Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221754
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1254 PM CDT WED OCT 22 2014

.UPDATE...
ISSUED AT 1013 AM CDT WED OCT 22 2014

HAVE UPDATED THE FORECAST TO ADJUST PRECIPITATION CHANCES THIS
AFTERNOON AND LINGER THEM INTO THIS EVENING...AHEAD OF THE MAIN
BAND OF PRECIP EXPECTED TO MOVE IN LATER TONIGHT. IF RAIN SHOWERS
DEVELOP THIS AFTERNOON THEY WILL BE ON THE LEADING EDGE OF 850 MB
MOISTURE TRANSPORT. THERE IS SOME WEAK ELEVATED CAPE TO WORK WITH
THIS AFTERNOON INTO EARLY THIS EVENING RAISING THE CONCERN FOR AN
ISOLATED THUNDERSTORM OR TWO. THE NAM FORECAST SOUNDING FROM KLSE
IS SHOWING AROUND 350 J/KG WHEN LIFTING FROM 850 MB. IF THIS CAPE
IS REALIZED...WE COULD SEE A FEW LIGHTNING STRIKES. CONFIDENCE IS
LOW ON ANY THUNDERSTORM ACTIVITY OCCURRING THIS AFTERNOON INTO
EARLY THIS EVENING SO WILL NOT INCLUDE THUNDERSTORM CHANCES AT
THIS TIME. THE REST OF THE FORECAST REMAINS ON TRACK.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 352 AM CDT WED OCT 22 2014

AT 3 AM...A 1030 MB SURFACE HIGH WAS CENTERED OVER ONTARIO. THIS
HAS PRODUCED LIGHT WINDS ACROSS WESTERN WISCONSIN AND CLEAR SKIES
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. THIS HAS ALLOWED DENSE
VALLEY FOG TO DEVELOP IN THE WISCONSIN AND KICKAPOO RIVER VALLEYS.
MEANWHILE THE RAP SOUNDINGS CONTINUE TO SUGGEST THAT THE WINDS
ALOFT WILL CONTINUE TO INCREASE DURING THE REMAINDER OF THE
MORNING. HOWEVER WE MAY HAVE JUST ENOUGH TIME TO BUILD A SHALLOW
NOCTURNAL INVERSION THAT MAY ALLOW SOME STRATUS AND SOME PATCHY
VALLEY FOG TO DEVELOP IN THE MISSISSIPPI CHANNEL AND ITS
TRIBUTARIES.

FOR TONIGHT...THE 22.00Z MODELS ARE IN GOOD AGREEMENT THAT A SHORT
WAVE TROUGH WILL MOVE THROUGH THE REGION. THIS RESULTS...IN
MODERATE TO STRONG 900 TO 800 MB FRONTOGENESIS TO DEVELOP ALONG
AND SOUTH OF THE INTERSTATE 90 CORRIDOR AND THERE WILL MODERATE
850 MB MOISTURE TRANSPORT. OVERALL LIKE THE TIMING OF NMM AND
ARW...SO TRENDED THE PRECIPITATION CHANCES TOWARD THEM FOR
TONIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 352 AM CDT WED OCT 22 2014

ON THURSDAY...THE 22.00Z MODELS ARE VERY SIMILAR WITH THE FASTER
MOVEMENT OF THE SHORT WAVE TROUGH THROUGH THE REGION. THIS RESULT
IN A RAPID DECREASE IN THE 900 TO 800 MB FRONTOGENESIS AND THE
850 MB MOISTURE TRANSPORT MOVING EAST OF THE AREA BY THE
AFTERNOON. THIS RESULTS IN A QUICK DECREASE IN THE PRECIPITATION
FROM WEST TO EAST DURING THE MORNING AND EARLY AFTERNOON. THIS
SEEMS TO BE HANDLED REALLY WELL IN THE ARW AND NMM...SO TRENDED
PRECIPITATION TIMING AND PLACEMENT CLOSER TO THEM. ALSO MODEL
SOUNDINGS SHOW A RAPID DECREASE IN CLOUD COVER ALONG AND WEST OF
THE MISSISSIPPI RIVER DURING THE AFTERNOON. THIS PROVIDES A BETTER
OPPORTUNITY THAT WE COULD POTENTIALLY SEE THE PARTIAL SOLAR
ECLIPSE DURING THE LATE AFTERNOON.

