000
FXUS63 KARX 260920
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
320 AM CST MON JAN 26 2015

.SHORT TERM...(TODAY AND TONIGHT))
ISSUED AT 320 AM CST MON JAN 26 2015

MAIN FCST CONCERNS THIS PERIOD...QUICK HITTING SYSTEM WITH SNOW/
-FZDZ MAINLY THIS MORNING...TEMPERATURES.

06Z DATA ANALYSIS HAD A 999MB LOW OVER LK WINNIPEG WITH THE
STRONGEST PRESSURE FALLS OF 5-6MB/3 HRS OVER NORTHWEST MN. VIGOROUS
SHORTWAVE OF CONCERN FOR TODAY COULD BE SEEN IN WV IMAGERY HEADED
INTO NORTHWEST MN. AREA RADARS SHOWING INCREASING RETURNS OVER
CENTRAL INTO NORTHEAST MN...WITH PRECIP /-SN/ SO FAR MAINLY
LIMITED TO NORTHEAST MN AS INITIAL FORCING/LIFT WORKS TO SATURATE
THE COLUMN FURTHER WEST/SOUTH ACROSS MN AHEAD OF THE SHORTWAVE.
STRONG TEMPERATURE CONTRAST ACROSS THE REGION EARLY THIS
MORNING...FROM NEAR ZERO IN NORTHEAST WI TO NEAR 30 ACROSS WESTERN
IA/SOUTHWEST MN...WHICH WILL PLAY INTO THE FCST FOR TODAY.

26.00Z MODELS ALL INITIALIZED QUITE WELL. SOLUTIONS...INCLUDING
VARIOUS HI-RES WRF MODELS VERY SIMILAR AS A RATHER VIGOROUS
SHORTWAVE AND ROUND OF DEEPER FORCING/LIFT DROPS SOUTH-SOUTHEAST
ACROSS THE UPPER MIDWEST TODAY...MAINLY THIS MORNING. TREND FAVORS
STRONGER OF THE EARLIER MODEL RUNS WITH THIS FEATURE...RESULTING IN
MORE IMPACT TO THE FCST AREA AS IT PASSES. GOOD CONSENSUS FOR HGTS
TO QUICKLY START RISING TONIGHT. SHORT TERM FCST CONFIDENCE IS GOOD
THIS CYCLE.

