Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 271715
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1215 PM CDT MON OCT 27 2014

.UPDATE...
ISSUED AT 1215 PM CDT MON OCT 27 2014

SHORT-RANGE MODELS CONTINUE TO STRUGGLE WITH THE LOW LEVEL MOISTURE/
CLOUDS ACROSS THE REGION THIS MORNING. THIS EVIDENCED BY THE FACT
THAT PER SFC OBS THERE ARE NO CLOUDS BELOW 10K FT OVER MOST OF
IA...THE SOUTHEAST HALF OF MN AND SOUTHWEST 2/3 OF WI. FINALLY SOME
2500FT STRATO-CU CLOUDS OVER FAR SOUTHWEST WI/NEARBY AREAS AT 17Z.
KDMX WSR-88D SHOWING SOME WEAK RETURNS OVER WESTERN IA...BUT THESE
OUT OF A 14K-15K FT ALTO-CU DECK. VARIOUS MODEL SOUNDINGS IN BUFKIT
DO SHOW SOME 200-800 J/KG OF CAPE OVER ABOUT THE SOUTHEAST 1/2 OF
THE FCST AREA THIS AFTERNOON INTO THIS EVENING...WHEN LIFTING SFC-
900MB PARCELS. THIS WITH A MDT/STRONG UPWARD MOTION SIGNAL IN THE
NEAR SFC TO 500MB LAYER...AHEAD OF THE SHORTWAVES APPROACHING FROM
NEB/DAKOTAS. HOWEVER...SOUNDINGS SHOWING SIGNIFICANT CAPPING TO THIS
CAPE...WITH 200-450 J/KG OF CIN IN THE 875-600MB LAYER THIS
AFTERNOON. THIS WITH SFC DEW POINTS CLIMBING INTO THE MID 50S TO
LOWER 60S...WHICH PER 17Z SFC OBS APPEARS REASONABLE. GIVEN THE
STRONG CAPPING...REMOVED/REDUCED SHRA CHANCES ACROSS MUCH OF THE
FCST AREA THIS AFTERNOON INTO THIS EVENING. DID LEAVE AN ISOLATED
TSRA MENTION ACROSS THE FAR SOUTHEAST END OF THE FCST AREA IN THE
23Z-03Z TIME-FRAME JUST IN CASE A CONVECTIVE PULSE CAN TAP INTO THE
CAPE...WHICH WANES/IS PUSHED OUT RATHER QUICKLY THRU THE EVENING.
WITH THINNER CLOUDS/MORE SUNSHINE TODAY...RAISED HIGHS A DEGREE OR
TWO MOST LOCATIONS AS WELL.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 253 AM CDT MON OCT 27 2014

FOCUS IS ON RAIN THIS MORNING...AND POTENTIAL FOR REDEVELOPMENT
LATER THIS AFTERNOON AND TONIGHT. SHORTLY AFTER MIDNIGHT SHOWERS
AND THUNDERSTORMS DEVELOPED ALONG AND NORTH OF I-94 AS WAS
PREVIOUSLY ANTICIPATED. THAT ACTIVITY IS MOVING NORTHEAST...AND
ANTICIPATE DRY WEATHER THROUGH THE MORNING AND INTO THE EARLY
AFTERNOON. BUT A POTENT LONG WAVE TROUGH WITH EMBEDDED SHORT WAVE
ENERGY WILL BE MOVING THROUGH THE REGION TODAY...DRIVING A SURFACE
LOW AND COLD FRONT ACROSS DURING THE AFTERNOON. ADDITIONAL RAIN
ACTIVITY IS EXPECTED TO DEVELOP ALONG THIS BOUNDARY. BUT IT DOES
APPEAR THAT THE TIMING IS SLIGHTLY OFF...WITH THE FRONT ALMOST ALL
THE WAY THROUGH THE FORECAST AREA BEFORE NEW CONVECTION DEVELOPS.
THUS HAVE MAINTAINED THE RAIN CHANCES WITH THE HIGHEST RISK OVER
THE FAR SOUTHEAST PART OF OUR AREA FROM LATE AFTERNOON INTO THE
EVENING. SOME QUESTION TODAY ON CLOUDS AS WELL. A FEW OF THE
MESOSCALE MODELS SUGGEST DRY AIR ROTATING IN FOR A TIME...LEADING
TO LESS CLOUD COVER AND POTENTIALLY WARMER TEMPERATURES. DID RAISE
TEMPS A FEW DEGREES...ESPECIALLY OVER NORTHEAST IOWA AND SOUTHWEST
WISCONSIN WHERE THE FRONTAL PASSAGE WILL OCCUR LATEST.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 253 AM CDT MON OCT 27 2014

