627
FXUS63 KDTX 080921
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
421 AM EST MON DEC 8 2025
KEY MESSAGES
- BELOW NORMAL TEMPERATURES PERSIST TODAY WITH MORNING WIND CHILLS
NEAR OR BELOW ZERO.
- ISOLATED LAKE EFFECT SNOW SHOWERS ALONG THE SOUTHERN LAKE HURON
COASTLINE THROUGH THE MORNING HOURS.
- ACTIVE WINTRY STRETCH COMMENCES LATE TONIGHT OR EARLY TUESDAY
MORNING WITH ADDITIONAL OPPORTUNITIES FOR ACCUMULATING SNOW,
RANGING FROM 0.3-1.5 INCHES.
- AREAS OF LIGHT FREEZING RAIN/DRIZZLE POSSIBLE DURING THE DAY
TUESDAY AS TEMPERATURES RISE TO AROUND THE FREEZING MARK.
- SNOW THEN BRIEFLY RETURNS TUESDAY NIGHT BEFORE CHANGING OVER TO
LIQUID RAIN FOR MOST OF SOUTHEAST MICHIGAN; AREAS ALONG/NORTH OF M-
46 COULD MAINTAIN ALL SNOW LEADING TO ACCUMULATIONS IN EXCESS OF 3
INCHES.
- COLDER AIR RETURNS WEDNESDAY EVENING WITH A BIT OF ADDITIONAL LIGHT
SNOW POSSIBLE, FOLLOWED BY THE NEXT ARCTIC AIRMASS HEADING INTO THE
WEEKEND.
- PERIODIC LAKE EFFECT SNOW CHANCES EXIST FROM THURSDAY ONWARD.
DISCUSSION
CHILLY START TODAY WITH READINGS IN THE SINGLE DIGITS, OUTSIDE OF
METRO DETROIT AND THE LAKE HURON COASTLINE. INITIAL WIND CHILLS WILL
NOT DEVIATE MUCH COMPARED TO TEMPERATURES GIVEN LIGHT TO CALM
GRADIENT WINDS. SUB-700 MB ANTICYCLONE PASSES OVER LOWER MICHIGAN
TODAY LEADING TO A LAYER OF SUBSIDENCE BETWEEN 3 KFT AND 12 KFT WITH
A MAXIMUM 35C DEWPOINT DEPRESSION. MEANWHILE, MOISTURE SPILLS IN
ALOFT ALONG A LOW AMPLITUDE SHORTWAVE TROUGH, LEADING TO A CANOPY OF
HIGH CLOUDS AS LOWER COLUMN TRAJECTORIES ACROSS THE HURON BASIN
GENERATE PATCHES OF STRATOCUMULUS, DOWNWIND OF THE SOUTHERN COAST.
GIVEN THE SHALLOW MIXED-LAYER AND 925 MB TEMPERATURES AROUND -10C,
DAYTIME HIGHS WILL STRUGGLE TO BREAK MUCH BEYOND THE MID-UPPER 20S
WHILE THE RESIDENT ARCTIC AIRMASS HOLDS (10-15 DEGREES BELOW
SEASONAL NORMALS).
THE SURFACE PRESSURE FIELD TRANSITIONS FROM HIGH PRESSURE TO LOW
PRESSURE DOMINANT OVERNIGHT AS A CLIPPER DIGS INTO THE UPPER
MIDWEST. GRADIENT FLOW STRENGTHENS, STARTING OUT SOUTHERLY, AND
FORESHADOWING THE CONSEQUENTIAL WARM SECTOR ARRIVAL WITHIN THE
OCCLUSION OF THE PRIMARY (SOUTHERN) SURFACE REFLECTION. A PLUME OF
PACIFIC MOISTURE ASSOCIATED WITH THIS CIRCULATION ACCOMPANIES THE
VORTMAX PROMOTING THE QUICK ONSET OF NOCTURNAL PRECIPITATION. THE
ELEVATED WARM FRONT MODIFIES THE LOWER LEVELS, SETTING UP AN
INVERSION BETWEEN THE 2-6 KFT AGL LAYER. INITIAL PRECIPITATION FALLS
AS SNOW BETWEEN 07Z AND 11Z (FROM WEST TO EAST). IN SPITE OF
NOCTURNAL WARMING, SURFACE TEMPERATURES SHOULD BE PLENTY COLD FOR
ACCUMULATION INTO THE EARLY MORNING HOURS ON TUESDAY. DGZ DEPTHS ARE
SUFFICIENT, BUT NOT MUCH QPF TO WORK WITH, SO EXPECT ONLY A COATING
TO AN INCH. INTERESTING NOTE ABOUT THE 07Z NBM SNOWFALL PERCENTILES
THROUGH TUESDAY (18Z). QUITE A BIG DIFFERENCE BETWEEN THE 50TH AND
75TH PERCENTILES, WITH 0.3-1.0 INCHES FOR THE FORMER, AND 1.0-2.5
INCHES FOR THE LATTER. OUTGOING FORECAST FALLS BETWEEN THE TWO
RANGES. ENSURED A MINIMUM ACCUMULATION OF AROUND A QUARTER INCH, BUT
ALLOWED FOR OVER AN INCH FOR THE THUMB WHERE MIXED PRECIPITATION
CHANCES WILL BE LOWER.
