Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 271737
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1137 AM CST TUE JAN 27 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 333 AM CST TUE JAN 27 2015

MAIN FORECAST CONCERNS THIS PERIOD...CLOUD TRENDS AND TEMPERATURES.

DATA ANALYSIS AT 06Z HAD LOW PRESSURE OVER CENTRAL IL WITH A TROUGH
NORTHWARD THRU WESTERN WI TO THE WEST END OF LK SUPERIOR. BULK OF
PRECIP WITH THIS LOW/TROUGH HAD SHIFTED INTO EASTERN WI BUT A FEW
-SHSN LINGERED ALONG THE MS RIVER FROM AROUND KLSE TO KDVN.
WIDESPREAD IFR TO VFR STRATUS REMAINED ACROSS WI...MUCH OF MN AND
NORTHEAST IA...AND WAS SLOWLY EXPANDING/ADVECTING SOUTH/SOUTHWEST.
ON THIS LATE JANUARY NIGHT...TEMPS UNDER THE CLOUDS STILL IN THE MID
30S ACROSS THE WEST 1/3 OF THE FCST AREA.

NO PROBLEMS NOTED WITH 27.00Z MODEL INITIALIZATIONS. SOLUTIONS VERY
SIMILAR AS HGTS RISE OVER THE REGION TODAY AND SHORTWAVE RIDGING
AHEAD OF SHORTWAVE ENERGY LIFTING THRU THE ROCKIES BUILDS INTO THE
UPPER MIDWEST TONIGHT. TREND FAVORS A COMPROMISE OF THE EARLIER
MODEL RUNS ON THE TROUGHING OVER WY AT 12Z WED. SHORT-TERM FCST
CONFIDENCE IS GOOD THIS CYCLE...THOUGH NUANCES OF LOW CLOUD/STRATUS
FCSTS THIS TIME OF YEAR ARE ALWAYS TRICKY.

FOR THE SHORT TERM...FLURRIES IN THE AREA COMING TO AN END EARLY
THIS MORNING AS THE LAST OF THE LIFT EXITS...PRESSURES RISE AND THE
SFC-850MB TROUGH EXITS THE AREA. HOWEVER...THE LINGERING LOW CLOUDS
AND THEIR IMPACT ON BOTH HIGHS/LOWS TODAY/TONIGHT WILL REMAIN
PROBLEMATIC. LATEST AVAILABLE PILOT REPORTS INDICATE LOW CLOUD DECK
IS ABOUT 1500 FT THICK WITH MODEL SOUNDINGS AND 925MB RH PROGS
SHOWING THIS MOISTURE TO REMAIN TRAPPED IN/UNDER AN INVERSION NEAR
925MB TODAY...ESPECIALLY OVER THE CENTRAL/EAST PARTS OF THE FCST
AREA. LIGHT WINDS AROUND 925MB AND BELOW WILL NOT HELP ADVECT THIS
MOISTURE/CLOUDS ANYWHERE FAST TODAY EITHER. RAISED CLOUD COVER FOR
TODAY...ESPECIALLY OVER THE EASTERN 2/3 OF THE FCST AREA AND LOWERED
HIGHS A BIT THESE AREAS. WITH POTENTIAL FOR SOME SUNSHINE IN THE
WEST AND A WARM START...RAISED HIGHS A BIT OVER MUCH OF SOUTHEAST
MN/NORTHEAST IA. MODEL SOUNDINGS/X-SECTIONS SHOW A DECREASE OF SFC-
925MB MOISTURE TONIGHT...BUT INCREASING 850MB WARM ADVECTION AS THE
MID LEVEL SHORTWAVE RIDGE BUILDS IN STRENGTHENS THE LOW LEVEL
INVERSION. THIS WITH A SLOW INCREASE OF ASCENT AHEAD OF THE NEXT LOW
DEVELOPING IN THE PLAINS. SUSPECT LOW CLOUDS WILL BE STUBBORN/
PERSISTENT YET TONIGHT AND RAISED CLOUD COVER. TRENDED LOWS UP A BIT
TONIGHT TO ACCOUNT FOR THE CLOUDS BUT STAYED WITH A NICE BLEND
AGAINST THE NEIGHBORS. HOWEVER...SUSPECT LOWS TONIGHT MAY STILL BE
TOO COOL IF THE CLOUDS HANG ON...ESPECIALLY OVER THE EAST END OF THE
FCST AREA.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 333 AM CST TUE JAN 27 2015

MAIN FCST CONCERNS FOR WED THRU THU NIGHT...MAINLY DZ/FZDZ CHANCES
WED NIGHT/THU MORNING...TEMPERATURES THRU THE PERIOD...ESPECIALLY
HIGHS ON WED.

