Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 211020
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
420 AM CST FRI NOV 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 353 AM CST FRI NOV 21 2014

CHALLENGES INCLUDE FREEZING PRECIP TONIGHT AND OVERALL EVOLUTION OF
PRECIP TYPE AND AMOUNTS THROUGH MONDAY AS A STRONG EASTERN PACIFIC
WAVE MOVES ACROSS THE UPPER MIDWEST. 21.00Z ECMWF/GFS/NAM IN GOOD
OVERALL AGREEMENT AND WILL USE A BLENDED SOLUTION.

FLOW ALOFT BECOMES MORE ZONAL TODAY ALLOWING FOR WARM AIR ADVECTION
REGIME TO OVERSPREAD THE FORECAST AREA. CLEAR SKIES THIS MORNING
WILL GIVE WAY TO INCREASING CLOUD COVER THROUGH THE AFTERNOON. WITH
WARMER AIR ALOFT...TEMPERATURES WILL RISE INTO THE MID TO UPPER 20S
AND PERHAPS EVEN A FEW SPOTS WILL REACH 30 DEGREES. WINDS WILL BE
BREEZY TODAY FROM THE SOUTH WITH OCCASIONAL GUSTS TO 25 MPH ACROSS
SOUTHEAST MN AND NORTHEAST IA.

ATTENTION THEN TURNS TO THIS EVENING AND OVERNIGHT AS 0-2 KM
MOISTURE SURGES NORTHWARD ALONG 30 TO 40 KT 850 HPA JET. WITH VERY
DRY AIR ALOFT...THERE WILL BE NO ICE INTRODUCED INTO THE CLOUD. LOW-
LEVEL WARM AIR ADVECTION AND ISENTROPIC LIFT ON THE 275 K SURFACE
RESULTS IN OMEGA VALUES AROUND 3 UBAR/S IN THIS SUPERCOOLED
SATURATED LAYER...PRODUCING PERIODS OF DRIZZLE. ALTHOUGH SURFACE
TEMPERATURES WILL BE WARMING TO ABOVE FREEZING OVERNIGHT...ROAD
SURFACES WILL REMAIN BELOW 32 DEGREES AND EXPECT SLICK CONDITIONS
TO DEVELOP WITH A GLAZE OF ICE. CONFIDENCE HIGHEST ACROSS NORTHEAST
IA INTO SOUTHWEST WI AND WILL ISSUE A FREEZING RAIN ADVISORY FOR
THESE AREAS FROM 22.05Z TO 22.14Z.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 353 AM CST FRI NOV 21 2014

DRIZZLE DIMINISHES FROM WEST TO EAST ON SATURDAY AS PRIMARY LOW-
LEVEL MOISTURE PLUME SHIFTS TO THE EAST. TEMPERATURES WILL RISE
INTO THE UPPER 30S TO LOWER 40S WITH LIGHT SOUTHWEST WIND. RAIN
CHANCES INCREASE AGAIN SATURDAY NIGHT FROM SOUTH TO NORTH AS
ATMOSPHERIC COLUMN CONTINUES TO WARM AND SATURATES UP TO 700 HPA.

SUNDAY WILL BE WARM AND WET AS PRIMARY SURFACE LOW LIFTS FROM THE
SOUTHERN PLAINS TO THE SOUTHERN TIP OF LAKE MICHIGAN BY 24.06Z.
PRECIP TYPE WILL BE ALL RAIN WITH A FULLY SATURATED COLUMN AND
A THERMAL PROFILE ABOVE FREEZING TO 750 HPA. AFTERNOON HIGHS WILL
SOAR INTO THE MID 40S. PRECIP WILL GRADUALLY CHANGE OVER TO ALL
SNOW SUNDAY NIGHT INTO MONDAY MORNING AFTER MID-LEVEL COLD FRONT
SWEEPS ACROSS THE REGION. ACCUMULATING SNOWFALL IS POSSIBLE
THROUGH THE DAY ON MONDAY IN WRAP-AROUND DEFORMATION ZONE...BUT
AMOUNTS LOOK TO BE ONLY A FEW INCHES AT MOST.

SNOW WILL DIMINISH FROM WEST TO EAST ON TUESDAY...BUT WITH A
RETURN TO A FREEZING AIR MASS. DAY TO DAY TEMPERATURES WILL SLOWLY
FALL THROUGH THE REMAINDER OF THE WEEK WITH HIGHS ON THURSDAY BACK
INTO THE TEENS TO LOWER 20S AND LOWS IN THE LOWER TO MID TEENS.
THE NEXT BEST CHANCE FOR SNOW WILL BE WEDNESDAY AND WEDNESDAY
NIGHT AS THE NEXT SHORT-WAVE DROPS SOUTH FROM CANADA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1115 PM CST THU NOV 20 2014

HIGH PRESSURE WILL INFLUENCE THE REGION TONIGHT...KEEPING SKIES
CLEAR AND FAVORING LIGHT WINDS.

THE HIGH WILL SLIP QUICKLY SOUTHEAST ON FRIDAY...WITH A TIGHTENING
PRESSURE GRADIENT AHEAD OF AN APPROACHING SHORTWAVE TROUGH. WINDS
WILL BECOME SOUTHERLY AND INCREASE EARLY FRIDAY MORNING.

HIGH/MID LEVEL CLOUDS WILL MOVE IN FROM WEST TO EAST ON
FRIDAY...THICKENING AND LOWERING FRIDAY NIGHT. BUFKIT SOUNDINGS ARE
FAVORING A LOW SATURATION FRIDAY NIGHT - ESPECIALLY OVERNIGHT INTO
SATURDAY. THIS STRATUS DECK WOULD INTERACT WITH LOW LEVEL WARM AIR
ADVECTION AND ADDITIONAL LIFT...WHICH COULD RESULT IN AREAS OF
DRIZZLE. SOME QUESTION THOUGH ON IF THERE WILL BE ENOUGH LIFT IN THE
SATURATED LAYER...OR IF MOST OF IT WOULD BE ABOVE IT. WITH TEMPS AND
ROADS SFCS BELOW ZERO...FREEZING DRIZZLE WOULD BE THE PCPN TYPE IF
IT OCCURS. TEMPS QUICKLY WARM SAT MORNING...AND THEN SHOULD STAY
WARM ENOUGH THROUGH THE WEEKEND FOR ANY ADDITIONAL PCPN TO FALL AS
RAIN.

IN ADDITION TO THE LOW CLOUDS AND POTENTIAL FOR DRIZZLE...THE
INCREASE IN THE LOW SATURATION AND MILDER AIR COULD TRANSLATE INTO
AREAS OF FOG. ALREADY ANTICIPATING IFR/MVFR CIGS AND VSBYS FROM THE
CLOUDS/PCPN...BUT THE FOG COULD FURTHER HINDER VISIBILITIES.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY FROM 11 PM THIS EVENING TO 8 AM CST
     SATURDAY FOR WIZ054-055-061.

MN...NONE.
IA...FREEZING RAIN ADVISORY FROM 11 PM THIS EVENING TO 8 AM CST
     SATURDAY FOR IAZ008>011-018-019-029-030.

&&

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION.....RIECK



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