048
FXUS63 KDLH 191752
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1152 AM CST THU DEC 19 2024
UPDATE
ISSUED AT 755 AM CST THU DEC 19 2024
THE DECISION WAS MADE TO DOWNGRADE THE WINTER STORM WARNINGS FOR
SOUTHERN CASS, CROW WING, SOUTHERN AITKIN, AND PINE COUNTIES TO
WINTER WEATHER ADVISORIES AS THE POTENTIAL FOR SEEING 6+" OF
SNOW IN THOSE COUNTIES HAS DIMINISHED AND NOW AN ADDITIONAL
2-4" OF SNOWFALL ARE EXPECTED THROUGH THIS EVENING. SURFACE
OBSERVATIONS AND SNOW REPORTS THAT HAVE COME IN SO FAR SHOW THAT
THE HEAVIER SNOW BAND/RATES SHIFTED SLIGHTLY FARTHER SOUTH INTO
CENTRAL AND SOUTHEAST MN RELATIVE TO WHAT WAS FORECAST. 850-600
MB FRONTOGENETIC FORCING FOR LIFT WILL STILL BE PRESENT ACROSS
THE AFOREMENTIONED ROW OF COUNTIES THROUGH MIDDAY, WHICH WILL
STILL SUPPORT RATES UP TO AROUND 0.5"/HR, BUT RATES WILL BECOME
MUCH LIGHTER IN THOSE LOCATIONS THIS AFTERNOON AND EVENING AS
THE BETTER SYNOPTIC LIFT SHIFTS OFF TO THE SOUTHEAST.
THE WINTER STORM WARNINGS FOR CARLTON/SOUTH ST. LOUIS, LAKE, AND
BAYFIELD COUNTIES REMAIN IN PLACE FOR NOW, THOUGH THE LATEST
HI-RES MODEL GUIDANCE DOES SUGGEST A REDUCTION IN TOTAL SNOWFALL
FOR THESE LOCATIONS, AS WELL. THE MAIN SNOWFALL-PRODUCING
FEATURE WE WILL CONTINUE TO MONITOR FOR IS A NARROW LAKE-
ENHANCED BAND THAT IS CLOSER TO FAR SOUTHWESTERN COOK COUNTY
THIS MORNING, BUT WILL BE RACING BACK DOWN THE NORTH SHORE THIS
AFTERNOON INTO MID-EVENING AS WINDS SHIFT TO NORTHEASTERLY. SOME
CONVERGENCE OF THE BAND IN THE HEAD OF LAKE SUPERIOR IS ALSO
EXPECTED THIS EVENING BEFORE WINDS SHIFT MORE NORTHERLY LATER
THIS EVENING AND TONIGHT, PUSHING THE LAKE-ENHANCED BAND INTO
THE SOUTH SHORE, PARTICULARLY THE BAYFIELD PENINSULA. RATES WITH
THIS BAND ALSO HAVE THE POTENTIAL TO REACH 0.5-0.75"/HR. HIGHER
ACCUMULATIONS (5-6+") WILL DEPEND ON HOW LONG THIS LAKE-
ENHANCED BAND REMAINS OVER ANY ONE LOCATION, AS IT APPEARS TO BE
SOMEWHAT TRANSIENT IN NATURE, WITH THE HIGHER TERRAIN OF DULUTH
TO SILVER BAY AND THE BAYFIELD PENINSULA BEING MOST FAVORED TO
SEE THIS HIGHER SNOWFALL POTENTIAL.
KEY MESSAGES
- A POTENT CLIPPER SYSTEM WILL BRING WIDESPREAD SNOW FROM 2 TO 6
INCHES WITH LOCALLY HIGHER AMOUNTS POSSIBLE ALONG THE LAKE
SUPERIOR SHORELINES AND PARTS OF EAST-CENTRAL MINNESOTA INTO
NORTHWEST WISCONSIN. THE HIGHER AMOUNTS ARE EXPECTED TO BE
VERY LOCALIZED.
- A COOL WEATHER PATTERN UNTIL AROUND SATURDAY WITH BELOW ZERO
LOWS, THEN WARMING UP SUNDAY INTO NEXT WEEK.
- THE WEATHER PATTERN LOOKS TO REMAIN ACTIVE WITH ON-AND-OFF
SNOW CHANCES.
