Forecast Discussions mentioning any of "HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 09/10/12


AREA FORECAST DISCUSSION
NWS PHOENIX AZ
945 AM MST SAT SEP 8 2012 .SYNOPSIS... A VERY MOIST AND UNSTABLE MONSOON AIRMASS WILL CONTINUE TO COVER THE REGION THROUGH EARLY NEXT WEEK...AND LEAD TO A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY. THUNDERSTORM COVERAGE AND INTENSITY WILL VARY FROM DAY TO DAY...WITH SOMEWHAT BETTER CHANCES EXPECTED OVER THE WEEKEND AND INTO MONDAY. HIGH TEMPERATURES WILL REMAIN BELOW SEASONAL NORMALS EACH DAY GIVEN THE HIGH MOISTURE CONTENT IN THE ATMOSPHERE. && .DISCUSSION... LATEST RAP INDICATES THE CENTER OF THE CYCLONIC CIRCULATION HAS DRIFTED SOUTHWESTWARD INTO THE GULF OF CALIFORNIA. THIS PLACES THE STRONGEST MID-LEVEL NORTHEASTERLY FLOW AND EFFECTIVE SHEAR NEAR YUMA. LATEST 12Z NAM APPEARS TO HAVE INITIALIZED WELL AND SUGGESTS THE STRONGEST UVV AND PRECIPITATION CHANCES WILL BE CONCENTRATED ACROSS SOUTHERN AZ. THIS SEEMS REASONABLE AND IS REFLECTED IN THE CURRENT FORECAST. ONLY MINOR ADJUSTMENTS TO SHORT-TERM MAX/HOURLY TEMPERATURES AND DEWPOINTS WERE NEEDED THIS MORNING. && .PREVIOUS DISCUSSION... EARLY MORNING SATELLITE AND RADAR IMAGERY REVEALS ABUNDANT CLOUD COVER ACROSS THE REGION...WITH A DECAYING COMPLEX OF STORMS ACROSS SOUTHERN NEW MEXICO AND A WEAK CIRCULATION NOTED ACROSS SOUTHERN ARIZONA. ONCE AGAIN THERE WAS ABUNDANT MOISTURE ACROSS THE AREA WITH BLENDED TPW PRODUCT INDICATING NEARLY 1.8 INCHES OF PW /NEARLY 200 PERCENT OF NORMAL/ ACROSS THE AREA ALTHOUGH THIS IS EXPECTED TO INCREASE LATER TODAY. WHAT ENDED UP BEING AN EXTREMELY ACTIVE DAY YESTERDAY MAY NOT END UP HINDERING OUR CHANCES OF STORMS TODAY. TYPICALLY ITS HARD TO GET BACK TO BACK DAYS OF STORMS /LOOKING AT SOUNDINGS AROUND THE AREA AT 00Z ITS EASY TO SEE THE BOUNDARY LAYER HAS BEEN OVERTURNED SUBSTANTIALLY/...HOWEVER AN INVERTED TROUGH PRESENTLY APPROACHING THE AREA FROM THE EAST AND ITS ASSOCIATED DYNAMICS SHOULD BE ENOUGH TO COMPENSATE FOR THE WELL OVERTURNED BOUNDARY LAYER. A FEW AIRCRAFT SOUNDINGS INDICATE THERE IS SOME CAPE TO BE HAD IN THE MID LEVELS OF THE ATMOSPHERE AND SURE ENOUGH...RADAR IMAGERY IS STARTING TO HINT AT A FEW VERY LIGHT SHOWERS DEVELOPING ACROSS ARIZONA AS OF 09Z. HOW QUICKLY STORMS WILL BLOSSOM HAS YET TO BE SEEN BUT GIVEN THE FACT THAT THEY ARE ALREADY FORMING...I AM INCLINED TO BRING IN POPS EARLIER THAN USUAL TO ALL LOCATIONS. FOR THE MORNING I WILL GO WITH 10-20 PERCENT POPS BUT QUICKLY INCREASE TO 30-40 FOR THE AFTERNOON/EVENING. IM A LITTLE HESITANT TO GO MUCH HIGHER THAN 30-40 PERCENT GIVEN JUST HOW POOR THE 00Z SOUNDING LOOKED AT PHOENIX LAST NIGHT BUT MAY TREND UPWARD AT THE LAST MINUTE ONCE THE 06Z NAM/GFS ARE BOTH AVAILABLE. MUCH OF THE SAME IS EXPECTED ON SUNDAY AS THE SLOW MOVING INVERTED TROUGH WILL REMAIN NEARLY STATIONARY. IF ANYTHING...THE BEST CHANCE FOR PRECIP MAY BE ORIENTED WEST OF PHOENIX ACROSS SW ARIZONA AND SE CALIFORNIA. THIS IS WELL AGREED UPON BY THE MODELS AND FITS WELL CONCEPTUALLY WITH THE PREVIOUS FORECAST AND NO MAJOR CHANGES WERE MADE. MONDAY STILL LOOKS TO BE THE MOST ACTIVE DAY AS THE WESTERLIES START TO APPROACH THE AREA AND THE MAIN UPPER TROUGH FINALLY MOVES THROUGH THE AREA. GIVEN GOOD MODEL AGREEMENT AMONG ALL MAJOR OPERATIONAL MODELS AS WELL AS FAVORABLE CONVECTIVE PARAMETERS FROM THE SREF...I RAISED POPS FURTHER ON MONDAY WITH ALMOST THE ENTIRE CWA IN THE 50-60 PERCENT RANGE. MLCAPES AOA 1500 J/KG WITH MIXING RATIOS STILL IN THE 12-14 G/KG BALLPARK. SEE NO REASON AT THIS POINT TO BACK OFF GIVEN FAVORABLE DYNAMICAL SUPPORT. THE FORECAST FROM TUESDAY ONWARD IS ONE OF A GRADUAL DRYING TREND WITH STEADILY DECREASING POPS AND SLOWLY INCREASING TEMPERATURES. A FEW SHOWERS ARE POSSIBLE ON TUESDAY MAINLY NORTH AND EAST OF PHOENIX /THE GFS AND EURO ARE STARTING TO CONVERGE ON A SLIGHTLY SLOWER SOLUTION THAN THEY WERE SHOWING WEDNESDAY/...OTHERWISE POP CHANCES ARE IN THE SINGLE DIGITS OR BARELY 10 PERCENT INTO NEXT WEEKEND. LOW CONFIDENCE TEMPERATURE FORECAST TODAY THROUGH MONDAY...LOOK WHAT HAPPENED ON FRIDAY WITH SOME LOCATIONS ACROSS SE CALIFORNIA TOPPING OUT ABOVE 100 WHILE PHOENIX COULD ONLY GET INTO THE MID 80S /SOME LOCATIONS IN THE EAST VALLEY BARELY GOT OUT OF THE MID 70S ALL DAY/. I STEERED CLEAR OF THE NORMALLY FAVORABLE BIAS CORRECTED GUIDANCE AND TRENDED THE FORECAST TOWARD THE COOLER RAW NAM/SREF VALUES. HIGHS EACH DAY THIS WEEKEND COULD REMAIN IN THE 90S GIVEN ABUNDANT CLOUD COVER...SATURATED GROUND...AND NEARBY SHOWERS. IF STORMS FAIL TO DEVELOP AS PLANNED...LOOK FOR HIGHS CLOSER TO SEASONAL NORMALS JUST ABOVE 100. TEMPS TOWARD THE MIDDLE/END OF NEXT WEEK WILL CLIMB SLIGHTLY...BACK TO NEAR OR SLIGHTLY ABOVE NORMAL. && .AVIATION... SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL... ABUNDANT MOISTURE REMAINS IN PLACE AS ANOTHER WEATHER DISTURBANCE APPROACHES FROM THE SOUTH-SOUTHWEST. YESTERDAYS PRECIP MAY HAVE HAD A STABILIZING EFFECT ON THE PHOENIX AREA AN IT IS UNCLEAR IF THE DISTURBANCE WILL PROVIDE ENOUGH LIFT TO OVERCOME THAT. HOWEVER...GIVEN ALL THE MOISTURE AVAILABLE...IT IS UNLIKELY THAT THERE WONT AT LEAST BE SHWRS/TSTMS IN THE VICINITY OF THE TAF SITES FOR MUCH OF THE DAY...ESPECIALLY AFTER 18Z. ANY STORMS THAT DO FORM WILL BE CAPABLE OF REDUCING VISIBILITY IN HEAVY RAIN. THE STRONGEST STORMS WILL ALSO BE CAPABLE OF SMALL HAIL AND GUSTS AOA 30 KTS. ANTICIPATE STORM THREAT TO TRAIL OFF DURING THE EVENING. OTHERWISE...WINDS TODAY WILL PRIMARILY BE FROM THE EAST AND SOUTHEAST AND BE GUSTY AT TIMES AS SURFACE HIGH PRESSURE STRENGTHENS OVER NEW MEXICO. SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH... ANOTHER WEATHER DISTURBANCE APPROACHING FROM THE SOUTH IS EXPECTED TO MAKE FOR A MORE ACTIVE STORM DAY. EXPECT SHWRS/TSTMS TO BE WITHIN THE VICINITY OF THE TAF SITES AT TIMES...ESPECIALLY AFTER 18Z. ANY STORMS THAT DO FORM WILL BE CAPABLE OF REDUCING VISIBILITY IN HEAVY RAIN. THE STRONGEST STORMS WILL ALSO BE CAPABLE OF SMALL HAIL AND GUSTS AOA 30 KTS. ANTICIPATE STORM THREAT TO TRAIL OFF LATE TONIGHT. OTHERWISE...WINDS TODAY WILL PRIMARILY BE FROM THE SOUTHEAST. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... MONDAY THROUGH FRIDAY... LINGERING MOISTURE WILL MAINTAIN AN ELEVATED CHANCE OF THUNDERSTORMS MONDAY BEFORE BEGINNING TO TREND DOWN TUESDAY AS DRIER AIR FROM THE WEST BEGINS MOVING IN. STORM CHANCES WILL BE LIMITED TO SOUTH-CENTRAL ARIZONA BY WEDNESDAY WITH COMPLETELY DRY CONDITIONS EXPECTED BY FRIDAY. HUMIDITIES WILL FOLLOW THE SAME TREND THOUGH MINIMUM VALUES ARE EXPECTED TO REMAIN ABOVE 15 PERCENT AND OVERNIGHT MAXIMUMS ABOVE 35 PERCENT. APART FROM THUNDERSTORM OUTFLOWS...NO STRONG WINDS ARE ANTICIPATED. AFTERNOON WINDS ARE EXPECTED TO FAVOR SOUTHWEST AND WESTERLY DIRECTIONS FOR MOST AREAS BEGINNING TUESDAY. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...HIRSCH PREVIOUS DISCUSSION...LEINS AVIATION...AJ FIRE WEATHER...AJ
AREA FORECAST DISCUSSION
NWS TUCSON AZ
945 PM MST FRI SEP 7 2012 .SYNOPSIS...ABUNDANT MOISTURE WILL RESULT IN MAINLY AFTERNOON AND EVENING THUNDERSTORMS THROUGH WEDNESDAY. HEAVY RAINFALL WILL OCCUR WITH THE STRONGER THUNDERSTORMS. THEREAFTER...A DRYING TREND IS EXPECTED FOR THE LATTER PART OF NEXT WEEK. && .DISCUSSION...NOT AS ACTIVE OF AN EVENING AS EARLIER THOUGHT. HAD ISOLATED AREAS OF HEAVY RAIN LATE THIS AFTERNOON/EARLY THIS EVENING EAST OF TUCSON. ATMOSPHERE STILL EXTREMELY MOIST FOR SEPTEMBER ALTHOUGH PRECIPITABLE WATER VALUES ARE SLOWLY DECREASING. MADE SOME ADJUSTMENTS TO THE FORECAST EARLIER THIS EVENING WHEN THE FLASH FLOOD WATCH WAS CANCELLED. AT 9 PM...DOPPLER RADAR SHOWED A FEW LIGHT SHOWERS ALONG GILA/GRAHAM COUNTY LINE WITH THE REST OF SE ARIZONA PRECIPITATION FREE. TO OUR EAST...THERE WERE WIDESPREAD SHOWERS AND THUNDERSTORMS MOVING ACROSS SOUTHERN NEW MEXICO IN ADVANCE OF BACK DOOR COLD FRONT. THIS ACTIVITY EXTENDED ACROSS THE INTERNATIONAL BORDER. THIS BACK DOOR COLD FRONT WILL CONTINUE TO SLOWLY PUSH WEST WHILE AT THE MID-LEVELS THERE IS AN UPPER LOW OVER NORTHERN SONORA. BASED ON LATEST HRRR MODEL...WHICH SEEMS TO PICK UP THE ACTIVITY ACROSS SOUTHERN NEW MEXICO/FAR NORTHERN CHIHUAHUA MEXICO NICELY...SHOWERS/ISOLD THUNDERSTORMS WILL PUSH INTO FAR EASTERN ARIZONA AROUND MIDNIGHT AND THEN GRADUALLY PUSH WEST TOWARD TUCSON THROUGH SUNRISE. LOCALIZED HEAVY RAINERS POSSIBLE WITH ANY STORM OVERNIGHT BUT NOT WIDESPREAD ENOUGH TO WARRANT PUTTING OUT ANOTHER FLASH FLOOD WATCH. I WILL MAKE SOME SIGNIFICANT ADJUSTMENTS TO THE OVERNIGHT FORECAST...ESPECIALLY FOR AREAS EAST OF TUCSON. && .AVIATION...SCTD SHRA/ISOLD TS OVERNIGHT EAST OF TUCSON. FROM TUCSON WEST...SLGT CHANCE OF SHRA/TS. SCT -TSRA/-SHRA SATURDAY AFTERNOON. OTHERWISE...VFR CONDITIONS AND SURFACE WIND MOSTLY LESS THAN 10 KTS THRU SATURDAY EVENING OR 09/03Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...SCATTERED THUNDERSTORMS WILL OCCUR THIS WEEKEND INTO EARLY NEXT WEEK FOLLOWED BY A GRADUAL DECREASE IN THUNDERSTORMS THROUGH THE END OF NEXT WEEK. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/TUCSON
AREA FORECAST DISCUSSION...CORRECTED.
NWS TALLAHASSEE FL
922 AM EDT Sat Sep 8 2012 Corrected to add Header. .NEAR TERM [Through Tonight]...Just made some minor tweaks to the fcst today, as what`s left of the Low Pressure Area in the northern Gulf of Mexico is getting picked up by the Upper Trof and will move onshore over the FL Panhandle today. This Low, which will continue on its NE trek through the CWA is expected to bring likely to categorical PoPs to the to the Tri-State area, so blended the previous fcst PoPs with our locally derived CAM PoPs. It should also be noted that PWATs have returned to the 2"+ level both from morning soundings and Satellite estimates (which show them increasing throughout the day from the SW as the Tropical moisture is pulled back to the NE). The 08 UTC HRRR Hi-Res Model appears to have initialized better than the WRF suite, so weighed that in when raising PoPs a bit for this aftn. Did knock down Max Temps and hourly temps 2-3 degrees as well, as the rain and increased cloud cover is making rapid inroads inland already. Over the Coastal Waters, the fcst is on track as Cautionary Conditions are already underway, with winds and seas expected to increase just a bit out of the SW this aftn. && .Previous Discussion... .SHORT TERM [Sunday Through Monday]... The low over the Gulf of Mexico will lift northeastward into the FL Panhandle today before being absorbed by the approaching cold front. The front is forecast to reach our northwestern zones late this afternoon and TLH around midnight before exiting southeast of the area Sunday morning. The front will have slowed down quite a bit by this time and may stall south of the area later on Sunday. All guidance is pointing at a wet day today across the forecast area today and we have maintained a high PoP forecast in the likely to categorical range. Bulk shear is now forecast to be on the order of 20-25 knots just ahead of the front and severe weather is looking less likely. That said, a few strong to severe storms will remain possible. However, the primary threat will be locally heavy rainfall. Rain chances will taper off from northwest to southeast tonight and Sunday, but will not clear entirely out of Dixie County until Monday morning (see table below). This will be the first bonafide cold frontal passage of the fall season. As is typical of these early season frontal passages, max temperatures behind the front will not drop off all that much. However, humidity levels will dip noticeably with dew points dropping into the upper 50s to lower 60s. Similarly, min temps will fall well into the 60s Sunday night, with a few upper 50s possible over Southeast AL and adjacent portions of the FL Panhandle. && .LONG TERM [Monday Night through Friday]... The extended period begins with a trough over wrn states, ridge building E/SE to ern seaboard and trough over extreme wrn Atlc. At surface, 1025mb high over OH/PA with strong ridge builds SWD across Nrn Gulf. This continues NLY winds, drier air and lower humidities advecting with somewhat tighter gradients into the local region. As the high translates to the Mid-Atlantic states thru mid week, winds will gradually veer to the east advecting moisture in from the Atlantic. The surface high will slowly move east off the eastern seaboard by the end of the week with the easterly flow continuing. This will also begin to generate ELY surges at night especially across the marine area. Forecast time height cross sections show most moisture confined below 850mb with subsidence drying above as upper ridging builds over the region thru 12Z Fri then progressively increasing moisture. The week looks like a welcome break from the very wet pattern that we`ve experienced this summer. The next chance for more than isold shwrs will be on Friday and especially on Saturday afternoons when the next upstream trough begins to suppress deep layer ern ridge allowing for a modest increase in moisture. Inverted surface trough also develops to our west. Will go with NIL pops except wdly sct Fri aftn and Low sct Sat aftn. Under NLY flow and near cloudless skies, Min temps commence 3 to 5 degrees below normal rising to near climo by Fri night. Max temps will remain near climo. Avg inland min/max temps are 67 and 88 degrees. && .AVIATION [Beginning 12Z Saturday]... [through 12Z Sunday] Expect low stratus/CIGS to develop near the Gulf coast as moist onshore flow continues, and filling in gradually over S AL/S GA for the next few hours after sunrise. Will go with reductions into MVFR range (with brief IFR at VLD). Should be high coverage today into tonight for SHRA and even -TS in the morning at ECP then late morning to TLH spreading to all Terminals in aftn. Expect MVFR VSBYS/CIGS with -TSRA or VCTS 00z-06z especially VLD and to a lesser extent TLH/ABY. After 06z, MVFR fog developing mainly at VLD and to a lesser extent TLH with IFR likely at VLD near sunrise. && .MARINE... Winds have increased to cautionary levels over the local marine area as low pressure just southeast of the Mississippi Delta lifts northeast toward the Florida Panhandle. This low will reach the Panhandle later today before being absorbed by a cold front. The front will cross the waters from northwest to southeast tonight into Sunday shifting winds to offshore. The front will then stall south of the area early next week as high pressure builds into the Mid Atlantic and Northeast. The gradient between the two systems will increase across the eastern Gulf of Mexico. This will result in a return of cautionary level winds to the forecast area from Tuesday into Wednesday. && .FIRE WEATHER... A cold front will move across the local area thru Sunday spreading ample showers, thunderstorms and gusty winds. In its wake, noticeably drier air will overspread the region from north to south. Minimum RH on Sunday afternoon will drop to the mid 30s across the inland FL Panhandle but should remain above critical levels. Red flag conditions are not expected during the upcoming work week. && .TAE WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...Gould SHORT TERM...Wool LONG TERM...Block AVIATION...Block/Gould MARINE...Block FIRE WEATHER...Block
AREA FORECAST DISCUSSION
NWS MELBOURNE FL
1020 AM EDT SAT SEP 8 2012 .DISCUSSION... LATEST RAP ANALYSIS SHOWS RELATIVELY DRY AIR ADVECTING INTO THE SRN HALF OF THE PENINSULA...H100-H70 AND H85-H50 MEAN RH BTWN 60-70PCT. THIS IS REFLECTED IN THE MORNING SOUNDINGS WITH PWAT VALUES ARND 2.0" AT KJAX/KXMR...DECREASING TO ARND 1.8" AT KTBW/KMFL. H85-H50 LAPSE RATES ARE UNREMARKABLE WITH READINGS ARND 5.5C/KM...UPSTREAM MID LVL VORTICITY VALUES ARE QUITE LOW...AND THE H30-H20 LYR IS WEAKLY DIVERGENT AT BEST. WITH SUCH WEAK DYNAMIC SUPPORT IN PLACE...MESOSCALE BNDRY COLLISIONS WILL BE NECESSARY TO SPARK AFTN SHRAS/TSRAS ACRS THE CWA. HOWEVER... EVEN THESE MAY BE HARD TO COME BY AS THE ATLC RIDGE AXIS OVER THE FL STRAITS WILL REMAIN IN PLACE DUE TO A FRONTAL TROF BUILDING ACRS THE APPALACHIAN. W/SW FLOW BTWN 10-15KTS THRU THE H100-H70 LYR ACRS THE CENTRAL PENINSULA WILL DELAY THE FORMATION OF THE EAST COAST SEA BREEZE UNTIL MID TO LATE AFTN AND MAY SUPPRESS IT ALTOGETHER N OF SEBASTIAN INLET. GIVEN THE DVLPG WX PATTERN...STORM COVERAGE THIS AFTN WILL BE LOWER THAN IN RECENT DAYS. WILL LOWER POPS BY 10PCT ACRS THE BOARD. REMAINDER OF THE FCST LOOKS GOOD. WARM SW FLOW WILL PUSH DAYTIME HIGHS INTO THE L90S OVER MOST OF THE CWA...U80S ALONG THE IMMEDIATE COAST. BEACHGOERS WILL NEED TO BE ALERT FOR A HIGH RIP CURRENT RISK AND ROUGH SURF CONDITIONS GIVEN A BUILDING LONGER PERIOD SWELL OF 12-14 SECONDS MOVING INTO THE LOCAL WATERS. && .AVIATION... THRU 08/17Z...PREVAILING VFR ALL SITES...SLGT CHC IFR TSRAS N OF KISM-KDAB. BTWN 08/17Z-08/20Z...SFC WNDSHFT FM SW TO S/SE AOB 12KTS S OF KVRB ASSOCD WITH THE EAST COAST SEA BREEZE. BTWN 08/17Z-09/01Z...SCT IFR/ISOLD LIFR TSRAS AREAWIDE...MORE NMRS N OF KISM-KTIX AS MID LVL DRY AIR ADVECTION OCCURS OVR THE S HALF OF FL...STORM MOTION E/NE 10-15KTS. AFT 09/01Z...VFR ALL SITES. && .MARINE... NO SIG CHANGES. RIDGE AXIS OVER THE FL STRAITS WILL GENERATE A GENTLE TO MODERATE SWRLY BREEZE ACRS THE LCL ATLC. LONG PD SWELLS FROM DISTANT T.C. LESLIE WILL KEEP SEAS IN THE 3-4FT RANGE NEARSHORE...4-5FT RANGE OFFSHORE. SWELL PDS BTWN 12-14SEC WILL GENERATE HAZARDOUS CONDITIONS AT THE INLETS. && .MLB WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. && $$ SHORT TERM/AVIATION...BRAGAW RADAR/IMPACT WX.......LASCODY
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
950 AM EDT SAT SEP 8 2012 .DISCUSSION... SURFACE HIGH PRESSURE REMAINS ACROSS THE SOUTHERN PENINSULA THIS MORNING WHILE A COLD FRONT IS MOVING INTO THE SOUTHEASTERN STATES. A TIGHTENING PRESSURE GRADIENT BETWEEN THESE TWO FEATURES WILL SUPPORT AN INCREASING SOUTHWEST WIND FLOW ACROSS THE FORECAST AREA THE REMAINDER OF TODAY...WITH BREEZY CONDITIONS DEVELOPING BY EARLY AFTERNOON. AMPLE MOISTURE AND INSTABILITY VIA 12Z RAOB DATA IS ALREADY SUPPORTING SCATTERED SHOWERS AND A FEW STORMS MOVING IN FROM THE GULF EARLY THIS MORNING...AND THIS CONVECTION WILL CONTINUE TO MOVE INLAND THE REMAINDER OF THE MORNING WITH ADDITIONAL SHOWERS AND STORMS FIRING OFF OVER INLAND LOCATIONS DURING THE AFTERNOON...WITH HIGHEST RAIN CHANCES (POPS 30 TO 50 PERCENT RANGE) LIKELY FROM TAMPA TO LAKELAND NORTHWARD THROUGH THE NATURE COAST WHERE THE DEEPEST MOISTURE WILL RESIDE...WITH SLIGHTLY LOWER CHANCES FAR SOUTH. CURRENT FORECAST IS ON TRACK... BUT WILL INCREASE WINDS A BIT IN A MID MORNING UPDATE GIVEN 12Z RAOB DATA AND EXPECTED TRENDS. STORM MOTION TODAY WILL BE FASTER COMPARED TO YESTERDAY...BUT EVEN SO MOISTURE RICH AIR MASS SHOULD STILL ALLOW FOR SOME LOCALLY HEAVY RAINFALL AMOUNTS IN SOME LOCATIONS. MID MORNING UPDATE SHOULD BE OUT BY 10 AM. && .AVIATION... HAVE OPTED TO MAINTAIN VFR AT ALL THE TERMINALS THROUGH THIS EVENING...BUT WITH VCTS/CB AT TPA/PIE EARLY IN THE PERIOD. AN AREA OF LOW PRESSURE MOVING EAST ALONG AN APPROACHING COLD FRONT WILL BRING INCREASING MID/HIGH CLOUDS TONIGHT. TPA/PIE/ LAL/SRQ CAN EXPECT VCSH STARTING IN THE EVENING AND VCTS LATE NIGHT. VARIABLE WINDS BECOME SW TODAY...ROBUST AT TIMES...AND CONTINUE TONIGHT. && .MARINE... A TIGHTENING PRESSURE GRADIENT IS SUPPORTING INCREASING WINDS AND SEAS OVER THE GULF WATERS THIS MORNING WITH WINDS ALREADY IN THE 10 TO 15 KNOT RANGE NEAR SHORE AND 14 TO 18 KNOTS OFFSHORE WITH SEAS UP TO 5 FEET BEING NOTED AT BUOY 42036. CURRENT WINDS WILL INCREASE A BIT MORE THE REMAINDER OF THE DAY AS MIXING TAKES PLACE SO WILL EXPAND EXERCISE CAUTION HEADLINES FOR ALL OF THE NEAR AND OFFSHORE WATERS FROM ENGLEWOOD NORTH TO THE SUWANNEE RIVER OUT 60NM INCLUDING THE TAMPA BAY WATERS IN THE MID MORNING UPDATE. WITH THE INCREASING ONSHORE FLOW THE RISK FOR RIP CURRENTS ALONG AREA BEACHES WILL REMAIN MODERATE THE REMAINDER OF THE DAY SO WILL KEEP THE BEACH HAZARD STATEMENT (CFW) IN PLACE FROM PINELLAS COUNTY SOUTH TO LEE COUNTY THROUGH EARLY TONIGHT. OTHER THAN EXPANDING THE SCEC HEADLINES...NO OTHER CHANGES EXPECTED AT THIS TIME. && .TBW WATCHES/WARNINGS/ADVISORIES... FL...BEACH HAZARDS STATEMENT THROUGH THIS EVENING FOR CHARLOTTE- HILLSBOROUGH-LEE-MANATEE-PINELLAS-SARASOTA. GULF WATERS...NONE. && $$ DISCUSSION/MARINE...57/MCMICHAEL AVIATION...09/RUDE
