Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 261729
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1229 PM CDT SAT JUL 26 2014

.UPDATE...
ISSUED AT 748 AM CDT SAT JUL 26 2014

THE 26.06Z DETERMINISTIC AND MESO MODELS CONTINUE TO SUGGEST THAT
THERE WILL BE STRONG 900 TO 500 MB FRONTOGENETIC FORCING MAINLY
SOUTH OF INTERSTATE 90 TODAY. VAD WIND PROFILERS SHOW A 30 TO 45
KNOT CONVERGENCE INTO THE 700 MB FRONT ACROSS SOUTHWEST MINNESOTA.
OVERALL THE HRRR AND A COUPLE /MEMBERS 2 AND 3/ OF THE 26.06Z HOP
WRF SHOW THAT THE PRECIPITATION CURRENTLY OVER EASTERN SOUTH
DAKOTA AND SOUTHWEST MINNESOTA WILL CONTINUE TO SPREAD EAST INTO
THE AREAS MAINLY SOUTH OF INTERSTATE 90. DUE TO THIS...RAISED THE
CHANCES OF SHOWERS UP SIGNIFICANTLY. THERE WILL BE EVEN ENOUGH
INSTABILITY ALOFT FOR ISOLATED THUNDERSTORMS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 320 AM CDT SAT JUL 26 2014

LATEST WATER VAPOR SATELLITE IMAGERY INDICATING UPPER LEVEL CLOSED
LOW OVER SOUTHERN SASKATCHEWAN AND WEST TO EAST ZONAL FLOW OVER
THE NORTHERN PLAINS. WEAK SHORTWAVE TROUGH OVER CENTRAL AND
EASTERN SOUTH DAKOTA EMBEDDED IN WEST TO EAST ZONAL FLOW IS
PRODUCING SHOWERS AND ISOLATED THUNDERSTORMS OVER CENTRAL SOUTH
DAKOTA PER MOSAIC RADAR.

MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES TODAY INTO TONIGHT.

THE 26.00Z GFS/NAM ARE IN GOOD AGREEMENT IN MOVING WEAK IMPULSE OVER
CENTRAL SOUTH DAKOTA INTO THE SOUTHERN PART OF THE FORECAST AREA.
THE 26.00Z GFS/NAM ARE INDICATING ISENTROPIC LIFT AT 315K SURFACE
AND PRODUCE LIGHT QPF ACROSS PARTS OF NORTHEAST IOWA AND SOUTHWEST
WISCONSIN. THE LATEST 26.05Z HRRR IS INDICATING THE SHRA/TSRA OVER
CENTRAL SOUTH DAKOTA TO WEAKEN AND POSSIBLY PRODUCE LIGHT SHOWERS OR
SPRINKLES OVER THE SOUTHERN PART OF THE FORECAST AREA. BUFKIT
SOUNDINGS SHOW QUITE A BIT OF DRY AIRMASS BELOW 700MB OVER THE
SOUTHERN FORECAST AREA. HOWEVER...WITH THE LIFT ASSOCIATED WITH THE
WEAK IMPULSE...THIS MAY PRODUCE AN ISOLATE SHRA/TSRA ACROSS SOUTHERN
FORECAST AREA THIS MORNING INTO THE EARLY AFTERNOON HOURS. HAVE
INTRODUCE A SMALL CHANCE OF PRECIPITATION OVER NORTHEAST IOWA AND
PARTS OF SOUTHWEST WISCONSIN.

