273
FXUS63 KMPX 200848
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
248 AM CST WED NOV 20 2024
KEY MESSAGES
- LIGHT SNOW COVERAGE WILL INCREASE FROM WEST TO EAST TODAY. SLICK
TRAVEL IS POSSIBLE, ESPECIALLY WITH GUSTY WINDS.
- STRONGEST WINDS IN WESTERN MN, GUSTS AS HIGH AS 35MPH.
- QUIET WEATHER RETURNS THURSDAY, WITH COOLER TEMPERATURES
PERSISTING INTO NEXT WEEK.
DISCUSSION
ISSUED AT 248 AM CST WED NOV 20 2024
THE SATELLITE PRODUCTS OF CHOICE THIS MORNING INCLUDE BOTH THE
NIGHTTIME MICROPHYSICS RGB AS WELL AS THE DIFFERENT WATER VAPOR,
WHICH SHOW THE SUBTLE DIFFERENCES BETWEEN THE CVA FORCED EASTERN
EDGE OF THE INCOMING DEEP LOW PRESSURE SYSTEM AND THE MORE
GRADIENT/BOUNDARY FORCED WESTERN REGION. THERE IS A DEGREE OF
ROUGHNESS WITHIN THE CLOUD COVER SHOWING A SUBTLE CONVECTIVE ELEMENT
STRETCHING FROM SOUTH-CENTRAL MINNESOTA DOWN TOWARDS THE MN/IA/SD
BORDER, WITH A COUPLE RUMBLES OF THUNDER NOT OUT OF THE QUESTION
(FURTHER REINFORCED BY THE MPX 00Z SOUNDING PRODUCING A SMALL AMOUNT
OF SURFACE BASED CAPE). THE BAND OF LIGHT SNOW SHOWING UP ON RADAR
IS CONFINED TO THE PRIMARY FORCING ALONG THE STACKED LOW THAT WILL
MOVE THROUGH TODAY, CURRENTLY OVER THE EASTERN DAKOTAS APPROACHING
FAR WESTERN MN. THE BEST SHOT FOR ACCUMULATIONS ON THE ORDER OF A
FEW INCHES WILL REMAIN IN WESTERN MINNESOTA, FOR THE MPX COVERAGE
AREA GENERALLY IN AND AROUND DOUGLAS, POPE, STEVENS, AND SWIFT
COUNTIES; HOWEVER WE STILL ANTICIPATE SNOW FALLING ACROSS MUCH OF
THE AREA TODAY, ALBEIT AT LOWER OVERALL ACCUMULATION. THE TIMING
WILL BECOME A KEY THING TO WATCH AS OVERNIGHT CAM GUIDANCE HAS
HINTED AT A FEW BANDS OF STRONGER SNOW AMIDST THE LIGHTER RATES FROM
MID AFTERNOON TO EARLY EVENING DURING PRIME COMMUTER HOURS. THE
EXPECTATION FOR MOST PEOPLE WILL STILL BE A DUSTING ON GRASSY
SURFACES WITH LIMITED SNOW STICKING TO WELL TRAVELED ROADWAYS,
HOWEVER SHOULD WE SEE A BAND PRODUCING LOWER VISIBILITY AND HIGHER
RATES EVEN FOR A BRIEF PERIOD, THIS COULD RESULT IN SLICK ROADWAYS
AND TRAVEL CHALLENGES FOR THE EVENING COMMUTE. POSITIONING THE BANDS
BECOMES THE CHALLENGE AS THERE IS NO CLEAR CONSENSUS WITHIN THE
SUITE OF GUIDANCE, WITH SOUTHERN MN FAVORED TOWARDS THE LATER
PORTIONS OF THE EVENING. THE SYSTEM ITSELF IS EXPECTED TO WEAKEN AS
BOTH THE SURFACE LOW AND OCCLUSION ALOFT BEGIN TO POSITIVELY TILT
AND FLATTEN OUT AS THEY APPROACH THE GREAT LAKES WITH THE LIGHT SNOW
CEASING FROM LATE EVENING TO EARLY THURSDAY MORNING. THE OTHER THING
TO LOOK OUT FOR TODAY WILL BE A CONTINUATION OF THE STRONG WINDS WE
HAVE BEEN SEEING FROM THIS SYSTEM DUE TO A TIGHT PRESSURE GRADIENT
AND VERTICAL MIXING FORCED BY THE MULTIPLE LAYERS OF THE SYSTEM.
GUSTS COULD REACH AS HIGH AS 35MPH IN WESTERN AND SOUTHWESTERN
MINNESOTA DECREASING SLIGHTLY TO 25-30MPH FOR THE TWIN CITIES AND
WESTERN WISCONSIN.
