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000
FXUS63 KARX 220809
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
309 AM CDT WED MAY 22 2013

.SHORT TERM...(TODAY AND FRIDAY)
ISSUED AT 309 AM CDT WED MAY 22 2013

MAIN FORECAST CONCERN ARE PRECIPITATION CHANCES THROUGH TONIGHT...
THEN POSSIBLE PATCHY FROST OVER CENTRAL WISCONSIN THURSDAY NIGHT.

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING UPPER LEVEL LOW OVER
THE NORTHERN PLAINS AND SHORTWAVE TROUGHS ROTATING AROUND THE UPPER
LEVEL LOW. LATEST MOSAIC RADAR INDICATING SCATTERED SHOWERS
EXTENDING FROM LAKE SUPERIOR INTO SOUTHWEST MINNESOTA AND ANOTHER
AREA OF SHOWERS AND THUNDERSTORMS FROM WESTERN ILLINOIS INTO
SOUTHERN LAKE MICHIGAN.

THE 22.00Z GFS/NAM ARE IN GOOD AGREEMENT WITH OVERALL UPPER LEVEL
FLOW THROUGH FORECAST PERIOD. BOTH MODELS ARE IN DECENT AGREEMENT
LIFTING SHORTWAVE TROUGH OVER MISSOURI AND EASTERN KANSAS
INTO SOUTHERN WISCONSIN TODAY. THE 22.00Z GFS/NAM AND 22.03Z RAP ARE
IN AGREEMENT IN INCREASING PV ADVECTION...QG FORCING AND VERTICAL
MOTION OVER THE FORECAST AREA 12-18Z TODAY AND DEVELOP
PRECIPITATION OVER MUCH OF THE FORECAST AREA BY 18Z TODAY.
CONFIDENCE IS INCREASING THE FORECAST AREA WILL SEE PRECIPITATION
DEVELOP OVER FORECAST AREA BY 18Z. THE DETERMINISTIC MODELS INDICATE
0-6KM MOST UNSTABLE CAPE 300-500 J/KG OVER SOUTHEASTERN HALF OF THE
FORECAST AREA AFTER 15Z TODAY. WILL CONTINUE TO MENTION ISOLATED
THUNDERSTORMS.

THE 22.00Z GFS/NAM SUGGEST UPPER LEVEL LOW WEAKENS AND DRIFTS SLOWLY
EAST INTO THE GREAT LAKES REGION...AS AN UPPER LEVEL TROUGH
DIGS OVER EASTERN GREAT LAKES REGION TONIGHT. WITH SURFACE RIDGE
BUILDING INTO SOUTHERN ONTARIO AND THE WESTERN GREAT LAKES REGION...
CLOUDS AND PRECIPITATION WILL DIMINISH FROM NORTH TO SOUTH ACROSS
FORECAST AREA AFTER 06Z THURSDAY.

DRY NORTHEASTERLY FLOW ALOFT DEVELOPS OVER FORECAST AREA THURSDAY.
THE 22.00Z GFS/NAM BUFKIT SOUNDINGS ARE INDICATING FORECAST AREA
MIXING UP TO 825MB BY 21Z. THIS SHOULD ALLOW FOR DEWPOINTS TO FALL
INTO THE MIDDLE 20S TO MIDDLE 30S ACROSS MUCH OF THE FORECAST AREA
THURSDAY AFTERNOON.

NEXT CONCERN IS LOW TEMPERATURES AND PATCHY FROST FRIDAY MORNING...
WITH THE COMBINATION OF SURFACE RIDGE CENTERED AND DRY AIRMASS OVER
FORECAST AREA...TEMPERATURES ARE EXPECTED TO DROP INTO THE MIDDLE
30S ACROSS PORTIONS OF CENTRAL WISCONSIN. PATCHY FROST WILL BE
POSSIBLE ACROSS THIS PART OF THE FORECAST AREA.

.LONG TERM...(FRIDAY NIGHT INTO TUESDAY)
ISSUED AT 309 AM CDT WED MAY 22 2013

MAIN FORECAST CONCERN ARE PRECIPITATION CHANCES THROUGH FORECAST
PERIOD. THE 22.00Z GFS/ECMWF/GEM CONTINUE TO DIFFER ON TIMING OF
SHORTWAVE TROUGHS OVER-TOPPING UPPER LEVEL RIDGE OVER THE CENTRAL
UNITED STATES AND PLACEMENT OF THE SURFACE RIDGE OVER THE
GREAT LAKES REGION. WITH THIS...CONFIDENCE IN FORECAST IS LOW AND
WILL CONTINUE WITH CONSISTENCY OF PRECIPITATION CHANCES THROUGH
FORECAST PERIOD. TEMPERATURES WILL CLIMB INTO THE 60S FOR THE
MEMORIAL DAY WEEKEND AND BE IN THE 70S TUESDAY...AS THE
DETERMINISTIC MODELS INDICATE WARMER AIR ALOFT TO FILTER INTO THE
REGION BY 00Z TUESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1131 PM CDT TUE MAY 21 2013

THE MAIN FOCUS AT THE TAF SITES IS WITH THE POTENTIAL FOR MVFR TO
IFR FLIGHT CONDITIONS AND RAIN SHOWERS AS A LOW PRESSURE SYSTEM
MOVES THROUGH THE REGION. THIS LOW IS CURRENTLY TO THE NORTHWEST
OF THE REGION BUT IS STARTING TO SINK TO THE SOUTHEAST. ALL OF THE
MVFR TO IFR CEILINGS ARE CURRENTLY TO THE NORTH AND WEST OF THIS
LOW AND ARE EXPECTED TO GET INTO THE REGION LATER WEDNESDAY
MORNING. THE EXACT TIMING OF THAT IS IN DOUBT...BUT RST SHOULD SEE
SOME IFR CEILINGS MOVE IN AROUND DAYBREAK WITH MVFR POSSIBLE INTO
LSE AROUND THE SAME TIME. SOME SHOWERS ARE EXPECTED TO DEVELOP IN
THE MORNING HOURS AS WELL AND LAST THROUGH MUCH OF THE DAY BEFORE
DIMINISHING IN THE EVENING HOURS.

&&

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

&&

$$

SHORT TERM.....DTJ
LONG TERM......DTJ
AVIATION.......HALBACH