA MADRE RANGES IN THE MORNING THEN DECREASING SIGNIFICANTLY
IN THE AFTERNOON AS MOISTURE WANES. THOUGH POSITIVE TILT SHORTWAVE
TROUGH ALOFT MOVES ACROSS IN THE AFTERNOON...BULK OF THE
PRECIPITATION WILL BE OVER THE SOUTHERN PLAINS STATES CLOSER TO THE
PRIMARY UPPER TROUGH AND DEEPER MOISTURE.
TUESDAY...SLOW WARMING TREND AS NORTHWEST FLOW DEVELOPS...THOUGH
TEMPERED BY TIME OF YEAR CONSIDERATIONS AND LOW SUN ANGLE. DRY DUE
TO LACK OF LOW AND MID LEVEL MOISTURE AVAILABILITY. WILL SEE TYPICAL
WINDS INCREASE AS SURFACE THROUGH 700 MB GRADIENTS INCREASE...THOUGH
LOOKS LIKE WINDS WILL REMAIN UNDER HIGH WIND CRITERIA DUE TO PROGGED
700 MB GRADIENTS.
WEDNESDAY...NEXT PROGRESSIVE TROUGH ALOFT BEGINS CARVING ITSELF OUT
OVER IDAHO AND MONTANA SENDING AN ASSOCIATED COLD FRONT INTO
NORTHERN WYOMING BY LATE IN THE DAY. WILL SEE INCREASING MID AND
HIGH LEVEL CLOUDS ACROSS OUR COUNTIES IN ADVANCE OF THE SHORTWAVE
TROUGH ALOFT. MAXIMUM TEMPERATURES 20S AND 30S WEST IN THE HIGH
MOUNTAINS AND VALLEYS WHERE COLD AIR WILL REMAIN MOSTLY
TRAPPED...WITH UPPER 30S TO MID 40S EAST PER 1000-500 MB THICKNESSES
NEAR 5430 METERS AND SOME DOWNSLOPE KATABATIC WARMING.
THURSDAY...COLDER AGAIN IN THE WAKE OF THE RELATIVELY STRONG COLD
FRONTAL PASSAGE. MAXIMUM TEMPERATURES IN THE 20S AND 30S WITH
SURFACE HIGH PRESSURE SETTLING OVER WYOMING AND NEBRASKA AND
1000-500 MB THICKNESSES PROGGED NEAR 5250 METERS. LOOKS LIKE A
DECENT AREAL COVERAGE OF SNOW WITH THIS COLD FRONT AND SHORTWAVE
TROUGH ALOFT PASSAGE...THOUGH QPF WILL BE LIMITED DUE TO PROGRESSIVE
NATURE OF THE SHORTWAVE AND LIMITED LOW AND MID LEVEL MOISTURE. HAVE
PAINTED HIGHEST COVERAGE OF SNOW OVER OUR NORTHERN LARAMIE...SNOWY
AND SIERRA MADRE RANGES DUE TO OROGRAPHICS AND DYNAMICS WORKING IN
UNISON.
AVIATION...06Z TAF ISSUANCE...WEAK COLD FRONT MOVING THROUGH
CENTRAL WYOMING LATE THIS EVENING...PRECEDED BY MID/HIGH CLOUD
CEILINGS. BOTH THE 00Z NAM AND 02Z HRRR DATA INDICATE SOME
MVFR TO IFR CEILINGS AND PATCHY FOG DEVELOPING INTO SOUTHWEST
CARBON COUNTY OVERNIGHT...BUT SHOULD NOT IMPACT RAWLINS. WENT
WITH LOWEST CEILINGS AT 5000 FT AND WILL MONITOR TRENDS.
ELSEWHERE...EXPECT VFR CONDITIONS WITH VARIABLE TO SOUTHWEST
WINDS 5 TO 10 KT PRIOR TO THE FRONTAL PASSAGE. WINDS SHIFT TO
THE WEST TO NORTHWEST AFTER FROPA WITH SKIES CLEARING FROM WEST
TO EAST FRIDAY MORNING. IT WILL BECOME BREEZY WEST OF THE LARAMIE
RANGE WITH GUSTS OF 20 TO 25 KT.
FIRE WEATHER...DRY CONDITIONS EXPECTED TO CONTINUE THROUGH SUNDAY
WITH ABOVE NORMAL TEMPERATURES FOR HIGHS. AFTERNOON HUMIDITIES
EXPECTED TO FALL INTO THE LOW TO MID 20 PERCENT RANGE...WITH
EXCELLENT OVERNIGHT RECOVERIES. GUSTY WINDS EXPECTED TO DEVELOP
SUNDAY AHEAD OF A DRY COLD FRONT THAT IS EXPECTED TO MOVE THROUGH
SUNDAY EVENING.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...CLAYCOMB
LONG TERM/AVIATION...RUBIN
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
255 AM MST FRI DEC 16 2011
.SHORT TERM...FRIDAY THROUGH SUNDAY NIGHT
TRANQUIL CONDITIONS EXPECTED IN THE SHORT TERM WITH TEMPERATURES
BEING THE PRIMARY FORECAST CHALLENGE.
CURRENTLY...SPLIT FLOW OVER WYOMING THIS MORNING WITH AN UPPER
LEVEL SHORTWAVE TRACKING ACROSS MONTANA/DAKOTAS AND AN UPPER LEVEL
LOW PRESSURE SYSTEM MOVING INTO SOUTHERN CALIFORNIA. CLOUD BAND
WITH THE SOUTHERN EDGE OF THE SHORTWAVE OVER WYOMING HAS BEEN
SHEARING APART AND WARMING ON IR IMAGERY. MOSAIC RADAR SHOWING NO
PRECIPITATION ECHOES ANYWHERE OVER WYOMING OR NEBRASKA PANHANDLE.
FOR TODAY...SHORTWAVE CONTINUES TO SHEAR OUT AND PUSHES THROUGH
THE SOUTHERN PANHANDLE BY EARLY AFTERNOON. WE THEN WILL BE IN
NORTHWEST FLOW BEHIND THE SHORTWAVE. WORST CASE CONDITIONS WILL BE
MOSTLY CLOUDY SKIES THROUGH MUCH OF THE MORNING WITH GRADUAL
SCATTERING OUT BY LATE AFTERNOON. EXPECT HIGH TEMPERATURES IN THE
LOW 40S EAST OF THE LARAMIE RANGE WITH UPPER 20S WEST. SOME OF THE
HIGHER TERRAIN AREAS AND OUR WIND PRONE AREAS MAY SEE SOME GUSTY
WEST TO NORTHWEST WINDS...BUT WELL BELOW ANY HEADLINE CRITERIA.
700MB TEMPERATURES BEGIN TO WARM THIS EVENING INTO
SATURDAY...INCREASING FROM -9C THIS MORNING TO AROUND 0C SATURDAY
MORNING. AS A RESULT...LOOKS LIKE MODERATELY WARM HIGHS EXPECTED
FOR THE WEEKEND WITH 50 HIGHS IN THE PANHANDLE TO THE EASTERN
SLOPES OF THE LARAMIE RANGE...UPPER 30S WEST. BCCONSMOS GUIDANCE
SEEMS TO BE THE BEST PERFORMING ON TEMPERATURES THE PAST WEEK AND
HAVE BLENDED MORE TOWARDS THIS GUIDANCE WITH THE WARMER 700MB
TEMPERATURES. WARMEST DAY LOOKS TO BE SUNDAY AS 700MB TEMPERATURES
CLIMB TO +4C. MID TO UPPER 50S POSSIBLE IN THE
PANHANDLE...ESPECIALLY THE SOUTHERN PORTIONS NEAR SIDNEY. WINDS TO
BEGIN INCREASING SUNDAY AFTERNOON...POSSIBLY GUSTING INTO THE 40
MPH RANGE FOR OUR WIND PRONE AREAS. THESE STRONGER WINDS WILL ADD TO
DOWNSLOPE WARMING AND WE MAY NEED TO UP TEMPERATURES EVEN MORE OUT
IN THE PANHANDLE FOR SUNDAY AFTERNOON. BY SUNDAY EARLY EVENING...A
DRY COLD FRONT LOOKS TO MOVE THROUGH SOUTHEAST WYOMING....WITH MAIN
IMPACT BEING ON TEMPERATURES AS 700MB TEMPS FALL TO -6 TO -8C.
.LONG TERM...MONDAY THROUGH THURSDAY. 500 MB SYNOPTIC PATTERNS
SIMILAR WITH THE 16/00Z GFS AND ECMWF RUNS...THOUGH THEY DIVERGE ON
THURSDAY. ON THURSDAY...16/00Z GFS TAKES ALL THE ENERGY WITH THE
SHORTWAVE TROUGH ALOFT INTO THE NORTHERN AND CENTRAL PLAINS STATES...
WHILE THE 16/00Z ECMWF KEEPS THE MAIN ENERGY WITH THE TROUGH ALOFT
BEGINNING TO CUT OFF OVER UTAH AND ARIZONA WITH THE WEAKER NORTHERN
PORTION OF THE TROUGH MOVING ACROSS THE NORTHERN PLAINS STATES.
SENSIBLE WEATHER FOR OUR COUNTIES WOULD CONTAIN MORE PRECIPITATION
AND CLOUDS FOR THURSDAY IF THE ECMWF SOLUTION VERIFIES CLOSER TO
REALITY VERSUS THE GFS SOLUTION.
MONDAY...CONSIDERABLY COLDER DAY TO START THE WEEK BEFORE CHRISTMAS
IN THE WAKE OF THE COLD FRONTAL PASSAGE. MAXIMUM TEMPERATURES IN THE
20S AND 30S WITH 1000-500 MB THICKNESSES NEAR 5310 METERS. FAIRLY
WIDESPREAD COVERAGE OF SNOW SHOWERS OVER THE NORTHERN LARAMIE...SNOWY
AND SIERRA MADRE RANGES IN THE MORNING THEN DECREASING SIGNIFICANTLY
IN THE AFTERNOON AS MOISTURE WANES. THOUGH POSITIVE TILT SHORTWAVE
TROUGH ALOFT MOVES ACROSS IN THE AFTERNOON...BULK OF THE
PRECIPITATION WILL BE OVER THE SOUTHERN PLAINS STATES CLOSER TO THE
PRIMARY UPPER TROUGH AND DEEPER MOISTURE.
TUESDAY...SLOW WARMING TREND AS NORTHWEST FLOW DEVELOPS...THOUGH
TEMPERED BY TIME OF YEAR CONSIDERATIONS AND LOW SUN ANGLE. DRY DUE
TO LACK OF LOW AND MID LEVEL MOISTURE AVAILABILITY. WILL SEE TYPICAL
WINDS INCREASE AS SURFACE THROUGH 700 MB GRADIENTS INCREASE...THOUGH
LOOKS LIKE WINDS WILL REMAIN UNDER HIGH WIND CRITERIA DUE TO PROGGED
700 MB GRADIENTS.
WEDNESDAY...NEXT PROGRESSIVE TROUGH ALOFT BEGINS CARVING ITSELF OUT
OVER IDAHO AND MONTANA SENDING AN ASSOCIATED COLD FRONT INTO
NORTHERN WYOMING BY LATE IN THE DAY. WILL SEE INCREASING MID AND
HIGH LEVEL CLOUDS ACROSS OUR COUNTIES IN ADVANCE OF THE SHORTWAVE
TROUGH ALOFT. MAXIMUM TEMPERATURES 20S AND 30S WEST IN THE HIGH
MOUNTAINS AND VALLEYS WHERE COLD AIR WILL REMAIN MOSTLY
TRAPPED...WITH UPPER 30S TO MID 40S EAST PER 1000-500 MB THICKNESSES
NEAR 5430 METERS AND SOME DOWNSLOPE KATABATIC WARMING.
THURSDAY...COLDER AGAIN IN THE WAKE OF THE RELATIVELY STRONG COLD
FRONTAL PASSAGE. MAXIMUM TEMPERATURES IN THE 20S AND 30S WITH
SURFACE HIGH PRESSURE SETTLING OVER WYOMING AND NEBRASKA AND
1000-500 MB THICKNESSES PROGGED NEAR 5250 METERS. LOOKS LIKE A
DECENT AREAL COVERAGE OF SNOW WITH THIS COLD FRONT AND SHORTWAVE
TROUGH ALOFT PASSAGE...THOUGH QPF WILL BE LIMITED DUE TO PROGRESSIVE
NATURE OF THE SHORTWAVE AND LIMITED LOW AND MID LEVEL MOISTURE. HAVE
PAINTED HIGHEST COVERAGE OF SNOW OVER OUR NORTHERN LARAMIE...SNOWY
AND SIERRA MADRE RANGES DUE TO OROGRAPHICS AND DYNAMICS WORKING IN
UNISON.
&&
.AVIATION...06Z TAF ISSUANCE...WEAK COLD FRONT MOVING THROUGH
CENTRAL WYOMING LATE THIS EVENING...PRECEDED BY MID/HIGH CLOUD
CEILINGS. BOTH THE 00Z NAM AND 02Z HRRR DATA INDICATE SOME
MVFR TO IFR CEILINGS AND PATCHY FOG DEVELOPING INTO SOUTHWEST
CARBON COUNTY OVERNIGHT...BUT SHOULD NOT IMPACT RAWLINS. WENT
WITH LOWEST CEILINGS AT 5000 FT AND WILL MONITOR TRENDS.
ELSEWHERE...EXPECT VFR CONDITIONS WITH VARIABLE TO SOUTHWEST
WINDS 5 TO 10 KT PRIOR TO THE FRONTAL PASSAGE. WINDS SHIFT TO
THE WEST TO NORTHWEST AFTER FROPA WITH SKIES CLEARING FROM WEST
TO EAST FRIDAY MORNING. IT WILL BECOME BREEZY WEST OF THE LARAMIE
RANGE WITH GUSTS OF 20 TO 25 KT.
&&
.FIRE WEATHER...DRY CONDITIONS EXPECTED TO CONTINUE THROUGH SUNDAY
WITH ABOVE NORMAL TEMPERATURES FOR HIGHS. AFTERNOON HUMIDITIES
EXPECTED TO FALL INTO THE LOW TO MID 20 PERCENT RANGE...WITH
EXCELLENT OVERNIGHT RECOVERIES. GUSTY WINDS EXPECTED TO DEVELOP
SUNDAY AHEAD OF A DRY COLD FRONT THAT IS EXPECTED TO MOVE THROUGH
SUNDAY EVENING.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...CLAYCOMB
LONG TERM/AVIATION...RUBIN
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
1036 PM MST THU DEC 15 2011
.AVIATION...06Z TAF ISSUANCE...WEAK COLD FRONT MOVING THROUGH
CENTRAL WYOMING LATE THIS EVENING...PRECEDED BY MID/HIGH CLOUD
CEILINGS. BOTH THE 00Z NAM AND 02Z HRRR DATA INDICATE SOME
MVFR TO IFR CEILINGS AND PATCHY FOG DEVELOPING INTO SOUTHWEST
CARBON COUNTY OVERNIGHT...BUT SHOULD NOT IMPACT RAWLINS. WENT
WITH LOWEST CEILINGS AT 5000 FT AND WILL MONITOR TRENDS.
ELSEWHERE...EXPECT VFR CONDITIONS WITH VARIABLE TO SOUTHWEST
WINDS 5 TO 10 KT PRIOR TO THE FRONTAL PASSAGE. WINDS SHIFT TO
THE WEST TO NORTHWEST AFTER FROPA WITH SKIES CLEARING FROM WEST
TO EAST FRIDAY MORNING. IT WILL BECOME BREEZY WEST OF THE LARAMIE
RANGE WITH GUSTS OF 20 TO 25 KT.
&&
PREV DISCUSSION... /ISSUED 352 PM MST THU DEC 15 2011/
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT...QUIET WEATHER WILL
CONTINUE INTO THE WEEKEND WITH MODELS SHOWING SPLIT FLOW ACROSS
THE WESTERN UNITED STATES AS AN UPPER LEVEL RIDGE ATTEMPTS TO PUSH
EASTWARD FROM THE EASTERN PACIFIC. THIS WILL RESULT IN THE STORM
TRACK FAR TO THE NORTH OF WYOMING AND NEBRASKA...WITH THE NORTHERN
BRANCH OF THE JET STREAM RETREATING INTO CANADA. THE SOUTHERN
BRANCH WILL REMAIN ACROSS MEXICO AND THE GULF COAST STATES AS AN
UPPER LEVEL TROUGH CURRENTLY ACROSS ARIZONA WILL BECOME A CLOSED
LOW OVER NORTHERN MEXICO AND REMAIN NEARLY STATIONARY THROUGH
SATURDAY. THE NORTHERN AND CENTRAL ROCKIES WILL IN BETWEEN THIS
JET ENERGY AND WILL THEREFORE BE RELATIVELY QUIET WITH LITTLE IF
ANY IMPACT. ANOTHER WEAK UPPER LEVEL TROUGH CURRENTLY OVER MONTANA
WILL PUSH SOUTHEAST ACROSS WYOMING EARLY ON FRIDAY. NO
PRECIPITATION IS EXPECTED WITH A WIND SHIFT INTO THE NORTHWEST THE
ONLY IMPACT FROM THIS DISTURBANCE. LOW STRATUS CLOUDS AND PATCHY
FOG IS POSSIBLE ACROSS FAR SOUTHWEST CARBON COUNTY TONIGHT...SO
ADDED PATCHY FOG TO THE FORECAST SOUTH OF RAWLINS.
OTHERWISE...TEMPERATURES WILL BE NEAR OR SLIGHTLY BELOW NORMAL
THROUGH FRIDAY AS THE UPPER LEVEL TROUGH MOVES THROUGH THE
AREA...BUT WILL THEN MODERATE INTO THIS WEEKEND WITH HIGHS IN THE
UPPER 30S TO UPPER 40S ACROSS MOST OF THE AREA FOR SATURDAY. A FEW
LOCATIONS IN FAR SOUTHEAST WYOMING AND WESTERN NEBRASKA MAY SEE 50
FOR A HIGH AS WINDS SHIFT INTO THE WEST. LOW TEMPERATURES WILL BE
SEASONABLY COLD FOR THIS TIME OF THE YEAR WITH CLEAR SKIES AND
LIGHT WINDS.
LONG TERM...SUNDAY THROUGH THURSDAY...
PERSISTENT ZONAL JET WILL REMAIN ENTRENCHED UPSTREAM OVER THE
CENTRAL PACIFIC. THIS WILL MAINTAIN THE SPLIT FLOW PATTERN ACROSS
THE WESTERN CONUS THROUGH THE EXTENDED PERIOD. INITIALLY THE
CLOSED LOW NEAR THE BAJA OF CALIFORNIA WILL BEGIN TO LIFT
EAST/NORTHEAST ACROSS SOUTHERN ARIZONA/NEW MEXICO ON SUNDAY. THE
BRUNT OF THIS ENERGY WILL BE CONFINED SOUTH OF THE CWA.
MEANWHILE...A NRN STREAM SHORTWAVE WILL DRAG A MAINLY DRY SURFACE
COLD FRONT THROUGH THE REGION MONDAY NIGHT. THERE MAY BE A FEW
ISOLATED MOUNTAIN SNOW SHOWERS LATE SUNDAY NIGHT/EARLY MONDAY. ANY
ACCUMULATION FROM THIS ACTIVITY WILL REMAIN VERY LIGHT. SPLIT
FLOW WILL CONTINUE THROUGH THE MIDDLE OF NEXT WEEK...WITH A
ANOTHER CLOSED LOW TO BECOME CUT-OFF NR THE BAJA OF CALIFORNIA.
MEDIUM RANGE GUIDANCE HINT AT ANOTHER SHORTWAVE EMBEDDED WITHIN
THE NRN STREAM TO DROP SOUTHEAST THROUGH THE NRN ROCKIES TOWARDS
THE MIDDLE/END OF NEXT WEEK. MEDIUM RANGE GUIDANCE HAS TRENDED
SLOWER WITH THIS FEATURE CLOSING IT OFF NR THE GREAT BASIN. SO FOR NOW
HAVE LEFT THE GOING FORECAST DRY. AFTER AN ABOVE NORMAL DAY
TEMPERATURE WISE ON SUNDAY...TEMPERATURES WILL DROP BACK TO MORE
SEASONAL READINGS NEXT WEEK.
&&
FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH THE END OF THE
WEEK AND INTO THE WEEKEND. WINDS WILL CONTINUE TO BE RELATIVELY
LIGHT ACROSS THE AREA WITH MODERATE DAYTIME HUMIDITIES BETWEEN 30
TO 50 PERCENT.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...RJM
LONG TERM...HAHN
AVIATION...JAMSKI
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
319 AM CST SUN DEC 18 2011
.DISCUSSION...
849 PM CST
FORECAST CONCERNS/CHALLENGES ARE WITH SKY COVER TONIGHT...AS I AM
LITTLE CONCERNED CLOUD COVER MAY LINGER A LITTLE BIT LONGER THAN
PREVIOUSLY THOUGHT...AS WELL AS FOG DEVELOPMENT.
LARGE SCALE TROUGH WILL CONTINUE TO PUSH EAST TONIGHT WITH
ATTENDANT TROUGH OF LOW PRESSURE TO THE NORTH QUICKLY SHIFTING
EAST THROUGH NORTHERN MICHIGAN. MEANWHILE ACROSS THE CWA...SURFACE
RIDGE AXIS WILL SHIFT OVERHEAD WITH WINDS BECOMING MORE LIGHT AND
VARIABLE. ALTHOUGH...WEAK RIDGING ALOFT COINCIDING WITH A WAVE
SHIFTING SOUTHEAST ACROSS CANADA WILL ALLOW LOW/MID LEVEL WINDS TO
BACK MORE TO THE WEST/SOUTHWEST...WITH LATEST RUC ANALYSIS ALREADY
SHOWING THIS BEGINNING TO OCCUR. THIS IS THE START OF A PERIOD OF
WAA ACROSS MUCH OF THE REGION. ITS THIS WAA/WEAK FORCING RIDING
OVER A MOIST BOUNDARY LAYER FROM HIGHER DEWPOINT AIR AS WELL AS
THE RECENT SNOW...WHICH COULD HELP PROVIDE THE REDEVELOPMENT OF
LOW CEILINGS TONIGHT. CLEARING CURRENTLY ONGOING ACROSS A PORTION
OF NORTHERN ILLINOIS AND NORTHWEST INDIANA MAY INITIALLY BE
HINDERED BY THE LARGE CLOUD SHIELD SHIFTING EAST/SOUTHEAST ACROSS
MUCH OF WISCONSIN. THIS CLOUD SHIELD HAS SHOWN MORE OF A SOUTHERLY
PUSH RECENTLY AND THINK THAT IT WILL LINGER INTO NORTHEAST
ILLINOIS AND NORTHWEST ILLINOIS OVER THE NEXT COUPLE OF HOURS
BEFORE IT COMPLETELY EXITS TO THE EAST. ALTHOUGH...ITS DURING THIS
CLEARING TREND THAT THE REDEVELOPMENT OF LOW CEILINGS/FOG WILL BE
POSSIBLE ACROSS MOST OF THE CWA. THIS CLEARING AND LIGHTER WINDS
IN PLACE WILL ALLOW FOR GOOD RADIATIONAL COOLING TO
CONTINUE...WITH SEVERAL SITES ALREADY SHOWING RAPID TEMPERATURE
DROPS THIS EVENING.
WITH THESE CONCERNS IN MIND...THE RUC/VSREF HAVE BEEN HINTING AT
THE POSSIBILITY OF LOW CEILINGS/VIS WITH LOCATIONS NEAR
DEKALB/ROCHELL ALREADY SHOWING THESE TRENDS. ALTHOUGH AREAS OF FOG
WILL CONTINUE TO DEVELOP TONIGHT WITH SOME SITES OBSERVING VIS
AROUND THE 1-2SM RANGE...DONT THINK VIS WILL REMAIN THIS LOW WITH
STRATUS THEN DEVELOPING. LATEST GUIDANCE CONTINUES TO SHOW THAT
THERE WILL BE ENOUGH MOMENTUM IN THE BOUNDARY LAYER TO FAVOR
STRATUS.
THERE IS STILL UNCERTAINTY WITH SKY COVER TONIGHT...BUT HAVE
TRENDED MORE PESSIMISTIC IN THE GRIDS AND HAVE STARTED THE TREND
TOWARDS MORE CLOUDY SKIES BY SUNDAY MORNING. WILL LEAVE PARTLY
CLOUDY SKIES LATE TONIGHT BUT WILL HAVE TO CONTINUE TO MONITOR
LATEST TRENDS AND ADJUST ACCORDINGLY. HAVE ONLY MADE SOME MINOR
TEMP ADJUSTMENTS TONIGHT...MAINLY TO ACCOUNT FOR THE RAPID COOLING
IN AREAS WHICH HAVE ALREADY OBSERVED CLEAR SKIES.
RODRIGUEZ
//PREV DISCUSSION...
350 PM
LATE AFTERNOON THROUGH MONDAY...
AT MID AFTERNOON ANOTHER SHORT WAVE TROUGH MOVING EAST-SOUTHEAST
ACROSS LAKE SUPERIOR AND THE U.P. OF MI...TRAILING RIGHT BEHIND
THE SHORT WAVE...CURRENTLY OVER THE SOUTH CENTRAL GREAT LAKES
REGION...THAT GAVE AN INCH OR TWO TO MUCH OF OF SNOW TO MUCH OF
NORTH CENTRAL AND FAR NORTHEAST IL LATE LAST NIGHT AND THIS
MORNING...WITH LESSER AMOUNTS FURTHER SOUTH. THIS SECOND SHORT
WAVE WILL TRACK TOO FAR TO OUR NORTH AND NORTHEAST TO THREATEN
THE LOCAL AREA WITH ANY ADDITIONAL LIGHT SNOWFALL TONIGHT.
WIDESPREAD STRATOCUMULUS EXTENDS FROM IND NORTHWESTWARD ACROSS
EAST CENTRAL AND NORTHERN IL...ALL OF WI AND THE SOUTHEAST CORNER
OF MN. WHILE MODEL FORECAST TEMPERATURE AND DEW POINT DEPRESSION
PROFILES AS WELL AS PLAN DISPLAYS OF LOWER LEVEL RH FIELDS SHOW
THESE CLOUDS GRADUALLY CLEARING WEST TO E DURING THE LATE EVENING
AND EARLY A.M. HOURS THIS APPEARS TO BE A BIT FAST AND DO NOT
EXPECT TO SEE SIGNIFICANT CLEARING OVER THE EASTERN PORTIONS OF
THE FORECAST AREA UNTIL THE PRE-DAWN HOURS WHEN THE SECOND SHORT
WAVE TROUGH REACHES THE CENTRAL GREAT LAKES AND A SURFACE RIDGE
SHIFTS EAST ACROSS THE MS RIVER AND OVER THE LOCAL AREA BY 12Z
SUN.
RIDGING ALOFT SPREADS EAST FROM THE NORTHERN PLAINS TO OVER THE
UPPER MIDWEST AND THE LOCAL FORECAST AREA DURING SUNDAY MORNING
BETWEEN THE DEPARTING GREAT LAKES TROUGH AND ANOTHER SHORT WAVE
DIGGING SOUTHEAST OVER ALBERTA AND NORTHERN SASKATCHEWAN. RIDGING
SURFACE AND ALOFT ALONG WITH LOWER LEVEL WINDS BACKING TO SOUTH-
SOUTHWEST AND SOUTHWEST SUNDAY EXPECTED TO BE MOSTLY SUNNY AND
MILD FOR MID DECEMBER WITH TEMPERATURES UP INTO THE LOWER AND
MID 40S FOR THE AFTERNOON. A COLD FRONT EXTENDING FROM A SURFACE
LOW ASSOCIATED WITH THE SECOND SHORT WAVE SWEEPS ACROSS THE
REGION MONDAY NIGHT RETURNING COLDER AIR BUT TEMPERATURES STILL
EXPECTED TO BE FROM AROUND TO A BIT ABOVE NORMALS FOR THE DATE.
TUESDAY THROUGH SATURDAY...
THOUGHTS TURN TO HOLIDAY TRAVEL PLANS FOR NEXT WEEK. AT THIS
POINT LOOKS TO BE PRETTY GOOD CONDITIONS FOR THE AREA AS NO MAJOR
WINTER WEATHER IS EXPECTED.
OVERALL THEME OF MODEL RUNS FROM LAST NIGHT WAS THE IDEA OF LESS
PHASING OF THE CUT-OFF UPPER LOW TO BE OVER THE AZ/MEXICO BORDER
LATE SUNDAY AND A NORTHERN JET STREAM SHORT WAVE MOVING FROM
SOUTHERN B.C. AND THE PACIFIC NORTHWEST SOUTHEASTWARD TO THE
NORTHERN PLAINS...AND THEN EASTWARD ACROSS THE NORTHERN PLAINS
AND THE UPPER MIDWEST...FINALLY REACHING THE WESTERN GREAT LAKES
TUESDAY EVENING. MODEL RUNS FROM THIS MORNING AND MIDDAY
INCLUDING INDIVIDUAL ENSEMBLE MEMBERS MAINTAIN THEIR MEMBER TO
MEMBER...RUN TO RUN...AND MODEL TO MODEL AGREEMENT LEADING TO A
MORE SINGULAR SOLUTION. HOPEFULLY THIS WILL TURN OUT TO BE A
DECENT SOLUTION IF NOT THE BEST.
THIS MORE UNIFIED SOLUTION HAS THE CUT-OFF CLOSED UPPER
LOW...WHICH TAKES UP RESIDENCE OVER OR JUST WEST OF THE NORTHERN
BAJA PENINSULA TONIGHT INTO SATURDAY STARTING TO BE EJECTED BY A
DISTURBANCE DROPPING SOUTH-SOUTHEAST FROM THE GULF OF AK ALONG THE
PACIFIC COAST LATE SUNDAY THROUGH MONDAY. IN RESPONSE THE UPPER
LOW LIFTS NORTHEASTWARD OVER THE CENTRAL PLAINS TUESDAY AND THEN
GRADUALLY OPENS TO AN OPEN WAVE BY LATE WED AS IT CROSSES THE MID
MS VALLEY.
AS THE UPPER LOW/OPEN WAVE MOVES FROM THE EASTERN CENTRAL PLAINS
ACROSS THE MID MS VALLEY AND THE LOWER OH VALLEY LATE TUESDAY
NIGHT THROUGH WEDNESDAY IT WILL BASICALLY BE TRACKING TO THE EAST.
THIS KEEPS THE MAX PRECIP AXIS FROM MO EAST ACROSS SOUTHERN AND
CENTRAL IL AND THEN ACROSS IND...SOUTH OF THE LOCAL FORECAST AREA.
WHILE NORTHERN EDGE OF THE PRECIPITATION SHIELD IS EXPECTED TO
GRADUALLY CREEP FAR ENOUGH NORTHWARD TO GIVE AT LEAST CHANCE
THREAT OF PRECIPITATION FROM LATER MONDAY THROUGH WEDNESDAY.
PRECIPITATION STILL LOOKS TO BE RAIN WITH ONLY A VERY SMALL
THREAT OF MIXED RAIN AND SNOW OR LIGHT SNOW ACROSS THE FAR NORTH
COUNTIES TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE
PRECIPITATION IS MOVING OFF TO THE EAST. LIQUID FORM FAVORED AS
SIGNIFICANT COLD AIR IS HELD AT BAY WITH QUICK PROGRESSION OF
DISTURBANCES MOVING THROUGH THE NORTHERN STREAM NOT PERMITTING
ANY STRONG COLD AIR ADVECTION TO OCCUR BEFORE FLOW BACKS AS THE
NEXT SHORT WAVE APPROACHES.
A RATHER SIGNIFICANT SHORT WAVE IS PROGGED TO DROP ACROSS THE
UPPER MIDWEST...UPPER AND MOD MO VALLEY...AND THE UPPER GREAT
LAKES WEDNESDAY NIGHT...MOVING TO OVER THE CENTRAL GREAT LAKES
BY MIDDAY FRIDAY. HOWEVER...DURING THIS TIME MODELS CONTINUE TO
SHOW A VERY LARGE STRONG ANTICYCLONE SPRAWLED FROM TX TO THE OH
VALLEY AND SOUTHERN GREAT LAKES. THIS WILL KEEP ANY SIGNIFICANT
AWAY FROM THE REGION WITH ONLY A POTENTIAL OF MAINLY LAKE EFFECT
SNOWS DOWNWIND OF THE LAKES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* TIMING DEPARTURE OF CURRENT MVFR STRATUS.
* POTENTIAL FOR IFR/LIFR FOG/STRATUS DEVELOPMENT TOWARD DAYBREAK
ONCE CURRENT MVFR STRATUS CLEARS.
* LIGHT WEST-SOUTHWEST WINDS OVERNIGHT BECOMING SOUTHWEST AND
GUSTING 15-20 KTS SUNDAY AFTERNOON/EVENING.
MDB
//DISCUSSION...UPDATED 09Z...
