Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 021630
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1130 AM CDT TUE JUN 2 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 322 AM CDT TUE JUN 2 2015

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING SHORTWAVE RIDGE OVER
THE NORTHERN PLAINS AND UPPER LEVEL TROUGH OVER THE PACIFIC
NORTHWEST. LATEST 08Z SURFACE ANALYSIS INDICATING HIGH PRESSURE OVER
LAKE MICHIGAN. SUBSIDENCE UNDERNEATH THE SURFACE HIGH PRESSURE IS
PRODUCING MOSTLY CLEAR SKIES ACROSS THE FORECAST AREA PER INFRARED
SATELLITE IMAGERY.

SURFACE RIDGE OVER LAKE MICHIGAN AND MICHIGAN WILL REMAIN IN CONTROL
OF THE FORECAST AREA TODAY AND PROVIDE DRY WEATHER AND SEASONABLE
TEMPERATURES.

TONIGHT...THE 02.00Z GFS/NAM/ECMWF SHOW A COUPLE OF SHORTWAVE
TROUGHS...EMBEDDED IN THE SOUTHWESTERLY FLOW ALOFT OVER THE ROCKY
MOUNTAINS...FLATTEN UPPER LEVEL RIDGE OVER THE NORTHERN PLAINS
TONIGHT. THE FIRST IMPULSE PUSHES INTO WESTERN MINNESOTA/NORTHWEST
IOWA AFTER 06Z WEDNESDAY. THE 02.00Z GFS/NAM INDICATE DECENT
MOISTURE CONVERGENCE AND FORCING WITH THE IMPULSE...AND THE MODELS
SHOW THE EASTERN PERIPHERY OF FORCING/LIFT/MOISTURE CONVERGENCE
MOVES INTO THE WESTERN PARTS OF THE FORECAST AREA 09-12Z
WEDNESDAY. THE 02.00Z GFS/NAM SUGGEST A SLIGHTLY FASTER SOLUTION
THAN PREVIOUS RUNS PER DPROG/DT. THERE IS POSSIBILITY...THE
VERTICAL MOTION/MOISTURE CONVERGENCE COULD MOVE INTO THE WESTERN
PARTS OF THE FORECAST AREA BEFORE 09Z WEDNESDAY. AT THIS
TIME...TRENDED PRECIPITATION CHANCES TO ENTER WESTERN PARTS OF
FORECAST AREA AROUND 09Z WEDNESDAY.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 322 AM CDT TUE JUN 2 2015

AS SHORTWAVE TROUGH PROGRESSES EASTWARD AND RUNS INTO A WEAK
SHORTWAVE RIDGE OVER THE GREAT LAKES REGION...SHORTWAVE TROUGH
WEAKENS WEDNESDAY INTO WEDNESDAY NIGHT. WITH THE SHORTWAVE TROUGH
WEAKENING...THE 02.00Z GFS/NAM/ECMWF ARE IN AGREEMENT THE
LIFT/FORCING/MOISTURE TRANSPORT/CONVERGENCE ALSO WEAKENS OVER THE
FORECAST AREA WEDNESDAY/WEDNESDAY NIGHT. HOWEVER...THE 02.00Z MODELS
SUGGEST ENOUGH LIFT/MOISTURE CONVERGENCE OVER THE FORECAST AREA WILL
ALLOW FOR LINGERING SHOWERS AND THUNDERSTORMS WEDNESDAY INTO
WEDNESDAY NIGHT. WITH THE BETTER AGREEMENT BETWEEN THE 02.00Z
GFS/NAM/ECMWF DURING THIS TIME FRAME...HAVE INCREASED PRECIPITATION
CHANCES ACROSS THE FORECAST AREA.

NEXT CONCERNS ARE SHOWERS AND THUNDERSTORMS CHANCES THURSDAY INTO
THURSDAY NIGHT. DIFFERENCES OCCUR BETWEEN THE 02.00Z
GFS/NAM/ECMWF...AS THE NAM CONTINUES TO BE MORE PROGRESSIVE WITH
THE SURFACE FRONT EXITING THE FORECAST AREA BY 18Z THURSDAY.
WHILE...THE GFS LAGS UP THE SURFACE FRONT OVER SOUTHERN MINNESOTA
AND NORTHERN IOWA THURSDAY. ECMWF STALLS SURFACE FRONT OVER
SOUTHWEST WISCONSIN AND NORTHEAST IOWA. THE 02.00Z GFS/NAM/ECMWF
ALL SUGGEST SOME MOISTURE CONVERGENCE AND WEAK FORCING ALONG THE
SURFACE FRONT...DEPENDING ON PLACEMENT...WILL KEEP SMALL
PRECIPITATION CHANCES ACROSS MUCH OF THE FORECAST AREA THURSDAY.

