Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 020438
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1138 PM CDT WED OCT 1 2014

.UPDATE...
ISSUED AT 1117 PM CDT WED OCT 1 2014

ISSUED DENSE FOG ADVISORY FROM 02.07Z UNTIL 02.15Z ACROSS MOST OF
SOUTHEAST MN...PORTIONS OF NORTHEAST IA AND BUFFALO COUNTY IN WI.
THIS IS THE AREA THAT RECEIVED THE MOST RAINFALL YESTERDAY
RESULTING IN A SATURATED LOW-LEVEL AIR MASS. WITH VERY LIGHT
SURFACE WIND...RAPID REDUCTIONS IN VISIBILITY TO ONE QUARTER MILE
OR LESS EXPECTED AS SKIES CLEAR. MAY NEED TO EXPAND ADVISORY
FARTHER EAST LATER TONIGHT...BUT CONFIDENCE NOT AS GREAT DUE TO
LOW-MID LEVEL CLOUD COVER AND SOMEWHAT DRIER BOUNDARY LAYER.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 250 PM CDT WED OCT 1 2014

A SHORTWAVE TROUGH WILL LIFT NORTHEAST THROUGH THE UPPER MISSISSIPPI
RIVER VALLEY LATE THIS AFTERNOON INTO THIS EVENING DRAGGING A
STATIONARY FRONT INTO CENTRAL MINNESOTA/FAR NORTHWEST WISCONSIN. THE
PRESSURE GRADIENT WILL BECOME BAGGY OVER THE FORECAST AREA AS THE
FRONT EDGES CLOSER. WITH THE RAIN TODAY AND SOME DRYING OCCURRING
ALOFT...THIS WILL INCREASE THE CONCERN FOR FOG DEVELOPMENT TONIGHT.
MUCH OF THE GUIDANCE IS INDICATING AT LEAST 1 MILE FOG TONIGHT.
LOOKING AT FORECAST SOUNDINGS THERE IS THE POTENTIAL FOR THE FOG TO
BECOME DENSE.  IF THIS DRYING OCCURS ALOFT...THIS WOULD SET THE
STAGE FOR DENSE FOG AND A DENSE FOG ADVISORY MAY BE NEEDED ACROSS
MUCH OF THE AREA. ALSO...THE WIDESPREAD CLOUD COVER TODAY WILL HELP
KEEP TEMPERATURE/DEWPOINT SPREADS FAIRLY CLOSE...SO IT WON/T TAKE
MUCH COOLING TONIGHT TO GET THE FOG TO FORM. HAVE TWEAKED PRODUCTS
TOWARDS FOG TONIGHT. THE EVENING SHIFT WILL HAVE TO KEEP A VERY
CLOSE EYE ON TRENDS AND POSSIBLY ISSUE A DENSE FOG ADVISORY IF
CONDITIONS BECOME FAVORABLE.

LOW PRESSURE LIFTS NORTHEAST OUT OF THE CENTRAL PLAINS DURING THE DAY
ON THURSDAY AND PUSHES INTO THE UPPER MISSISSIPPI RIVER VALLEY. THIS
SYSTEM WILL SPREAD SHOWERS AND POSSIBLY SOME ISOLATED THUNDERSTORMS
TO THE REGION. VERY NICE UPPER LEVEL SUPPORT OVER THE REGION WITH
THIS LOW...WITH THE RIGHT ENTRANCE REGION OF A 250 MB JET STREAK
LOCATED DIRECTLY OVER THE FORECAST AREA. MEANWHILE...ANOTHER LOW IS
PUSHING SOUTHEAST OUT OF OF SOUTHERN MANITOBA LATE IN THE DAY ON
THURSDAY. WE WILL SEE RAPID CYCLOGENESIS OCCUR OVER AS A TROUGH DIGS
INTO THE REGION AND LOW DEEPENS OVER NORTHEAST WISCONSIN INTO
EASTERN UPPER MICHIGAN AND EASTERN LAKE SUPERIOR. THE TRACK OF THE
LOW PLACES A WELL DEFINED DEFORMATION ZONE OVER THE FORECAST AREA SO
WILL WILL SEE A SWATH OF 1 TO 2 INCHES OF RAINFALL ON THE NORTHWEST
SIDE OF THE LOW. AT THIS TIME IT APPEARS THE LOW WILL TRACK FROM FAR
NORTHEAST IOWA INTO CENTRAL WISCONSIN THURSDAY AFTERNOON INTO
THURSDAY EVENING. THIS WOULD CENTER THE BAND ROUGHLY  FROM CHARLES
CITY...TO LA CROSSE...TO NEILLSVILLE. ANY SHIFT IN THE LOW TRACK
WILL RESULT IN A SHIFT OF THE HEAVIER RAINFALL. WILL HAVE TO KEEP A
CLOSE EYE ON FAR SOUTHWEST INTO PORTIONS OF SOUTH CENTRAL WISCONSIN
FOR THE OUTSIDE CHANCE OF SEEING A BRIEF WEAK TORNADO...IF SURFACE
CAPE CAN BUILD IN THESE AREAS NORTHEAST OF THE SURFACE LOW TRACK
DURING THE LATE MORNING TO AFTERNOON HOURS.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 250 PM CDT WED OCT 1 2014

