699
FXUS63 KARX 230538
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1139 PM CST TUE JAN 22 2019
UPDATE
ISSUED AT 845 PM CST TUE JAN 22 2019
BASED ON TRACK OF SOUTHERN SHORT WAVE AND ASSOCIATED LIFT, LOOKS
LIKE PATCHY BAND OF SNOW WILL PERSIST TONIGHT ACROSS PARTS OF
EASTERN IOWA INTO SOUTHWEST WISCONSIN WITH MODEST ACCUMULATIONS
STILL POSSIBLE.
ALLOWING FOR SOME BUFFER IF SNOW BAND WAVERS A BIT, WILL TRIM BACK
NORTH AND WEST EDGE OF ADVISORY A TIER OF COUNTIES TONIGHT AS TROUGH
AXIS PASSES. SHORT TERM GUIDANCE IN AGREEMENT THAT PRECIPITATION
SHOULD REMAIN SOUTH AND EAST OF THESE AREAS, AND OUTSIDE OF SOME
SNOW LEFT ON ROADS, NOT EXPECTING ANY ADDITIONAL IMPACT MOVING
THROUGH THE OVERNIGHT.
SHORT TERM
(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 239 PM CST TUE JAN 22 2019
WATER VAPOR SATELLITE THIS AFTERNOON CONTINUES TO SHOW THAT THE
NORTHERN AND SOUTHERN STREAM SHORT WAVE TROUGHS HAVE NOT PHASED.
USING THE LAST SEVERAL RUNS OF THE RAP, APPEARS THERE IS LITTLE
CHANCE OF THIS HAPPENING NOW. BECAUSE OF THIS LACK OF PHASING, THE
SOUTHERN STREAM SYSTEM HAS BEEN PUSHED FARTHER TO THE SOUTHEAST THAN
PREVIOUSLY EXPECTED. THIS SOUTHEAST PUSH IS NOW TAKING THE BEST PV
ADVECTION IN THE 500-300 MB LAYER FROM KANSAS INTO SOUTHEAST
WISCONSIN SO THAT IT JUST BRUSHES THE SOUTHERN SECTIONS OF THE
FORECAST AREA. IN THE MID-LEVELS, A BAND OF FRONTOGENESIS IN
ASSOCIATION WITH THE NORTHERN STREAM WAVE HAS FORMED A BAND OF
MODERATE SNOW FROM SOUTHEAST MINNESOTA INTO WESTERN/CENTRAL
WISCONSIN. THIS LOOKS TO CONTINUE MOVING EAST AND THEN WEAKEN DURING
THE LATE AFTERNOON AS THE FRONTOGENESIS BECOMES FOCUSED FARTHER TO
THE SOUTH WITH THE SOUTHERN STREAM SHORT WAVE TROUGH. THIS WILL
FOCUS THE THREAT FOR THE HEAVIER SNOW FROM EASTERN IOWA INTO
SOUTHERN WISCONSIN FOR THE OVERNIGHT HOURS. AFTER THE EARLIER
ADJUSTMENTS TO THE SNOW AMOUNTS, WILL CONTINUE WITH THE IDEA THAT
THE FRONTOGENESIS AND HEAVIER SNOW BAND COULD BE CLOSE ENOUGH TO
GENERATE TOTAL ACCUMULATIONS OF 4 TO 6 INCHES FROM ALLAMAKEE AND
CLAYTON COUNTIES NORTHEAST INTO CENTRAL WISCONSIN. HOWEVER, IF THE
SHORT RANGE MODEL TRENDS CONTINUE TO SHOW A MORE SOUTHEAST PLACEMENT
OF THE SNOW BAND, FURTHER ADJUSTMENTS TO THE HEADLINES WILL BE
NEEDED.
LONG TERM
(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 239 PM CST TUE JAN 22 2019
ON WEDNESDAY NIGHT, ANOTHER ARCTIC COLD FRONT WILL MOVE QUICKLY
SOUTHEAST THROUGH THE REGION. WARM AIR ADVECTION AHEAD OF THIS
FRONT WILL CAUSE TEMPERATURES TO WARM INTO THE TEENS AND LOWER
20S. IN THE WAKE OF THIS FRONT, STRONG COLD AIR ADVECTION WILL
CAUSE FALLING TEMPERATURES THROUGHOUT THURSDAY. BY MID-AFTERNOON
TEMPERATURES WILL BE IN THE SINGLE DIGITS ABOVE AND BELOW ZERO. A
WIND CHILL ADVISORY WILL BE LIKELY NEEDED FOR THURSDAY AFTERNOON
IN SOUTHEAST MINNESOTA AND NORTHEAST IOWA.
