Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 291728
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1228 PM CDT WED APR 29 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 305 AM CDT WED APR 29 2015

LATEST WATER VAPOR SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE OVER
THE ROCKY MOUNTAINS AND UPPER LEVEL TROUGH OVER SOUTHERN ONTARIO.
LATEST 08Z SURFACE ANALYSIS INDICATES WEAK FRONT EXTENDING FROM
NORTHEAST WISCONSIN INTO EASTERN IOWA WITH THE LATEST FOG SATELLITE
PRODUCT SHOWING PATCHY ALTOCUMULUS CLOUDS OVER EASTERN IOWA AND
SOUTHWEST WISCONSIN.

THE 29.00Z GFS/NAM ARE IN GOOD AGREEMENT IN TRACKING UPPER LEVEL
TROUGH OVER SOUTHERN ONTARIO INTO THE GREAT LAKES REGION THIS
AFTERNOON AND INTO TONIGHT. THE 29.00Z GFS/NAM BUFKIT SOUNDINGS
CONTINUE TO SHOW STEEP LOW LEVEL LAPSE RATES AND WEAK LOW LEVEL
MOISTURE CONVERGENCE WITH THE UPPER LEVEL TROUGH. WILL CONTINUE WITH
SMALL CHANCES OF PRECIPITATION OVER PARTS OF CENTRAL WISCONSIN. THE
29.00Z GFS/NAM INDICATE 100-200 J/KG 0-6KM MOST UNSTABLE CAPE OVER
CENTRAL WISCONSIN...CANNOT RULE THE POSSIBILITY OF A THUNDERSTORM
OR TWO.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 305 AM CDT WED APR 29 2015

UPPER LEVEL TROUGH PUSHES SOUTH AND EAST OF FORECAST AREA AND
SURFACE RIDGE FROM ONTARIO BUILDS INTO EASTERN MINNESOTA AND
WISCONSIN THURSDAY/THURSDAY NIGHT. SLIGHTLY COOLER AIR FILTERS INTO
THE REGION BEHIND THE UPPER LEVEL TROUGH AND UNDERNEATH SURFACE
RIDGE. EXPECT HIGH TEMPERATURES THURSDAY TO BE A COUPLE TO A FEW
DEGREES COOLER THAN TODAY...MAINLY IN THE LOWER TO MIDDLE 60S.

NEXT FORECAST CONCERN ARE PRECIPITATION CHANCES FRIDAY. SHORTWAVE
TROUGH OVER THE PACIFIC NORTHWEST MOVES EAST INTO THE GREAT LAKES
REGION AND BREAKS DOWN UPPER LEVEL RIDGE FRIDAY. THE 29.00Z
GFS/NAM/ECMWF SUGGEST 925-850MB MOISTURE TRANSPORT/CONVERGENCE AND
LIFT IN ASSOCIATION WITH SHORTWAVE TROUGH/SURFACE FRONT. AS THE
SHORTWAVE TROUGH BREAKS DOWN RIDGE...SHORTWAVE TROUGH WEAKENS
ALONG WITH THE LIFT/FORCING. HOWEVER...ENOUGH
LIFT/FORCING/MOISTURE CONVERGENCE OVER FORECAST AREA WILL ALLOW
FOR CHANCES OF SHOWERS ACROSS MUCH OF THE FORECAST AREA FRIDAY.

FOCUS THEN TURNS TO SATURDAY INTO TUESDAY WITH AN ACTIVE WEATHER
PATTERN DEVELOPING AND PRECIPITATION CHANCES POSSIBLE SATURDAY NIGHT
INTO TUESDAY. THE 29.00Z GFS/GEM/ECMWF ARE IN DECENT AGREEMENT IN
DEVELOPING WEST TO EAST ZONAL FLOW ACROSS THE NORTHERN TIER STATES
SATURDAY INTO TUESDAY. MAIN DIFFERENCES BETWEEN THE MODELS CONTINUE
TO BE TIMING OF SHORTWAVE TROUGHS EMBEDDED IN THE WEST TO EAST ZONAL
FLOW AND PLACEMENT OF SURFACE FEATURES ACROSS THE GREAT LAKES REGION
AND THE NORTHERN PLAINS. THE 29.00Z GFS/ECMWF/GEM SHOW DECENT
SOUTHERLY MOISTURE RETURN INTO THE FORECAST AREA SATURDAY NIGHT INTO
TUESDAY. DEPENDING ON PLACEMENT OF SURFACE FEATURES...SHOWERS AND
THUNDERSTORMS ARE LIKELY ACROSS PARTS OF THE FORECAST
AREA...ESPECIALLY SUNDAY NIGHT. WITH DIFFERENCES IN PLACEMENT OF
SURFACE FEATURES...CONFIDENCE REMAINS LOW ON THE EXACT LOCATION OF
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS ACROSS THE FORECAST AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1228 PM CDT WED APR 29 2015

A MID-LEVEL TROUGH SWINGING SOUTHWARD ACROSS THE REGION THIS
AFTERNOON WILL PRODUCE SOME CUMULUS W/BASES AOA 5KFT MAINLY EAST
OF THE MISSISSIPPI RIVER. LOOK FOR NORTH WINDS AROUND 12KT...GUSTING
IN THE 15-20KT RANGE. LOOK FOR THE CUMULUS TO DISSIPATE BY SUNSET
WITH WINDS DIMINISHING AS WELL. ANOTHER TROUGH WILL DROP THROUGH
THE REGION AFTER MIDNIGHT FOR SOME SCATTERED-BROKEN CUMULUS
MAINLY EAST OF THE MISSISSIPPI RIVER WITH BASES AOA 5KFT. THESE
CLOUDS LOOK TO DISSIPATE WITH THE PASSAGE OF THE TROUGH AFTER
14Z. OTHERWISE...PLAN ON LIGHT AND VARIABLE WINDS
TONIGHT...BECOMING NORTH IN THE 5-10KT RANGE AFTER SUNRISE.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...DAS


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