000
FXUS63 KARX 221752
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1252 PM 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 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1252 PM CDT WED MAY 22 2013

CLOSED LOW LOCATED OVER NORTHEAST IA WILL SLOWLY FILL IN AND
MOVE EAST INTO LOWER MI BY MORNING. PLAN ON IFR/MVFR CLOUD
COVER AND BAND OF SHRA NORTH OF THE LOW TO PERSIST INTO TONIGHT.
THEN LOOK FOR FAIRLY RAPID IMPROVEMENT INTO VFR CATEGORY AROUND
07Z AT KRST AND AROUND 09Z AT KLSE AS DRIER AIR WORKS IN FROM THE
NORTH. HIGH PRESSURE WILL PROVIDE CLEAR SKIES ON THURSDAY WITH
NORTH/NORTHEAST WINDS IN THE 10-20KT RANGE.

&&

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

$$

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