MAIN BAND OF MVFR STRATUS CONTINUES TO MOVE EASTWARD AWAY FROM THE
AREA BUT A PORTION OF THE WESTERN FLANK HAS BROKEN OFF AN STARTED
MOVING SOUTHWEST ACROSS ORD/DPA/MDW. EXPECT THAT THIS BAND WILL
SCATTER OUT BUT CONFIDENCE IN HOW QUICKLY THIS WILL OCCUR IS NOT
TERRIBLY HIGH. NEXT CONCERN IS POTENTIAL FOR FOG AND NEW STRATUS
TO DEVELOP CLOSER TO DAYBREAK ONCE THE CURRENT MVFR STRATUS
SCATTERS. BAND OF CIRRUS IS NOW STREAMING IN FROM THE NORTHWEST
BUT BASED ON SATELLITE TRENDS THE COVERAGE WILL QUICKLY DECREASE
CLOSER TO DAYBREAK. OBS TO THE WEST SHOW A MIX OF CONDITIONS WITH
POCKETS OF IFR AND LOWER SHOWING UP IN SPOTS BUT MUCH OF THIS HAD
BEGUN DEVELOPING PRIOR TO THE ARRIVAL OF THE CIRRUS. WILL
CONTINUE WITH MENTION OF IFR AND LOWER VSBY/CIGS BUT SLOW THE
ARRIVAL DOWN ACROSS THE CHICAGO METRO TERMINALS THOUGH THIS MAY BE
TOO PESSIMISTIC SO WILL NEED TO CONTINUE TO MONITOR.
MDB
FROM 06Z...
UPPER-LEVEL DISTURBANCE PULLING EAST OF THE FORECAST AREA LATE
THIS EVENING...WITH CLEARING SKIES SPREADING QUICKLY EAST AS
SUBSIDENCE DEVELOPS BEHIND DEPARTING UPPER TROUGH. EXTRAPOLATION
FROM SATELLITE IMAGERY INDICATES MVFR CIGS WILL CLEAR ORD/MDW
SHORTLY AFTER 06Z AND CLEAR GYY BY 0730Z. QUESTION REMAINS THE
POTENTIAL FOR FOG/LOW STRATUS DEVELOPMENT ACROSS NORTHERN IL AS
SKIES CLEAR AND TEMPERATURES DROP. RPJ/RFD/DKB DISPLAYED QUICK
TEMP DROPS AND FOG/STRATUS DEVELOPMENT EARLIER IN THE EVENING
BEFORE MVFR DECK SPREAD BACK ACROSS THOSE SITES...AND CONCERN IS
THAT SIMILAR TREND WILL OCCUR WITH CLEARING IN NEXT FEW HOURS. 00Z
MODEL SOUNDINGS CONTINUE TO DEPICT VERY SHALLOW BOUNDARY LAYER
SATURATING AT BOTH KRFD/KDPA...SUGGESTING FOG AND PERHAPS IFR OR
EVEN LIFR CEILING DEVELOPMENT. WHILE CONFIDENCE THAT VISIBILITY
WILL LOWER INTO MVFR RANGE IN MANY PLACES...VERY LOW CONFIDENCE
REMAINS WITH COVERAGE OF WHAT MAY BE PATCHY IFR/LIFR CONDITIONS.
HAVE MAINTAINED THE MIDDLE OF THE ROAD THINKING FROM 03Z
AMENDMENTS WITH TEMPO IFR CONDITIONS EARLY SUNDAY MORNING. IF MORE
EXTENSIVE IFR/LIFR DOES DEVELOP...IT MAY TAKE UNTIL 15-16Z BEFORE
STRATUS IS ABLE TO MIX OUT GIVEN RELATIVELY LATE SUNRISE ON NEARLY
THE SHORTEST DAY OF THE YEAR.
IMPROVEMENT TO VFR CONDITIONS IS EXPECTED BY MID-LATE MORNING
HOWEVER...EARLIER IF WIDESPREAD IFR DOES NOT DEVELOP. LOW PRESSURE
MOVING ACROSS CANADA WILL HELP TO TIGHTEN THE PRESSURE GRADIENT
ACROSS THE MIDWEST...WITH SOUTHWEST WINDS INCREASING AND BECOMING
GUSTY IN THE 15-20 KT RANGE IN THE AFTERNOON AND PERHAPS A FEW KTS
HIGHER AT KRFD. WILL LIKELY LOSE HIGHER GUSTS WITH SUNSET BUT
MAINTAIN SUSTAINED WINDS IN THE 10-15 KT RANGE.
LOW LEVEL MOISTURE INCREASES SUNDAY NIGHT AS FAIRLY STRONG WARM
ADVECTION CONTINUES...AND WILL LIKELY SEE VFR CEILINGS DEVELOPING
OVERNIGHT.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* MEDIUM CONFIDENCE IN TIMING OF DEPARTURE OF CURRENT MVFR STRATUS.
* MEDIUM-HIGH CONFIDENCE IN PATCHY IFR FOG/STRATUS DEVELOPING ONCE
STRATUS CLEARS... BUT LOW CONFIDENCE ON DIRECT IMPACT AT ORD/MDW
TERMINALS.
* HIGH CONFIDENCE IN VFR CONDITIONS SUNDAY AFTER ANY MORNING
FOG/STRATUS DISSIPATES.
* HIGH CONFIDENCE IN WIND TRENDS.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN...PSBLY MIXED WITH SNOW AT
ONSET TUES. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
RATZER
&&
.MARINE...
315 AM CST
...SOUTHWEST GALES DEVELOP THIS AFTERNOON...
A SERIES OF RIDGES AND TROUGHS DOT THE EARLY MORNING WEATHER MAP.
HIGH PRESSURE EXTENDS FROM EASTERN QUEBEC INTO NORTHERN NEW ENGLAND
AND IS WORKING TOWARDS THE ATLANTIC WHILE LOW PRESSURE OVER HUDSON
BAY MOVES EASTWARD DRAGGING A TROUGH ACROSS LAKE HURON AND SOUTHERN
ONTARIO. WEAK RIDGING IS POSITIONED TO THE WEST OF THE TROUGH AND
WILL CREST OVER LAKE MICHIGAN THIS MORNING. THE MOST NOTABLE FEATURE
IS LOW PRESSURE MOVING FROM CENTRAL SASKATCHEWAN INTO CENTRAL
MANITOBA. THIS LOW WILL DEEPEN AS IT MOVES EAST TODAY TIGHTENING THE
PRESSURE GRADIENT ACROSS THE UPPER LAKES THIS AFTERNOON. THE LOW WILL
DRAG A TROUGH ACROSS THE LAKE EARLY MONDAY MORNING WHICH WILL SHIFT
WINDS TO NORTHWESTERLY. IN TERMS OF TRENDS...WINDS WILL BEGIN TO
SLACKEN SOMEWHAT THIS MORNING AS THE RIDGE MOVES ACROSS BUT THEN
QUICKLY PICK UP FROM THE SOUTHWEST THIS AFTERNOON AS THE DEEPENING
LOW MOVES INTO WESTERN ONTARIO AND JUST NORTH OF LAKE SUPERIOR BY
EVENING. AM EXPECTING SPEEDS TO REACH GALE FORCE TO 40 KT BY LATE
AFTERNOON NORTH AND CONTINUE THROUGH THE EVENING THEN SLOWLY BEGIN
TO DIMINISH TO 35 KT GALES AFTER MIDNIGHT WITH A REDUCTION TO
BELOW GALE TOWARD DAYBREAK. STRONGEST SPEEDS WILL BE ACROSS THE
NORTHERN HALF TO TWO-THIRDS OF THE LAKE WITH SPEEDS A FEW KNOTS
LOWER AND SLIGHTLY SLOWER IN ARRIVING ACROSS THE SOUTH. SPEEDS
WILL LIKELY REMAIN IN THE 20 TO 25 KT RANGE FOR MOST OF MONDAY AS
THE PRESSURE GRADIENT REMAINS STRONG BETWEEN THE DEPARTING LOW AND
A STRONG HIGH THAT WILL BE MOVING IN FROM THE WEST. WINDS WILL
TURN TO THE NORTH BY AFTERNOON THEN PROBABLY TURN MORE NORTHEAST
AS SPEEDS DROP OFF MONDAY EVENING AS THE HIGH REACHES THE LAKE.
LOW PRESSURE WILL DEVELOP ACROSS NORTHERN TEXAS MONDAY NIGHT AND
LIFT NORTHEASTWARD INTO EAST-CENTRAL ILLINOIS TUESDAY NIGHT WHILE
ANOTHER LOW MOVES ACROSS HUDSON BAY. RIDGING WILL REMAIN ACROSS THE
LAKE BUT THE NORTHERN SYSTEM LOOKS TO PASS CLOSE ENOUGH TO BRING
INCREASING SOUTH TO SOUTHWEST WINDS ACROSS THE FAR NORTHERN PART OF
THE LAKE TUESDAY AFTERNOON. THE GRADIENT WILL REMAIN WEAKER SOUTH
BUT A MORE SOUTHEASTERLY WIND DIRECTION SHOULD PREVAIL AHEAD OF THE
APPROACHING LOW. THE LOW WILL LIKELY PASS JUST TO THE SOUTHEAST OF
THE LAKE WEDNESDAY ALLOWING WINDS TO TURN NORTH OR NORTHEAST BEFORE
TURNING NORTHWEST WEDNESDAY EVENING. THE PATTERN REMAINS ACTIVE FROM
THAT POINT ONWARD WITH A SERIES OF HIGHS AND LOWS BRINGING UPS AND
DOWNS TO THE WIND SPEED FORECAST INTO NEXT WEEKEND.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1053 PM CST SAT DEC 17 2011
.DISCUSSION...
849 PM CST
FORECAST CONCERNS/CHALLENGES ARE WITH SKY COVER TONIGHT...AS I AM
LITTLE CONCERNED CLOUD COVER MAY LINGER A LITTLE BIT LONGER THAN
PREVIOUSLY THOUGHT...AS WELL AS FOG DEVELOPMENT.
LARGE SCALE TROUGH WILL CONTINUE TO PUSH EAST TONIGHT WITH
ATTENDANT TROUGH OF LOW PRESSURE TO THE NORTH QUICKLY SHIFTING
EAST THROUGH NORTHERN MICHIGAN. MEANWHILE ACROSS THE CWA...SURFACE
RIDGE AXIS WILL SHIFT OVERHEAD WITH WINDS BECOMING MORE LIGHT AND
VARIABLE. ALTHOUGH...WEAK RIDGING ALOFT COINCIDING WITH A WAVE
SHIFTING SOUTHEAST ACROSS CANADA WILL ALLOW LOW/MID LEVEL WINDS TO
BACK MORE TO THE WEST/SOUTHWEST...WITH LATEST RUC ANALYSIS ALREADY
SHOWING THIS BEGINNING TO OCCUR. THIS IS THE START OF A PERIOD OF
WAA ACROSS MUCH OF THE REGION. ITS THIS WAA/WEAK FORCING RIDING
OVER A MOIST BOUNDARY LAYER FROM HIGHER DEWPOINT AIR AS WELL AS
THE RECENT SNOW...WHICH COULD HELP PROVIDE THE REDEVELOPMENT OF
LOW CEILINGS TONIGHT. CLEARING CURRENTLY ONGOING ACROSS A PORTION
OF NORTHERN ILLINOIS AND NORTHWEST INDIANA MAY INITIALLY BE
HINDERED BY THE LARGE CLOUD SHIELD SHIFTING EAST/SOUTHEAST ACROSS
MUCH OF WISCONSIN. THIS CLOUD SHIELD HAS SHOWN MORE OF A SOUTHERLY
PUSH RECENTLY AND THINK THAT IT WILL LINGER INTO NORTHEAST
ILLINOIS AND NORTHWEST ILLINOIS OVER THE NEXT COUPLE OF HOURS
BEFORE IT COMPLETELY EXITS TO THE EAST. ALTHOUGH...ITS DURING THIS
CLEARING TREND THAT THE REDEVELOPMENT OF LOW CEILINGS/FOG WILL BE
POSSIBLE ACROSS MOST OF THE CWA. THIS CLEARING AND LIGHTER WINDS
IN PLACE WILL ALLOW FOR GOOD RADIATIONAL COOLING TO
CONTINUE...WITH SEVERAL SITES ALREADY SHOWING RAPID TEMPERATURE
DROPS THIS EVENING.
WITH THESE CONCERNS IN MIND...THE RUC/VSREF HAVE BEEN HINTING AT
THE POSSIBILITY OF LOW CEILINGS/VIS WITH LOCATIONS NEAR
DEKALB/ROCHELL ALREADY SHOWING THESE TRENDS. ALTHOUGH AREAS OF FOG
WILL CONTINUE TO DEVELOP TONIGHT WITH SOME SITES OBSERVING VIS
AROUND THE 1-2SM RANGE...DONT THINK VIS WILL REMAIN THIS LOW WITH
STRATUS THEN DEVELOPING. LATEST GUIDANCE CONTINUES TO SHOW THAT
THERE WILL BE ENOUGH MOMENTUM IN THE BOUNDARY LAYER TO FAVOR
STRATUS.
THERE IS STILL UNCERTAINTY WITH SKY COVER TONIGHT...BUT HAVE
TRENDED MORE PESSIMISTIC IN THE GRIDS AND HAVE STARTED THE TREND
TOWARDS MORE CLOUDY SKIES BY SUNDAY MORNING. WILL LEAVE PARTLY
CLOUDY SKIES LATE TONIGHT BUT WILL HAVE TO CONTINUE TO MONITOR
LATEST TRENDS AND ADJUST ACCORDINGLY. HAVE ONLY MADE SOME MINOR
TEMP ADJUSTMENTS TONIGHT...MAINLY TO ACCOUNT FOR THE RAPID COOLING
IN AREAS WHICH HAVE ALREADY OBSERVED CLEAR SKIES.
RODRIGUEZ
//PREV DISCUSSION...
350 PM
LATE AFTERNOON THROUGH MONDAY...
AT MID AFTERNOON ANOTHER SHORT WAVE TROUGH MOVING EAST-SOUTHEAST
ACROSS LAKE SUPERIOR AND THE U.P. OF MI...TRAILING RIGHT BEHIND
THE SHORT WAVE...CURRENTLY OVER THE SOUTH CENTRAL GREAT LAKES
REGION...THAT GAVE AN INCH OR TWO TO MUCH OF OF SNOW TO MUCH OF
NORTH CENTRAL AND FAR NORTHEAST IL LATE LAST NIGHT AND THIS
MORNING...WITH LESSER AMOUNTS FURTHER SOUTH. THIS SECOND SHORT
WAVE WILL TRACK TOO FAR TO OUR NORTH AND NORTHEAST TO THREATEN
THE LOCAL AREA WITH ANY ADDITIONAL LIGHT SNOWFALL TONIGHT.
WIDESPREAD STRATOCUMULUS EXTENDS FROM IND NORTHWESTWARD ACROSS
EAST CENTRAL AND NORTHERN IL...ALL OF WI AND THE SOUTHEAST CORNER
OF MN. WHILE MODEL FORECAST TEMPERATURE AND DEW POINT DEPRESSION
PROFILES AS WELL AS PLAN DISPLAYS OF LOWER LEVEL RH FIELDS SHOW
THESE CLOUDS GRADUALLY CLEARING WEST TO E DURING THE LATE EVENING
AND EARLY A.M. HOURS THIS APPEARS TO BE A BIT FAST AND DO NOT
EXPECT TO SEE SIGNIFICANT CLEARING OVER THE EASTERN PORTIONS OF
THE FORECAST AREA UNTIL THE PRE-DAWN HOURS WHEN THE SECOND SHORT
WAVE TROUGH REACHES THE CENTRAL GREAT LAKES AND A SURFACE RIDGE
SHIFTS EAST ACROSS THE MS RIVER AND OVER THE LOCAL AREA BY 12Z
SUN.
RIDGING ALOFT SPREADS EAST FROM THE NORTHERN PLAINS TO OVER THE
UPPER MIDWEST AND THE LOCAL FORECAST AREA DURING SUNDAY MORNING
BETWEEN THE DEPARTING GREAT LAKES TROUGH AND ANOTHER SHORT WAVE
DIGGING SOUTHEAST OVER ALBERTA AND NORTHERN SASKATCHEWAN. RIDGING
SURFACE AND ALOFT ALONG WITH LOWER LEVEL WINDS BACKING TO SOUTH-
SOUTHWEST AND SOUTHWEST SUNDAY EXPECTED TO BE MOSTLY SUNNY AND
MILD FOR MID DECEMBER WITH TEMPERATURES UP INTO THE LOWER AND
MID 40S FOR THE AFTERNOON. A COLD FRONT EXTENDING FROM A SURFACE
LOW ASSOCIATED WITH THE SECOND SHORT WAVE SWEEPS ACROSS THE
REGION MONDAY NIGHT RETURNING COLDER AIR BUT TEMPERATURES STILL
EXPECTED TO BE FROM AROUND TO A BIT ABOVE NORMALS FOR THE DATE.
TUESDAY THROUGH SATURDAY...
THOUGHTS TURN TO HOLIDAY TRAVEL PLANS FOR NEXT WEEK. AT THIS
POINT LOOKS TO BE PRETTY GOOD CONDITIONS FOR THE AREA AS NO MAJOR
WINTER WEATHER IS EXPECTED.
OVERALL THEME OF MODEL RUNS FROM LAST NIGHT WAS THE IDEA OF LESS
PHASING OF THE CUT-OFF UPPER LOW TO BE OVER THE AZ/MEXICO BORDER
LATE SUNDAY AND A NORTHERN JET STREAM SHORT WAVE MOVING FROM
SOUTHERN B.C. AND THE PACIFIC NORTHWEST SOUTHEASTWARD TO THE
NORTHERN PLAINS...AND THEN EASTWARD ACROSS THE NORTHERN PLAINS
AND THE UPPER MIDWEST...FINALLY REACHING THE WESTERN GREAT LAKES
TUESDAY EVENING. MODEL RUNS FROM THIS MORNING AND MIDDAY
INCLUDING INDIVIDUAL ENSEMBLE MEMBERS MAINTAIN THEIR MEMBER TO
MEMBER...RUN TO RUN...AND MODEL TO MODEL AGREEMENT LEADING TO A
MORE SINGULAR SOLUTION. HOPEFULLY THIS WILL TURN OUT TO BE A
DECENT SOLUTION IF NOT THE BEST.
THIS MORE UNIFIED SOLUTION HAS THE CUT-OFF CLOSED UPPER
LOW...WHICH TAKES UP RESIDENCE OVER OR JUST WEST OF THE NORTHERN
BAJA PENINSULA TONIGHT INTO SATURDAY STARTING TO BE EJECTED BY A
DISTURBANCE DROPPING SOUTH-SOUTHEAST FROM THE GULF OF AK ALONG THE
PACIFIC COAST LATE SUNDAY THROUGH MONDAY. IN RESPONSE THE UPPER
LOW LIFTS NORTHEASTWARD OVER THE CENTRAL PLAINS TUESDAY AND THEN
GRADUALLY OPENS TO AN OPEN WAVE BY LATE WED AS IT CROSSES THE MID
MS VALLEY.
AS THE UPPER LOW/OPEN WAVE MOVES FROM THE EASTERN CENTRAL PLAINS
ACROSS THE MID MS VALLEY AND THE LOWER OH VALLEY LATE TUESDAY
NIGHT THROUGH WEDNESDAY IT WILL BASICALLY BE TRACKING TO THE EAST.
THIS KEEPS THE MAX PRECIP AXIS FROM MO EAST ACROSS SOUTHERN AND
CENTRAL IL AND THEN ACROSS IND...SOUTH OF THE LOCAL FORECAST AREA.
WHILE NORTHERN EDGE OF THE PRECIPITATION SHIELD IS EXPECTED TO
GRADUALLY CREEP FAR ENOUGH NORTHWARD TO GIVE AT LEAST CHANCE
THREAT OF PRECIPITATION FROM LATER MONDAY THROUGH WEDNESDAY.
PRECIPITATION STILL LOOKS TO BE RAIN WITH ONLY A VERY SMALL
THREAT OF MIXED RAIN AND SNOW OR LIGHT SNOW ACROSS THE FAR NORTH
COUNTIES TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE
PRECIPITATION IS MOVING OFF TO THE EAST. LIQUID FORM FAVORED AS
SIGNIFICANT COLD AIR IS HELD AT BAY WITH QUICK PROGRESSION OF
DISTURBANCES MOVING THROUGH THE NORTHERN STREAM NOT PERMITTING
ANY STRONG COLD AIR ADVECTION TO OCCUR BEFORE FLOW BACKS AS THE
NEXT SHORT WAVE APPROACHES.
A RATHER SIGNIFICANT SHORT WAVE IS PROGGED TO DROP ACROSS THE
UPPER MIDWEST...UPPER AND MOD MO VALLEY...AND THE UPPER GREAT
LAKES WEDNESDAY NIGHT...MOVING TO OVER THE CENTRAL GREAT LAKES
BY MIDDAY FRIDAY. HOWEVER...DURING THIS TIME MODELS CONTINUE TO
SHOW A VERY LARGE STRONG ANTICYCLONE SPRAWLED FROM TX TO THE OH
VALLEY AND SOUTHERN GREAT LAKES. THIS WILL KEEP ANY SIGNIFICANT
AWAY FROM THE REGION WITH ONLY A POTENTIAL OF MAINLY LAKE EFFECT
SNOWS DOWNWIND OF THE LAKES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* POTENTIAL FOR IFR/LIFR FOG/STRATUS DEVELOPMENT OVERNIGHT.
* LIGHT WEST-SOUTHWEST WINDS OVERNIGHT BECOMING SOUTHWEST AND
GUSTING 15-20 KTS SUNDAY AFTERNOON/EVENING.
RATZER
//DISCUSSION...UPDATED 06Z...
UPPER-LEVEL DISTURBANCE PULLING EAST OF THE FORECAST AREA LATE
THIS EVENING...WITH CLEARING SKIES SPREADING QUICKLY EAST AS
SUBSIDENCE DEVELOPS BEHIND DEPARTING UPPER TROUGH. EXTRAPOLATION
FROM SATELLITE IMAGERY INDICATES MVFR CIGS WILL CLEAR ORD/MDW
SHORTLY AFTER 06Z AND CLEAR GYY BY 0730Z. QUESTION REMAINS THE
POTENTIAL FOR FOG/LOW STRATUS DEVELOPMENT ACROSS NORTHERN IL AS
SKIES CLEAR AND TEMPERATURES DROP. RPJ/RFD/DKB DISPLAYED QUICK
TEMP DROPS AND FOG/STRATUS DEVELOPMENT EARLIER IN THE EVENING
BEFORE MVFR DECK SPREAD BACK ACROSS THOSE SITES...AND CONCERN IS
THAT SIMILAR TREND WILL OCCUR WITH CLEARING IN NEXT FEW HOURS. 00Z
MODEL SOUNDINGS CONTINUE TO DEPICT VERY SHALLOW BOUNDARY LAYER
SATURATING AT BOTH KRFD/KDPA...SUGGESTING FOG AND PERHAPS IFR OR
EVEN LIFR CEILING DEVELOPMENT. WHILE CONFIDENCE THAT VISIBILITY
WILL LOWER INTO MVFR RANGE IN MANY PLACES...VERY LOW CONFIDENCE
REMAINS WITH COVERAGE OF WHAT MAY BE PATCHY IFR/LIFR CONDITIONS.
HAVE MAINTAINED THE MIDDLE OF THE ROAD THINKING FROM 03Z
AMENDMENTS WITH TEMPO IFR CONDITIONS EARLY SUNDAY MORNING. IF MORE
EXTENSIVE IFR/LIFR DOES DEVELOP...IT MAY TAKE UNTIL 15-16Z BEFORE
STRATUS IS ABLE TO MIX OUT GIVEN RELATIVELY LATE SUNRISE ON NEARLY
THE SHORTEST DAY OF THE YEAR.
IMPROVEMENT TO VFR CONDITIONS IS EXPECTED BY MID-LATE MORNING
HOWEVER...EARLIER IF WIDESPREAD IFR DOES NOT DEVELOP. LOW PRESSURE
MOVING ACROSS CANADA WILL HELP TO TIGHTEN THE PRESSURE GRADIENT
ACROSS THE MIDWEST...WITH SOUTHWEST WINDS INCREASING AND BECOMING
GUSTY IN THE 15-20 KT RANGE IN THE AFTERNOON AND PERHAPS A FEW KTS
HIGHER AT KRFD. WILL LIKELY LOSE HIGHER GUSTS WITH SUNSET BUT
MAINTAIN SUSTAINED WINDS IN THE 10-15 KT RANGE.
LOW LEVEL MOISTURE INCREASES SUNDAY NIGHT AS FAIRLY STRONG WARM
ADVECTION CONTINUES...AND WILL LIKELY SEE VFR CEILINGS DEVELOPING
OVERNIGHT.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* MEDIUM-HIGH CONFIDENCE IN PATCHY IFR FOG/STRATUS DEVELOPING...
BUT LOW CONFIDENCE ON DIRECT IMPACT AT ORD/MDW TERMINALS.
* HIGH CONFIDENCE IN VFR CONDITIONS SUNDAY AFTER ANY MORNING
FOG/STRATUS DISSIPATES.
* HIGH CONFIDENCE IN WIND TRENDS.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN...PSBLY MIXED WITH SNOW AT
ONSET TUES. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
RATZER
&&
.MARINE...
219 PM CST
A PROGRESSIVE WEATHER PATTERN ACROSS THE GREAT LAKES WILL CONTINUE
TO USHER MULTIPLE GUSTY SYSTEMS OVER THE REGION THE NEXT COUPLE OF
DAYS. THE FIRST ONE CENTERED OVER NORTHERN ONTARIO TONIGHT WILL
SWING A TROUGH THROUGH LAKE MICHIGAN THROUGH THE EVENING...TURNING
WINDS TO THE WEST...EVEN SLIGHTLY NORTHWEST IN PARTS OF THE OPEN
WATER. SOME WINDS UP TO 30 KTS ARE POSSIBLE WITH THIS
REGIME...MAINLY IN THE NORTH CLOSER TO THE SYSTEM. A STRONGER LOW
PRESSURE NORTH OF LAKE SUPERIOR WILL RACE EAST ON SUNDAY AFTERNOON
AND EVENING...SWEEPING A COLD FRONT THROUGH THE LAKE SUNDAY NIGHT
INTO EARLY MONDAY. THE TIGHT GRADIENT AROUND THIS LOW AND DEEPER
MIXING WILL SUPPORT GALES ACROSS THE LAKE BEGINNING LATE SUNDAY
AFTERNOON OVER THE NORTH AND SUNDAY EVENING OVER THE SOUTH. THE
WINDOW OF TIME FOR THE GALES WILL BE SHORT...ONLY THROUGH SUNDAY
NIGHT...DUE TO THE QUICK MOVEMENT OF THE SYSTEM. PREVAILING WAVES
UP TO 14 FT ARE EXPECTED ACROSS OPEN WATERS OF THE FAR NORTH. THE
NORTHWEST FLOW BEHIND THE FRONT WILL STILL BE BREEZY ON MONDAY
DESPITE THE WIND SPEEDS GRADUALLY DIMINISHING. HIGH PRESSURE WILL
MOVE OVER THE LAKE MONDAY NIGHT INTO THE DAY TUESDAY.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
140 AM EST SUN DEC 18 2011
.SYNOPSIS...
SNOW SHOWERS WILL SLOWLY END AS WEAK LOW PRESSURE ALOFT EXITS
SUNDAY MORNING. A SLOWING MIDWEST COLD FRONT WILL PROVIDE RAIN
MONDAY AFTERNOON INTO WEDNESDAY WITH PERHAPS A CHANCE OF SNOW
TUESDAY MORNING.
&&
.NEAR TERM /THROUGH TODAY/...
MADE SLIGHT ADJUSTMENTS TO TEMPERATURES, POPS, AND WINDS
OVERNIGHT. RECENT IR SATELITE IMAGERY SHOWS CLOUD TOPS COOLING
AND RADAR SCANS HAVE INDICATED SOME SLIGHTLY STRONGER SNOW BANDS
SO THINK THAT IT IS REASONABLE THAT AT LEAST A FEW TENTHS OF AN
INCH MORE CAN BE EXPECTED...UP TO A HALF INCH THROUGH SUNDAY
MORNING AND AN INCH OR SO OVER THE RIDGES. STILL THINK SNOW SHOULD
END SUNDAY MORNING WITH SUFFICIENT LIFT, AND MOISTURE PUSHING OFF
TO THE EAST. IN ADDITION, THE MORE WESTERLY WIND DIRECTION ALOFT
MAKES LAKE EFFECT ENHANCEMENT UNLIKELY.
850HPA RIDGE IS CURRENTLY OVER THE OHIO VALLEY WITH SOME WAA
KEEPING TEMPERATURES RELATIVELY STEADY THROUGH THE NIGHT, SO MADE
TEMPERATURE ADJUSTMENTS OVERNIGHT AND SUNDAY.
PREVIOUS DISCUSSION FOLLOWS...
PER RECENT SURFACE AND RADAR DATA, COUPLED WITH HRRR AND NAM MODEL
OUTPUT, EXPECT EXITING WEAK LOW PRESSURE ALOFT TO CAUSE LIGHT SNOW
SHOWERS TO SLOWLY END WEST TO EAST OVERNIGHT INTO SUNDAY MORNING.
MOST PLACES WILL GET LITTLE IF ANY ADDED SNOW ACCUMULATION, WITH
PERHAPS UP TO AN INCH ACROSS THE MOUNTAINS.
THE ONLY APPARENT HAZARD AT THIS TIME IS LINGERING BLACK ICE ON
UNTREATED PAVEMENTS.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY/...
DRY AND COOL SUNDAY NIGHT INTO EARLY MONDAY AS SURFACE RIDGE MOVES
OFF THE SOUTHEAST ATLANTIC COAST. BY MONDAY AFTERNOON A COLD FRONT WILL
MOVE INTO NORTHWEST PENNSYLVANIA AND CROSS THE REGION MONDAY
NIGHT. THE FRONT WILL STALL OVER NORTHERN WEST VIRGINIA BEFORE
MOVING NORTHWARD TUESDAY AS DEVELOPING LOW PRESSURE MOVES
NORTHEAST OUT OF TEXAS.
MODELS ARE NOW IN GOOD AGREEMENT ON ENOUGH COLD AIR BEHIND FRONT
FOR RAIN TO MIX WITH SNOW FROM PITTSBURGH SOUTH LATER MONDAY NIGHT
INTO TUESDAY MORNING WITH A PERIOD OF ALL SNOW FROM PITTSBURGH
NORTH AS 1000-850MB THICKNESS FALLS BELOW CRITICAL VALUES. BULK OF
PRECIPITATION STILL LOOKS TO BE RAIN AND SNOW ACCUMULATION LOOKS
TO BE LIMITED AS DEEPER MOISTURE WILL BE IN A FAIRLY NARROW BAND
ALONG AND JUST BEHIND THE FRONT. POPS WERE KEPT HIGH CHANCE TO LOW
LIKELY AS EXACT PLACEMENT OF WHERE BOUNDARY STALLS MONDAY NIGHT
WILL DETERMINE WHERE HIGHEST QPF WILL BE. TEMPERATURES TRENDED A
BIT LOWER ON AVERAGE WITH BETTER PUSH OF COLD AIR NOW EXPECTED.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE FORECAST PERIOD BEGINS WITH REASONABLE GFSE/ECMWF/CANADIAN
AGREEMENT THAT THE CUT OFF LOW OFF OF CALIFORNIA WILL EJECT INTO THE
CENTRAL PLAINS BY TUESDAY NIGHT AND PUSH INTO THE UPPER OHIO VALLEY
AS A TROUGH BY WEDNESDAY NIGHT. A FRONTAL BOUNDARY IN THE VICINITY
OF THE AREA ALONG WITH A MID-LEVEL SOUTHWESTERLY FLOW AHEAD OF THIS
SYSTEM WILL ALLOW FOR LIKELY POPS TUESDAY NIGHT INTO EARLY
WEDNESDAY. HIGH CHANCE POPS ARE FORECAST WEDNESDAY AS THE TROUGH
CROSSES THE AREA. GFS/ECMWF INDICATE CRITICAL THICKNESS LINES FOR
WINTRY PRECIP WILL BE WELL NORTH OF THE AREA AND THUS THE FORECAST
IS PREDOMINATELY IN THE FORM OF RAIN UNTIL THE TROUGH SHIFTS EAST
AND ADVECTS COLD AIR IN BEHIND IT. ON THE BACK SIDE OF THE TROUGH, A
MIX OF RAIN AND SNOW SHOWERS ARE FORECAST WEDNESDAY NIGHT BEFORE
PRECIPITATION COMES TO AN END.
THE TROUGH WILL SHIFT WELL EAST OF THE AREA WITH A DRY FORECAST FOR
THURSDAY. GFSE/ECMWF SOLUTIONS ARE HINTING AT A LOW PRESSURE SYSTEM
CLIPPING THE AREA AS IT PASSES TO THE SOUTHEAST ON FRIDAY. THUS HAVE
CHANCE POPS SOUTH OF PITTSBURGH. AFTER THIS POINT, FORECAST IS
CLOSEST TO THE ECMWF WITH ANOTHER TROUGH PASSING THROUGH AND SCHC
POPS FOR SATURDAY. TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE
NORMAL UNTIL SATURDAY WHEN A CANADIAN HIGH USHERS COLDER AIR INTO
THE REGION AND BRINGS TEMPS CLOSER TO SEASONAL NORMALS.
&&
.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
EXPECT AREAS OF MAINLY MVFR SNOW SHOWERS WITH SPOTTY IFR
RESTRICTIONS TO DECREASE IN COVERAGE EARLY THIS MORNING AS AN UPPER
TROUGH MOVES THROUGH. PREVAILING STRATOCUMULUS BASES WILL LIKELY
FLUCTUATE BETWEEN MVFR AND VFR AND THEN BECOME MAINLY VFR BY MIDDAY
SUNDAY.
