Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 230900
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
400 AM CDT THU APR 23 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT THU APR 23 2015

MAIN FCST CONCERNS THIS PERIOD...TEMPERATURES.

06Z DATA ANALYSIS HAD CANADIAN HIGH PRESSURE RIDGING FROM MANITOBA
SOUTHWARD TO MO WITH THE RIDGE AXIS NEAR THE MN/DAKOTAS AND NEB/IA
BORDER. CLOUDS LIMITED TO THE NORTHEAST 1/4 OF WI EARLY THIS
MORNING. WEAK TO MDT PRESSURE GRADIENT REMAINED OVER WI AND EASTERN
MN/IA...WITH LIGHT NORTHWEST WINDS CONTINUING ACROSS MUCH OF THE
REGION. EVEN WITH THE LIGHT WINDS...EARLY MORNING TEMPERATURES
ACROSS MUCH OF MN/IA/WI WERE IN THE MID 20S TO MID 30S.

23.00Z MODELS INITIALIZED WELL. SOLUTIONS VERY SIMILAR FOR TODAY/
TONIGHT AS HGTS RISE/SHORTWAVE RIDGING ALOFT BUILDS INTO THE UPPER
MIDWEST...AHEAD OF STRONGER TROUGHING/ENERGY MOVING INTO/THE WESTERN
CONUS. TREND FAVORS MORE PROGRESSIVE OF THE EARLIER MODELS ON THE
RIDGING BUILDING IN...WITH ECMWF HAVING THE BETTER RUN-TO-RUN
CONSISTENCY. SHORT-TERM FCST CONFIDENCE IS GOOD THIS CYCLE.

IN THE SHORT-TERM...SHORT TERM IS RATHER QUIET THIS CYCLE AS THE
COOL/CAN HIGH PRESSURE DRIFTS EAST ACROSS THE UPPER MIDWEST. RIDGE
AXIS IS PROGGED FROM WESTERN ONT TO IL AT 00Z FRI...THEN OVER LK
SUPERIOR THRU LK MI TO KY BY 12Z FRI. MODEL SOUNDINGS/X-SECTIONS
SHOW A DEEP DRY AIRMASS OVER THE AREA TODAY...FOR PLENTY OF
SUNSHINE. MODEL SOUNDINGS SHOWING MIXING TO 850MB OR A BIT HIGHER
THIS AFTERNOON...WITH WINDS IN 925-850MB PORTION OF THE MIXED LAYER
IN THE 10-15KT RANGE. EVEN WITH THE RIDGE AXIS NEARBY TODAY...WINDS
LOOKING TO BE NORTHWEST 8-12 MPH WITH A FEW HIGHER GUSTS LATE THIS
MORNING THRU MUCH OF THE AFTERNOON. 850MB TEMPS TODAY 2C TO 3C
WARMER THAN THOSE OF WED...WITH HIGHS TODAY MOSTLY IN THE UPPER 40S
TO MID 50S LOOKING TO BE WELL TRENDED. WINDS TO DIMINISH/DECOUPLE
VERY QUICKLY EARLY THIS EVENING WITH LOSS OF DIURNAL HEATING. CLEAR
SKIES THIS EVENING GIVE WAY TO INCREASING CLOUDS OVERNIGHT AS
INCREASING FLOW AHEAD OF THE NEXT LEE LOW DEVELOPING IN THE CENTRAL
PLAINS SPREADS MOISTURE FROM THE SOUTHERN PLAINS NORTH AND EAST INTO
THE UPPER MIDWEST. MAINLY MID/HIGH CLOUDS EXPECTED TO INCREASE LATER
TONIGHT WITH THE MAIN MOISTURE/THETA-E RIDGE AXIS AND LOWER LEVEL
THERMODYNAMIC FORCING REMAINING WEST OF THE FCST AREA. LEFT LATE
TONIGHT DRY. INCREASING SOUTHEAST GRADIENT WINDS /AND CLOUDS/ LATER
TONIGHT ALONG WITH SOME LOW LEVEL WARM ADVECTION WILL HELP KEEP LOWS
WARMER TONIGHT...ESPECIALLY ALONG/WEST OF THE MS RIVER. LOWS ACROSS
THE NORTHEAST 1/3 OF THE FCST AREA LOOKING TO BE AS COLD AS THIS
MORNING...WHERE WIND TO STAY LIGHT/DECOUPLED AND SKIES CLEAR/ MOSTLY
CLEAR THE LONGEST. TRENDED TOWARD WARMER OF GUIDANCE HIGHS TODAY.
TRENDED TOWARD WARMER OF GUIDANCE LOWS WEST AND COOLER OF GUIDANCE
LOWS EAST TONIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 400 AM CDT THU APR 23 2015

MAIN FCST CONCERNS FOR FRI THRU SAT NIGHT...RAIN CHANCES FRI INTO
SAT...TEMPERATURES THRU THE PERIOD.