PRECIPITATION TYPE CONCERNS ARISE DURING THE DAYLIGHT HOURS TUESDAY
AS FORECAST SOUNDINGS REVEAL ISSUES WITH DGZ DEPTH AND DURATION OF
SATURATION. AFTER THE INITIAL BURST OF MORNING SNOW, THE SURFACE TO
10 KFT LAYER WARMS ABOVE -10C AND BEGINS TO DRY OUT (DOWN TO 5 KFT)
UPON INCREASING ZONAL FLOW. AT THE SAME TIME, THE OMEGA SIGN
REVERSES LEADING TO SUBSIDENCE WITHIN THE MID-LEVELS. THIS EXTENDS
TO ICE NUCLEATION PROBLEMS LIMITING SNOW GENERATION ALOFT. HIGHER
POTENTIAL EXISTS FOR AN ALL-SNOW SCENARIO NORTH OF I-69 WHICH IS
WHERE THE HIGHER DAYTIME QPF SHOULD FALL. AS FOR THE SOUTHERN HALF
OF THE FORECAST AREA, A MIX OF LOW SLR (WET/FINE SNOW) AND FREEZING
DRIZZLE COULD LEAD TO A THIN GLAZE OF ICE, GENERALLY ATOP EXISTING
SNOWPACK. TEMPERATURES WILL BE NEAR/ABOVE FREEZING LATE AFTERNOON
AND EVENING, SO ICE ACCRETION WILL BE MORE QUESTIONABLE ON OTHER
SURFACES. HIGH TEMPERATURES ARRIVE AROUND SUNSET.
THE NEXT VORTMAX AND 985 MB SURFACE LOW ARRIVE TUESDAY NIGHT INTO
WEDNESDAY AS THE ACTIVE QUICK-HITTING PATTERN HOLDS. TEMPERATURES
WILL BE SLOW TO DROP BELOW FREEZING EARLY TUESDAY NIGHT AS THE NEXT
ROUND OF PRECIPITATION GETS UNDERWAY. LATEST MODEL DATA SHOWS A
SIMILAR PROGRESSION WITH SNOW TO START BEFORE SWITCHING OVER TO
PRIMARILY RAIN LATE TUESDAY NIGHT OR EARLY WEDNESDAY MORNING.
PRECIPITATION TYPE DIFFERENCES EXIST BETWEEN THE NORTHERN AND
SOUTHERN PARTS OF THE CWA WITH A MUCH LOWER LIKELIHOOD FOR A LIQUID
TRANSITION TO THE NORTH. HIGHER SNOWFALL TOTALS ARE THEREFORE
PREDICTED ALONG/NORTH OF M-46 WHERE PRECIPITATION SHOULD CONTINUE
EXCLUSIVELY AS SNOW ALL DAY WEDNESDAY. WINTER WEATHER ADVISORY
CONSIDERATIONS WILL NEED TO BE MADE FOR THE NORTHERN COUNTIES IN
SUBSEQUENT FORECAST UPDATES. KEPT INHERITED NBM SNOWFALL WITH TOTALS
IN THE 3-5 INCH RANGE. FURTHER SOUTH, DRYING IN THE MID AND UPPER
LEVELS ENSURES A PERIOD OF COLD LOW STRATUS RAIN UNTIL MIDDAY. ONCE
THE SYSTEM'S COLD FRONT SWINGS THROUGH, EXPECT A FLIP BACK TO SNOW
ACROSS SOUTHEAST MICHIGAN FOR THE FORESEEABLE FUTURE. ADDITIONAL
ACCUMULATIONS WILL BE LIGHTER ALONG THE BACK END OF THE EVENT
WEDNESDAY AND INTO THURSDAY WITH TEMPERATURES DROPPING BELOW NORMAL
OVERNIGHT.