OUTLOOK...SUNDAY NIGHT THROUGH THURSDAY...
HIGH PRESSURE WILL MAINTAIN VFR CONDITIONS SUNDAY NIGHT INTO
MONDAY. THE NEXT LOW PRESSURE SYSTEM WILL APPROACH FROM THE
SOUTHWEST MONDAY NIGHT, RETURNING THE CHANCE OF SHOWERS WITH
RESTRICTIONS THROUGH THURSDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
431 AM EST SUN DEC 18 2011
.DISCUSSION /TODAY THROUGH SATURDAY/...
QUIET MORNING ACROSS UPPER MICHIGAN...AS SFC RIDGE IS SLIDING ACROSS
THE UPPER GREAT LKS REGION. PERSISTENT AREA OF LOW CLOUDS EARLY THIS
MORNING ON SATELLITE...STRETCHING SW INTO NRN WI. MOST MODELS HAVING
A DIFFICULT TIME WITH THEM...BUT RUC SEEMS TO HAVE A DECENT HANDLE
ON LOW CLOUDS ON 0.5-1KM RH FIELDS...SO HAVE FOLLOWED THAT FOR THE
EXIT OF THE MVFR CLOUDS THIS MORNING. THINK THEY WILL LIKELY PERSIST
THROUGH THE FIRST PART OF THE MORNING UNTIL LLVL WINDS SHIFT TO THE
SW AND PUSH THEM NE OF THE AREA.
1002MB LOW PRESSURE SYSTEM CURRENTLY LOCATED JUST NW OF LK WINNIPEG
WILL SLOWLY DEEPEN THROUGH THE DAY...AS A NRN STREAM SHORTWAVE
AMPLIFIES OVER SOUTHERN CANADA THROUGH THE DAY. BY 00Z...SHOULD SEE
A 999MB LOW LOCATED JUST TO THE N OF LK SUPERIOR. STRONG H850-500
WAA OVER SRN CANADA /AND PRODUCING A FEW -SHSN E OF LK WINNIPEG/
WILL SHIFT ESE THROUGH SRN ONTARIO AND FAR NRN LK SUPERIOR FROM MID
MORNING THROUGH THE REST OF THE DAY. WITH THE BEST MOISTURE LOCATED
IN THIS AREA...EXPECT THE PCPN TO STAY N OF THE LAND AREAS. HEADING
FARTHER S OVER UPPER MI...DRY AIR BELOW H750 SHOULD KEEP ANY PCPN
COMING OUT OF THE MID CLOUDS FROM REACHING THE SFC FROM MID MORNING
THROUGH EARLY AFTN. LIKELY WON/T SEE MUCH SUN THROUGH THE MORNING
HOURS WITH THE LINGERING LLVL CLOUDS THAT WILL BE OVERRUN BY THE
INCOMING MID CLOUDS. DRY SLOT BEGINS TO MOVE OVER THE AREA AROUND
MID AFTN AND MAY LEAD TO SOME CLEARING...ESPECIALLY OVER THE W HALF.
WITH THE LOW INTENSIFYING AS IT MOVES N OF THE AREA...WILL LIKELY
SEE SOME GUSTY SW WINDS THIS AFTN. STRENGTHENING INVERSION AROUND
H900 WILL LIMIT ACCESS TO THE LLVL JET AROUND 45KTS. BUT TIGHTENING
PRESS GRADIENT WILL STILL LEAD TO GUSTS IN THE 20-30KT
RANGE...ESPECIALLY IN THE SW WIND DOWNSLOPE AREAS NEAR LK SUPERIOR.
THE INVERSION AND CLEARING THIS AFTN MAKES TEMPS TRICKY...AS THERE
WILL BE A LIMITED PERIOD FOR SUNSHINE HELP MIX HIGHER ALOFT. THOUGH
PREVIOUS HIGHS LOOKED GOOD AND ONLY MADE MINOR TWEAKS. WITH THE WARM
START AND SSWRLY FLOW...EXPECT THE HIGHS TO BE IN THE UPPER 30S AND
MAYBE AN ISOLATED 40 OVER THE WRN CWA /WHERE WARMER AIR SURGES INTO
THE AREA AND THERE IS A LONGER PERIOD OF CLEAR SKIES/...ALONG WITH
DOWNSLOPE AREAS NEAR LK SUPERIOR.
SFC LOW WILL QUICKLY DEEPEN TO 993MB THROUGH THE NIGHT AS IT SHIFTS
JUST SE OF JAMES BAY BY 12Z. DRY SLOT WILL STILL BE OVER THE AREA
AND PROVIDE A CLEAR BUT BREEZY EVENING. SFC TROUGH/COLD FRONT WILL
THEN SLIDE SE THROUGH THE CWA AFTER MIDNIGHT AND BRING A CHANCE FOR
PCPN TO AREAS NEAR LK SUPERIOR. NOT OVERLY IMPRESSED WITH
FORCING/MOISTURE ALONG THE FRONT...SO HAVE WENT WITH SLIGHT
CHANCES...EXCEPT FOR FAVORABLE UPSLOPE NW WIND LOCATIONS OVER THE
WRN CWA. P-TYPE WILL BE SNOW INITIALLY WITH THE PASSAGE OF THE
FRONT...BUT COULD BE SOME FZDZ WITH THE UPSLOPE FLOW OVER THE WRN
U.P. SOUNDINGS SHOW INCREASING LLVL LAPSE RATES OVER THE WEST AFTER
06Z TONIGHT BELOW THE 3-4KFT INVERSION. WITH NEAR SFC DRY AIR
PUTTING CLOUD BASES AROUND 1.5-2.5KFT...OVERALL CLOUD DEPTH WILL BE
FAIRLY SHALLOW. IN ADDITION...CLOUD TOPS ARE ONLY AROUND -7 TO -8C
AFTER THE FRONT MOVES THROUGH...LIMITING ICE CRYSTALS IN THE CLOUDS.
THEREFORE...HAVE ADDED A MENTION OF FZDZ OVER THE W AFTER 09Z. OVER
THE E...WARMER TEMPS WILL LIKELY LEAD TO MORE OF A DZ/SN POTENTIAL
LATE TONIGHT.
WITH CONTINUED H925-850 MOISTURE AND H850 TEMPS FALLING TOWARDS -10C
BY MID MORNING...EXPECT A PERIOD OF LK ENHANCED PCPN DURING THE
MORNING HOURS. TEMPS SHOULD FALL ENOUGH MON MORN OVER THE W TO
PRODUCE ENOUGH ICE CRYSTALS FOR ANY LINGERING SHOWERS TO BE ALL
SNOW. THERE COULD BE A SLIGHT LAG OVER THE E NEAR LK SUPERIOR FOR
THE FIRST COUPLE OF HOURS AND MENTIONED A -SHSN/FZDZ INITIALLY IN
THE MORNING. LAKE EFFECT POTENTIAL QUICKLY DIMINISHES HEADING INTO
THE AFTN...AS H850-700 SUBSIDENCE INCREASES AND LLVL MOISTURE
DEPARTS. IN ADDITION...MODELS SHOWING INVERSION HEIGHTS AT OR BELOW
3KFT IN THE AFTN AND LOCAL/NATIONAL HIRES WRF RUNS NOT SHOWING ANY
PCPN. WITH ALL THE NEGATIVES...HAVE TAPERED BACK EXISTING POPS IN
THE AFTN...BUT DID LEAVE SOME LOW CHANCES OVER THE E FOR NNW WIND
FAVORED LOCATIONS WHERE THE LONGER FETCH MAY HELP KEEP PCPN GOING.
HIGH PRESSURE RIDGE WILL BUILD OVER THE AREA ON MON NIGHT...BRINGING
AN END TO ANY LINGERING LES EARLY IN THE EVENING. WITH LIGHT WINDS
AND CLEAR SKIES UNDER THE HIGH PRESSURE RIDGE...EXPECT A GOOD
RADIATIONAL COOLING NIGHT. PWAT VALUES /AROUND 0.1 INCH OR 35
PERCENT OF NORMAL/ SUPPORT GOING ON THE LOW END OF GUIDANCE...AND
HAVE LOWS FALLING INTO THE SINGLE DIGITS ABOVE ZERO.
NRN STREAM OF THE JET WILL REMAIN N OF THE AREA FOR TUES/WED...WHILE
THE SRN STREAM IS LOCATED OVER THE SRN CONUS. THIS LEAVES THE AREA
WITH FAIRLY QUIET AND SEASONABLE CONDITIONS. SFC RIDGE WILL BE OVER
THE CWA AT THE START OF TUES...WITH ANOTHER SHORTWAVE MOVING THROUGH
SRN CANADA IN THE NRN STREAM. AS WITH THE SYSTEM TODAY...MAIN
ENERGY/MOISTURE WILL BE JUST TO THE N OF THE AREA...BRUSHING NRN LK
SUPERIOR. AS THIS QUICKLY MOVES E TUES EVENING...WEAK SFC RIDGE WILL
LIKELY BUILD BACK OVER THE AREA FOR TUES NIGHT INTO WED MORNING.
SEASONABLE TEMPS WILL CONTINUE...ALTHOUGH THE GUSTY WINDS AT TIMES
WILL MAKE IT FEEL A LITTLE COOLER.
DIFFERENCES START TO APPEAR IN THE EXTENDED MODELS WED INTO THURS
NIGHT WITH THE HANDLING OF THE EASTWARD MOVING UPPER LOW IN THE SRN
STREAM THAT WILL BE OVER THE CNTRL ROCKIES ON WED. ANOTHER NRN
STREAM TROUGH WILL BE DROPPING THROUGH THE CANADIAN ROCKIES AT THIS
TIME AND THEY WILL TRY TO MERGE THE NRN/SRN STREAMS OVER THE GREAT
LAKES REGION. 00Z RUNS OF THE GFS/ECMWF/GEM HAVE SPED UP THE EXITING
SRN STREAM WAVE...PUSHING IT THROUGH THE LOWER GREAT LKS AND OHIO
VALLEY BY 06Z THURS. AT THAT TIME...NRN STREAM WAVE WILL BE
APPROACHING THE UPPER GREAT LKS AND PASS THROUGH ON THURS.
THUS...WILL CONTINUE TO MENTION PCPN CHANCES DURING THAT
TIME...MAINLY DUE TO THE APPROACHING NRN STREAM WAVE.
BEHIND THESE DISTURBANCES...COLDER H850 TEMPS /TOWARDS -14C/ WILL
FILTER OVER THE UPPER GREAT LKS THURS INTO FRI AND LEAD TO LES UNDER
NWRLY FLOW. BEST CHANCES LOOK TO BE THURS INTO FRI MORNING WITH
ADDITIONAL MOISTURE FROM THE UPPER TROUGH...BEFORE SFC HIGH BEGINS
TO PULL DRIER AIR AND WARMER TEMPS ALOFT IN ON FRI AFTN. HAVE STUCK
WITH LOW CHANCES FOR NOW...BUT MAY NEED TO BUMP UP POPS IF
CONDITIONS REMAIN FAVORABLE. SWRLY FLOW WILL REDEVELOP FRI NIGHT AND
CONTINUE INTO SAT...AHEAD OF THE NEXT NRN STREAM SHORTWAVE TO AFFECT
THE AREA LATE SAT.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
STRATUS DECK WITH MVFR CIGS SHOULD GRADUALLY LIFT FROM THE WEST AS
SFC RDG AXIS MOVES ACROSS THE AREA IN THE OVERNIGHT AND EARLY
MORNING HRS. AFTER CLOUDS DISSIPATE LOOK FOR VFR CONDITIONS THROUGH
THE DAY TODAY. INCREASING SOUTHERLY WINDS GUSTING 22 TO 25KTS BEHIND
THE SFC RDG AND AHEAD OF NEXT APPROACHING TROUGH FROM THE NRN PLAINS
WILL RESULT IN GUSTY SSW WINDS TO 25 KT...ESPECIALLY AT KIWD AND KSAW
BY EARLY AFTERNOON. EXPECT LLWS WIND SHEAR AT ALL TAF SITES THIS
EVENING WITH TIGHT SW GRADIENT AHEAD OF THE TROUGH. SOME GUSTY WRLY
WINDS BEHIND THE TROF/FRONTAL PASSAGE CAN BE EXPECTED AT KCMX AROUND
MIDNIGHT SUNDAY NIGHT.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
AS PRES GRADIENT TIGHTENS WITH LOW PRES MOVING ACROSS MANITOBA INTO
NRN ONTARIO...SW WINDS WILL BE ON THE INCREASE TODAY. ALTHOUGH
INVERSION WILL LIMIT NEAR SFC WINDS FROM BEING STRONGER...AREA OF
PRES FALLS ON THE ORDER OF 6MB/3HR PASSING OVER AND JUST N OF LAKE
SUPERIOR WILL WORK TO BOOST WINDS TO GALE FORCE OVER CNTRL AND ERN
LAKE SUPERIOR LATER THIS AFTERNOON AND TONIGHT. HIGHEST WINDS...
PERHAPS GUSTING TO AROUND 40KT...WILL LIKELY OCCUR OVER EASTERN
PORTIONS OF THE LAKE FROM STANNARD ROCK EASTWARD DUE TO FAVORABLE
POSITIONING OF PRES FALLS. AREA AROUND GRAND MARAIS SHOULD BE
ESPECIALLY FAVORED FOR STRONGER WINDS FOR A FEW HRS THIS EVENING.
AFTER COLD FRONTAL PASSAGE TONIGHT ASSOCIATED WITH THE LOW PRES
SYSTEM...NW WINDS WILL PROBABLY GUST TO AROUND 35KT OVER THE E HALF
OF THE LAKE INTO MON MORNING. WINDS WILL DIMINISH W TO E MON
AFTN/NIGHT AS HIGH PRES SYSTEM QUICKLY PASSES ACROSS THE GREAT
LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL PROBABLY
BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR. SW
WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE
FOR STRONGEST WINDS TUE. GALES WILL END TUE NIGHT AS PRES GRADIENT
WEAKENS. WINDS WILL BE BLO 30KT FOR WED/THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING FROM 3 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ266-267.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST MONDAY FOR
LSZ264.
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST MONDAY FOR
LSZ263.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR
LMZ248-250.
&&
$$
DISCUSSION...SRF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
235 AM CST SUN DEC 18 2011
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES CONTINUE TO
SHOW A CUTOFF UPPER LOW OVER THE SOUTHWEST US WITH A BROAD RIDGE
OVERTOP OF IT EXTENDING FROM THE PACIFIC NORTHWEST COAST INTO THE
UPPER MIDWEST. THE DEEP UPPER LOW NORTH OF HUDSON BAY HAS MOVED
LITTLE OF LATE... AND SHOW NO SIGNS OF GOING ANYWHERE THROUGH AT
LEAST THE NEXT 10 DAYS ON THE GFS... ECMWF... AND THEIR RESPECTIVE
ENSEMBLES. IN THE BIG PICTURE... THIS SUGGESTS CONDITIONS IN OUR
NECK OF THE WOOD SHOULDN/T CHANGE TOO MUCH THROUGH AT LEAST THE
NEXT WEEK OR TWO... WITH NEAR TO ABOVE NORMAL TEMPERATURES
PREDOMINATING AS WEST TO NORTHWEST MID-UPPER LEVEL FLOW CONTINUES
TO BRING SYSTEMS OF PACIFIC ORIGIN INTO OUR AREA. WE WILL CONTINUE
TO SEE FAIRLY FREQUENT COLD FRONTAL PASSAGES... BUT NONE LOOK TO
BRING ANY TRUE ARCTIC AIR INTO THE REGION... AND INSTEAD WILL
SIMPLY BRING TEMPERATURES DOWN TO NEAR OR PERHAPS SLIGHTLY BELOW
NORMAL FOR BRIEF PERIODS OF TIME AS THEY MOVE THROUGH. AS FAR AS
PRECIPITATION GOES... THE PRESENT LONG WAVE PATTERN IS NOT
CONDUCIVE TO US SEEING MUCH... WITH MINIMAL MOISTURE RETURN AHEAD
OF INDIVIDUAL SHORTWAVES... AND THE DEEPENING OF SYSTEMS OCCURRING
SOUTH AND EAST OF OUR AREA AS THEY MOVE INTO THE MEAN LONG WAVE
TROUGH POSITION.
ROBUST WARM ADVECTION WILL OCCUR ACROSS THE AREA TODAY... WITH
TEMPERATURES SOARING INTO THE 40S IN MOST LOCATIONS... AND LIKELY
ECLIPSING THE 50 DEGREE MARK OVER WEST CENTRAL AND SOUTHWEST
MINNESOTA. IT ISN/T TOO OFTEN WE SEE 850MB TEMPERATURES IN EXCESS
OF 8C... BUT THAT LOOKS TO BE THE CASE TODAY OVER THE SOUTHERN
PART OF THE STATE. WE CERTAINLY WON/T MIX TO 850MB... BUT EVEN
MIXING THROUGH 950MB WILL ALLOW TEMPERATURES TO CLIMB TO AOA 50
DEGREES OVER MANY AREAS SOUTH AND WEST OF THE TWIN CITIES.
WOULDN/T BE SHOCKED IF THE TWIN CITIES MANAGES TO GET CLOSE TO 50
DEGREES DEPENDING UPON HOW WELL THINGS MIX OR IF WE/RE ABLE TO
ADVECT SOME OF THE WARMER UPSTREAM READINGS INTO THE AREA DURING
THE AFTERNOON HOURS. JUST NUDGED READINGS UP SLIGHTLY OVER
PREVIOUSLY FORECAST VALUES... BUT IT WILL CERTAINLY BE SOMETHING
TO KEEP AN EYE ON TODAY. LOW PRESSURE ASSOCIATED WITH THE
SHORTWAVE CURRENTLY SEEN MOVING INTO ALBERTA WILL PASS BY NORTH OF
THE STATE THIS EVENING... DRAGGING A COLD FRONT ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. THIS WILL COOL THINGS DOWN
TO ABOUT WHERE THEY SHOULD BE FOR MONDAY. A FEW FLURRIES COULD BE
SEEN BEHIND THE FRONT DEPENDING UPON HOW DEEP THE MOISTURE IS
BENEATH THE SUBSIDENCE INVERSION AND IF CYCLONIC BOUNDARY LAYER
FLOW IS ABLE TO LINGER. AT THIS POINT... THE CHANCES LOOK MINIMAL
AND IT WOULD ONLY BE SCATTERED FLURRIES AT BEST... SO LEFT IT OUT
OF THE FORECAST.
HIGH PRESSURE WILL BUILD ACROSS THE REGION MONDAY AFTER THROUGH
MONDAY NIGHT... AS THE 850-700MB THERMAL TROUGH MOVES ACROSS THE
AREA AND WEAKENS. THIS WILL BRING WHAT WILL FEEL LIKE A CHILLY
NIGHT MONDAY NIGHT... ALTHOUGH READINGS STILL LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL. WEAK WARM ADVECTION LOOKS TO BE IN PLACE
ACROSS THE REGION TUESDAY AND TUESDAY NIGHT AS A SHORTWAVE AND
SURFACE LOW MOVE BY WELL NORTH OF THE US/CANADA BORDER... AND A
SURFACE LOW ASSOCIATED WITH THE CUTOFF LOW CURRENTLY OVER THE
SOUTHWEST MOVES OUT OF THE SOUTHERN PLAINS TO THE OHIO VALLEY. WE
WILL FIND OURSELVES NESTLED BETWEEN THESE FEATURES... WITH BENIGN
WEATHER IN PLACE. A SLOWLY MOVING COLD FRONT WILL DROP SOUTH
THROUGH THE REGION WEDNESDAY INTO THURSDAY. THERE ARE SOME HINTS
WE COULD SEE MOISTURE POOL SUFFICIENTLY ALONG THIS BAROCLINIC ZONE
TO GET SOME PCPN DEPENDING UPON WHEN THE UPSTREAM SHORTWAVE
DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA IS ABLE TO CATCH UP
WITH IT. GIVEN UNCERTAINTIES IN NOT ONLY IF SOME PCPN WILL BE
SQUEEZED OUT... BUT WHEN AND WHERE IT MIGHT OCCUR... CHOSE TO
LEAVE PCPN OUT OF THE FORECAST IN THE WEDNESDAY TO THURSDAY TIME
FRAME... BUT FEEL THERE IS AT LEAST A CHANCE FOR SOME FLURRIES OF
VERY LIGHT SNOW DURING THAT PERIOD WHICH MAY GET INCLUDED AS WE
GET CLOSER TO THAT TIME PERIOD. THE MEDIUM RANGE GUIDANCE BECOMES
QUITE MUDDY IN ITS AGREEMENT BY WEEK/S END... WITH THE
DETERMINISTIC GFS AND ECMWF DIFFERING BY 15-20MB IN SURFACE
PRESSURES OVER OUR AREA BY FRIDAY AS THE GFS CLOSES OFF A SURFACE
LOW IN THE SAME AREA WHERE THE ECMWF SUGGESTS A FAIRLY POTENT
RIDGE. THE ECMWF SOLUTION WOULDN/T SUPPORT ANY PCPN... AND THE GFS
WOULD SUGGEST VERY LITTLE... SO THE PATH OF LEAST RESISTANCE AT
THIS POINT IS SIMPLY TO KEEP THINGS DRY.
&&
.AVIATION... /06Z TAF ISSUANCE/
/ISSUED 1135 PM CST SAT DEC 17 2011/
FEW PROBLEMS SEEN THIS TAF PERIOD AS A WARM FRONT IN THE DAKOTAS
MOVES EASTWARD ACROSS THE TAF SITES EARLY ON SUNDAY. SOME MINOR
VISIBILITY RESTRICTIONS OF 4-6SM BR POSSIBLE THROUGH DAYBREAK AT
KRNH AND KEAU BUT CONFIDENCE IS NOT HIGH WITH SCT-BKN CI/CS
DROPPING SOUTHEAST ACROSS THE AREA. SURFACE WINDS WILL INCREASE
TO 12-15 KNOTS AFTER 15Z ON SUNDAY WITH GUSTS FROM 18-23 KNOTS.
CONCERNS BEGIN AROUND 19/03Z AS A COLD FRONT BEGINS TO MOVE
SOUTH INTO CENTRAL MN. GUIDANCE IS SHOWING SOME POTENTIAL FOR
BKN010 IN THE WAKE OF THE FRONT FOR A FEW HOURS. TRAJECTORY
FORECASTS FROM NORTHWEST OF LAKE WINNIPEG...WHERE SOME MVFR
CEILINGS ARE LOCATED NOW...DO MAKE IT INTO NORTHWEST MN BY 19/03Z.
SO THERE IS SOME POTENTIAL THAT THIS SCENARIO COULD OCCUR.
HOWEVER...GIVEN THE TIME FRAME...CONFIDENCE IS LOW AND FEW-
SCT010-015 INSERTED INTO THE KAXN AND KSTC TAFS AS A START.
KMSP...LIGHT SOUTH WINDS OVERNIGHT WILL INCREASE TO 12 KNOTS WITH
GUSTS TO 18 KNOTS AFTER 16Z AND CONTINUE THROUGH THE AFTERNOON
BEFORE DIMINISHING AND BECOMING SOUTHWEST SUNDAY EVENING. A COLD
FRONT WILL PASS THE AIRPORT AROUND 19/07Z. SOME POTENTIAL FOR
BKN010-015 IN THE WAKE OF THE FRONT BETWEEN 07Z-12Z. CONFIDENCE IS
LOW AND INSERTED FEW015 IN THE TAF TO INDICATE THE POTENTIAL.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/RAH
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1232 AM EST SUN DEC 18 2011
.SYNOPSIS...
MUCH COLDER TEMPERATURES CONTINUE FOR THE OVERNIGHT HOURS AS
TEMPERATURES DROP INTO THE SINGLE DIGITS ABOVE AND BELOW ZERO.
LOCALIZED LAKE CHAMPLAIN LAKE EFFECT SNOW SHOWERS WILL BE
POSSIBLE TONIGHT...WITH SOME LIGHT ACCUMULATION ACROSS THE
CHAMPLAIN VALLEY. MAINLY CLEAR SKIES WILL CONTINUE FOR
SUNDAY...BEFORE A WEAK WARM FRONT PRODUCES SOME CLOUDS AND A
CHANCE OF SNOW SHOWERS LATE SUNDAY INTO MONDAY.
&&
.NEAR TERM /UNTIL 7 AM THIS MORNING/...
AS OF 1230 AM EST SUNDAY...FCST IN GREAT SHAPE THIS MORNING WITH
ONE MINOR CHANGE. HAVE DECREASE TEMPS BY SEVERAL DEGREES ACRS
NORTHERN NY PER LATEST OBS. SLK ALREADY AT -3F AND MSS AT
+2F...THINKING NEAR -10F FOR SLK AND -4F FOR MSS...WITH SINGLE
DIGITS ABOVE ZERO FOR THE CPV AND NEAR ZERO FOR PARTS OF CENTRAL AND
NORTHERN VT...WITH NEAR 10F FOR SOUTHERN VT. OTHERWISE...STILL
WATCHING SOME WEAK LAKE CHAMPLAIN ACTIVITY PER LATEST RADAR...BUT
OVERALL INTENSITY/COVERAGE IS LIMITED DUE TO LLVL DRY AIR AND WIND
SHEAR PER LATEST VAD FROM KCXX. THINKING A DUSTING OR SO WL STILL
BE POSSIBLE NEAR LAKE CHAMPLAIN BY MORNING AND WL CONT TO MENTION
SCHC TO CHC POPS IN A NARROW BAND. REST OF FCST IN GREAT.
MINOR UPDATE TO SNOW SHOWER/FLURRY CHANCES ALONG LAKE CHAMPLAIN
THROUGH THE REMAINDER OF THE NIGHT. LOWERING INVERSION HEIGHT AND
DRY AIR ADVECTION SHOULD LIMIT ACTIVITY TO MAINLY VERY LIGHT
ACTIVITY WITH LITTLE MORE THAN A DUSTING OVERNIGHT IN FAVORED
AREAS FROM SHELBURNE TO CHARLOTTE...FERRISBURGH AND THE WESTERN
LAKESHORE IN ESSEX COUNTY NEW YORK FROM WILLSBORO TO WESTPORT.
REST OF FCST UNCHANGED.
PRIOR DISCUSSION FROM 622 PM EST SATURDAY...
FORECAST ESSENTIALLY ON TRACK FOR THIS EVENING AND HAVE MADE ONLY
MODEST ADJUSTMENTS TO SKY COVER THROUGH THE EVENING/OVERNIGHT
HOURS BASED OFF IR SATELLITE DATA AND RUC13 850 HPA RH PROGS. THIS
WOULD SUGGEST SKIES TO REMAIN PTLY CLOUDY THROUGH MIDNIGHT OR
SO...THEN TRENDING MAINLY CLEAR IN MOST AREAS BY MORNING OUTSIDE
IMMEDIATE VCNTY OF LAKE CHAMPLAIN. RECENT AIRCRAFT DATA OUT OF
PIERRE TRUDEAU APT IN MONTREAL CONFIRM RUC/NAM/GFS 850 HPA TEMPS
OF AROUND -18C...SO SEE NO REASON TO DISCOUNT PRESENT CHILLY LOW
TEMP FORECAST IN THE -7 TO +7F RANGE BY SUNDAY MORNING...SLIGHTLY
MILDER SOUTH. IN REGARD TO THE CHAMPLAIN LAKE EFFECT...EVOLVING
NORTHERLY TRAJECTORIES AND LAKE-850 HPA AIR TEMP DIFFERENCE NEAR
24C MORE THAN SUFFICIENT TO ALLOW PERIODIC SNOW SHOWERS/FLURRIES
TO CONTINUE OVERNIGHT TO THE SOUTH AND EAST OF THE LAKE. LIMITING
FACTORS INCLUDING SHALLOW BOUNDARY LAYER AND DRY AIR ADVECTION
SHOULD PRECLUDE ANYTHING SUBSTANTIAL HOWEVER. AGAIN...PRESENT FCST
HAS THIS COVERED SO OTHER THAN SKY ADJUSTMENTS NOTED ABOVE...NO
OTHER CHANGES NEEDED AT THIS TIME. ENJOY YOUR EVENING.
&&
.SHORT TERM /7 AM THIS MORNING THROUGH MONDAY NIGHT/...
AS OF 300 PM EST SATURDAY...MID/UPPER LEVEL RIDGE BUILDS ACROSS
OUR CWA AS SURFACE HIGH PRESSURE SHIFTS TOWARD EASTERN NEW
ENGLAND. GIVEN DEEP DRY LAYER AND PLENTY OF NVA FROM BUILDING
HGHTS...EXPECT MAINLY CLEAR SKIES WITH MAX TEMPS ON SUNDAY AROUND
TEN DEGREES BELOW NORMAL. TEMPS RETURN TO NEAR NORMAL BY SUNDAY
NIGHT AS 850 TEMPS SLOWLY WARM FROM THE NEGATIVE TEENS ON SUNDAY
TO NEGATIVE SINGLE DIGITS SUNDAY NIGHT. MONDAY WILL BEGIN DRY
WITH HIGH PRESSURE STILL IN PLAY...BUT BY LATE MONDAY...ANOTHER
SFC COLD FRNT APPROACHES OUR WESTERN CWA. WITH A GOOD RIBBON OF
850 TO 500MB MOISTURE AND STRONG SFC CONVERGENCE. THIS COMBINED
WITH STEEP 0 TO 2 KM AGL LAPSE RATES...AND POTENTIAL FOR SOME
LAKE MOISTURE INTERACTION...A BAND OF SNOW SHOWERS AND SNOW
SQUALLS LOOKS POSSIBLE LATE MONDAY AFTN INTO MONDAY NIGHT. WINDS
ALSO LOOK STRONG ON MONDAY AS 850 JET PEAKS AROUND 60 KTS DURING
THE AFTERNOON. HAVE CONTINUED WITH MENTION OF LIKELY POPS ACROSS
NORTHERN NY/VT BY 00Z...WITH A QUICK INCH OR TWO OF SNOW
POSSIBLE. TEMPERATURES WILL WARM BACK INTO THE 30S TO NEAR 40F ON
MONDAY...ASSOCIATED WITH SOUTHERLY FLOW AHEAD OF BOUNDARY.
OVERNIGHT MIN TEMPS WILL BE SLIGHTLY WARMER THAN NORMAL WITH
RESIDUAL CLOUDS FROM FRONT AND WINDS PROMOTING MIXING.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 247 PM EST SATURDAY...THE EXTENDED FCST PERIOD STARTS QUIET
AS SFC RIDGE OF HIGH PRESSURE CRESTS OVER NY AND NEW ENGLAND ON
TUESDAY. SHOULD SEE MOSTLY SUNNY SKIES TUESDAY WITH LIGHT WINDS
AND SEASONABLY TEMPS /HIGHS IN THE UPR 20S TO LOWER 30S/. RIDGE
AXIS SHIFTS EAST TUESDAY NIGHT WITH DEVELOPING S-SW WINDS. MAY
SEE TEMPS LEVELING OUT IN THE CHAMPLAIN AND ST. LAWRENCE VALLEYS
WITH INCREASED MIXING AND DEVELOPING WARM ADVECTION REGIME.
MODELS HAVE DIVERGED COMPARED TO PREVIOUS RUNS FOR POTENTIAL
PRECIPITATION SYSTEM WEDNESDAY INTO WEDNESDAY NIGHT. THE 12Z GFS
AND ECMWF SOLNS SHOW THAT THE NORTHERN AND SOUTHERN STREAMS ARE
NO LONGER IN PHASE...WITH SRN STREAM SHORTWAVE TROUGH PRECEDING
NORTHERN STREAM AS VORT MAX EMERGES FROM THE OHIO RIVER VALLEY.
THE 12Z GFS IS A BIT FASTER...WITH VORT PASSING THRU PA AND THEN
OFFSHORE SOUTH OF LONG ISLAND. THE BULK OF ASSOCIATED
PRECIPITATION REMAINS SOUTH OF THE NORTH COUNTRY AS WELL. HIGHEST
POPS WOULD OCCUR LATE TUESDAY NIGHT INTO WEDNESDAY. THE ECMWF IS
ABOUT 12 HRS SLOWER AND WARMER ALOFT...WITH 850MB TEMPS +5C AT
00Z THU. HAVE CUT BACK ON POPS TO 30-40 PERCENT...AND HAVE
INDICATED MIXED PRECIPITATION TYPES BASED. NOT EXPECTING A LOT OF
QPF AT THIS POINT BASED ON ABSENCE OF PHASING AND GFS TRACK. WILL
CONTINUE TO MONITOR...BUT SIGNIFICANT WEATHER IMPACTS LOOK LESS
LIKELY THAN THIS TIME YESTERDAY.
THE 12Z GFS MAINTAINS A MORE SIGNIFICANT UPPER TROUGH LATE NEXT
WEEK AND OFFERS A COLDER SOLN THU-FRI AS COMPARED TO THE ECMWF.
HAVE MADE SOME ADJUSTMENTS BETWEEN THE TWO MODELS...INDICATING
HIGHS MOSTLY IN THE 30S WITH LOWS IN THE 20S...SO SOMEWHAT ABOVE
CLIMO ON TEMPS. CAN`T RULE OUT SOME SNOW SHOWER ACTIVITY
THU/FRI...BUT OVERALL NO SIGNIFICANT WEATHER EXPECTED AT THIS
TIME.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
THROUGH 06Z MONDAY...MAINLY VFR CONDITIONS EXPECTED THROUGH THE
PERIOD...EXCEPT FOR POSSIBLE MVFR AT KBTV/KSLK THROUGH 12Z. PATCHY
BR POSSIBLE AT KSLK...WHILE CLOUDS ASSOCIATED WITH SNOW SHOWERS
OVER LAKE CHAMPLAIN MAY DRIFT OVER KBTV AT TIMES. OTHERWISE...
