Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 251716
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1216 PM CDT WED MAR 25 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 348 AM CDT WED MAR 25 2015

MAIN FCST CONCERNS THIS PERIOD...EXITING PRECIP EARLY THIS
MORNING...TEMPERATURES.

DATA ANALYSIS AT 06Z HAD LOW PRESSURE OVER CENTRAL IL AND ANOTHER
NEAR THE ND/MN/MAN BORDER. WV IMAGERY DEPICTED THE MID LEVEL
SHORTWAVE AXIS/ENERGY EXTENDING FROM EASTERN ND TO CENTRAL
IL...APPROACHING THE WEST END OF THE FCST AREA. AREA RADARS SHOW THE
WINTRY MIX OF PRECIP EAST OF THIS AXIS...WITH THE TRAILING EDGE OF
THE PRECIP MOVING EAST AT ABOUT 25 MPH EARLY THIS MORNING. PRECIP
MAINLY SNOW WEST/NORTH OF KLSE WITH A WINTRY MIX ACROSS PARTS OF
NORTHEAST IA/SOUTHWEST WI. FEW SNOW REPORTS IN THE 1 TO 2.5 INCH
RANGE WEST/NORTH OF KLSE SO FAR WITH UP TO 1/2 INCH OF SLEET IN
SOUTHWEST WI.

MODEL RUNS OF 25.00Z INITIALIZED WITHOUT ISSUES. SOLUTIONS QUITE
SIMILAR FOR TODAY/TONIGHT...CONTINUING TO FAVOR FASTER OF EARLIER
RUNS AS THE MID MS VALLEY SHORTWAVE EXITS QUICKLY EAST TODAY.
SOLUTIONS TREND FASTER/FLATTER WITH THE NORTHERN STREAM SHORTWAVE
ACROSS NORTHERN MN/WI LATER TODAY/TONIGHT. SOLUTIONS REMAIN SIMILAR
WITH THE COLDER LONGWAVE TROUGHING/FALLING HGTS OVER THE REGION AT
12Z THU. SHORT-TERM FCST CONFIDENCE REMAINS GOOD THIS CYCLE.

FOR THE SHORT TERM...DEEPER FORCING/LIFT/MOISTURE CONTINUES TO EXIT
MORE QUICKLY THAN EARLIER MODEL CYCLES. AT THIS POINT...LITTLE
SIGNAL THAT THE TRAILING -DZ/-FZDZ WAS DEVELOPING OR WILL
DEVELOP...WITH THE TRAILING EDGE OF THE WINTRY MIX ALREADY
APPROACHING/CROSSING THE MS RIVER AS OF 0830Z. PORTIONS OF THE
WINTER WEATHER ADVISORY HAVE ALREADY BEEN CANCELED ALONG/WEST OF A
KRST-KDEH-KOLZ LINE AND APPEARS MUCH OF THE REMAINDER WILL BE ABLE
TO BE CANCELED/EXPIRED BY 12Z. WITH MVFR/IFR STRATUS CLOUDS WEST TO
THE MN/DAKOTAS BORDER...TODAY WILL START OUT CLOUDY. GRADIENT
TIGHTENS OVER THE REGION TODAY WITH STRONGER LOW LEVEL COLD
ADVECTION AND SUBSIDENCE SPREADING ACROSS THE AREA. EVEN WITH
THIS...PLENTY OF 925-850MB MOISTURE ASSOCIATED WITH THE SHORTWAVE
TRACKING ACROSS NORTHERN MN TODAY POISED TO SPREAD SOUTH/SOUTHEAST
ACROSS THE FCST AREA THRU THE DAY. WITH LINGERING CYCLONIC FLOW IN
THE SFC-700MB LAYER...RAISED LINGERED MORE CLOUDS ACROSS THE FCST
AREA TODAY INTO THIS EVENING. LIMITED ANY -RA/-SN CHANCES AFTER
EARLY THIS MORNING TO FAR NORTH END OF THE FCST AREA CLOSER TO THE
PASSING NORTHERN STREAM SHORTWAVE. LOWER CLOUDS LOOKING TO
INCREASE AGAIN LATE TONIGHT WITH YET ONE MORE PIECE OF SHORTWAVE
ENERGY TO DROPPING INTO THE DEVELOPING LONGWAVE TROUGH OVER THE
REGION AND A SFC-850MB TROUGH TO DROP INTO THE AREA. MOISTURE ON
THE SHALLOW SIDE AND LEFT TONIGHT DRY. USED A BLEND OF THE
GUIDANCE HIGHS/LOWS FOR TODAY/TONIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 348 AM CDT WED MAR 25 2015

