Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 231802
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
102 PM CDT THU OCT 23 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM CDT THU OCT 23 2014

FOR TODAY...A THE 23.00Z MODELS ARE IN GOOD AGREEMENT THAT A SHORT
WAVE WILL BE MOVING THROUGH THE REGION. HOWEVER AS IT DOES...THE
900 TO 800 MB FRONTOGENESIS WEAKENS AND THE 850 MB MOISTURE
TRANSPORT SLIDES EAST OF THE AREA BY LATE THIS MORNING. DUE TO
THIS...KEPT THE HIGHEST RAIN CHANCES FOR THIS MORNING...AND THEN
DRY IT OUT QUICKLY THIS AFTERNOON. SOUNDINGS CONTINUE TO SHOW THAT
DRY AIR WILL MOVE QUICKLY INTO THE AREA IN THE WAKE OF THIS
SYSTEM. AS THIS OCCURS...SKIES WILL QUICKLY CLEAR FROM WEST TO
EAST. THIS WILL LIKELY ALLOW THE PARTIAL SOLAR ECLIPSE TO BE
VISIBLE FOR SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND WESTERN
WISCONSIN. MEANWHILE IN CENTRAL AND NORTH-CENTRAL WISCONSIN...THERE
ARE STILL QUESTIONS ON WHETHER THESE AREAS WILL CLEAR OUT IN TIME.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 355 AM CDT THU OCT 23 2014

FROM FRIDAY INTO FRIDAY EVENING...THE 23.00Z MODELS ARE IN GOOD
AGREEMENT THAT A SHORT WAVE TROUGH WILL BE MOVING OUT OF THE
CENTRAL PLAINS AND EAST THROUGH THE UPPER MISSISSIPPI RIVER
VALLEY. THE NAM HAS THE STRONGEST WAVE AND GENERATES LIGHT RAIN
ACROSS THE AREA THROUGH THIS TIME PERIOD. THE GEM GENERATES RAIN
ACROSS WESTERN WISCONSIN ON FRIDAY EVENING. MEANWHILE THE ECMWF
AND GFS SOUNDINGS SHOW LIMITED MOISTURE SO THEY ARE DRY. SINCE THE
ECMWF USUALLY PERFORMS THE BEST IN THIS TIME FRAME...KEPT THE
FORECAST DRY.

ON SATURDAY...850 MB TEMPERATURES FALL TO 6 TO 8C IN THE WAKE OF A
CANADIAN COLD FRONT. THESE TEMPERATURES CONTINUE TO COOL WITH
EACH PROGRESSIVE MODEL RUN...THUS LOWERED THE TEMPERATURES A
COUPLE MORE OF DEGREES...AND THIS MAY NOT BE ENOUGH YET. IN
ADDITION TO LOWERING TEMPERATURES...SOUNDINGS SHOW THAT A VERY DRY
AIR MASS WILL BE MOVING SOUTHWEST INTO THE AREA DURING THE
AFTERNOON. THE DEW POINT MIX DOWN TOOL SUGGESTS THAT THEY WILL
FALL INTO 25 TO 35 DEGREE RANGE. THIS IS ABOUT 5 TO 8 DEGREES
LOWER THAN THE MOS GUIDANCE. SINCE THE MOS TYPICALLY DOES NOT DO
WELL IN THESE SITUATIONS...WENT WITH THE LOWER DEW POINTS.

FROM SUNDAY AFTERNOON INTO MONDAY MORNING...THE MODELS CONTINUE
TO SHOW A SERIES OF NEGATIVE TILTED SHORT WAVES MOVING OUT AHEAD
OF THE CENTRAL PLAINS LONG WAVE TROUGH. THE MODELS ARE IN GENERAL
AGREEMENT THAT A WARM FRONT WILL MOVE THE AREA ON SUNDAY NIGHT.
STRONG 300K ISENTROPIC LIFT DEVELOPS ALONG AND IN THE ADVANCE OF
THIS FRONT. PRESSURE CONDENSATION DEFICITS DROP TO LESS THAN 10 MB
ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN ON SUNDAY AFTERNOON
AND ACROSS THE ENTIRE AREA ON SUNDAY NIGHT. BOTH THE GFS AND GEM
GENERATE SHOWERS AS SOON AS SUNDAY AFTERNOON AND THEN IT CONTINUES
INTO MONDAY MORNING. MEANWHILE THE ECMWF HAS SUNDAY AFTERNOON DRY
AND INTRODUCES SHOWERS CHANCES FROM SUNDAY NIGHT INTO MONDAY. WITH
THIS BEING THE FIRST TIME THAT IT HAS SHOWED KEPT SUNDAY AFTERNOONDRY
AND THEN KEPT THE SHOWER CHANCES GOING FOR SUNDAY NIGHT AND
MONDAY. ALSO WITH GFS MOST UNSTABLE CAPES RUNNING BETWEEN 500 AND
1000 J/KG...KEPT AN ISOLATED CHANCE OF THUNDERSTORMS IN THE
FORECAST FROM SUNDAY NIGHT INTO MONDAY. THE 1 TO 7 KM SHEAR CLIMBS
ABOVE 50 KNOTS ON SUNDAY NIGHT...SO MAY HAVE TO WATCH THESE STORMS
CLOSELY FOR THE POTENTIAL OF HAIL APPROACHING QUARTERS.

FROM MONDAY NIGHT INTO TUESDAY...THE LONG WAVE TROUGH MOVES EAST
INTO THE REGION. AT THE SAME TIME...A SURFACE LOW WILL BE MOVING
NORTHEAST THROUGH THE UPPER MISSISSIPPI VALLEY THIS BRING ANOTHER
ROUND OF SHOWERS AND STORMS. WHILE THE 0-3 KM MOST UNSTABLE CAPES
CLIMB TO AROUND 500 J/KG...THE 0-6 KM SHEAR IS LESS THAN
40 KNOTS...SO NOT CONCERNED ABOUT ANY SEVERE WEATHER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 102 PM CDT THU OCT 23 2014

STRATUS AND BR WILL PUSH EAST OF THE TAF SITES LATE THIS
AFTERNOON WITH MVFR/IFR CONDITIONS  GIVING WAY TO VFR. A MOIST
AIRMASS OVER THE REGION AND LIGHT SURFACE WINDS WILL SET THE STAGE
FOR DENSE FOG FORMATION TONIGHT. VLIFR CONDITIONS ARE EXPECTED AT
KLSE STARTING AROUND 10Z WITH VISIBILITIES FALLING TO 1/4 MILE IN
FOG. IFR CONDITION ARE EXPECTED AT KRST. WINDS ALOFT SHOULD
PROMOTE MIXING OVER KRST AND HELP TO LIMIT THE FOG. HOWEVER...WITH
THE MOIST AIRMASS IN PLACE AND LIGHT SURFACE WINDS EXPECT
VISIBILITIES TO FALL TO 2SM AROUND 9Z. CONDITIONS  WILL IMPROVE
AFTER 14Z TOMORROW AT BOTH TAF SITES AS MIXING INCREASES.


&&

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

$$

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



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