Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 312052
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
352 PM CDT TUE MAR 31 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 350 PM CDT TUE MAR 31 2015

MAIN CONCERNS DURING THE PERIOD ARE WARMING CONDITIONS WITH DEEPER
MIXING AND WINDY CONDITIONS. THUS...MAINLY AN ELEVATED GRASS FIRE
DANGER DAY WITH THOSE WEATHER CONDITIONS. SEE FIRE WEATHER
SECTION FOR MORE DETAILS. HAVE ISSUED A FIRE WEATHER WATCH FOR
PARTS OF NORTHEAST IOWA WHERE GRASSLAND FIRE DANGER IS IN THE
EXTREME CATEGORY.

GOOD HEIGHT FALLS SEEN ALONG THE WEST COAST OF NORTH AMERICA WHERE
STRONG SHORTWAVE TROUGH IS MOVING IN /150M 12HR FALLS AT 500MB PER
RAOBS/. SHORTWAVE RIDGING AT MID-LEVELS IS NOW SHIFTING INTO THE
HIGH PLAINS AND CLEAR CONDITIONS IN PLACE PER GOES VISIBLE IMAGERY.
PRESSURE FALLS IN THE DAKOTAS AND WEST ARE IN THE 2-3MB/3 HR AHEAD
OF THE WEST COAST TROUGH...THE RAIN MAKER FOR WEDNESDAY NIGHT.

WEDNESDAY WILL BRING STRONG SOUTHERLY WINDS AHEAD OF A FRONT OVER
THE DAKOTAS BY MORNING. LOW-LEVEL PRESSURE GRADIENT WILL RAMP UP
IN THE LATER MORNING PER CONSENSUS GUIDANCE. MIXING DEPTH WILL
INCREASE TO 3-4KFT /900 MB/ BY MID-AFTERNOON WITH 35-40 KTS AT THE
TOP OF THE MIXED LAYER...PUSHING WIND/GUST SPEEDS IN THE NEAR-
ADVISORY CATEGORY...25 TO 40 MPH. HAVE DECIDED TO HOLD ON THE WIND
ADVISORY FOR NOW...BUT ANY UPTICK IN THE WINDS IN THE FORECAST AND
AN ADVISORY WILL BE NEEDED FOR SERN MN...WE WILL ASSESS THIS
OVERNIGHT.

BELIEVE SKIES WILL BE SUNNY AHEAD OF THE FRONT WITH SOME CIRRUS
SHIELD I-90 AND NORTH...WHICH COULD MEAN DEEPER MIXING ACROSS NERN
IA AND SWRN WI. WILL ALSO HAVE SOME WARM ADVECTION IN THE NORTH
THROUGH THE MORNING...BUT NOT EXPECTED PRECIPITATION. HAVE RAISED
WED HIGHS ACROSS THE SOUTH 3-4F...AND 2-3F ELSEWHERE BASED ON
EXPECTED SUN...925 MB TEMPERATURES WARMING 6-7C FROM TODAY TO
WEDNESDAY...AND GRADIENT/WINDS FOR GOOD MIXING.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 350 PM CDT TUE MAR 31 2015

PRECIPITATION CONSENSUS FROM THE DETERMINISTIC MODELS IS QUITE
HIGH FOR THE COLD FRONT AS IT PASSES ON WEDNESDAY NIGHT.
THUNDERSTORMS SHOULD FORM ACROSS IOWA AND SRN MN LATER IN THE
AFTERNOON AND PROPAGATE EASTWARD ON A NARROW MOIST PLUME NEAR
FRONT. COLD FRONT WILL NOT ENTER THE FORECAST AREA UNTIL ABOUT
MIDNIGHT...WHICH MEANS WAINING INSTABILITY. THERE IS STILL SOME
QUESTION TOO HOW THE MOIST POOL NOW IN OK/AR WILL ADVECT
NORTH...AND WHAT MOISTURE WILL BE AVAILABLE FOR STORMS. CURRENT
LOW-LEVEL AIR MASS IS QUITE DRY...SO HAVE FAVORED A TEMPERED
DEWPOINT RETURN AS PREVIOUS FORECASTS. FOR SEVERE WEATHER...
INSTABILITY WOULD BE THE LIMITING FACTOR PER TIMING AND MOISTURE
RETURN. HAVE CONCENTRATED RAINFALL AMOUNTS I-90 AND SOUTH AS THE
CONVECTIVE SYSTEM WILL BE MOST VIVACIOUS AND DESIRE A PROPAGATION
VECTOR TOWARD THE MOIST SOURCE /IOWA/. CONVECTIVE ALLOWING MODELS
/CAMS/ GENERALLY MIGRATE TO A SHOWERY COVERAGE AS THE SYSTEM MOVES
EAST ACROSS THE FORECAST AREA OVERNIGHT.