DISCUSSION
ISSUED AT 432 AM CST THU DEC 19 2024
TODAY AND TONIGHT (CLIPPER SYSTEM WITH SNOW):
SO HERE WE ARE ON THURSDAY MORNING WITH THIS WELL-ADVERTISED
CLIPPER STARTING TO PRODUCE SOME SNOW. THE MAIN AXIS OF FGEN-
INDUCED SNOW IS AFFECTING THE TWIN CITIES AND GENERAL
CENTRAL/SOUTHERN MINNESOTA AREAS, EXTENDING INTO NORTHWEST
MINNESOTA. THE FIRST ECHOES ARE STARTING TO AFFECT CASS AND CROW
WING COUNTIES, AND SNOW IS EXPECTED TO SPREAD EAST THIS MORNING.
WE ALSO HAVE A LIGHT LAKE-EFFECT SNOW BAND THAT STARTED AROUND
THE TWIN PORTS AND IS NOW MIGRATING SLOWLY NORTHWARD ACROSS THE
NORTH SHORE.
THE MAIN CHANGE WITH THIS FORECAST UPDATE IS A BIT OF A DROP IN
SNOWFALL AMOUNTS AS THE MAIN AXIS OF SNOW IS ALREADY AND IS
EXPECTED TO LARGELY PASS BY TO THE SOUTH, WITH THE HEAVIEST SNOW
EXPECTED ROUGHLY FROM THE TWIN CITIES THROUGH PINE CITY. WITH
THE HEAVIEST SYNOPTIC SNOW NOW EXPECTED JUST SOUTH OF THE
REGION, QPF AMOUNTS HAVE DROPPED OFF A BIT, AND WITH MOST MODEL
GUIDANCE SUGGESTING AMOUNTS IN THE VICINITY OF 0.3" FOR THE
EAST-CENTRAL MINNESOTA INTO NORTHWEST WISCONSIN AREAS. WE STILL
EXPECT SNOWFALL RATIOS TO LIE SOMEWHERE BETWEEN 15:1 AND 20:1,
SO DESPITE LOWER QPF, POTENTIAL FOR ACCUMULATING SNOW IS STILL
THERE.
AS FAR AS HEADLINES GO, WE DECIDED TO KEEP THEM AS-IS FOR
SEVERAL REASONS. AT THIS POINT, THIS IS EXPECTED TO BE A VERY
LOW-END WARNING CRITERIA SYSTEM FOR PLACES IN A WINTER STORM
WARNING. BUT, DESPITE MOST CAMS TAKING THE HEAVIEST AXIS OF SNOW
SOUTH, THERE'S ENOUGH GUIDANCE THAT STILL SUGGESTS A BRIEF
NORTHWARD JOG COULD STILL OCCUR THIS MORNING AND PRODUCE
SNOWFALL RATES AROUND 0.5" PER HOUR (70-80% CHANCE) AND PERHAPS
APPROACHING 1" PER HOUR LOCALLY (20-30% CHANCE). THIS WILL BE
MOST LIKELY AROUND SOUTHERN AITKIN TO PINE TO BURNETT COUNTIES.
ALL SAID AND DONE, WE ARE LIKELY TO SEE SNOWFALL AMOUNTS AROUND
3-6 INCHES THERE AND PERHAPS LOCALLY HIGHER IN THESE AREAS.
CONFIDENCE SIMPLY ISN'T HIGH ENOUGH TO DOWNGRADE ANY OF THE
WARNINGS OR UPGRADE ANY OF THE ADVISORIES WITH FORECAST TOTALS
FLOATING RIGHT AROUND THE 6" WARNING/ADVISORY THRESHOLD, SO WE
DECIDED TO LEAVE HEADLINES AS THEY ARE. SO, EXPECT HIGH-END
ADVISORY TO LOW-END WARNING CRITERIA SNOWFALL AMOUNTS ACROSS
EAST-CENTRAL MINNESOTA INTO NORTHWEST WISCONSIN.
A SIMILAR DECREASING TREND IN SNOWFALL IS EXPECTED AROUND THE
SHORES OF LAKE SUPERIOR WITH THE BULK OF THE SYNOPTIC SNOW
PASSING SOUTH. HOWEVER, WE DO ALREADY HAVE A LAKE-EFFECT BAND
GOING (LIGHT THOUGH IT MAY BE), AND OROGRAPHIC ENHANCEMENT IS
EXPECTED TO BEGIN ONCE WE GET THE SYNOPTIC SNOW MOVING IN AND
GET SEEDING FROM ALOFT. MUCH OF THE ENHANCED SNOW IN AND AROUND
THE TWIN PORTS THIS MORNING IS LIKELY TO BE ALMOST EXCLUSIVELY
OROGRAPHIC WITH SOUTHEAST FLOW. THUS, THE LOCALLY HIGHER AMOUNTS
THAT MAY REACH AROUND 6 TO 7 INCHES ARE EXPECTED TO BE PRETTY
WELL LOCALIZED TO WITHIN ABOUT 10 MILES OF SHORELINE, AND
ESPECIALLY AFFECTING COMMUNITIES SUCH AS PROCTOR, PIEDMONT,
DULUTH HEIGHTS, KENWOOD, AND WOODLAND AROUND THE TWIN PORTS.
