Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 102043
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
243 PM CST WED FEB 10 2016

.SHORT TERM...(TONIGHT THRU THURSDAY NIGHT)
ISSUED AT 243 PM CST WED FEB 10 2016

MAIN FCST CONCERNS THIS PERIOD...COLD TEMPERATURES...SMALL -SN
CHANCES SOUTHWEST LATE THU NIGHT.

18Z DATA ANALYSIS HAD A WEAK RIDGE OF HIGH PRESSURE FROM NORTHERN MN
TO SOUTHERN IL...WITH LOW PRESSURE CENTERED OVER NEB/SD. BAND OF FN
CONVERGENCE/ISENTROPIC LIFT IN A TIGHT BAROCLINIC ZONE SNOW WAS
SPREADING SOUTHEAST ACROSS SOUTHWEST MN THRU CENTRAL INTO SOUTHEAST
IA. HEAVIEST OF THIS PASSING SOUTH OF I-80 AS OF MID-DAY. THIS
FORCING/LIFT AND A SHORTWAVE DROPPING SOUTHEAST ACROSS MN PRODUCING
CLOUDS OVER THE SOUTHWEST HALF OF THE REGION...WITH PARTLY CLOUDY/
MOSTLY SUNNY SKIES OVER MUCH OF THE NORTHEAST HALF OF THE REGION.
EVEN WITH SOME SUNSHINE...TEMPS ACROSS THE UPPER MIDWEST ON THE COLD
SIDE TODAY WITH MID-DAY TEMPS MOSTLY IN THE 5 TO 20 ABOVE RANGE.

MODEL RUNS OF 10.12Z INITIALIZED WELL. SOLUTIONS VERY SIMILAR AS
RATHER CHANNELIZED SHORTWAVE ENERGY SLIDES SOUTHEAST ACROSS THE
REGION THIS AFTERNOON/THIS EVENING...WITH THE MID LEVEL JET AXIS
THEN SHIFTING EAST OF THE AREA FOR LATER TONIGHT/THU. TIGHT
CONSENSUS FOR ANOTHER CHANNELED SHORTWAVE TO SLIDE SOUTHEAST ACROSS
THE DAKOTAS THU NIGHT WHILE ANOTHER WAVE DROPS TOWARD NORTHERN MN
AND LK SUPERIOR. TREND FAVORS A COMPROMISE OF THE EARLIER RUNS ON
THESE FEATURE WITH THE SHORT-TERM FCST CONFIDENCE GOOD THIS CYCLE.

IN THE SHORT TERM...WITH PASSAGE OF THE SHORTWAVE THIS AFTERNOON/
EVENING RENEWED LOW LEVEL COLD ADVECTION SPREADS ACROSS THE AREA.
THIS AS THE NEXT CANADIAN/ARCTIC HIGH BUILDS SOUTH INTO THE UPPER
MIDWEST. LIGHT/DECOUPLED WINDS TONIGHT NEAR THE SFC RIDGE AXIS...
UNDER WHAT SHOULD BE CLEAR/MOSTLY CLEAR SKIES. 925MB TEMPS IN THE
-15C TO -18C RANGE AT 12Z THU...FOR WHAT PROMISES TO BE A NIGHT OF
WIDESPREAD SUB-ZERO LOWS. NAEFS SHOWS 850MB TEMPS AROUND 1 STD
DEVIATION BELOW NORMAL THU MORNING. FAVORED COLDER OF GUIDANCE LOWS
TONIGHT. WIND CHILLS LATER TONIGHT/THU MORNING ONLY LOOKING TO BE IN
THE -10 TO -20 RANGE...MAINLY DUE TO THE LIGHT/VARIABLE WINDS.
LITTLE LOW LEVEL ADVECTIONS OVER THE AREA THU WITH THE SFC-850MB
RIDGE AXIS NEAR/OVER THE AREA. WITH WHAT SHOULD BE PLENTY OF
SUNSHINE THU...MODEL SOUNDINGS SHOWING MIXING TO ABOUT 925MB.
HOWEVER 925MB TEMPS THU AFTERNOON ONLY LOOK TO SUPPORT HIGHS TEENS.
WAVE DROPPING SOUTHEAST ACROSS THE DAKOTAS THU NIGHT SPREADS A ROUND
OF LOWER LEVEL WARM ADVECTION/ISENTROPIC LIFT ACROSS THE AREA.