.NEAR TERM [Through Tonight]...Just made some minor tweaks to the fcst today, as what`s left of the Low Pressure Area in the northern Gulf of Mexico is getting picked up by the Upper Trof and will move onshore over the FL Panhandle today. This Low, which will continue on its NE trek through the CWA is expected to bring likely to categorical PoPs to the to the Tri-State area, so blended the previous fcst PoPs with our locally derived CAM PoPs. It should also be noted that PWATs have returned to the 2"+ level both from morning soundings and Satellite estimates (which show them increasing throughout the day from the SW as the Tropical moisture is pulled back to the NE). The 08 UTC HRRR Hi-Res Model appears to have initialized better than the WRF suite, so weighed that in when raising PoPs a bit for this aftn. Did knock down Max Temps and hourly temps 2-3 degrees as well, as the rain and increased cloud cover is making rapid inroads inland already. Over the Coastal Waters, the fcst is on track as Cautionary Conditions are already underway, with winds and seas expected to increase just a bit out of the SW this aftn. && .Previous Discussion... .SHORT TERM [Sunday Through Monday]... The low over the Gulf of Mexico will lift northeastward into the FL Panhandle today before being absorbed by the approaching cold front. The front is forecast to reach our northwestern zones late this afternoon and TLH around midnight before exiting southeast of the area Sunday morning. The front will have slowed down quite a bit by this time and may stall south of the area later on Sunday. All guidance is pointing at a wet day today across the forecast area today and we have maintained a high PoP forecast in the likely to categorical range. Bulk shear is now forecast to be on the order of 20-25 knots just ahead of the front and severe weather is looking less likely. That said, a few strong to severe storms will remain possible. However, the primary threat will be locally heavy rainfall. Rain chances will taper off from northwest to southeast tonight and Sunday, but will not clear entirely out of Dixie County until Monday morning (see table below). This will be the first bonafide cold frontal passage of the fall season. As is typical of these early season frontal passages, max temperatures behind the front will not drop off all that much. However, humidity levels will dip noticeably with dew points dropping into the upper 50s to lower 60s. Similarly, min temps will fall well into the 60s Sunday night, with a few upper 50s possible over Southeast AL and adjacent portions of the FL Panhandle. && .LONG TERM [Monday Night through Friday]... The extended period begins with a trough over wrn states, ridge building E/SE to ern seaboard and trough over extreme wrn Atlc. At surface, 1025mb high over OH/PA with strong ridge builds SWD across Nrn Gulf. This continues NLY winds, drier air and lower humidities advecting with somewhat tighter gradients into the local region. As the high translates to the Mid-Atlantic states thru mid week, winds will gradually veer to the east advecting moisture in from the Atlantic. The surface high will slowly move east off the eastern seaboard by the end of the week with the easterly flow continuing. This will also begin to generate ELY surges at night especially across the marine area. Forecast time height cross sections show most moisture confined below 850mb with subsidence drying above as upper ridging builds over the region thru 12Z Fri then progressively increasing moisture. The week looks like a welcome break from the very wet pattern that we`ve experienced this summer. The next chance for more than isold shwrs will be on Friday and especially on Saturday afternoons when the next upstream trough begins to suppress deep layer ern ridge allowing for a modest increase in moisture. Inverted surface trough also develops to our west. Will go with NIL pops except wdly sct Fri aftn and Low sct Sat aftn. Under NLY flow and near cloudless skies, Min temps commence 3 to 5 degrees below normal rising to near climo by Fri night. Max temps will remain near climo. Avg inland min/max temps are 67 and 88 degrees. && .AVIATION [Beginning 12Z Saturday]... [through 12Z Sunday] Expect low stratus/CIGS to develop near the Gulf coast as moist onshore flow continues, and filling in gradually over S AL/S GA for the next few hours after sunrise. Will go with reductions into MVFR range (with brief IFR at VLD). Should be high coverage today into tonight for SHRA and even -TS in the morning at ECP then late morning to TLH spreading to all Terminals in aftn. Expect MVFR VSBYS/CIGS with -TSRA or VCTS 00z-06z especially VLD and to a lesser extent TLH/ABY. After 06z, MVFR fog developing mainly at VLD and to a lesser extent TLH with IFR likely at VLD near sunrise. && .MARINE... Winds have increased to cautionary levels over the local marine area as low pressure just southeast of the Mississippi Delta lifts northeast toward the Florida Panhandle. This low will reach the Panhandle later today before being absorbed by a cold front. The front will cross the waters from northwest to southeast tonight into Sunday shifting winds to offshore. The front will then stall south of the area early next week as high pressure builds into the Mid Atlantic and Northeast. The gradient between the two systems will increase across the eastern Gulf of Mexico. This will result in a return of cautionary level winds to the forecast area from Tuesday into Wednesday. && .FIRE WEATHER... A cold front will move across the local area thru Sunday spreading ample showers, thunderstorms and gusty winds. In its wake, noticeably drier air will overspread the region from north to south. Minimum RH on Sunday afternoon will drop to the mid 30s across the inland FL Panhandle but should remain above critical levels. Red flag conditions are not expected during the upcoming work week. && .TAE WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...Gould SHORT TERM...Wool LONG TERM...Block AVIATION...Block/Gould MARINE...Block FIRE WEATHER...Block
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1117 AM MDT SAT SEP 8 2012 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 228 AM MDT SAT SEP 8 2012 03Z WATER VAPOR IMAGERY AND RUC 1.5 PVU SFC INDICATED SHORTWAVE TROUGH MOVING INTO SOUTHERN KANSAS WITH LARGE AREA OF DRYING/SUBSIDENCE OBSERVED OVER THE CWA. AT THE SFC...1024 MB SFC HIGH WAS SETTLING OVER THE AREA WITH TDS IN THE UPPER 30S OBSERVED TO THE NORTHWEST OF CWA. MAIN SHORT TERM FORECAST CONCERNS WILL CENTER AROUND TEMPERATURES AND POTENTIAL FIRE WX IMPACTS AS HIGH AMPLITUDE RIDGE WILL BE DOMINANT WEATHER FEATURE ACROSS THE AREA THROUGH THE REST OF THE WEEKEND. TODAY-SUNDAY...STRONG SUBSIDENCE BEHIND DEPARTING SHORT WAVE TROUGH WILL NOT ONLY CLEAR OUT CLOUDS ACROSS THE AREA BUT LEAVE IN ITS WAKE A STABLE MID LEVEL TEMPERATURE PROFILE TODAY AS HIGH AMPLITUDE RIDGE BEGINS TO BUILD OVER THE REGION. WITH SUCH A STABLE PROFILE...WINDS ALOFT NOT INDICATING ANY SIGNIFICANT MOISTURE ADVECTION AND LITTLE OF ANY LARGE SCALE FORCING FOR ASCENT...THINK CURRENT FORECAST OF DRY CONDITIONS LOOKS REASONABLE AND DO NOT SEE NEED FOR ANY MAJOR ADJUSTMENTS. TEMPERATURES WILL BE SEVERAL DEGREES WARMER TODAY THAN YESTERDAY WITH FULL SUN AND LIGHT WINDS ALLOWING FOR AMPLE SFC HEATING AND EXPECT MOST OF THE CWA TO BE AT OR ABOVE 80 DEGREES. SUNDAY A BIT TRICKIER AS STRONG MODEL AGREEMENT THAT BACKDOOR COLD FRONT WILL MOVE INTO THE AREA DURING THE EARLY MORNING HOURS...FORCED BY SHORT WAVE TROUGH MOVING THROUGH THE NORTHERN PLAINS. STILL EXPECT LOTS OF SUNSHINE/FULL MIXING SO AM HESITANT TO COOL THINGS OFF TO MUCH...BUT THINK BACKING OFF A FEW DEGREES ON HIGH TEMPS IS IN ORDER. AFTERNOON HUMIDITIES WILL FALL INTO THE TEENS TODAY AND AGAIN TOMORROW...INCREASING FIRE WX CONCERNS. WINDS FOR THE MOST PART WILL BE LIGHT AND VARIABLE TODAY...WITH ONLY AREA WHERE A FEW STRONGER GUSTS ARE EXPECTED IS AROUND MCK AS THEY ARE CLOSER TO STRONGER HEIGHT GRADIENT. OVERALL CONDITIONS TOO MARGINAL FOR A FIRE HIGHLIGHT. SUNDAY IS A BIT MORE COMPLICATED AS SFC TROUGH WILL STRENGTHEN THROUGH THE DAY...WIT STRONGEST PRESSURE GRADIENT/SUSTAINED WINDS EXPECTED ACROSS EASTERN COLORADO. MIXED LAYER DEW POINTS COMBINED WITH WEIGHTED MODEL DATA WOULD SUPPORT AFTERNOON HUMIDITIES IN THE 12-15 PERCENT RANGE AS WELL. HOWEVER COLD FRONT IN THE AREA POSSIBLE KEEPING TEMPS COOLER AND LARGE TD SPREADS NOTED ON SREF PLUMES...CONFIDENCE NOT HIGH ENOUGH FOR A FIRE WEATHER WATCH AT THIS POINT. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 228 AM MDT SAT SEP 8 2012 SUNDAY NIGHT-MONDAY NIGHT...HIGH AMPLITUDE RIDGE WILL GRADUALLY SHIFT EAST OVER THE AREA AND WEAKEN SOMEWHAT THROUGH THE PERIOD AS STRONG TROUGH ADVANCES ACROSS THE NORTHWEST CONUS. MAIN IMPACT FOR THE AREA WILL BE WARMING MAX AND MIN TEMPS THROUGH THE PERIOD. WITH LITTLE IN THE WAY OF MOISTURE ADVECTION DO NOT ANTICIPATE ANY MEANINGFUL PRECIP THREAT DESPITE STEEPENING LAPSE RATES AND SFC TROUGH IN AREA. POTENTIAL FOR WIDESPREAD CRITICAL FIRE WX CONDITIONS WILL EXIST ACROSS MUCH OF THE AREA ON MONDAY AS SFC TROUGH SHIFTS TO THE EAST BRINGING GUSTY SOUTHERLY WINDS TO THE AREA. WITH THIS PERIOD BEING IN THE 60-72 HOUR TIME RANGE...CONFIDENCE NOT HIGH ENOUGH FOR A WATCH ISSUANCE BUT WILL HAVE TO MONITOR CLOSELY AS MONDAY APPROACHES. STARTING ON TUESDAY AND THROUGH THE EXTENDED PERIOD THE REGION WILL BE UNDER THE INFLUENCE OF A DEEP SLOW MOVING TROUGH. AT THIS TIME THE FIRST IN A SERIES OF IMPULSES MOVING THROUGH THE FLOW WILL COME ACROSS THE REGION ON TUESDAY ALLOWING FOR A COLD FRONT TO MOVE INTO THE CWA TUESDAY NIGHT INTO WEDNESDAY. BETWEEN THE FORCING ASSOC WITH THE IMPULSE AND FRONT...COUPLED WITH LIMITED INSTABILITY...SHOULD SET THE STAGE FOR TSRA/SHRA LATE TUE AFTERNOON/NIGHT AND INTO WEDNESDAY BEHIND THE FRONT. PRECIP CHANCES REMAIN THEREAFTER BUT MORE LIMITED IN COVERAGE AS ANOTHER IMPULSE MOVES ACROSS ON THURSDAY BUT LACKING THE INSTABILITY AND FORCING COMPARED TO TUESDAY NIGHT/WEDNESDAY. THE PARENT TROUGH AXIS IS PROGGED BY THE 00Z GFS AND EC TO MOVE EAST OF THE CWA ON FRIDAY WITH RISING HEIGHTS OVER THE CNTRL HIGH PLAINS WHICH SHOULD CUT OFF PRECIP OPPORTUNITIES AT THAT POINT. HIGH TEMPERATURES ON TUESDAY WILL BE SLIGHTLY ABOVE NORMAL AHEAD OF THE COLD FRONT BUT THEN DROP BELOW NORMAL THROUGH THE REST OF THE PERIOD. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 1111 AM MDT SAT SEP 8 2012 VFR CONDITIONS FORECAST FOR THE 18Z TAFS. NORTHWEST WINDS AROUND 10 MPH WILL BE COMMON THROUGH THE AFTERNOON AS A SURFACE HIGH PRESSURE OVER THE CENTRAL PLAINS MOVES SOUTH. OVERNIGHT WINDS WILL BE LIGHT AS A COLD FRONT AND SURFACE HIGH PRESSURE MOVE INTO THE AREA. THE LIGHT WINDS WILL CONTINUE SUNDAY AS THE COLD FRONT AND SURFACE HIGH DRIFT EAST. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JRM LONG TERM...05/JRM AVIATION...JTL
AREA FORECAST DISCUSSION
NWS GOODLAND KS
538 AM MDT SAT SEP 8 2012 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 228 AM MDT SAT SEP 8 2012 03Z WATER VAPOR IMAGERY AND RUC 1.5 PVU SFC INDICATED SHORTWAVE TROUGH MOVING INTO SOUTHERN KANSAS WITH LARGE AREA OF DRYING/SUBSIDENCE OBSERVED OVER THE CWA. AT THE SFC...1024 MB SFC HIGH WAS SETTLING OVER THE AREA WITH TDS IN THE UPPER 30S OBSERVED TO THE NORTHWEST OF CWA. MAIN SHORT TERM FORECAST CONCERNS WILL CENTER AROUND TEMPERATURES AND POTENTIAL FIRE WX IMPACTS AS HIGH AMPLITUDE RIDGE WILL BE DOMINANT WEATHER FEATURE ACROSS THE AREA THROUGH THE REST OF THE WEEKEND. TODAY-SUNDAY...STRONG SUBSIDENCE BEHIND DEPARTING SHORT WAVE TROUGH WILL NOT ONLY CLEAR OUT CLOUDS ACROSS THE AREA BUT LEAVE IN ITS WAKE A STABLE MID LEVEL TEMPERATURE PROFILE TODAY AS HIGH AMPLITUDE RIDGE BEGINS TO BUILD OVER THE REGION. WITH SUCH A STABLE PROFILE...WINDS ALOFT NOT INDICATING ANY SIGNIFICANT MOISTURE ADVECTION AND LITTLE OF ANY LARGE SCALE FORCING FOR ASCENT...THINK CURRENT FORECAST OF DRY CONDITIONS LOOKS REASONABLE AND DO NOT SEE NEED FOR ANY MAJOR ADJUSTMENTS. TEMPERATURES WILL BE SEVERAL DEGREES WARMER TODAY THAN YESTERDAY WITH FULL SUN AND LIGHT WINDS ALLOWING FOR AMPLE SFC HEATING AND EXPECT MOST OF THE CWA TO BE AT OR ABOVE 80 DEGREES. SUNDAY A BIT TRICKIER AS STRONG MODEL AGREEMENT THAT BACKDOOR COLD FRONT WILL MOVE INTO THE AREA DURING THE EARLY MORNING HOURS...FORCED BY SHORT WAVE TROUGH MOVING THROUGH THE NORTHERN PLAINS. STILL EXPECT LOTS OF SUNSHINE/FULL MIXING SO AM HESITANT TO COOL THINGS OFF TO MUCH...BUT THINK BACKING OFF A FEW DEGREES ON HIGH TEMPS IS IN ORDER. AFTERNOON HUMIDITIES WILL FALL INTO THE TEENS TODAY AND AGAIN TOMORROW...INCREASING FIRE WX CONCERNS. WINDS FOR THE MOST PART WILL BE LIGHT AND VARIABLE TODAY...WITH ONLY AREA WHERE A FEW STRONGER GUSTS ARE EXPECTED IS AROUND MCK AS THEY ARE CLOSER TO STRONGER HEIGHT GRADIENT. OVERALL CONDITIONS TOO MARGINAL FOR A FIRE HIGHLIGHT. SUNDAY IS A BIT MORE COMPLICATED AS SFC TROUGH WILL STRENGTHEN THROUGH THE DAY...WIT STRONGEST PRESSURE GRADIENT/SUSTAINED WINDS EXPECTED ACROSS EASTERN COLORADO. MIXED LAYER DEWPOINTS COMBINED WITH WEIGHTED MODEL DATA WOULD SUPPORT AFTERNOON HUMIDITIES IN THE 12-15 PERCENT RANGE AS WELL. HOWEVER COLD FRONT IN THE AREA POSSIBLE KEEPING TEMPS COOLER AND LARGE TD SPREADS NOTED ON SREF PLUMES...CONFIDENCE NOT HIGH ENOUGH FOR A FIRE WEATHER WATCH AT THIS POINT. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 228 AM MDT SAT SEP 8 2012 SUNDAY NIGHT-MONDAY NIGHT...HIGH AMPLITUDE RIDGE WILL GRADUALLY SHIFT EAST OVER THE AREA AND WEAKEN SOMEWHAT THROUGH THE PERIOD AS STRONG TROUGH ADVANCES ACROSS THE NORTHWEST CONUS. MAIN IMPACT FOR THE AREA WILL BE WARMING MAX AND MIN TEMPS THROUGH THE PERIOD. WITH LITTLE IN THE WAY OF MOISTURE ADVECTION DO NOT ANTICIPATE ANY MEANINGFUL PRECIP THREAT DESPITE STEEPENING LAPSE RATES AND SFC TROUGH IN AREA. POTENTIAL FOR WIDESPREAD CRITICAL FIRE WX CONDITIONS WILL EXIST ACROSS MUCH OF THE AREA ON MONDAY AS SFC TROUGH SHIFTS TO THE EAST BRINGING GUSTY SOUTHERLY WINDS TO THE AREA. WITH THIS PERIOD BEING IN THE 60-72 HOUR TIME RANGE...CONFIDENCE NOT HIGH ENOUGH FOR A WATCH ISSUANCE BUT WILL HAVE TO MONITOR CLOSELY AS MONDAY APPROACHES. STARTING ON TUESDAY AND THROUGH THE EXTENDED PERIOD THE REGION WILL BE UNDER THE INFLUENCE OF A DEEP SLOW MOVING TROUGH. AT THIS TIME THE FIRST IN A SERIES OF IMPULSES MOVING THROUGH THE FLOW WILL COME ACROSS THE REGION ON TUESDAY ALLOWING FOR A COLD FRONT TO MOVE INTO THE CWA TUESDAY NIGHT INTO WEDNESDAY. BETWEEN THE FORCING ASSOC WITH THE IMPULSE AND FRONT...COUPLED WITH LIMITED INSTABILITY...SHOULD SET THE STAGE FOR TSRA/SHRA LATE TUE AFTERNOON/NIGHT AND INTO WEDNESDAY BEHIND THE FRONT. PRECIP CHANCES REMAIN THEREAFTER BUT MORE LIMITED IN COVERAGE AS ANOTHER IMPULSE MOVES ACROSS ON THURSDAY BUT LACKING THE INSTABILITY AND FORCING COMPARED TO TUESDAY NIGHT/WEDNESDAY. THE PARENT TROUGH AXIS IS PROGGED BY THE 00Z GFS AND EC TO MOVE EAST OF THE CWA ON FRIDAY WITH RISING HEIGHTS OVER THE CNTRL HIGH PLAINS WHICH SHOULD CUT OFF PRECIP OPPORTUNITIES AT THAT POINT. HIGH TEMPERATURES ON TUESDAY WILL BE SLIGHTLY ABOVE NORMAL AHEAD OF THE COLD FRONT BUT THEN DROP BELOW NORMAL THROUGH THE REST OF THE PERIOD. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING) ISSUED AT 537 AM MDT SAT SEP 8 2012 VFR CONDITIONS EXPECTED FOR THE NEXT 24 HOURS AS SFC RIDGE BRING LIGHT WEST NORTHWESTERLY WINDS AND CLEAR SKIES PREVAIL. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JRM LONG TERM...05/JRM AVIATION...JRM
AREA FORECAST DISCUSSION
NWS GOODLAND KS
229 AM MDT SAT SEP 8 2012 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 228 AM MDT SAT SEP 8 2012 03Z WATER VAPOR IMAGERY AND RUC 1.5 PVU SFC INDICATED SHORTWAVE TROUGH MOVING INTO SOUTHERN KANSAS WITH LARGE AREA OF DRYING/SUBSIDENCE OBSERVED OVER THE CWA. AT THE SFC...1024 MB SFC HIGH WAS SETTLING OVER THE AREA WITH TDS IN THE UPPER 30S OBSERVED TO THE NORTHWEST OF CWA. MAIN SHORT TERM FORECAST CONCERNS WILL CENTER AROUND TEMPERATURES AND POTENTIAL FIRE WX IMPACTS AS HIGH AMPLITUDE RIDGE WILL BE DOMINANT WEATHER FEATURE ACROSS THE AREA THROUGH THE REST OF THE WEEKEND. TODAY-SUNDAY...STRONG SUBSIDENCE BEHIND DEPARTING SHORT WAVE TROUGH WILL NOT ONLY CLEAR OUT CLOUDS ACROSS THE AREA BUT LEAVE IN ITS WAKE A STABLE MID LEVEL TEMPERATURE PROFILE TODAY AS HIGH AMPLITUDE RIDGE BEGINS TO BUILD OVER THE REGION. WITH SUCH A STABLE PROFILE...WINDS ALOFT NOT INDICATING ANY SIGNIFICANT MOISTURE ADVECTION AND LITTLE OF ANY LARGE SCALE FORCING FOR ASCENT...THINK CURRENT FORECAST OF DRY CONDITIONS LOOKS REASONABLE AND DO NOT SEE NEED FOR ANY MAJOR ADJUSTMENTS. TEMPERATURES WILL BE SEVERAL DEGREES WARMER TODAY THAN YESTERDAY WITH FULL SUN AND LIGHT WINDS ALLOWING FOR AMPLE SFC HEATING AND EXPECT MOST OF THE CWA TO BE AT OR ABOVE 80 DEGREES. SUNDAY A BIT TRICKIER AS STRONG MODEL AGREEMENT THAT BACKDOOR COLD FRONT WILL MOVE INTO THE AREA DURING THE EARLY MORNING HOURS...FORCED BY SHORT WAVE TROUGH MOVING THROUGH THE NORTHERN PLAINS. STILL EXPECT LOTS OF SUNSHINE/FULL MIXING SO AM HESITANT TO COOL THINGS OFF TO MUCH...BUT THINK BACKING OFF A FEW DEGREES ON HIGH TEMPS IS IN ORDER. AFTERNOON HUMIDITIES WILL FALL INTO THE TEENS TODAY AND AGAIN TOMORROW...INCREASING FIRE WX CONCERNS. WINDS FOR THE MOST PART WILL BE LIGHT AND VARIABLE TODAY...WITH ONLY AREA WHERE A FEW STRONGER GUSTS ARE EXPECTED IS AROUND MCK AS THEY ARE CLOSER TO STRONGER HEIGHT GRADIENT. OVERALL CONDITIONS TOO MARGINAL FOR A FIRE HIGHLIGHT. SUNDAY IS A BIT MORE COMPLICATED AS SFC TROUGH WILL STRENGTHEN THROUGH THE DAY...WIT STRONGEST PRESSURE GRADIENT/SUSTAINED WINDS EXPECTED ACROSS EASTERN COLORADO. MIXED LAYER DEWPOINTS COMBINED WITH WEIGHTED MODEL DATA WOULD SUPPORT AFTERNOON HUMIDITIES IN THE 12-15 PERCENT RANGE AS WELL. HOWEVER COLD FRONT IN THE AREA POSSIBLE KEEPING TEMPS COOLER AND LARGE TD SPREADS NOTED ON SREF PLUMES...CONFIDENCE NOT HIGH ENOUGH FOR A FIRE WEATHER WATCH AT THIS POINT. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 228 AM MDT SAT SEP 8 2012 SUNDAY NIGHT-MONDAY NIGHT...HIGH AMPLITUDE RIDGE WILL GRADUALLY SHIFT EAST OVER THE AREA AND WEAKEN SOMEWHAT THROUGH THE PERIOD AS STRONG TROUGH ADVANCES ACROSS THE NORTHWEST CONUS. MAIN IMPACT FOR THE AREA WILL BE WARMING MAX AND MIN TEMPS THROUGH THE PERIOD. WITH LITTLE IN THE WAY OF MOISTURE ADVECTION DO NOT ANTICIPATE ANY MEANINGFUL PRECIP THREAT DESPITE STEEPENING LAPSE RATES AND SFC TROUGH IN AREA. POTENTIAL FOR WIDESPREAD CRITICAL FIRE WX CONDITIONS WILL EXIST ACROSS MUCH OF THE AREA ON MONDAY AS SFC TROUGH SHIFTS TO THE EAST BRINGING GUSTY SOUTHERLY WINDS TO THE AREA. WITH THIS PERIOD BEING IN THE 60-72 HOUR TIME RANGE...CONFIDENCE NOT HIGH ENOUGH FOR A WATCH ISSUANCE BUT WILL HAVE TO MONITOR CLOSELY AS MONDAY APPROACHES. STARTING ON TUESDAY AND THROUGH THE EXTENDED PERIOD THE REGION WILL BE UNDER THE INFLUENCE OF A DEEP SLOW MOVING TROUGH. AT THIS TIME THE FIRST IN A SERIES OF IMPULSES MOVING THROUGH THE FLOW WILL COME ACROSS THE REGION ON TUESDAY ALLOWING FOR A COLD FRONT TO MOVE INTO THE CWA TUESDAY NIGHT INTO WEDNESDAY. BETWEEN THE FORCING ASSOC WITH THE IMPULSE AND FRONT...COUPLED WITH LIMITED INSTABILITY...SHOULD SET THE STAGE FOR TSRA/SHRA LATE TUE AFTERNOON/NIGHT AND INTO WEDNESDAY BEHIND THE FRONT. PRECIP CHANCES REMAIN THEREAFTER BUT MORE LIMITED IN COVERAGE AS ANOTHER IMPULSE MOVES ACROSS ON THURSDAY BUT LACKING THE INSTABILITY AND FORCING COMPARED TO TUESDAY NIGHT/WEDNESDAY. THE PARENT TROUGH AXIS IS PROGGED BY THE 00Z GFS AND EC TO MOVE EAST OF THE CWA ON FRIDAY WITH RISING HEIGHTS OVER THE CNTRL HIGH PLAINS WHICH SHOULD CUT OFF PRECIP OPPORTUNITIES AT THAT POINT. HIGH TEMPERATURES ON TUESDAY WILL BE SLIGHTLY ABOVE NORMAL AHEAD OF THE COLD FRONT BUT THEN DROP BELOW NORMAL THROUGH THE REST OF THE PERIOD. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED AT 1100 PM MDT FRI SEP 7 2012 VFR THROUGH THE PERIOD AT KGLD AND KMCK. SFC HIGH TO MOVE OVER THE TERMINALS THROUGH THE PERIOD. MAY SEE SOME FAIR WX CU AT KGLD AROUND 18Z WITH NORTHWEST WINDS NEAR 10 KTS. BY 00Z ANY CLOUDS SHOULD DISSIPATE WITH THE LOSS OF DAYTIME HEATING AND WINDS WILL BECOME VRB05KTS. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JRM LONG TERM...05/JRM AVIATION...007
