816
FXUS63 KARX 191202
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
602 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 /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 601 AM CST TUE NOV 19 2024
A TRICKY CIG FORECAST IS IN ORDER FOR MUCH OF THIS MORNING AND EARLY
AFTERNOON AS LOW PRESSURE PULLS AWAY FROM THE REGION. AS THIS
OCCURS, LOW-LEVEL MOISTURE WILL REMAIN PRESENT ACROSS THE AREA WITH
GUIDANCE OVERWHELMINGLY FAVORING (80-100% CHANCE IN THE 19.06Z
HREF) MVFR CIGS ACROSS THE ENTIRE LOCAL AREA. CONFIDENCE FOR IFR
CIGS REMAINS THE MAIN FORECAST CONSIDERATION DURING THE LATE
MORNING AND AFTERNOON HOURS. CURRENTLY, PROBABILISTIC GUIDANCE
AND MODEL SOUNDINGS WOULD CONTINUE TO SUGGEST A PERIOD OF IFR
CIGS AT KRST WITH THE 19.06Z HREF AND RECENT NBH HAVING FAIRLY
ROBUST PROBABILITIES (40-80% CHANCE) FOR IFR CIGS. CIGS WILL
GRADUALLY IMPROVE TO VFR TOWARDS THE LATE AFTERNOON AND EVENING
HOURS ACROSS THE REGION. WINDS OF 10-20 KTS ARE EXPECTED
THROUGHOUT MUCH OF THE AFTERNOON WITH GUSTS OF UP TO AROUND 30
KTS IN UNSHELTERED AREAS OF SOUTHEAST MN AND NORTHEAST IA.
WESTERLY WINDS WILL DIMINISH TO BETWEEN 8-12 KTS BY THE
OVERNIGHT HOURS.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...ZAPOTOCNY
AVIATION...NAYLOR
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