STRONGER OF THE LIFT/GREATER OF THE MOISTURE IS WEST/SOUTH OF THE
FCST AREA THU NIGHT...IN THE TIGHTER BAROCLINIC ZONE NEAR THE TRACK
OF THE SHORTWAVE. APPEARS A BAND OF -SN WILL PASS WEST/SOUTH OF THE
FCST AREA THU NIGHT...WITH THE QUESTION OF WHERE WILL THE NORTHEAST
EDGE OF -SN BAND BE. MUCH OF THE LIFT OVER THE FCST AREA LOOKS TO
WORK TO SATURATE THE COLUMN AND BY THE TIME THIS OCCURS THE LIFT IS
ON ITS WAY OUT. FEW OF THE MODELS INDICATING COLUMN WOULD SATURATE
ENOUGH FOR SOME -SN OVER THE SOUTHWEST END OF THE FCST AREA DURING
THE LATE EVENING INTO OVERNIGHT HOURS. CONTINUED SOME 20-30 PERCENT
-SN CHANCES OVER ABOUT THE SOUTHWEST 1/4 OF THE FCST AREA FOR THIS.
ANY -SN AMOUNTS THU NIGHT LOOKING TO BE LITTLE MORE THAN A DUSTING.
USED A BLEND OF THE GUIDANCE HIGHS/LOWS FOR THU/THU NIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 243 PM CST WED FEB 10 2016

FOR FRIDAY THRU SATURDAY NIGHT...

MAIN FCST CONCERNS THIS PERIOD...WIND CHILLS LATE FRI NIGHT/SAT
MORNING...RETURNING -SN CHANCES SAT NIGHT...BELOW NORMAL TEMPS
THRU THE PERIOD.

10.12Z MODELS IN GOOD AGREEMENT FOR THE DAKOTAS SHORTWAVE ENERGY
FROM THU NIGHT TO QUICKLY PASS WELL SOUTH/WEST OF THE FCST AREA FRI
MORNING. THIS WHILE THE NORTHERN MN/LK SUPERIOR ENERGY ROTATES
SOUTHEAST ACROSS THE WESTERN GREAT LAKES. TIGHTENING CONSENSUS FOR
HGTS TO START RISING FRI NIGHT...BEHIND THE DEPARTING TROUGH AND A
AHEAD OF A STRONGER SHORTWAVE HEADED INTO THE NORTHERN PLAINS BY
LATE SAT. BY SAT NIGHT THE WAVE IS PROGGED TO BE MOVING INTO THE
UPPER MIDWEST...BUT TIMING DIFFERENCES DEVELOP AMONG THE MODELS.
FCST CONFIDENCE REMAINS GOOD FRI THRU SAT THEN IS AVERAGE FOR SAT
NIGHT.