AMOUNTS MAY BE SLIGHTLY LESSER AT LOWER ELEVATIONS, BUT NOT BY
MUCH. AMOUNTS DROP OFF BY SEVERAL INCHES PRETTY QUICKLY MOVING
BEYOND ABOUT 10 MILES OF THE LAKESHORE.
THE LAKE-EFFECT BAND MAY INCREASE IN INTENSITY AS SYNOPTIC SNOW
MOVES IN TO SEED IT FROM ALOFT, BUT IT IS ALSO EXPECTED TO BE
PRETTY TRANSIENT ALONG THE NORTH SHORE TODAY AS WIND DIRECTIONS
WOBBLE BACK-AND-FORTH TO MORE SOUTHEASTERLY THIS MORNING, THEN
EAST TO NORTHEASTERLY THIS AFTERNOON. THEREFORE, HIGHER END
LOCALIZED TOTALS TO 6 OR 7 INCHES ARE EXPECTED TO GRADUALLY
DROP OFF GOING NORTHEAST OF ABOUT TWO HARBORS.
THIS AFTERNOON, AS LOW PRESSURE PASSES BY TO THE SOUTH AND WINDS
BECOME NORTHEASTERLY, HEAVIER SNOWFALL RATES ASSOCIATED WITH THE
SYNOPTIC SNOW ARE EXPECTED TO DECREASE FROM WEST TO EAST. THE
MAIN LAKE-EFFECT SNOW BAND ALONG THE NORTH SHORE WILL START TO
DRIFT SOUTH, AND WE WILL LIKELY GET SOME ADDITIONAL STREAMERS
DEVELOPING TOWARDS THE TWIN PORTS AS WINDS BECOME MORE
NORTHEASTERLY. THUS, WHILE SNOWFALL RATES DECREASE EVERYWHERE
ELSE, THEY ARE LIKELY TO REMAIN AROUND THAT 0.5" PER HOUR RATE
LOCALLY THROUGH THE AFTERNOON AND EVENING COMMUTE. IN THE
EVENING, THE LAKE-EFFECT DRIFTS INTO THE BAYFIELD PENINSULA AND
WILL LIKELY TAKE THE FORM OF A PRIMARY CONVERGENCE BAND WITH
SOME NEARBY STREAMERS FOR A WHILE AS WINDS BECOME NORTHERLY.
MOST CAMS SUGGEST A SEVERAL-HOUR PERIOD OF MODERATE TO HEAVY
SNOW POTENTIAL ROUGHLY FROM BAYFIELD THROUGH WASHBURN AND
PERHAPS ALSO ASHLAND BETWEEN ABOUT 9 PM AND 2 AM, DROPPING ABOUT
2-5 INCHES OF SNOW AND BRINGING STORM TOTALS TO AROUND 6 TO 7
INCHES LOCALLY. WINDS BECOME NORTH TO NORTHWESTERLY BY EARLY
FRIDAY MORNING, LIMITING REMAINING LAKE-EFFECT TO IRON COUNTY.
ALL THINGS SAID, WITH THE MORE SOUTHERLY TRACK OF THIS CLIPPER,
EXPECT SOME SLIGHTLY LOWER SNOWFALL AMOUNTS COMPARED TO THE
PREVIOUS FORECAST (AROUND 2-6" REGIONWIDE), BUT LOCALLY HIGHER
AMOUNTS NEAR LAKE SUPERIOR AND ALSO AREAS AROUND AND SOUTH OF
HINCKLEY.
FRIDAY AND SATURDAY (COOL WEATHER):
A COLD AIR MASS MOVES IN WITH NORTH TO NORTHWEST FLOW ON FRIDAY.
LOWS IN THE SINGLE DIGITS TO TEENS BELOW ZERO ARE EXPECTED
FRIDAY NIGHT WITH WIND CHILLS IN THE TEENS FOR MANY PLACES. A
WEAK CLIPPER MIGHT BRING A STRIPE OF <1" OF SNOW AROUND THE
BRAINERD LAKES, AND CLOUDS ASSOCIATED WITH THIS WILL LIKELY
PREVENT TEMPERATURES FROM FALLING TOO MUCH LOWER THAN THE
CURRENT FORECAST.