COOLER AIR DROPPING INTO THE REGION BEHIND THE DEPARTING UPPER
TROUGH ON TUESDAY. COULD BE A BIT BREEZY AS WELL WITH GOOD
DOWNWARD MOMENTUM TRANSPORT. WITH THE COOLER AIR REGIME...COULD
SEE SOME INSTABILITY SHOWERS FROM CENTRAL MN INTO NORTHERN WI.
HIGH PRESSURE WILL PROVIDE DRY AND COOL CONDITIONS FOR WEDNESDAY.
BUT A WEAK DISTURBANCE IN THE NORTHWEST FLOW BEHIND THE DEPARTING
TROUGH IS EXPECTED TO MOVE THROUGH WEDNESDAY NIGHT INTO THURSDAY.
THIS FEATURE HAS BEEN PRESENT IN THE MODELS FOR SEVERAL DAYS
NOW...WITH VARYING DEGREES OF STRENGTH AND AVAILABLE MOISTURE.
PREVIOUS FORECAST TOOK THE RAIN CHANCE OUT...AND HAVE MAINTAINED
THAT CONTINUITY FOR NOW. WOULD NOT BE SURPRISED TO SEE SOME LIGHT
SHOWERS HOWEVER...SO WILL CONTINUE TO MONITOR. ANOTHER REINFORCING
SHOT OF COLD AIR ARRIVES TO END THE WEEK AS A SPRAWLING HIGH
PRESSURE AREA DROPS IN FROM CANADA. FRIDAY SHOULD BE A CHILLY FALL
DAY...AND SATURDAY MORNING LOOKS QUITE CRISP. BUT THE UPPER
PATTERN IS REALLY AMPLIFYING BY THIS TIME...AND WITH A DEEPENING
SURFACE LOW PRESSURE ALONG THE FRONT RANGE OF THE MT/WY ROCKIES...
SOUTHERLY FLOW WILL RETURN AND WILL BEGIN A SLOW MODERATION. COULD
BE SOME LIGHT SHOWERS IN THE WARM ADVECTION ON SUNDAY...BUT AT
THIS POINT NOT LOOKING LIKE ANYTHING SIGNIFICANT. BRUNT OF THIS
SYSTEM LOOKS TO STAY TO THE NORTH OF THE LOCAL AREA AT THIS
POINT...SO MINIMAL IMPACT. BUT WILL HAVE TO WATCH THE EVOLUTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1215 PM CDT MON OCT 27 2014

CONTINUED WITH A VFR FORECAST THROUGH THE PERIOD. LOW CLOUDS/STRATUS
CONTINUE TO LOOK LIKE A NO-SHOW...EXCEPT FOR SOME SCT DIURNALLY
DRIVEN STRATO-CU IN THE 4K-5K FT RANGE LATER THIS AFTERNOON/EARLY
THIS EVENING. SFC-MID LEVEL LOW/TROUGH SLIDES ACROSS THE AREA
TONIGHT...WITH INCREASING NORTHWEST FLOW/DEEPER SUBSIDENCE SCOURING
OUT MUCH OF THE MOISTURE. GRADIENT TIGHTENS WITH STEEP LOW LEVEL
LAPSE RATES FOR MIXING...WITH WEST TO NORTHWEST WINDS INCREASING
INTO THE 10-15KT RANGE LATER TONIGHT...THEN IN THE 15-20KT G25KT
RANGE WITH STEEP LOW LEVEL LAPSE RATES FOR LATER TUE MORNING/
AFTERNOON. THE NORTHWEST FLOW EVENTUALLY WRAPS SOME OF THE MOISTURE
BEHIND THE DEPARTING SYSTEM SOUTH/SOUTHEAST ACROSS THE AREA FOR
LATER TUE MORNING/AFTERNOON. SOUNDINGS AND X-SECTIONS SHOWING THIS
TO BE IN THE 4K-5K FT RANGE WHEN IT REACHES THE TAF SITES.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

UPDATE.......RRS
SHORT TERM...MW
LONG TERM....MW
AVIATION.....RRS



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