501
FXUS63 KDTX 200259
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
959 PM EST THU DEC 19 2024
KEY MESSAGES
- A WINTER WEATHER ADVISORY IS IN EFFECT FOR MIDLAND AND BAY COUNTY
FOR TOTAL SNOW ACCUMULATIONS RANGING BETWEEN 3 TO 5 INCHES.
- ELSEWHERE, 1 TO 3 INCHES OF SNOW ACCUMULATION ARE EXPECTED BY
TOMORROW AFTERNOON. SNOW COVERED ROADS ARE LIKELY TO IMPACT THE
MORNING COMMUTE.
- LOCALLY HIGHER TOTALS TO OR IN EXCESS OF 4 INCHES ARE POSSIBLE
ALONG THE EASTERN THUMB DUE TO LAKE ENHANCEMENT OR BANDING.
- MUCH COLDER AIR MOVES IN FOR THE WEEKEND LIMITING DAYTIME
TEMPERATURES TO THE 20S WITH SINGLE DIGIT READINGS POSSIBLE AT
NIGHT.
UPDATE
LIGHT SNOW HAS LIFTED TO AREAS NORTH OF I 69 THIS EVENING, RELEGATED
TO THOSE AREAS EXPERIENCING ISENTROPIC LIFT ON THE 289-296KE SURFACES.
MIDLEVEL DRY AIR IN THE 800-700MB LAYER HAS BEEN HOLDING ON OVER THE
SOUTHERN FORECAST AREA AND WILL TAKE TIME TO SATURATE. FORECAST
REASONING ISSUED EARLIER TODAY PROVIDED GOOD DISCUSSION ON THIS DRY
AIR POTENTIAL. NO CHANGES ARE NEEDED TO THE FORECAST.
PREV DISCUSSION
ISSUED AT 629 PM EST THU DEC 19 2024
AVIATION...
CLIPPER LOW PRESSURE SYSTEM WILL BRING WIDESPREAD SNOW TO THE
SOUTHEAST MICHIGAN TERMINALS TONIGHT AND EARLY FRIDAY. LIGHT TO
OCCASIONALLY MODERATE SNOW IS EXPECTED TO RESULT IN PREVAILING IFR
CONDITIONS WITH SOME POTENTIAL FOR BRIEF LIFR AT KMBS AND KFNT.
SYNOPTIC PREVAILING SNOW WILL TRANSITION TO INTERMITTENT LAKE EFFECT
SNOW SHOWER BY LATE MORNING HOURS FRIDAY. EAST WINDS THIS EVENING
WILL VEER TO THE NORTHEAST AFTER 12Z FRIDAY.
FOR DTW...THE TERMINAL RESIDES JUST SOUTH OF EARLY SNOW FLURRY
ACTIVITY EARLY THIS EVENING. MOST LIKELY TIMEFRAME FOR PREVAILING
LIGHT SNOW WILL BE AFTER 08Z TONIGHT.
DTW THRESHOLD PROBABILITIES...
* HIGH FOR CEILING AT OR BELOW 5000 FEET THROUGH FRIDAY.
* HIGH FOR PRECIPITATION TYPE OF SNOW TONIGHT AND FRIDAY.
PREV DISCUSSION...
ISSUED AT 345 PM EST THU DEC 19 2024
DISCUSSION...
TEMPERATURES NOW RESIDE IN THE UPPER 20S TO LOWER 30S ACROSS SE MI
UNDER THE INFLUENCE OF A DIFFUSE HIGH PRESSURE SYSTEM WHICH HAS
PRODUCED DRY WEATHER THROUGH THE BULK OF THE DAY, OUTSIDE OF
SPORADIC FLURRY PRODUCTION. FOR THIS EVENING, ATTENTION WILL TURN TO
THE LOW PRESSURE SYSTEM NOW CENTERED OVER MN/IA, WHICH HAS AND WILL
CONTINUE TO PRODUCE WINTER IMPACTS ACROSS THE MIDWEST.
