Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 260817
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
317 AM CDT THU MAR 26 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 317 AM CDT THU MAR 26 2015

MAIN FCST CONCERNS THIS PERIOD...CLOUDS AND TEMPERATURES.

06Z DATA ANALYSIS HAD LOW PRESSURE OVER WESTERN QUEBEC WITH
TROUGHING/SECONDARY COLD FRONT WESTWARD ACROSS LK SUPERIOR AND
NORTHERN MN. WV IMAGERY SHOWED TROUGHING OVER THE UPPER MIDWEST
WITH PIECES OF SHORTWAVE ENERGY UPSTREAM ACROSS CENTRAL CAN.
MOISTURE/CLOUDS IN THE LOWER LEVEL CYCLONIC FLOW CONTINUED TO ROTATE
OVER THE NORTHEAST HALF OF THE REGION WHILE SKIES WERE CLEARING OVER
THE SOUTHWEST HALF...WITH THE CLEAR/CLOUDY LINE SPLITTING THE FCST
AREA EARLY THIS MORNING. GRADIENT NORTHWEST WINDS OF 5-15 MPH
KEEPING THE BOUNDARY LAYER STIRRED THIS MORNING...AND TEMPERATURES
RATHER UNIFORM IN THE UPPER 20S-MID 30S REGION-WIDE.

26.00Z MODEL RUNS LOOK TO HAVE INITIALIZED QUITE WELL. SOLUTIONS
VERY SIMILAR THRU TODAY/TONIGHT AS ADDITIONAL SMALLER PIECES OF
SHORTWAVE ENERGY IN THE FLOW CARVE OUT A DEEP LONGWAVE TROUGH OVER
THE GREAT LAKES/MS VALLEY BY 12Z FRI. OVERALL TREND IS A TIGHTER
CONSENSUS OF THE EARLIER RUNS. SHORT-TERM CONFIDENCE IS GOOD THIS
CYCLE.

FOR THE SHORT TERM...PIECES OF SHORTWAVE ENERGY AND DEEPENING MID
LEVEL TROUGH OVERHEAD SENDS A WEAK SFC-850MB TROUGH/BACK-DOOR COLD
FRONT SOUTH ACROSS THE REGION TODAY. LOWER LEVEL FLOW OVER THE AREA
BECOMES MORE NORTHERLY THRU THE DAY. WITH PLENTY OF STRATUS UPSTREAM
ACROSS EASTERN MAN/WESTERN ONT/NORTHERN MN AND TIGHTER CYCLONIC LOW
LEVEL FLOW OVER MN/IA/WI...APPEARS CLOUDS ARE HERE TO STAY THRU THE
DAY ESPECIALLY ACROSS THE NORTHEAST 1/2 TO 2/3 OF THE FCST AREA.
WILL HAVE TO RAISE CLOUD COVER IN THE FCST GRIDS ACROSS MUCH OF THE
FCST AREA TODAY. WARMER LOWS THIS MORNING PLUS MORE CLOUDS TODAY...
HIGHS CLOSE TO THOSE OF WED LOOK REASONABLE. SOME SIGNAL CLOUDS MAY
BE TOUGH TO GET RID OF TONIGHT. WILL REMAIN OPTIMISTIC THAT PASSAGE
OF THE SHORTWAVE ENERGY/MID LEVEL TROUGH AXIS AND MORE ANTI-CYCLONIC
SFC-850MB FLOW WILL BE ENOUGH TO SCOUR OUT THE CLOUDS. LOWS TRICKY
TONIGHT BASED ON IF CLOUDS CLEAR OR NOT. A MORE FAVORABLE NIGHT FOR
RADIATIONAL COOLING WITH LIGHTER SFC WINDS AS THE SFC RIDGE AXIS
APPROACHES. LIGHT WINDS...CLEAR SKIES AND 925MB TEMPS IN THE -8C TO
-13C RANGE WOULD ALLOW FOR SOME OF THE COLDEST LOWS WE/VE SEEN
ACROSS THE FCST AREA SINCE MARCH 7TH. HOWEVER...IF THE CLOUD BLANKET
HOLDS...LOW TEMPS IN THE FCST GRIDS COULD EASILY BE 1 TO 2
CATEGORIES TOO COLD. FOR NOW BANKED ON THE CLOUDS CLEARING TONIGHT
AND STAYED WITH A BLEND OF THE GUIDANCE HIGHS/LOWS TODAY/TONIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 317 AM CDT THU MAR 26 2015

MAIN FCST CONCERNS FOR FRI THRU SAT NIGHT...COLD TEMPERATURES FRI
INTO SAT...PRECIP CHANCES LATE SAT NIGHT.