WAVE PASSING ACROSS THE WESTERN GREAT LAKES FRI LOOKS TO DO LITTLE
MORE THAN ENHANCE THE LAKE EFFECT SNOW IN THE LEE OF THE LAKES AS IT
PASSES. DRIER AIR ABOVE 850MB AND DEEP LAYERED SUBSIDENCE SPREADS
OVER THE FCST AREA FRI WEST OF/BEHIND THIS WAVE...FOR A DRY PERIOD
FRI/FRI NIGHT. THIS WAVE DOES OPEN THE DOOR FOR ONE LAST LARGE...
COLD CAN/ARCTIC HIGH TO BUILD SOUTH INTO/ACROSS THE UPPER MIDWEST
FRI INTO SAT. CENTER OF THIS HIGH IS OVER MN FRI NIGHT...FOR WHAT
WOULD BE NORTHWEST GRADIENT WINDS 5-10 MPH ACROSS THE FCST AREA FRI
NIGHT INTO SAT MORNING. THIS WITH 925MB TEMPS IN THE -19C TO -23C
RANGE AND NAEFS INDICATING 850MB TEMPS 1 TO 2 STD DEVIATIONS BELOW
NORMAL AT 12Z SAT. FRI NIGHT LOWS TRENDING TO BE THE COLDEST OF THE
PAST SEVERAL NIGHTS...BUT THE GRADIENT WINDS LOOK TO KEEP THE
BOUNDARY LAYER STIRRED A BIT AND LOWS FROM FULLY BOTTOMING OUT. DID
FAVOR COLDER OF GUIDANCE LOWS FRI NIGHT AND TRENDED SOME LOWS TOWARD
-20F IN THE LOWER LAYING AREAS ALONG/NORTHEAST OF I-94 WHERE WINDS
ARE MORE PRONE TO DECOUPLING. THE WINDS AND LOWS IN THE -5F TO -20F
RANGE WILL SEND WIND CHILLS LATER FRI NIGHT INTO SAT MORNING INTO
THE -20 TO -30 RANGE. A WIND CHILL ADVISORY IS LOOKING NECESSARY FOR
LATER FRI NIGHT THRU MUCH OF SAT MORNING...BUT PLENTY OF TIME TO
DETAIL AND ISSUE THAT BEFORE FRI NIGHT. SAT TO BE A COLD DAY WITH
THE COLD START AND THE SFC-850MB RIDGE AXIS NEAR/OVER THE AREA FOR
LITTLE IN THE WAY OF ADVECTIONS TO CHANGE THE AIRMASS. THE HIGH IS
QUICKLY PUSHED EAST OF THE AREA SAT NIGHT...WITH INCREASING
SOUTHEAST WINDS ON ITS BACKSIDE AND INCREASING CLOUDS AHEAD OF THE
NEXT LOW/TROUGH/SHORTWAVE INTO THE NORTHERN PLAINS. LOWS SAT NIGHT
TO BE IN THE EVENING...WITH STEADY/SLOWLY RISING TEMPS AFTER
MIDNIGHT...ESPECIALLY WEST OF THE MS RIVER. BY LATER SAT NIGHT...
INCREASING MOISTURE AND LOWER LEVEL THERMO-DYNAMIC FORCING ALREADY
PROGGED INTO THE WEST SIDE OF THE FCST AREA BY THE FASTER OF THE
MODELS. CONTINUED WITH SOME 20-40 PERCENT -SN CHANCES MAINLY ALONG/
WEST OF THE MS RIVER AND MAINLY AFTER MIDNIGHT SAT NIGHT. USED A
BLEND OF THE GUIDANCE HIGHS/LOWS FRI/SAT/SAT NIGHT.

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

MAIN FCST CONCERNS THIS PERIOD...SNOW CHANCES SUN INTO SUN NIGHT AND
MAINLY SNOW CHANCES AGAIN TUE/TUE NIGHT...WARMING TEMPERATURES.

MEDIUM RANGE MODEL RUNS OF 02.10Z/02.12Z OFFER IMPROVING AGREEMENT
ON A STRONGER SHORTWAVE/TROUGH TO BE MOVING INTO THE UPPER MIDWEST
SUN THEN ACROSS THE REGION SUN NIGHT. LOOSER AGREEMENT FOR HGTS TO
RISE AND WEAK SHORTWAVE RIDGING TO BUILD ACROSS THE REGION MON/MON
NIGHT. EVEN LESSER AGREEMENT ON THE DETAILS BY TUE...BUT SOME SIGNAL
AMONG GFS/ECMWF FOR ANOTHER NORTHWEST FLOW SHORTWAVE TO DROP INTO
THE NORTHERN PLAINS TUE THEN ACROSS THE UPPER MIDWEST TUE NIGHT...
WITH RISING HGTS/RIDGING BUILD IN WED. FCST CONFIDENCE IS AVERAGE
SUN...THEN WITH THE INCREASING DETAIL DIFFERENCES BELOW AVERAGE BY
TUE/WED.