LIGHT SNOW WILL INITIALLY EXPAND ACROSS THE NORTHERN PORTION OF THE
CWA THIS EVENING, INITIALLY ALONG/NORTH OF I69, ALONG AN ARC OF LEAD
MID-LEVEL ISENTROPIC ASCENT, WITH ADDITIONAL AID FROM A WEAK
SHORTWAVE. LOW PRESSURE WILL TAKE ON A SOUTHEASTWARD PATH, CENTERING
OVER THE THE OHIO VALLEY BY FRIDAY MORNING, WHILE THE PARENT TROUGH
ORIENTS FROM A POSITIVE TILT TO NEUTRAL AS THE AXIS CROSSES OVER
MICHIGAN. THIS WILL SPUR MORE EFFICIENT ISENTROPIC ASCENT ACROSS THE
TRI-CITIES AND PORTIONS OF THE THUMB AND WILL EXPAND WEAKER LIFT
ACROSS LOCATIONS SOUTH THROUGH THE EARLY MORNING HOURS. MOIST
ISENTROPIC ASCENT REMAINS IN MOTION ACROSS ALL OF SE MI THROUGH THE
MID-MORNING HOURS, BEFORE THE LOW WASHES OUT INTO THE CAROLINAS BY
THE EARLY AFTERNOON, BACKING SYSTEM RELATIVE FLOW TO AN UNFAVORABLE
ORIENTATION ALONG THE ISENTROPIC SURFACE.
FOR MOST OF SE MI, HREF AND NBM ENSEMBLE SHOWCASE MEAN QPF VALUES OF
1-.25" BY THE EARLY AFTERNOON. SLRS AROUND 14:1 FOR THE EVENT PLACE
SNOW TOTALS AROUND 1.5 TO 3.5". THERE IS A SIGNAL FOR UNDER .1" QPF
SOUTH OF I-94, SO THE OUTGOING FORECAST WILL CAP SNOW TOTALS AROUND
AN INCH FOR THIS REGION. THE NORTHERN TRI-CITIES, PARTICULARLY BAY
AND MIDLAND COUNTIES AND THE FAR EASTERN THUMB ALONG HURON AND
SANILAC COUNTIES WILL BE AREAS OF CONCERN FOR POTENTIAL
OVERACHIEVEMENT OF SNOWFALL TOTALS. THERE WILL LIKELY BE LINEAR
INTENSE BANDING THAT WILL BE FUELED FROM INSTABILITY OVER LAKE HURON
THAT INITIALLY SETS UP INTO NORTHERN LOWER MICHIGAN THROUGH THE EARLY
MORNING HOURS. DEPARTURE OF THE AFOREMENTIONED LOW WILL BACK LOW-
LEVEL FLOW FROM THE SOUTHEAST TO NORTHEAST BY THE LATE MORNING TO
EARLY AFTERNOON WHICH HAS THE POTENTIAL TO RE-ORIENT THIS BAND INTO
THE TRI-CITIES, BRINGING A 1-3 HOUR WINDOW OF LOCALLY ENHANCED
SNOWFALL RATES IN EXCESS OF A HALF-INCH PER HOUR INTO THE EARLY
AFTERNOON. AS A RESULT, HAVE ISSUED A WINTER WEATHER ADVISORY FOR
BAY/MIDLAND GIVEN HIGHER CONFIDENCE TO SEE 4+ INCH ACCUMULATIONS. OF
MUCH LOWER CONFIDENCE, THERE IS A MODEST SIGNAL FOR LAKE ENHANCEMENT
OFF OF THE SOUTHERN BASIN OF LAKE HURON TO PRODUCE LOCALIZED HIGHER
TOTALS AROUND 4 INCHES ACROSS EASTERN HURON/SANILAC COUNTY BY FRIDAY
AFTERNOON, BUT CONFIDENCE IN THIS MATERIALIZING IS TOO LOW TO INCLUDE
IN ANY HEADLINES AT THIS TIME. FLOW WILL CONTINUE TO ORIENT NORTH-
NORTHWEST, BRINGING CONCERNS FOR LAKE EFFECT BANDING TO SET UP OVER
THE EASTERN HURON SHORELINE FRIDAY EVENING INTO SATURDAY MORNING.