IN THE SHORT TERM...RATHER IMPRESSIVE SFC-700MB THERMAL GRADIENT
OVER THE AREA TODAY...FOR THE SOUTHEAST MOVING SHORTWAVE AND LOWER
LEVEL THERMO-DYNAMIC FORCING TO WORK WITH. CONSISTENT SIGNAL AMONG
MODELS FOR STRONG/DEEP LAYERED FORCING/LIFT...FROM DIVERGENCE IN
LEFT EXIT REGION OF A 150KT JET MAX TO PV ADVECTION AHEAD OF THE
SHORTWAVE AND 925-700MB WARM ADVECTION...TO SPREAD SOUTH-SOUTHEAST
ACROSS THE AREA THIS MORNING. ISENTROPIC LIFT SEEN IN THE 275K-315K
LAYER...ROUGHLY THE 925-400MB PORTION OF THE COLUMN. STRONGEST/
DEEPEST OF THE FORCING  PASSES IN THE 09Z-15Z TIME-FRAME...WITH THE
FIRST HALF OF IT WORKING TO SATURATE THE INITIALLY DRY 925-500MB
PORTION OF THE COLUMN OVER THE FCST AREA. ONCE THIS OCCURS...WITH PW
VALUES OF 0.4 TO 0.5 INCH IN THE INFLOW AIR...APPEARS A RATHER
VIGOROUS BAND OF PRECIP TO SPREAD SOUTHEAST ACROSS MAINLY THE
CENTRAL/EAST PORTIONS OF THE FCST AREA WHERE THE COLUMN WILL BE A
BIT COOLER AND LIFT STRONGER EAST OF THE SHORTWAVE TRACK. OTHER
SIGNAL AMONG THE STRONGER MODEL CONSENSUS IS DEEPER SATURATION OF
THE COLUMN...AT LEAST THRU MID MORNING BEFORE THE SHORTWAVE PASSES
AND MID LEVEL DRYING SPREADS SOUTHEAST INTO THE FCST AREA. APPEARS
A SNOW-BURST TYPE BAND OF PRECIP TO MOVE ACROSS THE AREA MAINLY IN
THE 12Z-16Z PERIOD...PRODUCING A QUICK 1 TO 2 INCHES OF SNOW EAST
OF THE MS RIVER...LESSER AMOUNTS ALONG/WEST OF THE MS RIVER...MUCH
OF THIS DURING THE MORNING COMMUTE TIME. ONCE THE MID LEVEL DRYING
SPREADS IN...ICE IS LOST IN THE CLOUDS. WITH THE CONTINUED WARM
ADVECTION/ LIFT IN THE 925-850MB SATURATED PORTION OF THE COLUMN
WELL INTO THE AFTERNOON...STRONG SIGNAL FOR -DZ/-FZDZ ACROSS THE
CENTRAL EAST/ PARTS OF THE FCST AREA...AND CONTINUED PRECIP
CHANCES EAST OF THE MS RIVER THRU MUCH OF THE AFTERNOON. EVENING
CREW ALREADY ISSUED A WINTER WEATHER ADVISORY FOR CENTRAL/NORTH
PARTS OF THE FCST AREA AND CONSIDERING EXPANDING THIS INTO AT
LEAST THE REST OF THE WI COUNTIES IN THE FCST AREA. MAY HAVE TO
WAIT UNTIL EVENT UNFOLDS A BIT MORE TO ADJUST/ EXPAND THE ADVISORY
IF NEEDED.

ONE CONCERN IS HOW FAR EAST THE WARM FRONT GETS TODAY AND RESULTING
HIGH TEMPS ACROSS THE FCST AREA. SOME SOLUTIONS STALL IT NEAR THE MS
RIVER...OTHER TAKE IT AS FAR EAST AS I-94 BEFORE THE WAVE PASSES.
WILL STAY THE COURSE WITH THE BOUNDARY MOVING TO JUST EAST OF THE MS
RIVER THIS AFTERNOON AND TEMPS ALONG/WEST I-94 WARMING ABOVE
FREEZING AND LIMITING -FZDZ POTENTIAL THRU MUCH OF THE AFTERNOON
HOURS ACROSS ALL BUT THE NORTHEAST END OF THE FCST AREA. LOW LEVEL
COLD ADVECTION AND WEAK RIDGE OF HIGH PRESSURE QUICKLY BUILD IN
TONIGHT...HOWEVER LOWER CLOUDS LOOKING TO LINGER ACROSS MUCH OF THE
FCST AREA AS 925-850MB MOISTURE GETS TRAPPED UNDER AN INVERSION...
LIMITING HOW FAR TEMPS MAY DROP TONIGHT. OVERALL USED A BLEND OF THE
GUIDANCE HIGHS/LOWS FOR TODAY/TONIGHT.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 320 AM CST MON JAN 26 2015

MAIN FCST CONCERNS FOR TUE THRU WED NIGHT...NEXT WAVE THRU THE FLOW
AND -SN/-RA CHANCES WED NIGHT...TEMPERATURES THRU THE PERIOD.

26.00Z MODELS REMAIN IN DECENT AGREEMENT FOR TUE INTO WED WITH
RISING HGTS/SHORTWAVE RIDGING BUILDING ACROSS THE UPPER MIDWEST.
TIGHTENING SIGNAL FOR A PAC ENERGY TOPPING THE WESTERN NOAM RIDGE TO
AT LEAST PARTLY PHASE WITH REMNANTS OF THE CA BAJA ENERGY AND MOVE
INTO THE MID/UPPER MS VALLEY WED NIGHT. HOWEVER PLENTY OF DETAIL
DIFFERENCES WITH THIS AND LOWER LEVEL FEATURES BY WED NIGHT. FCST
CONFIDENCE IS GOOD TUE THRU WED THEN AVERAGE WED NIGHT.