THE COLDER POST-FRONTAL AIRMASS WORKS IN CONCERT WITH PERIODIC
TRAJECTORIES FOR SUFFICIENT FETCH FOR SOME LAKE EFFECT SNOW CHANCES
THROUGH THE END OF THE WORKWEEK. SOME EVIDENCE EXISTS FOR A THIRD
CLIPPER ON FRIDAY, BUT POSITIONING WITHIN THE MEAN FLOW IS
QUESTIONABLE AS IT WOULD PERTAIN TO THE LOCAL AREA. COULD GET SOME
SYNOPTIC DRIVEN SNOW IF THINGS FALL INTO PLACE. THE NEXT RELEASE OF
ARCTIC AIR REMAINS ON TRACK FOR ARRIVAL BY SATURDAY. 850 MB
TEMPERATURES COULD DROP BELOW -20C AS COLDER THAN NORMAL
TEMPERATURES LOCK-IN FOR THE WEEKEND.
MARINE
NORTHERLY WINDS CONTINUE TO DECREASE THIS MORNING AS HIGH PRESSURE
SETTLES OVER THE CENTRAL GREAT LAKES, LEADING TO LIGHT WINDS TODAY,
BUT SHIFTING TO THE SOUTHWEST AND THEN RAMPING UP THIS EVENING.
STILL LOOKING AT BRIEF SOUTHWEST GALES POSSIBLE LATE TONIGHT INTO
TUESDAY MORNING AS LOW PRESSURE TRACKS THROUGH THE NORTHERN GREAT
LAKES. THE STRONGEST WINDS LOOKING TO BE OVER SAGINAW BAY/CENTRAL
LAKE HURON. SNOW WILL LIKELY CAUSE SOME PRECIP DRAG, WHICH SHOULD
HELP LIMIT THE MAGNITUDE AND DURATION OF ANY GALES THAT DEVELOP.
A LARGER AND STRONGER LOW PRESSURE SYSTEM IS THEN ON TRACK TO MOVE
THROUGH LOWER MICHIGAN TUESDAY NIGHT INTO WEDNESDAY PRODUCING
WIDESPREAD SNOW AND EVEN RAIN OVER LAKE
ST. CLAIR AND LAKE ERIE. THE SOUTHWEST LOW LEVEL JET AHEAD OF THE
LOOKS TO BE VERY STRONG, AND LOW LEVEL PROFILES DO NOT APPEAR TO
WARM QUICK ENOUGH TO STABILIZE THE NEAR WATER SURFACE. THUS, IT IS
LOOKING LIKE INCREASING CHANCE OF GALES OF WESTERN LAKE ERIE, WITH
POTENTIAL TO BRIEFLY REACH AOA 40 KNOTS.
RUSH OF COLD AIR BEHIND THE PASSAGE OF THE LOW WILL THEN SUPPORT
STRONG NORTHWEST WINDS LATE WEDNESDAY AND WEDNESDAY EVENING.
ISOLATED, BRIEF GUSTS TO GALES WILL BE POSSIBLE,
BUT THE PRESSURE GRADIENT QUICKLY RELAXES BY THURSDAY MORNING.
PREV DISCUSSION
ISSUED AT 1145 PM EST SUN DEC 7 2025
AVIATION...
SYSTEM RELATIVE ISENTROPIC ANALYSIS SUPPORTS HIGHLY EFFICIENT, VERY
DEEP DESCENT TONIGHT. WATCHING FOR THE POTENTIAL OF LAKE HURON LAKE
EFFECT SNOW SHOWERS TO PUSH INLAND/WESTWARD TONIGHT INTO PORTIONS OF
THE THUMB AS MASS CENTROID OF SURFACE ANTICYCLONE BEGINS TO EXPAND
INTO FAR SOUTHWESTERN ONTARIO. GRADIENT FLOW IS FORECASTED TO EMERGE
EASTERLY AT SOME POINT THIS MORNING. GIVEN THE BACKGROUND FORCING
FOR ISENTROPIC DOWNGLIDE HERE OVER SOUTHEAST MICHIGAN, NOT EXPECTING
MUCH LAKE EFFECT CLOUD TO IMPACT THE TAF SITES. DAYTIME HEATING IS
EXPECTED TO RESULT IN SOME BOUNDARY LAYER CLOUD DURING THE MORNING
HOURS MONDAY BEFORE LIFTING FOR THE AFTERNOON. LOW CONFIDENCE EXISTS
LATE MONDAY AFTERNOON WITH THE AMOUNT OF TRANSPARENCY TO MID TO HIGH
CLOUD PUSHING IN FROM THE NORTHWEST.
FOR DTW...FLURRIES POSSIBLE FOR AN HOUR OR TWO BEFORE CLEARING TREND
PUSHES IN FROM THE NORTH. MVFR CLOUD POSSIBLE LATE MONDAY MORNING.
DTW THRESHOLD PROBABILITIES...
* LOW FOR CEILING AT OR BELOW 5000 FT TONIGHT. MODERATE MONDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR LHZ421-
441>443.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...KGK
MARINE.......SF
AVIATION.....CB
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