OTHERWISE, THERE WILL BE A CHANCE TO SEE FLURRIES TO LIGHT LAKE
EFFECT SNOW SHOWERS THROUGH TOMORROW AFTERNOON AND EVENING WHERE AN
ADDITIONAL DUSTING TO HALF-INCH OF ACCUMULATION WILL BE POSSIBLE
FLOW DOES NOT TURN FAVORABLE FOR THE THUMB SHORELINE UNTIL TOMORROW
EVENING THROUGH SATURDAY MORNING, SO WILL PRECLUDE ANY HEADLINE
DECISIONS WITHIN THE THUMB GIVEN THE LONGER TIME OF ARRIVAL AND
LOWER CONFIDENCE FOR IF SNOWBANDS WILL CLIP THE SHORELINE OR STAY
JUST OFFSHORE. IF CLIPPED, BRIEF HOURLY SNOW RATES OF 1"/HR ARE NOT
OUT OF THE QUESTION FACTORING IN OVERLAKE CAPE VALUES >100J/KG,
ALLOWING CONVECTIVE DEPTHS TO PUSH ABOVE 10KFT. HREF MAINTAINS
AROUND A 30% PROBABILITY TO SEE SNOW TOTALS IN EXCESS OF 3" BY 12Z
SAT. SUBTLE CONTINUED BACKING WITH DECREASE CONCERNS FOR LAKE BANDING
BY THE LATE MORNING HOURS.
PASSAGE OF THE LOW WILL INITIATE CAA THROUGH FRIDAY AND SATURDAY,
BRINGING BELOW NORMAL TEMPERATURES BY THE WEEKEND WITH HIGHS IN THE
20S. THE COLDEST TEMPERATURES WILL BE FELT SUNDAY MORNING WHERE LOWS
DIP INTO THE SINGLE DIGITS. VERY DRY AIR WILL ACCOMPANY THE BELOW
NORMAL TEMPERATURES, BRINGING AN UNFAVORABLE ENVIRONMENT FOR LAKE
EFFECT SNOW CHANCES. PERIODS OF EXTENDED SUNSHINE WILL BE POSSIBLE
FOR PORTIONS OF THE WEEKEND.
MARINE...
EASTERLY FLOW STRENGTHENS TO BETWEEN 15-20KTS THROUGH THE NIGHT AS A
CLIPPER SYSTEM DROPS OUT OF THE UPPER MIDWEST INTO NORTH-CENTRAL
INDIANA/OHIO. WIDESPREAD SNOW SHOWERS ARE LIKELY DURING THIS
TIMEFRAME AND WILL LINGER INTO THE EARLY PART OF FRIDAY. LOW CENTER
REACHES THE EASTERN OHIO VALLEY LATTER HALF OF THE DAY FRIDAY
SETTING UP NORTHERLY FLOW IN ITS WAKE AND TAPERING OFF MOST SNOW
SHOWERS, SAVE FOR SOME POSSIBLE LAKE EFFECT IN SOUTHERN HURON.
GRADIENT IS NOT EXPECTED TO BE STRONG ENOUGH TO SUPPORT HEADLINE
WINDS, INSTEAD GUSTS BETWEEN 20-25KTS ARE MOST FAVORED- STRONGEST IN
THE SOUTHERN BASIN OF LAKE HURON. SMALL CRAFT ADVISORIES HAVE BEEN
ISSUED FOR THE THUMB NEARSHORE WATERS LATE FRIDAY INTO SATURDAY DUE
TO ONSHORE WINDS DRAWING IN HIGHER WAVE ACTION. HIGH PRESSURE THEN
BUILDS ACROSS THE GREAT LAKES THIS WEEKEND SUPPORTING DRIER
CONDITIONS AND LIGHTER WINDS.
DTX WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY UNTIL 5 PM EST FRIDAY FOR MIZ047-048.
LAKE HURON...SMALL CRAFT ADVISORY FROM 10 AM FRIDAY TO 10 PM EST SATURDAY FOR
LHZ421-441>443.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
UPDATE.......CB
AVIATION.....CB
DISCUSSION...AM
MARINE.......KDK
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AT WWW.WEATHER.GOV/DETROIT.
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