Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 161719
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1219 PM CDT TUE SEP 16 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 303 AM CDT TUE SEP 16 2014

LATEST 07Z SURFACE ANALYSIS SHOWS HIGH PRESSURE CENTERED OVER
WESTERN IOWA. SUBSIDENCE UNDERNEATH HIGH PRESSURE IS ALLOWING FOR
MOSTLY CLEAR SKIES ACROSS THE AREA PER LATEST SATELLITE IMAGERY.
WITH THE CLEAR SKIES AND LIGHT WINDS ACROSS THE FORECAST AREA...FOG
HAS FORMED ALONG THE WISCONSIN RIVER VALLEY...PARTS OF CENTRAL
WISCONSIN AND PARTS OF SOUTHEAST MINNESOTA.

MAIN FORECAST CONCERNS ONCE AGAIN IS FOG POTENTIAL TONIGHT IN RIVER
VALLEYS AND CENTRAL WISCONSIN. TODAY...SURFACE RIDGE DOMINATES THE
REGION. SUBSIDENCE UNDER SURFACE WILL PROVIDE MOSTLY SUNNY SKIES AND
SEASONABLE TEMPERATURES. THE LATEST 16.00Z GFS BUFKIT SOUNDINGS
CONTINUE TO SHOW WINDS LESS THAN 10 KNOTS UP TO 1000 FEET AND
DEVELOP INVERSION. ONCE AGAIN...WITH THE CLEAR SKIES AND LIGHT
WINDS...EXPECT FOG TO DEVELOP AFTER 08Z IN RIVER VALLEYS AND THE
CENTRAL WISCONSIN.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 303 AM CDT TUE SEP 16 2014

FOG POTENTIAL CONTINUES FOR WEDNESDAY NIGHT INTO THURSDAY MORNING IN
RIVER VALLEYS...AS THE 16.0ZZ GFS/ECMWF/NAM CONTINUE SHOW HIGH
PRESSURE DOMINATING THE UPPER MIDWEST AND GREAT LAKES REGION.
HOWEVER...THE 16.00Z GFS/NAM/ECMWF INDICATE A VERY WEAK FRONT TO
PUSH SOUTH INTO CENTRAL WISCONSIN WEDNESDAY EVENING/WEDNESDAY
NIGHT. THIS WEAK FRONT PRODUCES A THIN LAYER OF MOISTURE/CLOUDS
AROUND 850MB ACROSS THE CENTRAL INTO NORTH CENTRAL WISCONSIN
WEDNESDAY NIGHT(00-12Z THURSDAY). THIS MOISTURE/CLOUDS  WILL
INHIBIT ANY FOG FORMATION OVER CENTRAL WISCONSIN. THE 16.00Z NAM
IS MORE PROGRESSIVE AND ADVECTS THE MOISTURE/CLOUDS FARTHER WEST
AND POTENTIALLY TO THE MISSISSIPPI RIVER. FOR NOW...WILL CONTINUE
WITH THE MENTION OF PATCHY TO AREAS OF FOG IN THE RIVER
VALLEYS...HOWEVER WILL CONTINUE TO MONITOR IF STRATUS/CLOUDS
DEVELOP OVER CENTRAL WISCONSIN.

MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES THURSDAY NIGHT INTO
SATURDAY NIGHT. THE LATEST 16.00Z GFS/GEM/ECMWF ARE TRENDING TOWARDS
A SLOWER AND FARTHER WEST/NORTH SOLUTIONS WITH THE FIRST IMPULSE TO
IMPACT THE AREA THURSDAY NIGHT AND FRIDAY PER DPROG/DT. THE MODELS
ARE SUGGESTING THE LIFT/MOISTURE TRANSPORT AND CONVERGENCE TO BE
FOCUSED OVER CENTRAL MINNESOTA AND NORTHERN WISCONSIN THURSDAY NIGHT
INTO FRIDAY...AS SHORTWAVE RIDGE REMAINS IN CONTROL OVER SOUTHERN
MINNESOTA AND SOUTHERN WISCONSIN. THIS COULD RESULT IN DRY
WEATHER CONDITIONS ACROSS THE SOUTHERN PART OF THE FORECAST AREA
AND BETTER PRECIPITATION CHANCES OVER THE NORTHERN HALF FRIDAY.
THEN FOCUS TURNS TO FRIDAY NIGHT INTO SATURDAY...AS THE 16.00Z
GFS/GEM/ECMWF ARE IN AGREEMENT DIGGING UPPER LEVEL TROUGH OVER THE
UPPER MIDWEST AND PUSHING SHORTWAVE ENERGY OVER THE FORECAST AREA.
THE MODELS INDICATE DECENT MOISTURE TRANSPORT/CONVERGENCE AND LIFT
ASSOCIATED WITH SHORTWAVE TROUGH/SURFACE COLD FRONT FRIDAY NIGHT
INTO SATURDAY. WILL CONTINUE WITH HIGHER PRECIPITATION CHANCES
DURING THIS TIME FRAME. THE 16.00Z GFS CONTINUES TO SHOW ENOUGH
INSTABILITY AND SHEAR FRIDAY NIGHT INTO SATURDAY...TO POTENTIALLY
HAVE A FEW OF THE THUNDERSTORMS BECOME SEVERE.

SURFACE RIDGE BUILDS INTO THE NORTHERN PLAINS AND THE GREAT LAKES
REGION LATE SUNDAY INTO MONDAY AND PROVIDE DRY WEATHER CONDITIONS
ACROSS THE FORECAST AREA. COOLER AIR WILL FILTER IN BEHIND THE
SURFACE FRONT/SHORTWAVE TROUGH AND TEMPERATURES SHOULD BE NEAR
NORMAL BY MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1219 PM CDT TUE SEP 16 2014

AREA UNDER HIGH PRESSURE WITH LIGHT WINDS AND MAINLY CLEAR SKIES.
ONLY A FEW CUMULUS TODAY. MAIN FORECAST CONCERN FOR THE TAF PERIOD
IS POTENTIAL FOR VALLEY FOG AGAIN TONIGHT AT KLSE. SITUATION IS
DIFFERENT THAN LAST NIGHT`S GOOD EVENT. MOISTURE IS LESS...
FORECAST T/TD DEPRESSION IS NEARLY 10 DEG DURING THE EVENING. BOUNDARY
LAYER WIND IS HIGHER...WITH 15-20 KTS AT 1000 FT. PREVIOUS FORECAST
HAD GONE WITH 1SM BR OVERNIGHT BUT NOT CONFIDENT THAT WILL
MANIFEST. FEEL WE WILL DECOUPLE EARLY AND PERHAPS EVEN FORM SOME
BCFG NEAR KLSE BY 06Z. BUT WIND WILL KEEP IT FROM DEVELOPING
FURTHER...AND LACK OF MOISTURE LOOKING TO PRECLUDE WIDESPREAD
STRATUS. SOME INDICATION THAT WARM ADVECTION WILL HELP GENERATE
SOME PATCHY CLOUD COVER OVERNIGHT WHICH WOULD LIMIT RADIATION.
HAVE OPTED TO BACK OUT OF ANY FOG FOR NOW. BUT LATER SHIFTS WILL
NEED TO MONITOR IF WIND FIELD SLACKENS. IF THE FOG/STRATUS DOES
INDEED FORM...INVERSION MAY ALLOW IT TO EXPAND AND DEVELOP
FURTHER.

&&

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

$$

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


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