26.00Z MODELS IN GOOD AGREEMENT FOR THE DEEP MID LEVEL TROUGH TO
CONTINUE MOVING EAST FRI/FRI NIGHT...WHILE A SHORTWAVE DROPPING DOWN
THE WEST SIDE OF THE TROUGH KEEPS HGTS LOWER OVER THE REGION THRU
12Z SAT. TIGHT CONSENSUS FOR HGTS TO THEN QUICKLY RISE OVER THE
REGION SAT...AHEAD OF THE STRONGER SHORTWAVE ENERGY INTO CENTRAL/
EASTERN MT BY 00Z SUN. STILL SOME TIMING/DETAIL DIFFERENCES BY SAT
NIGHT BUT STRONG SIGNAL FOR THE SHORTWAVE TROUGH TO MOVE QUICKLY
INTO THE EASTERN DAKOTAS/WESTERN MN BY 12Z SUN. FCST CONFIDENCE IS
GOOD FRI THRU SAT THEN AVERAGE SAT NIGHT WITH THE TIMING DIFFERENCES.

UPPER MIDWEST REMAINS UNDER COLD MID LEVEL TROUGHING FRI/FRI NIGHT
AS COLD CAN HIGH PRESSURE DRIFTS SLOWLY SOUTHEAST ACROSS THE REGION.
HIGH IS STILL CENTERED OVER THE U.P. OF MI WITH RIDGING INTO IL AT
12Z SAT. WITH LIGHT LOW LEVEL WINDS...THE COLD AIRMASS FROM 12Z FRI
ONLY SLOWLY MODERATES IN PLACE WITH 925MB STILL IN THE -5C TO -9C
RANGE AT 12Z SAT. EVEN WITH PLENTY OF SUNSHINE FRI...925MB ONLY
SUPPORTING HIGHS IN THE 30S. LIGHT WINDS/CLEAR SKIES WITH THE SFC
RIDGE OVERHEAD SHOULD MAKE FRI NIGHT AS COLD OR COLDER THAN THU
NIGHT EVEN AS 925MB TEMPS WARM A BIT...ESPECIALLY EAST OF THE MS
RIVER. SHORTWAVE DROPPING DOWN THE WEST SIDE OF THE TROUGH FRI
NIGHT/SAT MORNING PASSES WEST OF THE FCST AREA...LOOKING TO DO
LITTLE MORE THAN SPREAD SOME MID/HIGH CLOUDS OVER THE WEST HALF OF
THE FCSTR AREA AS IT PASSES. SHORTWAVE RIDGING QUICKLY BUILDS IN SAT
WITH DEVELOPING TROUGHING IN THE PLAINS PUSHING THE CAN HIGH EAST.
SOUTH FLOW/LOW LEVEL WARM ADVECTION QUICKLY SPREADS ACROSS THE
REGION SAT. COMBINED WITH PLENTY OF SUNSHINE...A STRONG DIURNAL TEMP
RISE EXPECTED SAT. LOW LEVEL WARM ADVECTION STRENGTHENS SAT NIGHT AS
THE SFC TROUGH AND SHORTWAVE TROUGH MOVE TOWARD/INTO WESTERN MN.
MOISTURE STARTS TO INCREASE SAT EVENING...WITH MODEL SOUNDINGS AND X-
SECTIONS SHOWING THE INCREASING MOISTURE IN THE SFC-700MB LAYER
ARRIVING AFTER MIDNIGHT. GFS/NAM FASTER BRINING THIS IN LATER SAT
NIGHT WHILE ECMWF/GEM BRING IT IN SUNDAY. LEFT SAT EVENING DRY. LEFT
PRECIP CHANCES LATE SAT NIGHT IN THE 15-30 PERCENT RANGE PENDING A
TIGHTER TIMING CONSENSUS AMONG THE MODELS. WARMING TEMPS ALOFT LATER
SAT NIGHT LOOKING TO PRODUCE A TRANSITION TO A WINTRY MIX OR -RA
ACROSS THE WEST END OF THE FCST AREA BY 12Z SUN AS WELL. GENERALLY
USED A BLEND OF THE GUIDANCE HIGHS/LOWS FOR FRI THRU SAT NIGHT.

