283
FXUS63 KARX 191746
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1146 AM CST TUE NOV 19 2024
KEY MESSAGES
- PRECIPITATION ENDING TODAY WITH STEADY TO FALLING
TEMPERATURES AND INCREASING WEST WINDS:
- SCATTERED SNOW SHOWERS OVERSPREADING THE AREA WEDNESDAY WITH
REINFORCING COLD AIR (30-100% HREF PROBABILITIES FOR
MEASURABLE SNOW, BUT LOW PROBABILITIES FOR 1"). FALLING SNOW
AND BRISK WINDS COULD REDUCE VISIBILITIES
- SEASONABLE TEMPERATURES WEDNESDAY INTO EARLY NEXT WEEK WITH
HIGHS IN THE 30S/40S.
DISCUSSION
ISSUED AT 330 AM CST TUE NOV 19 2024
OVERVIEW:
STRONG SURFACE LOW PRESSURE WAS LOCATED OVER SOUTHWEST MINNESOTA AT
07Z WITH THE MAIN PRECIPITATION SHIELD EXTENDING FROM NORTHEAST
WISCONSIN THROUGH NORTHERN MINNESOTA AND INTO EASTERN SOUTH DAKOTA.
DUE TO THE STRONG ISALLOBARIC GRADIENT, WINDS HAVE BEEN GUSTING 25
TO 45 MPH. FOR A TIME MONDAY EVENING AT DBQ, WINDS WERE GUSTING
AROUND 50 MPH BETWEEN 930 AND MIDNIGHT. A LOOK AT THE TEMPERATURE
TRACE SHOWS TEMPERATURES HAVE BEEN RISING ALL EVENING INTO THE EARLY
MORNING HOURS WITH AREA TEMPERATURES EARLY THIS MORNING WERE IN THE
50S TO LOWER 60S, SOME 15 TO 20 DEGREES ABOVE THE NORMAL HIGH! AT
07Z, THE TRIPLE POINT WAS NEAR MKT AND THE FRONT HAD JUST LIFTED
NORTH OF RST WITH WINDS SWITCHING FROM THE EAST TO THE
SOUTHWEST. RAINFALL HERE AT THE NWS THROUGH MIDNIGHT WAS 0.67",
AT LSE 0.81", AND AT RST 0.98"; A NEW DAILY RECORD (OLD RECORD
1957).
WATER VAPOR SATELLITE IMAGERY, HEIGHTS, AND LIGHTNING SHOWED THE
NEGATIVELY TILTED TROUGH OVER SOUTHERN MINNESOTA WITH TROUGHING
EXTENDING WESTWARD INTO MONTANA AND BRITISH COLUMBIA. THE TROPICAL
FETCH OF MOISTURE CONTINUED TO FEED THE STRONG STORM SYSTEM WITH
CONVECTION NOTED FROM THE GULF OF MEXICO THROUGH THE MISSISSIPPI
VALLEY TOWARD ILLINOIS. WE DID HAVE SOME CONVECTION EARLIER ACROSS
SOUTHERN WISCONSIN MONDAY EVENING. BROAD MID/HIGH LEVEL DRYING WAS
MOVING INTO SOUTHERN MINNESOTA AND SOUTHERN WISCONSIN.
PRECIPITATION ENDING WITH STEADY TO FALLING TEMPERATURES AND
INCREASING WEST WINDS:
THROUGH TODAY, THE CLOSED 500MB LOW OVER MONTANA WILL CONTINUE TO
PHASE WITH THE LOW OVER MINNESOTA, EVOLVING INTO A LARGE CLOSED
LOW OVER THE DAKOTAS. THIS LARGE AREA OF MID-TROPOSPHERIC LOW
PRESSURE WILL SLOWLY MOVE THROUGH THE UPPER MISSISSIPPI VALLEY
THROUGH WEDNESDAY AND THURSDAY. THE SURFACE COLD FRONT OVER THE
MISSOURI RIVER VALLEY WILL CONTINUE TO PUSH EAST THIS MORNING
WITH STEADY TO FALLING TEMPERATURES WITH LOWER 40S TO LOWER 50S
BY LATE AFTERNOON. THE PRECIPITATION SHIELD WILL CONTINUE TO
LIFT NORTH TODAY. ADDITIONAL RAIN AMOUNTS SHOULD MOSTLY BE IN
THE TRACE TO 0.10" RANGE WITH THE HIGHER AMOUNTS FOR CLARK AND
TAYLOR COUNTIES. THE 19.00Z PRECIPITABLE WATER (PWAT) VALUE AT
MPX WAS 1.27". THIS IS FORECAST TO LOWER TO 0.50" OR LESS BY
20.00Z. ALTHOUGH WE LOSE THE DEEP MOISTURE, LOW LEVEL MOISTURE
WILL CONTINUE TO AFFECT THE LOCAL AREA WRAPPING AROUND THE AREA
OF LOW PRESSURE. CONSIDERABLE CLOUDS ARE FORECAST TO HOLD ON
THROUGH MUCH OF THE DAY. PARTS OF IOWA AND MINNESOTA COULD SEE
SOME IMPROVEMENT PER THE RAP RH PROGS.
