Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 311135
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
635 AM CDT MON AUG 31 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CDT MON AUG 31 2015

EARLY THIS MORNING...LOW STRATUS HAS QUICKLY DEVELOPED ACROSS
NORTH-CENTRAL IA AND ALONG THE MN/IA BORDER AS WELL AS ACROSS
NORTHERN WI. 31.07Z RAP SHOWS THIS STRATUS FILLING-IN ACROSS MUCH
OF THE FORECAST AREA BY SUNRISE. THESE CLOUDS...COMBINED WITH
BRISK WEST-SOUTHWEST WIND JUST OFF THE SURFACE SHOULD PRECLUDE
WIDESPREAD DENSE FOG...BUT CAN STILL EXPECT SOME AREAS OF REDUCED
VISIBILITY...ESPECIALLY FOR THOSE AREAS THAT REMAIN MOSTLY CLEAR
FOR A LONGER PERIOD.

AS QUICKLY AS THE STRATUS DEVELOPS...MOST HIGH RESOLUTION MODELS
DISSIPATE IT JUST AS QUICKLY BY LATE MORNING AS 15 TO 20 KTS MIX
WITHIN DEEPENING BOUNDARY LAYER. EXPECT A RETURN TO AT LEAST
PARTLY SUNNY SKIES BY EARLY AFTERNOON. PRIMARY IMPACT OF CLOUDS
WILL BE TO SLOW TEMPERATURE RISE THROUGH THE DAY...SO DROPPED
AFTERNOON HIGHS A FEW DEGREES INTO THE LOWER TO MID 80S.

TONIGHT NOT LIKELY TO BE COMPLETELY CLOUD FREE AND WITH 10 TO 20
KTS ATOP NOCTURNAL INVERSION...FOG THREAT SHOULD BE LOWER THAN THE
PAST COUPLE NIGHTS. TEMPERATURES WILL DROP INTO THE MID TO UPPER
60S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 340 AM CDT MON AUG 31 2015

MAIN STORY FOR THE WEEK CONTINUES TO BE WELL ABOVE NORMAL
TEMPERATURES WITH A BROAD 500 HPA RIDGE PARKED ACROSS THE EASTERN
CONUS. WITH 925 HPA TEMPERATURES GENERALLY WOBBLING BETWEEN 24 AND
26 CELSIUS...DAILY HIGHS HIGHS WILL TOP OUT IN THE MID TO UPPER
80S WITH SOME 90 PLUS DEGREE READINGS ALONG AND EAST OF THE MS
RIVER.

WILL KEEP 20-30 PERCENT MODEL CONSENSUS POPS WEDNESDAY NIGHT
THROUGH FRIDAY...BUT THINK MAJORITY OF THE WEEK WILL REMAIN DRY.
MULTIPLE WEAK/ILL-RESOLVED SHORT-WAVES MOVE ACROSS THE REGION IN
SOUTHWEST FLOW ALOFT THAT COULD PROVIDE A FOCUSING MECHANISM FOR
CONVECTION. HOWEVER...AXIS OF MAXIMUM MID-LEVEL MOISTURE TRANSPORT
REMAINS WEST OF THE FORECAST AREA...CLOSER TO THE WESTERN CONUS
TROUGH. DAILY INSTABILITY IS PRESENT WITH ABOVE NORMAL TEMPERATURES/
SURFACE DEWPOINTS IN THE 60S...BUT LARGE SCALE RIDGE SQUASHES ANY
DEEP LAYER SHEAR OF SIGNIFICANCE. FOR NOW...DIFFICULT TO PROVIDE
DETAILS ON TIMING OR COVERAGE IF ANYTHING DOES DEVELOP SO BROAD-
BRUSHED POPS SEEM REASONABLE.

BETTER CHANCES FOR SHOWERS AND THUNDERSTORMS RETURN SATURDAY NIGHT
INTO SUNDAY AS 31.00Z GFS/ECMWF ATTEMPT TO BREAK DOWN EASTERN
CONUS RIDGE BY MOVING A BROAD PACIFIC TROUGH INTO THE ROCKIES/
NORTHERN PLAINS. GFS IS MUCH QUICKER IN DOING SO COMPARED TO THE
SLOWER ECMWF...SO DEFINITE TIMING ISSUES EMERGE. FOR NOW...A
BLENDED APPROACH IS PRUDENT RESULTING IN CHANCE POPS SATURDAY
NIGHT THROUGH THE DAY ON SUNDAY. SHOULD SEE TEMPERATURES FALL BACK
TO MORE SEASONABLE LEVELS ONCE TROUGH PASSES...BUT WHETHER THIS
OCCURS BY SUNDAY OR EARLY NEXT WEEK IS YET TO BE SEEN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 635 AM CDT MON AUG 31 2015

LIGHT SOUTHERLY FLOW IS BRINGING A MORE HUMID AIR MASS INTO THE
REGION THIS MORNING. THIS WAS PRODUCING EXPANSIVE AREA OF LIFR TO
MVFR STRATUS FROM IOWA INTO SOUTHEAST MN/WESTERN AND NORTHERN WI.
THERE WAS ALSO POCKETS OF VSBY BLO 1SM IN BR. EXPECTING
STRATUS/FOG TO LIFT AND SCATTER OUT LATER THIS MORNING AS
STRONGER SOUTH/SOUTHWEST WINDS MIX OUT THE BOUNDARY LAYER. VFR
CONDITIONS THEN EXPECTED AFTER 16Z. SOUTHERLY AIRFLOW WILL LIKELY
PRODUCE MORE STRATUS TONIGHT ACROSS THE AREA...BUT EXTENT IS NOT
CERTAIN AT THIS TIME. LOOKS LIKE IF CEILINGS DID FORM AT KRST/KLSE
IT WOULD LIKELY BE IN MVFR CATEGORY. SHOULD ALSO SEE SOME LIGHT
FOG WITH VSBY IN THE 5-6SM RANGE.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...DAS


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