MAIN FCST CONCERNS FOR THU THRU FRI NIGHT...MUCH BELOW NORMAL
TEMPERATURES.

25.00Z MODELS IN GOOD AGREEMENT FOR COLD LONGWAVE TROUGHING OVER THE
MID/UPPER MS VALLEY THU...WITH THE TROUGH MOVING SLOWLY EAST THU
NIGHT THRU FRI NIGHT. 500MB HGTS IN THE -1 TO -2 STANDARD
DEVIATIONS FROM NORMAL THRU MOST OF THIS PERIOD. STRONGER
SHORTWAVE DROPPING DOWN THE WEST SIDE OF THE TROUGH FRI NIGHT
KEEPS NORTHERLY FLOW ALOFT OVER THE REGION INTO SAT MORNING. FCST
CONFIDENCE IN THE THU THRU FRI NIGHT PERIOD IS GOOD FOR A COLD/DRY
PERIOD.

LOW LEVEL COLD ADVECTION CONTINUES OVER THE FCST AREA THU/THU NIGHT
WITH 925MB TEMPS IN THE -8C TO -14C RANGE BY 12Z FRI. WEAK SFC-850MB
TROUGH PASSES THU BUT LARGER SCALE SIGNAL IS FOR COLD CAN HIGH
PRESSURE/ANTICYCLONIC FLOW TO BE BUILDING INTO THE UPPER MIDWEST.
SOME CLOUDS TO PASS ACROSS THE AREA WITH THE LOW LEVEL TROUGH THU
WITH DECREASING CLOUDS/CLEARING THU NIGHT. CLOUDS TO HELP HOLD HIGHS
DOWN THU WHILE CLEARING SKIES/LIGHT WINDS WITH APPROACH OF THE SFC
RIDGE AXIS SHOULD ALLOW FOR STRONG RADIATIONAL COOLING UNDER THE
COLD LOW LEVEL AIRMASS THU NIGHT. SFC RIDGE AXIS DRIFTS VERY SLOWLY
ACROSS THE REGION FRI/FRI NIGHT...ONLY OVER EASTERN LK SUPERIOR
TO IL BY 12Z SAT. 850MB TEMPS 1.5 TO 2.5 STANDARD DEVIATIONS BELOW
NORMAL ACROSS THE AREA ON FRI. EVEN WITH SUNSHINE ON FRI...REMNANT
SNOW COVER AND COLD 925-850MB TEMPS WILL HOLD HIGHS DOWN. ANOTHER
NIGHT OF STRONGER RADIATIONAL COOLING FRI NIGHT WITH 925MB TEMPS
STILL IN THE -7C TO -10C RANGE AT 12Z SAT. THU THRU FRI NIGHT
CONTINUES TO SHAPE UP AS A PERIOD WITH SOME OF THE COLDEST TEMPS
SINCE MARCH 6TH WITH HIGHS/LOWS 10F TO AS MUCH AS 20F BELOW
NORMAL. USED A BLEND OF THE GUIDANCE HIGHS/LOWS FOR THU THRU FRI
NIGHT.

FOR SATURDAY THRU TUESDAY...DAYS 4 TO 7...

MAIN FCST CONCERNS THIS PERIOD...-RA/-SN CHANCES WITH PASSING
TROUGH/FRONT SAT NIGHT/SUN...TEMPERATURES THRU THE PERIOD.