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1101 PM MDT FRI SEP 7 2012 .SHORT TERM...(THIS AFTERNOON THROUGH TONIGHT) ISSUED AT 210 PM MDT FRI SEP 7 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS SHOW POSITIVELY TILTED TROUGH OVER NORTHERN GREAT LAKES WITH AXIS EXTENDING SOUTHWEST ACROSS CENTRAL NEBRASKA. LARGE SCALE SUBSIDE IS CURRENTLY BUILDING INTO TRI-STATE AREA AS THIS TROUGH SHIFTS EAST. AT THE SURFACE HIGH PRESSURE BUILDING INTO THE CWA FROM THE NORTHWEST. ISOLATED LIGHT SHOWERS/SPRINKLES WILL REMAIN POSSIBLE ACROSS THE NW THIS AFTERNOON ASSOCIATED WITH COLD POOL ALOFT AND STEEPENING LAPSE RATES. WE ALSO HAVE SOME WEAK H85-H7 FRONTOGENESIS LINGERING JUST TO THE NORTHWEST OF THE CWA...RESPONSIBLE FOR CURRENT SHOWER ACTIVITY OUTSIDE OF CWA. DO NOT ANTICIPATE ANY PRECIP LINGERING PAST SUNSET WHEN DIURNAL HEATING COMES TO AN END. COOLER AIR MASS ALREADY IN PLACE AFTER FRONTAL PASSAGE LAST NIGHT...WITH H85 TEMPS BASED ON THIS MORNINGS 12Z SOUNDING IN THE 12-14C RANGE. WITH CALM WINDS AND CLEARING SKIES I EXPECT OVERNIGHT TEMPS TO DROP TO THE LOW TO MID 40S ACROSS THE AREA. IF WE WERE TO SEE LOWER TD VALUES ADVECT INTO THE CWA...THEN WE COULD BREAK A FEW LOW TEMPERATURE RECORDS TONIGHT...WITH VALUES IN THE UPPER 30S. PREVIOUS GUIDANCE WAS BRINGING MUCH LOWER TD VALUES INTO THE AREA TONIGHT. HOWEVER...BASED ON UPSTREAM TRENDS AND CURRENT GUIDANCE TD VALUES SHOULD REMAIN 40F OR HIGHER...WHICH WILL LIMIT COOLING POTENTIAL. .LONG TERM...(SATURDAY THROUGH FRIDAY) ISSUED AT 226 PM MDT FRI SEP 7 2012 SATURDAY THROUGH SUNDAY NIGHT WILL REMAIN DRY AS THE UPPER LEVEL RIDGE CURRENTLY OVER THE SOUTHERN CONUS BUILDS NORTHWARD OVER THE GREAT BASIN AND EXPANDS EAST INTO THE PLAINS. SUNDAY AFTERNOON AND SUNDAY NIGHT THE RIDGE WILL FLATTEN OUT AS A SHORT WAVE TROUGH MOVES ACROSS IT. THE SHORT WAVE TROUGH WILL MOVE INTO THE AREA SUNDAY NIGHT. HOWEVER AM ONLY EXPECTING SOME CLOUDS TO DEVELOP WITH THE TROUGH DUE TO THE SHALLOW MOIST LAYER TO WORK WITH BETWEEN 500-600MB. TUESDAY THROUGH FRIDAY WILL HAVE CHANCES FOR PRECIPITATION ALMOST EVERY DAY. TUESDAY AN UPPER LEVEL SHORT WAVE TROUGH AND ASSOCIATED SURFACE TROUGH MOVE ACROSS THE AREA PROVIDING AN OPPORTUNITY FOR SOME LOCATIONS TO RECEIVE RAINFALL. TUESDAY NIGHT INTO WEDNESDAY ANOTHER UPPER LEVEL SHORT WAVE TROUGH FOLLOWS A COLD FRONT THROUGH THE AREA...OFFERING A SHOT FOR MORE WIDE SPREAD RAINFALL. THE NEXT BEST CHANCE FOR WIDE SPREAD RAINFALL COMES WEDNESDAY NIGHT THROUGH THURSDAY NIGHT AS AN UPPER LEVEL LONG WAVE TROUGH MOVES ACROSS THE PLAINS. THERE MAY BE SOME LINGERING STORM ACTIVITY ON FRIDAY AS THE TROUGH DEPARTS THE AREA. HIGH TEMPERATURES WILL BE WARMEST ON MONDAY AND TUESDAY AHEAD OF THE COLD FRONT...ROUGHLY 10 DEGREES ABOVE NORMAL. FROM WEDNESDAY THROUGH FRIDAY HIGH TEMPERATURES WILL BE ALMOST 10 DEGREES BELOW NORMAL. LOW TEMPERATURES FOR THE PERIOD WILL BE NEAR NORMAL. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED AT 1100 PM MDT FRI SEP 7 2012 VFR THROUGH THE PERIOD AT KGLD AND KMCK. SFC HIGH TO MOVE OVER THE TERMINALS THROUGH THE PERIOD. MAY SEE SOME FAIR WX CU AT KGLD AROUND 18Z WITH NORTHWEST WINDS NEAR 10 KTS. BY 00Z ANY CLOUDS SHOULD DISSIPATE WITH THE LOSS OF DAYTIME HEATING AND WINDS WILL BECOME VRB05KTS. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...DR LONG TERM...JTL AVIATION...99
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
400 AM EDT SAT SEP 8 2012 .SYNOPSIS... A COLD FRONT WILL APPROACH THE MID ATLANTIC FROM THE NORTHWEST THIS MORNING AND CROSS THE AREA THIS AFTERNOON AND EVENING. STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED IN ADVANCE OF THIS FRONT. COOLER AND MUCH DRIER AIR WILL MOVE IN SUNDAY AND REMAIN OVER THE REGION THROUGH AT LEAST MID WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... REST OF THE OVERNIGHT...WAVE OF LOW CLOUDS HAVE SPREAD NORTH ACROSS THE NRN VA I-95 CORRIDOR AND MD PIEDMONT AND EAST. THESE CLOUDS WILL PERSIST THROUGH SUNRISE BEFORE MIXING OUT IN ADVANCE OF THE COLD FRONT. SCATTERED THUNDERSTORMS ARE EXPECTED TO CONTINUE DEVELOPING OVER THE BAY OFF SRN MD THROUGH DAYBREAK. RAP GUIDANCE DISPLAYED ON THE SPC MESOANALYSIS PAGE DOES INDICATE 2000 J/KG OVER SRN MD PORTIONS OF THE BAY...SO ACTIVITY MAY BE VIGOROUS DESPITE THE EARLY MORNING HOUR. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM SUNDAY/... TODAY...07Z REGIONAL RADAR MOSAIC DEPICTS GRADUAL WEAKENING OF PRECIP SHIELD IN ADVANCE OF A COLD FRONT STRETCHING FROM THE ERN GREAT LAKES THROUGH THE MID SOUTH STATES. THIS PREFRONTAL ACTIVITY WILL APPROACH FROM THE WEST THROUGH MID MORNING. 04Z HRRR PROPERLY DEPICTS CURRENT ACTIVITY AND TREND...WITH LEADING PRECIP REACHING THE ALLEGHENY FRONT AROUND 14Z...WITH MORE OF A SCATTERED LINE OF PRECIP DEVELOPING OVER THE POTOMAC HIGHLANDS LATE IN THE MORNING. POPS WERE UPDATED WITH A HEAVY LEANING TOWARD SREF. POPS THEN DECREASED FOR THE PIEDMONT AND WEST DUE TO LOCAL WRF ARW RUNS AND 00Z SPC 4KM NMM RUN DEPICTING A BIT OF A DC SPLIT THAT COAGULATES JUST EAST OF DC /AS IS OFTEN SEEN...PARTICULARLY WITH LATE AFTERNOON AND EVENING TIMING/. TALL SKINNY CAPE OF ONLY UP TO 2000 J/KG /AN 18Z RAOB WAS REQUESTED BY SPC/. BULK SHEAR IN EXCESS OF 30 KT COULD ALLOW SOME DISCRETE SUPERCELL DEVELOPMENT. DAMAGING WINDS MAIN THREAT. AN ISOLATED TORNADO CANNOT BE RULED OUT...THOUGH BEST SHEAR/CAPE CONVERGENCE FOR THOSE ARE FARTHER NORTH. MOTION SHOULD BE QUICK ENOUGH TO LIMIT FLASH FLOODING THREAT DESPITE HEAVY RAIN. MAX TEMPS MID 80S EAST OF THE BLUE RIDGE /UPR 70S TO LOW 80S WEST DEPENDING ON PRECIP AND CLOUDS/. TONIGHT...TRAILING STRATIFORM EXPECTED TO MOVE EAST THROUGH THE EVENING...WITH DRY/COOL AIR COMING IN FROM THE NW. NWLY FLOW AROUND 10 MPH WILL LIMIT FOG. MIN TEMPS IN THE 40S IN THE POTOMAC HIGHLANDS...50S ELSEWHERE /LOW 60S NEAR SHORE AND URBAN AREAS/ WITH SKIES CLEARING. && .LONG TERM /SUNDAY THROUGH FRIDAY/... COLD FRONT WILL BE OFFSHORE BY SUNDAY WITH COOLER AND DRIER HIGH PRESSURE MOVING IN. TEMPS SHOULD STAY NEAR OR A LITTLE BELOW NORMAL THROUGH AT LEAST MIDWEEK BEFORE TEMPS RISE A LITTLE AS THE HIGH SHIFTS OFFSHORE AND WINDS SWAP TO A SOUTHERLY DIRECTION. THE NEXT SIGNIFICANT WEATHER FEATURE IS A WEAK COLD FRONT APPROACHING BY THE END OF NEXT WEEK. NO EXPECTED TROPICAL THREATS TO OUR FORECAST AREA THROUGH NEXT WEEK. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... IFR/MVFR DECK MOVING NW ACROSS BALT-WASH METRO EARLY THIS MORNING...ISOLATED SHOWERS/THUNDERSTORMS EXPECTED WELL SOUTHEAST OF DC THROUGH MID MORNING. SOUTHERLY FLOW WILL CONTINUE TO HOLD OFF IFR MIST/FOG DEVELOPMENT. SLY FLOW INCREASES THIS MORNING IN ADVANCE OF THE APPROACHING COLD FRONT. LINE/S/ OF THUNDERSTORMS EXPECTED IN ADVANCE OF THE FRONT ACROSS THE TERMINALS FROM WEST TO EAST THIS AFTERNOON INTO THE EVENING. SOME STORMS MAY BE STRONG/SEVERE...WITH DAMAGING WIND GUSTS. PCPN ENDS AND CLOUDS GRADUALLY CLR TONIGHT WITH DRY NWLY FLOW AROUND 10 KT LIMITING FOG DEVELOPMENT. VFR CONDS EXPECTED THRU NEXT WK. NW WINDS 10-20 KTS SUN/MON... DIMINISHING THEREAFTER AS HIGH PRESSURE MOVES IN. && .MARINE... LULL IN SLY SCA THROUGH SUNRISE...THEN SCA LEVELS RETURN IN GUSTY SLY FLOW AHEAD OF A COLD FRONT. LINE/S/ OF TSTMS EXPECTED LATE AFTERNOON INTO EVENING ACROSS THE WATERS IN ADVANCE OF THE COLD FRONT. SPECIAL MARINE WARNINGS EXPECTED SINCE MAIN THREAT WITH THE WEATHER IS DAMAGING WINDS. NWLY FLOW AFTER THE FRONT CONTINUES SCA FOR MAIN PORTIONS OF THE WATERS TONIGHT WITH GUSTS AROUND 20 KT. GUSTY NW WINDS SUNDAY ARE EXPECTED TO REMAIN AROUND 20KTS FOR MUCH OF THE BAY CHANNEL SOUTH OF BALTIMORE AND LOWER POTOMAC DURING THE MORNING...REQUIRING A SMALL CRAFT ADVISORY THERE SUNDAY MORNING. OTHERWISE NO MARINE HAZARDS THROUGH NEXT WEEK. && .TIDES/COASTAL FLOODING... TIDAL ANOMALIES EXPECTED TO REMAIN ABOUT THREE QUARTERS FOOT ABOVE ASTRONOMICAL PREDICTION INTO SATURDAY EVENING WITH SLY FLOW IN ADVANCE OF A COLD FRONT. POST FRONT WILL BE NWLY FLOW AND MORE NORMAL WATER LEVELS. WITH THE PREFERRED TIDE TONIGHT HAVING PAST...NO COASTAL FLOODING IS EXPECTED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ531-539>541. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 6 AM EDT SUNDAY FOR ANZ530-538-542. SMALL CRAFT ADVISORY UNTIL 3 PM EDT SUNDAY FOR ANZ532>534-537- 543. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 6 PM EDT THIS EVENING FOR ANZ535-536. && $$ SYNOPSIS...BAJ/CAS NEAR TERM...BAJ SHORT TERM...BAJ LONG TERM...CAS AVIATION...BAJ/CAS MARINE...BAJ/CAS TIDES/COASTAL FLOODING...BAJ
AREA FORECAST DISCUSSION...UPDATED
NWS BALTIMORE MD/WASHINGTON DC
252 AM EDT SAT SEP 8 2012 .SYNOPSIS... A COLD FRONT WILL APPROACH THE MID ATLANTIC REGION TODAY...AND CROSS THIS AFTERNOON AND EVENING. STRONG THUNDERSTORMS ARE EXPECTED AHEAD OF THIS FRONT. HIGH PRESSURE WILL BUILD BEHIND THE COLD FRONT LATE TONIGHT THROUGH EARLY NEXT WEEK AND THEN DOMINATE THROUGH THE REMAINDER OF THE WORK WEEK WITH DRY AND SEASONABLE TEMPERATURES. && .NEAR TERM /REST OF THE OVERNIGHT/... WAVE OF LOW CLOUDS HAVE SPREAD NORTHWEST ACROSS THE I-95 CORRIDOR AND EAST OVER THE PAST COUPLE HOURS. MAIN EFFECT FOR THE PUBLIC IS WARMER CONDITIONS...WITH TEMPS PERSISTING IN THE LOW 70S WHERE CLOUDS PERSIST. ISOLATED SHOWERS ARE EXPECTED TO DEVELOP SOUTHEAST OF DC OVER THE NEXT COUPLE HOURS...PERHAPS SOME THUNDER BY DAYBREAK OVER THE MD PORTION OF THE BAY. RAP GUIDANCE DISPLAYED ON THE SPC MESOANALYSIS PAGE DOES INDICATE 2000 J/KG OVER SRN MD PORTIONS OF THE BAY...SO ACTIVITY MAY BE VIGOROUS DESPITE THE EARLY MORNING HOUR. OTHERWISE...PREFRONTAL ACTIVITY WILL APPROACH FROM THE WEST THROUGH SUNRISE. 03Z HRRR DEPICTS LEADING PRECIP REACHING THE ALLEGHENY FRONT BY 13Z...WITH MORE OF A SCATTERED LINE OF PRECIP DEVELOPING LATE IN THE MORNING. POPS WERE UPDATED WITH A HEAVY LEANING TOWARD SREF /WITH POPS DECREASED A BIT/. EXPECT HEAVY THUNDERSTORMS WITH DAMAGING WINDS AS THE MAIN THREAT AS WRITTEN IN THE HWOLWX. WILL CONTINUE TO MONITOR LATEST GUIDANCE AND UPDATE GRIDS AS NECESSARY. && .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/... CONFIDENCE IN SEVERE WEATHER INCREASING FOR THE DAYTIME HOURS SATURDAY. DEEP UPPER TROUGH OVER THE WESTERN OHIO RIVER VALLEY WILL PIVOT TOWARDS THE REGION...WHILE A STRONG SURFACE COLD FRONT APPROACHES FROM THE WEST IN THE MORNING AND CROSS THE CWA DURING THE DAY. STRONG UPPER LEVEL JET WILL SUPPORT A FAVORABLE SHEAR ENVIRONMENT. THERE ARE SOME QUESTIONS ABOUT AVAILABLE INSTABILITY DEPENDING ON CLOUD COVER...BUT THIS IS EXPECTED TO BE MORE THAN COMPENSATED FOR BY STRONG FORCING FROM THE FRONT. SPC HAS PLACED A FEW COUNTIES IN NORTHEASTERN MARYLAND IN A MODERATE RISK...WHILE THE REST OF THE CWA REMAINS IN A SLIGHT RISK. WITH STRONG WIND FIELDS IN PLACE...MAIN THREAT WILL BE DAMAGING WINDS...WITH POTENTIAL FOR SQUALL LINE DEVELOPMENT. THERE IS ALSO SOME TORNADO RISK...AS 12Z MODEL FORECAST SOUNDINGS INDICATE HELICITY COULD EXCEED 200 M2/S2 BEFORE FRONTAL PASSAGE. HIGH TEMPS RANGE FROM THE UPPER 70S OVER THE POTOMAC HIGHLANDS TO THE UPPER 80S OVER EASTERN PORTIONS OF THE CWA. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... CDFNT SHUD BE CLEARING BAY BY 0Z...WITH PCPN RAPIDLY ENDING BEHIND IT. SKIES SHUD CLR AFTER MIDNIGHT...THO UPSLOPE CLOUDS/SCT SHWRS CUD PERSIST W OF ALLEGHENY FRONT IN NW FLOW. ULVL TROF WILL LAG A BIT BEHIND FRONT AND ITS AXIS WILL NOT CROSS CWA UNTIL SUN EVE. LLVLS WILL BE SCOURED OF ANY MOISTURE...BUT WITH STRONG CAA...ESPECIALLY ALOFT...DIURNALLY STEEP LAPSE RATES AND ARRIVAL OF ULVL VORT MAX SUN AFTN CUD INDUCE CU FIELD AND PERHAPS ISOLATED SHWRS. FOR NW...KEPT FCST DRY XCPT FOR UPSLOPE-FAVORED AREAS. AFTER ULVL TROF MOVES PASSED...HIPRES AT ALL LVLS BUILDS IN MON AND RESIDES NEARLY OVHD INTO LATE WEEK. THIS WILL MEAN DRY/NEARLY CLOUD-FREE CONDS MON THRU AT LEAST THU. TEMPS WILL BE AUTUMN- LIKE...BELOW AVG FOR MID-SEP. MAXIMA WILL BE GENERALLY IN 70S...XCPT 60S IN MOUNTAINS. MINIMA WILL BE IN 50S E OF BLUE RIDGE...WITH 40S W. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... IFR/MVFR DECK MOVING NW ACROSS BALT-WASH METRO EARLY THIS MORNING...ISOLATED SHOWERS/THUNDERSTORMS EXPECTED SOUTHEAST OF DC THROUGH SUNRISE. SOUTHERLY FLOW HAS HELD OFF FOG DEVELOPMENT. SUB VFR CONDITIONS LIKELY ON SATURDAY AS A STRONG COLD FRONT MOVES THROUGH. NUMEROUS SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE BOUNDARY. SOME STORMS MAY BE STRONG/SEVERE...WITH DAMAGING WIND GUSTS. PCPN ENDS AND CLOUDS GRADUALLY CLR SAT NGT...WITH VFR CONDS XPCD THRU MUCH OF NEXT WK. NW WINDS 10-20 KTS SUN/MON...DIMINISHING THEREAFTER AS HIPRES BUILDS IN. && .MARINE... LULL IN SLY SCA THROUGH SUNRISE...SCA LEVELS RETURN AFTER SUNRISE WITH SLY FLOW INCREASING AHEAD OF A COLD FRONT. LINE/S/ OF TSTMS EXPECTED LATE AFTERNOON INTO EVENING IN ADVANCE OF THE COLD FRONT. SPECIAL MARINE WARNINGS EXPECTED SINCE MAIN THREAT WITH THE WEATHER IS DAMAGING WINDS. SCA XTDD SAT NGT FOR ALL ZONES...AS GUSTY SLY WINDS WILL QUICKLY TRANSITION TO NLY AS CDFNT MOVES THRU. MAY BE A BRIEF PERIOD OF SUB-ADZY THRESHOLD WINDS IN ASSOCIATION WITH FROPA...BUT OTHERWISE 20-25 KT GUSTS SEEM LIKELY. GUSTY NW WINDS SUN WILL LIKELY REQUIRE ADDITIONAL ADZYS...AND THIS CUD CONT INTO MON. && .TIDES/COASTAL FLOODING... COASTAL FLOOD ADVISORY CANCELLED EARLY WITH LOWER THAN EXPECTED LEVELS AND CRESTS OCCURRED. TIDAL ANOMALIES EXPECTED TO REMAIN ABOUT THREE QUARTERS FOOT ABOVE ASTRONOMICAL PREDICTION INTO SATURDAY EVENING WITH SLY FLOW IN ADVANCE OF A COLD FRONT. POST FRONT WILL BE NWLY FLOW AND MORE NORMAL WATER LEVELS. WITH THE PREFERRED TIDE TONIGHT HAVING PAST...NO COASTAL FLOODING IS EXPECTED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ531>534-537- 539>541-543. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 6 AM EDT SUNDAY FOR ANZ530-538-542. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 6 PM EDT THIS EVENING FOR ANZ535-536. && $$ UPDATE...JACKSON
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
634 PM EDT SAT SEP 8 2012 .SYNOPSIS... ISSUED AT 252 PM EDT SAT SEP 8 2012 EXPECT SHOWERS AND ISOLATED THUNDERSTORMS NEAR LAKE MICHIGAN TONIGHT. THAT ACTIVITY WILL DIMINISH BY MID MORNING SUNDAY. OTHERWISE EXPECT COOLER WEATHER TO PREVAIL INTO THE BEGINNING OF THE WEEK. A WARMING TREND WILL BEGIN BY TUESDAY THAT WILL LAST INTO THE END OF THE WEEK. && .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 252 PM EDT SAT SEP 8 2012 THE PRIMARY FORECAST CONCERN IS THE AREA OF SHOWERS MOVING SOUTHEAST FROM WESTERN UPPER MICHIGAN AND HOW IT WILL IMPACT SOUTHWEST LOWER MICHIGAN OVERNIGHT AS IT MOVES THROUGH. OTHERWISE...I EXPECT TEMPERATURES TO FALL INTO THE 30S NEAR ROUTE 10 EAST OF THE LAKE SHORE SUNDAY NIGHT. AN EARLY TASTE OF FALL FOR SURE. A STRONG SHORTWAVE... WELL DEFINED ON THE WATER VAPOR LOOPS... WILL CONTINUE TO DROP SOUTHEAST CROSSING SOUTHWEST LOWER MICHIGAN DURING THE EARLY EVENING HOURS. THERE IS A 130 KNOT JET EXIT REGION THAT CROSSES SOUTHERN LAKE MICHIGAN JUST BEFORE MIDNIGHT ASSOCIATED WITH FEATURE. THIS JET CORE IS ROTATING AROUND THE BASE OF THE CLOSED 300 MB LOW THAT IS ALSO ASSOCIATED WITH THIS FEATURE. BOTH THE NAM12 AND HRRR RUC SUGGEST A MESO-LOW FEATURE WILL DEVELOP ON THE EAST SIDE (MICHIGAN SIDE)OF THE LAKE AN TRACK SOUTH THROUGH THE NIGHT ENHANCING THE CONVERGENCE OVER THE LAKE. GIVEN THE 850 MB TO LAKE TEMP DIFFERENCE IS NEAR 15C. BUFKIT SHOWS THE EQUILIBRIUM LEVEL OVERNIGHT WILL APPROACH 30000 FT AGL WITH NEARLY 2000 J/KG OF LAKE EDUCED CAPE. I AM THINKING THIS IS ENOUGH FOR SCT TO ISOLATED THUNDERSTORMS. LOCALLY HEAVY SHOWERS SHOULD BE EXPECTED. THAT THINKING IS CONFIRMED BY THE SPC SREF. NEARLY ALL OF THIS WILL MOSTLY BE OVER LAKE MICHIGAN AND WEST OF US-131 WHERE THE LAKE EDUCED INSTABILITY WILL BE A FACTOR. INLAND OF THAT EXPECT PARTLY CLOUDY SKIES WITH POSSIBLY A PASSING SHOWER AS THE UPPER WAVE MOVE THROUGH. ONCE THIS FEATURE EXITS THE AREA MID TO LATE MORNING SUNDAY THE UPPER RIDGE BUILDS IN THROUGH TUESDAY. THERE WILL BE ENOUGH INSTABILITY YET FOR ISOLATED SHOWERS SOUTH OF ROUTE 10 AND EAST OF US-131 SUNDAY AFTERNOON SINCE THE UPPER JET WILL NOT BE EAST OF THERE YET. SUNDAY NIGHT WITH SURFACE HIGH PRESSURE OVER THE AREA WINDS WILL BE LIGHT AND SKIES CLEAR. I EXPECT LOWS IN THE MID 30S OVER OUR NE CWA AND LOWER TO MID 40S ELSEWHERE. A SLOW WARMING TREND FOLLOWS THEN WITH MOSTLY CLEAR SKIES THROUGH TUESDAY NIGHT. .LONG TERM...(TUESDAY THROUGH SATURDAY) ISSUED AT 305 PM EDT SAT SEP 8 2012 WE/LL START TO WARM UP AGAIN TUESDAY AS THE HIGH MOVES TOWARD NEW ENGLAND. THE NEXT COLD FRONT WILL LIKELY MOVE ACROSS THE CWA THURSDAY NIGHT OR FRIDAY. INSTABILITY DOESN/T LOOK VERY IMPRESSIVE WITH THIS NOR DO THE MOISTURE TRANSPORT VECTORS. AS A RESULT I CAN/T SEE MUCH MORE THAN SLIGHT CHC POPS AT THIS POINT. THERE IS A COMPACT SHORT WAVE ASSOCIATED WITH THIS AND THAT MAY BOOST PCPN CHANCES INTO SATURDAY...BUT GIVEN THE SFC RIDGING MOVING IN AT THAT POINT...PCPN AMOUNTS AND CHANCES LOOK MEAGER. TEMPS WILL CLIMB TO AROUND 80 PRIOR TO FROPA AND THAN BACK INTO THE && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 146 PM EDT SAT SEP 8 2012 THERE IS CERTAINLY A DIURNAL LOOK TO THE CU FIELD AND WE/LL SEE ISOLD SHRA DIMINISH TOWARD SUSET AND SKIES WILL BECOME CLR-SCT. HOWEVER STRATOCU WILL INCREASE LATE TONIGHT AS THE NEXT COLD FRONT DROPS SOUTH. WINDS WILL VEER TO THE NNW 12Z-15Z AND CIGS SHOULD DEVELOP AROUND 4K FT. && .MARINE... ISSUED AT 633 PM EDT SAT SEP 8 2012 ISSUED ANOTHER SCA FOR THE NRN ZONE. GUSTY WINDS EXPECTED WITH THE NEXT COLD FRONT CURRENTLY MOVING ACROSS WISCONSIN. && .HYDROLOGY... ISSUED AT 252 PM EDT SAT SEP 8 2012 RIVERS WILL CONTINUE TO FALL SLOWLY THROUGH THIS COMING WEEK AS IT IS EXPECTED TO BE DRY MOST OF THIS COMING WEEK. ANY RAINFALL WE GET TONIGHT WILL ONLY BE NEAR THE LAKE SHORE AND THAT WILL NOT IMPACT MOST OF RIVERS. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR LMZ847>849. SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR LMZ844>846. && $$ SYNOPSIS...WDM SHORT TERM...WDM LONG TERM...93 AVIATION...93 HYDROLOGY...WDM MARINE...93
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
