Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 251151
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
651 AM CDT FRI JUL 25 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 303 AM CDT FRI JUL 25 2014

LATEST MOSAIC RADAR SHOWING A LINE OF SHOWERS AND THUNDERSTORMS
DEVELOPING FROM WEST CENTRAL MINNESOTA INTO CENTRAL IOWA EARLY
THIS MORNING. THE SHOWERS AND THUNDERSTORMS IS ON THE NOSE OF THE
LOW LEVEL JET/MOISTURE TRANSPORT AND CONVERGENCE IN THE 925-850MB
LAYER PER THE LATEST 25.03 RAP AND 25.00Z GFS/NAM.

THE 25.00Z NAM/GFS AND THE 25.03Z RAP INDICATE THE NOSE OF LOW LEVEL
JET/MOISTURE TRANSPORT AND CONVERGENCE WILL BE POINTED DIRECTLY INTO
MAINLY THE SOUTHERN FORECAST AREA THROUGH 18Z TODAY. HOWEVER...THE
MODELS SHOW THE CORFIDI VECTORS/UPWIND PROPAGATION VECTORS TO MOVE
THE SHOWERS AND THUNDERSTORMS SOUTH TO SOUTHEAST AND IMPACT MAINLY
THE SOUTHERN FORECAST AREA TODAY. THIS IS EVIDENT WITH MOVEMENT OF
THE THUNDERSTORMS EARLY THIS MORNING PER THE LATEST MOSAIC RADAR.
AT THIS TIME...SEVERE WEATHER THREAT LOOKS TO BE MINIMAL WITH THE
THUNDERSTORMS...AS THE LATEST 25.00Z NAM AND 25.03Z RAP SHOW 0-6KM
MOST UNSTABLE CAPE LESS THAN 1000 J/KG AND THE BETTER ELEVATED
INSTABILITY TO BE WEST OF THE DEVELOPING THUNDERSTORM
ACTIVITY/NOSE OF THE LOW LEVEL JET/MOISTURE CONVERGENCE. THE
MODELS SHOW PRECIPITABLE WATERS APPROACHING 1.5 TO 2 INCHES LATE
THIS MORNING. SOME OF THE THUNDERSTORMS COULD PRODUCE LOCAL HEAVY
RAINFALL.

THE LOW LEVEL JET/MOISTURE CONVERGENCE WEAKENS AND MOVES EAST OF
THE FORECAST AREA THIS AFTERNOON AND EVENING AND WILL ALLOW FOR
SKIES AND PRECIPITATION CHANCES TO DIMINISH WEST TO EAST ACROSS
THE FORECAST AREA.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 303 AM CDT FRI JUL 25 2014

NEXT CONCERN IS CLOSED UPPER LEVEL LOW OVER SOUTHERN SASKATCHEWAN
AND ALBERTA SLOWLY MEANDERS OVER THE UPPER GREAT LAKES REGION
SATURDAY NIGHT INTO SUNDAY. THE 25.00Z GFS/NAM SHOW MUCH STRONGER
AND DEEPER QG FORCING IN ASSOCIATION WITH THE UPPER LEVEL LOW. BEST
FORCING INCREASES OVER THE NORTHERN PORTIONS OF FORECAST AREA LATE
SATURDAY NIGHT INTO SUNDAY...HENCE THE BETTER PRECIPITATION CHANCES.
THE NAM/GFS BUFKIT SOUNDINGS INDICATE WEAK ELEVATED CAPE MAINLY
ABOVE 800MB BY 18Z SUNDAY AND 0-6KM MOST UNSTABLE CAPE OF 500-1000
J/KG EAST OF THE MISSISSIPPI RIVER. WILL CONTINUE TO MENTION
ISOLATED THUNDERSTORMS SATURDAY NIGHT INTO SUNDAY.

SUNDAY NIGHT THROUGH THURSDAY...NORTHERLY FLOW DEVELOPS OVER THE
UPPER GREAT LAKES REGION PER LATEST 25.00Z GFS/ECMWF/GEM. MAIN
CONCERN IS TIMING OF THE WEAK SHORTWAVE TROUGHS EMBEDDED IN THE
NORTHERLY FLOW ALOFT AND PRODUCE SMALL PRECIPITATION CHANCES ACROSS
PARTS OF THE FORECAST AREA TUESDAY...WEDNESDAY NIGHT INTO
THURSDAY. TEMPERATURES MONDAY THROUGH THURSDAY WILL CONTINUE TO BE
UNSEASONABLY COOL ACROSS FORECAST AREA...AS THE 25.00Z GEFS
INDICATE 850MB TEMPERATURE ANOMALIES IN THE MINUS 0.5 TO MINUS 1.5
DEGREES CELSIUS RANGE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 650 AM CDT FRI JUL 25 2014

A SHORT WAVE TROUGH WILL PRODUCE SHOWERS AND THUNDERSTORMS AT BOTH
TAF SITES THIS MORNING. THIS PRECIPITATION MAY BRIEFLY REDUCE
VISIBILITIES AND CEILINGS TO MVFR. THE HRRR HAS BEEN HANDLING
THIS PRECIPITATION WELL EARLY THIS MORNING...SO FOLLOWED IT WHEN
MAKING THE TAFS. WITH THIS IN MIND...THE PRECIPITATION WILL END AT
KRST BY 25.14Z AND AT KLSE BY 25.15Z.

FOR TONIGHT...THE LAMP GUIDANCE IS SUGGESTING THAT FOG WILL REDUCE
VISIBILITIES TO MVFR AT KRST AFTER 26.06Z...AND LESS THAN A MILE
AT KLSE AFTER 26.08Z. I AM A BIT SKEPTICAL OF THIS SINCE THERE HAS
BEEN VERY LITTLE FOG OVER THE DAKOTAS AND WESTERN MINNESOTA EARLY
THIS MORNING...AND THE SOUNDINGS SHOW SOME MIXING BELOW 2K FEET.
AS A RESULT...JUST INTRODUCED SOME MVRF FOG AT THIS TIME.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...BOYNE



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