27.00Z MODELS IN GOOD AND IMPROVING AGREEMENT AS THE WY SHORTWAVE
ENERGY MOVES INTO NEB WED THEN INTO IL WED NIGHT. THIS AS A NORTHERN
STREAM WAVE ALSO DROPS ACROSS MN WED NIGHT. TREND FAVORS A
COMPROMISE OF THE EARLIER RUNS WITH THESE FEATURES. TREND SHOWS A
TIGHTENING AND STRONGER WITH A SECOND NORTHERN STREAM WAVE TO DROP
ACROSS THE GREAT LAKES THU/THU NIGHT. FCST CONFIDENCE IN THE WED
THRU THU NIGHT PERIOD IS AVERAGE TO GOOD.

FIRST UP IS THE POTENTIAL FOR VERY WARM/UNSEASONABLY MILD TEMPS ON
WED. LITTLE OR NO SNOW COVER WEST/SOUTH OF THE FCST AREA TO IMPEDE
LOW LEVEL WARM AIR FROM COMING NORTH AHEAD OF THE PLAINS LOW ON WED.
SOME VARIABILITY AMONG THE MODELS YET BUT GENERAL CONSENSUS FOR 850MB
TEMP IN THE -1C TO +4C RANGE OVER THE FCST AREA AT 00Z THU. GRANTED
850MB AIR WOULD NOT MIX TO THE SFC...BUT SHOWS A VERY WARM BUBBLE OF
OVER THE FCST AREA ON WED. SOUTH-SOUTHEAST GRADIENT WINDS LOOK TO
INCREASE INTO THE 10-20KT RANGE FOR MIXING WED. QUESTION WILL BE
EXTENT OF CLOUD COVER AND HOW QUICKLY 925-800MB MOISTURE INCREASES
OVER THE AREA...WHICH WOULD AGAIN LIMIT DIURNAL WARMING/MIXING. FOR
NOW USED THE MODEL/ENSEMBLE BLEND OF HIGHS MOSTLY IN THE MID 30S TO
LOW 40S UNTIL THE CLOUD DETAILS BECOME CLEARER.

MODEL SOUNDINGS/X-SECTIONS SHOW THE MOISTURE INCREASE WED NIGHT
GENERALLY TOPS OUT AROUND 800MB...WITH CLOUD TOP TEMPS MOSTLY WARMER
THAN -5C. APPEARS ICE WILL BE LACKING IN THE CLOUDS WED NIGHT INTO
THU MORNING. 925-850MB WARM ADVECTION AND PASSAGE OF THE SFC-85M0MB
TROUGH PRODUCES CONVERGENCE/LIFT IN THE LOWER SATURATED PORTION OF
THE COLUMN. PREVIOUS SHIFT TRENDED PRECIP CHANCES WED NIGHT/THU
TOWARD -DZ/-FZDZ AND THIS LOOKS GOOD. MODELS GENERALLY PRODUCING A
VERY LIGHT QPF/DRIZZLE PRECIP SIGNATURE ACROSS THE FCST AREA AS
WELL. IF -FZDZ STARTS TO LOOK CERTAIN FOR SOME PORTIONS OF THE FCST
AREA...BASED ON SFC TEMPS WED NIGHT...MAY NEED ANOTHER WINTER
WEATHER ADVISORY...AS WE WERE REMINDED MON THAT IT TAKES VERY
LITTLE -FZDZ TO MAKE UNTREATED ROADS SLICK. DID LIMIT SMALL PRECIP
CHANCES THU TO THE MORNING HOURS WITH PASSAGE OF THE TROUGH AXIS
EAST AND LOW LEVEL COLD ADVECTION/SUBSIDENCE SPREADING ACROSS THE
AREA. SHORTWAVE DROPPING ACROSS THE GREAT LAKES DRIVES A STRONGER
SHOT OF LOW LEVEL COLD ADVECTION SOUTHWARD ACROSS THE UPPER
MIDWEST FOR LATER THU/THU NIGHT. APPROACH OF THE CAN SFC HIGH AND
925-850MB RIDGE AXIS/ DIFFLUENT FLOW SHOULD CLEAR OUT THE CLOUDS
THU NIGHT. GENERALLY FOLLOWED A BLEND OF THE GUIDANCE LOWS/HIGHS
FOR WED NIGHT THRU THU NIGHT...WITH THU NIGHT LOWS CLOSER TO LATE
JAN NORMALS.