FROM THURSDAY NIGHT THROUGH SATURDAY, THE ARCTIC AIR WILL REMAIN
ACROSS THE REGION. 850 MB STANDARDIZED TEMPERATURE ANOMALIES RANGE
FROM -1.5 TO -2.5. THE LARGEST TEMPERATURE ANOMALIES WILL BE ON
FRIDAY MORNING. LOW TEMPERATURES ON BOTH FRIDAY AND SATURDAY
MORNINGS WILL LIKELY RANGE FROM -10 TO -25F. THERE MAY BE EVEN
SOME COLDER TEMPERATURES IN CENTRAL WISCONSIN. WIND CHILLS WILL
LIKELY RANGE FROM 25 TO 35 BELOW. A WIND CHILL ADVISORY WILL
LIKELY BE NEEDED.
ON FRIDAY, A NORTHERN STREAM SHORT WAVE TROUGH MAY BE CLOSE ENOUGH
TO POTENTIALLY PRODUCE UP TO A HALF INCH OF SNOW ACROSS PARTS OF
NORTHEAST IOWA AND SOUTHWEST WISCONSIN. HOWEVER, CONFIDENCE IS
LOW. BOTH THE GFS AND NAM KEEPS THIS SNOW WELL TO OUR WEST AND
SOUTH. MEANWHILE, THE ECMWF HAS LIGHT SNOW SOUTH OF INTERSTATE 90.
FOR NOW JUST STAYED WITH 20 PERCENT SNOW CHANCES.
ON SATURDAY NIGHT, ANOTHER ARCTIC COLD FRONT WILL MOVE SOUTHEAST
THROUGH THE AREA. THIS SYSTEM MAY PRODUCE UP TO 1 INCH OF SNOW.
FROM SUNDAY NIGHT INTO MONDAY, A MUCH STRONGER NORTHERN STREAM
SHORTWAVE TROUGH WILL MOVE THROUGH THE REGION. UNLIKE THE PREVIOUS
2 SYSTEMS, ACTUALLY THIS ONE HAS MORE MOISTURE TO WORK WITH. THE
GEFS LSE PLUMES RANGING FROM 0.05 TO A HALF INCH. DEPENDING ON ITS
TRACK, THERE COULD BE SOME TRAVEL IMPACTS.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1139 PM CST TUE JAN 22 2019
GENERAL IMPROVEMENT HAS BEEN NOTED THROUGH THE EVENING AS LOWER
CEILINGS AND VISIBILITIES STARTING TO SHIFT SOUTHEAST WITH MAIN
SHORT WAVE AND ASSOCIATED WINTER PRECIPITATION. WHILE SOME IFR STILL
BEING OBSERVED SOUTH, CONDITIONS HAVE LIFTED TO MAINLY MVFR FOR THE
TIME BEING.
THIS TREND WILL CONTINUE OVERNIGHT IT APPEARS, BUT SATELLITE AND
METARS SHOW BANDS OF LOWER CLOUDS MIXED WITH VFR THAT WILL MAKE TAF
FORECASTING A BIT TRICKY.
AS WAVE EXITS THE AREA, GENERALLY IMPROVING CONDITIONS EXPECTED WITH
SHORT TERM RIDGE BUILDING IN LATER WEDNESDAY. VFR CONDITIONS SHOULD
BE MORE WIDESPREAD AS WINDS BACK.
ARX WATCHES/WARNINGS/ADVISORIES
WI...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR WIZ041>044-
053.
WINTER STORM WARNING UNTIL 9 AM CST WEDNESDAY FOR WIZ054-055-061.
MN...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR MNZ096.
IA...WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR IAZ010-011-
019-029.
WINTER STORM WARNING UNTIL 9 AM CST WEDNESDAY FOR IAZ030.
UPDATE...SHEA
SHORT TERM...04
LONG TERM...BOYNE
AVIATION...SHEA
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