POST-FRONTAL CONDITIONS ARE EXPECTED THURSDAY...HOWEVER THE FRONT
IS ONLY A MILD POLAR FRONT WITH ABOVE NORMAL HIGHS EXPECTED AND A
DRIER AIR MASS TO RETURN. MIXING WILL AGAIN BE DEEP ON THURSDAY
AND BREEZY CONDITIONS ARE EXPECTED. SEE THE FIRE WEATHER
DISCUSSION FOR CONCERNS THURSDAY. COLDER ARCTIC FRONT SHIFTS IN
THURSDAY NIGHT AND COOLS TEMPERATURES ANOTHER 15-20F FOR FRIDAY.

A SOUTHERN SYSTEM LOOKS TO PASS THROUGH ILLINOIS FRIDAY WITH SOME
SMALL RAIN CHANCES ACROSS THE SOUTH.

SATURDAY THROUGH TUESDAY...MODEL TRENDS TOWARD A SPLIT FLOW REGIME
ARE AGREED UPON WELL IN THE ECMWF AND GFS FROM 31.12Z. THE
FORECAST AREA WOULD REMAIN UNDER THE NW FLOW SPLIT WITH
TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL. FRONTOGENESIS IN THE
CONFLUENT FLOW COULD BRING SOME WEEKEND SHOWERS TOO.

SOME INDICATIONS EXIST FOR A TRANSITION TO A WESTERN U.S. TROUGH
EARLY NEXT WEEK WHICH COULD BE A RAINIER PATTERN.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1218 PM CDT TUE MAR 31 2015

MAIN CONCERN GOING THROUGH WEDNESDAY MORNING WILL BE GUSTY SOUTH
WINDS AFTER DAYBREAK. THIS WILL BE AHEAD OF A STRONG LOW PRESSURE
SYSTEM MOVING INTO THE NORTHERN PLAINS. PLAN ON SOUTH WINDS
PICKING UP AROUND 25KT GUSTING TO NEAR 35KT AT KRST AND 15KT
GUSTING NEAR 25KT AT KLSE. APPEARS THERE WILL BE SOME MID- LEVEL
CLOUDS WITH BASES AOA 15KFT AFTER 14Z...SO VFR THROUGH THE PERIOD.
LOOKING FURTHER...SHOWERS AND THUNDERSTORMS ARE EXPECTED TO FORM
AHEAD OF A COLD FRONT BY LATE WEDNESDAY AFTERNOON...AFFECTING
KRST/KLSE TAF SITES WEDNESDAY EVENING. MORE DETAIL WILL BE PUT
INTO THIS WITH THE 01.00/01.06Z TAF ISSUANCES.


&&

.FIRE WEATHER...
ISSUED AT 350 PM CDT TUE MAR 31 2015

WITH DRY FUELS AND SOME WINDS TODAY...IOWA HAS HAD SOME ISSUES
WITH FIRES TODAY. SPECIFICALLY...LOSING CONTROL OF PRESCRIBED
BURNS.

WEDNESDAY...STRONG WINDS IN THE 20 TO 30 MPH RANGE WITH GUSTS TO
40 MPH...AND RELATIVE HUMIDITIES IN THE LOWER 30S...MAKES FOR
ELEVATED FIRE WEATHER CONDITIONS. GRASSLAND FIRE DANGER VALUES ARE
OVER 50 /EXTREME/ IN IOWA AND THUS HAVE ISSUED A RED FLAG WATCH
THERE...EXCEPT MISS RIVER COUNTIES WHERE WINDS ARE A BIT LESS.
HOWEVER...WE MAY NEED A RED FLAG WATCH IN MN FOR THESE CONDITIONS
BASED ON BURN ACTIVITY TODAY AND ELEVATED CONDITIONS WEDNESDAY.
GOOD NEWS IS THAT SOME RAIN IS EXPECTED WEDNESDAY NIGHT TO KNOCK
DOWN FIRE ACTIVITY.

THURSDAY...POST-FRONTAL NORTHWEST WINDS WILL INCREASE AND DEEPLY
MIX TO POSSIBLY 5KFT. WITH DRIER AIR MASS MOVING IN...RH VALUES
ARE EXPECTED TO BE IN THE 20S BY AFTERNOON. WINDS WILL BE LESS
THURSDAY IN THE 15 TO 25 MPH RANGE...BUT ENOUGH TO CAUSE ANOTHER
ELEVATED FIRE DANGER DAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
     EVENING FOR IAZ008>010-018-019-029.

&&

$$

SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...DAS
FIRE WEATHER...BAUMGARDT


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