MAINLY CLEAR SKIES THROUGH SUNDAY...WITH INCREASING CLOUDS SUNDAY
NIGHT. WINDS LIGHT AND VARIABLE...THEN BECOMING SSW 5-10 KTS OVER
NORTHERN NY SUNDAY AFTERNOON AND OVER VT SUNDAY NIGHT.
OUTLOOK 06Z MONDAY THROUGH THURSDAY...HIGH PRESSURE BRINGS MAINLY
VFR CONDITIONS THRU 18Z MONDAY. COLD FRONT MONDAY AFTERNOON INTO
MONDAY NIGHT MAY BRING LOCALLY GUSTY W-NW WINDS TO 25 KTS AND
SCATTERED SNOW SHOWERS WITH A PERIOD OF MVFR OR BRIEF IFR
CONDITIONS. NEXT PRECIPITATION SYSTEM ARRIVES LATE TUESDAY NIGHT
INTO WEDNESDAY...THOUGH CURRENT INDICATIONS ARE THAT BULK OF
PRECIPITATION WILL SLIDE SOUTH OF THE NORTH COUNTRY. A PERIOD OF
SNOW OR MIXED PCPN IS EXPECTED TO BE LIGHT AT THIS TIME.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...NEILES
NEAR TERM...JMG/TABER
SHORT TERM...NEILES
LONG TERM...BANACOS
AVIATION...RJS/LOCONTO
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1230 AM EST SUN DEC 18 2011
.SYNOPSIS...
MUCH COLDER TEMPERATURES CONTINUE FOR THE OVERNIGHT HOURS AS
TEMPERATURES DROP INTO THE SINGLE DIGITS ABOVE AND BELOW ZERO.
LOCALIZED LAKE CHAMPLAIN LAKE EFFECT SNOW SHOWERS WILL BE
POSSIBLE TONIGHT...WITH SOME LIGHT ACCUMULATION ACROSS THE
CHAMPLAIN VALLEY. MAINLY CLEAR SKIES WILL CONTINUE FOR
SUNDAY...BEFORE A WEAK WARM FRONT PRODUCES SOME CLOUDS AND A
CHANCE OF SNOW SHOWERS LATE SUNDAY INTO MONDAY.
&&
.NEAR TERM /UNTIL 7 AM THIS MORNING/...
AS OF 927 PM EST SATURDAY...MINOR UPDATE TO SNOW SHOWER/FLURRY
CHANCES ALONG LAKE CHAMPLAIN THROUGH THE REMAINDER OF THE NIGHT.
LOWERING INVERSION HEIGHT AND DRY AIR ADVECTION SHOULD LIMIT
ACTIVITY TO MAINLY VERY LIGHT ACTIVITY WITH LITTLE MORE THAN A
DUSTING OVERNIGHT IN FAVORED AREAS FROM SHELBURNE TO
CHARLOTTE...FERRISBURGH AND THE WESTERN LAKESHORE IN ESSEX COUNTY
NEW YORK FROM WILLSBORO TO WESTPORT. REST OF FCST UNCHANGED.
PRIOR DISCUSSION FROM 622 PM EST SATURDAY...
FORECAST ESSENTIALLY ON TRACK FOR THIS EVENING AND HAVE MADE ONLY
MODEST ADJUSTMENTS TO SKY COVER THROUGH THE EVENING/OVERNIGHT
HOURS BASED OFF IR SATELLITE DATA AND RUC13 850 HPA RH PROGS. THIS
WOULD SUGGEST SKIES TO REMAIN PTLY CLOUDY THROUGH MIDNIGHT OR
SO...THEN TRENDING MAINLY CLEAR IN MOST AREAS BY MORNING OUTSIDE
IMMEDIATE VCNTY OF LAKE CHAMPLAIN. RECENT AIRCRAFT DATA OUT OF
PIERRE TRUDEAU APT IN MONTREAL CONFIRM RUC/NAM/GFS 850 HPA TEMPS
OF AROUND -18C...SO SEE NO REASON TO DISCOUNT PRESENT CHILLY LOW
TEMP FORECAST IN THE -7 TO +7F RANGE BY SUNDAY MORNING...SLIGHTLY
MILDER SOUTH. IN REGARD TO THE CHAMPLAIN LAKE EFFECT...EVOLVING
NORTHERLY TRAJECTORIES AND LAKE-850 HPA AIR TEMP DIFFERENCE NEAR
24C MORE THAN SUFFICIENT TO ALLOW PERIODIC SNOW SHOWERS/FLURRIES
TO CONTINUE OVERNIGHT TO THE SOUTH AND EAST OF THE LAKE. LIMITING
FACTORS INCLUDING SHALLOW BOUNDARY LAYER AND DRY AIR ADVECTION
SHOULD PRECLUDE ANYTHING SUBSTANTIAL HOWEVER. AGAIN...PRESENT FCST
HAS THIS COVERED SO OTHER THAN SKY ADJUSTMENTS NOTED ABOVE...NO
OTHER CHANGES NEEDED AT THIS TIME. ENJOY YOUR EVENING.
&&
.SHORT TERM /7 AM THIS MORNING THROUGH MONDAY NIGHT/...
AS OF 300 PM EST SATURDAY...MID/UPPER LEVEL RIDGE BUILDS ACROSS
OUR CWA AS SURFACE HIGH PRESSURE SHIFTS TOWARD EASTERN NEW
ENGLAND. GIVEN DEEP DRY LAYER AND PLENTY OF NVA FROM BUILDING
HGHTS...EXPECT MAINLY CLEAR SKIES WITH MAX TEMPS ON SUNDAY AROUND
TEN DEGREES BELOW NORMAL. TEMPS RETURN TO NEAR NORMAL BY SUNDAY
NIGHT AS 850 TEMPS SLOWLY WARM FROM THE NEGATIVE TEENS ON SUNDAY
TO NEGATIVE SINGLE DIGITS SUNDAY NIGHT. MONDAY WILL BEGIN DRY
WITH HIGH PRESSURE STILL IN PLAY...BUT BY LATE MONDAY...ANOTHER
SFC COLD FRNT APPROACHES OUR WESTERN CWA. WITH A GOOD RIBBON OF
850 TO 500MB MOISTURE AND STRONG SFC CONVERGENCE. THIS COMBINED
WITH STEEP 0 TO 2 KM AGL LAPSE RATES...AND POTENTIAL FOR SOME
LAKE MOISTURE INTERACTION...A BAND OF SNOW SHOWERS AND SNOW
SQUALLS LOOKS POSSIBLE LATE MONDAY AFTN INTO MONDAY NIGHT. WINDS
ALSO LOOK STRONG ON MONDAY AS 850 JET PEAKS AROUND 60 KTS DURING
THE AFTERNOON. HAVE CONTINUED WITH MENTION OF LIKELY POPS ACROSS
NORTHERN NY/VT BY 00Z...WITH A QUICK INCH OR TWO OF SNOW
POSSIBLE. TEMPERATURES WILL WARM BACK INTO THE 30S TO NEAR 40F ON
MONDAY...ASSOCIATED WITH SOUTHERLY FLOW AHEAD OF BOUNDARY.
OVERNIGHT MIN TEMPS WILL BE SLIGHTLY WARMER THAN NORMAL WITH
RESIDUAL CLOUDS FROM FRONT AND WINDS PROMOTING MIXING.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 247 PM EST SATURDAY...THE EXTENDED FCST PERIOD STARTS QUIET
AS SFC RIDGE OF HIGH PRESSURE CRESTS OVER NY AND NEW ENGLAND ON
TUESDAY. SHOULD SEE MOSTLY SUNNY SKIES TUESDAY WITH LIGHT WINDS
AND SEASONABLY TEMPS /HIGHS IN THE UPR 20S TO LOWER 30S/. RIDGE
AXIS SHIFTS EAST TUESDAY NIGHT WITH DEVELOPING S-SW WINDS. MAY
SEE TEMPS LEVELING OUT IN THE CHAMPLAIN AND ST. LAWRENCE VALLEYS
WITH INCREASED MIXING AND DEVELOPING WARM ADVECTION REGIME.
MODELS HAVE DIVERGED COMPARED TO PREVIOUS RUNS FOR POTENTIAL
PRECIPITATION SYSTEM WEDNESDAY INTO WEDNESDAY NIGHT. THE 12Z GFS
AND ECMWF SOLNS SHOW THAT THE NORTHERN AND SOUTHERN STREAMS ARE
NO LONGER IN PHASE...WITH SRN STREAM SHORTWAVE TROUGH PRECEDING
NORTHERN STREAM AS VORT MAX EMERGES FROM THE OHIO RIVER VALLEY.
THE 12Z GFS IS A BIT FASTER...WITH VORT PASSING THRU PA AND THEN
OFFSHORE SOUTH OF LONG ISLAND. THE BULK OF ASSOCIATED
PRECIPITATION REMAINS SOUTH OF THE NORTH COUNTRY AS WELL. HIGHEST
POPS WOULD OCCUR LATE TUESDAY NIGHT INTO WEDNESDAY. THE ECMWF IS
ABOUT 12 HRS SLOWER AND WARMER ALOFT...WITH 850MB TEMPS +5C AT
00Z THU. HAVE CUT BACK ON POPS TO 30-40 PERCENT...AND HAVE
INDICATED MIXED PRECIPITATION TYPES BASED. NOT EXPECTING A LOT OF
QPF AT THIS POINT BASED ON ABSENCE OF PHASING AND GFS TRACK. WILL
CONTINUE TO MONITOR...BUT SIGNIFICANT WEATHER IMPACTS LOOK LESS
LIKELY THAN THIS TIME YESTERDAY.
THE 12Z GFS MAINTAINS A MORE SIGNIFICANT UPPER TROUGH LATE NEXT
WEEK AND OFFERS A COLDER SOLN THU-FRI AS COMPARED TO THE ECMWF.
HAVE MADE SOME ADJUSTMENTS BETWEEN THE TWO MODELS...INDICATING
HIGHS MOSTLY IN THE 30S WITH LOWS IN THE 20S...SO SOMEWHAT ABOVE
CLIMO ON TEMPS. CAN`T RULE OUT SOME SNOW SHOWER ACTIVITY
THU/FRI...BUT OVERALL NO SIGNIFICANT WEATHER EXPECTED AT THIS
TIME.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
THROUGH 06Z MONDAY...MAINLY VFR CONDITIONS EXPECTED THROUGH THE
PERIOD...EXCEPT FOR POSSIBLE MVFR AT KBTV/KSLK THROUGH 12Z. PATCHY
BR POSSIBLE AT KSLK...WHILE CLOUDS ASSOCIATED WITH SNOW SHOWERS
OVER LAKE CHAMPLAIN MAY DRIFT OVER KBTV AT TIMES. OTHERWISE...
MAINLY CLEAR SKIES THROUGH SUNDAY...WITH INCREASING CLOUDS SUNDAY
NIGHT. WINDS LIGHT AND VARIABLE...THEN BECOMING SSW 5-10 KTS OVER
NORTHERN NY SUNDAY AFTERNOON AND OVER VT SUNDAY NIGHT.
OUTLOOK 06Z MONDAY THROUGH THURSDAY...HIGH PRESSURE BRINGS MAINLY
VFR CONDITIONS THRU 18Z MONDAY. COLD FRONT MONDAY AFTERNOON INTO
MONDAY NIGHT MAY BRING LOCALLY GUSTY W-NW WINDS TO 25 KTS AND
SCATTERED SNOW SHOWERS WITH A PERIOD OF MVFR OR BRIEF IFR
CONDITIONS. NEXT PRECIPITATION SYSTEM ARRIVES LATE TUESDAY NIGHT
INTO WEDNESDAY...THOUGH CURRENT INDICATIONS ARE THAT BULK OF
PRECIPITATION WILL SLIDE SOUTH OF THE NORTH COUNTRY. A PERIOD OF
SNOW OR MIXED PCPN IS EXPECTED TO BE LIGHT AT THIS TIME.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...NEILES
NEAR TERM...JMG
SHORT TERM...NEILES
LONG TERM...BANACOS
AVIATION...RJS/LOCONTO
AREA FORECAST DISCUSSION
NWS BISMARCK ND
1147 PM CST SAT DEC 17 2011
.DISCUSSION...CURRENT FORECAST REMAINS ON TRACK TONIGHT WITH
MOSTLY CLEAR SKIES...SCATTERED CIRRUS FILTERING THROUGH FROM
MONTANA AND SASKATCHEWAN INTO NORTH DAKOTA. MADE MINOR CHANGES TO
OVERNIGHT LOWS BY WARMING A COUPLE DEGREES IN THE SOUTHWEST PER
LATEST HOURLY TEMPS AND RUC DATA. MAIN THEME REST OF TONIGHT WILL
BE WATCHING A WARM FRONT NOW OVER WESTERN NORTH DAKOTA SLIDE EAST.
WARM AIR ADVECTION LOOKS TO CONTINUE THROUGH SUNDAY MORNING...THEN A
TRANSITION TO COLD AIR ADVECTION WILL COMMENCE FROM NORTHWEST TO
SOUTHEAST BETWEEN 18Z SUNDAY AND 03Z MONDAY AS A COLD FRONT SWEEPS
THROUGH. EXPECT DRY WEATHER...BUT BREEZY CONDITIONS DEVELOPING AS
THE FRONT MOVES THROUGH.
&&
.AVIATION...HIGH PRESSURE WILL REMAIN OVERHEAD TONIGHT...WHICH WILL
KEEP WEST TO SOUTHWEST WINDS AND VFR CONDITIONS THROUGH 12Z TOMORROW
MORNING. WINDS WILL START TO INCREASE AND SHIFT TO THE WEST TOMORROW
MORNING AS A LOW PRESSURE SYSTEM AND COLD FRONT APPROACHES THE REGION.
CEILINGS WILL START TO LOWER AFTER 18Z AS A MVFR CLOUD DECK SPREADS
FROM THE NORTHWEST TO SOUTHEAST AHEAD OF THE COLD FRONT.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KS
AVIATION....LTH
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
339 AM EST SUN DEC 18 2011
.SYNOPSIS...
HIGH PRESSURE TODAY INTO MONDAY. EAST/WEST FRONT DROPS SOUTH MONDAY
NIGHT...BECOMES STATIONARY BY TUESDAY MORNING IN NORTHERN WEST
VIRGINIA INTO CENTRAL OHIO...THEN CREEPS BACK NORTH IN AFTERNOON.
&&
.NEAR TERM /THROUGH TONIGHT/...
VORT MAX ALONG BACK EDGE OF H500 TROUGH SHOWING UP WELL ON WATER
VAPOR LOOP...NOW IN THE TRI-STATE AREA. RUC13 HAS A GOOD HANDLE ON
THIS...BRINGING THE LOBE EAST OF CRW BY 12Z...AND ACROSS THE
MOUNTAINS BY 15Z. BACK EDGE OF LIGHT SNOW WILL FOLLOW THIS...UNTIL
ONLY A FEW SCATTERED UPSLOPE SHSN REMAIN BY MIDMORNING. HAVE NOT
RECEIVED MANY SNOW REPORTS BUT EXPECT ACCUMULATIONS ARE GENERALLY AN
INCH OR LESS AT THIS POINT. FAVORABLE SNOW GROWTH CONDITIONS WILL BE
DIMINISHING AS MOISTURE IN THE DGZ DECREASES. ADDITIONAL MINOR
ACCUMULATION OF LESS THAN AN INCH IS POSSIBLE...MAINLY IN THE
NORTHERN MOUNTAINS...WITH A BIT OF AN UPSLOPE ASSIST. A FEW
FLURRIES MAY LINGER INTO EARLY AFTERNOON IN THE NORTHERN MOUNTAINS
BEFORE ENDING. CLOUDS WILL BE BREAKING IN THE WEST AS ANTICYCLONIC
FLOW TAKES HOLD.
SURFACE HIGH PRESSURE CROSSES BY TO OUR SOUTH THIS EVENING...AND
MOVES TOWARD THE CAROLINA COAST BY 12Z MONDAY. AFTER A CLEAR START
TO THE NIGHT...SOME MID AND HIGH CLOUDS WILL START SHOWING UP LATE
IN THE DEVELOPING SW RETURN FLOW. WARM ADVECTION IS FAIRLY GENTLE
OVERNIGHT AND STICKING WITH A NORMAL DIURNAL TEMPERATURE TREND FOR
NOW.
LEANED A BIT MORE TOWARD THE COOLER MAV TODAY...HAVING PERFORMED
BETTER YESTERDAY. WARMER MET LOOKS MORE REASONABLE TONIGHT IN THE
DEVELOPING WARM ADVECTION.
&&
.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
NO MAJOR CHANGES MADE TO MONDAY ON THIS SUNDAY MORNING GRAVEYARD
SHIFT. CLOUDS INCREASE ACROSS OUR WESTERN AND NORTHERN
COUNTIES...WITH SUNSHINE HOLDING THE LONGEST IN SOUTHWEST VIRGINIA
AND SOUTHEAST WEST VIRGINIA. POPS INCREASING QUICKLY ACROSS
SOUTHEAST OHIO DURING THE AFTERNOON.
HAVE LIKELY POPS FOR PCPN MONDAY NIGHT...MAINLY N OF HTS-CRW-EKN
LINE.
BASING THE FORECAST ON THE FRONT STILL SAGGING SOUTH MONDAY
NIGHT...REACHING NEAR A ROUTE 50 CORRIDOR BY 12Z TUESDAY BEFORE
TRYING TO LIFT SLOWLY BACK NORTH TUESDAY AFTERNOON...AHEAD OF
SURFACE LOW PRESSURE MOVING NORTHEAST UP THE OHIO RIVER VALLEY
TUESDAY NIGHT INTO WEDNESDAY.
FOR ABOUT A 6 HOUR WINDOW ON EITHER SIDE OF 12Z TUESDAY...WILL HAVE
THE POSSIBILITY OF A WINTRY MIXTURE OF RAIN...SNOW...SLEET...FROM
THE EKN VCNTY TO CKB-PKB AND NORTH OF UNI. FORECASTING THE SURFACE
TEMPERATURES IN THE 34/35 DEGREE NEIGHBORHOOD IN THAT TIME
INTERVAL FOR NORTHERN COUNTIES...SO DO NOT HAVE READINGS BELOW
FREEZING. OF COURSE...IN THE STRONG NORTH TO SOUTH GRADIENT...IF
FRONT SNEAKS A BIT FURTHER SOUTH...IT WOULD BE COLDER.
WILL HAVE STRATIFORM TYPE PRECIPITATION MONDAY AFTERNOON
THROUGH TUESDAY MORNING...THEN GO TO RAIN SHOWERS/CONVECTIVE TYPE
PRECIPITATION/ FOR TUESDAY AFTERNOON AND TUESDAY NIGHT. KEPT THE
CHANCE OF THUNDER BELOW 15 PCT FOR OUR SOUTHERN COUNTIES TUESDAY
NIGHT.
SURFACE FRONT LIKELY TO WHIP THROUGH DURING THE DAY ON
WEDNESDAY...SO INCREASED SURFACE WINDS THEN.
CURRENTLY...NO STRONG INDICATIONS FROM THE 00Z MODEL SOLUTIONS TO
ADD ANY WATER HAZARD FOR RAIN AMOUNTS.
TEMPERATURES WILL BE TOUGH THROUGH THIS ENTIRE PERIOD. TRIED TO STAY
ON THE MILD SIDE OF 00Z GFS MOS GUIDANCE FOR TUESDAY NIGHT...IN THE
WARM SECTOR AHEAD OF APPROACHING LOW.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
UNFORTUNATELY MODELS HAVE REVERTED BACK TO THEIR TIMING DIFF WITH
EJECTIONS OF SW UPR LOW...WITH 12Z ECWMF CONSIDERABLY SLOWER NOW.
WILL LEAN HEAVILY ON HPC WITH THIS SYS. ASSOCIATED SFC LOW LOOKS TO
TAKE A FAMILIAR TRACK THIS SEASON...THRU OH VALLEY. THIS WILL MEAN A
COLD FRONTAL PASSAGE SOMETIME ON WED WITH RA AND A TURN TO SEASONAL
TEMPS BEHIND IT FOR THU.
MORE ENERGY LOOKS TO DUMP BACK INTO SW CONUS...HELPING TO FORM
ANOTHER UPR LOW WHICH WILL TRY TO COME EAST LATE IN THE
PERIOD...WITH NORTHERN STREAM TRYING TO AMPLIFY ACROSS THE UPR
MIDWEST. THIS WILL HAVE TO BE MONITORED FOR SOME POTENTIAL PRE
CHRISTMAS MISCHIEF. AS OF NOW BL LOOKS WARM ENOUGH FOR RA.
&&
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
01Z SUNDAY THRU 00Z MONDAY...
UPPER DISTURBANCE ROTATES THROUGH OVERNIGHT. MVFR CIGS/VSBYS IN -SN
WITH OCCASIONAL IFR TO THE NORTH (PKB/CKB/EKN). NOT MUCH SNOW TO
THE SOUTH...BUT MVFR CIGS ARE EXPECTED TO DEVELOP FOR AT LEAST A FEW
HOURS. SYSTEM STARTS TO PULL AWAY AFTER 12Z WITH IMPROVING
CIG/VSBY...ALTHOUGH EKN WILL SEE MVFR LINGER FOR A FEW MORE HOURS.
SKIES WILL THEN CLEAR THIS AFTERNOON...WITH VFR FOR THE BALANCE OF
THE PERIOD.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z MONDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: TIMING AND INTENSITY OF SNOW COULD VARY ACROSS
THE NORTH.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE SUN 12/18/11
UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19
EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
CRW CONSISTENCY H M M M M H H H H H H H
HTS CONSISTENCY H M H H H H H M H H H H
BKW CONSISTENCY H M M H M M H M H H H H
EKN CONSISTENCY L L M M M M M M L M M H
PKB CONSISTENCY H H H H H M M H H H H H
CKB CONSISTENCY M M M M M M M L M L H H
AFTER 06Z MONDAY...
NO SIGNIFICANT AREAS OF IFR EXPECTED.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...30
AVIATION...CL
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1121 PM CST SAT DEC 17 2011
.SHORT TERM...TONIGHT
901 PM CST SAT DEC 17 2011
THE MAIN CHANGE FOR OVERNIGHT WITH THE FORECAST WAS TO ADD IN SOME
FOG MENTION ACROSS THE REGION.
LOW LEVEL STRATUS HAS CLEARED MUCH OF THE FORECAST AREA WITH THE
BACK EDGE OF IT RUNNING THROUGH TAYLOR/NORTHEAST CLARK DOWN TO
JUNEAU AND ADAMS COUNTY. WITH WESTERLY LOW LEVEL WINDS IN
PLACE...THESE CLOUDS SHOULD CONTINUE TO MARCH EASTWARD OVER THE
NEXT FEW HOURS.
WITH THE COMBINATION OF CLEARING AND WARMER LOW LEVEL AIR
STARTING TO ADVECT INTO THE REGION...18.01Z RUC SOUNDINGS FROM THE
REGION ARE SHOWING A STEEP INVERSION SETTING UP OFF OF THE SURFACE
UP TO AROUND 1KFT. WITH A WEAK SURFACE RIDGE COMING
THROUGH...WINDS HAVE/WILL DROP OFF TO JUST A FEW KNOTS BEFORE
COMING AROUND TO THE SOUTH AROUND DAYBREAK TOMORROW MORNING. WITH
DEW POINTS STILL IN THE MID 20S...ANY RADIATIONAL COOLING SHOULD
LEAD TO SMALL SURFACE DEW POINT DEPRESSIONS.
THESE CONDITIONS ARE EXPECTED TO LEAD TO SOME FOG DEVELOPMENT
OVERNIGHT WITH PLATTEVILLE ALREADY DROPPING DOWN TO 3/4SM. THE TWO
HINDRANCES TO THE FOG DEVELOPMENT IS WITH THE WINDS EXPECTED TO
PICK UP THROUGH THE MORNING ALONG WITH SOME CIRRUS MOVING IN FROM
THE WEST THAT MAY LIMIT RADIATIONAL COOLING. REGARDLESS...IT LOOKS
LIKE ENOUGH OF A CHANCE TO WARRANT PUTTING IN THE FORECAST AT THIS
TIME. WITH TEMPERATURES BELOW FREEZING...THERE COULD BE SOME SLICK
SPOTS THAT DEVELOP ON AREA ROADS THOUGH MANY OF THEM HAVE BEEN
TREATED FOR THE SNOW THAT FELL LAST NIGHT. THERE COULD ALSO BE
SOME HOAR FROST THAT DEVELOPS IN ANY AREAS THAT SEES THE DENSER
FOG. AT THIS POINT...NOT EXPECTING TO HAVE TO ISSUE A DENSE FOG
ADVISORY OVERNIGHT...BUT CONDITIONS WILL BE MONITORED.
.LONG TERM...TUESDAY THROUGH SATURDAY
217 PM CST SAT DEC 17 2011
GOOD AGREEMENT EARLY IN THE PERIOD BETWEEN THE MODELS THAT THE
SURFACE LOW TRACKING ALONG THE COLD FRONT WILL STAY WELL SOUTH OF
THE REGION KEEPING THE AREA DRY THROUGH THE MIDDLE OF THE WEEK.
AFTER THAT THERE ARE SOME DIFFERENCES THAT SHOW UP. THE 17.00Z
ECMWF SHOWS ANOTHER LOW GETTING CUT OFF OVER THE DESERT SOUTHWEST
WITH A PRETTY STRONG NORTHERN STREAM SHORT WAVE TROUGH COMING
ACROSS THE UPPER MIDWEST THURSDAY THROUGH FRIDAY. THE 17.12Z GFS
AND GEM ALSO SHOW A TROUGH INTO THE DESERT SOUTHWEST BUT DO NOT
INDICATE A CUT OFF LOW NOR DO THEY HAVE THE NORTHERN STREAM WAVE.
AS A RESULT...THE ECMWF IS THE ONLY MODEL SHOWING ANY
PRECIPITATION ACROSS THE REGION FOR THURSDAY AND THURSDAY NIGHT.
INTERESTINGLY...THE 17.12Z GFS ENSEMBLE DOES SHOW A LOW PROBABILITY
OF SOME PRECIPITATION THURSDAY SIMILAR TO THE ECMWF. WILL CARRY
JUST A SLIGHT CHANCE OF SOME PRECIPITATION ACROSS THE NORTH TO
HONOR THE ECMWF SOLUTION.
&&
.AVIATION...THROUGH 06Z MONDAY
1121 PM CST SAT DEC 17 2011
THE MAIN CONCERNS OVER THE NEXT 24 HOURS ARE WITH THE SHALLOW
GROUND FOG EARLY THIS MORNING AND ALSO WITH A POSSIBLE STRATUS
DECK THAT COULD FORM SUNDAY EVENING.
CURRENTLY...A WEAK RIDGE OF HIGH PRESSURE IS SET UP ACROSS THE
REGION WITH LIGHT WINDS AND MAINLY CLEAR SKIES OUTSIDE OF SOME
CIRRUS. WITH A FRESH SNOW PACK IN PLACE FROM SOUTHEAST MINNESOTA
INTO SOUTHWEST WISCONSIN...IDEAL RADIATIONAL COOLING CONDITIONS
ARE TAKING PLACE. THIS HAS CREATED A VERY SHARP SURFACE BASED
INVERSION THAT IS TRAPPING ANY LOW LEVEL MOISTURE UNDER IT.
VISIBILITY HAVE FOR THE MOST PART BEEN VFR ACROSS THE
REGION...THOUGH A FEW SPOTS HAVE QUICKLY DROPPED TO AROUND A MILE
SUCH AS PLATTEVILLE AND WATERLOO. THE POTENTIAL IS THERE FOR BOTH
RST AND LSE TO SEE SOME OF THESE DROPS THIS MORNING...SO HAVE PUT
IN A TEMPO GROUP FROM 8Z-12Z TO ACCOUNT FOR ANY VFR TO IFR DROPS.
WINDS PICK UP QUICKLY AROUND DAYBREAK AND SHOULD MIX OUT ANY
REMNANT FOG WITH GUSTS UP IN THE 18-22KT RANGE IN THE AFTERNOON.
WITH WARM TEMPERATURES ABOVE FREEZING TODAY...THE SNOW PACK IS
EXPECTED TO MELT AWAY TODAY AND ADD SOME MOISTURE TO THE BOUNDARY
LAYER. 18.00Z NAM FORECAST SOUNDINGS SHOW A SHALLOW SATURATED
LAYER FORMING THIS EVENING AND LASTING OVERNIGHT AS A COLD FRONT
APPROACHES THE REGION. AT THIS POINT...HAVE HINTED AT THIS
STRATUS DECK FORMING AROUND 00Z TONIGHT IN THE TAFS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
217 PM CST SAT DEC 17 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION...UPDATED
NWS CHICAGO/ROMEOVILLE IL
1000 AM CST SUN DEC 18 2011
.DISCUSSION...
959 AM CST
THE DENSE FOG CONTINUES TO SLOWLY DISSIPATE...WITH MOST PREVAILING
VISIBILITIES AT OR ABOVE ONE MILE. THE EXCEPTION IS NORTHWEST
INDIANA WHERE THE FOG/STRATUS SPREAD IN THE LATEST. THE FOG
SHOULD CONTINUE TO ABATE WITH INCREASING LOW-LEVEL SOUTHWEST WINDS
EASING THE INVERSION IN THE LOWEST FEW HUNDRED FEET. IT IS
INTERESTING TO NOTE HOW THIS FOG CORRELATED WITH THE LIGHT BUT
FRESH SNOW COVER FROM THE SATURDAY MORNING EVENT. THIS SNOW COVER
MAKES IT TRICKY FOR TEMPERATURES THIS AFTERNOON...AS IT AIDED IN
COOLING LAST NIGHT /DOWN TO 10 DEGREES IN ROCHELLE/. IT HELPED THE
ASSOCIATED DEPTH OF THE INVERSION WITH RUC DIAGNOSTIC SOUNDINGS
INDICATING AN 8C DEGREE CLIMB JUST 100MB /3000 FT OR SO/ FROM THE
SURFACE OVER LOCATIONS IN THE NORTHERN HALF OF THE FORECAST AREA.
THE NORMAL DIURNAL CLIMB AT ORD AND RFD ARE 14 AND 15 DEGREES
RESPECTIVELY. WITH MORNING FOG/STRATUS AT AND AROUND BOTH
LOCATIONS...WOULD NOT THINK WE WOULD CLIMB MUCH ABOVE THAT GIVEN
THE INVERSION STRENGTH. IT WILL LIKELY CLIMB EVEN LESS IN CHICAGO
WHERE THE CLOUDS RESIDED LONGER. BELIEVE THE RUC AND MOST RECENT
NAM RUN AT 12Z HAVE A GOOD HANDLE ON KEEPING TEMPERATURES COOLER
IN THE NORTHERN FORECAST AREA. HAVE TRENDED THAT ROUTE...CUTTING 3
TO 5 DEGREES OFF OR SO.
MTF
&&
.PREV DISCUSSION...
408 AM CST
HIGH PRESSURE CONTINUES TO BUILD INTO THE SOUTHEAST US THIS
MORNING. A STUBBORN STRATUS DECK THAT RESIDED OVER AREAS EAST OF
I-39 HAS FINALLY ERODED. HIGH CIRRUS CLOUDS ARE QUICKLY MOVING
SOUTHEAST INTO THE AREA...BUT IR IMAGERY INDICATES THE CLOUDS ARE
DISSIPATING AS THEY MOVE IN. EXPECTING CLEARING TO CONTINUE
THROUGH TODAY. WHILE MOST OF THE SNOWFALL FROM YESTERDAY HAS
ALREADY MELTED...THE CLEAR SKIES ARE ALLOWING TEMPS TO DROP
RAPIDLY. SOME LOCATIONS THAT HAVE SNOW ON THE GROUND MAY EVEN DIP
INTO THE TEENS BEFORE SUNRISE. AREAS OF FOG WILL CONTINUE TO
PERSIST AND BURN OFF AFTER SUNRISE. WITH PLENTY OF SUNSHINE
TOMORROW...TEMPS WILL RISE INTO THE LOW 40S TODAY.
CLOUDS BEGIN TO MOVE IN LATE TONIGHT AHEAD OF THE NEXT SYSTEM. IN
REGARDS TO THE NEXT SYSTEM...THE MODELS ARE BEGINNING TO SHOW A
SIMILAR SOLUTION AND FORECAST CONFIDENCE FOR THE TIMING OF THE
PRECIP IS MEDIUM. THE LOW MOVES FROM OKLAHOMA TUESDAY MORNING TO
DETROIT BY WEDNESDAY AFTERNOON. THIS PATH WOULD BRING A SWATH OF
PRECIPITATION INTO THE REGION. THE GFS WANTS TO PUSH THE PRECIP
FARTHER NORTH INTO CENTRAL WISCONSIN...WHILE THE ECMWF HAS THE
PRECIP ONLY REACHING SOUTHERN WISCONSIN. SINCE THE GFS SOLUTIONS
HAVE BEEN SLOWLY CONVERGING WITH THE STEADY ECMWF SOLUTION...WENT
AHEAD AND LIMITED THE NORTHERN EXTENT OF THE PRECIP. THAT BEING
SAID...CONFIDENCE IN THE FORECASTED PRECIP TYPE REMAINS LOW. LOOKING
AT MODEL SOUNDINGS...THE GFS WANTS TO WARM THE THERMAL PROFILE
TUESDAY...WHILE THE NAM WANTS TO COOL THE PROFILE. BOTH PROFILES
HAVE SURFACE TEMPS NEAR FREEZING.