COLD SFC HIGH TO RETREAT EAST SUNDAY AS THE NEXT STRONGER SHORTWAVE
TROUGH BRINGS LOW PRESSURE AND INCREASING SFC-700MB MOISTURE/WARM
ADVECTION/ISENTROPIC LIFT EASTWARD INTO THE REGION. DEPTH OF THE
MOISTURE COLUMN/PW VALUES LOOKING SUITABLE FOR THE SHORTWAVE AND
LOWER LEVEL THERMO-DYNAMIC FORCING TO SQUEEZE OUT SOME SNOW ACROSS
THE AREA SUN INTO SUN EVENING. CONSENSUS SNOW CHANCES SUNDAY IN THE
50 PERCENT RANGE ARE LIKELY A BIT LOW BUT WILL LEAVE THEM AS IS FOR
NOW AS TREND OF RECENT MODEL RUNS IS TOWARD LESS PRECIP WITH THIS
WAVE/TROUGH. MONDAY WOULD BE A BETWEEN-SYSTEMS DAY WITH PASSAGE OF
THE MID LEVEL TROUGH AXIS. HOWEVER MODELS WANTING TO DROP A WEAK
SECONDARY SHORTWAVE INTO THE TROUGH...KEEPING CYCLONIC FLOW ALOFT
OVER THE AREA ON MON. LINGERING SMALL -SN OR FLURRY CHANCES OKAY AT
THIS POINT. BIGGER THING BY MON IS WESTERLY LOWER LEVEL FLOW/WARM
ADVECTION RETURNING LOWER LEVEL TEMPS TOWARD NORMAL. AFTER A WEEK IN
THE DEEP FREEZE...HIGHS MONDAY TRENDING TO BE NEAR 30F. NEXT WAVE
THRU THE FLOW /STRONGER IN ECMWF/ WOULD SPREAD ANOTHER ROUND OF
STRONGER MOISTURE ADVECTION/THERMO-DYNAMIC FORCING/LIFT ACROSS THE
AREA TUE/TUE NIGHT INTO WED. BIGGER TIME SPREAD TUE-WED WITH THE
MODEL DETAIL DIFFERENCES. DEPENDING ON MODEL...PERHAPS ENOUGH WARM
AIR DRAWN NORTHWARD FOR PRECIP TYPE ISSUES TUE/TUE NIGHT...
ESPECIALLY ACROSS THE SOUTH 1/2 OF THE FCST AREA. PRECIP CHANCES IN
THE 20-30 PERCENT RANGE TUE-WED REASONABLE FOR NOW. LOWER LEVEL
WARMING WOULD CONTINUE TUE/WED...WITH TEMPS TRENDING NEAR/ABOVE
NORMAL. MODEL/ENSEMBLE CONSENSUS OF HIGHS/LOWS FOR SUN-WED APPEAR
WELL TRENDED AT THIS TIME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1100 AM CST WED FEB 10 2016

AN UPPER LEVEL SHORTWAVE TROUGH WAS STREAKING SOUTHWEST ACROSS THE
REGION...PRODUCING A BAND OF -SN FROM WESTERN MN INTO IA. TREND AND
TRACK OF THE SYSTEM WILL/SHOULD KEEP ANY SNOW IMPACT WEST OF THE TAF
SITES. LOCALLY...MOSTLY MID/HIGH LEVEL VFR CLOUDS TO DEAL WITH THIS
AFTERNOON/EVENING. WINDS WILL REMAIN RELATIVELY LIGHT FROM THE NORTH
INTO THU MORNING...BECOMING MORE WEST/SOUTHWEST THU AFTERNOON/NIGHT
AS WEAK HIGH PRESSURE MOVES OVERHEAD.

&&

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

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION.....RIECK


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