Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 301800
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1200 PM CST FRI JAN 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CST FRI JAN 30 2015

CHALLENGES INCLUDE SNOW CHANCES/AMOUNTS AND LOCATION SATURDAY
EVENING THROUGH SUNDAY. 30.00Z MODEL SUITE...INCLUDING THE
GFS/NAM/ECMWF/GEM HAVE SHIFTED TO THE NORTH WITH PRIMARY SNOW
BAND...INCREASING THE LIKELIHOOD OF ACCUMULATING SNOWFALL MAINLY
ALONG AND SOUTH OF THE I-90 CORRIDOR. WILL USE A BLENDED MODEL
SOLUTION WITH A SLIGHT PREFERENCE FOR GFS/ECMWF GIVEN THE MOST
SIMILARITIES.

FOR TODAY...SURFACE HIGH PRESSURE IN THE WAKE OF YESTERDAY/S COLD
FRONTAL PASSAGE WILL RESULT IN DRY CONDITIONS WITH A MIX OF SUN
AND CLOUDS. TEMPERATURES...HOWEVER...WILL BE NOTICEABLY COOLER
WITH AFTERNOON HIGHS FROM THE UPPER TEENS ACROSS NORTH-CENTRAL WI
TO THE UPPER 20S ACROSS PORTIONS ACROSS NORTHEAST IA. WARM AIR
ADVECTION OVERNIGHT ALONG INCREASING SOUTHERLY WIND WILL ALLOW
TEMPERATURES TO FALL SLOWLY OR REMAIN STEADY WITH SATURDAY MORNING
LOWS GENERALLY IN THE MID TEENS TO MID 20S.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 340 AM CST FRI JAN 30 2015

ANOTHER COLD FRONT WILL DROP SOUTH ON SATURDAY...BUT NOT BEFORE
TEMPERATURES RISE INTO THE MID 20S TO LOWER 30S IN THE PRECEDING
WARM SECTOR. CLOUD COVER WILL INCREASE THROUGH THE DAY...ALTHOUGH
EXPECT MOSTLY DRY CONDITIONS.

ATTENTION TURNS TO SATURDAY EVENING THROUGH SUNDAY WHEN AN 850 HPA
LOW EJECTS FROM A FOUR CORNERS TROUGH AND INTERACTS WITH A
NORTHERN STREAM WAVE DROPPING SOUTH FROM WESTERN CANADA. THIS
SETS-UP A MODEST AREA OF LOW-LEVEL FRONTOGENESIS FROM NORTHERN
IOWA INTO SOUTHEAST MN AND SOUTHWEST WI. INCREASED MOISTURE
WRAPPING AROUND THE 850 HPA LOW WITH PWATS FROM 0.4 TO 0.5 INCHES
ACTING ON THIS FORCING AND BEING FURTHER SUPPORTED BY THE RIGHT
ENTRANCE REGION OF A 300 HPA JET STREAK...WILL RESULT IN AN AREA
OF LIGHT SNOW MAINLY ALONG AND SOUTH OF THE I-90 CORRIDOR.

THIS IS A DEPARTURE FROM PREVIOUS FORECASTS WITH THE LAST THREE
RUNS OF THE GFS/ECMWF TRENDING FARTHER NORTH WITH ACCUMULATING
SNOWFALL. THIS TREND MAY CONTINUE AND WITH GFS/NAM SOUNDINGS
SUPPORTING A DEEP (SFC TO 650 HPA) SATURATED DENDRITIC GROWTH
ZONE...SNOW AMOUNTS MAY NEED TO BE INCREASED FURTHER. FOR
NOW...LOOK FOR 1 TO 2 INCHES ALONG AND SOUTH OF I-90 WITH UPWARDS
OF 3 TO 4 INCHES ACROSS THE SOUTHERNMOST PORTIONS OF FAYETTE/
CLAYTON/GRANT COUNTIES. ADJUSTED GRIDS ACCORDINGLY WITH LIKELY
POPS EXTENDING MUCH FURTHER NORTH THAN PREVIOUS FORECASTS. SUNDAY
WILL BE MUCH COLDER UNDER THE INFLUENCE OF LOW-LEVEL COLD AIR
ADVECTION WITH HIGHS ONLY IN THE TEENS.

TEMPERATURES TO BOTTOM OUT MONDAY MORNING WITH SURFACE RIDGE AXIS
JUST WEST OF THE FORECAST AREA LEADING TO CLEARING SKIES AND LIGHT
WINDS. WITH FRESH SNOW OVER MUCH OF THE AREA...MORNING LOWS WILL
FALL BELOW ZERO IS MOST LOCATIONS.

FOR THE REST OF THE WORK WEEK...NORTHWEST FLOW ALOFT WILL
CONTINUE WITH WEAK SHORT-WAVES BRINING ADDITIONAL LIGHT SNOW
CHANCES MONDAY NIGHT THROUGH MUCH OF TUESDAY. WEDNESDAY/THURSDAY
FOR THE MOST PART LOOK DRY. HIGHS TUESDAY WILL REBOUND SLIGHTLY
INTO THE LOWER TO MID 20S BEFORE DROPPING BACK INTO THE MID TEENS
FOR THE LATTER HALF OF THE WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1200 PM CST FRI JAN 30 2015

EXPECT VFR CONDITIONS TO REMAIN IN PLACE OVER THE TAF SITES
THROUGH MUCH OF TONIGHT...DUE TO PLENTIFUL LOW LEVEL DRY AIR.
HOWEVER...SOME MOISTURE INCREASE WILL OCCUR LATE TONIGHT IN
SOUTHEAST MINNESOTA AS SOUTHERLY WINDS INCREASE...WHICH COULD
DEVELOP INTO MVFR BR. A COLD FRONT IS POISED TO MOVE THROUGH THE
TAF SITES SATURDAY MORNING. BESIDES WINDS TURNING NORTHWEST BEHIND
THE FRONT...THERE IS POTENTIAL FOR LOWER STRATUS TO FOLLOW. A LOT
OF MODEL SPREAD EXISTS ON THIS POTENTIAL...MORESO AT LSE VERSUS
RST. THEREFORE...HAVE ONLY INCLUDED BKN MVFR CEILINGS AT RST AT
THIS TIME.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...AJ



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