PRECIP FROM THE LOW REACHES NORTHEASTERN IL AND NORTHWESTERN IN LATE
MONDAY INTO MONDAY NIGHT AS RAIN. THE RAIN WILL BEGIN SOUTH OF I-80
AND SLOWLY INCH NORTHWARD THROUGH TUESDAY. AREAS SOUTH OF I-80 WILL
LIKELY SEE ALL RAIN AS THEY WILL BE CLOSEST TO THE LOW ITSELF. A
RAIN/SNOW MIX WILL FALL NORTH OF I-80 ON TUESDAY. SINCE THIS LOW IS
COMING OUT OF THE SOUTH CENTRAL US...THERE IS NO GOOD COLD AIR PUSH
ASSOCIATED WITH IT. THEREFORE...AS THE LOW PULLS AWAY TUESDAY NIGHT
AND WEDNESDAY...LINGERING PRECIP WILL FALL AS A RAIN/SNOW MIX OR AS
A COLD RAIN. DAYTIME HIGH TEMPS TUESDAY THROUGH THURSDAY WILL BE IN
THE MID 30S TO LOW 40S. LOW TEMPS WILL BE IN THE UPPER 20S TO LOW
30S.
NUMEROUS UPPER LEVEL ENERGY STREAMERS PASS THROUGH THE REGION
THURSDAY AND FRIDAY...RESULTING IN SLIGHT CHANCES OF SNOW. NONE OF
THESE CHANCES LOOK LIKE THEY WILL PRODUCE SIGNIFICANT SNOWFALL.
HIGH PRESSURE MOVES IN FROM THE PLAINS ON FRIDAY.
JEE
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 15Z...
* BAND OF IFR/LIFR STRATUS AND FOG STILL OVER LOCAL TERMINALS AT
MID MORNING.
* TIMING OF IMPROVEMENT TO VFR TODAY.
* INCREASING SSW TO SW WINDS TO MODERATE SPEEDS OF 15-20 KT THIS
AFTERNOON.
* MVFR CEILINGS POSSIBLE MONDAY MORNING AS A TROUGH CROSSES THE AREA.
TRS
//DISCUSSION...UPDATED 15Z...
HAVE DELAYED IMPROVEMENT OF FLIGHT CATEGORIES BACK UP TO VFR A
COUPLE HOURS BUT ALL SHOULD BE VFR BY 18Z. RISING OF SUN AND WEAK
SURFACE HEATING ALONG WITH GRADUALLY INCREASING SSW-SW WINDS
HELPING TO MIX OUT THE STRATUS AND FOG THIS MORNING BUT THE STREAK
OF CIRRUS THAT PASSED RIGHT OVER THE LOW DECK PROBABLY DELAYED
THE QUICKER IMPROVEMENT THAT WAS ANTICIPATED EARLIER THIS MORNING.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 15Z...
* MEDIUM TO HIGH CONFIDENCE LIFR AND IFR VISIBILITIES AND CEILINGS
WILL QUICKLY IMPROVE TO VFR BY 18Z.
* HIGH CONFIDENCE IN WIND FORECASTS.
* MEDIUM CONFIDENCE IN MVFR CEILINGS SOMETIME MONDAY MORNING.
MDB/TRS
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF
ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN AND SNOW. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
SATURDAY...VFR.
MDB
&&
.MARINE...
315 AM CST
...SOUTHWEST GALES DEVELOP THIS AFTERNOON...
A SERIES OF RIDGES AND TROUGHS DOT THE EARLY MORNING WEATHER MAP.
HIGH PRESSURE EXTENDS FROM EASTERN QUEBEC INTO NORTHERN NEW ENGLAND
AND IS WORKING TOWARDS THE ATLANTIC WHILE LOW PRESSURE OVER HUDSON
BAY MOVES EASTWARD DRAGGING A TROUGH ACROSS LAKE HURON AND SOUTHERN
ONTARIO. WEAK RIDGING IS POSITIONED TO THE WEST OF THE TROUGH AND
WILL CREST OVER LAKE MICHIGAN THIS MORNING. THE MOST NOTABLE FEATURE
IS LOW PRESSURE MOVING FROM CENTRAL SASKATCHEWAN INTO CENTRAL
MANITOBA. THIS LOW WILL DEEPEN AS IT MOVES EAST TODAY TIGHTENING THE
PRESSURE GRADIENT ACROSS THE UPPER LAKES THIS AFTERNOON. THE LOW WILL
DRAG A TROUGH ACROSS THE LAKE EARLY MONDAY MORNING WHICH WILL SHIFT
WINDS TO NORTHWESTERLY. IN TERMS OF TRENDS...WINDS WILL BEGIN TO
SLACKEN SOMEWHAT THIS MORNING AS THE RIDGE MOVES ACROSS BUT THEN
QUICKLY PICK UP FROM THE SOUTHWEST THIS AFTERNOON AS THE DEEPENING
LOW MOVES INTO WESTERN ONTARIO AND JUST NORTH OF LAKE SUPERIOR BY
EVENING. AM EXPECTING SPEEDS TO REACH GALE FORCE TO 40 KT BY LATE
AFTERNOON NORTH AND CONTINUE THROUGH THE EVENING THEN SLOWLY BEGIN
TO DIMINISH TO 35 KT GALES AFTER MIDNIGHT WITH A REDUCTION TO
BELOW GALE TOWARD DAYBREAK. STRONGEST SPEEDS WILL BE ACROSS THE
NORTHERN HALF TO TWO-THIRDS OF THE LAKE WITH SPEEDS A FEW KNOTS
LOWER AND SLIGHTLY SLOWER IN ARRIVING ACROSS THE SOUTH. SPEEDS
WILL LIKELY REMAIN IN THE 20 TO 25 KT RANGE FOR MOST OF MONDAY AS
THE PRESSURE GRADIENT REMAINS STRONG BETWEEN THE DEPARTING LOW AND
A STRONG HIGH THAT WILL BE MOVING IN FROM THE WEST. WINDS WILL
TURN TO THE NORTH BY AFTERNOON THEN PROBABLY TURN MORE NORTHEAST
AS SPEEDS DROP OFF MONDAY EVENING AS THE HIGH REACHES THE LAKE.
LOW PRESSURE WILL DEVELOP ACROSS NORTHERN TEXAS MONDAY NIGHT AND
LIFT NORTHEASTWARD INTO EAST-CENTRAL ILLINOIS TUESDAY NIGHT WHILE
ANOTHER LOW MOVES ACROSS HUDSON BAY. RIDGING WILL REMAIN ACROSS THE
LAKE BUT THE NORTHERN SYSTEM LOOKS TO PASS CLOSE ENOUGH TO BRING
INCREASING SOUTH TO SOUTHWEST WINDS ACROSS THE FAR NORTHERN PART OF
THE LAKE TUESDAY AFTERNOON. THE GRADIENT WILL REMAIN WEAKER SOUTH
BUT A MORE SOUTHEASTERLY WIND DIRECTION SHOULD PREVAIL AHEAD OF THE
APPROACHING LOW. THE LOW WILL LIKELY PASS JUST TO THE SOUTHEAST OF
THE LAKE WEDNESDAY ALLOWING WINDS TO TURN NORTH OR NORTHEAST BEFORE
TURNING NORTHWEST WEDNESDAY EVENING. THE PATTERN REMAINS ACTIVE FROM
THAT POINT ONWARD WITH A SERIES OF HIGHS AND LOWS BRINGING UPS AND
DOWNS TO THE WIND SPEED FORECAST INTO NEXT WEEKEND.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
740 AM EST SUN DEC 18 2011
UPDATED AVIATION DISCUSSION FOR THE 12Z TAFS
.DISCUSSION /TODAY THROUGH SATURDAY/... ISSUED AT 431 AM EST
QUIET MORNING ACROSS UPPER MICHIGAN...AS SFC RIDGE IS SLIDING ACROSS
THE UPPER GREAT LKS REGION. PERSISTENT AREA OF LOW CLOUDS EARLY THIS
MORNING ON SATELLITE...STRETCHING SW INTO NRN WI. MOST MODELS HAVING
A DIFFICULT TIME WITH THEM...BUT RUC SEEMS TO HAVE A DECENT HANDLE
ON LOW CLOUDS ON 0.5-1KM RH FIELDS...SO HAVE FOLLOWED THAT FOR THE
EXIT OF THE MVFR CLOUDS THIS MORNING. THINK THEY WILL LIKELY PERSIST
THROUGH THE FIRST PART OF THE MORNING UNTIL LLVL WINDS SHIFT TO THE
SW AND PUSH THEM NE OF THE AREA.
1002MB LOW PRESSURE SYSTEM CURRENTLY LOCATED JUST NW OF LK WINNIPEG
WILL SLOWLY DEEPEN THROUGH THE DAY...AS A NRN STREAM SHORTWAVE
AMPLIFIES OVER SOUTHERN CANADA THROUGH THE DAY. BY 00Z...SHOULD SEE
A 999MB LOW LOCATED JUST TO THE N OF LK SUPERIOR. STRONG H850-500
WAA OVER SRN CANADA /AND PRODUCING A FEW -SHSN E OF LK WINNIPEG/
WILL SHIFT ESE THROUGH SRN ONTARIO AND FAR NRN LK SUPERIOR FROM MID
MORNING THROUGH THE REST OF THE DAY. WITH THE BEST MOISTURE LOCATED
IN THIS AREA...EXPECT THE PCPN TO STAY N OF THE LAND AREAS. HEADING
FARTHER S OVER UPPER MI...DRY AIR BELOW H750 SHOULD KEEP ANY PCPN
COMING OUT OF THE MID CLOUDS FROM REACHING THE SFC FROM MID MORNING
THROUGH EARLY AFTN. LIKELY WON/T SEE MUCH SUN THROUGH THE MORNING
HOURS WITH THE LINGERING LLVL CLOUDS THAT WILL BE OVERRUN BY THE
INCOMING MID CLOUDS. DRY SLOT BEGINS TO MOVE OVER THE AREA AROUND
MID AFTN AND MAY LEAD TO SOME CLEARING...ESPECIALLY OVER THE W HALF.
WITH THE LOW INTENSIFYING AS IT MOVES N OF THE AREA...WILL LIKELY
SEE SOME GUSTY SW WINDS THIS AFTN. STRENGTHENING INVERSION AROUND
H900 WILL LIMIT ACCESS TO THE LLVL JET AROUND 45KTS. BUT TIGHTENING
PRESS GRADIENT WILL STILL LEAD TO GUSTS IN THE 20-30KT
RANGE...ESPECIALLY IN THE SW WIND DOWNSLOPE AREAS NEAR LK SUPERIOR.
THE INVERSION AND CLEARING THIS AFTN MAKES TEMPS TRICKY...AS THERE
WILL BE A LIMITED PERIOD FOR SUNSHINE HELP MIX HIGHER ALOFT. THOUGH
PREVIOUS HIGHS LOOKED GOOD AND ONLY MADE MINOR TWEAKS. WITH THE WARM
START AND SSWRLY FLOW...EXPECT THE HIGHS TO BE IN THE UPPER 30S AND
MAYBE AN ISOLATED 40 OVER THE WRN CWA /WHERE WARMER AIR SURGES INTO
THE AREA AND THERE IS A LONGER PERIOD OF CLEAR SKIES/...ALONG WITH
DOWNSLOPE AREAS NEAR LK SUPERIOR.
SFC LOW WILL QUICKLY DEEPEN TO 993MB THROUGH THE NIGHT AS IT SHIFTS
JUST SE OF JAMES BAY BY 12Z. DRY SLOT WILL STILL BE OVER THE AREA
AND PROVIDE A CLEAR BUT BREEZY EVENING. SFC TROUGH/COLD FRONT WILL
THEN SLIDE SE THROUGH THE CWA AFTER MIDNIGHT AND BRING A CHANCE FOR
PCPN TO AREAS NEAR LK SUPERIOR. NOT OVERLY IMPRESSED WITH
FORCING/MOISTURE ALONG THE FRONT...SO HAVE WENT WITH SLIGHT
CHANCES...EXCEPT FOR FAVORABLE UPSLOPE NW WIND LOCATIONS OVER THE
WRN CWA. P-TYPE WILL BE SNOW INITIALLY WITH THE PASSAGE OF THE
FRONT...BUT COULD BE SOME FZDZ WITH THE UPSLOPE FLOW OVER THE WRN
U.P. SOUNDINGS SHOW INCREASING LLVL LAPSE RATES OVER THE WEST AFTER
06Z TONIGHT BELOW THE 3-4KFT INVERSION. WITH NEAR SFC DRY AIR
PUTTING CLOUD BASES AROUND 1.5-2.5KFT...OVERALL CLOUD DEPTH WILL BE
FAIRLY SHALLOW. IN ADDITION...CLOUD TOPS ARE ONLY AROUND -7 TO -8C
AFTER THE FRONT MOVES THROUGH...LIMITING ICE CRYSTALS IN THE CLOUDS.
THEREFORE...HAVE ADDED A MENTION OF FZDZ OVER THE W AFTER 09Z. OVER
THE E...WARMER TEMPS WILL LIKELY LEAD TO MORE OF A DZ/SN POTENTIAL
LATE TONIGHT.
WITH CONTINUED H925-850 MOISTURE AND H850 TEMPS FALLING TOWARDS -10C
BY MID MORNING...EXPECT A PERIOD OF LK ENHANCED PCPN DURING THE
MORNING HOURS. TEMPS SHOULD FALL ENOUGH MON MORN OVER THE W TO
PRODUCE ENOUGH ICE CRYSTALS FOR ANY LINGERING SHOWERS TO BE ALL
SNOW. THERE COULD BE A SLIGHT LAG OVER THE E NEAR LK SUPERIOR FOR
THE FIRST COUPLE OF HOURS AND MENTIONED A -SHSN/FZDZ INITIALLY IN
THE MORNING. LAKE EFFECT POTENTIAL QUICKLY DIMINISHES HEADING INTO
THE AFTN...AS H850-700 SUBSIDENCE INCREASES AND LLVL MOISTURE
DEPARTS. IN ADDITION...MODELS SHOWING INVERSION HEIGHTS AT OR BELOW
3KFT IN THE AFTN AND LOCAL/NATIONAL HIRES WRF RUNS NOT SHOWING ANY
PCPN. WITH ALL THE NEGATIVES...HAVE TAPERED BACK EXISTING POPS IN
THE AFTN...BUT DID LEAVE SOME LOW CHANCES OVER THE E FOR NNW WIND
FAVORED LOCATIONS WHERE THE LONGER FETCH MAY HELP KEEP PCPN GOING.
HIGH PRESSURE RIDGE WILL BUILD OVER THE AREA ON MON NIGHT...BRINGING
AN END TO ANY LINGERING LES EARLY IN THE EVENING. WITH LIGHT WINDS
AND CLEAR SKIES UNDER THE HIGH PRESSURE RIDGE...EXPECT A GOOD
RADIATIONAL COOLING NIGHT. PWAT VALUES /AROUND 0.1 INCH OR 35
PERCENT OF NORMAL/ SUPPORT GOING ON THE LOW END OF GUIDANCE...AND
HAVE LOWS FALLING INTO THE SINGLE DIGITS ABOVE ZERO.
NRN STREAM OF THE JET WILL REMAIN N OF THE AREA FOR TUES/WED...WHILE
THE SRN STREAM IS LOCATED OVER THE SRN CONUS. THIS LEAVES THE AREA
WITH FAIRLY QUIET AND SEASONABLE CONDITIONS. SFC RIDGE WILL BE OVER
THE CWA AT THE START OF TUES...WITH ANOTHER SHORTWAVE MOVING THROUGH
SRN CANADA IN THE NRN STREAM. AS WITH THE SYSTEM TODAY...MAIN
ENERGY/MOISTURE WILL BE JUST TO THE N OF THE AREA...BRUSHING NRN LK
SUPERIOR. AS THIS QUICKLY MOVES E TUES EVENING...WEAK SFC RIDGE WILL
LIKELY BUILD BACK OVER THE AREA FOR TUES NIGHT INTO WED MORNING.
SEASONABLE TEMPS WILL CONTINUE...ALTHOUGH THE GUSTY WINDS AT TIMES
WILL MAKE IT FEEL A LITTLE COOLER.
DIFFERENCES START TO APPEAR IN THE EXTENDED MODELS WED INTO THURS
NIGHT WITH THE HANDLING OF THE EASTWARD MOVING UPPER LOW IN THE SRN
STREAM THAT WILL BE OVER THE CNTRL ROCKIES ON WED. ANOTHER NRN
STREAM TROUGH WILL BE DROPPING THROUGH THE CANADIAN ROCKIES AT THIS
TIME AND THEY WILL TRY TO MERGE THE NRN/SRN STREAMS OVER THE GREAT
LAKES REGION. 00Z RUNS OF THE GFS/ECMWF/GEM HAVE SPED UP THE EXITING
SRN STREAM WAVE...PUSHING IT THROUGH THE LOWER GREAT LKS AND OHIO
VALLEY BY 06Z THURS. AT THAT TIME...NRN STREAM WAVE WILL BE
APPROACHING THE UPPER GREAT LKS AND PASS THROUGH ON THURS.
THUS...WILL CONTINUE TO MENTION PCPN CHANCES DURING THAT
TIME...MAINLY DUE TO THE APPROACHING NRN STREAM WAVE.
BEHIND THESE DISTURBANCES...COLDER H850 TEMPS /TOWARDS -14C/ WILL
FILTER OVER THE UPPER GREAT LKS THURS INTO FRI AND LEAD TO LES UNDER
NWRLY FLOW. BEST CHANCES LOOK TO BE THURS INTO FRI MORNING WITH
ADDITIONAL MOISTURE FROM THE UPPER TROUGH...BEFORE SFC HIGH BEGINS
TO PULL DRIER AIR AND WARMER TEMPS ALOFT IN ON FRI AFTN. HAVE STUCK
WITH LOW CHANCES FOR NOW...BUT MAY NEED TO BUMP UP POPS IF
CONDITIONS REMAIN FAVORABLE. SWRLY FLOW WILL REDEVELOP FRI NIGHT AND
CONTINUE INTO SAT...AHEAD OF THE NEXT NRN STREAM SHORTWAVE TO AFFECT
THE AREA LATE SAT.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
STRATUS DECK WITH MVFR CIGS WILL CONTINUE TO LIFT NE THIS MORNING AS
SW FLOW INCREASES AHEAD OF AN APPROACHING COLD FRONT. LOW CLOUDS
CLEARED KIWD A FEW HRS AGO...AND KCMX/KSAW SHOULD SEE THE STRATUS
DEPART MID TO LATE MORNING. THEREAFTER...VFR CONDITIONS WILL PREVAIL
INTO THE EVENING HRS AT ALL 3 TAF SITES. TIGHTENING PRES GRADIENT
WILL LEAD TO GUSTY SW WINDS INTO THE 20-25KT RANGE THIS AFTN.
THEN...THERE SHOULD BE ENOUGH DECOUPLING THIS EVENING TO RESULT IN
LLWS AS LOW-LEVEL JET WILL STILL BE OVER THE AREA. AFTER COLD FRONT
PASSAGE TONIGHT...MODELS ARE INDICATING A GOOD PUSH OF LOW-LEVEL
MOISTURE. THERE ARE LOW CLOUDS WELL UPSTREAM BEHIND FRONT...SO OPTED
TO DROP CIGS TO LOW MVFR LATER TONIGHT. CERTAINLY POSSIBLE THAT CIGS
COULD DROP TO IFR...ESPECIALLY AT KCMX/KIWD DUE TO UPSLOPING NW WIND.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
AS PRES GRADIENT TIGHTENS WITH LOW PRES MOVING ACROSS MANITOBA INTO
NRN ONTARIO...SW WINDS WILL BE ON THE INCREASE TODAY. ALTHOUGH
INVERSION WILL LIMIT NEAR SFC WINDS FROM BEING STRONGER...AREA OF
PRES FALLS ON THE ORDER OF 6MB/3HR PASSING OVER AND JUST N OF LAKE
SUPERIOR WILL WORK TO BOOST WINDS TO GALE FORCE OVER CNTRL AND ERN
LAKE SUPERIOR LATER THIS AFTERNOON AND TONIGHT. HIGHEST WINDS...
PERHAPS GUSTING TO AROUND 40KT...WILL LIKELY OCCUR OVER EASTERN
PORTIONS OF THE LAKE FROM STANNARD ROCK EASTWARD DUE TO FAVORABLE
POSITIONING OF PRES FALLS. AREA AROUND GRAND MARAIS SHOULD BE
ESPECIALLY FAVORED FOR STRONGER WINDS FOR A FEW HRS THIS EVENING.
AFTER COLD FRONTAL PASSAGE TONIGHT ASSOCIATED WITH THE LOW PRES
SYSTEM...NW WINDS WILL PROBABLY GUST TO AROUND 35KT OVER THE E HALF
OF THE LAKE INTO MON MORNING. WINDS WILL DIMINISH W TO E MON
AFTN/NIGHT AS HIGH PRES SYSTEM QUICKLY PASSES ACROSS THE GREAT
LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL PROBABLY
BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR. SW
WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE
FOR STRONGEST WINDS TUE. GALES WILL END TUE NIGHT AS PRES GRADIENT
WEAKENS. WINDS WILL BE BLO 30KT FOR WED/THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING FROM 3 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ266-267.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST MONDAY FOR
LSZ264.
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST MONDAY FOR
LSZ263.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR
LMZ248-250.
&&
$$
DISCUSSION...SRF
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
540 AM CST SUN DEC 18 2011
UPDATED TO ADD THE 12Z AVIATION DISCUSSION BELOW...
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES CONTINUE TO
SHOW A CUTOFF UPPER LOW OVER THE SOUTHWEST US WITH A BROAD RIDGE
OVERTOP OF IT EXTENDING FROM THE PACIFIC NORTHWEST COAST INTO THE
UPPER MIDWEST. THE DEEP UPPER LOW NORTH OF HUDSON BAY HAS MOVED
LITTLE OF LATE... AND SHOW NO SIGNS OF GOING ANYWHERE THROUGH AT
LEAST THE NEXT 10 DAYS ON THE GFS... ECMWF... AND THEIR RESPECTIVE
ENSEMBLES. IN THE BIG PICTURE... THIS SUGGESTS CONDITIONS IN OUR
NECK OF THE WOOD SHOULDN/T CHANGE TOO MUCH THROUGH AT LEAST THE
NEXT WEEK OR TWO... WITH NEAR TO ABOVE NORMAL TEMPERATURES
PREDOMINATING AS WEST TO NORTHWEST MID-UPPER LEVEL FLOW CONTINUES
TO BRING SYSTEMS OF PACIFIC ORIGIN INTO OUR AREA. WE WILL CONTINUE
TO SEE FAIRLY FREQUENT COLD FRONTAL PASSAGES... BUT NONE LOOK TO
BRING ANY TRUE ARCTIC AIR INTO THE REGION... AND INSTEAD WILL
SIMPLY BRING TEMPERATURES DOWN TO NEAR OR PERHAPS SLIGHTLY BELOW
NORMAL FOR BRIEF PERIODS OF TIME AS THEY MOVE THROUGH. AS FAR AS
PRECIPITATION GOES... THE PRESENT LONG WAVE PATTERN IS NOT
CONDUCIVE TO US SEEING MUCH... WITH MINIMAL MOISTURE RETURN AHEAD
OF INDIVIDUAL SHORTWAVES... AND THE DEEPENING OF SYSTEMS OCCURRING
SOUTH AND EAST OF OUR AREA AS THEY MOVE INTO THE MEAN LONG WAVE
TROUGH POSITION.
ROBUST WARM ADVECTION WILL OCCUR ACROSS THE AREA TODAY... WITH
TEMPERATURES SOARING INTO THE 40S IN MOST LOCATIONS... AND LIKELY
ECLIPSING THE 50 DEGREE MARK OVER WEST CENTRAL AND SOUTHWEST
MINNESOTA. IT ISN/T TOO OFTEN WE SEE 850MB TEMPERATURES IN EXCESS
OF 8C... BUT THAT LOOKS TO BE THE CASE TODAY OVER THE SOUTHERN
PART OF THE STATE. WE CERTAINLY WON/T MIX TO 850MB... BUT EVEN
MIXING THROUGH 950MB WILL ALLOW TEMPERATURES TO CLIMB TO AOA 50
DEGREES OVER MANY AREAS SOUTH AND WEST OF THE TWIN CITIES.
WOULDN/T BE SHOCKED IF THE TWIN CITIES MANAGES TO GET CLOSE TO 50
DEGREES DEPENDING UPON HOW WELL THINGS MIX OR IF WE/RE ABLE TO
ADVECT SOME OF THE WARMER UPSTREAM READINGS INTO THE AREA DURING
THE AFTERNOON HOURS. JUST NUDGED READINGS UP SLIGHTLY OVER
PREVIOUSLY FORECAST VALUES... BUT IT WILL CERTAINLY BE SOMETHING
TO KEEP AN EYE ON TODAY. LOW PRESSURE ASSOCIATED WITH THE
SHORTWAVE CURRENTLY SEEN MOVING INTO ALBERTA WILL PASS BY NORTH OF
THE STATE THIS EVENING... DRAGGING A COLD FRONT ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. THIS WILL COOL THINGS DOWN
TO ABOUT WHERE THEY SHOULD BE FOR MONDAY. A FEW FLURRIES COULD BE
SEEN BEHIND THE FRONT DEPENDING UPON HOW DEEP THE MOISTURE IS
BENEATH THE SUBSIDENCE INVERSION AND IF CYCLONIC BOUNDARY LAYER
FLOW IS ABLE TO LINGER. AT THIS POINT... THE CHANCES LOOK MINIMAL
AND IT WOULD ONLY BE SCATTERED FLURRIES AT BEST... SO LEFT IT OUT
OF THE FORECAST.
HIGH PRESSURE WILL BUILD ACROSS THE REGION MONDAY AFTER THROUGH
MONDAY NIGHT... AS THE 850-700MB THERMAL TROUGH MOVES ACROSS THE
AREA AND WEAKENS. THIS WILL BRING WHAT WILL FEEL LIKE A CHILLY
NIGHT MONDAY NIGHT... ALTHOUGH READINGS STILL LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL. WEAK WARM ADVECTION LOOKS TO BE IN PLACE
ACROSS THE REGION TUESDAY AND TUESDAY NIGHT AS A SHORTWAVE AND
SURFACE LOW MOVE BY WELL NORTH OF THE US/CANADA BORDER... AND A
SURFACE LOW ASSOCIATED WITH THE CUTOFF LOW CURRENTLY OVER THE
SOUTHWEST MOVES OUT OF THE SOUTHERN PLAINS TO THE OHIO VALLEY. WE
WILL FIND OURSELVES NESTLED BETWEEN THESE FEATURES... WITH BENIGN
WEATHER IN PLACE. A SLOWLY MOVING COLD FRONT WILL DROP SOUTH
THROUGH THE REGION WEDNESDAY INTO THURSDAY. THERE ARE SOME HINTS
WE COULD SEE MOISTURE POOL SUFFICIENTLY ALONG THIS BAROCLINIC ZONE
TO GET SOME PCPN DEPENDING UPON WHEN THE UPSTREAM SHORTWAVE
DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA IS ABLE TO CATCH UP
WITH IT. GIVEN UNCERTAINTIES IN NOT ONLY IF SOME PCPN WILL BE
SQUEEZED OUT... BUT WHEN AND WHERE IT MIGHT OCCUR... CHOSE TO
LEAVE PCPN OUT OF THE FORECAST IN THE WEDNESDAY TO THURSDAY TIME
FRAME... BUT FEEL THERE IS AT LEAST A CHANCE FOR SOME FLURRIES OF
VERY LIGHT SNOW DURING THAT PERIOD WHICH MAY GET INCLUDED AS WE
GET CLOSER TO THAT TIME PERIOD. THE MEDIUM RANGE GUIDANCE BECOMES
QUITE MUDDY IN ITS AGREEMENT BY WEEK/S END... WITH THE
DETERMINISTIC GFS AND ECMWF DIFFERING BY 15-20MB IN SURFACE
PRESSURES OVER OUR AREA BY FRIDAY AS THE GFS CLOSES OFF A SURFACE
LOW IN THE SAME AREA WHERE THE ECMWF SUGGESTS A FAIRLY POTENT
RIDGE. THE ECMWF SOLUTION WOULDN/T SUPPORT ANY PCPN... AND THE GFS
WOULD SUGGEST VERY LITTLE... SO THE PATH OF LEAST RESISTANCE AT
THIS POINT IS SIMPLY TO KEEP THINGS DRY.
&&
.AVIATION... /12Z TAF ISSUANCE/
WARM FRONT ADVANCING EAST INTO THE LOWER GREAT LAKES REGION LATER
TODAY. ONLY SOME HIGH CLOUDS ANTICIPATED OVER THE TAF SITES TODAY.
SURFACE WINDS INCREASING FROM THE SOUTH-SOUTHWEST 10-15 KT WITH
GUSTS BETWEEN 18-23 KT BY LATE MORNING. COLD FRONT WILL DROP SOUTH
INTO CENTRAL MN EARLY TONIGHT. THE FRONT WILL CONTINUE TO TREK SOUTH
OVER THE LOWER GREAT LAKES INTO THE CENTRAL PLAINS BY DAYBREAK
MONDAY. SURFACE OBSERVATION SHOWED SOME CEILING ROUGHLY BETWEEN
1000-3000 FEET AGL NEAR LAKE WINNEPEG. RESIDUAL MOISTURE ASSOCIATED
WITH THESE CLOUDS/CEILINGS SHOULD FLOW SOUTHEAST INTO MINNESOTA
OVERNIGHT. THE BIG QUESTION...IS IF THESE CLOUDS WILL BECOME A
CEILING OVERNIGHT. WL BRING SOME SCATTERED CLOUDS BETWEEN 1000-2000
FEET AGL OVER THE TAF SITES EARLY MONDAY MORNING.
KMSP...VFR CONDITIONS WILL REMAIN VFR THROUGH THE BULK OF THE
PERIOD. SOME LOWER CLOUDS WILL SNEAK DOWN OUT OF CANADA LATER THIS
EVENING AND OVERNIGHT. SURFACE WINDS SOUTHWEST AND INCREASING TO 10
TO 20 KT. SOME PATCHY OR LOW CLOUDS BETWEEN 1500-2000 FEET AGL
DEVELOPING AFTER MIDNIGHT TONIGHT.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/JM
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
550 AM EST SUN DEC 18 2011
.SYNOPSIS...
HIGH PRESSURE TODAY INTO MONDAY. EAST/WEST FRONT DROPS SOUTH MONDAY
NIGHT...BECOMES STATIONARY BY TUESDAY MORNING IN NORTHERN WEST
VIRGINIA INTO CENTRAL OHIO...THEN CREEPS BACK NORTH IN AFTERNOON.
&&
.NEAR TERM /THROUGH TONIGHT/...
NO MAJOR CHANGES AT 545 AM.
PREVIOUS DISCUSSION...
VORT MAX ALONG BACK EDGE OF H500 TROUGH SHOWING UP WELL ON WATER
VAPOR LOOP...NOW IN THE TRI-STATE AREA. RUC13 HAS A GOOD HANDLE ON
THIS...BRINGING THE LOBE EAST OF CRW BY 12Z...AND ACROSS THE
MOUNTAINS BY 15Z. BACK EDGE OF LIGHT SNOW WILL FOLLOW THIS...UNTIL
ONLY A FEW SCATTERED UPSLOPE SHSN REMAIN BY MIDMORNING. HAVE NOT
RECEIVED MANY SNOW REPORTS BUT EXPECT ACCUMULATIONS ARE GENERALLY AN
INCH OR LESS AT THIS POINT. FAVORABLE SNOW GROWTH CONDITIONS WILL BE
DIMINISHING AS MOISTURE IN THE DGZ DECREASES. ADDITIONAL MINOR
ACCUMULATION OF LESS THAN AN INCH IS POSSIBLE...MAINLY IN THE
NORTHERN MOUNTAINS...WITH A BIT OF AN UPSLOPE ASSIST. A FEW
FLURRIES MAY LINGER INTO EARLY AFTERNOON IN THE NORTHERN MOUNTAINS
BEFORE ENDING. CLOUDS WILL BE BREAKING IN THE WEST AS ANTICYCLONIC
FLOW TAKES HOLD.
SURFACE HIGH PRESSURE CROSSES BY TO OUR SOUTH THIS EVENING...AND
MOVES TOWARD THE CAROLINA COAST BY 12Z MONDAY. AFTER A CLEAR START
TO THE NIGHT...SOME MID AND HIGH CLOUDS WILL START SHOWING UP LATE
IN THE DEVELOPING SW RETURN FLOW. WARM ADVECTION IS FAIRLY GENTLE
OVERNIGHT AND STICKING WITH A NORMAL DIURNAL TEMPERATURE TREND FOR
NOW.
LEANED A BIT MORE TOWARD THE COOLER MAV TODAY...HAVING PERFORMED
BETTER YESTERDAY. WARMER MET LOOKS MORE REASONABLE TONIGHT IN THE
DEVELOPING WARM ADVECTION.