428 PM EDT SAT SEP 8 2012 .SHORT TERM...(THIS EVENING THROUGH SUNDAY) ISSUED AT 426 PM EDT SAT SEP 8 2012 MAIN FOCUS OF THE SHORT TERM IS THE STRONG SHORTWAVE SLIDING SSE THROUGH NE MN AND WRN LK SUPERIOR AND THE ASSOCIATED SFC COLD FRONT. AHEAD OF THIS SHORTWAVE...AREA OF SHOWERS HAS DROPPED OUT OF CANADA THIS MORNING AND INTO FAR WRN UPPER MI. EXPECT THESE SHOWERS TO CONTINUE TO SLIDE TO THE SE OVER THE COUNTIES NEAR THE WI BORDER THROUGH THE REST OF THIS AFTN...ASSOCIATED WITH THE H850-500 Q-VECTOR CONV. BEHIND THIS INITIAL AREAS OF SHOWERS AND THE FRONT...SCATTERED SHOWERS HAVE DEVELOPED UNDER THE CENTER OF THE SHORTWAVE AND ASSOCIATED WITH AREA OF STEEP MID LVL LAPSE RATES. THESE SHOWERS SHOULD CONTINUE TO THE SSE AND LARGELY MISS THE CWA...BUT COULD SEE SOME SCATTERED SHOWERS OVER THE WEST UNTIL DIURNAL HEATING IS LOST AND THE SHORTWAVE SLIDES S OF THE CWA. ATTENTION THEN TURNS TO POTENTIAL LK ENHANCED SHOWERS AND CLOUDS FOR TONIGHT. RUC ANALYSIS IS SHOWING THAT H850 TEMPS HAVE WARMED A DEGREE OR TWO FROM THIS MORNING...TOWARDS 6-7C OVER THE WEST AHEAD OF THE SHORTWAVE. ONCE THIS WAVE AND THE SFC FRONT SLIDE SE OF THE AREA...EXPECT H850 TEMPS TO FALL TOWARDS 5C BY THIS EVENING AND THEN 4C BY 12Z SUN. WITH LK SUPERIOR TEMPS IN THE 17-21C RANGE...THIS SHOULD PROVIDE DECENT DELTA-T VALUES FOR LK ENHANCED SHOWERS/CLOUDS. THE MAIN QUESTION FOR TONIGHT INTO SUN MORNING IS THE AMNT OF MOISTURE AND IT/S LOCATION. WITH THE TRACK OF THE SHORTWAVE AND MOISTURE UPSTREAM INTO ONTARIO...EXPECT FAR WRN UPPER MI TO SEE THE BEST OPPORTUNITY FOR LK ENHANCED SHOWERS UNDER THE NRLY BL FLOW. THAT AREA WILL BE AIDED BY COASTAL CONVERGENCE AND UPSLOPE FLOW...SO HAVE HIGH END CHANCE POPS THROUGH MUCH OF THE NIGHT. WITH A SLIGHT DELAY TO THE COLDEST TEMPS...MAY SEE A SHORT BREAK IN THE SHOWERS AFTER THE SUN GOES DOWN AND BEFORE THE COLD AIR ARRIVES. FARTHER NE IS A LITTLE MORE UNCERTAIN. MODELS SHOWING H850-700 DRY AIR DROPPING S FROM CNTRL ONTARIO AND OVER CNTRL/ERN LK SUPERIOR THIS EVENING AND OVER CNTRL/ERN UPPER MI OVERNIGHT. WITH THE LACK OF CU THAT HAS DEVELOPED NE OF THUNDER BAY...THAT SEEMS FAIRLY REASONABLE. BUT...H925-850 MOISTURE AND STEEP LAPSE RATES OVER LK SUPERIOR WITH THE NRLY FLOW SHOULD STILL PRODUCE ISOLATED TO POTENTIALLY SCATTERED LK ENHANCED SHOWERS OVER THE NCNTRL CWA WITH THE LIMITED CLOUD DEPTH KEEPING THEM LIGHT. ALL OF THESE SHOWERS MAY BE HELPED BY A SECONDARY SHORTWAVE FROM NW ONTARIO MOVING THROUGH OVERNIGHT. FOR TOMORROW...WITH LINGERING LLVL MOISTURE AND 3-4C H850 TEMPS...THE NNW WIND FAVORED LOCATIONS SHOULD SEE PARTLY/MOSTLY CLOUDY SKIES THROUGH THE MORNING HOURS. STILL LINGERED LIGHT SHOWERS THROUGH THE MORNING...BUT LIMITED MOISTURE DEPTH SUPPORTS ONLY HAVING SLIGHT CHANCES. OVER THE CNTRL/EAST IN THE AFTN...MOISTURE THAT IS CURRENTLY OVER NW ONTARIO SHOULD DROP OVER THE ERN LK AND WITH THE COLD TEMPS REINFORCE THE CLOUD DECK. NCEP WRF NMM/ARW RUNS HAVE SHOWN THE POTENTIAL FOR SHOWERS WITH THIS WAVE...BUT CONCERNED DRIER AIR ALOFT WILL KEEP CLOUDS FROM DEVELOPING TOO MUCH. FARTHER WEST...HIGH PRESSURE BUILDING IN UNDER THE UPPER RIDGING WILL HELP BRING DRIER AIR INTO THE AREA AND DECREASE THE CLOUDS DURING THE AFTN AND LEAD TO CLEARING AFTER 21Z. FINALLY...WITH THE NORTHERLY WINDS CREATING 3-5FT WAVES TOMORROW...EXPECT A MODERATE TO HIGH RISK OF RIP CURRENTS TO CONTINUE TOMORROW. .LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY) ISSUED AT 426 PM EDT SAT SEP 8 2012 MEDIUM RANGE GUIDANCE CONTINUES TO BE IN GENERAL AGREEMENT ON THE BIG PICTURE OVER THE NEXT 7 DAYS AS IT PERTAINS TO UPPER MI. AFTER THIS WEEKENDS TROF...PATTERN WILL BECOME MORE PROGRESSIVE NEXT WEEK. THE TROF DOMINATING THE GREAT LAKES THIS WEEKEND WILL BE FOLLOWED BY RIDGING EARLY IN THE WEEK...A TROF FOR THE MID/LATE PORTION OF THE WEEK...AND ANOTHER TROF LATE NEXT WEEKEND. THE EVOLUTION/STRUCTURE OF THE MID/LATE WEEK TROF REMAINS THE MAIN AREA OF MODEL DISAGREEMENT. WITH A PROGRESSIVE PATTERN...TEMPS WILL SHOW A FAIR AMOUNT OF VARIATION OVER THE NEXT 7 DAYS. TEMPS A LITTLE BLO NORMAL THRU THE WEEKEND WITH TROFFING OVER THE GREAT LAKES WILL TRANSITION TO STRONG WARMING/ABOVE NORMAL TEMPS EARLY IN THE WEEK AHEAD OF THE NEXT APPROACHING TROF. GRADUAL COOLING WILL OCCUR MIDWEEK...LEADING TO TEMPS AROUND NORMAL LATE IN THE WORK WEEK AS MID/UPPER LEVEL TROF PASSES. TEMPS WILL THEN BEGIN TO REBOUND FOR THE START OF NEXT WEEKEND. AS FOR PCPN...THIS WILL BE AN OVERALL DRY PERIOD DUE TO LACK OF GULF MOISTURE TRANSPORT TO THE UPPER LAKES AND DUE TO MAIN FORCING PASSING N OF THE AREA WHEN SHORTWAVES PASS. BEGINNING SUN NIGHT...WITH SFC HIGH PRES RIDGE PASSING ACROSS THE AREA...CLR SKIES AND PRECIPITABLE WATER 45-65PCT OF NORMAL...A GOOD RADIATIONAL COOLING NIGHT IS EXPECTED. MINS ON THE LOW SIDE OF AVBL GUIDANCE LOOK ON TRACK. TRADITIONAL INTERIOR COLD SPOTS SHOULD DROP TO THE UPPER...POSSIBLY MID...30S. MIGHT SEE A LITTLE FROST. AS MID LEVEL RIDGE SHIFTS TO THE UPPER LAKES MON...WAA WILL BE UNDERWAY. LOW-LEVEL JET/STRONGEST PUSH OF WARMING IS WELL TO THE NNW MON...SO PCPN IS NOT A CONCERN. TEMPS SHOULD REBOUND INTO THE 70S UNDER WAA PATTERN. AS THE MID LEVEL RIDGE SHIFTS E TUE AND NEXT TROF BEGINS TO MOVE OUT OVER THE NRN PLAINS...850MB THERMAL RIDGE (TEMPS OF 16-19C) WILL TRANSLATE OVER THE AREA. ALTHOUGH THERE REMAINS SOME CONCERN WITH MID/HIGH CLOUD COVERAGE TUE...THERMAL RIDGE AND BREEZY S-SW WINDS WILL LEAD TO A WARM DAY FOR EARLY/MID SEPT...ESPECIALLY OVER THE W HALF. WILL STAY WITH HIGH TEMPS MAINLY LOW/MID 80S...ABOVE ALL GUIDANCE IN MOST AREAS. NOT TOTALLY OUT OF THE QUESTION THAT SOME OF THE DOWNSLOPE AREAS OVER THE W TOWARD LAKE SUPERIOR COULD FLIRT WITH 90F IF THE DAY ENDS UP SUNNY. COOLER READINGS WILL BE OVER THE E WITH FLOW UP LAKE MICHIGAN. WITH LOW-LEVEL JET TRANSLATING ACROSS THE AREA...THERE IS A VERY SMALL POTENTIAL FOR SOME CONVECTION...BUT LACK OF BETTER MOISTURE MINIMIZES THE POTENTIAL. MEDIUM RANGE GUIDANCE HAS CONTINUED TO SLOW DOWN SLIGHTLY THE COLD FRONT ASSOCIATED WITH THE INCOMING MID LEVEL TROF MIDWEEK. IT NOW APPEARS FRONT WILL BE CROSSING THE AREA DURING THE DAY WED. WITH BEST DEEP LAYER FORCING PASSING WELL TO THE N AND WITH A LACK OF A GOOD GULF MOISTURE CONNECTION...THERE SHOULDN`T BE MUCH PCPN ASSOCIATED WITH THE FRONT. HOWEVER...WITH THE UPPER TROF TAKING ON A POSITIVE TILT FROM HUDSON BAY TO THE NRN PLAINS THRU THU...THE SUPPORTING SW-NE ORIENTED UPPER JET WILL SLOWLY TRANSLATE EASTWARD. AS IT DOES...RIGHT ENTRANCE UPPER DIVERGENCE WILL BEGIN TO OVERLAY THE LOW-LEVEL FRONT...LIKELY LEADING TO A RIBBON SHRA EVENTUALLY DEVELOPING ALONG/BEHIND SFC FRONT AS SUGGESTED BY THE GFS/ECMWF/GLOBAL GEM. THUS...PLAN TO MAINTAIN SCHC POPS OVER THE FAR W LATE TUE NIGHT INTO WED WITH SCHC POPS EXPANDING INTO THE CNTRL WED AND THEN CHC POPS OVER THE E HALF WED NIGHT. INSTABILITY IS VERY LIMITED...SO POTENTIAL OF THUNDER IS MINIMAL. LINGERED SCHC POPS OVER ALL BUT THE FAR W THU GIVEN MODEL TRENDS...BUT MAY NEED TO INCREASE THU POPS TO CHC IF CONSISTENCY DEVELOPS FOR SLOW FRONTAL MOVEMENT AND AN INCREASED POST FRONTAL PCPN BAND WITH TIME DUE TO UPPER JET. SINCE YESTERDAY`S RUNS...GFS/ECMWF HAVE TRENDED COOLER FOR FRI AS THE MID/UPPER LEVEL TROF PASSES (850MB TEMPS 3-5C TO START THE DAY). AS A RESULT...TEMPS WILL BE BACK AROUND NORMAL MID SEPT VALUES (60S FOR HIGHS). MIGHT BE SOME LAKE EFFECT -SHRA FRI MORNING IN THE CHILLY NW FLOW. OTHERWISE...DRY WEATHER IS EXPECTED FRI. HOWEVER... IT IS NOTED THAT THE 00Z GFS AND NOW THE 12Z ECMWF SHOW ENERGY IN THE SRN PORTION OF PASSING TROF SEPARATING OUT AND LEADING TO A MID LEVEL LOW TRACKING INTO THE UPPER LAKES FRI INTO EARLY SAT. GIVEN THE VERY INCONSISTENT SIGNAL...WILL IGNORE THIS IDEA FOR NOW. WILL BE SOMETHING TO KEEP IN MIND WHICH MAY CHANGE THE CURRENT DRY FCST TO A POSSIBLE GOOD SOAKING. IN THE ABSENCE OF THE POSSIBLE MID LEVEL LOW...DRY WEATHER/WARMING IS EXPECTED SAT AS WEAK MID LEVEL RIDGE ARRIVES. NEXT SHORTWAVE TROF SHOULD ARRIVE SUN. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 133 PM EDT SAT SEP 8 2012 STRONG SHORTWAVE DROPPING SSE THROUGH NORTHERN MN ALONG WITH SFC COLD FRONT WILL BRING SCATTERED/NUMEROUS SHOWERS TO WRN UPPER MI THIS AFTN. THINK THE SHOWERS WILL MAINLY STAY SW OF KCMX/KSAW...SO HAVE LEFT OUT PREDOMINATE -SHRA FOR THOSE SITES THIS AFTN. DUE TO THE DYNAMICS WITH THE SYSTEM...THERE COULD BE A RUMBLE OF THUNDER AT KIWD BUT NOT CONFIDENT ON PROXIMITY TO THE TAF SITE...SO HAVE LEFT OUT. BEHIND THE FRONT AND SHORTWAVE...EXPECT A TRANSITION TO LK ENHANCED CLOUDS/RAIN TO OCCUR THIS EVENING AND CONTINUE THROUGH MUCH OF THE TAF PERIOD. WITH THE BEST MOISTURE/FETCH AFFECTING KIWD...HAVE CONTINUED THE MENTION OF MVFR CONDITIONS TONIGHT THROUGH THE MORNING HOURS. DRIER AIR ALOFT LEADS TO MORE UNCERTAINTY ON THE COVERAGE OF CLOUDS AND RAIN POTENTIAL AT KCMX/KSAW...SO WILL GO WITH VFR CONDITIONS FOR NOW. && .MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE) ISSUED AT 426 PM EDT SAT SEP 8 2012 A SFC TROUGH DROPPING SE ACROSS LAKE SUPERIOR THIS EVENING WILL BRING A REINFORCING SHOT OF COLD AIR AND STRENGTHEN THE NNW WINDS ACROSS LAKE SUPERIOR. THE HIGHEST GUSTS...TO 30KTS...WILL BE SEEN OVER FAR WRN LK SUPERIOR...WILL THE REST OF THE LAKE WILL SEE 15-25KTS TONIGHT INTO TOMORROW. HIGH PRESSURE WILL BUILD OVER THE UPPER GREAT LAKES TOMORROW AND LEAD TO WEAKENING WINDS SUN AFTN AND SUNDAY NIGHT. AS THE HIGH QUICKLY SHIFTS TO THE LOWER GREAT LAKES ON MONDAY...SOUTHERLY WINDS WILL INCREASE AND PRODUCE A PERSISTENT PERIOD OF 15-25KT WINDS THROUGH TUESDAY NIGHT WHEN A COLD FRONT PUSHES ACROSS LAKE SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... NONE. LAKE SUPERIOR... NONE. LAKE MICHIGAN... NONE. && $$ SHORT TERM...SRF LONG TERM...ROLFSON AVIATION...SRF MARINE...SRF
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
306 PM EDT SAT SEP 8 2012 .SYNOPSIS... ISSUED AT 252 PM EDT SAT SEP 8 2012 EXPECT SHOWERS AND ISOLATED THUNDERSTORMS NEAR LAKE MICHIGAN TONIGHT. THAT ACTIVITY WILL DIMINISH BY MID MORNING SUNDAY. OTHERWISE EXPECT COOLER WEATHER TO PREVAIL INTO THE BEGINNING OF THE WEEK. A WARMING TREND WILL BEGIN BY TUESDAY THAT WILL LAST INTO THE END OF THE WEEK. && .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 252 PM EDT SAT SEP 8 2012 THE PRIMARY FORECAST CONCERN IS THE AREA OF SHOWERS MOVING SOUTHEAST FROM WESTERN UPPER MICHIGAN AND HOW IT WILL IMPACT SOUTHWEST LOWER MICHIGAN OVERNIGHT AS IT MOVES THROUGH. OTHERWISE...I EXPECT TEMPERATURES TO FALL INTO THE 30S NEAR ROUTE 10 EAST OF THE LAKE SHORE SUNDAY NIGHT. AN EARLY TASTE OF FALL FOR SURE. A STRONG SHORTWAVE... WELL DEFINED ON THE WATER VAPOR LOOPS... WILL CONTINUE TO DROP SOUTHEAST CROSSING SOUTHWEST LOWER MICHIGAN DURING THE EARLY EVENING HOURS. THERE IS A 130 KNOT JET EXIT REGION THAT CROSSES SOUTHERN LAKE MICHIGAN JUST BEFORE MIDNIGHT ASSOCIATED WITH FEATURE. THIS JET CORE IS ROTATING AROUND THE BASE OF THE CLOSED 300 MB LOW THAT IS ALSO ASSOCIATED WITH THIS FEATURE. BOTH THE NAM12 AND HRRR RUC SUGGEST A MESO-LOW FEATURE WILL DEVELOP ON THE EAST SIDE (MICHIGAN SIDE)OF THE LAKE AN TRACK SOUTH THROUGH THE NIGHT ENHANCING THE CONVERGENCE OVER THE LAKE. GIVEN THE 850 MB TO LAKE TEMP DIFFERENCE IS NEAR 15C. BUFKIT SHOWS THE EQUILIBRIUM LEVEL OVERNIGHT WILL APPROACH 30000 FT AGL WITH NEARLY 2000 J/KG OF LAKE EDUCED CAPE. I AM THINKING THIS IS ENOUGH FOR SCT TO ISOLATED THUNDERSTORMS. LOCALLY HEAVY SHOWERS SHOULD BE EXPECTED. THAT THINKING IS CONFIRMED BY THE SPC SREF. NEARLY ALL OF THIS WILL MOSTLY BE OVER LAKE MICHIGAN AND WEST OF US-131 WHERE THE LAKE EDUCED INSTABILITY WILL BE A FACTOR. INLAND OF THAT EXPECT PARTLY CLOUDY SKIES WITH POSSIBLY A PASSING SHOWER AS THE UPPER WAVE MOVE THROUGH. ONCE THIS FEATURE EXITS THE AREA MID TO LATE MORNING SUNDAY THE UPPER RIDGE BUILDS IN THROUGH TUESDAY. THERE WILL BE ENOUGH INSTABILITY YET FOR ISOLATED SHOWERS SOUTH OF ROUTE 10 AND EAST OF US-131 SUNDAY AFTERNOON SINCE THE UPPER JET WILL NOT BE EAST OF THERE YET. SUNDAY NIGHT WITH SURFACE HIGH PRESSURE OVER THE AREA WINDS WILL BE LIGHT AND SKIES CLEAR. I EXPECT LOWS IN THE MID 30S OVER OUR NE CWA AND LOWER TO MID 40S ELSEWHERE. A SLOW WARMING TREND FOLLOWS THEN WITH MOSTLY CLEAR SKIES THROUGH TUESDAY NIGHT. .LONG TERM...(TUESDAY THROUGH SATURDAY) ISSUED AT 305 PM EDT SAT SEP 8 2012 WE/LL START TO WARM UP AGAIN TUESDAY AS THE HIGH MOVES TOWARD NEW ENGLAND. THE NEXT COLD FRONT WILL LIKELY MOVE ACROSS THE CWA THURSDAY NIGHT OR FRIDAY. INSTABILITY DOESN/T LOOK VERY IMPRESSIVE WITH THIS NOR DO THE MOISTURE TRANSPORT VECTORS. AS A RESULT I CAN/T SEE MUCH MORE THAN SLIGHT CHC POPS AT THIS POINT. THERE IS A COMPACT SHORT WAVE ASSOCIATED WITH THIS AND THAT MAY BOOST PCPN CHANCES INTO SATURDAY...BUT GIVEN THE SFC RIDGING MOVING IN AT THAT POINT...PCPN AMOUNTS AND CHANCES LOOK MEAGER. TEMPS WILL CLIMB TO AROUND 80 PRIOR TO FROPA AND THAN BACK INTO THE 70S BY THE WEEKEND. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 146 PM EDT SAT SEP 8 2012 THERE IS CERTAINLY A DIURNAL LOOK TO THE CU FIELD AND WE/LL SEE ISOLD SHRA DIMINISH TOWARD SUSET AND SKIES WILL BECOME CLR-SCT. HOWEVER STRATOCU WILL INCREASE LATE TONIGHT AS THE NEXT COLD FRONT DROPS SOUTH. WINDS WILL VEER TO THE NNW 12Z-15Z AND CIGS SHOULD DEVELOP AROUND 4K FT. && .MARINE... ISSUED AT 252 PM EDT SAT SEP 8 2012 I WILL CONTINUE THE SMALL CRAFT ADVISORIES AS IS INTO SUNDAY. IT SHOULD BE NOTED THAT THERE CURRENTLY ARE GUSTY WINDS BEHIND THE TROUGH AT THE SURFACE OVER NE MINNESOTA. THE HRRR RUC SHOWS AN AREA OF 40 TO 50 KNOT WINDS OVER THE CENTRAL PART OF LAKE MICHIGAN JUST BEHIND THE THROUGH OVERNIGHT. SO IN THE NEAR SHORE WATERS EXPECT WINDS TO INCREASE SIGNIFICANTLY LATER TONIGHT FOR A FEW HOURS BEHIND THE THROUGH. ALL OF THIS WILL END FROM NORTH TO SOUTH DURING THE DAY SUNDAY AS THE SYSTEM MOVES OUT. && .HYDROLOGY... ISSUED AT 252 PM EDT SAT SEP 8 2012 RIVERS WILL CONTINUE TO FALL SLOWLY THROUGH THIS COMING WEEK AS IT IS EXPECTED TO BE DRY MOST OF THIS COMING WEEK. ANY RAINFALL WE GET TONIGHT WILL ONLY BE NEAR THE LAKE SHORE AND THAT WILL NOT IMPACT MOST OF RIVERS. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR LMZ849. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR LMZ847-848. SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR LMZ844>846. && $$ SYNOPSIS...WDM SHORT TERM...WDM LONG TERM...93 AVIATION...93 HYDROLOGY...WDM MARINE...WDM
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
254 PM EDT SAT SEP 8 2012 .SYNOPSIS... ISSUED AT 252 PM EDT SAT SEP 8 2012 EXPECT SHOWERS AND ISOLATED THUNDERSTORMS NEAR LAKE MICHIGAN TONIGHT. THAT ACTIVITY WILL DIMINISH BY MID MORNING SUNDAY. OTHERWISE EXPECT COOLER WEATHER TO PREVAIL INTO THE BEGINNING OF THE WEEK. A WARMING TREND WILL BEGIN BY TUESDAY THAT WILL LAST INTO THE END OF THE WEEK. && .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 252 PM EDT SAT SEP 8 2012 THE PRIMARY FORECAST CONCERN IS THE AREA OF SHOWERS MOVING SOUTHEAST FROM WESTERN UPPER MICHIGAN AND HOW IT WILL IMPACT SOUTHWEST LOWER MICHIGAN OVERNIGHT AS IT MOVES THROUGH. OTHERWISE...I EXPECT TEMPERATURES TO FALL INTO THE 30S NEAR ROUTE 10 EAST OF THE LAKE SHORE SUNDAY NIGHT. AN EARLY TASTE OF FALL FOR SURE. A STRONG SHORTWAVE... WELL DEFINED ON THE WATER VAPOR LOOPS... WILL CONTINUE TO DROP SOUTHEAST CROSSING SOUTHWEST LOWER MICHIGAN DURING THE EARLY EVENING HOURS. THERE IS A 130 KNOT JET EXIT REGION THAT CROSSES SOUTHERN LAKE MICHIGAN JUST BEFORE MIDNIGHT ASSOCIATED WITH FEATURE. THIS JET CORE IS ROTATING AROUND THE BASE OF THE CLOSED 300 MB LOW THAT IS ALSO ASSOCIATED WITH THIS FEATURE. BOTH THE NAM12 AND HRRR RUC SUGGEST A MESO-LOW FEATURE WILL DEVELOP ON THE EAST SIDE (MICHIGAN SIDE)OF THE LAKE AN TRACK SOUTH THROUGH THE NIGHT ENHANCING THE CONVERGENCE OVER THE LAKE. GIVEN THE 850 MB TO LAKE TEMP DIFFERENCE IS NEAR 15C. BUFKIT SHOWS THE EQUILIBRIUM LEVEL OVERNIGHT WILL APPROACH 30000 FT AGL WITH NEARLY 2000 J/KG OF LAKE EDUCED CAPE. I AM THINKING THIS IS ENOUGH FOR SCT TO ISOLATED THUNDERSTORMS. LOCALLY HEAVY SHOWERS SHOULD BE EXPECTED. THAT THINKING IS CONFIRMED BY THE SPC SREF. NEARLY ALL OF THIS WILL MOSTLY BE OVER LAKE MICHIGAN AND WEST OF US-131 WHERE THE LAKE EDUCED INSTABILITY WILL BE A FACTOR. INLAND OF THAT EXPECT PARTLY CLOUDY SKIES WITH POSSIBLY A PASSING SHOWER AS THE UPPER WAVE MOVE THROUGH. ONCE THIS FEATURE EXITS THE AREA MID TO LATE MORNING SUNDAY THE UPPER RIDGE BUILDS IN THROUGH TUESDAY. THERE WILL BE ENOUGH INSTABILITY YET FOR ISOLATED SHOWERS SOUTH OF ROUTE 10 AND EAST OF US-131 SUNDAY AFTERNOON SINCE THE UPPER JET WILL NOT BE EAST OF THERE YET. SUNDAY NIGHT WITH SURFACE HIGH PRESSURE OVER THE AREA WINDS WILL BE LIGHT AND SKIES CLEAR. I EXPECT LOWS IN THE MID 30S OVER OUR NE CWA AND LOWER TO MID 40S ELSEWHERE. A SLOW WARMING TREND FOLLOWS THEN WITH MOSTLY CLEAR SKIES THROUGH TUESDAY NIGHT. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 330 AM EDT SAT SEP 8 2012 LONG TERM BEGINS MONDAY NIGHT WITH RIDGING IN PLACE AT 500MB/S. THE RIDGING REMAINS INTO WEDNESDAY MORNING. ON WEDNESDAY...A DEEP UPPER LOW PROGRESSING ACROSS CANADA WILL FLATTEN THE GREAT LAKES RIDGE...RESULTING IN MORE OF A ZONAL FLOW FOR THE REMAINDER OF THE PERIOD. THE GFS AND ECMWF HAVE TIMING DIFFERENCE BUT BOTH BRING AN UPPER SHORTWAVE TROUGH THROUGH THE REGION THE LATTER HALF OF THE WORK WEEK. AT THE SURFACE...HIGH PRESSURE WILL SLIP AWAY FROM THE GREAT LAKES ON TUESDAY RESULTING IN A WARMER RETURN FLOW TUES/WED. DRY WX IS EXPECTED FROM MONDAY NIGHT INTO WEDNESDAY NIGHT. WEAK SURFACE TROUGHING MOVES THROUGH THE FORECAST AREA THURS/FRI. HAVE SMALL POPS LATE WEDNESDAY NIGHT THROUGH FRIDAY AS THE TROUGH MOVES THROUGH...BUT NOT EXPECTING SIGNIFICANT PRECIPITATION AT THIS POINT. TEMPERATURES WILL BE ABOVE NORMAL TUES/WED IN SOUTHERLY FLOW...DROPPING BACK CLOSER TO NORMAL BY WEEKS END. OVERALL A FAIRLY BENIGN PATTERN. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 146 PM EDT SAT SEP 8 2012 THERE IS CERTAINLY A DIURNAL LOOK TO THE CU FIELD AND WE/LL SEE ISOLD SHRA DIMINISH TOWARD SUSET AND SKIES WILL BECOME CLR-SCT. HOWEVER STRATOCU WILL INCREASE LATE TONIGHT AS THE NEXT COLD FRONT DROPS SOUTH. WINDS WILL VEER TO THE NNW 12Z-15Z AND CIGS SHOULD DEVELOP AROUND 4K FT. && .MARINE... ISSUED AT 252 PM EDT SAT SEP 8 2012 I WILL CONTINUE THE SMALL CRAFT ADVISORIES AS IS INTO SUNDAY. IT SHOULD BE NOTED THAT THERE CURRENTLY ARE GUSTY WINDS BEHIND THE TROUGH AT THE SURFACE OVER NE MINNESOTA. THE HRRR RUC SHOWS AN AREA OF 40 TO 50 KNOT WINDS OVER THE CENTRAL PART OF LAKE MICHIGAN JUST BEHIND THE THROUGH OVERNIGHT. SO IN THE NEAR SHORE WATERS EXPECT WINDS TO INCREASE SIGNIFICANTLY LATER TONIGHT FOR A FEW HOURS BEHIND THE THROUGH. ALL OF THIS WILL END FROM NORTH TO SOUTH DURING THE DAY SUNDAY AS THE SYSTEM MOVES OUT. && .HYDROLOGY... ISSUED AT 252 PM EDT SAT SEP 8 2012 RIVERS WILL CONTINUE TO FALL SLOWLY THROUGH THIS COMING WEEK AS IT IS EXPECTED TO BE DRY MOST OF THIS COMING WEEK. ANY RAINFALL WE GET TONIGHT WILL ONLY BE NEAR THE LAKE SHORE AND THAT WILL NOT IMPACT MOST OF RIVERS. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR LMZ849. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR LMZ847-848. SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR LMZ844>846. && $$ SYNOPSIS...WDM SHORT TERM...WDM LONG TERM...DUKE AVIATION...93 HYDROLOGY...WDM MARINE...WDM
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
