Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 180828
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
328 AM CDT SAT OCT 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 237 AM CDT SAT OCT 18 2014

OVERALL A VERY QUIET WEEK SETTING UP ACROSS THE UPPER MISSISSIPPI
RIVER VALLEY. 18.00Z GLOBAL MODELS ARE IN GOOD AGREEMENT THROUGH
23.00Z...DIVERGING THEREAFTER WITH THE SPEED AND LOCATION OF A MID-
WEEK EASTERN PACIFIC SHORT-WAVE. WILL USE A BLENDED MODEL SOLUTION
FOR THIS FORECAST PACKAGE.

FOR TODAY...THE MID-LEVEL TROUGH ACROSS THE EASTERN GREAT LAKES
WILL MOVE INTO NEW ENGLAND ALLOWING SURFACE HIGH PRESSURE TO BUILD
ACROSS THE REGION. WINDS WILL BECOME LIGHT AND VARIABLE BY MID-
LATE AFTERNOON. UPSTREAM OBSERVATIONS SUGGEST CLOUDS WILL BE SLOW
TO DISSIPATE THIS MORNING...BUT BOTH THE RAP AND HRRR HIGH
RESOLUTION GUIDANCE SHOW CLEARING SKIES BY LATE AFTERNOON. AS A
RESULT...DELAYED CLEARING IN THE SKY GRIDS THROUGH THE MORNING
HOURS WITH MOSTLY CLEAR CONDITIONS BY 19.00Z. TEMPERATURES TODAY
WILL BE VERY SIMILAR TO YESTERDAY WITH HIGHS IN THE 50S.

SURFACE PRESSURE GRADIENT STRENGTHENS OVERNIGHT AS HIGH PRESSURE
MOVES QUICKLY TO THE EAST. DESPITE CLEAR SKIES...LIGHT SOUTHERLY
RETURN FLOW WILL DEVELOP AND WITH NEAR SURFACE WINDS FROM 10 TO
15 KTS...DO NOT EXPECT SIGNIFICANT VALLEY FOG FORMATION. LACK OF
CLOUD COVER AND OVERALL DRY AIR MASS WILL ALLOW TEMPERATURES TO
DROP INTO THE UPPER 20S TO MID 30S.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 237 AM CDT SAT OCT 18 2014

500 TO 300 HPA PV ADVECTION INCREASES ON SUNDAY AND SUNDAY NIGHT
AHEAD OF THE NEXT SHORT-WAVE. MOISTURE RATHER LIMITED ALONG MID-
LEVEL WARM FRONT WITH BEST CHANCES FOR PRECIPITATION FARTHER NORTH
CLOSER TO THE SURFACE LOW RIDING ALONG THE INTERNATIONAL BORDER.
WILL KEEP A SLIGHT CHANCE MENTION ACROSS TAYLOR/CLARK COUNTIES...
BUT EXPECT DRY CONDITIONS ELSEWHERE. SUNDAY WILL BE MOSTLY CLOUDY...
BUT WITH INCREASING THERMAL PROFILE...TEMPERATURES WILL CLIMB INTO
THE UPPER 5OS TO LOWER 60S. SOUTHWEST WINDS WILL INCREASE BY
AFTERNOON...GUSTING AT TIMES TO 25 MPH.

MONDAY THROUGH WEDNESDAY WILL BE MOSTLY SUNNY AND DRY AS SURFACE
HIGH PRESSURE DRIFTS SLOWLY ACROSS THE UPPER MIDWEST. RIDGE AXIS
CUTS RIGHT DOWN THE MIDDLE OF THE FORECAST AREA BY 21.12Z (TUESDAY
MORNING)...SO FOG POTENTIAL IS HIGHER...BUT CERTAINTY NOT GREAT
ENOUGH TO MENTION IN CURRENT FORECAST. LITTLE DAY-TO-DAY VARIATION
IN TEMPERATURES CAN BE EXPECTED WITH HIGHS IN THE 50S AND LOWS IN
THE 30S TO LOWER 40S.

BY THURSDAY...THE ECMWF RAPIDLY BREAKS DOWN THE 500 HPA RIDGE
ALLOWING THE NEXT SHORT-WAVE TO CRUISE ACROSS THE REGION BRINGING
A QUICK SHOT OF RAIN. THE GFS...HOWEVER MAINTAINS THE RIDGE
ACROSS THE GREAT LAKES...SLOWING THE WAVE/S EASTWARD PROGRESS AND
KEEPING RAIN WEST OF THE FORECAST AREA UNTIL THURSDAY NIGHT. THE
GFS SOLUTION ALSO WEAKENS THE WAVE RESULTING IN LESS RAINFALL. FOR
NOW...WILL KEEP LOW-END POPS ACROSS THE WESTERN HALF OF THE
FORECAST AREA ON THURSDAY. HEIGHTS RISE THURSDAY...ALLOWING
TEMPERATURES TO REACH BACK INTO THE LOWER 60S. BY FRIDAY...
850 HPA TEMPERATURES RANGE FROM +12 TO +15 C WHICH SHOULD RESULT
IN SURFACE VALUES INTO THE MID 60S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY TONIGHT)
ISSUED AT 1110 PM CDT FRI OCT 17 2014

VFR CLOUDS DID WORK ACROSS THE TAF SITES LATE THIS EVENING...WITH
THE CLEAR SPOT IN THE CLOUD SHIELD SLIDING SOUTH...JUST WEST OF
KRST. MORE 1.5-2.5 KFT CIGS ARE SITUATED JUST NORTH OF THE CLEAR
SLOT...WITH SATELLITE/OBS TRENDS SPREADING THESE BACK ACROSS THE TAF
SITES AROUND 06Z.

RH FIELDS AND BUFKIT SOUNDINGS FAVOR KEEPING THE LOW SATURATION-MVFR
CIGS IN THROUGH SAT MORNING...WITH SUBSIDENCE POST A DEPARTING
SHORTWAVE TROUGH AND WEAK HIGH PRESSURE CLEARING THE SKIES SAT
AFTERNOON.

WINDS WILL DECOUPLE WITH SUNDOWN SAT EVENING...AND WITH CLEAR
SKIES...SEE SOME POTENTIAL FOR RIVER VALLEY FOG AT KLSE. A COUPLE
DETRACTORS - SOME HIGH CLOUDS COULD BE SPILLING IN FROM THE WEST
OVERNIGHT AHEAD OF A SHORTWAVE TROUGH...AND LOW LEVEL WINDS INCREASE
OVERNIGHT AS THE HIGH SLIPS SOUTHEAST. ITS NOT A PERFECT SETUP FOR
FG...BUT ENOUGH ELEMENTS THAT IT WILL HAVE TO BE WATCHED. COULD JUST
BE SOME THIN STRATUS/FOG DEVELOPS ON THE RIVER AND STAYS THERE.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION.....RIECK


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