ON FRIDAY...ALL OF THE MODELS ARE IN GENERAL AGREEMENT THAT A
SHORT WAVE TROUGH WILL MOVE EAST THROUGH THE AREA. THE NAM
SOUNDINGS HAVE A MUCH DEEPER MOISTURE PROFILE AND STRONGER 850 MB
MOISTURE TRANSPORT THAN THE GFS...GEM...AND ECMWF. AS A RESULT...
IT GENERATES SHOWERS AND THE OTHER MODEL SOLUTIONS ARE DRY. DUE TO
THIS...OPTED TO KEEP THE PERIOD DRY. 850 MB TEMPERATURES CLIMB 2
TO 4C WARMER THAN THURSDAY. MIXING 875 MB TEMPERATURES TO THE
SURFACE RESULTS IN TEMPERATURES MUCH CLOSER TO THE 22.03Z SREF
THAN THE SUPER BLEND...SO TRENDED THEM MORE TOWARD THE LATTER.

FROM FRIDAY NIGHT INTO SATURDAY...AN ANOMALOUSLY STRONG 150 KNOT
200 MB JET ROUNDING THE EASTERN PERIPHERY OF THE UPPER LEVEL
RIDGE. THE 21.12Z NAEFS STANDARDIZED ANOMALY SHOWED THAT A JET
THIS STRONG HAD A RETURN FREQUENCY OF ONCE IN EVERY 5 YEARS. THIS
RESULTS IN A RETROGRESSION OF THIS RIDGE WHICH IN TURN ALLOWS
COOLER 850 MB TEMPERATURES TO MOVE BACK INTO THE REGION. THERE IS
A 6 TO 8C DROP ACROSS WESTERN WISCONSIN AND 4 TO 6C ACROSS
SOUTHEAST MINNESOTA AND NORTHEAST IOWA. DUE TO THIS...LOWERED THE
MAXIMUM TEMPERATURES ANYWHERE FROM 2 TO 6 DEGREES.

ON SUNDAY...THE UPPER LEVEL RIDGE REESTABLISHES ITSELF ACROSS THE
AREA AS A LONG WAVE TROUGH MOVES EAST INTO THE WESTERN UNITED
STATES. 850 MB TEMPERATURES RISE 6 TO 8C INTO THE 10C TO 14C
RANGE. THESE TEMPERATURES ARE AROUND 1.8 STANDARD DEVIATIONS ABOVE
NORMAL. THE SUPER BLEND LOOKS TOO COLD...SO RAISED THE HIGH
TEMPERATURES CLOSER TO THE BIAS CORRECTED GFS AND ECMWF.

FROM SUNDAY NIGHT INTO TUESDAY...THE MODELS ARE DIFFERING ON THE
TRACK OF A STRENGTHENING LOW PRESSURE SYSTEM MOVING THROUGH THE
REGION. THE GFS IS MUCH FURTHER THAN EITHER THE ECMWF OR GEM. DUE
TO THIS...STAYED CLOSED TO THE MODEL CONSENSUS FOR TEMPERATURES
AND PRECIPITATION CHANCES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1254 PM CDT WED OCT 22 2014

A TROUGH WILL SWING THROUGH THE REGION TONIGHT BRINGING RAIN AND
MVFR/IFR CONDITIONS TO THE TAF SITES. SOUTHEAST WINDS WILL
INCREASE TODAY AHEAD OF THE TROUGH WITH GUSTS APPROACHING 27 KTS
AT KRST AND 16 KTS AT KLSE. A MID CLOUD DECK...WITH BASES AROUND
6KFT WILL SLIDE ACROSS THE TAF SITES THIS AFTERNOON AND MAY
GENERATE A FEW SPRINKLES AS IT MOVES THROUGH...HOWEVER IT APPEARS
UNLIKELY THAT WE WILL SEE ANY PRECIP OUT OF THIS DECK. RAIN WILL
MOVE INTO KRST AROUND 06Z TONIGHT WITH CLOUD BASES LOWERING TO
AROUND 3500 FT...THEN FALLING THROUGH 9Z TO AROUND 800 FT. AT
KLSE...CLOUD BASES ARE EXPECTED TO FALL TO AROUND 4KFT AROUND 08Z
THEN LOWER TO AROUND 1500 FT BY 12Z. THE IFR MVFR CONDITIONS WILL
IMPROVE TO VFR DURING THE LATE MORNING INTO EARLY AFTERNOON
TOMORROW AS THE SYSTEM EXITS THE REGION.

&&

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

$$

UPDATE...WETENKAMP
SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...WETENKAMP



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