&&
.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
NO MAJOR CHANGES MADE TO MONDAY ON THIS SUNDAY MORNING GRAVEYARD
SHIFT. CLOUDS INCREASE ACROSS OUR WESTERN AND NORTHERN
COUNTIES...WITH SUNSHINE HOLDING THE LONGEST IN SOUTHWEST VIRGINIA
AND SOUTHEAST WEST VIRGINIA. POPS INCREASING QUICKLY ACROSS
SOUTHEAST OHIO DURING THE AFTERNOON.
HAVE LIKELY POPS FOR PCPN MONDAY NIGHT...MAINLY N OF HTS-CRW-EKN
LINE.
BASING THE FORECAST ON THE FRONT STILL SAGGING SOUTH MONDAY
NIGHT...REACHING NEAR A ROUTE 50 CORRIDOR BY 12Z TUESDAY BEFORE
TRYING TO LIFT SLOWLY BACK NORTH TUESDAY AFTERNOON...AHEAD OF
SURFACE LOW PRESSURE MOVING NORTHEAST UP THE OHIO RIVER VALLEY
TUESDAY NIGHT INTO WEDNESDAY.
FOR ABOUT A 6 HOUR WINDOW ON EITHER SIDE OF 12Z TUESDAY...WILL HAVE
THE POSSIBILITY OF A WINTRY MIXTURE OF RAIN...SNOW...SLEET...FROM
THE EKN VCNTY TO CKB-PKB AND NORTH OF UNI. FORECASTING THE SURFACE
TEMPERATURES IN THE 34/35 DEGREE NEIGHBORHOOD IN THAT TIME
INTERVAL FOR NORTHERN COUNTIES...SO DO NOT HAVE READINGS BELOW
FREEZING. OF COURSE...IN THE STRONG NORTH TO SOUTH GRADIENT...IF
FRONT SNEAKS A BIT FURTHER SOUTH...IT WOULD BE COLDER.
WILL HAVE STRATIFORM TYPE PRECIPITATION MONDAY AFTERNOON
THROUGH TUESDAY MORNING...THEN GO TO RAIN SHOWERS/CONVECTIVE TYPE
PRECIPITATION/ FOR TUESDAY AFTERNOON AND TUESDAY NIGHT. KEPT THE
CHANCE OF THUNDER BELOW 15 PCT FOR OUR SOUTHERN COUNTIES TUESDAY
NIGHT.
SURFACE FRONT LIKELY TO WHIP THROUGH DURING THE DAY ON
WEDNESDAY...SO INCREASED SURFACE WINDS THEN.
CURRENTLY...NO STRONG INDICATIONS FROM THE 00Z MODEL SOLUTIONS TO
ADD ANY WATER HAZARD FOR RAIN AMOUNTS.
TEMPERATURES WILL BE TOUGH THROUGH THIS ENTIRE PERIOD. TRIED TO STAY
ON THE MILD SIDE OF 00Z GFS MOS GUIDANCE FOR TUESDAY NIGHT...IN THE
WARM SECTOR AHEAD OF APPROACHING LOW.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
UNFORTUNATELY MODELS HAVE REVERTED BACK TO THEIR TIMING DIFF WITH
EJECTIONS OF SW UPR LOW...WITH 12Z ECWMF CONSIDERABLY SLOWER NOW.
WILL LEAN HEAVILY ON HPC WITH THIS SYS. ASSOCIATED SFC LOW LOOKS TO
TAKE A FAMILIAR TRACK THIS SEASON...THRU OH VALLEY. THIS WILL MEAN A
COLD FRONTAL PASSAGE SOMETIME ON WED WITH RA AND A TURN TO SEASONAL
TEMPS BEHIND IT FOR THU.
MORE ENERGY LOOKS TO DUMP BACK INTO SW CONUS...HELPING TO FORM
ANOTHER UPR LOW WHICH WILL TRY TO COME EAST LATE IN THE
PERIOD...WITH NORTHERN STREAM TRYING TO AMPLIFY ACROSS THE UPR
MIDWEST. THIS WILL HAVE TO BE MONITORED FOR SOME POTENTIAL PRE
CHRISTMAS MISCHIEF. AS OF NOW BL LOOKS WARM ENOUGH FOR RA.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
VORT MAX ROTATING ACROSS CENTRAL WEST VIRGINIA AT THIS TIME...WITH
BACK EDGE OF GENERAL SNOW SHOWER ACTIVITY ACCOMPANYING IT. MVFR
CIGS AT CKB/EKN/BKW WILL LINGER FOR A COUPLE OF HOURS...BEFORE
MOISTURE DECREASE SHUTS OFF THE REMAINING SNOW SHOWERS. CIGS WILL
RISE TO VFR IN MOST AREAS BY MIDMORNING. AS HIGH PRESSURE BUILDS IN
THIS AFTERNOON...SKIES WILL CLEAR AREAWIDE...WITH VFR EXPECTED FROM
18Z ON.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z MONDAY...
FORECAST CONFIDENCE: HIGH.
ALTERNATE SCENARIOS: MVFR CIGS MAY LINGER A BIT LONGER THAN FORECAST.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 11 12 13 14 15 16 17 18 19 20 21 22
EST 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17
CRW CONSISTENCY M H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H H H
BKW CONSISTENCY H L M H H H H H H H H H
EKN CONSISTENCY M L L M M M M M M H H H
PKB CONSISTENCY M H H H H H H H H H H H
CKB CONSISTENCY M M M M M M M M H H H H
AFTER 12Z MONDAY...
NO SIGNIFICANT AREAS OF IFR EXPECTED.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...30
AVIATION...CL
AREA FORECAST DISCUSSION
NWS NEW YORK NY
356 PM EST SUN DEC 18 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE WILL DRIFT OVER THE REGION TONIGHT...AND
OFFSHORE ON MONDAY. A COLD FRONT WILL PASS MONDAY NIGHT. HIGH
PRESSURE BUILDS OVER THE AREA TUESDAY. A WARM FRONT APPROACHES
FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO THE NORTH
WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY NIGHT...AS AN AREA
OF LOW PRESSURE PASSES TO OUR NORTH. HIGH PRESSURE THEN BUILDS IN
TO OUR NORTH THURSDAY THROUGH SUNDAY...AS A COUPLE OF LOW PRESSURE
SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
AT 20Z A 1026 HIGH WAS CENTERED NEAR MONTREAL. SKIES WERE CLEAR
ACROSS THE CWA. CLEAR SKIES WILL REMAIN LOCKED IN THRU
7PM...ALLOWING TEMPS TO DROP SHARPLY AFT DARK AS WINDS DECOUPLE.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY NIGHT/...
HIGH PRESSURE RIDGING FROM ERN CANADA TO THE GULF COAST WILL SLOWLY
TRANSLATE EWD OVERNIGHT. WINDS WILL GO CALM AS THE RIDGE TRAVERSES
THE CWA. THIS WILL ALLOW TEMPS TO DROP TO SOME OF THE COLDEST
READINGS OF THE YEAR. ONLY LIMITING FACTOR WILL BE CLOUDS OVER THE
GREAT LAKES INTO WRN PA AS THEY SPREAD EWD TOWARDS THE CWA. WITH
SUBSIDENCE OVER THE CWA HOWEVER...MOST OF THE LOW AND MID CLOUD
POTENTIAL WILL BE MITIGATED...LEAVING MAINLY HIGH CLOUDS OVER THE
AREA TNGT. TEMPS WERE THEREFORE TRENDED TOWARDS THE LOWER GUIDANCE
NUMBERS...AND HAVE TWEAKED READINGS EVEN COLDER THAN GUIDANCE ACROSS
THE PINE BARRENS OF LI. A FEW SINGLE DIGIT LOWS WILL BE POSSIBLE IN
THIS AREA. TEMPS BLW GUIDANCE IN THE CITY AS WELL...AS TEMPS AT
20Z WERE CLOSE TO GUIDANCE LOWS AND A FEW DEGREES SHOULD BE LOST
AFT DARK. SOME WARMING LATE IS POSSIBLE IN THE CITY AND WRN LI AS
LIGHT SW FLOW DEVELOPS ON THE BACK SIDE OF THE HIGH.
LOW PRES OVER ONTARIO WILL RACE EWD ON MON UNDER THE INFLUENCE OF A
STRENGTHENING 120KT H3 JET. AS THE ASSOCIATED COLD FRONT
APPROACHES...THE PRES GRAD WILL TIGHTEN...ALLOWING FOR INCREASING
WSW WINDS DURING THE DAY. SUSTAINED WINDS WILL MAX OUT IN THE
15-20KT RANGE WITH SOME GUSTS TO AROUND 30KT. STRONGEST WINDS WILL
BE ALONG THE S SHORES. 12Z OKX SOUNDING INDICATED 0.14 INCHES OF
PW...SO THE FCST WILL BE KEPT DRY DURING THE DAYTIME HOURS WITH
MOISTURE TRANSPORT VECTORS NOT REACHING THE CWA TIL AROUND 00Z TUE.
TEMPS WARMER THAN SUN DUE TO BETTER MIXING ALL AREAS AND AN ONSHORE
COMPONENT ON THE COASTS.
THE COLD FRONT PASSES MON NGT. 12Z MODELS IN GOOD AGREEMENT WITH
THIS. MOISTURE REMAINS EXTREMELY LIMITED...BUT ENOUGH LAKE MOISTURE
MAY ALLOW FOR A FEW SPRINKLES AND/OR FLURRIES. HAVE RETAINED THIS
WEATHER IN THE GRIDS. BL TOO WARM FOR FLAKES NEAR THE COASTS
INITIALLY...BUT AT THE CWA GETS INTO THE RR QUAD OF THE H3 170 PLUS
KT H3 JET AFT MIDNIGHT...A FEW FLURRIES POSSIBLE POST FRONTAL ACROSS
ALL AREAS. MOS WAS IN GOOD AGREEMENT FOR TEMPS...SO A BLEND WAS
USED.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
THE GFS IS MORE PROGRESSIVE THAN THE NAM/ECMWF/SREF WITH THE SYSTEM
IMPACTING THE REGION MID WEEK...AS IS ITS BIAS...SO USED A BLEND OF
THE SLOWER SOLUTIONS TUESDAY THROUGH WEDNESDAY. WEDNESDAY NIGHT
THROUGH CHRISTMAS DAY...THERE ARE QUITE A BIT OF DIFFERENCES BETWEEN
THE GFS AND ECMWF IN HOW THEY HANDLE THE NEXT SYSTEM EJECTING FROM
THE SW U.S. AND ITS INTERACTION WITH THE NORTHERN STREAM. DUE TO
BETTER RUN TO RUN CONSISTENCY AND BETTER OVERALL VERIFICATION IN THE
LONG TERM...LEANED HEAVILY TOWARDS THE ECMWF WEDNESDAY NIGHT THROUGH
SUNDAY.
RIDGING BUILDS INTO THE AREA TUESDAY/TUESDAY NIGHT...THEN SLIDES
OFFSHORE WEDNESDAY AS A SOUTHERN STREAM TROUGH LIFTS INTO THE UPPER
OHIO RIVER VALLEY...THIS TROUGH WILL SUPPORT A SURFACE LOW TRACKING
TO OUR NORTH WEDNESDAY.
TUESDAY SHOULD BE DRY UNDERNEATH THE RIDGE BUILDING IN. OVER RUNNING
SETS UP TUESDAY NIGHT...AHEAD OF A SURFACE AND 850 HPA WARM
FRONT...EXPECT LIGHT PRECIPITATION TO GRADUALLY DEVELOP FROM SW TO
NE FROM TUESDAY NIGHT INTO WEDNESDAY MORNING. LOW LEVEL THERMAL
PROFILES SUPPORT RAIN ACROSS NYC METRO/LONG ISLAND WITH A WINTRY
MIX...INCLUDING POSSIBLY SOME FREEZING RAIN ACROSS THE
INTERIOR...BEFORE CHANGING TO ALL RAIN AS THE WARM FRONT LIFTS TO
THE NORTH WEDNESDAY MORNING. 40-50 KT LOW LEVEL JET MOVES IN BY
WEDNESDAY AFTERNOON SUPPORTING MORE WIDESPREAD RAIN.
THE AFOREMENTIONED TROUGH LIFT JUST OVER THE REGION WEDNESDAY
NIGHT...ALLOWING PRECIPITATION TO TAPER OFF FROM W TO E BY THURSDAY
MORNING - STILL CARRY SLIGHT CHANCE POPS THURSDAY MORNING AS THERE
HAS BEEN SOME UNCERTAINTY IN TIMING OF THE SYSTEM...WITH SOME
SUGGESTIONS IT COULD END UP A TAD SLOWER THAN CURRENTLY FORECAST.
RIDGING BUILDS IN THURSDAY WITH ITS AXIS SLIDING OFFSHORE THURSDAY
NIGHT. FOLLOWING THE ECMWF...IT APPEARS THAT THE SHEARING TROUGH
FORECAST TO LIFT OUT OF BAJA CA WEDNESDAY...APPROACHES BY LATE
THURSDAY NIGHT...THEN CROSSES ON FRIDAY...WITH AN ASSOCIATED
COASTAL LOW PASSING TO THE SOUTH ALONG A STALLED FRONTAL BOUNDARY.
LOW LEVEL THERMAL PROFILES SUGGEST SNOW OR RAIN/SNOW ACROSS NORTHERN
ZONES AND RAIN ACROSS SOUTHERN ZONES BY LATE THURSDAY NIGHT...WITH
PRECIPITATION TRANSITIONING TO ALL RAIN DURING THE DAY ON FRIDAY ON
THE NORTHERN TIER. THERE IS QUITE A BIT OF UNCERTAINTY WITH THIS
SYSTEM...WITH SOME POTENTIAL IT COULD END UP MISSING US ENTIRELY TO
THE SOUTH.
FRIDAY NIGHT AND SATURDAY WILL FEATURE SW FLOW ALOFT...WITH SOME
EMBEDDED SHORTWAVES. THESE WARRANT SLIGHT CHANCE POPS FOR NOW...BUT
MORE THAN LIKELY WILL BE DRY.
THE NEXT POTENTIAL SYSTEM IMPACTS THE REGION LATE CHRISTMAS
EVE/CHRISTMAS DAY...THIS TIME EJECTING FROM NEAR THE FOUR CORNERS
REGION AROUND THURSDAY. LIKE THE SYSTEM FOR FRIDAY...THE SURFACE LOW
WILL TRACK TO THE SOUTH...THE QUESTION IS HOW FAR. FOLLOWING THE
ECMWF...HAVE SLIGHT CHANCE POPS FOR LIGHT SNOW DEVELOPING ACROSS
MOST ZONES LATE SATURDAY NIGHT...AND CONTINUING INTO SUNDAY
MORNING...THEN CHANGING TO RAIN IN THE AFTERNOON. ONCE AGAIN - LOW
CONFIDENCE AT THIS TIME.
NEAR NORMAL TEMPERATURES ARE EXPECTED TUESDAY...THEN ABOVE NORMAL
TEMPERATURES TUESDAY NIGHT THROUGH THURSDAY NIGHT. NEAR NORMAL
TEMPERATURES ARE FORECAST FRIDAY-SUNDAY.
&&
.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
VFR. HIGH PRESSURE REMAINS WEST OF THE AREA TERMINALS.
NORTH-NORTHWEST FLOW WITH SPEEDS OF 8 TO 12 KT WILL GRADUALLY
DIMINISH THIS EVENING TO LESS THAN 10 KT. EXPECT THE WIND DIRECTION
BETWEEN 320 TO 360.
SURFACE HIGH PRESSURE PASSES TO THE EAST TONIGHT WITH MOST TERMINALS
BECOMING LIGHT AND VARIABLE. AT THIS TIME...WINDS WILL GRADUALLY
SHIFT TO THE WEST AND EVENTUALLY THE SOUTHWEST. WIND SPEEDS INCREASE
THROUGHOUT MONDAY MORNING TO 8-12 KT WITH GUSTS INTO THE TEENS AND
LOWER 20S. SPEEDS MAY BE STRONGER AT THE NYC TERMINALS. CLOUD COVER
WILL INCREASE LATE IN THE 30 HOUR TAFS WITH THE APPROACH OF A COLD
FRONT...WITH VFR CIGS EXPECTED.
OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY...
MONDAY AFTERNOON AND MONDAY NIGHT...VFR. STRONG SW FLOW WITH GUST
UP TO 25 KT POSSIBLE. BRIEF PERIOD OF GUSTY NW FLOW LATE AT NIGHT.
TUESDAY AND TUESDAY NIGHT...VFR...TRENDING TOWARD SUB VFR LATE AT
NIGHT.
WEDNESDAY...SUB VFR IN RAIN...BECOMING VFR AT NIGHT.
THURSDAY...VFR.
FRIDAY...SUB-VFR POSSIBLE.
&&
.MARINE...
LIGHT WINDS TNGT AS HIGH PRES BUILDS OVER THE WATERS. THE HIGH
DRIFTS E OF THE CSTL WATERS MON...ALLOWING FOR A TIGHTENING PRES
GRAD TO DEVELOP THRU THE DAY AS A COLD FRONT APPROACHES FROM THE W.
STRENGTHENING WSW WINDS WILL BE THE RESULT. SCA WILL REMAIN IN
EFFECT FOR ALL WATERS EXCEPT FOR THE ERN OCEAN...WHERE THE GALE
WATCH WILL BE RETAINED. WINDS WEAKEN INVOF THE FRONT
OVERNIGHT...THEN VEER TO THE NW BEHIND THE FRONT EARLY TUE MRNG.
SCA LEVEL SEAS COULD LINGER INTO TUESDAY ON THE FAR EASTERN COASTAL
WATERS...OTHERWISE SUB-SCA CONDITIONS ARE EXPECTED TUESDAY AND
TUESDAY NIGHT. SOUTHERLY FLOW AHEAD OF A STORM SYSTEM
WEDNESDAY...SHOULD AT LEAST BUILD SEAS ON THE COASTAL OCEAN WATERS
TO SCA LEVELS...WITH GUSTY WINDS CONTINUING THEM AT SCA LEVELS INTO
THURSDAY. THERE IS SOME POTENTIAL FOR SCA LEVEL GUSTS ON ALL WATERS
WEDNESDAY-THURSDAY...BUT NOT QUITE CONFIDENT ENOUGH TO GO WITH THIS
IN THE FORECAST AT THIS TIME.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH A COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS.
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE MON NGT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS SHOULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM MONDAY TO 1 AM EST TUESDAY FOR
ANZ330-335-338-340-345-355.
GALE WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR
ANZ350-353.
&&
$$
SYNOPSIS...JMC/MALOIT
NEAR TERM...JMC
SHORT TERM...JMC
LONG TERM...MALOIT
AVIATION...BC
MARINE...JMC/MALOIT
HYDROLOGY...JMC/MALOIT
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
314 PM CST SUN DEC 18 2011
.DISCUSSION...
959 AM CST
THE DENSE FOG CONTINUES TO SLOWLY DISSIPATE...WITH MOST PREVAILING
VISIBILITIES AT OR ABOVE ONE MILE. THE EXCEPTION IS NORTHWEST
INDIANA WHERE THE FOG/STRATUS SPREAD IN THE LATEST. THE FOG
SHOULD CONTINUE TO ABATE WITH INCREASING LOW-LEVEL SOUTHWEST WINDS
EASING THE INVERSION IN THE LOWEST FEW HUNDRED FEET. IT IS
INTERESTING TO NOTE HOW THIS FOG CORRELATED WITH THE LIGHT BUT
FRESH SNOW COVER FROM THE SATURDAY MORNING EVENT. THIS SNOW COVER
MAKES IT TRICKY FOR TEMPERATURES THIS AFTERNOON...AS IT AIDED IN
COOLING LAST NIGHT /DOWN TO 10 DEGREES IN ROCHELLE/. IT HELPED THE
ASSOCIATED DEPTH OF THE INVERSION WITH RUC DIAGNOSTIC SOUNDINGS
INDICATING AN 8C DEGREE CLIMB JUST 100MB /3000 FT OR SO/ FROM THE
SURFACE OVER LOCATIONS IN THE NORTHERN HALF OF THE FORECAST AREA.
THE NORMAL DIURNAL CLIMB AT ORD AND RFD ARE 14 AND 15 DEGREES
RESPECTIVELY. WITH MORNING FOG/STRATUS AT AND AROUND BOTH
LOCATIONS...WOULD NOT THINK WE WOULD CLIMB MUCH ABOVE THAT GIVEN
THE INVERSION STRENGTH. IT WILL LIKELY CLIMB EVEN LESS IN CHICAGO
WHERE THE CLOUDS RESIDED LONGER. BELIEVE THE RUC AND MOST RECENT
NAM RUN AT 12Z HAVE A GOOD HANDLE ON KEEPING TEMPERATURES COOLER
IN THE NORTHERN FORECAST AREA. HAVE TRENDED THAT ROUTE...CUTTING 3
TO 5 DEGREES OFF OR SO.
MTF
//PREV DISCUSSION...
408 AM CST
HIGH PRESSURE CONTINUES TO BUILD INTO THE SOUTHEAST US THIS
MORNING. A STUBBORN STRATUS DECK THAT RESIDED OVER AREAS EAST OF
I-39 HAS FINALLY ERODED. HIGH CIRRUS CLOUDS ARE QUICKLY MOVING
SOUTHEAST INTO THE AREA...BUT IR IMAGERY INDICATES THE CLOUDS ARE
DISSIPATING AS THEY MOVE IN. EXPECTING CLEARING TO CONTINUE
THROUGH TODAY. WHILE MOST OF THE SNOWFALL FROM YESTERDAY HAS
ALREADY MELTED...THE CLEAR SKIES ARE ALLOWING TEMPS TO DROP
RAPIDLY. SOME LOCATIONS THAT HAVE SNOW ON THE GROUND MAY EVEN DIP
INTO THE TEENS BEFORE SUNRISE. AREAS OF FOG WILL CONTINUE TO
PERSIST AND BURN OFF AFTER SUNRISE. WITH PLENTY OF SUNSHINE
TOMORROW...TEMPS WILL RISE INTO THE LOW 40S TODAY.
CLOUDS BEGIN TO MOVE IN LATE TONIGHT AHEAD OF THE NEXT SYSTEM. IN
REGARDS TO THE NEXT SYSTEM...THE MODELS ARE BEGINNING TO SHOW A
SIMILAR SOLUTION AND FORECAST CONFIDENCE FOR THE TIMING OF THE
PRECIP IS MEDIUM. THE LOW MOVES FROM OKLAHOMA TUESDAY MORNING TO
DETROIT BY WEDNESDAY AFTERNOON. THIS PATH WOULD BRING A SWATH OF
PRECIPITATION INTO THE REGION. THE GFS WANTS TO PUSH THE PRECIP
FARTHER NORTH INTO CENTRAL WISCONSIN...WHILE THE ECMWF HAS THE
PRECIP ONLY REACHING SOUTHERN WISCONSIN. SINCE THE GFS SOLUTIONS
HAVE BEEN SLOWLY CONVERGING WITH THE STEADY ECMWF SOLUTION...WENT
AHEAD AND LIMITED THE NORTHERN EXTENT OF THE PRECIP. THAT BEING
SAID...CONFIDENCE IN THE FORECASTED PRECIP TYPE REMAINS LOW. LOOKING
AT MODEL SOUNDINGS...THE GFS WANTS TO WARM THE THERMAL PROFILE
TUESDAY...WHILE THE NAM WANTS TO COOL THE PROFILE. BOTH PROFILES
HAVE SURFACE TEMPS NEAR FREEZING.
PRECIP FROM THE LOW REACHES NORTHEASTERN IL AND NORTHWESTERN IN LATE
MONDAY INTO MONDAY NIGHT AS RAIN. THE RAIN WILL BEGIN SOUTH OF I-80
AND SLOWLY INCH NORTHWARD THROUGH TUESDAY. AREAS SOUTH OF I-80 WILL
LIKELY SEE ALL RAIN AS THEY WILL BE CLOSEST TO THE LOW ITSELF. A
RAIN/SNOW MIX WILL FALL NORTH OF I-80 ON TUESDAY. SINCE THIS LOW IS
COMING OUT OF THE SOUTH CENTRAL US...THERE IS NO GOOD COLD AIR PUSH
ASSOCIATED WITH IT. THEREFORE...AS THE LOW PULLS AWAY TUESDAY NIGHT
AND WEDNESDAY...LINGERING PRECIP WILL FALL AS A RAIN/SNOW MIX OR AS
A COLD RAIN. DAYTIME HIGH TEMPS TUESDAY THROUGH THURSDAY WILL BE IN
THE MID 30S TO LOW 40S. LOW TEMPS WILL BE IN THE UPPER 20S TO LOW
30S.
NUMEROUS UPPER LEVEL ENERGY STREAMERS PASS THROUGH THE REGION
THURSDAY AND FRIDAY...RESULTING IN SLIGHT CHANCES OF SNOW. NONE OF
THESE CHANCES LOOK LIKE THEY WILL PRODUCE SIGNIFICANT SNOWFALL.
HIGH PRESSURE MOVES IN FROM THE PLAINS ON FRIDAY.
JEE
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 21Z...
* MARGINALLY GUSTY SSW TO SW REST OF AFTERNOON.
* TIMING OF PASSAGE LOCALLY OF COLD FRONT TRAILING SW FROM LOW
PRES MOVING ACROSS ONTARIO OVERNIGHT.
* PERIOD OF MVFR CEILINGS POSSIBLE MON MORNING FOLLOWING CFP.
TRS
//DISCUSSION...UPDATED 18Z...
SUN AND INCREASING WINDS DID HEIR JOBS IN MIXING OUT THE STRATUS
AND FOG STUCK UNDER THE VERY SHALLOW INVERSION. REST OF THE DAY
AND MUCH OF TONIGHT WILL ONLY SEE PERIODIC AREAS OF CIRRUS CROSSING
OVERHEAD AS THEY TOP THE BROAD UPPER RIDGE CENTERED OVER THE
PLAINS.
A SHORT WAVE CROSSING THE SOUTHERN CANADIAN ROCKIES LATE THIS
MORNING WILL CONTINUE EAST-SOUTHEAST AND CROSS ONTARIO OVERNIGHT.
A COLD FRONT TRAILING BACK TO THE SOUTHWEST ACROSS THE UPPER
MIDWEST AND THE CENTRAL PLAINS WILL BE MOVING EAST...AND IS
EXPECTED TO CROSS NORTHERN IL AND AND NORTHWEST IND DURING THE
PERIOD FROM 12Z TO 18Z MON.
A THICK LAYER OF MID LEVEL DRY AIR IS PROGGED ACROSS THE LOCAL
AREA DURING THE TIME OF THE PASSAGE OF TAIL OF THE ONTARIO SHORT
WAVE TROUGH AND THE COLD FRONT CROSSING THE LOCAL AREA SO NO
PRECIPITATION OUTSIDE OF A FEW FLURRIES EXPECTED.
FORECAST PROFILES DO SHOW A LAYER OF MOIST LOWER LEVEL AIR
TRAPPED UNDER AN INVERSION FOLLOWING THE COLD FRONTAL PASSAGE WITH
THE BASE OF THE INVERSION LOWERING TO AROUND 022 SO HAVE A PERIOD
OF MVFR CEILINGS IN THE TAFORS FOLLOWING THE COLD FRONT AND THE
ASSOCIATED WIND SHIFT FROM SOUTHWEST TO WEST AND WEST-NORTHWEST.
AS HIGH PRESSURE BUILDS IN FROM SOUTH CENTRAL CANADA AND THE
NORTHERN PLAINS ANTICYCLONIC LOW LEVEL FLOW INCREASES AND SHOULD
SERVE TO BREAK UP AND LIFT THE STRATOCUMULUS DECK.
ANOTHER SHORT WAVE DROPS SOUTHEAST OVER THE NORTHERN HIGH PLAINS
MONDAY MORNING AND THEN TURNS EASTWARD AND CROSSES THE DAKOTAS
DURING THE AFTERNOON BEFORE CROSSING THE UPPER MIDWEST AND WESTERN
GREAT LAKES DURING MIDDAY NIGHT. THIS SHORT WAVE WILL BE PASSING
OVER A LARGE DRY SURFACE HIGH ACROSS THE REGION SO ONLY EVIDENCE
SUSPECTED WILL BE AND INCREASE IN MID LEVEL CLOUDS LATER MONDAY
AND MONDAY NIGHT.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN VFR REST OF THIS AFTERNOON AND TONIGHT.
* HIGH CONFIDENCE IN WIND FORECASTS.
* MEDIUM CONFIDENCE IN COLD FRONTAL PASSAGE MONDAY MORNING AND
EXTEND OF MVFR CEILINGS IN WAKE OF THIS FRONT.
TRS
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF
ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN AND SNOW. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
SATURDAY...VFR.
MDB
&&
.MARINE...
305 PM
LOW PRESSURE WILL BE DEEPENING AS IT MOVES EAST ACROSS ONTARIO
TONIGHT. THE DEEPENING OF THE LOW AND THE APPROACH OF THE
SOUTHWESTWARD TRAILING COLD FRONT IS INCREASING THE PRESSURE
GRADIENT ACROSS THE WESTERN GREAT LAKES AND EXPECT WINDS TO REACH
GALE FORCE ON THE NORTH HALF BY LATE AFTERNOON AND ON THE SOUTH
HALF DURING THE EVENING.
AS THE COLD FRONT APPROACHES LATE TONIGHT THE GRADIENT AND
RESULTANT WINDS WILL DIMINISH. WIND DIRECTIONS VEER TO W...NW
AND EVENTUALLY N DURING THE DAY AS HIGH PRESSURE BUILDS OVER THE
PLAINS BEHIND THE COLD FRONT. THIS HIGH THEN SPREADS EAST ACROSS
THE UPPER MIDWEST AND THE UPPER GREAT LAKES....WITH THE HIGH BEING
CENTERED OVER THE GREAT LAKES BY TUESDAY MORNING.
DURING THE DAY TUESDAY LOW PRESSURE WILL BE MOVING NORTHEASTWARD
FROM THE SOUTHERN PLAINS...REACHING THE MID MISSISSIPPI VALLEY BY
TUESDAY NIGHT. THE LOW THEN MOVES EAST ACROSS THE MIDWEST TO THE
UPPER OHIO RIVER VALLEY BY WEDNESDAY EVENING.
ANTHER COLD FRONT WILL MOVE FROM THE UPPER MIDWEST ACROSS LAKE
MICHIGAN DURING WEDNESDAY NIGHT AND THURSDAY MORNING....WITH
ANOTHER LARGE AREA OF HIGH PRESSURE SETTLING OVER THE CENTRAL
PLAINS THURSDAY NIGHT...AND SPREADING EAST ACROSS THE MIDWEST
FRIDAY AND FRIDAY NIGHT.
TRS
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 5 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 5 AM MONDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 8 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1253 PM CST SUN DEC 18 2011
.DISCUSSION...
959 AM CST
THE DENSE FOG CONTINUES TO SLOWLY DISSIPATE...WITH MOST PREVAILING
VISIBILITIES AT OR ABOVE ONE MILE. THE EXCEPTION IS NORTHWEST
INDIANA WHERE THE FOG/STRATUS SPREAD IN THE LATEST. THE FOG
SHOULD CONTINUE TO ABATE WITH INCREASING LOW-LEVEL SOUTHWEST WINDS
EASING THE INVERSION IN THE LOWEST FEW HUNDRED FEET. IT IS
INTERESTING TO NOTE HOW THIS FOG CORRELATED WITH THE LIGHT BUT
FRESH SNOW COVER FROM THE SATURDAY MORNING EVENT. THIS SNOW COVER
MAKES IT TRICKY FOR TEMPERATURES THIS AFTERNOON...AS IT AIDED IN
COOLING LAST NIGHT /DOWN TO 10 DEGREES IN ROCHELLE/. IT HELPED THE
ASSOCIATED DEPTH OF THE INVERSION WITH RUC DIAGNOSTIC SOUNDINGS
INDICATING AN 8C DEGREE CLIMB JUST 100MB /3000 FT OR SO/ FROM THE
SURFACE OVER LOCATIONS IN THE NORTHERN HALF OF THE FORECAST AREA.
THE NORMAL DIURNAL CLIMB AT ORD AND RFD ARE 14 AND 15 DEGREES
RESPECTIVELY. WITH MORNING FOG/STRATUS AT AND AROUND BOTH
LOCATIONS...WOULD NOT THINK WE WOULD CLIMB MUCH ABOVE THAT GIVEN
THE INVERSION STRENGTH. IT WILL LIKELY CLIMB EVEN LESS IN CHICAGO
WHERE THE CLOUDS RESIDED LONGER. BELIEVE THE RUC AND MOST RECENT
NAM RUN AT 12Z HAVE A GOOD HANDLE ON KEEPING TEMPERATURES COOLER
IN THE NORTHERN FORECAST AREA. HAVE TRENDED THAT ROUTE...CUTTING 3
TO 5 DEGREES OFF OR SO.
MTF
//PREV DISCUSSION...
408 AM CST
HIGH PRESSURE CONTINUES TO BUILD INTO THE SOUTHEAST US THIS
MORNING. A STUBBORN STRATUS DECK THAT RESIDED OVER AREAS EAST OF
I-39 HAS FINALLY ERODED. HIGH CIRRUS CLOUDS ARE QUICKLY MOVING
SOUTHEAST INTO THE AREA...BUT IR IMAGERY INDICATES THE CLOUDS ARE
DISSIPATING AS THEY MOVE IN. EXPECTING CLEARING TO CONTINUE
THROUGH TODAY. WHILE MOST OF THE SNOWFALL FROM YESTERDAY HAS
ALREADY MELTED...THE CLEAR SKIES ARE ALLOWING TEMPS TO DROP
RAPIDLY. SOME LOCATIONS THAT HAVE SNOW ON THE GROUND MAY EVEN DIP
INTO THE TEENS BEFORE SUNRISE. AREAS OF FOG WILL CONTINUE TO
PERSIST AND BURN OFF AFTER SUNRISE. WITH PLENTY OF SUNSHINE
TOMORROW...TEMPS WILL RISE INTO THE LOW 40S TODAY.
