Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 060450
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1150 PM CDT TUE MAY 5 2015

.UPDATE...THROUGH WEDNESDAY MORNING
ISSUED AT 1150 PM CDT TUE MAY 5 2015

AREAS OF DENSE FOG ARE DEVELOPING ACROSS NORTHEAST IOWA AND
SOUTHEAST MINNESOTA THANKS TO RECENT RAINFALL...A MOIST
AIRMASS...AND A WARM FRONT OVER THE AREA. CURRENTLY VISIBILITIES
ARE INT HE 1/4 TO 1 MILE RANGE ACROSS THESE AREA AND CONTINUE TO
FALL. A DENSE FOG ADVISORY MAY BE NEEDED SOON ACROSS THESE AREAS
AND THIS DENSE FOG COULD LINGER INTO THE WEDNESDAY MORNING
COMMUTE. HAVE ISSUED A SPECIAL WEATHER STATEMENT FOR THE FOG
THREAT BUT AM ANTICIPATING A DENSE FOG ADVISORY MAY BE NEEDED
SOON.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 343 PM CDT TUE MAY 5 2015

AT 3 PM...LIGHT RAIN CONTINUES TO FALL ALONG AND SOUTH OF THE
INTERSTATE 90 CORRIDOR. HOURLY RAINFALL AMOUNTS ARE RANGING FROM
JUST A TRACE TO 0.05 INCHES PER HOUR. THIS RAIN IS BEING PRODUCED
BY 900 TO 800 MB FRONTOGENESIS AND A SURFACE WARM FRONT IN
NORTHERN IOWA. 05.12Z MODELS CONTINUE TO SHOW THAT THE WARM FRONT
WILL MOVE SLOWLY NORTH TO THE INTERSTATE 90 CORRIDOR TONIGHT AND
INTO CENTRAL MINNESOTA AND NORTHERN WISCONSIN ON WEDNESDAY. THIS
FRONTOGENESIS AND WARM FRONT WILL CONTINUE TO BE FOCUS OF RAIN.
WITH SOME DRIER AIR IN THE MID LEVELS MOVING INTO THE REGION
DURING IN THE WARM SECTOR OF THIS FRONT...THINKING THAT THIS AREA
COULD BE DRY MUCH OF WEDNESDAY. BOTH THE ARW AND NMM SUGGEST THIS
POSSIBILITY FOR MUCH OF THE DAY.

INSTABILITY LOOKS REALLY WEAK FROM TONIGHT INTO WEDNESDAY...BUT
WITH THE FRONT IN THE AREA AND 850 TO 700 MB LAPSE RATES IN THE 8
TO 10 C/KM RANGE...CANNOT COMPLETELY RULE OUT A THUNDERSTORM...SO
JUST KEPT AN ISOLATED STORM IN THE FORECAST.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 343 PM CDT TUE MAY 5 2015

FROM WEDNESDAY NIGHT INTO THURSDAY...THE 05.12Z MODELS CONTINUE TO
SHOW THAT THE AREA WILL BE LOCATED IN THE WARM SECTOR OF THE
SYSTEM. THERE CONTINUES TO BE MODERATE MOISTURE TRANSPORT INTO THE
AREA...BUT THE BEST CONVERGENCE REMAINS NORTH AND WEST OF THE
AREA SO THERE IS A POSSIBILITY THAT THIS PERIOD COULD BE DRY. THIS
IS ESPECIALLY THE CASE IN WESTERN WISCONSIN. AS A RESULT...KEPT
THE PRECIPITATION CHANCES THE LOWEST IN THESE AREAS.

ON THURSDAY NIGHT...THE COLD FRONT WILL MOVE EAST THROUGH THE
AREA. 0-1 KM MIXED LAYER CAPES CLIMB INTO THE 1 TO 2K RANGE AHEAD
OF THIS FRONT. LIKE THE PAST COUPLE OF DAYS...THE 0-6 KM SHEAR
REMAINS LESS THAN 30 KNOTS...SO NOT EXPECTING ANY SUPERCELLS.
HOWEVER WITH THE COLD FRONT PRODUCING LINEAR CONVECTION AND 0-3 KM
UP TO 40 KNOTS COULD NOT RULE SOME ISOLATED DAMAGING WIND.

FROM FRIDAY INTO SATURDAY...THE MODELS DIVERGE SOME. THE GFS
BUILDS A HIGH PRESSURE AREA INTO THE AREA. MEANWHILE THE GEM AND
ECMWF STALL THE FRONT TO OUR SOUTHEAST AND SEVERAL WAVES OF LOW
PRESSURE CONTINUE TO BRING ROUNDS PRECIPITATION INTO THE SOUTHEAST
PORTION OF THE FORECAST AREA. WITH QUITE A BIT OF UNCERTAINTY IN
THIS TIME FRAME...JUST STAYED WITH THE MODEL CONSENSUS.

FOR EARLY NEXT WEEK...THE GFS CONTINUES TO TRACK THE SURFACE LOW
TO OUR SOUTHEAST. MEANWHILE THE ECMWF HAS TRENDED A BIT FURTHER
NORTHEAST AND IT HAS PARTS OF SOUTHWEST WISCONSIN AND NORTHEAST
IOWA ENTERING THE WARM SECTOR OF THIS SYSTEM. DUE TO INCONSISTENT
SIGNALS IN THE TRACK AND EVEN TIMING...OPTED TO STAY WITH THE
MODELS CONSENSUS FOR NOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1150 PM CDT TUE MAY 5 2015

PERIODS OF LIFR TO VLIFR CONDITIONS ARE EXPECTED AT KRST IN FOG
AND STRATUS THROUGH MID MORNING ON WEDNESDAY WITH VISIBILITIES
FALLING INTO THE 1/4 TO 1/2 MILE RANGE AND CEILINGS OF 200 FT OR
LESS. CONDITIONS WILL IMPROVE IN THE 12 TO 14Z TIMEFRAME AS A
WARM FRONT STARTS TO LIFT NORTH OF THE TAF SITES. MVFR TO IFR
CONDITIONS ARE EXPECTED AT KLSE IN FOG AND STRATUS. PLAN ON
CEILINGS FALLING TO AROUND 900 AND VISIBILITIES RANGING FROM 4 TO
5 SM. LOOK FOR CONDITIONS TO IMPROVE TO VFR BY MID MORNING ON
WEDNESDAY.

&&

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

$$

UPDATE...WETENKAMP
SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...WETENKAMP



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