321 PM CDT SAT SEP 8 2012 .DISCUSSION.../ISSUED 320 PM CDT SAT SEP 8/ WINDS AND CLOUD COVER WILL DECREASE NOTABLY AFTER SUNSET...AND WILL ALLOW TEMPERATURES TO FALL INTO THE 40S OVERNIGHT. COOL AND DRY HIGH PRESSURE WILL THEN PREVAIL ON SUNDAY AS THE GREAT LAKES TROUGH DIGS TOWARD THE EAST COAST. SUNDAY HIGHS WILL BE RIGHT AROUND NORMAL...AND GENERALLY RANGE FROM 70 TO 75 DEGREES. MID LEVEL RIDGING WILL ARRIVE INTO THE NORTH CENTRAL CONUS FOR MONDAY...AND SOUTHERLY LOW LEVEL FLOW WILL DEVELOP AS A TROUGH STRENGTHENS OVER THE NORTHERN/CENTRAL PLAINS. BY MONDAY AFTERNOON...SUSTAINED WINDS OF 15 TO 25 MPH...WITH GUSTS INTO THE 30S APPEAR LIKELY OVER WEST/SOUTH CENTRAL MN. ALTHOUGH MOISTURE WILL BE SLOWLY INCREASING...DEWPOINTS WILL LIKELY ONLY BE IN THE 45 TO 50 DEGREE RANGE. THEREFORE...THE COMBINATION OF STRONG WINDS...RELATIVELY LOW HUMIDITY VALUES...AND DRY FUELS...WILL CONTINUE TO SET THE STAGE FOR ENHANCED FIRE DANGER ON MONDAY AFTERNOON/EVE AND POSSIBLY TUESDAY. /SEE THE FIRE WEATHER DISCUSSION BELOW FOR MORE INFORMATION/. TUESDAY WILL BE QUITE WARM ACROSS CENTRAL AND SOUTH CENTRAL MN AS THE THERMAL RIDGE NOSES INTO THE AREA WITH THE ADVANCING FRONT. HIGHS AROUND OR EVEN ABOVE 90 DEGREES APPEAR LIKELY ACROSS THE HEART OF THE CWA. REALLY APPEARS AS IF THE FRONT WILL COME THROUGH DRY...WITH CHANCE POPS HOLDING OFF UNTIL WEDNESDAY AS REINFORCING MOISTURE AND DYNAMICS WITH A SHORTWAVE EJECTING NORTHEAST FROM THE FOUR CORNERS REGION ARRIVE. SHOWER/TS POTENTIAL APPEARS THE HIGHEST OVER SOUTHERN MN INTO WEST CENTRAL WI. ON THURSDAY...A NORTHERN STREAM WAVE WILL BRING A REINFORCING SHOT OF MORE SEASONAL AIR INTO THE UPPER MIDWEST. THURSDAY/FRIDAY HIGHS WILL TOP OUT IN THE UPPER 60S AND LOWER 70S...AND LOWS WILL DIP INTO THE 40S. MID LEVEL RIDGING WILL BUILD BACK INTO THE CENTRAL UNITED STATES FOR THE WEEKEND OF THE 15TH...AND YIELD ANOTHER RETURN TO DRY WEATHER WITH ABOVE NORMAL TEMPERATURES. && .AVIATION... /18Z TAF ISSUANCE/ STRONG COLD FRONT STILL ON SCHEDULE...DROPPING INTO CENTRAL MN NOW AND EXITING SOUTHERN MN AFTER 23Z. SHRA ASSOCIATED SHOULD BE LIMITED TO WC WI...WITH ISOLD TSRA PSBL. CONTINUED THE TREND OF VCSH AT KRNH AND KEAU...WITH VCTS PSBL AT KEAU...FOR A COUPLE HOURS THIS AFTERNOON WITH FROPA. STRONG NW WINDS DEVELOPING BEHIND FRONT WITH 35 KNOT GUSTS POSSIBLE MOST AREAS. SHOULD SEE GUSTINESS NED 03Z-04Z MOST AREAS. QUESTION REMAINS AS TO EXTENT OF POSSIBLE MVFR CEILINGS OVER EASTERN AREAS DURING THE NIGHT. THE 12Z RAP WAS MOST PESSIMISTIC WITH LOWER CLOUDS AFFECTING KMSP EAST OVERNIGHT. WILL LIMIT TO SCT040 OVER EASTERN MN AND MENTION CEILINGS DOWN TO 3500 FEET INTO WI OVERNIGHT FOR NOW. SUBSIDENCE WILL BE STRONG BEHIND SYSTEM BUT NAM CONTINUES TO INDICATE SOME FAIRLY HIGH LOWER LEVEL RH AROUND. SUNDAY SHOULD BE LESS EVENTFUL WITH LIGHTER NORTH WINDS AS SURFACE HIGH DROPS SOUTH. MAYBE SOME CUMULUS INTO THE AFTERNOON OVER EASTERN AREAS...BUT SHOULD DISSIPATE LATE BY LATE AFTERNOON. KMSP...SOME CLOUDS AROUND WITH FROPA THIS AFTERNOON. MAY LINGER AS CAA STRATOCUMULUS INTO THE EVENING. WILL LEAVE AS SCT FOR NOW. SOME INDICATION OF LOWER MVFR CEILING DEVELOPING...BUT MAINLY TO THE EAST OF THE AREA. STRONG NORTHWEST WINDS WITH FROPA WILL DISSIPATE AFTER SUNSET. LIGHT NORTH WINDS THEN INTO SUNDAY WITH PERHAPS A FEW CUMULUS INTO THE AFTERNOON. /OUTLOOK FOR KMSP/ .MONDAY...VFR. WINDS S 15 TO 20 KTS WITH GUSTS TO 30 KTS. .TUESDAY...VFR. WINDS SSW 15 TO 20 KTS WITH GUSTS TO 25 KTS. .WEDNESDAY...MAINLY VFR WITH A CHC OF SHRA/TSRA. WINDS NW 7 KTS. && .FIRE WEATHER.../ISSUED 320 PM CDT SAT SEP 8/ THERE IS A HEIGHTENED FIRE DANGER ON MONDAY AND TUESDAY AHEAD OF A DEVELOPING LOW PRESSURE SYSTEM OVER THE NORTHERN PLAINS. SOUTHERLY WINDS WILL INCREASE TO 20 TO 25 MPH WITH GUSTS TO 30 MPH AHEAD OF THIS SYSTEM ON MONDAY...AS MOSTLY SUNNY SKIES ALLOW FOR TEMPERATURES TO WARM INTO THE LOW TO MID 80S FROM WEST INTO SOUTH CENTRAL MN. THE WARM TEMPERATURES WILL COMBINE WITH RELATIVELY LOW DEWPOINTS IN THE MID 40S TO YIELD AFTERNOON HUMIDITY VALUES IN THE LOW TO MID 20S. THE DRY VEGETATION AND FUELS IN DROUGHT AREAS OF WEST AND SOUTH CENTRAL MN...COMBINED WITH THE EXPECTED WEATHER CONDITIONS...WILL LEAD TO ELEVATED FIRE DANGER ON MONDAY AFTERNOON AND EVENING. THEREFORE...A FIRE WEATHER WATCH HAS BEEN ISSUED FOR MUCH OF WEST CENTRAL...SOUTHWEST...AND SOUTH CENTRAL MN ON MONDAY. THE FIRE DANGER CONDITIONS MAY EXTEND THROUGH TUESDAY DEPENDING ON THE TIMING WITH THE APPROACHING FRONTAL BOUNDARY. STAY TUNED TO FUTURE FIRE WEATHER PRODUCTS AND DISCUSSIONS FOR UPDATED THINKING. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...FIRE WEATHER WATCH FROM MONDAY MORNING THROUGH MONDAY EVENING FOR BLUE EARTH-BROWN-CHIPPEWA-DOUGLAS-FARIBAULT-FREEBORN- KANDIYOHI-LAC QUI PARLE-MARTIN-NICOLLET-POPE-REDWOOD- RENVILLE-SIBLEY-STEVENS-SWIFT-WASECA-WATONWAN-YELLOW MEDICINE. WI...NONE. && $$ LS/DWE
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1225 PM CDT SAT SEP 8 2012 .AVIATION... /18Z TAF ISSUANCE/ STRONG COLD FRONT STILL ON SCHEDULE...DROPPING INTO CENTRAL MN NOW AND EXITING SOUTHERN MN AFTER 23Z. SHRA ASSOCIATED SHOULD BE LIMITED TO WC WI...WITH ISOLD TSRA PSBL. CONTINUED THE TREND OF VCSH AT KRNH AND KEAU...WITH VCTS PSBL AT KEAU...FOR A COUPLE HOURS THIS AFTERNOON WITH FROPA. STRONG NW WINDS DEVELOPING BEHIND FRONT WITH 35 KNOT GUSTS POSSIBLE MOST AREAS. SHOULD SEE GUSTINESS NED 03Z-04Z MOST AREAS. QUESTION REMAINS AS TO EXTENT OF POSSIBLE MVFR CEILINGS OVER EASTERN AREAS DURING THE NIGHT. THE 12Z RAP WAS MOST PESSIMISTIC WITH LOWER CLOUDS AFFECTING KMSP EAST OVERNIGHT. WILL LIMIT TO SCT040 OVER EASTERN MN AND MENTION CEILINGS DOWN TO 3500 FEET INTO WI OVERNIGHT FOR NOW. SUBSIDENCE WILL BE STRONG BEHIND SYSTEM BUT NAM CONTINUES TO INDICATE SOME FAIRLY HIGH LOWER LEVEL RH AROUND. SUNDAY SHOULD BE LESS EVENTFUL WITH LIGHTER NORTH WINDS AS SURFACE HIGH DROPS SOUTH. MAYBE SOME CUMULUS INTO THE AFTERNOON OVER EASTERN AREAS...BUT SHOULD DISSIPATE LATE BY LATE AFTERNOON. KMSP...SOME CLOUDS AROUND WITH FROPA THIS AFTERNOON. MAY LINGER AS CAA STRATOCUMULUS INTO THE EVENING. WILL LEAVE AS SCT FOR NOW. SOME INDICATION OF LOWER MVFR CEILING DEVELOPING...BUT MAINLY TO THE EAST OF THE AREA. STRONG NORTHWEST WINDS WITH FROPA WILL DISSIPATE AFTER SUNSET. LIGHT NORTH WINDS THEN INTO SUNDAY WITH PERHAPS A FEW CUMULUS INTO THE AFTERNOON. /OUTLOOK FOR KMSP/ .MONDAY...VFR. WINDS S 15 TO 20 KTS WITH GUSTS TO 30 KTS. .TUESDAY...VFR. WINDS SSW 15 TO 20 KTS WITH GUSTS TO 25 KTS. .WEDNESDAY...MAINLY VFR WITH A CHC OF SHRA/TSRA. WINDS NW 7 KTS. && .DISCUSSION... /ISSUED 248 AM CDT SAT SEP 8 2012/ A STRONG SHRTWV EARLY THIS MORNING WAS EVIDENT ON THE LATEST WV IMAGERY JUST NORTH OF WINNIPEG. MODELS HAVE SLOWLY COME AROUND TO A MORE SIGNIFICANT SYSTEM AFFECTING THE UPPER MIDWEST STARTING LATE THIS MORNING...AND LASTING THRU EARLY THIS EVENING. TWO FORECAST CONCERNS ARE ASSOCIATED WITH THIS SYSTEM TODAY. ONE IS THE QUICK MOVEMENT WHICH MAY ALLOW FOR TEMPS ACROSS CENTRAL MN TO MAX OUT BY LATE MORNING AS CURRENT TIMING OF THIS SHRTWV HAS IT MOVING INTO KAXN BY 16Z. ALTHOUGH THERE SHOULD BE A FAIR AMT OF SUNSHINE ACROSS WC/CENTRAL MN BEFORE THIS SYSTEM MOVES IN...CLDS SHOULD QUICKLY INCREASE...ESPECIALLY EAST OF AXN WHICH MAY ALLOW FOR TEMPS TO HOLD STEADY OR FALL IN CENTRAL/EC MN DURING THE AFTN. WC MN WILL HAVE LITTLE OR NO CLD CVR ALONG WITH A LONGER TIME FOR HEATING BEFORE THIS FRONT MOVES THRU. SO...WC/SW MN MAY RISE TO NEAR 80 BEFORE LEVELING OFF BY THE EARLY AFTN. ACROSS EC MN AND WI WC...STRONG LIFT AND AMPLE MOISTURE WILL ALLOW FOR SHRA TO DEVELOP...WITH THE BEST COVERAGE IN WC WI WHERE LIKELY POPS SEEM REASONABLE BY 18-21Z. DUE TO THE SPEED OF THIS SYSTEM...THE OPPORTUNITY OF SHRA WILL BE SHORT LIVED AS MOST OF THE LIFT WILL DEPART THE AREA BY 00Z/09. WINDS WILL INCREASE SIGNIFICANTLY BY NOON...WITH GUSTS OVER 30 MPH LIKELY IN WC MN BY NOON. SOME FIRE WEATHER CONCERNS ARE EVIDENT...ESPECIALLY IN WC/SW MN. WILL HIGHLIGHT MORNING HWO ON THIS SCENARIO...AND LET THE DAY SHIFT CALL FIRE WEATHER PERSONAL FOR A POSSIBLE WARNING IF NECESSARY. FIRE WEATHER CONCERNS WILL BE MORE EVIDENT ON MONDAY AS A STRONG SW WIND DEVELOPS ALONG THE LEADING EDGE OF A STRONGER SYSTEM AFFECTING THE UPPER MIDWEST BY TUESDAY AFTN/WED. THERE ARE SEVERAL FACTORS LEADING TO A HIGH FIRE DANGER FOR MONDAY AS THE COMBINATION OF DRY VEGETATION AND STRONG MIXING FROM FULL SUNSHINE LEADING TO STRONG SW WINDS...AND THE ADDED AFFECT OF THE DROUGHT CONDITIONS HAVE WORSEN IN THIS AREA. WILL AGAIN HIGHLIGHT AREAS OF CONCERN IN THE MORNING HWO. THERE IS A SMALL OPPORTUNITY OF SHRA/TSRA WED/WED AFTN IN SC MN AS THE FRONT MAY SLOW ALLOWING FOR DEEPER MOISTURE TO RETURN FOR THE UPPER MIDWEST. AS FOR TEMPS...80S AND A FEW LOW 90S ARE NOT OUT OF THE QUESTION FOR PORTIONS OF THE FA MONDAY AND AGAIN TUE. AFT WED...MORE SEASONABLE TEMPS WILL RETURN WITH A STRONGER SIGNAL OF A STRONG COLD FRONT MOVING THRU THE UPPER MIDWEST AFT THE 15TH OF SEPT. THE LATEST EC/GFS HAVE HINTED OF A LARGE RIDGE DEVELOPING ACROSS THE PACIFIC NW...INTO WESTERN CANADA. THIS RIDGE WILL ALLOW OR CONTRIBUTE TO A LONG WAVE TROUGH DEVELOPING ACROSS CENTRAL CANADA AND INTO THE GREAT LAKES REGION. THIS WILL ALLOW FOR N/NW FLOW TO DEVELOP AND THE POSSIBILITY OF MUCH COLDER AIR MASSES TO FILTER SOUTHWARD INTO THE UPPER MIDWEST. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ JLT/DE
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1047 PM CDT SUN SEP 9 2012 UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE .SHORT TERM...TONIGHT AND MONDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A LARGE HIGH PRESSURE SYSTEM STRETCHING ACROSS THE GREAT PLAINS...AND MOVING EAST INTO THE WESTERN GREAT LAKES. MORNING LOW STRATUS BURNED OFF INTO A CU FIELD WITH HELP FROM MOISTURE FLUXES ADVECTING OFF LAKE SUPERIOR. A FEW SHOWERS EVEN POPPED UP OVER THE U.P...BUT DIDNT HAVE ENOUGH TO MAKE IT INTO IRON MOUNTAIN OR WASHINGTON ISLAND EARLY THIS AFTERNOON. AS A STRONG CANADIAN SURFACE MOVES ACROSS THE AREA...TEMPS AND CLOUD COVER ARE THE MAIN FORECAST CONCERNS. TONIGHT...HIGH PRESSURE WILL BE OVER THE STATE DURING THE EVENING THEN DRIFT TOWARDS THE CENTRAL GREAT LAKES OVERNIGHT. WITH RIDGING THROUGH THE COLUMN...MAY SEE SCT COVERAGE OF LINGERING CU OVER DOOR COUNTY DURING EARLY EVENING...BUT SUBSIDENCE SHOULD WIN OUT FAIRLY QUICKLY WHICH WILL LEAVE CLEAR CONDITIONS THEREAFTER. PWATS WILL FALL BELOW 0.5 INCHES OVERNIGHT AND WINDS WILL BE CALM...AND THAT WILL LEAD TO GOOD RADIATIONAL COOLING CONDITIONS. BIAS CORRECTED GUIDANCE DROPS LOWS INTO THE MID TO UPPER 30S OVER LINCOLN AND NORTHERN VILAS COUNTY...AND WILL MENTION PATCHY FROST IN THE FORECAST. LOWS IN THE 40S OUTSIDE OF THE COLD SPOTS. MONDAY...HIGH PRESSURE WILL BE MOVING TO THE EASTERN GREAT LAKES ON MONDAY AND WILL START OUT THE DAY WEST OF THE 850MB RIDGE AXIS. AS A RESULT...WINDS WILL SHIFT TO THE SOUTHWEST AND WILL SEE A WARMING TREND COMMENCE. THE AIRMASS ADVECTING INTO THE REGION FROM THE GREAT PLAINS IS VERY DRY...SO EXPECT A SEASONABLE AND MOSTLY SUNNY DAY WITH HIGHS IN THE LOW TO MID 70S. .LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY...PRECIPITATION TRENDS FOR THE MID TO LATE PART OF THE UPCOMING WEEK...AND TEMPERATURES... ARE THE MAIN FCST CONCERNS. STRONG RETURN FLOW WILL BE ONGOING AT THE BEGINNING OF THE PERIOD... AHEAD OF AN APPROACHING COLD FRONT. MIN TEMPS WILL BE MILDER ON MONDAY NIGHT...MAINLY IN THE 50S. MIXING THROUGH 900-875 MB ON TUESDAY SHOULD YIELD MAX TEMPS IN THE 80-85 RANGE...WARMEST IN THE SANDY SOIL REGION OF CENTRAL WI. BREEZY CONDITIONS ARE EXPECTED... WITH SW WINDS GUSTING OVER 25 MPH. THE COMBINATION OF WARM TEMPS... GUSTY WINDS AND FAIRLY LOW RELATIVE HUMIDITY (30-35 PERCENT) WILL RESULT IN ELEVATED FIRE DANGER...BUT CONDITIONS DO NOT WARRANT ANY HEADLINE CONSIDERATIONS. THE PREVIOUSLY-MENTIONED COLD FRONT IS EXPECTED TO MOVE INTO FAR NC WI LATE TUESDAY NIGHT. WITH AN INITIAL LACK OF MOISTURE AND THE UPPER LEVEL FORCING LAGGING TO THE WEST...WILL KEEP THE DRY FCST INTACT. MUCH ABOVE NORMAL TEMPERATURES ARE ANTICIPATED... WITH READINGS IN THE 60-65 RANGE. THE COLD FRONT IS EXPECTED TO SHIFT TOWARD THE FOX VALLEY/LKSHR AREAS ON WEDS...WITH POST-FRONTAL SHOWERS DEVELOPING NW OF AN MFI-IMT LINE. SUNSHINE AND COMPRESSIONAL HEATING AHEAD OF THE FRONT SHOULD STILL ALLOW TEMPS TO REACH THE LOWER TO MIDDLE 80S OVER PARTS OF C/NE/EC WI...SO HAVE RAISED MAX TEMPS SEVERAL DEGREES. HAVE INCREASED POPS FOR THE WEDS NGT/THU PERIOD...AS POST- FRONTAL PCPN INCREASES DUE TO AN APPROACHING UPPER TROF...UPPER DIVG IN THE RRQ OF A STRONG JET STREAK...AND MID-LEVEL FRONTOGENETIC FORCING. PCPN CHANCES BECOME LESS CLEAR DURING THE THU NGT-FRI NGT PERIOD...AS THE GFS/GEFS SHOVE THE FRONTAL SYSTEM AND ASSOC PCPN BAND TO OUR EAST...WHILE THE ECMWF STALLS THE FRONT AND LIFTS A SFC WAVE NORTHWARD ALONG THE BOUNDARY... RESULTING IN A RENEWED SWATH OF RAIN ACROSS THE AREA LATE THURSDAY NIGHT INTO FRIDAY NIGHT. DUE TO THE UNCERTAINTY... HAVE KEPT THE TYPICAL MODEL BLEND FOR NOW...WHICH SIDES TOWARD THE DRIER SIDE OF THE SOLUTIONS. ANOTHER WEAK COLD FRONT IS EXPECTED OVER THE WEEKEND...BUT IS NOT EXPECTED TO BE A BIG WEATHER MAKER. AFTER WEDNESDAY...THE INCOMING CANADIAN AIR MASS WILL BRING TEMPERATURES BACK CLOSER TO NORMAL FOR THE MIDDLE OF SEPTEMBER. && .AVIATION...CLEAR SKIES OVERNIGHT AS HIGH PRESSURE MOVES OVER THE FORECAST AREA. SOME PATCHY GROUND FOG ESPECIALLY OVER NORTHCENTRAL AREAS INCLUDING RHI. VFR CONDITIONS MONDAY WITH LIGHT SOUTHWEST WINDS EARLY...THEN INCREASING TO 10 TO 20 MPH ESPECIALLY OVER CENTRAL WISCONSIN DURING THE AFTERNOON. ESB && .MARINE...PERSISTENT AND STRENGTHENING SOUTH TO SOUTHWEST FLOW WILL LEAD TO HAZARDOUS CONDITIONS FOR SMALL CRAFT FROM MONDAY NIGHT THROUGH WEDNESDAY. WILL BE ISSUING SMALL CRAFT ADVISORIES WITH THIS FCST PACKAGE. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
549 PM CDT SAT SEP 8 2012 UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE .SHORT TERM...TONIGHT THROUGH SUNDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A VIGOROUS AND COMPACT SHORTWAVE TROUGH MOVING SOUTHEAST INTO NORTHWEST WISCONSIN EARLY THIS AFTERNOON. LEADING BAND OF SHOWERS IS DIVING ACROSS NORTH-CENTRAL WISCONSIN...WHILE ADDITIONAL SHOWER ACTIVITY EXISTS ACROSS THE ARROWHEAD OF MINNESOTA IN THE WRAP-AROUND REGION OF THE SYSTEM. A REINFORCEMENT OF COOLER AIR IS FOLLOWING IN THE WAKE OF THE SHORTWAVE WHERE 850MB TEMPS ARE FALLING BELOW 4C OVER NORTHERN MINNESOTA AND WESTERN ONTARIO. PRECIP TRENDS ARE THE MAIN FORECAST CONCERN OVER THE NEXT 24 HOURS. TONIGHT...COMPACT YET POTENT SHORTWAVE TROUGH WILL CONTINUE TO DIVE SE AND EXIT THE STATE BY MID-EVENING. LOW LEVEL TROUGH BENEATH PLENTY OF MID-LEVEL MOISTURE WILL KEEP LIKELY TO DEFINITE SHOWERS AROUND OVER CENTRAL AND NORTHEAST WISCONSIN FOR THE FIRST HALF OF THE EVENING. SOME SHOWERS BEHIND THE SYSTEM AS WELL OVER THE ARROWHEAD SO DECIDED TO KEEP A LOW END CHANCE OF SHOWERS OVER N-C WISCONSIN. THEREAFTER...SHOULD SEE SHOWERS EXIT EAST-CENTRAL WISCONSIN BY LATE EVENING WHILE DELTA T/S OVER WESTERN LAKE SUPERIOR INCREASE TO 14-15C IN NORTHERLY FLOW. WITH RICH ENOUGH MOISTURE IN THE 850-700MB LAYER...LAKE EFFECT SHOWERS LOOK TO BE A GOOD BET TO DEVELOP LATER THIS EVENING AND OVERNIGHT. AS A RESULT...CLOUDS WILL BE SLOWER TO DEPART OVER CENTRAL AND NORTH-CENTRAL WISCONSIN THAN FARTHER EAST WHERE MODELS SHOW DRY AIR FROM EASTERN ONTARIO SURGING SOUTH OVER NORTHEAST WISCONSIN. TEMPS FALLING INTO THE 40S NORTHWEST OF THE FOX VALLEY...AND INTO THE LOWER 50S ELSEWHERE. SUNDAY...CANADIAN HIGH PRESSURE WILL BE BUILDING INTO THE STATE THROUGH THE DAY. NORTHERLY FLOW AHEAD OF THE SURFACE HIGH WILL CONTINUE TO SEND LAKE EFFECT CLOUDS AND SPOTTY SHOWERS INTO NORTH-CENTRAL WISCONSIN THROUGH THE MORNING. ELSEWHERE...DIURNAL CU WILL BE BUILDING BY MIDDAY WHICH WILL LEAD TO A PARTLY CLOUDY DAY. HIGHS RANGING FROM THE MID 60S NORTH TO LOW 70S SOUTH. .LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY...TEMPERATURES THROUGHOUT THE PERIOD...AND PCPN CHANCES FOR THE MID TO LATE PART OF THE WORK WEEK...ARE THE MAIN FCST CONCERNS. COOL CANADIAN HIGH PRESSURE WILL RESIDE OVER THE REGION AT THE BEGINNING OF THE PERIOD. COULD SEE SOME PATCHY FROST OVER PARTS OF NORTHERN WI...WITH MIN TEMPS EXPECTED TO DROP INTO THE MID TO UPPER 30S IN THE TYPICAL COLD SPOTS. RETURN FLOW ON THE BACK SIDE OF THE HIGH WILL RESULT IN A WARM-UP ON MONDAY AND TUESDAY...WITH TEMPERATURES RISING TO WELL ABOVE NORMAL LEVELS AGAIN BY TUESDAY. BREEZY CONDITIONS WILL ALSO DEVELOP ON TUESDAY...AS THE PRESSURE GRADIENT STRENGTHENS BETWEEN THE DEPARTING HIGH AND A COLD FRONT MOVG INTO MINNESOTA. THE COLD FRONT WILL EDGE TOWARD NC WI LATE TUESDAY NIGHT...THEN MOVE SLOWLY SE THROUGH THE FORECAST AREA ON WEDS/WEDS NGT/THU. WITH AN UPPER TROF AND THE RRQ OF AN UPPER LEVEL JET LAGGING TO THE WEST OF THE FRONT...PCPN IS EXPECTED TO BE POST-FRONTAL. WILL HAVE CHC POPS OVER NC WI ON WEDS...ACROSS MOST OF THE CWA ON WEDS NGT...AND CONTINUING OVER AT LEAST OUR SE COUNTIES ON THU/THU NGT. THE 12Z ECMWF HAS CAST SOME DOUBT ON THIS SCENARIO...AS IT REDEVELOPS PCPN ACROSS MOST OF WISCONSIN FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT...AS IT LIFTS A SFC WAVE NEWD ALONG THE STALLED FRONTAL BOUNDARY. THIS CANNOT BE RULED OUT...GIVEN THE FAIRLY POTENT UPPER TROF/JET STREAK PREDICTED BY THE MODELS. WILL NEED TO WATCH THE TRENDS ON THIS OVER THE NEXT FEW DAYS. ANOTHER COOLER CANADIAN AIR MASS WILL BUILD INTO THE REGION IN THE WAKE OF THE COLD FRONT...ALLOWING TEMPERATURES TO DROP TO AROUND SEASONAL NORMALS FOR MID-SEPTEMBER. && .AVIATION...AN UPPER LOW WITH SURFACE COLD FRONT WILL DROP OVER EASTERN WISCONSIN THIS EVENING. BANDS OF SHOWERS WITH ISOLATED STORMS WILL PRODUCE SCATTERED MVFR CIGS AND VSBYS MAINLY THIS EVENING. AS THE UPPER LOW DEPARTS TO THE EAST LATER TONIGHT...VFR CONDITIONS TO DOMINATE...WITH THE EXCEPTION OF PATCHY MVFR CIGS OVER FAR NORTH CENTRAL WISCONSIN. DRIER AIR WILL FEED INTO THE STATE SUNDAY TO CONTINUE THE VFR CONDITIONS. TDH && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