CLOUDS BEGIN TO MOVE IN LATE TONIGHT AHEAD OF THE NEXT SYSTEM. IN
REGARDS TO THE NEXT SYSTEM...THE MODELS ARE BEGINNING TO SHOW A
SIMILAR SOLUTION AND FORECAST CONFIDENCE FOR THE TIMING OF THE
PRECIP IS MEDIUM. THE LOW MOVES FROM OKLAHOMA TUESDAY MORNING TO
DETROIT BY WEDNESDAY AFTERNOON. THIS PATH WOULD BRING A SWATH OF
PRECIPITATION INTO THE REGION. THE GFS WANTS TO PUSH THE PRECIP
FARTHER NORTH INTO CENTRAL WISCONSIN...WHILE THE ECMWF HAS THE
PRECIP ONLY REACHING SOUTHERN WISCONSIN. SINCE THE GFS SOLUTIONS
HAVE BEEN SLOWLY CONVERGING WITH THE STEADY ECMWF SOLUTION...WENT
AHEAD AND LIMITED THE NORTHERN EXTENT OF THE PRECIP. THAT BEING
SAID...CONFIDENCE IN THE FORECASTED PRECIP TYPE REMAINS LOW. LOOKING
AT MODEL SOUNDINGS...THE GFS WANTS TO WARM THE THERMAL PROFILE
TUESDAY...WHILE THE NAM WANTS TO COOL THE PROFILE. BOTH PROFILES
HAVE SURFACE TEMPS NEAR FREEZING.
PRECIP FROM THE LOW REACHES NORTHEASTERN IL AND NORTHWESTERN IN LATE
MONDAY INTO MONDAY NIGHT AS RAIN. THE RAIN WILL BEGIN SOUTH OF I-80
AND SLOWLY INCH NORTHWARD THROUGH TUESDAY. AREAS SOUTH OF I-80 WILL
LIKELY SEE ALL RAIN AS THEY WILL BE CLOSEST TO THE LOW ITSELF. A
RAIN/SNOW MIX WILL FALL NORTH OF I-80 ON TUESDAY. SINCE THIS LOW IS
COMING OUT OF THE SOUTH CENTRAL US...THERE IS NO GOOD COLD AIR PUSH
ASSOCIATED WITH IT. THEREFORE...AS THE LOW PULLS AWAY TUESDAY NIGHT
AND WEDNESDAY...LINGERING PRECIP WILL FALL AS A RAIN/SNOW MIX OR AS
A COLD RAIN. DAYTIME HIGH TEMPS TUESDAY THROUGH THURSDAY WILL BE IN
THE MID 30S TO LOW 40S. LOW TEMPS WILL BE IN THE UPPER 20S TO LOW
30S.
NUMEROUS UPPER LEVEL ENERGY STREAMERS PASS THROUGH THE REGION
THURSDAY AND FRIDAY...RESULTING IN SLIGHT CHANCES OF SNOW. NONE OF
THESE CHANCES LOOK LIKE THEY WILL PRODUCE SIGNIFICANT SNOWFALL.
HIGH PRESSURE MOVES IN FROM THE PLAINS ON FRIDAY.
JEE
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* SSW TO SW WINDS GRADUALLY BECOMING A BIT GUSTY THIS AFTERNOON.
* TIMING OF PASSAGE LOCALLY OF COLD FRONT TRAILING SW FROM LOW
PRES MOVING ACROSS ONTARIO OVERNIGHT.
* PERIOD OF MVFR CEILINGS POSSIBLE MON MORNING FOLLOWING CFP.
TRS
//DISCUSSION...UPDATED 18Z...
SUN AND INCREASING WINDS DID HEIR JOBS IN MIXING OUT THE STRATUS
AND FOG STUCK UNDER THE VERY SHALLOW INVERSION. REST OF THE DAY
AND MUCH OF TONIGHT WILL ONLY SEE PERIODIC AREAS OF CIRRUS CROSSING
OVERHEAD AS THEY TOP THE BROAD UPPER RIDGE CENTERED OVER THE
PLAINS.
A SHORT WAVE CROSSING THE SOUTHERN CANADIAN ROCKIES LATE THIS
MORNING WILL CONTINUE EAST-SOUTHEAST AND CROSS ONTARIO OVERNIGHT.
A COLD FRONT TRAILING BACK TO THE SOUTHWEST ACROSS THE UPPER
MIDWEST AND THE CENTRAL PLAINS WILL BE MOVING EAST...AND IS
EXPECTED TO CROSS NORTHERN IL AND AND NORTHWEST IND DURING THE
PERIOD FROM 12Z TO 18Z MON.
A THICK LAYER OF MID LEVEL DRY AIR IS PROGGED ACROSS THE LOCAL
AREA DURING THE TIME OF THE PASSAGE OF TAIL OF THE ONTARIO SHORT
WAVE TROUGH AND THE COLD FRONT CROSSING THE LOCAL AREA SO NO
PRECIPITATION OUTSIDE OF A FEW FLURRIES EXPECTED.
FORECAST PROFILES DO SHOW A LAYER OF MOIST LOWER LEVEL AIR
TRAPPED UNDER AN INVERSION FOLLOWING THE COLD FRONTAL PASSAGE WITH
THE BASE OF THE INVERSION LOWERING TO AROUND 022 SO HAVE A PERIOD
OF MVFR CEILINGS IN THE TAFORS FOLLOWING THE COLD FRONT AND THE
ASSOCIATED WIND SHIFT FROM SOUTHWEST TO WEST AND WEST-NORTHWEST.
AS HIGH PRESSURE BUILDS IN FROM SOUTH CENTRAL CANADA AND THE
NORTHERN PLAINS ANTICYCLONIC LOW LEVEL FLOW INCREASES AND SHOULD
SERVE TO BREAK UP AND LIFT THE STRATOCUMULUS DECK.
ANOTHER SHORT WAVE DROPS SOUTHEAST OVER THE NORTHERN HIGH PLAINS
MONDAY MORNING AND THEN TURNS EASTWARD AND CROSSES THE DAKOTAS
DURING THE AFTERNOON BEFORE CROSSING THE UPPER MIDWEST AND WESTERN
GREAT LAKES DURING MIDDAY NIGHT. THIS SHORT WAVE WILL BE PASSING
OVER A LARGE DRY SURFACE HIGH ACROSS THE REGION SO ONLY EVIDENCE
SUSPECTED WILL BE AND INCREASE IN MID LEVEL CLOUDS LATER MONDAY
AND MONDAY NIGHT.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN VFR REST OF TODAY AND TONIGHT.
* HIGH CONFIDENCE IN WIND FORECASTS.
* MEDIUM CONFIDENCE IN COLD FRONTAL PASSAGE MONDAY MORNING AND
EXTEND OF MVFR CEILINGS IN WAKE OF THIS FRONT.
TRS
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF
ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN AND SNOW. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
SATURDAY...VFR.
MDB
&&
.MARINE...
315 AM CST
...SOUTHWEST GALES DEVELOP THIS AFTERNOON...
A SERIES OF RIDGES AND TROUGHS DOT THE EARLY MORNING WEATHER MAP.
HIGH PRESSURE EXTENDS FROM EASTERN QUEBEC INTO NORTHERN NEW ENGLAND
AND IS WORKING TOWARDS THE ATLANTIC WHILE LOW PRESSURE OVER HUDSON
BAY MOVES EASTWARD DRAGGING A TROUGH ACROSS LAKE HURON AND SOUTHERN
ONTARIO. WEAK RIDGING IS POSITIONED TO THE WEST OF THE TROUGH AND
WILL CREST OVER LAKE MICHIGAN THIS MORNING. THE MOST NOTABLE FEATURE
IS LOW PRESSURE MOVING FROM CENTRAL SASKATCHEWAN INTO CENTRAL
MANITOBA. THIS LOW WILL DEEPEN AS IT MOVES EAST TODAY TIGHTENING THE
PRESSURE GRADIENT ACROSS THE UPPER LAKES THIS AFTERNOON. THE LOW WILL
DRAG A TROUGH ACROSS THE LAKE EARLY MONDAY MORNING WHICH WILL SHIFT
WINDS TO NORTHWESTERLY. IN TERMS OF TRENDS...WINDS WILL BEGIN TO
SLACKEN SOMEWHAT THIS MORNING AS THE RIDGE MOVES ACROSS BUT THEN
QUICKLY PICK UP FROM THE SOUTHWEST THIS AFTERNOON AS THE DEEPENING
LOW MOVES INTO WESTERN ONTARIO AND JUST NORTH OF LAKE SUPERIOR BY
EVENING. AM EXPECTING SPEEDS TO REACH GALE FORCE TO 40 KT BY LATE
AFTERNOON NORTH AND CONTINUE THROUGH THE EVENING THEN SLOWLY BEGIN
TO DIMINISH TO 35 KT GALES AFTER MIDNIGHT WITH A REDUCTION TO
BELOW GALE TOWARD DAYBREAK. STRONGEST SPEEDS WILL BE ACROSS THE
NORTHERN HALF TO TWO-THIRDS OF THE LAKE WITH SPEEDS A FEW KNOTS
LOWER AND SLIGHTLY SLOWER IN ARRIVING ACROSS THE SOUTH. SPEEDS
WILL LIKELY REMAIN IN THE 20 TO 25 KT RANGE FOR MOST OF MONDAY AS
THE PRESSURE GRADIENT REMAINS STRONG BETWEEN THE DEPARTING LOW AND
A STRONG HIGH THAT WILL BE MOVING IN FROM THE WEST. WINDS WILL
TURN TO THE NORTH BY AFTERNOON THEN PROBABLY TURN MORE NORTHEAST
AS SPEEDS DROP OFF MONDAY EVENING AS THE HIGH REACHES THE LAKE.
LOW PRESSURE WILL DEVELOP ACROSS NORTHERN TEXAS MONDAY NIGHT AND
LIFT NORTHEASTWARD INTO EAST-CENTRAL ILLINOIS TUESDAY NIGHT WHILE
ANOTHER LOW MOVES ACROSS HUDSON BAY. RIDGING WILL REMAIN ACROSS THE
LAKE BUT THE NORTHERN SYSTEM LOOKS TO PASS CLOSE ENOUGH TO BRING
INCREASING SOUTH TO SOUTHWEST WINDS ACROSS THE FAR NORTHERN PART OF
THE LAKE TUESDAY AFTERNOON. THE GRADIENT WILL REMAIN WEAKER SOUTH
BUT A MORE SOUTHEASTERLY WIND DIRECTION SHOULD PREVAIL AHEAD OF THE
APPROACHING LOW. THE LOW WILL LIKELY PASS JUST TO THE SOUTHEAST OF
THE LAKE WEDNESDAY ALLOWING WINDS TO TURN NORTH OR NORTHEAST BEFORE
TURNING NORTHWEST WEDNESDAY EVENING. THE PATTERN REMAINS ACTIVE FROM
THAT POINT ONWARD WITH A SERIES OF HIGHS AND LOWS BRINGING UPS AND
DOWNS TO THE WIND SPEED FORECAST INTO NEXT WEEKEND.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
103 PM EST SUN DEC 18 2011
UPDATED AVIATION DISCUSSION FOR 18Z TAFS
.DISCUSSION /TODAY THROUGH SATURDAY/... ISSUED AT 431 AM EST
QUIET MORNING ACROSS UPPER MICHIGAN...AS SFC RIDGE IS SLIDING ACROSS
THE UPPER GREAT LKS REGION. PERSISTENT AREA OF LOW CLOUDS EARLY THIS
MORNING ON SATELLITE...STRETCHING SW INTO NRN WI. MOST MODELS HAVING
A DIFFICULT TIME WITH THEM...BUT RUC SEEMS TO HAVE A DECENT HANDLE
ON LOW CLOUDS ON 0.5-1KM RH FIELDS...SO HAVE FOLLOWED THAT FOR THE
EXIT OF THE MVFR CLOUDS THIS MORNING. THINK THEY WILL LIKELY PERSIST
THROUGH THE FIRST PART OF THE MORNING UNTIL LLVL WINDS SHIFT TO THE
SW AND PUSH THEM NE OF THE AREA.
1002MB LOW PRESSURE SYSTEM CURRENTLY LOCATED JUST NW OF LK WINNIPEG
WILL SLOWLY DEEPEN THROUGH THE DAY...AS A NRN STREAM SHORTWAVE
AMPLIFIES OVER SOUTHERN CANADA THROUGH THE DAY. BY 00Z...SHOULD SEE
A 999MB LOW LOCATED JUST TO THE N OF LK SUPERIOR. STRONG H850-500
WAA OVER SRN CANADA /AND PRODUCING A FEW -SHSN E OF LK WINNIPEG/
WILL SHIFT ESE THROUGH SRN ONTARIO AND FAR NRN LK SUPERIOR FROM MID
MORNING THROUGH THE REST OF THE DAY. WITH THE BEST MOISTURE LOCATED
IN THIS AREA...EXPECT THE PCPN TO STAY N OF THE LAND AREAS. HEADING
FARTHER S OVER UPPER MI...DRY AIR BELOW H750 SHOULD KEEP ANY PCPN
COMING OUT OF THE MID CLOUDS FROM REACHING THE SFC FROM MID MORNING
THROUGH EARLY AFTN. LIKELY WON/T SEE MUCH SUN THROUGH THE MORNING
HOURS WITH THE LINGERING LLVL CLOUDS THAT WILL BE OVERRUN BY THE
INCOMING MID CLOUDS. DRY SLOT BEGINS TO MOVE OVER THE AREA AROUND
MID AFTN AND MAY LEAD TO SOME CLEARING...ESPECIALLY OVER THE W HALF.
WITH THE LOW INTENSIFYING AS IT MOVES N OF THE AREA...WILL LIKELY
SEE SOME GUSTY SW WINDS THIS AFTN. STRENGTHENING INVERSION AROUND
H900 WILL LIMIT ACCESS TO THE LLVL JET AROUND 45KTS. BUT TIGHTENING
PRESS GRADIENT WILL STILL LEAD TO GUSTS IN THE 20-30KT
RANGE...ESPECIALLY IN THE SW WIND DOWNSLOPE AREAS NEAR LK SUPERIOR.
THE INVERSION AND CLEARING THIS AFTN MAKES TEMPS TRICKY...AS THERE
WILL BE A LIMITED PERIOD FOR SUNSHINE HELP MIX HIGHER ALOFT. THOUGH
PREVIOUS HIGHS LOOKED GOOD AND ONLY MADE MINOR TWEAKS. WITH THE WARM
START AND SSWRLY FLOW...EXPECT THE HIGHS TO BE IN THE UPPER 30S AND
MAYBE AN ISOLATED 40 OVER THE WRN CWA /WHERE WARMER AIR SURGES INTO
THE AREA AND THERE IS A LONGER PERIOD OF CLEAR SKIES/...ALONG WITH
DOWNSLOPE AREAS NEAR LK SUPERIOR.
SFC LOW WILL QUICKLY DEEPEN TO 993MB THROUGH THE NIGHT AS IT SHIFTS
JUST SE OF JAMES BAY BY 12Z. DRY SLOT WILL STILL BE OVER THE AREA
AND PROVIDE A CLEAR BUT BREEZY EVENING. SFC TROUGH/COLD FRONT WILL
THEN SLIDE SE THROUGH THE CWA AFTER MIDNIGHT AND BRING A CHANCE FOR
PCPN TO AREAS NEAR LK SUPERIOR. NOT OVERLY IMPRESSED WITH
FORCING/MOISTURE ALONG THE FRONT...SO HAVE WENT WITH SLIGHT
CHANCES...EXCEPT FOR FAVORABLE UPSLOPE NW WIND LOCATIONS OVER THE
WRN CWA. P-TYPE WILL BE SNOW INITIALLY WITH THE PASSAGE OF THE
FRONT...BUT COULD BE SOME FZDZ WITH THE UPSLOPE FLOW OVER THE WRN
U.P. SOUNDINGS SHOW INCREASING LLVL LAPSE RATES OVER THE WEST AFTER
06Z TONIGHT BELOW THE 3-4KFT INVERSION. WITH NEAR SFC DRY AIR
PUTTING CLOUD BASES AROUND 1.5-2.5KFT...OVERALL CLOUD DEPTH WILL BE
FAIRLY SHALLOW. IN ADDITION...CLOUD TOPS ARE ONLY AROUND -7 TO -8C
AFTER THE FRONT MOVES THROUGH...LIMITING ICE CRYSTALS IN THE CLOUDS.
THEREFORE...HAVE ADDED A MENTION OF FZDZ OVER THE W AFTER 09Z. OVER
THE E...WARMER TEMPS WILL LIKELY LEAD TO MORE OF A DZ/SN POTENTIAL
LATE TONIGHT.
WITH CONTINUED H925-850 MOISTURE AND H850 TEMPS FALLING TOWARDS -10C
BY MID MORNING...EXPECT A PERIOD OF LK ENHANCED PCPN DURING THE
MORNING HOURS. TEMPS SHOULD FALL ENOUGH MON MORN OVER THE W TO
PRODUCE ENOUGH ICE CRYSTALS FOR ANY LINGERING SHOWERS TO BE ALL
SNOW. THERE COULD BE A SLIGHT LAG OVER THE E NEAR LK SUPERIOR FOR
THE FIRST COUPLE OF HOURS AND MENTIONED A -SHSN/FZDZ INITIALLY IN
THE MORNING. LAKE EFFECT POTENTIAL QUICKLY DIMINISHES HEADING INTO
THE AFTN...AS H850-700 SUBSIDENCE INCREASES AND LLVL MOISTURE
DEPARTS. IN ADDITION...MODELS SHOWING INVERSION HEIGHTS AT OR BELOW
3KFT IN THE AFTN AND LOCAL/NATIONAL HIRES WRF RUNS NOT SHOWING ANY
PCPN. WITH ALL THE NEGATIVES...HAVE TAPERED BACK EXISTING POPS IN
THE AFTN...BUT DID LEAVE SOME LOW CHANCES OVER THE E FOR NNW WIND
FAVORED LOCATIONS WHERE THE LONGER FETCH MAY HELP KEEP PCPN GOING.
HIGH PRESSURE RIDGE WILL BUILD OVER THE AREA ON MON NIGHT...BRINGING
AN END TO ANY LINGERING LES EARLY IN THE EVENING. WITH LIGHT WINDS
AND CLEAR SKIES UNDER THE HIGH PRESSURE RIDGE...EXPECT A GOOD
RADIATIONAL COOLING NIGHT. PWAT VALUES /AROUND 0.1 INCH OR 35
PERCENT OF NORMAL/ SUPPORT GOING ON THE LOW END OF GUIDANCE...AND
HAVE LOWS FALLING INTO THE SINGLE DIGITS ABOVE ZERO.
NRN STREAM OF THE JET WILL REMAIN N OF THE AREA FOR TUES/WED...WHILE
THE SRN STREAM IS LOCATED OVER THE SRN CONUS. THIS LEAVES THE AREA
WITH FAIRLY QUIET AND SEASONABLE CONDITIONS. SFC RIDGE WILL BE OVER
THE CWA AT THE START OF TUES...WITH ANOTHER SHORTWAVE MOVING THROUGH
SRN CANADA IN THE NRN STREAM. AS WITH THE SYSTEM TODAY...MAIN
ENERGY/MOISTURE WILL BE JUST TO THE N OF THE AREA...BRUSHING NRN LK
SUPERIOR. AS THIS QUICKLY MOVES E TUES EVENING...WEAK SFC RIDGE WILL
LIKELY BUILD BACK OVER THE AREA FOR TUES NIGHT INTO WED MORNING.
SEASONABLE TEMPS WILL CONTINUE...ALTHOUGH THE GUSTY WINDS AT TIMES
WILL MAKE IT FEEL A LITTLE COOLER.
DIFFERENCES START TO APPEAR IN THE EXTENDED MODELS WED INTO THURS
NIGHT WITH THE HANDLING OF THE EASTWARD MOVING UPPER LOW IN THE SRN
STREAM THAT WILL BE OVER THE CNTRL ROCKIES ON WED. ANOTHER NRN
STREAM TROUGH WILL BE DROPPING THROUGH THE CANADIAN ROCKIES AT THIS
TIME AND THEY WILL TRY TO MERGE THE NRN/SRN STREAMS OVER THE GREAT
LAKES REGION. 00Z RUNS OF THE GFS/ECMWF/GEM HAVE SPED UP THE EXITING
SRN STREAM WAVE...PUSHING IT THROUGH THE LOWER GREAT LKS AND OHIO
VALLEY BY 06Z THURS. AT THAT TIME...NRN STREAM WAVE WILL BE
APPROACHING THE UPPER GREAT LKS AND PASS THROUGH ON THURS.
THUS...WILL CONTINUE TO MENTION PCPN CHANCES DURING THAT
TIME...MAINLY DUE TO THE APPROACHING NRN STREAM WAVE.
BEHIND THESE DISTURBANCES...COLDER H850 TEMPS /TOWARDS -14C/ WILL
FILTER OVER THE UPPER GREAT LKS THURS INTO FRI AND LEAD TO LES UNDER
NWRLY FLOW. BEST CHANCES LOOK TO BE THURS INTO FRI MORNING WITH
ADDITIONAL MOISTURE FROM THE UPPER TROUGH...BEFORE SFC HIGH BEGINS
TO PULL DRIER AIR AND WARMER TEMPS ALOFT IN ON FRI AFTN. HAVE STUCK
WITH LOW CHANCES FOR NOW...BUT MAY NEED TO BUMP UP POPS IF
CONDITIONS REMAIN FAVORABLE. SWRLY FLOW WILL REDEVELOP FRI NIGHT AND
CONTINUE INTO SAT...AHEAD OF THE NEXT NRN STREAM SHORTWAVE TO AFFECT
THE AREA LATE SAT.
&&
.AVIATION /FOR THE 18Z TAF ISSUANCE/...
INCREASING SW SFC WINDS WILL CONTINUE THROUGH THE EARLY EVENING
HOURS...WHEN WINDS DECOUPLE/INVERSION TAKES HOLD AND THE STRONGEST
WINDS REMAIN ALOFT. THESE STRONG WINDS AROUND 50KTS AROUND 2KFT
ABOVE THE SFC WILL GREATLY DIMINISH TO AROUND 25KTS BETWEEN 03Z AND
06Z MONDAY /WEST TO EAST/. AS A RESULT...WILL KEEP LLWS AT ALL SITES
THROUGH THE MID TO LATE EVENING HOURS. A TROUGH/COLD FRONT SWINGING
WEST TO EAST OVERNIGHT WILL PUSH WINDS TO A MORE NW DIRECTION...AS
WELL AS INCREASED LOW LEVEL MOISTURE AND PLENTY OF COLD AIR. EXPECT
MVFR TO HIGH END IFR CEIGS POSSIBLE BEHIND THE COLD FRONT /LOWEST AT
CMX AND IWD GIVEN THE FAVORABLE NW UPSLOPE WINDS OFF LS/...WITH ONLY
MINIMAL IMPROVEMENT BY 18Z MONDAY PRIMARILY WEST AS DRIER AIR WORKS
IN.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
AS PRES GRADIENT TIGHTENS WITH LOW PRES MOVING ACROSS MANITOBA INTO
NRN ONTARIO...SW WINDS WILL BE ON THE INCREASE TODAY. ALTHOUGH
INVERSION WILL LIMIT NEAR SFC WINDS FROM BEING STRONGER...AREA OF
PRES FALLS ON THE ORDER OF 6MB/3HR PASSING OVER AND JUST N OF LAKE
SUPERIOR WILL WORK TO BOOST WINDS TO GALE FORCE OVER CNTRL AND ERN
LAKE SUPERIOR LATER THIS AFTERNOON AND TONIGHT. HIGHEST WINDS...
PERHAPS GUSTING TO AROUND 40KT...WILL LIKELY OCCUR OVER EASTERN
PORTIONS OF THE LAKE FROM STANNARD ROCK EASTWARD DUE TO FAVORABLE
POSITIONING OF PRES FALLS. AREA AROUND GRAND MARAIS SHOULD BE
ESPECIALLY FAVORED FOR STRONGER WINDS FOR A FEW HRS THIS EVENING.
AFTER COLD FRONTAL PASSAGE TONIGHT ASSOCIATED WITH THE LOW PRES
SYSTEM...NW WINDS WILL PROBABLY GUST TO AROUND 35KT OVER THE E HALF
OF THE LAKE INTO MON MORNING. WINDS WILL DIMINISH W TO E MON
AFTN/NIGHT AS HIGH PRES SYSTEM QUICKLY PASSES ACROSS THE GREAT
LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL PROBABLY
BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR. SW
WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE
FOR STRONGEST WINDS TUE. GALES WILL END TUE NIGHT AS PRES GRADIENT
WEAKENS. WINDS WILL BE BLO 30KT FOR WED/THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 1 PM EST MONDAY FOR LSZ266-267.
GALE WARNING UNTIL 7 AM EST MONDAY FOR LSZ264.
GALE WARNING UNTIL 1 AM EST MONDAY FOR LSZ263.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 AM EST MONDAY FOR
LMZ248-250.
&&
$$
DISCUSSION...SRF
AVIATION...KF
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1128 AM CST SUN DEC 18 2011
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYZES CONTINUE TO
SHOW A CUTOFF UPPER LOW OVER THE SOUTHWEST US WITH A BROAD RIDGE
OVER-TOP OF IT EXTENDING FROM THE PACIFIC NORTHWEST COAST INTO THE
UPPER MIDWEST. THE DEEP UPPER LOW NORTH OF HUDSON BAY HAS MOVED
LITTLE OF LATE... AND SHOW NO SIGNS OF GOING ANYWHERE THROUGH AT
LEAST THE NEXT 10 DAYS ON THE GFS... ECMWF... AND THEIR RESPECTIVE
ENSEMBLES. IN THE BIG PICTURE... THIS SUGGESTS CONDITIONS IN OUR
NECK OF THE WOOD SHOULDN/T CHANGE TOO MUCH THROUGH AT LEAST THE
NEXT WEEK OR TWO... WITH NEAR TO ABOVE NORMAL TEMPERATURES
PREDOMINATING AS WEST TO NORTHWEST MID-UPPER LEVEL FLOW CONTINUES
TO BRING SYSTEMS OF PACIFIC ORIGIN INTO OUR AREA. WE WILL CONTINUE
TO SEE FAIRLY FREQUENT COLD FRONTAL PASSAGES... BUT NONE LOOK TO
BRING ANY TRUE ARCTIC AIR INTO THE REGION... AND INSTEAD WILL
SIMPLY BRING TEMPERATURES DOWN TO NEAR OR PERHAPS SLIGHTLY BELOW
NORMAL FOR BRIEF PERIODS OF TIME AS THEY MOVE THROUGH. AS FAR AS
PRECIPITATION GOES... THE PRESENT LONG WAVE PATTERN IS NOT
CONDUCIVE TO US SEEING MUCH... WITH MINIMAL MOISTURE RETURN AHEAD
OF INDIVIDUAL SHORTWAVES... AND THE DEEPENING OF SYSTEMS OCCURRING
SOUTH AND EAST OF OUR AREA AS THEY MOVE INTO THE MEAN LONG WAVE
TROUGH POSITION.
ROBUST WARM ADVECTION WILL OCCUR ACROSS THE AREA TODAY... WITH
TEMPERATURES SOARING INTO THE 40S IN MOST LOCATIONS... AND LIKELY
ECLIPSING THE 50 DEGREE MARK OVER WEST CENTRAL AND SOUTHWEST
MINNESOTA. IT ISN/T TOO OFTEN WE SEE 850MB TEMPERATURES IN EXCESS
OF 8C... BUT THAT LOOKS TO BE THE CASE TODAY OVER THE SOUTHERN
PART OF THE STATE. WE CERTAINLY WON/T MIX TO 850MB... BUT EVEN
MIXING THROUGH 950MB WILL ALLOW TEMPERATURES TO CLIMB TO AOA 50
DEGREES OVER MANY AREAS SOUTH AND WEST OF THE TWIN CITIES.
WOULDN/T BE SHOCKED IF THE TWIN CITIES MANAGES TO GET CLOSE TO 50
DEGREES DEPENDING UPON HOW WELL THINGS MIX OR IF WE/RE ABLE TO
ADVECT SOME OF THE WARMER UPSTREAM READINGS INTO THE AREA DURING
THE AFTERNOON HOURS. JUST NUDGED READINGS UP SLIGHTLY OVER
PREVIOUSLY FORECAST VALUES... BUT IT WILL CERTAINLY BE SOMETHING
TO KEEP AN EYE ON TODAY. LOW PRESSURE ASSOCIATED WITH THE
SHORTWAVE CURRENTLY SEEN MOVING INTO ALBERTA WILL PASS BY NORTH OF
THE STATE THIS EVENING... DRAGGING A COLD FRONT ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. THIS WILL COOL THINGS DOWN
TO ABOUT WHERE THEY SHOULD BE FOR MONDAY. A FEW FLURRIES COULD BE
SEEN BEHIND THE FRONT DEPENDING UPON HOW DEEP THE MOISTURE IS
BENEATH THE SUBSIDENCE INVERSION AND IF CYCLONIC BOUNDARY LAYER
FLOW IS ABLE TO LINGER. AT THIS POINT... THE CHANCES LOOK MINIMAL
AND IT WOULD ONLY BE SCATTERED FLURRIES AT BEST... SO LEFT IT OUT
OF THE FORECAST.
HIGH PRESSURE WILL BUILD ACROSS THE REGION MONDAY AFTER THROUGH
MONDAY NIGHT... AS THE 850-700MB THERMAL TROUGH MOVES ACROSS THE
AREA AND WEAKENS. THIS WILL BRING WHAT WILL FEEL LIKE A CHILLY
NIGHT MONDAY NIGHT... ALTHOUGH READINGS STILL LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL. WEAK WARM ADVECTION LOOKS TO BE IN PLACE
ACROSS THE REGION TUESDAY AND TUESDAY NIGHT AS A SHORTWAVE AND
SURFACE LOW MOVE BY WELL NORTH OF THE US/CANADA BORDER... AND A
SURFACE LOW ASSOCIATED WITH THE CUTOFF LOW CURRENTLY OVER THE
SOUTHWEST MOVES OUT OF THE SOUTHERN PLAINS TO THE OHIO VALLEY. WE
WILL FIND OURSELVES NESTLED BETWEEN THESE FEATURES... WITH BENIGN
WEATHER IN PLACE. A SLOWLY MOVING COLD FRONT WILL DROP SOUTH
THROUGH THE REGION WEDNESDAY INTO THURSDAY. THERE ARE SOME HINTS
WE COULD SEE MOISTURE POOL SUFFICIENTLY ALONG THIS BAROCLINIC ZONE
TO GET SOME PCPN DEPENDING UPON WHEN THE UPSTREAM SHORTWAVE
DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA IS ABLE TO CATCH UP
WITH IT. GIVEN UNCERTAINTIES IN NOT ONLY IF SOME PCPN WILL BE
SQUEEZED OUT... BUT WHEN AND WHERE IT MIGHT OCCUR... CHOSE TO
LEAVE PCPN OUT OF THE FORECAST IN THE WEDNESDAY TO THURSDAY TIME
FRAME... BUT FEEL THERE IS AT LEAST A CHANCE FOR SOME FLURRIES OF
VERY LIGHT SNOW DURING THAT PERIOD WHICH MAY GET INCLUDED AS WE
GET CLOSER TO THAT TIME PERIOD. THE MEDIUM RANGE GUIDANCE BECOMES
QUITE MUDDY IN ITS AGREEMENT BY WEEK/S END... WITH THE
DETERMINISTIC GFS AND ECMWF DIFFERING BY 15-20MB IN SURFACE
PRESSURES OVER OUR AREA BY FRIDAY AS THE GFS CLOSES OFF A SURFACE
LOW IN THE SAME AREA WHERE THE ECMWF SUGGESTS A FAIRLY POTENT
RIDGE. THE ECMWF SOLUTION WOULDN/T SUPPORT ANY PCPN... AND THE GFS
WOULD SUGGEST VERY LITTLE... SO THE PATH OF LEAST RESISTANCE AT
THIS POINT IS SIMPLY TO KEEP THINGS DRY.
&&
.AVIATION.../18Z TAF ISSUANCE/
NO AVIATION CONCERNS IN THE FIRST 6 TO 12 HRS WITH VFR CONDITIONS
PREVAILING...WITH WNDS FROM THE SW/S...BECOMING MORE W IN WESTERN
MN...AND SW IN EASTERN MN. SOME GUSTS UP TO 18-22 KTS ARE POSSIBLE
AT RWF/AXN/STC THIS AFTN. EAU/RNH WILL LIKELY REMAIN AOB 12 KTS
FROM THE SSW THIS AFTN...THAN MORE SW BY 23Z. AFT 6Z...A FRONTAL
BOUNDARY AND FAIRLY SHALLOW MOISTURE WILL MOVE SOUTHWARD ACROSS
THE FA. THERE REMAINS SOME CONCERN WITH MVFR CIGS DEVELOPING
ALONG AND BEHIND THIS FRONT. HOWEVER...MODELS SLOWLY DECREASE THE
LOW LEVEL MOISTURE AS IT HEADS TO THE S OVERNIGHT. CONFIDENCE
REMAINS LOW ON MVFR CIGS DEVELOPING. AFT 15Z...ALL AREAS SHOULD
LIFT TO VFR WITH CIGS AOA 4K. WNDS WILL INCREASING SLIGHTLY DURING
THE MORNING WITH SOME GUSTS FROM THE NW/NNW.
