280
FXUS63 KMPX 082032
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
232 PM CST WED JAN 8 2025
KEY MESSAGES
- LIGHT SNOW WILL MOVE FROM WEST TO EAST ACROSS THE AREA
THURSDAY. MOST AREAS WILL SEE LESS THAN AN INCH OF SNOW,
HOWEVER SLICK SPOTS ARE POSSIBLE.
- CLIPPER SYSTEM TO BRING ANOTHER CHANCE FOR SNOW OVER THE
WEEKEND. CONFIDENCE IN INCREASING IN THE POTENTIAL FOR A FEW
INCHES OF ACCUMULATING SNOW, THOUGH TIMING IS STILL
UNCERTAIN.
DISCUSSION
ISSUED AT 219 PM CST WED JAN 8 2025
SUNSHINE AND TEMPERATURES IN THE TEENS ARE THE THEME ACROSS MOST OF
SOUTH CENTRAL MINNESOTA AND WESTERN WISCONSIN THIS AFTERNOON. THE
ONLY DIFFERENCE IN SKY COVER IS CAPTURED ON SATELLITE ACROSS CENTRAL
MINNESOTA, WHERE AN AREA OF STRATUS IS SLOWLY MEANDERING EAST FROM
ROUGHLY AXN TOWARDS STC (AND LOCATIONS TO THE NORTH). THE FORECAST
WILL REMAIN DRY TONIGHT, WITH THE UPPER RIDGE AXIS POSITIONED
ABOVE THE UPPER MIDWEST. WATER VAPOR IMAGERY SHOWS ASCENT
ACROSS SOUTHERN SASKATCHEWAN AND NORTHERN MONTANA, ASSOCIATED
WITH AN EASTWARD MOVING WAVE THAT WILL BRING THE CHANCE FOR
LIGHT SNOW ON THURSDAY. HIGH CLOUDS WILL BUILD AHEAD OF THIS
FEATURE, WHICH WILL COMBINE WITH LIGHT SOUTHERLY FLOW TO PREVENT
MOST AREAS FROM FALLING BELOW THE DOUBLE DIGITS TONIGHT.
THE AFOREMENTIONED WAVE IS PROGGED TO SLIDE EAST ACROSS THE DAKOTAS
TONIGHT AND WILL SEND A SURFACE COLD FRONT FROM WEST TO EAST ACROSS
MINNESOTA/WISCONSIN TOMORROW. WE ARE EXPECTING A "HIGH POP/LOW
QPF" PRECIPITATION SCENARIO, WHERE MAY LOCATIONS SEE SNOWFLAKES
FLY, HOWEVER POOR MOISTURE (A FEW HUNDREDTHS) AND STANDARD SLR'S
(~12:1) CAP SNOWFALL BELOW AN INCH FOR MOST COMMUNITIES. THE
HIGHEST AMOUNTS (SAY AN INCH AND A HALF IN ISOLATED SETTINGS)
APPEAR TO BE ALONG AND NORTH OF I-94 IN MINNESOTA, WHICH WILL BE
TIED TO BETTER FORCING ALOFT. NONETHELESS, FORECAST SOUNDINGS
DO CAPTURE A FEW HOURS OF DEEPER SATURATION IN TANDEM WITH
SUFFICIENT OMEGA FORCING TO PRODUCE LIGHT SNOW ACROSS MUCH OF
THE AREA. GIVEN HIGH CONFIDENCE LIGHT SNOW AND MINOR ACCUMULATIONS,
WE COLLABORATED WITH NEIGHBORING OFFICES TO BOOST POPS INTO THE
~60-80% RANGE ACROSS WEST CENTRAL MINNESOTA, WHERE HOURLY
PRECIPITATION >0.01" PROBABILITIES ARE THE HIGHEST PER THE 12Z
HREF. WHILE THIS WILL NOT BE A MAJOR SNOWFALL, THE INTRODUCTION
OF EVEN A HALF TO QUARTER INCH OF SNOW MAY BE ENOUGH TO PRODUCE
SLICK SPOTS THURSDAY AFTERNOON & EVENING. A FEW SNOWFLAKES MAY
LINGER AMID THE NORTHWEST FLOW ON FRIDAY MORNING, BEFORE THE
SOUTHWARD MOVEMENT OF 1020S CANADIAN HIGH PRESSURE RESULTS IN A
BRIEF PERIOD OF QUIET WEATHER FRIDAY AFTERNOON-SATURDAY
MORNING.
A POTENT CLIPPER, ORIGINATING ACROSS NORTHERN ALBERTA, IS PROGGED TO
DIVE SOUTHEAST ACROSS THE DAKOTAS SATURDAY MORNING. GUIDANCE DEPICTS
THE ~1002-1004MB LOW MOVING SOUTHEAST OUT OF THE DAKOTAS INTO
MINNESOTA/WISCONSIN SATURDAY EVENING THROUGH SUNDAY MORNING.