239 PM CDT SAT SEP 8 2012 .SHORT TERM...TONIGHT THROUGH SUNDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A VIGOROUS AND COMPACT SHORTWAVE TROUGH MOVING SOUTHEAST INTO NORTHWEST WISCONSIN EARLY THIS AFTERNOON. LEADING BAND OF SHOWERS IS DIVING ACROSS NORTH-CENTRAL WISCONSIN...WHILE ADDITIONAL SHOWER ACTIVITY EXISTS ACROSS THE ARROWHEAD OF MINNESOTA IN THE WRAP-AROUND REGION OF THE SYSTEM. A REINFORCEMENT OF COOLER AIR IS FOLLOWING IN THE WAKE OF THE SHORTWAVE WHERE 850MB TEMPS ARE FALLING BELOW 4C OVER NORTHERN MINNESOTA AND WESTERN ONTARIO. PRECIP TRENDS ARE THE MAIN FORECAST CONCERN OVER THE NEXT 24 HOURS. TONIGHT...COMPACT YET POTENT SHORTWAVE TROUGH WILL CONTINUE TO DIVE SE AND EXIT THE STATE BY MID-EVENING. LOW LEVEL TROUGH BENEATH PLENTY OF MID-LEVEL MOISTURE WILL KEEP LIKELY TO DEFINITE SHOWERS AROUND OVER CENTRAL AND NORTHEAST WISCONSIN FOR THE FIRST HALF OF THE EVENING. SOME SHOWERS BEHIND THE SYSTEM AS WELL OVER THE ARROWHEAD SO DECIDED TO KEEP A LOW END CHANCE OF SHOWERS OVER N-C WISCONSIN. THEREAFTER...SHOULD SEE SHOWERS EXIT EAST-CENTRAL WISCONSIN BY LATE EVENING WHILE DELTA T/S OVER WESTERN LAKE SUPERIOR INCREASE TO 14-15C IN NORTHERLY FLOW. WITH RICH ENOUGH MOISTURE IN THE 850-700MB LAYER...LAKE EFFECT SHOWERS LOOK TO BE A GOOD BET TO DEVELOP LATER THIS EVENING AND OVERNIGHT. AS A RESULT...CLOUDS WILL BE SLOWER TO DEPART OVER CENTRAL AND NORTH-CENTRAL WISCONSIN THAN FARTHER EAST WHERE MODELS SHOW DRY AIR FROM EASTERN ONTARIO SURGING SOUTH OVER NORTHEAST WISCONSIN. TEMPS FALLING INTO THE 40S NORTHWEST OF THE FOX VALLEY...AND INTO THE LOWER 50S ELSEWHERE. SUNDAY...CANADIAN HIGH PRESSURE WILL BE BUILDING INTO THE STATE THROUGH THE DAY. NORTHERLY FLOW AHEAD OF THE SURFACE HIGH WILL CONTINUE TO SEND LAKE EFFECT CLOUDS AND SPOTTY SHOWERS INTO NORTH-CENTRAL WISCONSIN THROUGH THE MORNING. ELSEWHERE...DIURNAL CU WILL BE BUILDING BY MIDDAY WHICH WILL LEAD TO A PARTLY CLOUDY DAY. HIGHS RANGING FROM THE MID 60S NORTH TO LOW 70S SOUTH. .LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY...TEMPERATURES THROUGHOUT THE PERIOD...AND PCPN CHANCES FOR THE MID TO LATE PART OF THE WORK WEEK...ARE THE MAIN FCST CONCERNS. COOL CANADIAN HIGH PRESSURE WILL RESIDE OVER THE REGION AT THE BEGINNING OF THE PERIOD. COULD SEE SOME PATCHY FROST OVER PARTS OF NORTHERN WI...WITH MIN TEMPS EXPECTED TO DROP INTO THE MID TO UPPER 30S IN THE TYPICAL COLD SPOTS. RETURN FLOW ON THE BACK SIDE OF THE HIGH WILL RESULT IN A WARM-UP ON MONDAY AND TUESDAY...WITH TEMPERATURES RISING TO WELL ABOVE NORMAL LEVELS AGAIN BY TUESDAY. BREEZY CONDITIONS WILL ALSO DEVELOP ON TUESDAY...AS THE PRESSURE GRADIENT STRENGTHENS BETWEEN THE DEPARTING HIGH AND A COLD FRONT MOVG INTO MINNESOTA. THE COLD FRONT WILL EDGE TOWARD NC WI LATE TUESDAY NIGHT...THEN MOVE SLOWLY SE THROUGH THE FORECAST AREA ON WEDS/WEDS NGT/THU. WITH AN UPPER TROF AND THE RRQ OF AN UPPER LEVEL JET LAGGING TO THE WEST OF THE FRONT...PCPN IS EXPECTED TO BE POST-FRONTAL. WILL HAVE CHC POPS OVER NC WI ON WEDS...ACROSS MOST OF THE CWA ON WEDS NGT...AND CONTINUING OVER AT LEAST OUR SE COUNTIES ON THU/THU NGT. THE 12Z ECMWF HAS CAST SOME DOUBT ON THIS SCENARIO...AS IT REDEVELOPS PCPN ACROSS MOST OF WISCONSIN FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT...AS IT LIFTS A SFC WAVE NEWD ALONG THE STALLED FRONTAL BOUNDARY. THIS CANNOT BE RULED OUT...GIVEN THE FAIRLY POTENT UPPER TROF/JET STREAK PREDICTED BY THE MODELS. WILL NEED TO WATCH THE TRENDS ON THIS OVER THE NEXT FEW DAYS. ANOTHER COOLER CANADIAN AIR MASS WILL BUILD INTO THE REGION IN THE WAKE OF THE COLD FRONT...ALLOWING TEMPERATURES TO DROP TO AROUND SEASONAL NORMALS FOR MID-SEPTEMBER. && .AVIATION...A COMPACT BUT DYNAMIC UPPER LEVEL DISTURBANCE WILL DROP SOUTH ACROSS THE REGION THIS AFTERNOON. LIGHT TO MODERATE SHOWERS WILL MOVE SOUTH-SOUTHEAST AHEAD OF THIS DISTURBANCE EARLY TO MID-AFTERNOON OVER NORTH-CENTRAL AND CENTRAL WISCONSIN...AND MID TO LATE AFTERNOON OVER NORTHEAST WISCONSIN AND THE FOX VALLEY. NOT OUT OF THE QUESTION THAT COULD ALSO SEE A RUMBLE OF THUNDER AND MVFR CIGS/VSBYS WITHIN THE HEAVIER SHOWERS. THE SHOWERS WILL BE DEPARTING EARLY THIS EVENING BUT THINK SOME MVFR CIGS WILL STICK AROUND FOR PARTS OF THE EVENING. EVENTUALLY THOUGH...MODELS PROJECT DRIER AIR ARRIVING LATE THIS EVENING ONWARD FROM THE NORTH THAT WILL ERODE ANY LOW CLOUD COVER...EXCEPT OVER FAR NORTH-CENTRAL WISCONSIN WHERE SCT LAKE EFFECT RAIN SHOWERS MAY OCCUR. THEREAFTER...LOOK FOR SCT TO BKN CU TO DEVELOP BY LATE MORNING TOMORROW WITH DAYTIME HEATING. MPC && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ MPC/KIECKBUSCH
AREA FORECAST DISCUSSION
NWS BILLINGS MT
334 AM MDT MON SEP 10 2012 .SHORT TERM...VALID FOR TDY AND TUE... CRITICAL FIRE WEATHER CONDITIONS WILL BE THE MAIN MESSAGE FOR THIS AFTERNOON THROUGH TONIGHT WHILE A 500-HPA SHORT WAVE TROUGH SHIFTS EAST AND DEEPENS OVER CENTRAL CANADA. WE HAVE HIGH CONFIDENCE THAT RED FLAG CRITERIA WILL BE MET THIS AFTERNOON INTO TONIGHT. THAT IS NOT TRUE FOR TUE...WHEN CONFIDENCE IN RED FLAG CONDITIONS ACROSS A WIDESPREAD AREA IS ACTUALLY DECREASING SUBSTANTIALLY WITH TIME. EARLY THIS MORNING...A LEAD AND RELATIVELY WEAK 500-HPA SHORT WAVE IS CROSSING THE AREA...AND GENERATING A BIT OF CONVECTION IN SOUTH CENTRAL MT AROUND LIVINGSTON. THE 06 UTC NAM AND 05 UTC HRRR WOULD SUGGEST THIS ACTIVITY WILL WANE BY ABOUT 12 UTC...BUT THE SCENARIO DOES WARRANT SOME LOW POPS FOR A FEW PLACES IN SOUTH CENTRAL MT IN THE 12 TO 15 UTC TIME FRAME BASED ON RECENT RADAR TRENDS. TODAY...PRE-FRONTAL MIXING WILL EXTEND TO AROUND 600 HPA OVER MUCH OF SOUTH CENTRAL MT BASED ON A CONSENSUS OF FORECAST SOUNDINGS. IT LOOKS LIKE GUSTS OF 30 MPH WILL BE COMMON...WITH SOME 40 MPH GUSTS VERY PLAUSIBLE FOR PLACES LIKE LIVINGSTON SINCE BUFKIT-BASED TOOLS REVEAL SUBSIDENCE THROUGH THE DEPTH OF THE MIXED LAYER...WITH SOME 35 KT WINDS AT ITS TOP. ONE EXCEPTION TO ALL OF THIS COULD BE OVER SOUTHEASTERN MT...WHERE WINDS ALOFT DO NOT INCREASE UNTIL CLOSE TO 00 UTC. THE EXPECTED MIXING SUPPORTS HIGHS NEAR 90 F IN MANY SPOTS TODAY...THOUGH BASED ON A BIT OF COOLING ALOFT EARLY TODAY...HIGHS WERE ACTUALLY LOWERED A BIT OVER PREVIOUS FORECASTS FOR AREAS LIKE LIVINGSTON AND HARLOWTON. THAT IS IN LINE WITH THE SET OF MOS FROM THE 00 UTC GUIDANCE. FINALLY...WE HAVE SOME LOW POPS IN PLACE THIS AFTERNOON FROM THE BIG HORN MOUNTAINS NORTHEAST INTO FAR SOUTHEAST MT BASED ON THE FACT THAT THE LAST SEVERAL MODEL CYCLES HAVE SHOWN HIGH-BASED CONVECTION IN THOSE AREAS. CALIBRATED PROBABILITIES FOR DRY THUNDERSTORMS FROM THE 21 UTC SREF ARE EVEN NEAR 10 PERCENT IN THAT REGION...SO WE WILL INCLUDE A MENTION OF THE POTENTIAL WITHIN OUR RED FLAG WARNING. TONIGHT...THE SURFACE COLD FRONTAL PASSAGE IS EXPECTED TO OCCUR IN THE 00 TO 06 UTC TIME FRAME. SURFACE PRESSURE RISES WILL BE IN THE 5 HPA/3 HOUR RANGE BASED ON THE 00 UTC NAM AND GFS...AND 500 M AGL WINDS WILL CLOSE IN ON 30 KT. THUS...WE STILL EXPECT A PERIOD WITH WIND GUSTS OF 35 MPH...THOUGH WE HAVE TO ADMIT THAT SOUNDINGS FROM THE 00 UTC GUIDANCE LEAVE A BIT TO BE DESIRED SINCE THEY ALLOW FOR THE BOUNDARY LAYER TO STABILIZE ENOUGH TO REDUCE MOMENTUM TRANSFER BEHIND THE FRONT. THUS...THERE IS A BIT OF UNCERTAINTY WITH REGARD TO HOW LONG WINDS WILL STAY UP BEHIND THE FRONT. TUE...FORECAST SOUNDINGS SUGGEST THAT BOUNDARY LAYER MIXING SHOULD ONLY EXTEND TO ABOUT 750 HPA...AND IT IS ONLY ABOVE THAT LEVEL THE MID-LEVEL WINDS WILL BE SIGNIFICANT. THIS BRINGS INTO QUESTION THE POTENTIAL FOR GUSTY SURFACE WINDS OUTSIDE OF SOUTHEASTERN MT...AND ADDING TO THAT UNCERTAINTY ARE THE SURFACE PRESSURE FALLS SHOWN IN SOUTH CENTRAL MT BY AFTERNOON. SOMETIMES TURBULENT MIXING BEHIND A COLD FRONT AND SHORT WAVE IS MORE ROBUST THAN MODELS SUGGEST...AND SO WE MADE FEW CHANGES TO THE CURRENT FORECAST. HOWEVER...THERE IS A CHANCE THAT THE BAKER AND MILES CITY AREAS WILL BE THE ONLY ONES WITH GUSTY WINDS REQUIRING A RED FLAG ON TUE SINCE THOSE SPOTS ARE IN CLOSER PROXIMITY TO STRONGER FLOW BELOW 750 HPA. SCHULTZ .LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN... MODEL AGREEMENT IS NOT AS GOOD TONIGHT AS DURING PREVIOUS RUNS. BROAD UPPER LEVEL TROUGH CONTINUES ACROSS THE REGION WED...WITH REINFORCING FRONT ON WED AFTN/EVE. ECMWF BRINGS THE SHORTWAVE SUPPORT FOR THE REINFORCING FRONT THROUGH IN THE FORM OF TWO SEPARATE WAVES...WHILE THE GFS BRINGS IT THROUGH AS ONE STRONG...COHERENT SHORTWAVE. A BLEND OF LONG RANGE MODELS SEEMS TO BE THE BEST SOLUTION FOR WED...AND FOR MUCH OF THE EXTENDED AT THIS POINT. SO...DID NOT REALLY CHANGE MUCH WED-THURS. UPPER TROUGH IS SLOW TO MOVE THROUGH...KEEPING COOL DRY AIR ADVECTION IN PLACE THROUGH THURS. AN UPPER RIDGE BUILDS INTO THE REGION LATE THURS AND WILL DOMINATE THE PATTERN FOR FRI...IN RESPONSE TO TROUGHING BUILDING UPSTREAM. TEMPS SHOULD RETURN TO ABOVE NORMAL LEVELS ON FRI AND SAT. MODELS HANDLE THE REMAINDER OF THE PERIOD QUITE DIFFERENTLY. AT SOME POINT LATE IN THE WEEKEND OR EARLY NEXT WEEK IT LOOKS LIKE ANOTHER COOLDOWN WILL BEGIN...BUT CANNOT REALLY DETERMINE EXACTLY WHEN THIS WILL BE AS MODEL CONSISTENCY IS POOR DURING THIS TIMEFRAME. PREVIOUS MODEL RUNS HAD THIS COOLDOWN BEGINNING SAT/SAT NIGHT...SO IT APPEARS MODELS ARE HAVING A VERY HARD TIME FORECASTING THE TIMING OF THIS FEATURE. INTRODUCED SLIGHT CHANCE POPS OVER THE MOUNTAINS SUNDAY AS THE ECMWF HAS GONE TO A SOLUTION THAT SLIDES AN UPPER LEVEL LOW SOUTHWARD THROUGH WESTERN MT/IDAHO. STILL...NOT REALLY BUYING THAT AS IT REPRESENTS A TREMENDOUS DEPARTURE FROM MODELS RUNS OVER THE LAST COUPLE OF DAYS. BOTTOM LINE IS...COOL WEATHER WED INTO THURS...A WARMUP FRI INTO SAT...THEN ANOTHER COOLDOWN PROBABLY BEGINNING SUN....WITH NO PRECIP EXPECTED THROUGH AT LEAST SAT NIGHT. STC && .AVIATION... MAINLY VFR CONDITIONS WILL PREVAIL ACROSS THE AREA THROUGH TONIGHT. A WEAK DISTURBANCE WILL GENERATE ISOLATED SHOWERS AND THUNDERSTORMS ACROSS WESTERN AND CENTRAL ROUTES OVER THE NEXT FEW HOURS...BUT NOT EXPECTING ANY MVFR OR IFR WITH THE STORMS. THE MAIN AVIATION HAZARD THROUGH THE PERIOD WILL BE WIND. WESTERLY WINDS WILL BECOME GUSTIER ACROSS THE REGION BY EARLY THIS AFTERNOON AHEAD OF A COLD FRONT. THE COLD FRONT WILL RACE THROUGH THE REGION FROM MID AFTERNOON THROUGH THIS EVENING...SWITCHING WINDS TO A NW DIRECTION WITH GUSTS OVER 30 KTS POSSIBLE. A FEW SHOWERS AND THUNDERSTORMS ARE ALSO POSSIBLE ACROSS EASTERN ROUTES DURING THE LATE AFTERNOON AND EVENING HOURS...JUST AHEAD OF THE COLD FRONT. STC && .PRELIMINARY POINT TEMP/POPS... TDY TUE WED THU FRI SAT SUN ------------------------------------------------------- BIL 090 051/071 042/067 039/069 044/082 052/079 051/073 2/T 10/U 00/U 00/U 00/U 11/U 11/U LVM 085 040/071 033/066 031/069 037/079 043/077 040/071 2/T 10/U 01/U 10/U 00/U 10/U 01/U HDN 093 051/073 042/070 040/071 042/083 050/082 050/075 1/N 20/U 00/U 00/U 00/U 11/U 11/U MLS 090 052/072 041/069 038/069 043/080 050/080 053/072 1/U 20/N 00/U 00/U 00/U 00/U 01/B 4BQ 093 053/072 042/070 040/069 044/081 049/082 051/075 2/T 20/N 00/U 00/U 00/U 00/U 01/U BHK 089 052/071 041/068 038/066 043/078 048/079 049/071 1/U 20/N 00/U 10/U 00/U 00/U 01/U SHR 091 048/072 039/066 038/067 041/079 046/079 048/072 2/T 20/U 00/U 00/U 00/U 01/U 11/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...RED FLAG WARNING IN EFFECT UNTIL MIDNIGHT MDT TONIGHT FOR ZONE 117. RED FLAG WARNING IN EFFECT UNTIL MIDNIGHT MDT TUESDAY NIGHT FOR ZONES 123>128-133. RED FLAG WARNING IN EFFECT FROM NOON TODAY TO MIDNIGHT MDT TUESDAY NIGHT FOR ZONES 129>132. WY...RED FLAG WARNING IN EFFECT FROM NOON TODAY TO MIDNIGHT MDT TUESDAY NIGHT FOR ZONES 274-284. && $$ WEATHER.GOV/BILLINGS
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AREA FORECAST DISCUSSION
NWS LA CROSSE WI
311 AM CDT MON SEP 10 2012 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT 311 AM CDT MON SEP 10 2012 MAIN FORECAST CONCERNS ARE ON THE WARMTH TODAY AND TUESDAY...THEN WHEN PRECIPITATION ARRIVES FOR WEDNESDAY INTO WEDNESDAY NIGHT. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS SHOWED TROUGHING COMING INTO BRITISH COLUMBIA AND THE PACIFIC NORTHWEST...RIDGING ACROSS MUCH OF THE PLAINS INTO MANITOBA...AND TROUGHING ALONG THE EAST COAST. SOME CIRRUS NOTED SPILLING OVER TOP OF THE RIDGE INTO NORTHERN MINNESOTA. OTHERWISE...PLENTY OF SUBSIDENCE UNDER THE UPPER RIDGE AS WELL AS DRY AIR RESULTING IN CLEAR SKIES FROM THE CENTRAL PLAINS INTO THE FORECAST AREA. REGARDING THE DRY AIR...GOES SOUNDER PRECIPITABLE WATER IMAGERY SHOWED VALUES OF 0.3 TO 0.5 INCHES WHERE THE CLEAR SKIES ARE...OR AROUND 50 PERCENT OF NORMAL. AT THE SURFACE...HIGH PRESSURE STRETCHED FROM MISSOURI INTO LOWER MICHIGAN AND LEE TROUGHING WAS PRESENT ALONG THE EAST SIDE OF THE ROCKIES. SOUTHERLY WINDS WERE INCREASING OVER THE PLAINS INTO MINNESOTA...BOTH AT THE SURFACE AND ALOFT. AT 850MB...PROFILER DATA SHOWED 40-50 KT SOUTHWEST WINDS ACROSS THE DAKOTAS. THESE WINDS DOWNSLOPING OFF THE ROCKIES ARE PRODUCING 22-27C 850MB TEMPS OVER THE DAKOTAS PER RAP ANALYSIS. OVER THE FORECAST AREA...LIGHTER WINDS ASSOCIATED WITH THE SURFACE HIGH ALLOWING THE TYPICAL COLD SPOTS TO DROP INTO THE UPPER 30S. ANY VALLEY FOG THUS FAR HAS BEEN CONFINED TO THE WISCONSIN RIVER VALLEY...AND EVEN THAT HAS NOT CONSISTENTLY STAYED IN PLACE. TODAY THROUGH TUESDAY...MODELS ARE IN GOOD AGREEMENT SHOWING THE UPPER TROUGHING COMING INTO BRITISH COLUMBIA DEEPENING AND SHIFTING EAST TO SASKATCHEWAN BY 00Z WEDNESDAY. AS THIS OCCURS...THE UPPER RIDGING OVER THE PLAINS GETS PUSHED EAST ACROSS THE FORECAST AREA. IN ADDITION...THE LEE TROUGHING TURNS INTO A COLD FRONT AND REACHES THE SIOUX FALLS AREA BY 00Z WEDNESDAY. THE HEAT BUILDING UP ACROSS THE DAKOTAS AND THE STRENGTHENING WINDS WILL ACCOMPANY THE EASTWARD PROGRESS OF THE UPPER RIDGE. 850MB TEMPS AT 12Z THIS MORNING SHOULD RANGE FROM 9-12C EAST TO WEST. BY 00Z THIS EVENING...THEY ARE PROGGED TO CLIMB TO AT LEAST 14-17C IF NOT A LITTLE WARMER. WITH INCREASING SOUTHERLY WINDS...DRY AIR AND PLENTY OF SUN OUTSIDE OF MAYBE SOME CIRRUS...WE SHOULD HAVE NO PROBLEM MIXING TO 850MB. GOING HIGHS OF MIDDLE 70S TO LOWER 80S REFLECT THIS WELL. A SOUTHERLY BREEZE WILL HELP TO KEEP LOW TEMPERATURES IN THE 50S TONIGHT. FURTHER WARMING CONTINUES INTO TUESDAY WITH 850MB TEMPS REACHING 20-22C BY 18Z...OR 1.5-2 STANDARD DEVIATIONS ABOVE NORMAL. THERE ARE INDICATIONS OF INCREASE CIRRUS DURING THE AFTERNOON...BUT MOST OF THE DAY SHOULD SEE PLENTY OF SUN. WINDS WILL BE STRONGER... WITH SOUTHWEST SPEEDS OF 25 KT AT 925MB AND 35KT AT 850MB. THE COMBINATION OF THESE WINDS...STILL PLENTY OF DRY AIR AND THE SUN SHOULD PROPEL TEMPERATURES UP INTO THE MIDDLE 80S TO AROUND 90. WITH THE WARM...DRY AIR AND INCREASING WINDS...THERE ARE SOME FIRE WEATHER CONCERNS WHICH ARE DISCUSSED IN THE FIRE WEATHER AFD SECTION. TUESDAY NIGHT AND WEDNESDAY...UPPER RIDGING IS PROGGED TO STRENGTHEN ACROSS THE OHIO VALLEY INTO THE EASTERN GREAT LAKES REGION DURING THIS TIME. THIS IN TURN HELPS TO HOLD THE FORECAST AREA UNDER SOUTHWEST FLOW ALOFT. WITH THE COLD FRONT THAT REACHED SIOUX FALLS AT 00Z WEDNESDAY HAVING A NEAR SOUTHWEST TO NORTHEAST ORIENTATION... CLOSE TO PARALLELING THE UPPER FLOW...THE SLOW EASTWARD PROGRESS MODELS HAVE TRENDED TO THE PAST FEW DAYS MAKES SENSE. LOOKS LIKE THE COLD FRONT MAY REACH ROCHESTER AROUND 12Z WEDNESDAY...THEN SLOWLY CROSS THE FORECAST AREA BY 00Z THURSDAY. NO CONCERN EXISTS ABOUT THE FRONT INITIATING PRECIPITATION AHEAD OF IT...DUE TO A DRY CAPPED AIRMASS IN PLACE. HOWEVER...BEHIND THE FRONT THINGS ARE MORE INTERESTING. FIRST IN THE 500MB PATTERN...MODELS SHOW A POTENT SHORTWAVE DROPPING DOWN THE BACK SIDE OF THE DEEP SOUTH CENTRAL CANADA TROUGH...REACHING EASTERN MONTANA LATE WEDNESDAY. AN 80-120 KT JET AT THE TROPOPAUSE IS PROGGED TO DEVELOP AHEAD OF THIS POTENT SHORTWAVE INTO NORTHERN MINNESOTA AND ONTARIO. THIS PLACES SOUTHERN MINNESOTA INTO NORTHWEST WISCONSIN UNDER UPPER LEVEL DIVERGENCE. ALSO IN THE 500MB PATTERN THERE IS AN UPPER LOW CURRENTLY NEAR BAJA CALIFORNIA WHICH MODELS SHEAR APART AND LIFT INTO SOUTHERN MINNESOTA BY 00Z THURSDAY. THIS FEATURE WILL HELP PRODUCE SOME DPVA. LASTLY... ON THE BACK/NORTHWEST SIDE OF THE FRONT...LOW TO MID LEVEL FRONTOGENESIS IS PROGGED TO INCREASE THROUGH THE DAY WEDNESDAY. SO PLENTY OF FORCING EXISTS BEHIND THE FRONT TO PRODUCE PRECIPITATION. THIS LEAVES MOISTURE THE ONLY ISSUE...WHICH DOES NOT LOOK TO BE A PROBLEM AS PRECIPITABLE WATER VALUES CLIMB TO 1.5 INCHES BEHIND THE FRONT. THEREFORE...PRECIPITATION DEVELOPMENT BEHIND THE FRONT WILL OCCUR. THERE IS A SHOT SOME OF THIS COULD GET INTO NORTHWESTERN PORTIONS OF THE FORECAST AREA PER THE 10.00Z GFS...BUT OVERALL MODEL CONSENSUS KEEPS THE BULK OF IT NORTH AND WEST OF THE AREA ON WEDNESDAY. REGARDING TEMPERATURES...WITH THE WARM AIRMASS IN PLACE AND A SOUTHERLY BREEZE PERSISTING...TUESDAY NIGHT SHOULD SEE LOWS FROM THE MIDDLE 50S TO MIDDLE 60S. 850MB TEMPS ARE A LITTLE COOLER ON WEDNESDAY...14-18C...BUT SUN THROUGH CIRRUS ALONG/AHEAD OF THE FRONT SHOULD BRING HIGHS UP INTO THE LOW TO MID 80S. BEHIND THE FRONTAL PASSAGE...INCREASING MID/HIGH CLOUDS AND POSSIBLE PRECIPITATION WILL RESULT IN SLIGHTLY COOLER CONDITIONS. WEDNESDAY NIGHT...GOOD CONSENSUS EXISTS FOR THIS PERIOD TO BE WET... ESPECIALLY FOR THE NORTHWEST HALF OF THE FORECAST AREA. UPPER LEVEL DIVERGENCE WILL SHIFT OVER THE FORECAST AREA...ALONG WITH THE LOW TO MID LEVEL FRONTOGENESIS. THIS IS ALL RELATED TO THE DEEP SOUTH CENTRAL CANADA TROUGH LIFTING OUT TO THE NORTHEAST...AND THE POTENT SHORTWAVE IN MONTANA SHIFTING INTO THE DAKOTAS AND CLOSING OFF INTO AN UPPER LOW. AGAIN...PLENTY OF MOISTURE EXISTS WITH PRECIPITABLE WATER VALUES UP AROUND 1.5 INCHES OR 160 PERCENT OF NORMAL. GIVEN THE EXCELLENT CONTINUITY AND CONSENSUS FOR PRECIPITATION IN THE NORTHWEST HALF OF THE FORECAST AREA...HAVE RAISED PRECIPITATION CHANCES THERE TO 80 OR HIGHER. SOME NEGATIVE EPV NOTED IN CROSS SECTIONS THAT GETS INGESTED INTO THE FRONTOGENESIS CIRCULATION. THIS NEGATIVE EPV SHOULD PRODUCE CONVECTIVE BANDING AND SOME ISOLATED THUNDERSTORMS...DESPITE THE LACK OF ANY CAPE. WITH THE CONVECTIVE NATURE AND HIGH PRECIPITABLE WATER...THE QPF AMOUNTS IN THE 10.00Z GFS/NAM OF UPWARDS OF 1 INCH IN 6 HOURS IS CERTAINLY POSSIBLE. COMBINATION OF GRADUAL COLD ADVECTION BEHIND THE FRONT ALONG WITH PRECIPITATION WILL RESULT IN COOLER TEMPERATURES COMPARED TO TUESDAY NIGHT. FOLLOWED A BLEND OF GUIDANCE FOR LOWS. .LONG TERM...THURSDAY THROUGH SUNDAY NIGHT 311 AM CDT MON SEP 10 2012 10.00Z ECMWF/GFS/GFS ENSEMBLES ARE IN GOOD AGREEMENT THROUGH ABOUT FRIDAY...THEN DIFFERENCES BEGIN TO SHOW UP. THE 10.00Z CANADIAN IS A FAST OUTLIER TO START OFF WITH AS IT DOES NOT HAVE THE POTENT SHORTWAVE OVER THE WESTERN DAKOTAS AT 12Z THURSDAY LIKE OTHER MODELS. AS SUCH...THIS MODEL WAS FOR THE MOST PART DISCOUNTED. GENERAL THEME FROM THE ECMWF/GFS/GFS ENSEMBLES IS THAT THE POTENT SHORTWAVE OVER THE WESTERN DAKOTAS WILL COME CLOSE TO OR ACROSS THE FORECAST AREA ON FRIDAY AS A CLOSED OFF UPPER LOW. ALL FORCING FOR PRECIPITATION LOOKS TO REMAIN TO THE EAST OF THE UPPER LOW...WHERE THE FRONTOGENESIS IS OCCURRING. ON THURSDAY...HIGH CONFIDENCE EXISTS THAT THE SOUTHEASTERN HALF OF THE FORECAST AREA WILL SEE RAIN...AS THE FRONTOGENESIS FROM WEDNESDAY NIGHT PUSHES EAST. RAISED PRECIPITATION CHANCES IN THIS AREA TO 70. PRECIPITATION CHANCES THEN LOWER THROUGH FRIDAY...BUT DONT COMPLETELY GO AWAY DUE TO THE UPPER LOW NEARBY. TEMPERATURES WILL DEFINITELY BE COOLER. HOW COOL DEPENDS ON EXACTLY WHERE THE RAIN SETS UP. IT IS POSSIBLE THAT HIGHS ON THURSDAY COULD GET STUCK IN THE 50S WHERE IT RAINS...VERSUS MID 60S TO AROUND 70 WHERE IT DOESNT. COOL AIR ASSOCIATED WITH THE UPPER LOW SHOULD HOLD HIGHS DOWN IN THE MID 60S FOR FRIDAY. BEYOND FRIDAY...THE FORECAST PRETTY MUCH REVOLVES AROUND THE UPPER LOW. OVER THE PAST 24 HOURS OR SO...HAVE SEEN VARIOUS GFS AND ECMWF MODEL RUNS HANDLE THE UPPER LOW DIFFERENTLY. EVEN WITH THE 10.00Z RUNS...THE ECMWF TAKES IT SLOWLY EAST ACROSS IOWA AND ILLINOIS FROM FRIDAY INTO SATURDAY WHILE THE GFS HAS IT HEADING UP INTO EASTERN ONTARIO. THE 09.06Z GFS RUN HAD THE UPPER LOW ON SATURDAY STILL OVER THE FORECAST AREA. AS SUCH...FORECAST CONFIDENCE BEYOND FRIDAY IS LOW. GENERAL THEME...THOUGH...IS ANY RAIN SHOULD FOR THE MOST PART BE EAST OF THE FORECAST AREA...WHICH IS WHAT THE CONSENSUS APPROACH GIVES. BY THE TIME WE APPROACH SUNDAY...THERE ARE INDICATIONS OF A DEEPENING CENTRAL CANADA TROUGH INTO THE NORTHERN ROCKIES. IF THIS DOES OCCUR AS FORECAST...WE SHOULD SEE A WARM UP AS SOUTHERLY FLOW PICKS UP AHEAD OF THE TROUGHING. THE TEMPERATURE FORECAST PLAYS THIS IDEA WITH HIGHS CLIMBING BACK INTO THE LOW TO MID 70S FOR SUNDAY. && .AVIATION... 1145 PM CDT SUN SEP 9 2012 A DIFFICULT CHALLENGE WITH WHAT TO DO WITH POSSIBLE FOG IN THE RIVER VALLEY AT KLSE. 7 DEGREE T/TD SPREAD AT 03Z GENERALLY FAVORS DENSE FOG...AS DOES THE CLEAR SKIES AND LIGHT SFC-NEAR SFC WINDS. MODELS CONTINUE TO POINT TO AN INCREASE IN WINDS ABOVE THE INVERSION BY 09Z...A CONSISTENT SIGNAL OVER THE PAST COUPLE DAYS. NOT CONVINCED THIS IS SUPPORTED BY THE SYNOPTIC SETUP. EVEN IF THESE STRONGER WINDS ARE REALIZED...THE INVERSION IS IN PLACE AND DON/T BELIEVE IT WOULD HAVE AN IMPACT ON THE FG POTENTIAL. MEANWHILE TDS ONLY RECOVERED 3 F THIS EVENING. A 5 TO 7 DEGREE REBOUND WOULD HAVE INCREASED CONFIDENCE FOR 1/4SM FG. NAM12/RAP BUFKIT SOUNDINGS REMAIN POOR WITH TDS...RAP STILL TOO MOIST AND NAM12 TOO DRY AT 03Z. BOTH KEEP AT LEAST A 1 DEGREE T/TD SPREAD THROUGH 12Z. IN ADDITION...THE SOUNDINGS GO FROM SUBSIDENT TO SOME LIGHT UPWARD MOTION AFTER 09Z. SUBSIDENCE ALL NIGHT WOULD FAVOR FOG. WILL CONTINUE WITH THE BCFG FOR NOW. CONFIDENCE JUST SHAKY ENOUGH TO HOLD OFF ON ADDING PREVAILING SUB 1SM AT THE MOMENT. CONDITIONS WILL HAVE TO BE MONITORED VERY CLOSELY THROUGH DAYBREAK AND UPDATES MADE AS NEEDED. THREAT IS STILL THERE FOR 1/4SM FG. HIGH PRESSURE SHIFTS EAST ON MONDAY...WITH A TIGHT PRESSURE GRADIENT RESULTING IN A BREEZY SOUTHERLY FLOW. SOME AFTERNOON MIXING SHOULD RESULT IN GUSTS UP TO 30 MPH AT KRST. && .CLIMATE...TUESDAY 340 PM CDT SUN SEP 9 2012 HIGH TEMPERATURES WILL CLIMB TO AROUND 90 DEGREES MAINLY NORTHWEST OF A CHARLES CITY IOWA TO BLACK RIVER FALLS LINE ON TUESDAY. THE RECORD HIGHS FOR THIS DATE ARE... LA CROSSE WI - 97 IN 1897 MEDFORD WI - 95 IN 1900 ROCHESTER MN - 94 IN 1931 AUSTIN MN - 92 IN 1948 CHARLES CITY IA - 96 IN 2000 DECORAH IA - 97 IN 1895 && .FIRE WEATHER...TODAY AND TUESDAY 311 AM CDT MON SEP 10 2012 INCREASING SOUTH TO SOUTHWEST WINDS TODAY AND TUESDAY WILL BRING WARMER AIR INTO THE REGION. SPEEDS ON THESE WINDS LOOK TO RANGE FROM 15 TO 25 MPH WITH GUSTS UP TO 35 MPH. WITH PLENTY OF SUNSHINE...GOOD MIXING WILL OCCUR...BRINGING TEMPERATURES UP TO 75 TO 80 TODAY AND 85 TO 90 ON TUESDAY. DEWPOINTS ARE A LITTLE TRICKY...SINCE THE WIND DIRECTION FAVORS A RETURN FLOW OF MOISTURE. HOWEVER...THE GULF OF MEXICO DOES NOT OPEN UP FOR THE RETURN OF MOISTURE UNTIL AT LEAST LATE TUESDAY. THEREFORE...DEWPOINTS WILL TAKE THEIR TIME COMING UP...BEING COUNTERED DURING THE AFTERNOONS DUE TO MIXING. CURRENT THINKING IS THAT RELATIVE HUMIDITIES ARE GOING TO END UP IN THE 25 TO 35 PERCENT RANGE...LOWEST IN WESTERN PORTIONS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA. WITH THE DRYING LANDSCAPE/MATURING VEGETATION AND THE ABOVE WEATHER CONDITIONS...CONCERN IS THERE FOR SOME FIRES. HOWEVER...THE RELATIVE HUMIDITIES ARE JUST ABOVE THE CRITICAL 25 PERCENT THRESHOLD NEEDED FOR A FIRE WEATHER RELATED HAZARD. IN ADDITION...FIRE WEATHER USERS AFFECTED IN OUR FORECAST AREA ARE ALRIGHT WITHOUT ANY FIRE WEATHER RELATED HAZARD AT THIS TIME. && .ARX WATCHES/WARNINGS/ADVISORIES... 311 AM CDT MON SEP 10 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM...AJ AVIATION.......RIECK CLIMATE........BOYNE FIRE WEATHER...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS PHOENIX AZ