SCATTERED SNOW SHOWERS OVERSPREADING THE AREA WEDNESDAY WITH
REINFORCING COLD AIR (30-100% HREF PROBABILITIES FOR MEASURABLE
SNOW, BUT LOW PROBABILITIES FOR 1"). FALLING SNOW AND BRISK
WINDS COULD REDUCE VISIBILITIES:
REINFORCING COLD AIR IS FORECAST TO ADVECT SOUTHEAST ACROSS
MINNESOTA AND THE FORECAST AREA. DEEPENING MOISTURE COMBINED
WITH STEEP LAPSE RATES, INSTABILITY OF 50 TO 90 J/KG, SATURATION
THROUGH THE DENDRITIC GROWTH ZONE, LOW CONVECTIVE TEMPERATURES,
AND BRISK WEST WINDS IS ELEVATING THE POTENTIAL FOR SNOW
SHOWERS/THE SNOW SQUALL PARAMETER. THE PARAMETER COVERS MUCH OF
THE FORECAST AREA, BUT ESPECIALLY FROM SOUTHEAST MN INTO
NORTHEAST IA. A LOOK AT THE CAMS SHOWS A CONSISTENT SIGNAL FOR
SNOW SHOWERS TO OVERSPREAD THE AREA WEDNESDAY. LIGHT SNOW
ACCUMULATIONS WILL BE POSSIBLE ON GRASSY AREAS AND HIGHER
ELEVATIONS. 19.00Z HREF HAS 30 TO 100% CHANCE OF MEASURABLE SNOW
(0.1" OR MORE) OF SNOW AND 0 TO 15% PROBABILITY OF 1" OR MORE,
BUT HIGHER ELEVATIONS COULD SEE MORE. THERE ARE A FEW SPOTTY LOW
PROBABILITIES FOR 1" PER HOUR RATES. INTERESTINGLY THERE ARE
30-70% PROBABILITIES FOR VISIBILITY LESS THAN 1 MI., INCREASING
DURING THE AFTERNOON WITH THE DEEPENING OF THE COLD AIR/DEPTH OF
MOISTURE. THE AXIS OF STRONGER WINDS WITH GUSTS 25 TO 35 MPH IS
FROM MINNESOTA INTO IOWA. WILL CONTINUE TO MENTION THE
SCATTERED SNOW SHOWERS IN THE HWO ALONG WITH LIGHT ACCUMULATIONS
AND REDUCED VISIBILITIES. AT THIS TIME, SNOW RATES ARE NOT
EXPECTED TO OVERCOME THE MILD SOIL TEMPS/GROUND, THUS A FLASH
FREEZE IS NOT BEING MESSAGED. THE AXIS OF THE COLD AIR SHIFTS
TO THE EAST FOR THURSDAY, THUS THE SPOTTY SHOWERS WOULD BE A
RAIN/SNOW MIX.
RIDGING BUILDS IN FOR FRIDAY INTO THE WEEKEND...THEN SOME
TROUGHING EARLY NEXT WEEK WITH TEMPERATURES RETURNING TO
SEASONABLE LEVELS WITH HIGHS IN THE 30S AND 40S. PRECIPITATION
EARLY NEXT WEEK WILL BE DEPENDENT ON THE FORCING WITH ANY
EMBEDDED WAVES WITHING THE BROAD SCALE TROUGH.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1145 AM CST TUE NOV 19 2024
MAIN TAF CONCERNS ARE MVFR CONDITIONS THROUGH MUCH OF THE TAF
PERIOD. LOW PRESSURE WILL CONTINUE TO WRAP PERIODS OF STRATUS
DECK OF CLOUDS INTO BOTH THE RST/LSE TAF SITES THROUGH THE TAF
PERIOD. CURRENT CEILINGS UNDER THE STRATUS DECK ARE MVFR.
HOWEVER...THERE WILL BE A PERIOD OF VFR CONDITIONS AFTER 05Z
WEDNESDAY AT BOTH TAF SITES. THEN...MORE LOW LEVEL STRATUS DECK
OF CLOUDS ROTATE AROUND LOW PRESSURE INTO THE TAF SITES AFTER
12Z. THIS WILL PRODUCE MVFR CONDITIONS LATE IN THE TAF PERIOD.
IN ADDITION...SNOW SHOWERS ARE EXPECTED TO DEVELOP AND COULD
REDUCE VISIBILITY INTO MVFR AFTER 12Z WEDNESDAY. AT THIS
TIME...WILL INTRODUCE SNOW SHOWERS INTO THE TAFS AFTER 12Z
WEDNESDAY...BASED ON COVERAGE OF SNOW SHOWERS.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...ZAPOTOCNY
AVIATION...DTJ
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