Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 201705
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1205 PM CDT MON OCT 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 312 AM CDT MON OCT 20 2014

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING SHORTWAVE TROUGH
EMBEDDED IN NORTHWEST FLOW ALOFT OVER EASTERN MINNESOTA AND WESTERN
WISCONSIN AND UPPER LEVEL RIDGE OVER THE ROCKY MOUNTAINS. LATEST FOG
SATELLITE PRODUCT INDICATING STRATUS/CUMULUS DECK CLOUDS EXTENDING FROM
NORTHEAST MINNESOTA INTO ONTARIO CANADA. THIS IS IN RESPONSE TO
LOW LEVEL MOISTURE AT 925-850MB PER THE 20.00Z NAM.

MAIN FORECAST CONCERNS TODAY AND TONIGHT ARE CLOUD TRENDS.

THE LATEST 20.00Z GFS/NAM ARE IN DECENT AGREEMENT IN DIGGING
UPPER LEVEL TROUGH OVER THE EASTERN UNITED STATES TODAY INTO
TONIGHT. THE 20.00Z GFS/NAM INITIALIZE THE STRATUS/CUMULUS DECK
WELL PER LATEST FOG SATELLITE PRODUCT AND THE 925-850MB RELATIVE
HUMIDITY FIELDS. BOTH OF THE MODELS ADVECT THIS MOISTURE/CLOUDS
MAINLY ALONG AND EAST OF THE MISSISSIPPI RIVER TODAY. THEN THE CONCERN
IS WHEN THE MOISTURE/CLOUDS ERODES EAST OF THE MISSISSIPPI RIVER
TONIGHT. THE 20.00Z NAM INDICATES THE 925-850MB MOISTURE
EVAPORATES...AS SHORTWAVE TROUGH DIGS OVER THE OHIO RIVER VALLEY
AND RIDGING ALOFT BUILDS INTO EASTERN MINNESOTA AND WESTERN
WISCONSIN BY 12Z TUESDAY. EXPECT THE CLOUDS TO DIMINISH EAST OF
THE MISSISSIPPI RIVER TONIGHT.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 312 AM CDT MON OCT 20 2014

SURFACE/UPPER LEVEL RIDGE DOMINATES THE UPPER MIDWEST AND GREAT
LAKES REGION TUESDAY INTO WEDNESDAY. MAIN CONCERN WILL BE POTENTIAL
FOR FOG IN RIVER VALLEYS TUESDAY NIGHT/WEDNESDAY MORNING. SURFACE
RIDGE AXIS IS EXPECTED TO BUILD OVER WESTERN WISCONSIN BY 06Z
WEDNESDAY AND ALLOW WINDS TO BECOME CALM OR VERY LIGHT AND SOUTHERLY
OVER THE FORECAST AREA. THE LATEST 20.00Z NAM/GFS BUFKIT SOUNDINGS
AT LA CROSSE WISCONSIN INDICATES OVER 10 KNOTS OF WIND AT AND ABOVE
THE SURFACE AT 200-400 FEET. THIS STRONG OF WIND MAY INHIBIT FOG
FORMATION IN THE RIVER VALLEYS AND AT THIS TIME WILL CONTINUE WITH
PATCHY FOG IN THE RIVER VALLEYS.

FOCUS THEN TURNS TO WEDNESDAY NIGHT INTO THURSDAY...THE LATEST
20.00Z GFS/NAM/GEM/ECMWF CONTINUE TO EJECT A PIECE OF ENERGY INTO
THE UPPER MIDWEST AND GREAT LAKES REGION. THE 20.00Z
GFS/NAM/ECMWF/GEM SHOW DIFFERENCES IN TIMING OF THE SHORTWAVE
TROUGH PUSHING INTO THE NORTHERN PLAINS AND UPPER MIDWEST...AS THE
20.00Z GFS/ECMWF ARE SLIGHTLY MORE PROGRESSIVE THAN THE 20.00Z
NAM/GEM. THIS IS ALSO EVIDENT WITH THE DPROG/DT OF THE GFS/ECMWF
INDICATING A SLIGHTLY FASTER SOLUTION THE PAST SEVERAL RUNS. ALL
THE MODELS SHOW INCREASING LOW LEVEL MOISTURE/LIFT/CONVERGENCE
OVER THE WESTERN PORTION OF THE FORECAST AREA AFTER 06Z THURSDAY.
THE SHORTWAVE TROUGH AND ASSOCIATED LIFT WEAKENS OVER THE FORECAST
AREA THURSDAY...AS THE SHORTWAVE TROUGH ENCOUNTERS RIDGING ALOFT
OVER THE GREAT LAKES REGION. FOR NOW...THE HIGHER CHANCES OF
PRECIPITATION WILL OCCUR ACROSS THE WESTERN PORTIONS OF THE
FORECAST AREA WITH LOWER CHANCES OVER THE EASTERN PORTIONS OF THE
FORECAST AREA.

FRIDAY INTO NEXT WEEKEND...MAIN FORECAST CONCERNS ARE TEMPERATURES
THROUGH PERIOD. THE 20.00Z GFS/GEM/ECMWF ARE IN GOOD AGREEMENT IN
BUILDING UPPER LEVEL RIDGE INTO THE CENTRAL UNITED STATES AND
DIGGING UPPER LEVEL TROUGH OVER THE WESTERN UNITED STATES. THE
20.00Z GFS/ECMWF SHOW MINOR DIFFERENCES IN THE STRENGTH OF THE
UPPER LEVEL TROUGH OVER THE WESTERN UNITED STATES AND RIDGE OVER
THE CENTRAL UNITED STATES...THIS WILL HAVE MINOR IMPACTS ON HOW
FAR NORTH THE WARMER AIR ALOFT ADVECTS NORTHWARD INTO THE GREAT
LAKES REGION. BOTH MODELS SUGGEST STRONG WARM AIR ADVECTION INTO
THE FORECAST AREA THIS WEEKEND...WITH 850MB TEMPERATURES WARMING
UP TO PLUS 18 DEGREES CELSIUS OVER PARTS OF THE SOUTHERN FORECAST
AREA BY 18Z SUNDAY. TEMPERATURES FRIDAY INTO NEXT WEEKEND ACROSS
FORECAST THE AREA WILL BE ABOVE NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1205 PM CDT MON OCT 20 2014

EXTENSIVE VFR CUMULUS FIELD ALONG AND EAST OF THE MISSISSIPPI
RIVER EARLY THIS AFTERNOON IN CYCLONIC FLOW ALOFT. EXPECT THIS
CUMULUS TO DISSIPATE WITH SKIES BECOMING SKC THIS EVENING AS A
RIDGE OF HIGH PRESSURE BUILDS IN FROM THE PLAINS. PLAN ON VFR/SKC
CONDITIONS THROUGH TUESDAY AS THE RIDGE CONTINUES TO BUILD
OVERHEAD.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...DAS


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