502 AM MST MON SEP 10 2012 .UPDATE...UPDATED AVIATION DISCUSSION... && .SYNOPSIS... A WEAK UPPER LOW WILL INTERACT WITH A MOIST AIRMASS OVER ARIZONA AND SOUTHEAST CALIFORNIA...LEADING TO ABOVE AVERAGE STORM CHANCES THROUGH TUESDAY. THERE WILL BE LARGE VARIATIONS IN STORM COVERAGE AND INTENSITY FROM DAY TO DAY...WITH STORMS LIKELY TODAY AND TUESDAY OVER SOUTH-CENTRAL ARIZONA. HIGH TEMPERATURES WILL BE BELOW NORMAL THROUGH THURSDAY. DRY AIR MOVES IN DURING THE LATTER HALF OF THE WEEK WITH STORM CHANCES ENDING OVER SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA WEDNESDAY...AND OVER SOUTH-CENTRAL ARIZONA BY FRIDAY. A GRADUAL WARMING TREND WILL ACCOMPANY THE DRIER AIR. && .DISCUSSION... TODAY THROUGH WEDNESDAY...A BATCH OF SHOWERS AND THUNDERSTORMS DEVELOPED OVER SANTA CRUZ COUNTY BEFORE MIDNIGHT AND HAS WORKED ITS WAY INTO NORTHWEST PINAL AND EASTERN MARICOPA COUNTIES...BUT IN A WEAKENED STATE. THE SHOWERS APPEAR TO BE BE ASSOCIATED WITH A CIRCULATION EVIDENT IN THE WATER VAPOR IMAGERY CENTERED SOUTH-SOUTHWEST OF NOGALES. THE RUC PICKED UP ON THIS VORT MAX BUT DID NOT PLACE THE PRECIP CORRECTLY. THE 00Z NAM AND GFS DIDNT PICK UP ON IT THOUGH THE 06Z VERSIONS NOW HINT AT SOMETHING. MEANWHILE...THE UPPER LOW IS CENTERED OVER FAR NORTHERN BAJA. THE LATEST OPERATIONAL MODELS DEPICT THE MAIN AREAS OF VORTICITY CLOSER TO THE LOW CENTER AS WOULD BE EXPECTED. THE OMEGA AND UPPER LEVEL DIVERGENCE FIELDS DIFFER CONSIDERABLY THOUGH WITH THE GFS PRODUCING ITS TYPICAL SPORADIC BULLSEYES AND ASSOCIATED QPF MAXIMA. AS USUAL...THERE ARE TREMENDOUS DIFFERENCES IN THE MODEL QPF WITH THE NAM CHARACTERISTICALLY ON THE LOW SIDE...THOUGH NOT AS LOW AS THE NMM6KM. THE NAM/GFS/SREF BASED POPS ALL CONTINUE TO DEPICT WELL ABOVE NORMAL PRECIP CHANCES ACROSS THE FORECAST AREA TODAY AND TUESDAY AS THE LOW FINALLY TRACKS NORTHEASTWARD. JUST WHERE THE MORE INTENSE SHOWER/STORM ACTIVITY WILL BE FOR OUR FORECAST AREA IS VERY DIFFICULT TO FIGURE OUT. THE AREA WHERE STORMS WERE MOST ACTIVE SUNDAY SHOULD HAVE SOME STABILIZATION OF THE BOUNDARY LAYER TO OVERCOME...YET BOTH THE NAM AND GFS DEPICT PRECIP FOR THAT AREA AGAIN TODAY. SOUTH-CENTRAL ARIZONA SHOULD BE LESS STABILIZED FROM LAST NIGHT BUT THIS MORNINGS SHOWERS MIGHT LEAD TO INHIBITED DEVELOPMENT LATER ON. THE 00Z LOCAL WRF HAS NOT BEEN RELIABLE OF LATE AS IT HAS FAILED TO EVEN INITIALIZE SIGNIFICANT CONVECTION. A MIX OF LOCALLY HEAVY RAIN AND STRONG WINDS WILL BE POSSIBLE ANYWHERE IN THE FORECAST AREA TODAY...LESS SO OVER PORTIONS OF SOUTHEAST CALIFORNIA TUESDAY. ON WEDNESDAY...THE LOW WILL BE EAST OF ARIZONA AND BARELY BE A SHORT WAVE BUT AN UPSTREAM KICKER SHORT WAVE MAY STILL BE OVER EASTERN PORTIONS OF THE FORECAST AREA. HOWEVER...THERE WILL BE SIGNIFICANTLY LESS MOISTURE TO WORK WITH AND THUS PRECIP CHANCES DROP DRAMATICALLY. HIGH TEMPERATURES WILL BE WELL BELOW NORMAL THROUGH TUESDAY AT MOST LOCATIONS. OVERALL FORECASTS REFLECT A MULTIMODEL BLEND. THURSDAY THROUGH SUNDAY... THE GFS AND ECMWF DIFFER ON WHERE HIGH PRESSURE WILL BE CENTERED DURING THE LATTER HALF OF THE WEEK. THE GFS HAS IT OVER ARIZONA WHEREAS THE ECMWF IS FURTHER WEST AND HAS WEAK LINGERING TROUGHING OVER NEW MEXICO. THE ECMWF IS ALSO SLOWER TO DRY THINGS OUT BUT WITH A NORTHERLY COMPONENT TO THE FLOW...IT WILL BE DIFFICULT TO HOLD ON TO ANY MEANINGFUL MOISTURE. EXCEPT FOR A SLIGHT CHANCE OVER FAR EASTERN PORTIONS OF THE FORECAST AREA THURSDAY...EXPECT DRY CONDITIONS THROUGH SUNDAY. MEANWHILE...TEMPS WILL SLOWLY WARM UP BUT IT DOES NOT APPEAR THAT THEY WILL GET MUCH ABOVE NORMAL. && .AVIATION... SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL... ALREADY LOOKING AT SOME EARLY MORNING SHOWERS ACROSS THE AREA. THESE WILL PERSIST UNTIL AROUND 15Z...WITH IMPROVING CONDITIONS EXPECTED INTO EARLY AFTERNOON. STORMS ARE EXPECTED TO INITIATE AROUND THE PHOENIX AREA BY MID AFTERNOON AND WHILE TIMING IS ALWAYS AN ISSUE...I INTRODUCED VCTS AT ALL PHOENIX SITES FROM 21Z TIL MID EVENING. STORMS SHOULD DISSIPATE GRADUALLY INTO THE EVENING HOURS. SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH... ATMOSPHERE PRETTY WORKED OVER FROM YESTERDAYS CONVECTION AND I THINK STORM COVERAGE WILL BE SOMEWHAT LIMITED TODAY. NONETHELESS...SCATTERED SHOWERS ARE EXPECTED FROM MID AFTERNOON ONWARD WITH THE BEST CHANCES AROUND 00Z. IMPROVING CONDITIONS EXPECTED AFTER MIDNIGHT /07Z/. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... WEDNESDAY THROUGH SUNDAY... HIGH PRESSURE WILL BUILD ACROSS SOUTHERN CA...PRODUCING A DRY WEST TO NORTHWESTERLY FLOW ACROSS THE FORECAST AREA. MOISTURE WILL BE SCOURED OUT WEDNESDAY...BUT MAY STILL BE SUFFICIENT FOR ISOLATED SHOWERS AND THUNDERSTORMS MAINLY ACROSS THE HIGHER ELEVATIONS. BUT BY THURSDAY...PRECIP CHANCES WILL BE NEGLIGIBLE. A WARMING TREND IS ALSO EXPECTED...WITH BELOW NORMAL TEMPERATURES APPROACHING NORMAL VALUES BY THE WEEKEND. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...AJ AVIATION...LEINS FIRE WEATHER...HIRSCH
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
355 AM MST MON SEP 10 2012 .SYNOPSIS... A WEAK UPPER LOW WILL INTERACT WITH A MOIST AIRMASS OVER ARIZONA AND SOUTHEAST CALIFORNIA...LEADING TO ABOVE AVERAGE STORM CHANCES THROUGH TUESDAY. THERE WILL BE LARGE VARIATIONS IN STORM COVERAGE AND INTENSITY FROM DAY TO DAY...WITH STORMS LIKELY TODAY AND TUESDAY OVER SOUTH-CENTRAL ARIZONA. HIGH TEMPERATURES WILL BE BELOW NORMAL THROUGH THURSDAY. DRY AIR MOVES IN DURING THE LATTER HALF OF THE WEEK WITH STORM CHANCES ENDING OVER SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA WEDNESDAY...AND OVER SOUTH-CENTRAL ARIZONA BY FRIDAY. A GRADUAL WARMING TREND WILL ACCOMPANY THE DRIER AIR. && .DISCUSSION... TODAY THROUGH WEDNESDAY...A BATCH OF SHOWERS AND THUNDERSTORMS DEVELOPED OVER SANTA CRUZ COUNTY BEFORE MIDNIGHT AND HAS WORKED ITS WAY INTO NORTHWEST PINAL AND EASTERN MARICOPA COUNTIES...BUT IN A WEAKENED STATE. THE SHOWERS APPEAR TO BE BE ASSOCIATED WITH A CIRCULATION EVIDENT IN THE WATER VAPOR IMAGERY CENTERED SOUTH-SOUTHWEST OF NOGALES. THE RUC PICKED UP ON THIS VORT MAX BUT DID NOT PLACE THE PRECIP CORRECTLY. THE 00Z NAM AND GFS DIDNT PICK UP ON IT THOUGH THE 06Z VERSIONS NOW HINT AT SOMETHING. MEANWHILE...THE UPPER LOW IS CENTERED OVER FAR NORTHERN BAJA. THE LATEST OPERATIONAL MODELS DEPICT THE MAIN AREAS OF VORTICITY CLOSER TO THE LOW CENTER AS WOULD BE EXPECTED. THE OMEGA AND UPPER LEVEL DIVERGENCE FIELDS DIFFER CONSIDERABLY THOUGH WITH THE GFS PRODUCING ITS TYPICAL SPORADIC BULLSEYES AND ASSOCIATED QPF MAXIMA. AS USUAL...THERE ARE TREMENDOUS DIFFERENCES IN THE MODEL QPF WITH THE NAM CHARACTERISTICALLY ON THE LOW SIDE...THOUGH NOT AS LOW AS THE NMM6KM. THE NAM/GFS/SREF BASED POPS ALL CONTINUE TO DEPICT WELL ABOVE NORMAL PRECIP CHANCES ACROSS THE FORECAST AREA TODAY AND TUESDAY AS THE LOW FINALLY TRACKS NORTHEASTWARD. JUST WHERE THE MORE INTENSE SHOWER/STORM ACTIVITY WILL BE FOR OUR FORECAST AREA IS VERY DIFFICULT TO FIGURE OUT. THE AREA WHERE STORMS WERE MOST ACTIVE SUNDAY SHOULD HAVE SOME STABILIZATION OF THE BOUNDARY LAYER TO OVERCOME...YET BOTH THE NAM AND GFS DEPICT PRECIP FOR THAT AREA AGAIN TODAY. SOUTH-CENTRAL ARIZONA SHOULD BE LESS STABILIZED FROM LAST NIGHT BUT THIS MORNINGS SHOWERS MIGHT LEAD TO INHIBITED DEVELOPMENT LATER ON. THE 00Z LOCAL WRF HAS NOT BEEN RELIABLE OF LATE AS IT HAS FAILED TO EVEN INITIALIZE SIGNIFICANT CONVECTION. A MIX OF LOCALLY HEAVY RAIN AND STRONG WINDS WILL BE POSSIBLE ANYWHERE IN THE FORECAST AREA TODAY...LESS SO OVER PORTIONS OF SOUTHEAST CALIFORNIA TUESDAY. ON WEDNESDAY...THE LOW WILL BE EAST OF ARIZONA AND BARELY BE A SHORT WAVE BUT AN UPSTREAM KICKER SHORT WAVE MAY STILL BE OVER EASTERN PORTIONS OF THE FORECAST AREA. HOWEVER...THERE WILL BE SIGNIFICANTLY LESS MOISTURE TO WORK WITH AND THUS PRECIP CHANCES DROP DRAMATICALLY. HIGH TEMPERATURES WILL BE WELL BELOW NORMAL THROUGH TUESDAY AT MOST LOCATIONS. OVERALL FORECASTS REFLECT A MULTIMODEL BLEND. THURSDAY THROUGH SUNDAY... THE GFS AND ECMWF DIFFER ON WHERE HIGH PRESSURE WILL BE CENTERED DURING THE LATTER HALF OF THE WEEK. THE GFS HAS IT OVER ARIZONA WHEREAS THE ECMWF IS FURTHER WEST AND HAS WEAK LINGERING TROUGHING OVER NEW MEXICO. THE ECMWF IS ALSO SLOWER TO DRY THINGS OUT BUT WITH A NORTHERLY COMPONENT TO THE FLOW...IT WILL BE DIFFICULT TO HOLD ON TO ANY MEANINGFUL MOISTURE. EXCEPT FOR A SLIGHT CHANCE OVER FAR EASTERN PORTIONS OF THE FORECAST AREA THURSDAY...EXPECT DRY CONDITIONS THROUGH SUNDAY. MEANWHILE...TEMPS WILL SLOWLY WARM UP BUT IT DOES NOT APPEAR THAT THEY WILL GET MUCH ABOVE NORMAL. && .AVIATION... SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...MOSTLY CLOUDY SKIES AND LIGHT AND VARIABLE WINDS ARE EXPECTED THROUGH MONDAY MORNING. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE FOCUSED MORE OVER EAST-CENTRAL ARIZONA ON MONDAY AFTERNOON AND EVENING. SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...THERE IS A CHANCE OF ISOLATED SHOWERS AND THUNDERSTORMS...MAINLY IN SOUTHEAST CALIFORNIA THROUGH MONDAY MORNING. WINDS WILL GENERALLY BE LIGHT...BUT COULD BECOME GUSTY IF STORMS DEVELOP IN THE AREA. OTHERWISE...SKIES WILL REMAIN CLOUDY...WITH CLOUD BASES AOA 10 KFT. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... WEDNESDAY THROUGH SUNDAY... HIGH PRESSURE WILL BUILD ACROSS SOUTHERN CA...PRODUCING A DRY WEST TO NORTHWESTERLY FLOW ACROSS THE FORECAST AREA. MOISTURE WILL BE SCOURED OUT WEDNESDAY...BUT MAY STILL BE SUFFICIENT FOR ISOLATED SHOWERS AND THUNDERSTORMS MAINLY ACROSS THE HIGHER ELEVATIONS. BUT BY THURSDAY...PRECIP CHANCES WILL BE NEGLIGIBLE. A WARMING TREND IS ALSO EXPECTED...WITH BELOW NORMAL TEMPERATURES APPROACHING NORMAL VALUES BY THE WEEKEND. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...AJ AVIATION...MCLANE FIRE WEATHER...HIRSCH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
610 AM CDT MON SEP 10 2012 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT 311 AM CDT MON SEP 10 2012 MAIN FORECAST CONCERNS ARE ON THE WARMTH TODAY AND TUESDAY...THEN WHEN PRECIPITATION ARRIVES FOR WEDNESDAY INTO WEDNESDAY NIGHT. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS SHOWED TROUGHING COMING INTO BRITISH COLUMBIA AND THE PACIFIC NORTHWEST...RIDGING ACROSS MUCH OF THE PLAINS INTO MANITOBA...AND TROUGHING ALONG THE EAST COAST. SOME CIRRUS NOTED SPILLING OVER TOP OF THE RIDGE INTO NORTHERN MINNESOTA. OTHERWISE...PLENTY OF SUBSIDENCE UNDER THE UPPER RIDGE AS WELL AS DRY AIR RESULTING IN CLEAR SKIES FROM THE CENTRAL PLAINS INTO THE FORECAST AREA. REGARDING THE DRY AIR...GOES SOUNDER PRECIPITABLE WATER IMAGERY SHOWED VALUES OF 0.3 TO 0.5 INCHES WHERE THE CLEAR SKIES ARE...OR AROUND 50 PERCENT OF NORMAL. AT THE SURFACE...HIGH PRESSURE STRETCHED FROM MISSOURI INTO LOWER MICHIGAN AND LEE TROUGHING WAS PRESENT ALONG THE EAST SIDE OF THE ROCKIES. SOUTHERLY WINDS WERE INCREASING OVER THE PLAINS INTO MINNESOTA...BOTH AT THE SURFACE AND ALOFT. AT 850MB...PROFILER DATA SHOWED 40-50 KT SOUTHWEST WINDS ACROSS THE DAKOTAS. THESE WINDS DOWNSLOPING OFF THE ROCKIES ARE PRODUCING 22-27C 850MB TEMPS OVER THE DAKOTAS PER RAP ANALYSIS. OVER THE FORECAST AREA...LIGHTER WINDS ASSOCIATED WITH THE SURFACE HIGH ALLOWING THE TYPICAL COLD SPOTS TO DROP INTO THE UPPER 30S. ANY VALLEY FOG THUS FAR HAS BEEN CONFINED TO THE WISCONSIN RIVER VALLEY...AND EVEN THAT HAS NOT CONSISTENTLY STAYED IN PLACE. TODAY THROUGH TUESDAY...MODELS ARE IN GOOD AGREEMENT SHOWING THE UPPER TROUGHING COMING INTO BRITISH COLUMBIA DEEPENING AND SHIFTING EAST TO SASKATCHEWAN BY 00Z WEDNESDAY. AS THIS OCCURS...THE UPPER RIDGING OVER THE PLAINS GETS PUSHED EAST ACROSS THE FORECAST AREA. IN ADDITION...THE LEE TROUGHING TURNS INTO A COLD FRONT AND REACHES THE SIOUX FALLS AREA BY 00Z WEDNESDAY. THE HEAT BUILDING UP ACROSS THE DAKOTAS AND THE STRENGTHENING WINDS WILL ACCOMPANY THE EASTWARD PROGRESS OF THE UPPER RIDGE. 850MB TEMPS AT 12Z THIS MORNING SHOULD RANGE FROM 9-12C EAST TO WEST. BY 00Z THIS EVENING...THEY ARE PROGGED TO CLIMB TO AT LEAST 14-17C IF NOT A LITTLE WARMER. WITH INCREASING SOUTHERLY WINDS...DRY AIR AND PLENTY OF SUN OUTSIDE OF MAYBE SOME CIRRUS...WE SHOULD HAVE NO PROBLEM MIXING TO 850MB. GOING HIGHS OF MIDDLE 70S TO LOWER 80S REFLECT THIS WELL. A SOUTHERLY BREEZE WILL HELP TO KEEP LOW TEMPERATURES IN THE 50S TONIGHT. FURTHER WARMING CONTINUES INTO TUESDAY WITH 850MB TEMPS REACHING 20-22C BY 18Z...OR 1.5-2 STANDARD DEVIATIONS ABOVE NORMAL. THERE ARE INDICATIONS OF INCREASE CIRRUS DURING THE AFTERNOON...BUT MOST OF THE DAY SHOULD SEE PLENTY OF SUN. WINDS WILL BE STRONGER... WITH SOUTHWEST SPEEDS OF 25 KT AT 925MB AND 35KT AT 850MB. THE COMBINATION OF THESE WINDS...STILL PLENTY OF DRY AIR AND THE SUN SHOULD PROPEL TEMPERATURES UP INTO THE MIDDLE 80S TO AROUND 90. WITH THE WARM...DRY AIR AND INCREASING WINDS...THERE ARE SOME FIRE WEATHER CONCERNS WHICH ARE DISCUSSED IN THE FIRE WEATHER AFD SECTION. TUESDAY NIGHT AND WEDNESDAY...UPPER RIDGING IS PROGGED TO STRENGTHEN ACROSS THE OHIO VALLEY INTO THE EASTERN GREAT LAKES REGION DURING THIS TIME. THIS IN TURN HELPS TO HOLD THE FORECAST AREA UNDER SOUTHWEST FLOW ALOFT. WITH THE COLD FRONT THAT REACHED SIOUX FALLS AT 00Z WEDNESDAY HAVING A NEAR SOUTHWEST TO NORTHEAST ORIENTATION... CLOSE TO PARALLELING THE UPPER FLOW...THE SLOW EASTWARD PROGRESS MODELS HAVE TRENDED TO THE PAST FEW DAYS MAKES SENSE. LOOKS LIKE THE COLD FRONT MAY REACH ROCHESTER AROUND 12Z WEDNESDAY...THEN SLOWLY CROSS THE FORECAST AREA BY 00Z THURSDAY. NO CONCERN EXISTS ABOUT THE FRONT INITIATING PRECIPITATION AHEAD OF IT...DUE TO A DRY CAPPED AIRMASS IN PLACE. HOWEVER...BEHIND THE FRONT THINGS ARE MORE INTERESTING. FIRST IN THE 500MB PATTERN...MODELS SHOW A POTENT SHORTWAVE DROPPING DOWN THE BACK SIDE OF THE DEEP SOUTH CENTRAL CANADA TROUGH...REACHING EASTERN MONTANA LATE WEDNESDAY. AN 80-120 KT JET AT THE TROPOPAUSE IS PROGGED TO DEVELOP AHEAD OF THIS POTENT SHORTWAVE INTO NORTHERN MINNESOTA AND ONTARIO. THIS PLACES SOUTHERN MINNESOTA INTO NORTHWEST WISCONSIN UNDER UPPER LEVEL DIVERGENCE. ALSO IN THE 500MB PATTERN THERE IS AN UPPER LOW CURRENTLY NEAR BAJA CALIFORNIA WHICH MODELS SHEAR APART AND LIFT INTO SOUTHERN MINNESOTA BY 00Z THURSDAY. THIS FEATURE WILL HELP PRODUCE SOME DPVA. LASTLY... ON THE BACK/NORTHWEST SIDE OF THE FRONT...LOW TO MID LEVEL FRONTOGENESIS IS PROGGED TO INCREASE THROUGH THE DAY WEDNESDAY. SO PLENTY OF FORCING EXISTS BEHIND THE FRONT TO PRODUCE PRECIPITATION. THIS LEAVES MOISTURE THE ONLY ISSUE...WHICH DOES NOT LOOK TO BE A PROBLEM AS PRECIPITABLE WATER VALUES CLIMB TO 1.5 INCHES BEHIND THE FRONT. THEREFORE...PRECIPITATION DEVELOPMENT BEHIND THE FRONT WILL OCCUR. THERE IS A SHOT SOME OF THIS COULD GET INTO NORTHWESTERN PORTIONS OF THE FORECAST AREA PER THE 10.00Z GFS...BUT OVERALL MODEL CONSENSUS KEEPS THE BULK OF IT NORTH AND WEST OF THE AREA ON WEDNESDAY. REGARDING TEMPERATURES...WITH THE WARM AIRMASS IN PLACE AND A SOUTHERLY BREEZE PERSISTING...TUESDAY NIGHT SHOULD SEE LOWS FROM THE MIDDLE 50S TO MIDDLE 60S. 850MB TEMPS ARE A LITTLE COOLER ON WEDNESDAY...14-18C...BUT SUN THROUGH CIRRUS ALONG/AHEAD OF THE FRONT SHOULD BRING HIGHS UP INTO THE LOW TO MID 80S. BEHIND THE FRONTAL PASSAGE...INCREASING MID/HIGH CLOUDS AND POSSIBLE PRECIPITATION WILL RESULT IN SLIGHTLY COOLER CONDITIONS. WEDNESDAY NIGHT...GOOD CONSENSUS EXISTS FOR THIS PERIOD TO BE WET... ESPECIALLY FOR THE NORTHWEST HALF OF THE FORECAST AREA. UPPER LEVEL DIVERGENCE WILL SHIFT OVER THE FORECAST AREA...ALONG WITH THE LOW TO MID LEVEL FRONTOGENESIS. THIS IS ALL RELATED TO THE DEEP SOUTH CENTRAL CANADA TROUGH LIFTING OUT TO THE NORTHEAST...AND THE POTENT SHORTWAVE IN MONTANA SHIFTING INTO THE DAKOTAS AND CLOSING OFF INTO AN UPPER LOW. AGAIN...PLENTY OF MOISTURE EXISTS WITH PRECIPITABLE WATER VALUES UP AROUND 1.5 INCHES OR 160 PERCENT OF NORMAL. GIVEN THE EXCELLENT CONTINUITY AND CONSENSUS FOR PRECIPITATION IN THE NORTHWEST HALF OF THE FORECAST AREA...HAVE RAISED PRECIPITATION CHANCES THERE TO 80 OR HIGHER. SOME NEGATIVE EPV NOTED IN CROSS SECTIONS THAT GETS INGESTED INTO THE FRONTOGENESIS CIRCULATION. THIS NEGATIVE EPV SHOULD PRODUCE CONVECTIVE BANDING AND SOME ISOLATED THUNDERSTORMS...DESPITE THE LACK OF ANY CAPE. WITH THE CONVECTIVE NATURE AND HIGH PRECIPITABLE WATER...THE QPF AMOUNTS IN THE 10.00Z GFS/NAM OF UPWARDS OF 1 INCH IN 6 HOURS IS CERTAINLY POSSIBLE. COMBINATION OF GRADUAL COLD ADVECTION BEHIND THE FRONT ALONG WITH PRECIPITATION WILL RESULT IN COOLER TEMPERATURES COMPARED TO TUESDAY NIGHT. FOLLOWED A BLEND OF GUIDANCE FOR LOWS. .LONG TERM...THURSDAY THROUGH SUNDAY NIGHT 311 AM CDT MON SEP 10 2012 10.00Z ECMWF/GFS/GFS ENSEMBLES ARE IN GOOD AGREEMENT THROUGH ABOUT FRIDAY...THEN DIFFERENCES BEGIN TO SHOW UP. THE 10.00Z CANADIAN IS A FAST OUTLIER TO START OFF WITH AS IT DOES NOT HAVE THE POTENT SHORTWAVE OVER THE WESTERN DAKOTAS AT 12Z THURSDAY LIKE OTHER MODELS. AS SUCH...THIS MODEL WAS FOR THE MOST PART DISCOUNTED. GENERAL THEME FROM THE ECMWF/GFS/GFS ENSEMBLES IS THAT THE POTENT SHORTWAVE OVER THE WESTERN DAKOTAS WILL COME CLOSE TO OR ACROSS THE FORECAST AREA ON FRIDAY AS A CLOSED OFF UPPER LOW. ALL FORCING FOR PRECIPITATION LOOKS TO REMAIN TO THE EAST OF THE UPPER LOW...WHERE THE FRONTOGENESIS IS OCCURRING. ON THURSDAY...HIGH CONFIDENCE EXISTS THAT THE SOUTHEASTERN HALF OF THE FORECAST AREA WILL SEE RAIN...AS THE FRONTOGENESIS FROM WEDNESDAY NIGHT PUSHES EAST. RAISED PRECIPITATION CHANCES IN THIS AREA TO 70. PRECIPITATION CHANCES THEN LOWER THROUGH FRIDAY...BUT DONT COMPLETELY GO AWAY DUE TO THE UPPER LOW NEARBY. TEMPERATURES WILL DEFINITELY BE COOLER. HOW COOL DEPENDS ON EXACTLY WHERE THE RAIN SETS UP. IT IS POSSIBLE THAT HIGHS ON THURSDAY COULD GET STUCK IN THE 50S WHERE IT RAINS...VERSUS MID 60S TO AROUND 70 WHERE IT DOESNT. COOL AIR ASSOCIATED WITH THE UPPER LOW SHOULD HOLD HIGHS DOWN IN