FOR SUNDAY THROUGH WEDNESDAY...DAYS 4 TO 7...

MAIN FCST CONCERNS THIS PERIOD...PRECIP CHANCES SUNDAY...MON AND TUE
NIGHT/WED...TEMPERATURES THRU THE PERIOD.

MEDIUM RANGE MODEL RUNS OF 26.00Z IN GENERAL AGREEMENT ON A
SHORTWAVE TROUGH MOVING ACROSS THE UPPER MIDWEST SUNDAY BUT CONTINUE
WITH SOME TIMING/DETAIL DIFFERENCES ON THE SHORTWAVE/TROUGH AXIS
PASSAGE. MODELS REMAIN IN GOOD LARGE-SCALE AGREEMENT MON WITH
EASTERN NOAM TROUGHING AND WESTERN NOAM RIDGING...WITH THIS PATTERN
PROGRESSING TUE AS STRONGER TROUGHING MOVES INTO THE PAC NORTHWEST.
HOWEVER MODELS DIFFER ON SHORTWAVE DETAILS IN THE FLOW ACROSS THE
REGION MON WITH POTENTIAL IMPACTS ON THE SENSIBLE WEATHER. MODELS IN
REASONABLY GOOD AGREEMENT FOR THE PAC NORTHWEST SHORTWAVE TO MOVE
INTO THE NORTH-CENTRAL CONUS BY LATE WED. GIVEN THE TIMING
DIFFERENCES...DAY 4-7 FCST CONFIDENCE IS AVERAGE THIS CYCLE.

PASSING SHORTWAVE/TROUGH SUN PUSHES A SFC TROUGH/WARM FRONT ACROSS
THE AREA. AGAIN NAM/GFS FASTER WITH THIS THAN ECMWF/GEM...AND WOULD
HAVE PRECIP EAST OF THE FCST AREA BY SUN AFTERNOON. ECMWF/GEM WOULD
SPREAD BULK OF PRECIP ACROSS THE AREA LATER SUN MORNING/AFTERNOON.
SFC-805MB WARMING SPREADS QUICKLY ACROSS THE AREA SUN MORNING...WITH
ANY PRECIP SUNDAY AS -RA AFTER 15-16Z. UNTIL TIMING DETAILS REACH A
BETTER CONSENSUS...30-50 PERCENT PRECIP CHANCES SUNDAY REASONABLE.
STRONGER GEM/ECMWF SHORTWAVE DROPPING SOUTHEAST ACROSS THE UPPER
MIDWEST MON WOULD SPREAD ANOTHER -RA CHANCE ACROSS THE FCST AREA.
SHORTWAVE RIDGING/RISING HGTS TUE WOULD SPREAD A DRY/MILD DAY ACROSS
THE UPPER MIDWEST ON TUE...WHILE NEXT APPROACHING SHORTWAVE TROUGH
SPREADS -RA CHANCES BACK INTO THE FCST AREA FOR TUE NIGHT/WED.
MODEL/ENSEMBLE CONSENSUS PRECIP CHANCES FOR MON-WED OKAY UNTIL THE
MODELS REACH A TIGHTER TIMING AND STRENGTH CONSENSUS ON THE DETAILS.

SUN-WED CONTINUES TO TREND TOWARD A PERIOD OF WARMER/ABOVE NORMAL
TEMPS WITH MORE WESTERLY VS. NORTHWEST AND NORTH MID LEVEL FLOW.
MODEL/ENSEMBLE CONSENSUS HIGHS/LOWS FOR SUN-WED APPEAR WELL TRENDED
AT THIS TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1148 PM CDT WED MAR 25 2015

SOME CLEARING OF LOWER CEILINGS HAS MADE ITS WAY INTO PORTIONS OF
SOUTHEAST MN AND NORTHEAST IA AND WILL CONTINUE TO PUSH EAST
OVERNIGHT RESULTING IN VFR CONDITIONS AT BOTH KRST/KLSE. LATEST
FORECAST GUIDANCE SUGGESTS MVFR CEILINGS TO BUILD BACK ACROSS TAF
AIRFIELDS BY MID-THURSDAY MORNING BUT RISE ABOVE 3000 FT AGL MID BY
MID-AFTERNOON. WEST-NORTHWEST WIND WILL PERSIST THROUGH THE
PERIOD...GENERALLY FROM 10 TO 15 KTS WITH SOME HIGHER GUSTS POSSIBLE
AT TIMES ON THURSDAY.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION.....ROGERS


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