FOR FRIDAY THRU MONDAY.../DAYS 4 TO 7/...

MAIN FCST CONCERNS THIS PERIOD...TEMPERATURE COOL-DOWN AND SNOW
CHANCES SAT NIGHT INTO SUNDAY.

27.00Z MEDIUM RANGE MODELS IN DECENT AGREEMENT FRI/FRI NIGHT FOR
RISING HGTS/WEAK SHORTWAVE RIDGING TO BUILD ACROSS THE UPPER
MIDWEST. TREND FOR SAT IS HIGHER HGTS/FLATTER FLOW OVER THE
REGION...AHEAD OF STRONGER NORTHERN STREAM SHORTWAVE TO DROP INTO
THE NORTHERN PLAINS AND PARTLY PHASE WITH SOUTHERN STREAM ENERGY SAT
NIGHT. MODELS REMAIN IN GOOD AGREEMENT FOR COLD TROUGHING TO SETTLE
OVER THE UPPER MIDWEST/GREAT LAKES SUN INTO MON. HOWEVER...DUE TO
THE TRENDS THE RUN-TO-RUN CONSISTENCY MUCH OF THE FRI THRU MON
PERIOD LEAVES A BIT TO BE DESIRED. OVERALL DAY 4-7 FCST CONFIDENCE
IS AVERAGE THIS CYCLE.

CAN HIGH PRESSURE SET TO DRIFT ACROSS THE AREA FRI WITH PARTLY
CLOUDY/MOSTLY SUNNY SKIES AND HIGHS NEAR LATE JAN NORMALS. EARLIER
GFS RUNS WERE TRENDING TOWARD A SNOW CHANCE ACROSS THE FCST AREA
CENTERED ON SAT NIGHT WITH TEMPS REMAINING NEAR TO ABOVE NORMAL THRU
SAT NIGHT. BOTH GFS/ECMWF NOW SPREAD A ROUND OF INCREASING SFC-500MB
MOISTURE AND LOWER LEVEL THERMO-DYNAMIC FORCING/LIFT ACROSS THE AREA
FROM SAT AFTERNOON INTO SUN MORNING. 20-40 PERCENT SNOW CHANCES
CENTERED ON SAT NIGHT LOOK GOOD FOR NOW. STRONGER LOW LEVEL COLD
ADVECTION/ARCTIC AIR NOW LOOKS ON TRACK TO SPREAD ACROSS THE REGION
LATER SUN INTO MON. 925MB TEMPS PROGGED IN THE -17C TO -23C RANGE AT
12Z MON. MODEL/ENSEMBLE CONSENSUS OF HIGHS/LOWS FOR FRI THRU MON
APPEAR WELL TRENDED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1136 AM CST TUE JAN 27 2015

SOUNDINGS CONTINUE TO SHOW THAT THE LOW LEVEL MOISTURE WILL REMAIN
TRAPPED BELOW THE SUBSIDENCE INVERSION THROUGH TONIGHT. CEILINGS
WILL BE MVFR THIS AFTERNOON AND THEN IFR/MVFR TONIGHT. WINDS WILL
BECOME SOUTHEAST EARLY THIS AFTERNOON AND REMAIN IN THE 5 TO
10 KNOT RANGE THROUGH TONIGHT. AS THE PRESSURE GRADIENT INCREASES
AHEAD OF THE NEXT SHORT WAVE TROUGH...THE SOUTHEAST WINDS WILL
CLIMB INTO THE 10 TO 20 KNOT RANGE. WIND GUSTS AT KRST WILL CLIMB
TO AROUND 25 KNOTS AFTER 28.14Z.

LOOKING AHEAD TO WEDNESDAY NIGHT...IT CONTINUES TO LOOK LIKE
FREEZING DRIZZLE WILL DEVELOP DURING THE LATE AFTERNOON/EVENING AT
KRST AND DURING THE EVENING AT KLSE.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION...BOYNE


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