SUNDAY AND MONDAY (WARMUP AND POTENTIAL CLIPPER):
SOUTHWESTERLY WARM AIR ADVECTION IS EXPECTED SUNDAY AHEAD OF A
POTENTIAL CLIPPER SYSTEM. PLENTY OF UNCERTAINTY WITH THIS
CLIPPER FOR TIMING AND MOISTURE POTENTIAL, BUT IT HAS POTENTIAL
TO PRODUCE SOME LIGHT ACCUMULATING SNOW.
HOLIDAY OUTLOOK:
LONG-RANGE MODELS SEEM TO FAVOR SOMETHING ALONG THE LINES OF AN
OMEGA BLOCK DEVELOPING AROUND CHRISTMAS. THIS WOULD MEAN PRETTY
QUIET AND MILD WEATHER FOR THE HOLIDAY. THE WEATHER COULD BECOME
MORE ACTIVE AFTER THAT.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1152 AM CST THU DEC 19 2024
VISIBILITIES ARE VFR AT NORTHERN TERMINALS WITH MUCH LIGHTER
SNOWFALL RATES. MOST OF THE REMAINING TERMINALS IN THE
NORTHLAND HAVE VISIBILITIES VARYING BETWEEN MVFR AND IFR THROUGH
THE AFTERNOON, WITH VISIBILITIES IMPROVING WEST TO EAST THIS
EVENING AS SNOWFALL RATES DECREASE, ASIDE FROM LOCATIONS NEAR
LAKE SUPERIOR. DLH SHOULD SEE 1SM TO 3/4SM VISIBILITIES THROUGH
THE AFTERNOON INTO EARLY EVENING AS A LAKE-EFFECT SNOW BAND
PASSES THROUGH. VISIBILITIES RETURN TO VFR OVERNIGHT AS SNOW
COMES TO AN END. EAST WINDS WITH GUSTS UP TO 15 KNOTS AT TIMES
WILL BACK TO NORTHEAST LATER THIS AFTERNOON AND NORTHERLY
TONIGHT AS THE LOW PRESSURE MOVES SOUTHEAST OF THE REGION.
EXPECT CLEARER SKIES AND VFR CONDITIONS FOR MOST OF THE
NORTHLAND ON FRIDAY.
MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
ISSUED AT 432 AM CST THU DEC 19 2024
GUSTY EAST WINDS, BECOMING NORTHERLY TONIGHT, ARE EXPECTED TO
DEVELOP THIS MORNING. WIDESPREAD GUSTS FROM 20 TO 30 KT ARE
EXPECTED THIS AFTERNOON THROUGH FRIDAY MORNING ALONG WITH WAVE
HEIGHTS UP TO AROUND 6 TO 7 FT ALONG THE SOUTH SHORE. SNOW IS
EXPECTED THROUGH THIS PERIOD AS WELL.
AFTER THAT, WINDS BECOME LIGHTER FROM THE NORTH TO NORTHWEST
THROUGH FRIDAY NIGHT, THEN SOUTHERLY THROUGH THE WEEKEND. THERE
COULD BE SOME LOCALLY BREEZY CONDITIONS FOR PARTS OF THE NORTH
SHORE ON SUNDAY WITH GUSTS APPROACHING 20 TO 25 KT.
FOR THE OPEN WATER DISCUSSION, REFER TO THE NWS MARQUETTE AREA
FORECAST DISCUSSION AT WEATHER.GOV/MQT.
DLH WATCHES/WARNINGS/ADVISORIES
MN...WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR MNZ010-
018-019-021-025-026-033>036-038.
WINTER STORM WARNING UNTIL MIDNIGHT CST TONIGHT FOR MNZ020-037.
WI...WINTER WEATHER ADVISORY UNTIL 6 AM CST FRIDAY FOR WIZ001.
WINTER STORM WARNING UNTIL 6 AM CST FRIDAY FOR WIZ002.
WINTER WEATHER ADVISORY UNTIL 9 AM CST FRIDAY FOR WIZ003-004.
WINTER WEATHER ADVISORY UNTIL 3 AM CST FRIDAY FOR WIZ006>009.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 10 AM CST
FRIDAY FOR LSZ121-146>148-150.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 8 AM CST FRIDAY
FOR LSZ140-143.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 8 AM CST
FRIDAY FOR LSZ141-142.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST FRIDAY
FOR LSZ144-145.
UPDATE...JDS
DISCUSSION...JDS
AVIATION...ROTHSTEIN
MARINE...JDS
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