THE COMPACT CLIPPER IS SET TO PIVOT OVER SOUTHERN MN/NORTHERN
IA, BEFORE LIFTING TO THE NORTHEAST TOWARDS EASTERN WISCONSIN
(TOWARDS THE REGION OF WARM ADVECTION). THE TRACK OF THE
CLIPPER WILL FOLLOW THE THERMAL GRADIENT, SUCH THAT THERE WILL
LIKELY BE ADDITIONAL SUPPORT FOR PRECIPITATION FROM FRONTOGENIC
FORCING. LATEST GUIDANCE HAS TRENDED UPWARD WITH QPF, WITH
ENSEMBLE MEANS SUGGESTING A WIDE SWATH OF ~0.1" LIQUID
PRECIPITATION. A VARIETY OF INDIVIDUAL ENSEMBLE MEMBERS AND
DETERMINISTIC COUNTERPARTS HAVE TRENDED WETTER, WITH PERHAPS
UPWARDS OF ~0.2" OF QPF. THAT'S PLENTY OF MOISTURE TO WORK WITH
FOR THIS TIME OF YEAR, ESPECIALLY GIVEN THE EXPECTED HIGHER
RATIO NATURE OF THESE CLIPPER EVENTS (SLR'S BETWEEN 15-18:1 PER
THE LATEST NBM AND CONCEPTUALLY COULD BE HIGHER). FOR THIS
REASON, CONFIDENCE IS INCREASING IN WIDESPREAD ACCUMULATING SNOW
OVER THE WEEKEND. WE'LL HAVE TO FINE TUNE THE DETAILS OVER THE
COMING DAYS, AS TIMING AND DURATION OF SNOWFALL REMAIN IN FLUX,
BUT THE LARGE SCALE PIECES ARE POINTING IN A MORE LIKELY DIRECTION
FOR A FEW INCHES OF SNOW. FOR THIS REASON, WE COLLABORATED WITH
NEIGHBORING OFFICES TO BOOST QPF THROUGH 18Z SUNDAY, TO REFLECT
VALUES CLOSER TO THE ENSEMBLE MEAN REFERENCED ABOVE. ADDITIONALLY,
WE BOOSTED POPS SATURDAY NIGHT/SUNDAY MORNING, SO THE GRIDS NOW
FEATURE 40-50% POPS AT ALL FORECAST POINTS.
THE FORECAST DRIES OUT EARLY NEXT WEEK, FOLLOWING THE DEPARTING
LOW. COLD ADVECTION ACROSS THE UPPER MIDWEST WILL WORK TO DROP
TEMPERATURES INTO THE SINGLE DIGITS FOR HIGHS MONDAY/TUESDAY,
ALONG WITH THE POTENTIAL FOR SUB-ZERO LOWS. FACTOR IN WHAT MAY
END UP BEING A FRESH LAYER OF SNOW AND THESE VALUES COULD END UP
EVEN COLDER AS WE APPROACH THE END OF THE FORECAST PERIOD.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1121 AM CST WED JAN 8 2025
THE TREND FOR THE 18Z TAF PERIOD WILL BE SLOWLY INCREASING
CLOUDS WITH EVENTUAL LOWERING AS OUR NEXT WAVE OF LIGHT SNOW
ARRIVES LATE IN THE PERIOD. VFR WITH FEW/SCT HIGH CLOUDS TO
BEGIN, FOLLOWED BY MORE CLOUDS ARRIVING GENERALLY AFTER 06-08Z
BEFORE EVENTUAL -SN FROM WEST TO EAST. TIMING FOR INCOMING SNOW
WAS FOLLOWING THE QUICKER CAM GUIDANCE WITH THE HRRR/RAP SHOWING
A START TIME ROUGHLY 4-5 HOURS EARLIER THAN CURRENT GLOBAL
GUIDANCE. MVFR CIGS/VIS ARE POSSIBLE ONCE SNOW STARTS WITH BKN
CIGS LOWERING GRADUALLY IN THE 3-4 HOURS BEFORE ARRIVAL. WINDS
REMAIN BELOW 10KTS WITH NO SIGNIFICANT GUSTS.
KMSP...SNOW ARRIVAL TIME WITHIN CURRENT GUIDANCE IS AROUND
17-18Z, AND THIS MAY WOBBLE AN HOUR OR TWO OVER THE NEXT COUPLE
OF TAF ISSUANCES BASED ON THE LATEST GUIDANCE. ACCUMULATION
POTENTIAL RIGHT NOW IS EXPECTED TO REMAIN AN INCH OR LOWER WITH
THE BEST CHANCE FOR IMPACTS FROM ROUGHLY 18-21Z, GIVE OR TAKE AN
HOUR OR TWO BASED ON WHEN IT ARRIVES. RATES SHOULD GENERALLY
REMAIN LESS THAN 1/4 INCH PER HOUR.
/OUTLOOK FOR KMSP/
FRI...MVFR/-SNSH EARLY, THEN VFR. WIND NW 5-10KTS.
SAT...VFR. WIND W TO S 5-10KTS.
SUN...VFR, SL CHC -SNSH/MVFR. WIND NW 5-10KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
DISCUSSION...STRUS
AVIATION...TDH
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