AS THE SYSTEM WEAKENS AND MOVES EASTWARDS, PRECIPITATION WILL CEASE
BUT WINDS WILL STAY HIGHER AS THEY SHIFT NORTHWESTERLY ON THE
WESTERN SIDE OF THE DEPARTING SYSTEM. BLUSTERY CONDITIONS WILL
PERSIST THROUGH THURSDAY BEFORE FALLING BACK ON FRIDAY AS THE
GRADIENT WEAKENS WITH THE SYSTEM APPROACHING THE EASTERN COAST OF
THE US. BY SATURDAY OUR SURFACE WINDS WILL BE QUITE WEAK WITH
PERSISTENT WESTERLY TO NORTHWESTERLY FLOW ALOFT KEEPING WEAK
SUBSIDENCE LOCKED IN PLACE, WHICH WILL ALSO KEEP OUR TEMPERATURES
LOCKED INTO THE UPPER 30S FOR HIGHS COMPARED TO NEAR 30 FOR LOWS
THROUGH THE REST OF THE FORECAST PERIOD. OUR NEXT CHANCE FOR
PRECIPITATION WOULD POINT TOWARDS EARLY NEXT WEEK WITH A SYSTEM
MOVING WEST TO EAST ACROSS SOUTHERN CANADA, HOWEVER FOR NOW
PREDICTABILITY IS A BIT TOO LOW FOR ANY CERTAINTY GIVEN THE NEED FOR
BETTER FORCING ALONG ANY FRONTAL BOUNDARIES AS WELL AS VERTICAL
SUPPORT FROM A LACK OF AN UPPER LEVEL JET. ENSEMBLE GUIDANCE SHOWS
QUITE A SIGNIFICANT SPREAD WITH NO CLEAR CONSENSUS, AND WILL
CONTINUE TO DO SO UNTIL WE AT LEAST GET THROUGH THE NEXT 36-48 HOURS
AND KICK OUR ARRIVING SYSTEM OUT OF THE REGION.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1105 PM CST TUE NOV 19 2024
ANY VFR CIGS SHOULD DROP TO MVFR (NEAR 2000 FEET) BY SUNRISE
THIS MORNING AS LOW-LEVEL STRATUS MOVES IN FROM THE WEST. LIGHT
SNOW WILL START AT ABOUT 09-11Z IN WESTERN MN AND SPREAD EAST
WITH TIME THROUGHOUT THE MORNING. VISIBILITIES SHOULD DROP TO AT
LEAST 5 MILES DURING LIGHT SNOW. IN FACT, FORECAST MODELS SHOW
2 PERIODS OF POTENTIALLY HEAVIER SNOW. THE FIRST DURING THIS
MORNING AND THE SECOND BEING MID-AFTERNOON INTO EARLY THIS
EVENING. HAVE ADDED TEMPO GROUPS AT MOST TERMINALS TO ACCOUNT
FOR THIS WITH CONDITIONS DROPPING TO IFR/LIFR. SNOW WILL
EVENTUALLY TAPER OFF WEDNESDAY EVENING. WEST-SOUTHWESTERLY
WINDS WILL GRADUALLY BECOME NORTHWESTERLY WITH SPEEDS INCREASING
INTO THIS AFTERNOON AS A LOW-LEVEL JET MOVES OVER MN. STRONGEST
WINDS ARE EXPECTED IN WESTERN MN WHERE SUSTAINED VALUES WILL BE
NEAR 20 KNOTS AND GUSTS WILL BE NEAR 30 KNOTS. WINDS GRADUALLY
SLOW AS ONE GOES EAST WITH GUSTS NEAR 20 KNOTS AT RNH AND EAU.
WINDS SHOULD LESSEN A BIT WEDNESDAY EVENING.
KMSP...LIGHT SNOW WILL START AROUND 13Z WITH CONDITIONS DROPPING
TO MVFR. HAVE KEPT TEMPO FROM 14-18Z FOR PERIODS OF HEAVIER SNOW
RESULTING IN IFR VISIBILITY. SNOW SHOWERS WILL BECOME MORE
PREVALENT DURING THE AFTERNOON SO BREAKS IN MVFR VISIBILITY ARE
POSSIBLE. HOWEVER, FORECAST MODELS DO SHOW ANOTHER CHANCE OF
HEAVIER SNOW FROM 22-02Z SO HAVE ADDED A PROB30. WEST-
NORTHWESTERLY WINDS WILL GUST TO 20-25 KNOTS WEDNESDAY
AFTERNOON.
/OUTLOOK FOR KMSP/
THU...MVFR CIGS LIKELY. WIND NW 20-25G30-35KTS.
FRI...CHC MVFR CIGS. WIND NW 10-15KTS.
SAT...CHC MVFR CIGS. WIND NW 5-10 KTS.
MPX WATCHES/WARNINGS/ADVISORIES
MN...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR
DOUGLAS-POPE-STEVENS.
WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR LAC QUI PARLE-
YELLOW MEDICINE.
WI...NONE.
DISCUSSION...TDH
AVIATION...CTG
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