MSP...VFR CONDITIONS THRU 6Z WITH WNDS BECOMING MORE SW...THEN WSW
LATE THIS AFTN/EVENING. AFT 9Z...WNDS WILL SHIFT TO THE NW WITH
MVFR CIGS DEVELOPING. CONFIDENCE REMAINS LOW ON MVFR CIGS
ATTM...BUT ENOUGH TO WARRANT A PERIOD FROM 9-14Z. NO OTHER CHGS
EXPECTED AFT 15Z...WITH WNDS GENERALLY FROM THE NW/NNW ARND 10
KTS.
MON/TUE/WED...VFR CONDITIONS EXPECTED.
..JLT..
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/JLT
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
407 PM CST SUN DEC 18 2011
.DISCUSSION...
12Z UPPER AIR ANALYSIS INDICATED THAT A CUT OFF LOW REMAINED IN
PLACE OVER FAR SOUTHERN CA WITH RIDGING OVER THE GULF OF MEXICO.
THIS LEFT SOUTHWEST FLOW ALOFT OVER THE SOUTHERN PLAINS OUT AHEAD
OF THE UPPER LOW. SOUTHWEST FLOW ALOFT HAD LED TO THE ADVECTION OF
STEEP LAPSE RATES INTO WEST TX THIS MORNING WITH A TEMPERATURE
DIFFERENCE IN THE H700 TO H500 LAYER OF 22 DEG C. A POOL OF 10 DEG
C DEW POINTS WAS OBSERVED AT THE H850 LEVEL OVER FAR SOUTH TX AND
THE EFFECTS OF LEE SIDE CYCLOGENESIS WERE BECOMING EVIDENT WITH
THE DEVELOPMENT OF A CYCLONIC CIRCULATION OVER FAR WEST TX. 21Z
SFC ANALYSIS INDICATED THAT A MOISTURE WAS RAPIDLY RETURNING TO
WESTERN AND CENTRAL TX WITH 45 DEG F DEW POINTS OBSERVED AS VAR
NORTH AS CHILDRESS.
TONIGHT THROUGH TUESDAY...AFTERNOON WATER VAPOR IMAGERY INDICATED
THAT THE CUT OFF LOW AS ALREADY BEGINNING TO MOVE EAST AND THE
CENTER OF CIRCULATION HAD JUST CROSSED OVER THE SOUTHERN AZ BORDER
AS OF 21Z. A PLUME OF PACIFIC MOISTURE HAS ALREADY BEEN ADVECTED
OVER MUCH OF THE SOUTHERN PLAINS...AND SOUTHWEST FLOW ALOFT
CONTINUES THIS TRANSPORT OF MID TO UPPER TROPOSPHERIC MOISTURE
INTO THE REGION. THE PROGRESSION OF SURFACE DEW POINTS WAS THE
MOST INTERESTING PIECE OF INFORMATION THAT COULD BE OBSERVED ABOUT
THE POTENTIAL THERMODYNAMIC ENVIRONMENT THIS AFTERNOON AHEAD OF
THIS UPPER LOW. BASED ON 12Z GUIDANCE...THE NAM WAS THE ONLY MODEL
TO SUFFICIENTLY HANDLE THE RAPID INFLUX OF LOW LEVEL MOISTURE INTO
TX. THE NAM HAD ROUGHLY AN ACCURATE REPRESENTATION OF 21Z DEW
POINTS ACROSS TX WITH THE GFS LAGGING BEHIND BY 6 HRS AND THE
ECMWF COMING IN A FEW DEG F TOO LOW FOR ITS 00Z FORECAST THIS
EVENING. EVEN THE 18Z INITIALIZATION OF THE RUC IS SLOW ON THIS
MOISTURE TRANSPORT WHICH POINTS TO A POTENTIALLY SIGNIFICANT
SOURCE OF ERROR WITH REGARDS TO HANDLING THE THERMODYNAMIC
ENVIRONMENT THAT WILL SET UP OVER NORTH TX TOMORROW.
DID NOT CHANGE MUCH WITH REGARDS TO THE TIMING OF EXPECTED
PRECIPITATION ACROSS NORTH TX WITH THIS FORECAST PACKAGE. THE
UPPER LEVEL SYSTEM AND ASSOCIATED FRONTAL BOUNDARIES ARE EXPECTED
TO MOVE THRU NORTH TX AT ROUGHLY THE SAME TIME AS THE PREVIOUS
FORECAST INDICATED. THE UPPER LOW IS EXPECTED TO MOVE INTO THE
SOUTHERN PLAINS TOMORROW EVENING AND THEN BECOME NEGATIVELY TILTED
AS IT MOVES NORTHEAST OVER NORTH CENTRAL TX AND OVER OK MONDAY
NIGHT. STRONG LARGE SCALE FORCING FOR ASCENT WILL SPREAD OVER
NORTH TX AHEAD OF THIS UPPER LOW...WITH MAXIMUM ASCENT SPREADING
OVER THE FORECAST AREA FROM 21Z MONDAY TO 06Z TUESDAY. THE
FORECAST STRENGTH OF THE UPPER LOW AS IT MOVES OVER THE SOUTHERN
PLAINS IS HIGH WITH H500 HEIGHTS REGISTERING AS A -2.5 STANDARD
DEVIATION ANOMALY PER HPCS ANALYSIS OF THE 12Z GFS. PRECIPITABLE
WATER VALUES CONTINUE TO BE FORECAST TO HOLD IN THE 99TH
PERCENTILE OVER NORTH TX FOR DECEMBER. THE 0 TO 6 KM BULK SHEAR
MAGNITUDE IS EXPECTED TO BE IN EXCESS OF 55 KTS DURING THE PERIOD
OF MAXIMUM FORCING FOR ASCENT WHICH SPEAKS TO THE STRENGTH OF THE
WIND FIELDS OUT AHEAD OF THIS SYSTEM. INSTABILITY CONTINUES TO BE
THE MOST DIFFICULT PARAMETER TO FORECAST...AND THE DEGREE OF
INSTABILITY WILL LARGELY DETERMINE OUR SEVERE WEATHER CHANCES AND
COVERAGE TOMORROW AFTERNOON.
BASED ON 21Z SURFACE OBS...THE NAM APPEARS TO HAVE THE BEST HANDLE
ON LOW LEVEL MOISTURE MOISTURE RETURN OUT AHEAD OF THIS SYSTEM.
MOISTURE TRANSPORT IS EXPECTED TO INCREASE IN INTENSITY TONIGHT
AND DURING THE DAY MONDAY AS THE UPPER LEVEL LOW MOVES OVER THE
SOUTHERN PLAINS. THE LOW LEVEL JET IS FORECAST TO INCREASE TO AT
LEAST 50 KTS OVER NORTH TX TOMORROW...WITH OUR LOCAL 4 KM WRF
INDICATING A POTENTIAL JET CORE OF 60 KTS AFTER 21Z. STRATUS IS
STILL EXPECTED TO BE IN PLACE OVER MOST OF THE OPEN WARM SECTOR
TOMORROW WHICH WILL BE A LIMITING FACTOR FOR LOW LEVEL
DESTABILIZATION. HOWEVER WITH MOISTURE TRANSPORT LIKELY
UNDERESTIMATED IN MOST OPERATIONAL GUIDANCE...THINK THAT SURFACE
BASED INSTABILITY IS LIKEWISE UNDERESTIMATED. 12Z MOS GUIDANCE IS
NOW CONSISTENT WITH MID 60S HIGHS FOR DFW TOMORROW. MOS GUIDANCE
ALSO INDICATES HIGHS IN THE UPPER 60S TO LOWER 70S FOR WACO
TOMORROW. THIS IS A FEW DEGREES WARMER THAN HIGHS WERE EXPECTED TO
CLIMB FROM YESTERDAYS FORECAST.
CONFIDENCE IN THESE HIGHER TEMPERATURES IS INCREASING DUE TO
SIGNIFICANT BREAKS IN CLOUD COVER OVER NORTH TX AND THE TX GULF
COAST. WARMER AFTERNOON TEMPERATURES TODAY WILL THEORETICALLY LEAD
TO WARMER OVERNIGHT LOWS ONCE CLOUD COVER BUILDS BACK IN TONIGHT.
THIS WOULD MEAN THAT LESS HEATING IS NECESSARY TO REACH HIGHER
TEMPERATURES TOMORROW AFTERNOON. THE 12 AND 18Z NAM RUNS BOTH
CONTINUE TO AGGRESSIVELY ADVERTISE FREE CONVECTION POTENTIAL
TOMORROW AFTERNOON AND EVENING. WITH THE NAM HAVING THE BEST
HANDLE ON LOW LEVEL MOISTURE AND HIGH TEMPERATURES LIKELY CLIMBING
A FEW DEGREES HIGHER TOMORROW THAN PREVIOUS EXPECTED...CONFIDENCE
IN THE NAMS THERMODYNAMIC SOLUTION HAS INCREASED SUBSTANTIALLY.
THE NAM ADVERTISES A CORRIDOR OF SURFACE BASED CAPE OF 1000 J/KG
EXTENDING FROM THE METROPLEX SOUTH...NEAR THE INTERSTATE 35
CORRIDOR BY 00Z TUE OR TOMORROW AT 6 PM.
AS PREVIOUS FORECAST MENTIONED...LOW LCL HEIGHTS INDICATE THAT A
SIGNIFICANT PORTION OF THE FREE CONVECTION POTENTIAL ENERGY /CAPE/
WILL LIE IN THE LOWEST 3 KMS. 0 TO 3 KM CAPE VALUES ARE FORECAST
TO BE IN EXCESS OF 200 J/KG WITHIN THIS SAME GENERAL CORRIDOR.
THESE VALUES ARE QUITE HIGH EVEN FOR A SPRING SEVERE WEATHER
EPISODE...AND HIGH LOW LEVEL CAPE VALUES SPEAK TO THE POTENTIAL
FOR LOW LEVEL STRETCHING AND TILTING OF HORIZONTAL VORTICITY INTO
THE VERTICAL. LOW LEVEL WIND PROFILES CONTINUE TO VEER WITH HEIGHT
AND CONTAIN SIGNIFICANT SPEED SHEAR DUE TO THE PRESENCE OF THE
STRONG LOW LEVEL JET. 0-1 KM HELICITY VALUES IN EXCESS OF 200
M2/S2 ARE PRESENT WITHIN THE CORRIDOR OF HIGH LOW LEVEL CAPE. THIS
COMBINATION OF PARAMETERS INDICATES THAT ANY UPDRAFT WILL HAVE A
STRONG LIKELIHOOD TO INGEST HORIZONTAL VORTICITY WHICH GREATLY
INCREASES THE SEVERE WEATHER THREAT TOMORROW AFTERNOON. THE
GENERAL STORM MODE IS STILL EXPECTED TO BE LINEAR WITH SIGNIFICANT
FORCING FOR ASCENT EXPECTED ALONG A PACIFIC TYPE COLD FRONT THAT
WILL MOVE TROUGH NORTH TX JUST AHEAD OF THE CORE OF THE UPPER LOW.
THIS NORTH/SOUTH ORIENTED FRONT IS ORIENTED NEARLY PARALLEL TO THE
0-6 KM BULK SHEAR VECTORS WHICH GENERALLY FAVORS SHARED COLD POOLS
LEADING TO A LINEAR STORM MODE.
EVEN WITH A LINEAR STORM MODE STRETCHING AND TILTING OF HORIZONTAL
VORTICITY INTO THE VERTICAL CAN LEAD TO THE DEVELOPMENT OF
MESOVORTICIES CAPABLE OF PRODUCING STRONG LOCALIZED WIND
DAMAGE...AND TO THE DEVELOPMENT OF BRIEF TORNADOES. ANY DISCRETE
STORMS OUT AHEAD OF LINE SEGMENT CONVECTION WILL LIKELY BE IN THE
FORM OF LOW-TOPPED AND VERY FAST MOVING SUPERCELLS. ANY LOW-TOPPED
SUPERCELL AWAY FROM THE MAIN LINE OF CONVECTION WILL BE CAPABLE OF
PRODUCING A TORNADO...ESPECIALLY SOUTH OF THE METROPLEX TOMORROW
AFTERNOON. THE MOST WIDESPREAD SEVERE WEATHER HAZARD IS THOUGHT
TO BE IN THE FORM OF STRAIGHT LINE WIND DAMAGE...AND THIS IS
MOSTLY DUE TO THE POTENTIAL FOR STRONG ENVIRONMENTAL WINDS TO BE
DRIVEN DOWN TO THE SURFACE. DEEP MOISTURE MEANS THAT THERE IS
LITTLE THETA-E DIFFERENCE WITH HEIGHT...AND THEREFORE LITTLE
POTENTIAL FOR ENHANCED DOWNDRAFT SPEEDS OR MICROBURSTS.
OVERALL CONFIDENCE IN AN ORGANIZED STORM MODE IS HIGH NOW FOR
TOMORROW AFTERNOON. DAMAGING STRAIGHT LINE WINDS WITH A HIGH
POTENTIAL FOR LOCALLY ENHANCED DAMAGE IS THE MOST PREVALENT SEVERE
WEATHER HAZARD. THERE IS AN ATTENDANT TORNADO THREAT TOMORROW
AFTERNOON...ESPECIALLY IF ANY DISCRETE STORMS ARE ABLE TO DEVELOP
OUT AHEAD OF THE SQUALL LINE/PACIFIC FRONT. 99TH PERCENTILE PWATS
ALWAYS RAISE THE POTENTIAL FOR LOCALIZED FLOODING ISSUES...HOWEVER
THE VERY FAST STORM MOTION IS EXPECTED TO MITIGATE SIGNIFICANT
FLOODING CONCERNS.
THE PACIFIC TYPE COLD FRONT IS EXPECTED TO MOVE EAST THRU MOST OF
NORTH TX BY MIDNIGHT /06Z TUE/ MONDAY NIGHT. THE ATTENDANT SQUALL
LINE WILL LIKELY BE JUST EXITING THE FORECAST AREA AT THIS TIME
SO HAVE LINGERED HIGH POPS OVER THE FAR EASTERN CWA AFTER
MIDNIGHT. BY TUESDAY MORNING THERE IS SOME LOW END POTENTIAL FOR
LIGHT RAIN ASSOCIATED WITH MOISTURE WRAPPED AROUND THE UPPER
LOW...ESPECIALLY AS SOME RESIDUAL FRONTOGENETIC FORCING BUILDS
INTO THE NORTHERN CWA AS THE CANADIAN AIRMASS RESPONSIBLE FOR THE
BLIZZARD PORTION OF THIS SYSTEM /OVER THE SOUTHERN HIGH PLAINS/
MOVES SOUTH INTO NORTH TX. NO WINTRY PRECIPITATION IS EXPECTED AT
THIS TIME AS THERE WILL BE VERY LITTLE MOISTURE LEFT TO WORK WITH
AND TEMPERATURES WILL GENERALLY REMAIN ABOVE FREEZING EARLY
TUESDAY MORNING BEHIND THE FRONT.
EXTENDED...NO SIGNIFICANT CHANGES MADE TO THE EXTENDED AT THIS
TIME. KEPT THE LOW END RAIN CHANCES OVER THE SOUTHEASTERN PORTION
OF THE CWA ON THURSDAY AS ANOTHER SHORTWAVE TROUGH MOVES OVER
NORTH TX. THE 12Z ECMWF WAS THE MOST AGGRESSIVE WITH PRECIPITATION
BECAUSE IT BRINGS THE WAVE OVER NORTH TX THE FURTHEST NORTH AND
STRONGER THAN THE GFS ADVERTISES. EITHER WAY LIMITED MOISTURE WILL
PREVENT SIGNIFICANT COVERAGE OF RAIN OVER NORTH TX ON THURSDAY.
MAINTAINED A DRY FORECAST FOR THE HOLIDAY WEEKEND AS RUN TO RUN
AND MODEL TO MODEL CONSISTENCY EVEN ON LARGE SCALE FLOW REMAINS
POOR AT THIS TIME. GENERAL CONSENSUS IS THAT TEMPERATURES WILL BE
BELOW NORMAL...SO FOR NOW A COOL AND DRY HOLIDAY WEEKEND IS
EXPECTED.
CAVANAUGH
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 51 64 45 50 31 / 10 80 100 5 5
WACO, TX 52 67 44 53 28 / 10 70 100 5 5
PARIS, TX 44 63 47 54 30 / 10 50 100 10 10
DENTON, TX 52 61 43 46 27 / 10 90 100 10 5
MCKINNEY, TX 48 62 45 50 30 / 10 80 100 5 5
DALLAS, TX 51 64 46 50 31 / 10 80 100 5 5
TERRELL, TX 48 64 49 53 31 / 10 50 100 5 5
CORSICANA, TX 48 66 47 55 32 / 10 50 100 5 5
TEMPLE, TX 50 66 43 55 29 / 10 70 100 5 5
MINERAL WELLS, TX 53 64 39 46 25 / 20 100 80 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LUBBOCK TX
1148 AM CST SUN DEC 18 2011
.AVIATION...
COMPLICATED FORECAST THIS PERIOD DUE TO RECENT DEVELOPMENT OF VFR
CONDITIONS. EARLIER MVFR CIGS AT LBB HAVE SINCE BEEN ERADICATED
BY DRIER AIR/DEEPER MIXING ALONG A LINE FROM BROWNFIELD-LUBBOCK-
NORTHEAST OF PLAINVIEW. LATEST RUC SUGGESTS THESE VFR CONDITIONS
WILL HOLD THROUGH THE DAY WITH STEADY SWLY WINDS...BUT A NWLY PUSH
OF DEEPER MOISTURE OUT OF THE PERMIAN BASIN COULD THREATEN THIS
WITH A RETURN TO MVFR DECKS BEFORE SUNSET. FOR NOW IT APPEARS
SCT LOW CLOUDS WILL PREVAIL AT LBB INTO THE EVENING. THE MOIST
PUSH WILL BE REINFORCED TONIGHT AS WINDS BACK SELY WELL AHEAD OF A
POWERFUL UPPER CYCLONE. CONFIDENCE IS HIGH THAT PROLONGED IFR
CIGS AND REDUCED VISBYS WILL UNFOLD AT LBB AROUND MIDNIGHT BEFORE
DRIZZLE/RAIN/ISOLATED TSRA EMERGE EARLY MON MORNING. PRECIPITATION
MAY BE HEAVY AT TIMES /ESPECIALLY AT CDS/ BUT WILL REMAIN ALL
LIQUID THROUGH 19/18Z BEFORE A STRONG COLD FRONT CHANGES RAIN OVER
TO LIGHT SNOW WELL AFTER THIS TAF WINDOW.
&&
PREV DISCUSSION... /ISSUED 515 AM CST SUN DEC 18 2011/
SHORT TERM...
IMPENDING WINTER STORM IS STILL THE MAIN FOCUS IN THE FORECAST BUT
THE SHORT TERM FORECAST WILL SEE INCREASING CHANCES OF PRECIPITATION
AHEAD OF THE SYSTEM. THE CENTER OF THE UPPER LOW WAS NEARLY ONSHORE
IN BAJA CALIFORNIA EARLY THIS MORNING. THE SYSTEM WILL THEN BEGIN
ITS MARCH EASTWARD TO A LOCATION JUST EAST OF EL PASO BY 12Z MONDAY.
HEIGHTS WILL BEGIN A RAPID DESCENT EARLY MONDAY MORNING ALONG WITH
DIFFLUENCE IN THE UPPER LEVEL WIND FIELDS. THE UPPER LEVEL LIFT FROM
THE LOW WILL BEGIN TO SPREAD OVER THE REGION FROM WEST TO EAST BY
DAYBREAK MONDAY MORNING. AT THE SAME TIME...A LOW LEVEL JET WILL
DEVELOP WITH GOOD ISENTROPIC LIFT SPREADING INTO THE AREA. MOIST LOW
AND UPPER LEVELS WILL BE PREVALENT AT THIS TIME WITH MID LEVEL
SLOWLY MOISTENING. OVERNIGHT TONIGHT...LOW LEVEL MOISTURE WILL
CONTINUE TO SURGE NORTHWARD WITH WINDS SLIGHTLY BACKING TO THE SSE.
PRECIPITATION WILL START OUT AS ALL LIQUID AT THE SURFACE THROUGH
MONDAY MORNING. FOR SUNDAY...LOW STRATUS WILL STICK AROUND AND MAY
BE ABLE TO SQUEEZE OUT A FEW SPRINKLES THIS AFTERNOON AND EVENING.
JDV
LONG TERM...
SOLUTIONS REMAIN TIGHTLY CLUSTERED WITH UPPER LEVEL LOW PRESSURE
MOVING ACROSS SOUTHEAST NEW MEXICO 18Z MONDAY...NEAR LITTLEFIELD
00Z TUESDAY...AND AROUND CLARENDON BY 06Z TUESDAY. THE LATEST RUNS
HAVE WOBBLED BACK A BIT TO THE NORTH BUT REMAIN CONSISTENT ENOUGH
TO RAISE OUR CONFIDENCE IN A POTENTIAL WINTER STORM EVENT OVER THE
FAR NORTHWESTERN SOUTH PLAINS AND EXTREME SOUTHERN TEXAS PANHANDLE.
WE REMAIN SUSPICIOUS OF THIS LEVEL OF AGREEMENT AND ARE RELUCTANT
TO USE MODELS QUITE SO DETERMINISTICALLY. THEREFORE WE HAVE INCLUDED
THE NORTHWESTERN SOUTH PLAINS IN A WINTER STORM WATCH AS A BUFFER
FOR THE MORE PRONE EXTREME SOUTHWEST AND SOUTH-CENTRAL PANHANDLE
ZONES.
OTHER CHANGES THIS GO-AROUND INCLUDE SLIGHTLY DELAYING THE COLD
FRONT PASSAGE THROUGH OUR NORTHWESTERN ZONES UNTIL MID OR LATE
AFTERNOON FOR SOME AREAS. ALTHOUGH COLUMN COOLING WILL BE GOING ON
STRONG...THIS MAY DELAY POSSIBLE CHANGE-OVER TO FROZEN PRECIPITATION
STAGE UNTIL LATER MONDAY FOR MOST NORTHWESTERN ZONES. IT STILL LOOKS
LIKELY THAT THE SOUTHWESTERN SOUTH PLAINS COUNTIES WILL BECOME
DRY-SLOTTED FOLLOWING A POTENTIAL HEALTHY SHOWER OR THUNDERSTORM
EVENT AROUND AND JUST AFTER DAYBREAK MONDAY MORNING...BUT COLD AIR
NOT EXPECTED TO ARRIVE IN TIME FOR FROZEN STAGE SWITCH-OVER INTO
CENTRAL SOUTH PLAINS BEFORE MOST OF THIS PRECIPITATION MOVES AWAY
FROM THE AREA. CENTRAL AREAS WILL NEED FRONTO-GENETIC FORCING AND
POSSIBLE WEAK SOUTHERN EXTENSION OF THE TROWEL LATE MONDAY NIGHT
FOR MUCH PRECIPITATION OPPORTUNITY. AND GIVEN THE LATEST TRENDS OF
PASSAGE SLIGHTLY FURTHER NORTH...SIGNIFICANT COLD PHASE PRECIPITATION
SEEMS UNLIKELY AT THE MOMENT.
ACROSS NORTHERN ZONES LATE MONDAY AND EARLY MONDAY NIGHT...
FRONTOGENETIC FORCING SHOULD BE AUGMENTED BY AT LEAST SOMEWHAT
STRONGER MID LEVEL LIFT AND REMNANT INSTABILITY FOR AN OPPORTUNITY
TO PRODUCE HEAVIER SNOW RATES. HOWEVER...AVAILABILITY OF
SIGNIFICANT DENDRITES STILL IN DOUBT. A MAJOR WINTER STORM MOST
LIKELY WILL REQUIRE THIS ELEMENT WHICH APPEARS MUCH MORE CERTAIN
FROM NORTHEASTERN NEW MEXICO ACROSS THE NORTHERN TEXAS PANHANDLE.
ANYWAY...THIS WAS ONE OF THE ELEMENTS THAT DELAYED US REACHING
SUFFICIENT CONFIDENCE LEVELS EARLIER FOR A WINTER STORM WATCH AND
STILL REMAINS A CONCERN. HOWEVER...OTHER THRESHOLDS SUCH AS STORM
TRACK AND DEEPENING OF THE PARENT UPPER LOW REQUIRES NOW UPGRADING
THE SITUATION TO A WINTER STORM WATCH...ESPECIALLY SINCE START OF
THE EVENT IS NOW WITHIN 36 HOURS. WE HAVE INCREASED FORECAST SNOW
TOTALS SLIGHTLY ACROSS OUR FAR NORTHERN ZONES THOUGH REMAIN WITH
ONLY MODERATE SNOW AMOUNTS. ADDITION OF STIFF NORTHERLY WINDS
POTENTIALLY CLOSE TO 30 MPH AND THREAT OF BLOWING SNOW ADDS
ANOTHER LEVEL OF CONCERN FOR THIS POTENTIAL WINTER STORM.
SYSTEM SHOULD PASS TO THE EAST FAIRLY QUICKLY EARLY TUESDAY.
TEMPERATURES FOR A DAY OR TWO FOLLOWING WILL BE TRICKY DEPENDING
ON ANY SNOW COVER. MOSTLY DRY POSITIVE TILTED TROUGH PASSAGE
EXPECTED EARLY THURSDAY WITH A COOL SURFACE RIDGE MOVING IN.
ANOTHER POTENTIALLY MORE POTENT UPPER TROUGH APPEARS WILL APPROACH
AND PASS JUST NORTH OF THE AREA FRIDAY...DRY MOST LIKELY FOR US...
BUT YET ANOTHER CHILLY AIRMASS SETTLING IN FOR THE WEEKEND. RMCQUEEN
&&
.PRELIMINARY POINT TEMPS/POPS...
FRIONA 55 36 38 21 34 / 10 60 90 60 10
TULIA 56 42 42 22 35 / 10 60 90 70 10
PLAINVIEW 55 43 44 23 37 / 10 60 90 60 10
LEVELLAND 54 43 45 24 40 / 10 70 70 40 10
LUBBOCK 54 45 46 25 39 / 10 60 70 50 10
DENVER CITY 54 42 48 25 44 / 10 70 70 40 0
BROWNFIELD 55 44 49 26 42 / 10 70 70 40 0
CHILDRESS 62 43 47 27 40 / 10 40 90 60 10
SPUR 58 45 51 28 43 / 10 50 80 40 10
ASPERMONT 61 46 54 30 45 / 10 50 70 40 10
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY
NIGHT FOR THE FOLLOWING ZONES: TXZ021>024-027>029.
&&
$$
99/99/93
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
227 PM CST SUN DEC 18 2011
.SHORT TERM...THROUGH TUESDAY NIGHT
227 PM CST SUN DEC 18 2011
MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES AND TYPES
TUESDAY AND TUESDAY NIGHT.
SURFACE ANALYSIS THIS AFTERNOON SHOWS AN AREA OF LOW PRESSURE OVER
SOUTHWEST ONTARIO WITH A COLD FRONT EXTENDING SOUTHWEST THROUGH
NORTH DAKOTA.
THE COLD FRONT WILL SLIDE ACROSS THE REGION OVERNIGHT. AS IT
DOES...THE 18.12Z NAM AND 18.18Z RUC SUGGEST THERE WILL BE A
RIBBON OF LOW LEVEL MOISTURE BEHIND THE FRONT THAT SHOULD BE
SUFFICIENT TO ALLOW SATURATION TO OCCUR. THIS SHOULD RESULT IN A
BAND OF STRATUS CLOUDS DEVELOPING ACROSS THE REGION AND HAVE
RAISED THE CLOUD COVER TO HANDLE THIS. OBSERVATIONS ACROSS
SASKATCHEWAN AND MANITOBA DO INDICATE THE EXISTENCE OF THIS
STRATUS ALREADY. THE NAM BUFKIT SOUNDINGS INDICATE SOME VERTICAL
MOTION THROUGH THIS SATURATED LAYER SUGGESTING THE POTENTIAL FOR
SOME DRIZZLE. HOWEVER...THE RUC DOES NOT SHOW THIS AND WILL LEAVE
OUT THE MENTION OF ANY DRIZZLE.
THE FRONT WILL BECOME STATIONARY SOUTH OF THE AREA MONDAY NIGHT AS
THE UPPER LEVEL LOW OVER THE SOUTHWEST STARTS TO EJECT OUT TO THE
NORTHEAST. AS THIS SYSTEM COMES OUT...BOTH THE NAM AND GFS BRING
BETWEEN 4 AND 8 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB
LAYER ACROSS THE SOUTHERN PARTS OF THE FORECAST AREA TUESDAY AND
TUESDAY NIGHT. THIS IS EXPECTED TO RESULT IN WEAK TO MODERATE QG
CONVERGENCE OCCURRING ACROSS THE FAR SOUTHERN PARTS OF THE
FORECAST AREA. THERE SHOULD ALSO BE SOME WEAK FRONTOGENESIS IN THE
850-500 MB LAYER OF THE SAME AREA. THERE IS ENOUGH OF A CONSENSUS
IN ALL THE MODELS TO BRING THE PRECIPITATION CHANCES TO ABOUT THE
INTERSTATE 90 CORRIDOR TUESDAY AFTERNOON AND NIGHT. BUFKIT
SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST THERE MAY NOT BE A LOT
OF ICE PRESENT IN THE CLOUDS AS THIS SYSTEM COMES THROUGH. THE
SOUNDINGS SUGGEST CLOUD TOP TEMPERATURES MAY BE IN THE -10 TO -12C
RANGE AND THERE COULD ALSO BE A BIT OF A WARM LAYER ALOFT AT TIMES
AS WELL. HAVE THUS ADDED IN SOME PROBABILITIES OF FREEZING RAIN
AND WILL HAVE A MIXTURE OF RAIN...SNOW AND FREEZING RAIN. ACTUAL
PRECIPITATION AMOUNTS SHOULD BE VERY LIGHT AND ANY SNOW OR ICE
ACCUMULATIONS THAT OCCUR SHOULD NOT AMOUNT TO MUCH.
.LONG TERM...WEDNESDAY THROUGH SUNDAY
227 PM CST SUN DEC 18 2011
AS THE SYSTEM PULLS AWAY FROM THE AREA WEDNESDAY...THERE COULD
STILL BE A LITTLE BIT OF LINGERING PRECIPITATION ACROSS THE FAR
SOUTHEASTERN PARTS OF THE FORECAST AREA. THE NEXT NORTHERN STREAM
SHORT WAVE TROUGH IS EXPECTED TO COME ACROSS THE UPPER MIDWEST
WEDNESDAY NIGHT AND THURSDAY. MODELS HAVE BEEN INCONSISTENT ON
WHETHER THIS WILL BE ENOUGH TO PRODUCE SOME LIGHT SNOW AS THE WEAK
COLD FRONT COMES THROUGH. FOR NOW...WILL STAY WITH THE CURRENT
MODEL CONSENSUS GRIDS SHOWING THE SNOW CHANCES FARTHER NORTH
CLOSER TO THE SHORT WAVE TROUGH...BUT COULD SEE LATER FORECASTS
ADDING IN SOME SNOW CHANCES FOR THIS SYSTEM. ANOTHER WAVE WILL BE
DROPPING INTO THE UPPER MIDWEST NEXT SUNDAY AND WILL HAVE SOME
SMALL SNOW CHANCES ACROSS THE NORTH WITH THIS SYSTEM.
&&
.AVIATION...THROUGH 18Z MONDAY
1148 AM CST SUN DEC 18 2011
MAIN CONCERN WILL BE COLD FRONTAL PASSAGE TONIGHT ALONG WITH IFR
STRATUS. CURRENTLY...VFR CONDITIONS ACROSS THE AREA WITH MILD
SOUTHWEST FLOW AHEAD OF AN AREA OF LOW PRESSURE TRACKING ALONG THE
U.S./CANADIAN BORDER. A COLD FRONT ASSOCIATED WITH THE LOW WILL
DROP INTO THE AREA LATER THIS EVENING AND EXIT BY DAYBREAK.
WARMING TODAY HAS CAUSED SNOWMELT AND CONSEQUENTLY IS LOADING THE
BOUNDARY LAYER WITH MOISTURE. THIS MOISTURE IS EXPECTED TO
CONVERGE ALONG THE COLD FRONT AS IT DROPS INTO THE AREA LATE THIS
EVENING...AND IS EXPECTED TO PRODUCE SCATTERED STRATUS. BY
08-09Z...COLDER AIR FILTERING INT BEHIND THE FRONT ON NORTHERLY
WINDS IS EXPECTED TO COOL THE RELATIVELY MOIST BOUNDARY LAYER FOR
MORE WIDESPREAD IFR STRATUS FORMATION. THIS IFR STRATUS IS
EXPECTED TO LINGER THROUGH MONDAY MORNING AS MOISTURE IS TRAPPED
BELOW A SUBSIDENCE INVERSION ASSOCIATED WITH A RIDGE OF HIGH
PRESSURE EXTENDING FROM THE NORTHERN PLAINS INTO NORTHERN WI.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
227 PM CST SUN DEC 18 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...DAS