THE 02.00Z GFS/NAM/ECMWF EJECT ANOTHER STRONGER SHORTWAVE TROUGH OUT
OF THE WESTERN UPPER LEVEL TROUGH INTO THE UPPER MIDWEST THURSDAY
NIGHT. THE 02.00Z MODELS CONTINUE TO SHOW DIFFERENCES ON
PLACEMENT OF SURFACE FRONT AND DEVELOPMENT OF SURFACE LOW OVER
NEBRASKA AND KANSAS. THE 02.00Z GFS/NAM/ECMWF INDICATE DECENT
MOISTURE TRANSPORT AND CONVERGENCE ALONG SURFACE FRONT. WITH THE
DIFFERENCES ON PLACEMENT OF SURFACE FRONT BETWEEN THE
NAM/GFS/ECMWF...LEANED TOWARD A MIDDLE SOLUTION OF THE ECMWF...AS
THE GFS FARTHER WEST/NAM FARTHER EAST/ECMWF IN THE MIDDLE WITH
PLACEMENT OF SURFACE/UPPER LEVEL FEATURES. AT THIS TIME
FOCUSED...PRECIPITATION CHANCES ACROSS THE EASTERN AND SOUTHERN
FORECAST AREAS THURSDAY NIGHT.

SEVERE RISK REMAINS LOW WEDNESDAY INTO THURSDAY NIGHT...DUE TO
LIMITED INSTABILITY AND WEAK SHEAR ACROSS THE FORECAST AREA.

MAIN FORECAST CONCERNS FRIDAY THROUGH MONDAY ARE PRECIPITATION
CHANCES THROUGH MUCH OF THE PERIOD. THE 02.00Z GFS/ECMWF/GEM ARE IN
GOOD AGREEMENT IN MOVING SHORTWAVE TROUGH/SURFACE LOW INTO THE OHIO
RIVER VALLEY AND SOUTH OF THE FORECAST AREA FRIDAY NIGHT INTO
SATURDAY. THEN...DIFFERENCES OCCUR BETWEEN THE 02.00Z GFS/ECMWF
WITH TIMING AND STRENGTH OF UPPER LEVEL TROUGH OVER THE GREAT
LAKES REGION SATURDAY NIGHT INTO MONDAY...WITH THE ECMWF MUCH
STRONGER WITH UPPER LEVEL TROUGH THAN THE GFS. THE 02.00Z
GFS/ECMWF SHOW DECENT VERTICAL MOTION/MOISTURE CONVERGENCE WITH
ASSOCIATED UPPER LEVEL TROUGH/SURFACE FEATURES TO PRODUCE SHOWER
AND THUNDERSTORM CHANCES ACROSS THE FORECAST AREA SATURDAY NIGHT
INTO MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1130 AM CDT TUE JUN 2 2015

PRIMARY CONCERN FOR AVIATION IS ONSET OF RAIN CHANCES WEDNESDAY
MORNING. MODELS OFFER SIMILAR SOLUTIONS THAT RAIN WILL SPREAD OVER
THE AIRFIELDS...BUT PER USUAL DIFFER ON THE DETAILS WHICH AFFECTS
TIMING. FEEL RAIN COMPLEX TO THE WEST MAY SEND DISSIPATING
REMNANTS ACROSS SOUTHERN MN BY MORNING. BEST SUPPORT AND FOCUS
REMAINS WEST SO DO NOT ANTICIPATE LARGE STORMS OR EVEN A LARGE
AREA OF SHOWERS TO MAKE IT TO KRST...BUT DID OPT TO INCLUDE VCSH
IN CASE LIGHT SHOWERS DO GET CLOSE. EXPECT A LOWER AREA OF CU/SC
TO INVADE SO INCLUDED THAT...BUT SHOULD REMAIN VFR. LATER SHIFTS
WILL NEED TO MONITOR EVOLUTION OF THE SITUATION TO SEE OF RAIN
CHANCES ARE WARRANTED IN THE TAFS MORE THAN VCSH EARLIER IN THE
DAY. BEST RAIN CHANCES APPEAR TO REMAIN AFTER THE END OF THE
CURRENT VALID TAF PERIOD...WITH HIGHEST CHANCES DURING THE
WEDNESDAY NIGHT TIME FRAME.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...MW


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