THE HIGH PRESSURE RIDGE FROM MON NIGHT REMAINS NEAR/OVER THE EASTERN
SIDE OF THE REGION TUE/TUE NIGHT AS THE NEXT LOW DEVELOPS IN THE
CENTRAL/NORTHERN PLAINS. LOW LEVEL WARM ADVECTION RETURNS FOR
TUE/TUE NIGHT AS SOUTH/SOUTHWEST SFC-700MB GRADIENT FLOW
INCREASES ACROSS THE AREA. SIGNAL FOR THIS FLOW TO ADVECT THE
LOWER LEVEL MOISTURE NORTH/EAST OF THE FCST AREA AND WILL REMAIN
OPTIMISTIC FOR PARTLY CLOUDY SKIES ACROSS MUCH OF THE FCST AREA
FOR TUE/TUE NIGHT. THE LOWER LEVEL WARM ADVECTION CONTINUES INTO
WED...WITH TUE THRU WED TEMPS LOOKING TO REMAIN SOME 10F TO 15F
ABOVE NORMAL. GIVEN SOME UNCERTAINTIES WITH THE LOWER LEVEL
MOISTURE/CLOUDS...WHICH ALL THE MODELS STRUGGLE WITH...USED THE
MODEL/ENSEMBLE CONSENSUS FOR HIGHS/ LOWS TUE THRU WED. SFC THRU
MID LEVEL TROUGH AXIS TO MOVE ACROSS THE REGION WED NIGHT. DETAIL
DIFFERENCES WITH TIMING/TRACKS OF THE NORTHERN/SOUTHERN STREAM
SHORTWAVES...LOWER LEVEL THERMO-DYNAMIC FIELDS AND FORCING AND
AMOUNT OF MOISTURE BROUGHT NORTHWARD INTO THE SYSTEM ALL PLAY INTO
PRECIP POTENTIAL ACROSS THE REGION WED NIGHT. FOR NOW...A 30-40
PERCENT -SN/-RA CHANCE WED NIGHT LOOKS GOOD UNTIL THE DETAILS SORT
THEMSELVES OUT. USED A BLEND OF THE GUIDANCE LOWS FOR WED NIGHT.

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

MAIN FCST CONCERNS THIS PERIOD...TEMPERATURES AND POTENTIAL SNOW
CHANCES THRU THE PERIOD.

MEDIUM RANGE MODEL RUNS OF 26.00Z IN GENERALLY GOOD AGREEMENT FOR
TROUGHING TO BE MOVING EAST OF THE REGION THU...WITH NORTHWEST FLOW
AND SLOWLY RISING HGTS/WEAK SHORTWAVE RIDGING OVER THE UPPER MIDWEST
FRI. DIFFERENCES IMPACTING THE SENSIBLE WEATHER ARE PRESENT AMONG
THE MODELS FOR SAT/SUN. RUN-TO-RUN CONSISTENCY TAKES A HIT BY
SAT/SUN AS WELL. GFS OFFERS A CONTINUED ACTIVE NORTHWEST FLOW
PATTERN WHILE ECMWF DROPS A CHUNK OF ARCTIC AIR/HIGH PRESSURE INTO
THE UPPER MIDWEST FOR THE WEEKEND. FCST CONFIDENCE AVERAGE FOR
THU/FRI THEN BELOW AVERAGE FOR THE WEEKEND.