THE MID 60S FOR FRIDAY. BEYOND FRIDAY...THE FORECAST PRETTY MUCH REVOLVES AROUND THE UPPER LOW. OVER THE PAST 24 HOURS OR SO...HAVE SEEN VARIOUS GFS AND ECMWF MODEL RUNS HANDLE THE UPPER LOW DIFFERENTLY. EVEN WITH THE 10.00Z RUNS...THE ECMWF TAKES IT SLOWLY EAST ACROSS IOWA AND ILLINOIS FROM FRIDAY INTO SATURDAY WHILE THE GFS HAS IT HEADING UP INTO EASTERN ONTARIO. THE 09.06Z GFS RUN HAD THE UPPER LOW ON SATURDAY STILL OVER THE FORECAST AREA. AS SUCH...FORECAST CONFIDENCE BEYOND FRIDAY IS LOW. GENERAL THEME...THOUGH...IS ANY RAIN SHOULD FOR THE MOST PART BE EAST OF THE FORECAST AREA...WHICH IS WHAT THE CONSENSUS APPROACH GIVES. BY THE TIME WE APPROACH SUNDAY...THERE ARE INDICATIONS OF A DEEPENING CENTRAL CANADA TROUGH INTO THE NORTHERN ROCKIES. IF THIS DOES OCCUR AS FORECAST...WE SHOULD SEE A WARM UP AS SOUTHERLY FLOW PICKS UP AHEAD OF THE TROUGHING. THE TEMPERATURE FORECAST PLAYS THIS IDEA WITH HIGHS CLIMBING BACK INTO THE LOW TO MID 70S FOR SUNDAY. && .AVIATION...TODAY AND TONIGHT 610 AM CDT MON SEP 10 2012 BIGGEST CONCERN TODAY/TONIGHT IS THE REMNANT VALLEY FOG/SCT-BKN IFR STRATUS AT/NEAR KLSE UNTIL ABOUT 14Z. SFC HIGH SLIPPING OFF TO THE SOUTHEAST AND INCREASING PRESSURE GRADIENT WILL ERODE/LIMIT THE BR/FG EARLY THIS MORNING. A DRY AIRMASS OVER THE AREA AND SOME WIND WILL KEEP CONDITIONS VFR THRU THE REST OF TODAY/TONIGHT. PRESSURE GRADIENT CONTINUES TO TIGHTEN OVER THE AREA THRU THE DAY...WITH SOUTH WINDS OF 10-20KTS G20-30KTS BY THIS AFTERNOON. WINDS OVER THE HIGHER TERRAIN/OPEN COUNTRY AREAS AND RIDGE-TOPS /KRST/KAUM/KCCY/ WILL TOWARD THE HIGHER END OF THE RANGE WITH THE VALLEY FLOORS /KONA/KLSE/KOVS/ TOWARD THE LOWER END OF THE WIND SPEED RANGE. GRADIENT WILL REMAIN TIGHT TONIGHT WITH SOUTH WINDS IN THE 10-15KT RANGE OVERNIGHT...WHICH WILL KEEP THE VALLEY FOG THREAT TO A MINIMUM. SOUTH WINDS WILL BE BRISK AGAIN ON TUE...15-25KT AND GUSTY. && .CLIMATE...TUESDAY 340 PM CDT SUN SEP 9 2012 HIGH TEMPERATURES WILL CLIMB TO AROUND 90 DEGREES MAINLY NORTHWEST OF A CHARLES CITY IOWA TO BLACK RIVER FALLS LINE ON TUESDAY. THE RECORD HIGHS FOR THIS DATE ARE... LA CROSSE WI - 97 IN 1897 MEDFORD WI - 95 IN 1900 ROCHESTER MN - 94 IN 1931 AUSTIN MN - 92 IN 1948 CHARLES CITY IA - 96 IN 2000 DECORAH IA - 97 IN 1895 && .FIRE WEATHER...TODAY AND TUESDAY 311 AM CDT MON SEP 10 2012 INCREASING SOUTH TO SOUTHWEST WINDS TODAY AND TUESDAY WILL BRING WARMER AIR INTO THE REGION. SPEEDS ON THESE WINDS LOOK TO RANGE FROM 15 TO 25 MPH WITH GUSTS UP TO 35 MPH. WITH PLENTY OF SUNSHINE...GOOD MIXING WILL OCCUR...BRINGING TEMPERATURES UP TO 75 TO 80 TODAY AND 85 TO 90 ON TUESDAY. DEWPOINTS ARE A LITTLE TRICKY...SINCE THE WIND DIRECTION FAVORS A RETURN FLOW OF MOISTURE. HOWEVER...THE GULF OF MEXICO DOES NOT OPEN UP FOR THE RETURN OF MOISTURE UNTIL AT LEAST LATE TUESDAY. THEREFORE...DEWPOINTS WILL TAKE THEIR TIME COMING UP...BEING COUNTERED DURING THE AFTERNOONS DUE TO MIXING. CURRENT THINKING IS THAT RELATIVE HUMIDITIES ARE GOING TO END UP IN THE 25 TO 35 PERCENT RANGE...LOWEST IN WESTERN PORTIONS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA. WITH THE DRYING LANDSCAPE/MATURING VEGETATION AND THE ABOVE WEATHER CONDITIONS...CONCERN IS THERE FOR SOME FIRES. HOWEVER...THE RELATIVE HUMIDITIES ARE JUST ABOVE THE CRITICAL 25 PERCENT THRESHOLD NEEDED FOR A FIRE WEATHER RELATED HAZARD. IN ADDITION...FIRE WEATHER USERS AFFECTED IN OUR FORECAST AREA ARE ALRIGHT WITHOUT ANY FIRE WEATHER RELATED HAZARD AT THIS TIME. && .ARX WATCHES/WARNINGS/ADVISORIES... 311 AM CDT MON SEP 10 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM...AJ AVIATION.......RIECK CLIMATE........BOYNE FIRE WEATHER...AJ
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
242 PM CDT MON SEP 10 2012 .SHORT TERM...TONIGHT AND TUESDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE SHIFTING EAST OVER THE CENTRAL GREAT LAKES WHILE LOW PRESSURE IS LOCATED OVER THE NORTHERN GREAT PLAINS. EXCEPT FOR CIRRUS FLOATING OVER NORTH DAKOTA AND NORTHERN MINNESOTA...CLEAR SKIES EXIST ACROSS MUCH OF THE MISSISSIPPI VALLEY AND THE GREAT PLAINS...OWING TO THE VERY DRY AIRMASS AHEAD OF THE LOW PRESSURE. GUSTS AHEAD OF THE LOW PRESSURE ARE ALSO REACHING INTO THE UPPER 20S TO LOWER 30S KTS WHICH WILL BE SHIFTING INTO OUR AREA TOMORROW. WITH LITTLE THREAT OF PRECIP...TEMPS AND WIND GUSTS ARE THE MAIN FORECASTS CONCERNS. TONIGHT...HIGH PRESSURE WILL SHIFT TO THE APPALACHIANS WHILE LOW PRESSURE MOVES ACROSS THE DAKOTAS. AHEAD OF THE LOW PRESSURE...THE PRESSURE GRADIENT INCREASES SUBSTANTIALLY TONIGHT AND PRODUCES A LOW LEVEL JET OF 40+ KNOTS ABOUT 1000 FT OFF THE SURFACE. THIS SHOULD KEEP THE BOUNDARY LAYER CHURNED UP ESPECIALLY OVER HIGHER TERRAIN AND PREVENT TEMPS FROM FALLING NEARLY AS COLD AS THE PAST COUPLE NIGHTS. WILL GO WITH LOWS MAINLY IN THE 50S. OTHER THAN CIRRUS DRIFTING OVERHEAD...SKIES WILL BE CLEAR. TUESDAY...LOW PRESSURE WILL MOVE ACROSS MINNESOTA AND INTO FAR NORTHWEST WISCONSIN BY 00Z WEDNESDAY. THE AIRMASS AHEAD OF THE FRONT IS VERY DRY WITH DEWPOINTS IN THE 40S AND 50S...SO NO THREAT OF ANY PRECIP AHEAD OF THE FRONT. THE TIGHT PRESSURE GRADIENT WILL STILL BE THERE AND MIXING UP TO AROUND 900MB SHOULD BE ABLE TO PRODUCE GUSTS 30 TO 35 MPH IN THE AFTERNOON. SW WINDS WILL CONTINUE TO DRAW WARMER AIR INTO THE REGION FROM THE GREAT PLAINS AS 850MB TEMPS INCREASE TO AROUND 20C. WILL NOT BE ABLE TO TAP INTO THIS AIR THOUGH...SO THE SHALLOW MIXING WILL ONLY PLACE HIGHS INTO THE LOW TO MID 80S. .LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...MAIN FCST CONCERN IS PCPN TRENDS THROUGH THE PERIOD...AND A BIG CHANGE IN TEMPERATURES FROM WEDNESDAY INTO THURSDAY. A COLD FRONT WILL ENTER NC WI ON TUESDAY NIGHT...BUT WITH AN INITIALLY DRY AIR MASS AND UPPER FORCING LAGGING TO THE WEST OF THE FRONT...WILL MAINTAIN THE DRY FCST. THE FRONT WILL SAG SE ACROSS THE FORECAST AREA ON WEDS AND WEDS NGT...WITH POST-FRONTAL PCPN DEVELOPING DUE THE INCOMING UPPER TROF...THE RRQ OF A STRG JET STREAK AND MID-LEVEL FRONTOGENETIC FORCING. ECMWF/GFS/GEM/UKMET ALL SHOW SIMILAR TIMING... WHICH WAS A BIT FASTER THAN OUR PREVIOUS FCST...AND PERHAPS 6 HOURS FASTER THAN THE 12Z NAM. HOWEVER...GIVEN RECENT MODEL DIFFERENCES AND A NEED TO MESH WITH FCSTS FROM SURROUNDING OFFICES...OPTED TO CONTINUE WITH A BLENDED APPROACH FOR POPS. REGARDLESS...THE HIGHEST POPS REMAIN CENTERED AROUND WEDS NGT AND THURSDAY. SUBSEQUENT FCSTS MAY NEED TO BE A BIT MORE AGGRESSIVE ENDING THE PCPN OVER OUR NW COUNTIES ON THU/THU NGT. SECOND PROBLEM WITH POPS OCCURS FRIDAY INTO SATURDAY...AS THE GFS SHIFTS THE UPPER TROF AND FRONT FAR ENOUGH EAST TO END THE PCPN OVER WI...WHILE THE ECMWF CLOSES OFF A STG UPPER LOW OVER THE RGN...INDUCES SFC CYCLOGENESIS...REGENERATES PCPN OVER MUCH OF WI...AND LINGERS IT WELL INTO THE WEEKEND. THE ECMWF SEEMS OVERDONE COMPARED TO THE ENSEMBLES...BUT IT SHOULD BE NOTED THAT IT HAS SHOWN AN UPPER LOW IN THE WSTRN GREAT LKS/UPPER MIDWEST LATE IN THE WEEK FOR THE PAST 5 MODEL RUNS. ONCE AGAIN...HAVE OPTED FOR THE PREFERRED MODEL BLEND...BUT BIG CHANGES WILL BE NEEDED LATER IN THE WEEK IF THE ECMWF SOLN LOOKS LIKE IT WILL VERIFY. MUCH ABOVE NORMAL TEMPERATURES (LOW TO MID 80S) IN ADVANCE OF THE FRONT WILL BE REPLACED BY SLIGHTLY COOLER THAN NORMAL 60S FOR THE END OF THE WEEK. WEEKEND TEMPS ARE UP IN THE AIR DUE TO THE PREVIOUSLY-MENTIONED MODEL DIFFERENCES. && .AVIATION...VFR CONDITIONS THROUGH TOMORROW WITH LITTLE IN THE WAY OF CLOUD COVER AND EXCELLENT VISIBILITY. LOW LEVEL WIND SHEAR WILL BE THE ONLY CONCERN TONIGHT AS A LOW LEVEL JET INCREASES TO AROUND 40 KNOTS AT 800 FT AGL WITH SFC WINDS OF 5 TO 10 KTS. ONCE TEMPERATURES WARM TUESDAY MORNING...WIND GUSTS OUT OF THE SOUTHWEST WILL INCREASE GREATER THAN 20 KTS. SOME GUSTS UP TO 30 KTS WILL BE POSSIBLE TUESDAY AFTERNOON. MPC && .MARINE...PERSISTENT AND STRENGTHENING SOUTH TO SOUTHWEST FLOW WILL LEAD TO HAZARDOUS CONDITIONS FOR SMALL CRAFT TONIGHT THROUGH WEDNESDAY. SMALL CRAFT ADVISORIES ARE ALREADY IN EFFECT. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ MPC/KIECKBUSCH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1248 PM CDT MON SEP 10 2012 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT 311 AM CDT MON SEP 10 2012 MAIN FORECAST CONCERNS ARE ON THE WARMTH TODAY AND TUESDAY...THEN WHEN PRECIPITATION ARRIVES FOR WEDNESDAY INTO WEDNESDAY NIGHT. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS SHOWED TROUGHING COMING INTO BRITISH COLUMBIA AND THE PACIFIC NORTHWEST...RIDGING ACROSS MUCH OF THE PLAINS INTO MANITOBA...AND TROUGHING ALONG THE EAST COAST. SOME CIRRUS NOTED SPILLING OVER TOP OF THE RIDGE INTO NORTHERN MINNESOTA. OTHERWISE...PLENTY OF SUBSIDENCE UNDER THE UPPER RIDGE AS WELL AS DRY AIR RESULTING IN CLEAR SKIES FROM THE CENTRAL PLAINS INTO THE FORECAST AREA. REGARDING THE DRY AIR...GOES SOUNDER PRECIPITABLE WATER IMAGERY SHOWED VALUES OF 0.3 TO 0.5 INCHES WHERE THE CLEAR SKIES ARE...OR AROUND 50 PERCENT OF NORMAL. AT THE SURFACE...HIGH PRESSURE STRETCHED FROM MISSOURI INTO LOWER MICHIGAN AND LEE TROUGHING WAS PRESENT ALONG THE EAST SIDE OF THE ROCKIES. SOUTHERLY WINDS WERE INCREASING OVER THE PLAINS INTO MINNESOTA...BOTH AT THE SURFACE AND ALOFT. AT 850MB...PROFILER DATA SHOWED 40-50 KT SOUTHWEST WINDS ACROSS THE DAKOTAS. THESE WINDS DOWNSLOPING OFF THE ROCKIES ARE PRODUCING 22-27C 850MB TEMPS OVER THE DAKOTAS PER RAP ANALYSIS. OVER THE FORECAST AREA...LIGHTER WINDS ASSOCIATED WITH THE SURFACE HIGH ALLOWING THE TYPICAL COLD SPOTS TO DROP INTO THE UPPER 30S. ANY VALLEY FOG THUS FAR HAS BEEN CONFINED TO THE WISCONSIN RIVER VALLEY...AND EVEN THAT HAS NOT CONSISTENTLY STAYED IN PLACE. TODAY THROUGH TUESDAY...MODELS ARE IN GOOD AGREEMENT SHOWING THE UPPER TROUGHING COMING INTO BRITISH COLUMBIA DEEPENING AND SHIFTING EAST TO SASKATCHEWAN BY 00Z WEDNESDAY. AS THIS OCCURS...THE UPPER RIDGING OVER THE PLAINS GETS PUSHED EAST ACROSS THE FORECAST AREA. IN ADDITION...THE LEE TROUGHING TURNS INTO A COLD FRONT AND REACHES THE SIOUX FALLS AREA BY 00Z WEDNESDAY. THE HEAT BUILDING UP ACROSS THE DAKOTAS AND THE STRENGTHENING WINDS WILL ACCOMPANY THE EASTWARD PROGRESS OF THE UPPER RIDGE. 850MB TEMPS AT 12Z THIS MORNING SHOULD RANGE FROM 9-12C EAST TO WEST. BY 00Z THIS EVENING...THEY ARE PROGGED TO CLIMB TO AT LEAST 14-17C IF NOT A LITTLE WARMER. WITH INCREASING SOUTHERLY WINDS...DRY AIR AND PLENTY OF SUN OUTSIDE OF MAYBE SOME CIRRUS...WE SHOULD HAVE NO PROBLEM MIXING TO 850MB. GOING HIGHS OF MIDDLE 70S TO LOWER 80S REFLECT THIS WELL. A SOUTHERLY BREEZE WILL HELP TO KEEP LOW TEMPERATURES IN THE 50S TONIGHT. FURTHER WARMING CONTINUES INTO TUESDAY WITH 850MB TEMPS REACHING 20-22C BY 18Z...OR 1.5-2 STANDARD DEVIATIONS ABOVE NORMAL. THERE ARE INDICATIONS OF INCREASE CIRRUS DURING THE AFTERNOON...BUT MOST OF THE DAY SHOULD SEE PLENTY OF SUN. WINDS WILL BE STRONGER... WITH SOUTHWEST SPEEDS OF 25 KT AT 925MB AND 35KT AT 850MB. THE COMBINATION OF THESE WINDS...STILL PLENTY OF DRY AIR AND THE SUN SHOULD PROPEL TEMPERATURES UP INTO THE MIDDLE 80S TO AROUND 90. WITH THE WARM...DRY AIR AND INCREASING WINDS...THERE ARE SOME FIRE WEATHER CONCERNS WHICH ARE DISCUSSED IN THE FIRE WEATHER AFD SECTION. TUESDAY NIGHT AND WEDNESDAY...UPPER RIDGING IS PROGGED TO STRENGTHEN ACROSS THE OHIO VALLEY INTO THE EASTERN GREAT LAKES REGION DURING THIS TIME. THIS IN TURN HELPS TO HOLD THE FORECAST AREA UNDER SOUTHWEST FLOW ALOFT. WITH THE COLD FRONT THAT REACHED SIOUX FALLS AT 00Z WEDNESDAY HAVING A NEAR SOUTHWEST TO NORTHEAST ORIENTATION... CLOSE TO PARALLELING THE UPPER FLOW...THE SLOW EASTWARD PROGRESS MODELS HAVE TRENDED TO THE PAST FEW DAYS MAKES SENSE. LOOKS LIKE THE COLD FRONT MAY REACH ROCHESTER AROUND 12Z WEDNESDAY...THEN SLOWLY CROSS THE FORECAST AREA BY 00Z THURSDAY. NO CONCERN EXISTS ABOUT THE FRONT INITIATING PRECIPITATION AHEAD OF IT...DUE TO A DRY CAPPED AIRMASS IN PLACE. HOWEVER...BEHIND THE FRONT THINGS ARE MORE INTERESTING. FIRST IN THE 500MB PATTERN...MODELS SHOW A POTENT SHORTWAVE DROPPING DOWN THE BACK SIDE OF THE DEEP SOUTH CENTRAL CANADA TROUGH...REACHING EASTERN MONTANA LATE WEDNESDAY. AN 80-120 KT JET AT THE TROPOPAUSE IS PROGGED TO DEVELOP AHEAD OF THIS POTENT SHORTWAVE INTO NORTHERN MINNESOTA AND ONTARIO. THIS PLACES SOUTHERN MINNESOTA INTO NORTHWEST WISCONSIN UNDER UPPER LEVEL DIVERGENCE. ALSO IN THE 500MB PATTERN THERE IS AN UPPER LOW CURRENTLY NEAR BAJA CALIFORNIA WHICH MODELS SHEAR APART AND LIFT INTO SOUTHERN MINNESOTA BY 00Z THURSDAY. THIS FEATURE WILL HELP PRODUCE SOME DPVA. LASTLY... ON THE BACK/NORTHWEST SIDE OF THE FRONT...LOW TO MID LEVEL FRONTOGENESIS IS PROGGED TO INCREASE THROUGH THE DAY WEDNESDAY. SO PLENTY OF FORCING EXISTS BEHIND THE FRONT TO PRODUCE PRECIPITATION. THIS LEAVES MOISTURE THE ONLY ISSUE...WHICH DOES NOT LOOK TO BE A PROBLEM AS PRECIPITABLE WATER VALUES CLIMB TO 1.5 INCHES BEHIND THE FRONT. THEREFORE...PRECIPITATION DEVELOPMENT BEHIND THE FRONT WILL OCCUR. THERE IS A SHOT SOME OF THIS COULD GET INTO NORTHWESTERN PORTIONS OF THE FORECAST AREA PER THE 10.00Z GFS...BUT OVERALL MODEL CONSENSUS KEEPS THE BULK OF IT NORTH AND WEST OF THE AREA ON WEDNESDAY. REGARDING TEMPERATURES...WITH THE WARM AIRMASS IN PLACE AND A SOUTHERLY BREEZE PERSISTING...TUESDAY NIGHT SHOULD SEE LOWS FROM THE MIDDLE 50S TO MIDDLE 60S. 850MB TEMPS ARE A LITTLE COOLER ON WEDNESDAY...14-18C...BUT SUN THROUGH CIRRUS ALONG/AHEAD OF THE FRONT SHOULD BRING HIGHS UP INTO THE LOW TO MID 80S. BEHIND THE FRONTAL PASSAGE...INCREASING MID/HIGH CLOUDS AND POSSIBLE PRECIPITATION WILL RESULT IN SLIGHTLY COOLER CONDITIONS. WEDNESDAY NIGHT...GOOD CONSENSUS EXISTS FOR THIS PERIOD TO BE WET... ESPECIALLY FOR THE NORTHWEST HALF OF THE FORECAST AREA. UPPER LEVEL DIVERGENCE WILL SHIFT OVER THE FORECAST AREA...ALONG WITH THE LOW TO MID LEVEL FRONTOGENESIS. THIS IS ALL RELATED TO THE DEEP SOUTH CENTRAL CANADA TROUGH LIFTING OUT TO THE NORTHEAST...AND THE POTENT SHORTWAVE IN MONTANA SHIFTING INTO THE DAKOTAS AND CLOSING OFF INTO AN UPPER LOW. AGAIN...PLENTY OF MOISTURE EXISTS WITH PRECIPITABLE WATER VALUES UP AROUND 1.5 INCHES OR 160 PERCENT OF NORMAL. GIVEN THE EXCELLENT CONTINUITY AND CONSENSUS FOR PRECIPITATION IN THE NORTHWEST HALF OF THE FORECAST AREA...HAVE RAISED PRECIPITATION CHANCES THERE TO 80 OR HIGHER. SOME NEGATIVE EPV NOTED IN CROSS SECTIONS THAT GETS INGESTED INTO THE FRONTOGENESIS CIRCULATION. THIS NEGATIVE EPV SHOULD PRODUCE CONVECTIVE BANDING AND SOME ISOLATED THUNDERSTORMS...DESPITE THE LACK OF ANY CAPE. WITH THE CONVECTIVE NATURE AND HIGH PRECIPITABLE WATER...THE QPF AMOUNTS IN THE 10.00Z GFS/NAM OF UPWARDS OF 1 INCH IN 6 HOURS IS CERTAINLY POSSIBLE. COMBINATION OF GRADUAL COLD ADVECTION BEHIND THE FRONT ALONG WITH PRECIPITATION WILL RESULT IN COOLER TEMPERATURES COMPARED TO TUESDAY NIGHT. FOLLOWED A BLEND OF GUIDANCE FOR LOWS. .LONG TERM...THURSDAY THROUGH SUNDAY NIGHT 311 AM CDT MON SEP 10 2012 10.00Z ECMWF/GFS/GFS ENSEMBLES ARE IN GOOD AGREEMENT THROUGH ABOUT FRIDAY...THEN DIFFERENCES BEGIN TO SHOW UP. THE 10.00Z CANADIAN IS A FAST OUTLIER TO START OFF WITH AS IT DOES NOT HAVE THE POTENT SHORTWAVE OVER THE WESTERN DAKOTAS AT 12Z THURSDAY LIKE OTHER MODELS. AS SUCH...THIS MODEL WAS FOR THE MOST PART DISCOUNTED. GENERAL THEME FROM THE ECMWF/GFS/GFS ENSEMBLES IS THAT THE POTENT SHORTWAVE OVER THE WESTERN DAKOTAS WILL COME CLOSE TO OR ACROSS THE FORECAST AREA ON FRIDAY AS A CLOSED OFF UPPER LOW. ALL FORCING FOR PRECIPITATION LOOKS TO REMAIN TO THE EAST OF THE UPPER LOW...WHERE THE FRONTOGENESIS IS OCCURRING. ON THURSDAY...HIGH CONFIDENCE EXISTS THAT THE SOUTHEASTERN HALF OF THE FORECAST AREA WILL SEE RAIN...AS THE FRONTOGENESIS FROM WEDNESDAY NIGHT PUSHES EAST. RAISED PRECIPITATION CHANCES IN THIS AREA TO 70. PRECIPITATION CHANCES THEN LOWER THROUGH FRIDAY...BUT DONT COMPLETELY GO AWAY DUE TO THE UPPER LOW NEARBY. TEMPERATURES WILL DEFINITELY BE COOLER. HOW COOL DEPENDS ON EXACTLY WHERE THE RAIN SETS UP. IT IS POSSIBLE THAT HIGHS ON THURSDAY COULD GET STUCK IN THE 50S WHERE IT RAINS...VERSUS MID 60S TO AROUND 70 WHERE IT DOESNT. COOL AIR ASSOCIATED WITH THE UPPER LOW SHOULD HOLD HIGHS DOWN IN THE MID 60S FOR FRIDAY. BEYOND FRIDAY...THE FORECAST PRETTY MUCH REVOLVES AROUND THE UPPER LOW. OVER THE PAST 24 HOURS OR SO...HAVE SEEN VARIOUS GFS AND ECMWF MODEL RUNS HANDLE THE UPPER LOW DIFFERENTLY. EVEN WITH THE 10.00Z RUNS...THE ECMWF TAKES IT SLOWLY EAST ACROSS IOWA AND ILLINOIS FROM FRIDAY INTO SATURDAY WHILE THE GFS HAS IT HEADING UP INTO EASTERN ONTARIO. THE 09.06Z GFS RUN HAD THE UPPER LOW ON SATURDAY STILL OVER THE FORECAST AREA. AS SUCH...FORECAST CONFIDENCE BEYOND FRIDAY IS LOW. GENERAL THEME...THOUGH...IS ANY RAIN SHOULD FOR THE MOST PART BE EAST OF THE FORECAST AREA...WHICH IS WHAT THE CONSENSUS APPROACH GIVES. BY THE TIME WE APPROACH SUNDAY...THERE ARE INDICATIONS OF A DEEPENING CENTRAL CANADA TROUGH INTO THE NORTHERN ROCKIES. IF THIS DOES OCCUR AS FORECAST...WE SHOULD SEE A WARM UP AS SOUTHERLY FLOW PICKS UP AHEAD OF THE TROUGHING. THE TEMPERATURE FORECAST PLAYS THIS IDEA WITH HIGHS CLIMBING BACK INTO THE LOW TO MID 70S FOR SUNDAY. && .AVIATION...THROUGH 18Z TUESDAY 1248 PM CDT MON SEP 10 2012 MAIN CONCERNS AT THE TAF SITES THROUGH THE PERIOD ARE BREEZY SOUTH TO SOUTHWEST WINDS AND LOW LEVEL WIND SHEAR LATE TONIGHT INTO EARLY TUESDAY MORNING. OTHERWISE PLAN ON VFR CONDITIONS. THE AREA WILL BE IN A TIGHT PRESSURE GRADIENT WITH A SURFACE TROUGH LOCATED ACROSS THE DAKOTAS AND HIGH PRESSURE CENTERED OVER THE APPALACHIANS. PLAN ON SOUTH WINDS TODAY AT 15 TO 20 KTS WITH GUSTS AROUND 29 KTS POSSIBLE...ESPECIALLY AT KRST. SURFACE WINDS WILL SUBSIDE INTO THE 12 TO 14 KT RANGE THIS EVENING. A 45 TO 50 KT LOW LEVEL JET IS EXPECTED TO DEVELOP AROUND 05Z AT THE TAF SITES. HAVE INCLUDED WIND SHEAR IN THE TAF STARTING AT 1500 FT. THE LOW LEVEL JET SHOULD DECREASE AROUND 13Z...BUT SURFACE WINDS ARE EXPECTED TO RAPIDLY INCREASE AFTER SUNRISE. PLAN ON SOUTHWEST WINDS AT 15 TO 20 KTS WITH GUSTS AROUND 30 KTS BY LATE TOMORROW MORNING. && .CLIMATE...TUESDAY 340 PM CDT SUN SEP 9 2012 HIGH TEMPERATURES WILL CLIMB TO AROUND 90 DEGREES MAINLY NORTHWEST OF A CHARLES CITY IOWA TO BLACK RIVER FALLS LINE ON TUESDAY. THE RECORD HIGHS FOR THIS DATE ARE... LA CROSSE WI - 97 IN 1897 MEDFORD WI - 95 IN 1900 ROCHESTER MN - 94 IN 1931 AUSTIN MN - 92 IN 1948 CHARLES CITY IA - 96 IN 2000 DECORAH IA - 97 IN 1895 && .FIRE WEATHER...TODAY AND TUESDAY 311 AM CDT MON SEP 10 2012 INCREASING SOUTH TO SOUTHWEST WINDS TODAY AND TUESDAY WILL BRING WARMER AIR INTO THE REGION. SPEEDS ON THESE WINDS LOOK TO RANGE FROM 15 TO 25 MPH WITH GUSTS UP TO 35 MPH. WITH PLENTY OF SUNSHINE...GOOD MIXING WILL OCCUR...BRINGING TEMPERATURES UP TO 75 TO 80 TODAY AND 85 TO 90 ON TUESDAY. DEWPOINTS ARE A LITTLE TRICKY...SINCE THE WIND DIRECTION FAVORS A RETURN FLOW OF MOISTURE. HOWEVER...THE GULF OF MEXICO DOES NOT OPEN UP FOR THE RETURN OF MOISTURE UNTIL AT LEAST LATE TUESDAY. THEREFORE...DEWPOINTS WILL TAKE THEIR TIME COMING UP...BEING COUNTERED DURING THE AFTERNOONS DUE TO MIXING. CURRENT THINKING IS THAT RELATIVE HUMIDITIES ARE GOING TO END UP IN THE 25 TO 35 PERCENT RANGE...LOWEST IN WESTERN PORTIONS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA. WITH THE DRYING LANDSCAPE/MATURING VEGETATION AND THE ABOVE WEATHER CONDITIONS...CONCERN IS THERE FOR SOME FIRES. HOWEVER...THE RELATIVE HUMIDITIES ARE JUST ABOVE THE CRITICAL 25 PERCENT THRESHOLD NEEDED FOR A FIRE WEATHER RELATED HAZARD. IN ADDITION...FIRE WEATHER USERS AFFECTED IN OUR FORECAST AREA ARE ALRIGHT WITHOUT ANY FIRE WEATHER RELATED HAZARD AT THIS TIME. && .ARX WATCHES/WARNINGS/ADVISORIES... 311 AM CDT MON SEP 10 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM...AJ AVIATION...WETENKAMP CLIMATE........BOYNE FIRE WEATHER...AJ