23.00Z MODELS IN RATHER GOOD AGREEMENT TO START THIS PERIOD...BUT BY
00Z SAT QUICKLY DIVERGE WITH THE SHORTWAVE DETAILS IN THE TROUGH
MOVING ACROSS THE CENTRAL PLAINS. MODELS IN SOMEWHAT BETTER
AGREEMENT AS THE SHORTWAVE ENERGY/TROUGH MOVES INTO/ACROSS THE MID
MS VALLEY FRI NIGHT/SAT...THEN MERGES WITH THE NEW ENGLAND MID LEVEL
LOW SAT NIGHT. TREND TENDS TO FAVOR SLOWER MORE AMPLIFIED OF THE
EARLIER RUNS WITH THIS TROUGH AND RIDGING BEHIND IT FOR FRI THRU SAT
NIGHT. GIVEN THE SHORTWAVE DETAIL DIFFERENCES ALREADY ON FRI...FCST
CONFIDENCE IN THE FRI THRU SAT NIGHT PERIOD IS AVERAGE THIS CYCLE.

MOISTURE/LIFT INCREASE ACROSS THE AREA FRI AS THE SFC LOW THRU MID
LEVEL TROUGH MOVES ACROSS THE PLAINS AND TOWARD THE REGION ON FRI.
GIVEN THE SHORTWAVE DETAIL DIFFERENCES...SOME MODELS FASTER THAN
OTHERS SPREADING PRECIP INTO/ACROSS THE AREA ON FRI...AND WHERE THE
HEAVIER OF ANY RAIN MAY FALL. STAYED WITH THE ENSEMBLE MEAN APPROACH
WITH PRECIP CHANCES FRI...MAINLY OVER THE WEST HALF FRI MORNING...
INCREASING AND SPREADING EAST ACROSS THE AREA IN THE AFTERNOON.
RAISED/CONTINUED 50-70 PERCENT RAIN CHANCES ACROSS THE SOUTH/WEST
PORTIONS OF THE FCST AREA FRI NIGHT WITH THE BETTER CONSISTENCY ON
THE LOW MOVING INTO NORTHERN MO. LESSER RAIN CHANCES NORTH/EAST OF
KLSE WHERE DRIER EASTERLY LOW LEVEL FLOW MAY WIN OUT. CIRCULATION
TIGHTENS SAT WITH THE SFC LOW/SHORTWAVE ENERGY PASSING ACROSS IL.
DEEPER MOISTURE/SATURATION AND STRONGER OF FORCING/LIFT PASS ACROSS
THE SOUTH END OF THE FCST AREA. 40-60 PERCENT RAIN CHANCES ACROSS
THE SOUTH 1/3 TO HALF OF THE FCST AREA TO DRY IN TAYLOR CO WI SAT
MORNING REASONABLE. SLOWER TREND LINGERS MORE MOISTURE/LIFT INTO THE
AFTERNOON ACROSS THE SOUTH END OF THE FCST AREA AND RAISED RAIN
CHANCES A BIT MAINLY SOUTH OF I-90 FOR SAT AFTERNOON. RAIN
AMOUNTS...USING THE MODEL/ENSEMBLE...FROM FRI THRU SAT LOOKING TO
RANGE FROM LESS THAN 1/10 INCH OVER THE NORTH END OF THE FCST AREA
TO 1/4 TO 1/2 INCH OVER THE SOUTHEAST 1/3 OF THE FCST AREA. LEFT SAT
NIGHT DRY WITH THE LOW MOVING INTO THE OH VALLEY AND SFC THRU MID
LEVEL RIDGING BUILDING ACROSS THE UPPER MIDWEST. A COOLER NIGHT
AGAIN SAT NIGHT UNDER THE APPROACHING/BUILD RIDGE AXIS BUT LOWS WILL
DEPEND ON HOW QUICKLY THE LOWER CLOUDS CLEAR OUT AND IF SFC WINDS
WITH A MDT PRESSURE GRADIENT AROUND THE SFC HIGH CAN DECOUPLE. WITH
AVERAGE CONFIDENCE THIS PERIOD...STAYED WITH THE MODEL/ENSEMBLE
CONSENSUS HIGHS/LOWS FOR FRI THRU SAT NIGHT.

FOR SUN THRU WED...DAYS 4 TO 7...

