Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 210440
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1140 PM CDT WED MAY 20 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 244 PM CDT WED MAY 20 2015

COOL CONDITIONS TO PREVAIL THROUGH THURSDAY. COLD UPPER LEVEL
TROUGH CONTINUES TO DOMINATE EASTERN CANADA WITH A PARADE OF COLD
AIRMASSES ARRIVING IN OUR AREA. ONE SHORT WAVE WAS WORKING EAST
ACROSS THE REGION CURRENTLY...AND WAS RESULTING IN SOME RAIN
ACROSS IA/IL AND INTO FAR SOUTHERN WI. THAT SHOULD EXIT QUICKLY
YET THIS AFTERNOON. ANOTHER PASSING SHORT WAVE TROUGH WILL SLIDE
THROUGH ON THURSDAY...JUST AS PEAK HEATING WILL BE MAXING OUT.
WITH THE COLD POOL STILL ON PLACE...FEEL THERE WILL BE SOME LIGHT
SHOWERS FOR CENTRAL AND EASTERN WI. INCLUDED SOME SMALL CHANCES.
ELSEWHERE MOISTURE APPEARS TO LIMITED AT THIS POINT. THE BRIEF
PERIOD BETWEEN DISTURBANCES TONIGHT SHOULD ALLOW FOR AT LEAST
PARTIAL CLEARING...HELPING TEMPERATURES TO DIP AGAIN TONIGHT.
THERE MAY BE SOME PATCHY FROST IN THE MORE FAVORED LOCATIONS.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 244 PM CDT WED MAY 20 2015

HIGH PRESSURE WILL DOMINATE THURSDAY NIGHT THROUGH FRIDAY NIGHT AS
THE UPPER RIDGE SHIFTS EAST JUST ENOUGH TO ENCOMPASS THE UPPER
MIDWEST. SOUTHERLY FLOW WILL BEGIN BY SATURDAY...BRINGING A
WARMING TREND...BUT ALSO ADDITIONAL MOISTURE...INSTABILITY...AND
SHORT WAVE TROUGH ENERGY EJECTING OUT OF THE MEAN LONG WAVE OVER
THE WESTERN U.S. ECMWF IS THE SLOWEST WITH THE ENERGY REACHING OUR
AREA...WHILE GFS/NAM WITH SUPPORT FROM OTHER MODELS SUGGESTING AT
LEAST A THREAT FOR CONVECTIVE ACTIVITY ALREADY BY SATURDAY
AFTERNOON. IF THE EC SOLUTION VERIFIES...WE MAY GET WELL INTO
SUNDAY BEFORE THE RAIN ARRIVES. THIS WILL BE THE PRIMARY CONCERN
WITH THE HOLIDAY WEEKEND NEARLY UPON US. FOR NOW HAD TO TAKE A
BLENDED APPROACH WITH NO CLEAR TREND EMERGING YET. WOULD EXPECT
MODELS TO BEGIN TO CONVERGE ON A SOLUTION IN THE NEXT 12-36 HOURS
NOW THAT THE MAIN TROUGH IS MAKING IT ONTO THE WEST COAST. THERE
IS A SECOND PIECE OF ENERGY IN THE MEAN TROUGH AND THE MODELS ALL
DIFFER IN HOW IT WILL PROGRESS FROM THE SOUTHWEST INTO THE CENTRAL
PART OF THE COUNTRY. THUS THE CONFIDENCE IN THE LONGER TERM
FORECAST BEYOND THIS WEEKEND IS ON THE LOW SIDE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1140 PM CDT WED MAY 20 2015

THE CLOUDS HAVE MOVED PAST BOTH SITES THIS EVENING WITH CLEAR
SKIES EXPECTED THROUGH THE OVERNIGHT. A WEAK SHORT WAVE TROUGH
DROPPING OUT OF CANADA WILL MOVE ACROSS THE REGION THURSDAY AND
PUSH A WEAK COLD FRONT THROUGH THE AREA. THE WAVE WILL ONLY BE
STRONG ENOUGH TO PRODUCE A FEW CLOUDS ALONG THE FRONT WITH NO
RAIN EXPECTED FOR THE LOCAL AREA. GOOD LOW LEVEL LAPSE RATES AND A
MIXED LAYER UP THROUGH ABOUT 800 MB THURSDAY AFTERNOON SHOULD
ALLOW FOR SOME GUSTY WINDS TO AROUND 20 KNOTS AT KRST.

&&

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

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...04



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