POTENTIAL FOR SOME WEAK SFC-700MB TROUGHING AND PV ADVECTION WITH
THE NORTHERN STREAM SHORTWAVE FROM THE WED NIGHT TROUGHING TO LINGER
OVER THE REGION THU. SMALL -SN CHANCE REASONABLE AT THIS POINT.
BETTER SIGNAL FOR CANADIAN HIGH PRESSURE TO DRIFT ACROSS THE UPPER
MIDWEST FRI...UNDER THE WEAK SHORTWAVE RIDGING ALOFT. LOOSE
CONSISTENCY SIGNAL FOR SFC-700MB TROUGHING TO MOVE ACROSS THE REGION
SAT...HOWEVER PLENTY OF LOCATION/STRENGTH DIFFERENCES CONCERNING
A SFC WAVE/LOW...ECMWF MUCH WEAKER/FURTHER NORTH THAN GFS WHICH
TRACKS A SFC LOW ACROSS SOUTHERN MN/IA. SMALL -SN CHANCE SAT OKAY
FOR NOW. BY SUN...ECMWF HAS LOW LEVEL COLD ADVECTION OVER THE
REGION WITH 925MB TEMPS IN THE -18C TO -23C RANGE ACROSS THE FCST
AREA. GFS HAS INCREASING LOW LEVEL WARM ADVECTION SUNDAY...WITH
925MB TEMPS ABOUT 10C WARMER THAN THOSE OF THE ECMWF BY 02.00Z.
GIVEN AVERAGE TO BELOW CONFIDENCE AND NO ONE MODEL A BETTER
PERFORMER IN THE DAY 4-7 PERIOD THIS WINTER...STAYED WITH THE
MODEL/ENSEMBLE CONSENSUS HIGHS/LOWS FOR THU THRU SUN.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1135 PM CST SUN JAN 25 2015

MVFR STRATUS REMAINS OVER RST AND WAS EXPANDING QUICKLY TOWARDS
LSE LATE THIS EVENING DUE TO SOUTHWEST WINDS PICKING UP. LSE
SHOULD GO MVFR BY 07Z. ATTENTION THEN TURNS TO A LOW PRESSURE
SYSTEM DROPPING SOUTHEAST THROUGH MN. THIS SYSTEM WILL BRING SNOW
INTO THE TAF SITES AROUND 11Z...ALONG WITH A DROP OF VISIBILITIES
AND CEILINGS TO IFR. RST COULD EVEN GO LIFR IN CEILINGS. TOWARDS
13Z AT RST AND 16Z AT LSE...THE ICE IN THE CLOUDS IS EXPECTED TO
BE LOST...CAUSING THE SNOW TO CHANGE TO FREEZING DRIZZLE.
SWITCHING THE PRECIPITATION TYPE WILL HELP TO IMPROVE VISIBILITY
TO MVFR. HOWEVER...LITTLE CHANGE IS EXPECTED TO CEILING.
PRECIPITATION SHOULD END BY NOON AT RST AS A WARM FRONT MOVES
IN...BUT WINDS WILL INCREASE FROM THE WEST AND EVENTUALLY
NORTHWEST LATE IN THE DAY WITH A COLD FRONTAL PASSAGE. LSE IS
TRICKY WIND WISE WITH BOTH FRONTS FORECAST TO LAY UP RIGHT NEAR
THE TAF SITE FOR THE AFTERNOON AND EVENING. NEVERTHELESS...BOTH
SITES EXPECTED TO SEE CEILINGS INCREASE TO MVFR LATE IN THE DAY
INTO THE EVENING AS MIXING INCREASES.

LOOKING AT TOTAL SNOWFALL AMOUNTS LESS THAN 1 INCH...WHILE A
LIGHT GLAZING OF ICE COULD OCCUR...ESPECIALLY AT LSE.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR WIZ017-029-
     032>034-041-042-053.

MN...WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR MNZ079-088-096.

IA...NONE.
&&

$$

SHORT TERM...RRS
LONG TERM....RRS
AVIATION.....AJ