MAIN FCST CONCERNS THIS PERIOD...SMALL RAIN CHANCES TUE/WED...
TEMPERATURES THRU THE PERIOD.

MEDIUM RANGE MODEL RUNS OF 23.00Z SHOW GOOD AGREEMENT FOR SHORTWAVE
RIDGING ALOFT OVER THE REGION SUN/MON...AS MORE NORTHERN/SOUTHERN
STREAM ENERGY MOVES FROM THE ROCKIES INTO THE CENTRAL CONUS. BY
TUE/WED...MODELS CONTINUE DIFFER ON THE PROGRESSIVENESS AND PHASING
OR NOT OF THE NORTHERN/SOUTHERN/STREAM ENERGY. TREND FROM 22.00Z IS
TOWARD LESS PHASING...AT LEAST UNTIL THE TROUGH AXIS WOULD BE
EAST/SOUTH OF THE REGION. SOME CONSENSUS FOR WESTERN NOAM RIDGING
AND EASTERN NOAM TROUGHING FOR MID TO LATE NEXT WEEK...WITH THE
UPPER MIDWEST UNDER NORTHWEST FLOW ALOFT. FCST CONFIDENCE IN THE DAY
4-7 PERIOD IS AVERAGE TO BELOW THIS CYCLE.

SUN/MON TRENDING DRY WITH THE SFC THRU MID LEVEL RIDGING AND A DRY
AIRMASS OVER THE REGION. MODEL CONSENSUS HAS 850MB TEMPS IN THE +2C
TO +5C RANGE SUN/MON...SUPPORTING HIGHS IN THE UPPER 50S-LOW 60S.
HGTS FALL WILL APPROACH OF THE NORTHERN/SOUTHERN STREAM TROUGH
AXES...WITH SOME FORM OF A SFC/LOW LEVEL TROUGH TO PUSH INTO/ACROSS
THE REGION. MOISTURE LOOKS TO BE ON THE LIMITED SIDE...HOWEVER NOT
ENOUGH CONFIDENCE TO MAKE CHANGES TO THE SMALL MODEL CONSENSUS -RA
CHANCES ON TUE-WED. TEMPERATURES FOR TUE/WED LOOKING TO REMAIN NEAR
THOSE OF SUN/MON...PERHAPS A BIT COOLER IF A MUCH CLOUDIER SOLUTION
ENDS UP BEING MORE CORRECT IN THE DAY 6/7 TIME-FRAME. MODEL/
ENSEMBLE CONSENSUS HIGHS/LOWS FOR SUN-WED QUITE REASONABLE FOR NOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1147 PM CDT WED APR 22 2015

SKIES WILL REMAIN MAINLY CLEAR THROUGH THE PERIOD. NORTHWEST WINDS
WILL REMAIN LESS THAN 10 KNOTS THROUGH 24.03Z...AND THEN BECOME
LIGHT SOUTHEAST.

&&

.FIRE WEATHER...TODAY
ISSUED AT 400 AM CDT THU APR 23 2015

A SUNNY AND WARMER DAY IS EXPECTED ACROSS THE AREA TODAY. A DRY AIR
MASS HAS SETTLED ACROSS THE REGION...WITH FEW OPTIONS FOR INCREASING
THE DEW POINTS TODAY. DEEP MIXING AND DRY AIR ALOFT...HUMIDITIES
THIS AFTERNOON ARE EXPECTED TO MOSTLY BE IN THE 17 TO 27 PERCENT
RANGE. WINDS ALOFT IN THE UPPER PORTION OF THE MIXED LAYER MOSTLY IN
THE 10-15KT RANGE TODAY. WITH THE DEEPER MIXING LATE THIS MORNING
AND THIS AFTERNOON...NORTHWEST WINDS 8-12 MPH WITH OCCASIONAL GUSTS
IN THE 13-18 MPH RANGE ARE EXPECTED. WITH SOME GREEN-UP ALREADY
OCCURRING AND THE LIGHTER WINDS...APPEARS RED FLAG CONDITIONS WILL
NOT BE REACHED TODAY. RAIN CHANCES/CLOUDS INCREASE FROM WEST TO EAST
ACROSS THE AREA FRI AND CONTINUE FRI NIGHT INTO SAT. SEE ABOVE FOR
EXPECTED RAIN AMOUNTS FROM FRI THRU SAT WHICH SHOULD HELP MITIGATE
FIRE WEATHER CONCERNS INTO THE WEEKEND.

&&

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

$$

SHORT TERM.....RRS
LONG TERM......RRS
AVIATION.......BOYNE
FIRE WEATHER...RRS



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