25.00Z MEDIUM RANGE MODELS CONTINUE GOOD AGREEMENT ON RISING
HGTS/SHORTWAVE RIDGING TO BUILD ACROSS THE UPPER MIDWEST SAT. THIS
AHEAD OF THE NEXT STRONGER SHORTWAVE DROPPING INTO MN SAT NIGHT.
TREND IS STRONGER/SLOWER WITH WITH THIS FEATURE AT 12Z SUN. SOME
TIMING/DETAIL DIFFERENCES AS THE TROUGH/SHORTWAVE ENERGY MOVES
ACROSS THE REGION SUN...BUT MODELS REMAIN IN GOOD AGREEMENT FOR
RISING HGTS/SHORTWAVE RIDGING TO BUILD INTO THE UPPER MIDWEST
MON/TUE. DAY 4-7 FCST CONFIDENCE IS AVERAGE TO GOOD THIS CYCLE.

SHORTWAVE DROPPING TOWARD ND SAT THEN INTO MN SAT NIGHT SPREADS
INCREASING LOW LEVEL WARM ADVECTION ACROSS THE UPPER MIDWEST SAT/SAT
NIGHT. AFTER A COLD START SAT MORNING...TEMPS LOOKING TO RECOVER
RATHER QUICKLY ON SAT. STRONGER TREND OF THE SHORTWAVE TROUGH SAT
NIGHT/SUN SPREADS A STRONGER ROUND OF FORCING/LIFT ACROSS THE FCST
AREA THIS PERIODS. QUESTION REMAINS HOW MUCH MOISTURE WILL BE PULLED
NORTH AHEAD OF THE TROUGH/FRONT...BUT GFS/GEM/ECMWF NOW BRING IN
ENOUGH MOISTURE TO PRODUCE SOME -RA/-SN WITH THE TROUGH PASSAGE.
TIMING DIFFERENCE CONTINUE BUT THIS EXPECTED AT THE DAY 5. CONSENSUS
20-40 PERCENT PRECIP CHANCES SAT NIGHT/SUN SEEM A BIT LOW BUT WILL
LEAVE THEM AT THIS POINT GIVEN THE TIMING DIFFERENCES. BRIEF/QUICK
SHOT OF LOW LEVEL COLD ADVECTION FOLLOWS THE TROUGH/FRONT...AS
STRONGER TROUGHING/ENERGY APPROACHING THE WEST COAST/MOVING INLAND
EARLY NEXT PUSHES RISING HGTS/RIDGING/STRONGER LOW LEVEL WARM
ADVECTION INTO THE NORTH CENTRAL CONUS. LATEST MODEL TREND/CONSENSUS
HAS ABOVE NORMAL 850MB TEMPS ADVECTING INTO THE UPPER MIDWEST BY
TUE. MODEL/ENSEMBLE CONSENSUS OF HIGHS/LOWS FOR SAT THRU TUE APPEARS
WELL TRENDED AT THIS TIME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1216 PM CDT WED MAR 25 2015

DEEP/1004MB LOW PRESSURE ALONG THE MN/ONTARIO BORDER WILL
PUSH EAST ACROSS SOUTHERN ONTARIO THROUGH TONIGHT. CYCLONIC FLOW
ASSOCIATED WITH THE LOW WILL CONTINUE TO INFLUENCE OUR AREA WITH
LOW CLOUDS THIS AFTERNOON AND BREEZY WEST WINDS. WILL LIKELY SEE
GUSTS IN THE 25-35KT RANGE AT KLSE/KRST RESPECTIVELY THROUGH THE
REMAINDER OF THIS AFTERNOON ALONG WITH MVFR STRATOCUMULUS. LOOK
FOR THE CLOUDS TO DISPERSE AND WINDS TO SUBSIDE SOME AFTER SUNSET.
PLAN ON LOW CLOUDS TO ROTATE BACK INTO THE KRST/KLSE TAF SITES
AGAIN BY 08Z LASTING THROUGH THE DAY THURSDAY AS CYCLONIC FLOW
CONTINUES. NORTHWEST WINDS ARE ALSO EXPECTED TO BECOME A BIT GUSTY
AGAIN IN THE 15-25KT RANGE BY 15Z WITH GOOD MIXING THROUGH THE
BOUNDARY LAYER.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION...DAS


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