UPPER LEVEL CLOSED LOW OVER SOUTHERN SASKATCHEWAN MOVES SOUTH
INTO THE GREAT LAKES REGION TONIGHT. THE 26.00Z GFS/NAM SUGGEST
INCREASING FORCING/LIFT AFTER 06Z OVER NORTHERN PARTS OF THE
FORECAST AREA AND INDICATE ELEVATED CAPE ASSOCIATED WITH UPPER
LEVEL CLOSED LOW. WILL CONTINUE TREND OF PRECIPITATION CHANCES
ACROSS THE NORTHERN PARTS OF THE FORECAST AREA.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 320 AM CDT SAT JUL 26 2014

SUNDAY...THE 26.00Z GFS/NAM CONTINUE TO SHOW DECENT 500-300MB PV
ADVECTION AND DEEP QG FORCING ASSOCIATED WITH THE CLOSED UPPER LEVEL
LOW OVER MUCH OF THE NORTHERN AND EASTERN PART OF THE FORECAST
AREA. CONFIDENCE IS INCREASING THIS AREA WILL SEE SHOWERS AND
POSSIBLY AN ISOLATED THUNDERSTORM.

THE 26.00Z GFS/GEM/ECMWF ARE IN GOOD AGREEMENT DIGGING UPPER LEVEL
TROUGH OVER THE EASTERN UNITED STATES SUNDAY NIGHT INTO FRIDAY. THE
MAIN DIFFERENCE BETWEEN THE MODELS IS TIMING THE VERY WEAK IMPULSES
EMBEDDED IN THE NORTHERLY FLOW ALOFT INTO THE GREAT LAKES REGION.
THE MODELS CONTINUE TO PRODUCE LIGHT QPF OVER PARTS OF THE
FORECAST AREA MAINLY FROM WEDNESDAY INTO FRIDAY. HOWEVER...WITH
VERY WEAK MOISTURE CONVERGENCE AND VERY WEAK IMPULSES EMBEDDED IN
NORTHERLY FLOW. CONFIDENCE IN PRECIPITATION CHANCES IS LOW THROUGH
THIS PERIOD.

TEMPERATURES SUNDAY NIGHT INTO FRIDAY WILL BE UNSEASONABLY COOL
THROUGH MIDDLE OF THE WEEK AND MODERATE TO NEAR NORMAL BY END OF THE
WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1219 PM CDT SAT JUL 26 2014

COMPLEX OF SHOWERS AND STORMS OVER EASTERN SD THIS MORNING HAS
SHIFTED SOUTHEAST INTO WESTERN IA/EASTERN NEB. COOL OUTFLOW
SHOWERS IN MID LEVEL CONVERGENT AREA STRINGING EAST ALONG THE
MN/IA BORDER REGION. LITTLE MORE THAN SPRINKLES AT THE KRST/KLSE
AIRFIELDS...BUT MORE SHOWERS LOOK TO IMPACT KRST FOR THE EARLY
AFTERNOON. COMPLEX SHIFTING SLIGHTLY SOUTH OF EAST SO CONFIDENT IT
WILL MISS KLSE. STILL...LOW CLOUD LINGERING IN THE WEAK FLOW
ENVIRONMENT KEEPING INVERSION IN PLACE. DO FEEL THE LOWER CLOUD
WILL MIX OUT ONCE THE SHOWER AREA PASSES BY MID TO LATE AFTERNOON.
MEANWHILE A NICE SHORT WAVE TROUGH IS MOVING THROUGH SOUTHERN
CANADA NEAR WINNIPEG WILL DROP SOUTHEAST ACROSS MN TONIGHT AND
INTO WI BY SUNDAY. DESPITE MINIMAL MOISTURE AVAILABLE...STRONG
FORCING AND STEEP MID-LEVEL LAPSE RATES LOOK TO FORCE STORMS
DURING THE EVENING/OVERNIGHT HOURS. BUT THESE LOOK TO REMAIN WELL
NORTH AND EAST OF THE TAF LOCATIONS. ONLY IMPACT WILL PERHAPS BE
SOME CLOUD COVER AND A WIND SWITCH TO NORTHWEST. BEHIND THE UPPER
SYSTEM EXPECT LOW LEVEL MOISTURE TO MANIFEST AS CLOUD AND GUSTY
WINDS TOMORROW.

&&

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

$$

UPDATE...BOYNE
SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...MW



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