A POTENT TROUGH DIVES INTO THE REGION THURSDAY NIGHT THROUGH FRIDAY
BRINGING WINDY CONDITIONS AND UNSEASONABLY COOL AIR INTO THE REGION.
FRIDAY INTO FRIDAY NIGHT WILL BE DOWNRIGHT RAW FOR THIS TIME OF
YEAR...WITH NORTHWEST WINDS OF 18 TO 25 MPH WITH GUST APPROACHING 40
MPH AT TIMES. THE STRONGEST WINDS WILL OCCUR FRIDAY AFTERNOON INTO
FRIDAY NIGHT WHEN THE COOLEST AIR ADVECTS INTO THE REGION. 850 MB
TEMPERATURES GO FROM AROUND 5 C FRIDAY MORNING TO NEGATIVE 3 C BY
SATURDAY MORNING AS THE TROUGH MOVES IN. RAIN SHOWERS AND POSSIBLY A
FEW SNOW FLAKES ARE POSSIBLE FRIDAY EVENING INTO EARLY  SATURDAY
MORNING WITH THE ARRIVAL OF THE COOLEST AIR. LOOKING AT FORECAST
SOUNDINGS THERE ARE TWO CONCERNS WITH THE SNOW POTENTIAL. 1...THERE
MAY NOT BE ICE ALOFT IN THE CLOUD TO GENERATE SNOW AND 2...SURFACE
TEMPERATURES MAY BE JUST WARM ENOUGH FOR IT TO FALL AS DRIZZLE IF
SATURATION ISN/T DEEP ENOUGH...OR JUST PLAIN RAIN IF ITS A LITTLE
DEEPER. LOOKING AT THE COOLER AIR ALOFT WORKING IN FEEL THAT SNOW
REMAINS A POSSIBILITY BUT ACCUMULATIONS ARE UNLIKELY. HIGHS ON
SATURDAY WILL NOT MAKE IT OUT OF THE  40S.  PLAN ON HIGHS RANGING  FROM
THE LOWER 40S OVER NORTH CENTRAL WISCONSIN TO THE UPPER 40S ACROSS
NORTHEAST IOWA. THE UPPER TROUGH THEN REMAINS ENTRENCHED ACROSS THE
REGION FROM SUNDAY INTO NEXT WEEK WITH COOL NORTHEAST FLOW IN PLACE.
A WEAK WAVE MOVES THROUGH ON SUNDAY AND MAY GENERATE  A FEW SHOWER.
PLAN ON HIGHS ON SUNDAY REBOUNDING  SLIGHTLY WITH HIGHS IN THE 50S.
TEMPERATURES COULD WARM SLIGHTLY TOWARD THE MIDDLE OF NEXT WEEK AS
THE TROUGH EDGES EAST AND FLOW ALOFT TURNS ZONAL. HIGHS COULD WARM
INTO THE UPPER 60S TO LOWER 70S NEXT WEDNESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1138 PM CDT WED OCT 1 2014

CONFIDENCE INCREASING FOR WIDESPREAD DENSE FOG AT TAF AIRFIELDS
GIVEN SATURATED NEAR SURFACE LAYER...CLEARING SKIES ALOFT AND VERY
LIGHT WIND. EXPECT FOG TO RAPIDLY DEVELOP BETWEEN 02.08Z TO 02.10Z
WITH VISIBILITY DROPPING BELOW 1/4SM AND CEILINGS FROM 100 TO 200
FT AGL. FOG TO GRADUALLY DISSIPATE BETWEEN 02.15Z AND 02.16Z
BEFORE MVFR/IFR CONDITIONS PERSIST THROUGH THE AFTERNOON AND INTO
THE EVENING WITH RAIN SHOWERS INCREASING FROM SOUTHWEST TO
NORTHEAST AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS THE REGION.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 10 AM CDT THURSDAY FOR WIZ032.

MN...DENSE FOG ADVISORY UNTIL 10 AM CDT THURSDAY FOR MNZ079-086>088-
     094-095.

IA...DENSE FOG ADVISORY UNTIL 10 AM CDT THURSDAY FOR IAZ008-009-018-
     019.

&&

$$

UPDATE...ROGERS
SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...ROGERS


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