Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 271844
AFDARX

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

.UPDATE...
ISSUED AT 144 PM CDT MON OCT 27 2014

HAVE HAD TO ADD AN ISOLATED SHRA MENTION TO THE NORTHWEST 1/2 TO 2/3
OF THE FCST AREA FOR THE AFTERNOON. WEAK 700-500MB SHORTWAVE
ROTATING INTO WESTERN IA WITH 700-300MB LAPSE RATES IN THE 8.5C/KM
RANGE. SATURATING/LIFTING 650-600MB PARCELS RESULTS IN 100-200 J/KG
CAPE...EVEN FROM THIS HIGH UP. THESE COMBINED ELEMENTS HAVE MANAGED
TO PRODUCE WDLY SCT SHRA AND EVEN A FEW TSRA ACROSS WEST CENTRAL
INTO NORTHWEST IA EARLY THIS AFTERNOON. ALL THIS TRANSLATING
NORTHEAST TOWARD THE FCST AREA AT 35-40KTS...THUS ADDED THE ISOLATED
SHRA MENTION TO THE AFTERNOON FCST GRIDS. TSRA SEEMS TO COME AND GO
AS THE WEAK CONVECTION PULSES AND LEFT THIS OUT OF THE AFTERNOON
GRIDS FOR NOW. FALLING FROM 14K FT OR HIGHER...AND MOVING AT 35-
40KTS...PRECIP AT ANY ONE LOCATION LOOKS TO BE MORE SHORT DURATION
SPRINKLES.

&&

.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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