814
FXUS63 KDTX 201804
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
104 PM EST FRI DEC 20 2024
KEY MESSAGES
- A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE SAGINAW VALLEY UNTIL
5 PM AND EASTERN THUMB UNTIL 10 PM.
- WIDESPREAD SNOW TAPERS OFF THIS AFTERNOON AS HEAVIER SNOW SHOWERS
BECOME MORE LAKE INFLUENCED AND FOCUSED ACROSS THE THUMB INTO THE
EVENING.
- COLD THIS WEEKEND WITH DAYTIME TEMPERATURES IN THE 20S AND MORNING
LOWS IN THE TEENS AND SINGLE DIGITS.
- NEXT CHANCE OF SNOW AND RAIN ARRIVES ON MONDAY.
AVIATION
CLIPPER SYSTEM PASSING FURTHER TO THE SOUTH IS LEADING TO REDUCTION
OF WIDESPREAD SNOW AS MVFR/IFR CONDITIONS LINGER. NORTH/NORTHEAST
FLOW OFF LAKE HURON WILL SUPPORT MAINLY LIGHT SNOW SHOWERS FOR THE
NEXT FEW HOURS AS MORE CONCENTRATED LAKE EFFECT SNOW SHOWERS BECOMES
MORE DOMINATE AND FOCUSED NORTH AND EAST OF THE TERMINALS INTO THE
LATE AFTERNOON. THIS WILL LARGELY BRING AN END TO SNOW SHOWERS
ACROSS TERMINALS BY THIS EVENING. AS DRY AIR FILTERS INTO THE
REGION, CIGS/VSBYS BEGIN TO IMPROVE INTO TONIGHT, BUT COULD STILL
SEE PERIODS OF MVFR CEILINGS AS WINDS HOLD OUT OF THE NORTH. WIND
SPEEDS WILL TOP OUT BETWEEN 10-15 KNOTS THROUGH THE REST OF TODAY,
THOUGH THERE WILL BE GUSTS TO AROUND 20 KNOTS ACROSS KMBS COMING OFF
THE BAY. SUBTLE WIND SHIFT TO THE NORTHWEST TOMORROW MORNING
WILL BRING POTENTIAL FOR FURTHER CEILING IMPROVEMENT.
FOR DTW...LIGHT SNOW SHOWERS WILL BECOME MORE INTERMITTENT THROUGH
THE AFTERNOON AS ACTIVITY BECOMES MORE LAKE INFLUENCED WITH ACTIVITY
MORE LIKELY COMING TO AN END BY 21-22Z. NORTHERLY WINDS WILL
MAINTAIN MVFR TO IFR CEILINGS WITH SOME IMPROVEMENTS TO VFR WITH
PERIODS OF MVFR TONIGHT INTO TOMORROW MORNING.
DTW THRESHOLD PROBABILITIES...
* HIGH FOR CEILING AT OR BELOW 5000 FEET THROUGH TONIGHT.
* HIGH FOR PRECIPITATION TYPE OF SNOW TODAY.
PREV DISCUSSION
ISSUED AT 1025 AM EST FRI DEC 20 2024
UPDATE...
MID-MORNING SNOW TOTALS AS OF 7-9 AM RANGE BETWEEN 1-3 INCHES ACROSS
MOST OF SE MI, OUTSIDE OF LOWER AMOUNTS BELOW AN INCH ACROSS THE
METRO DETROIT AREA AND LOCATIONS AROUND AND SOUTH OF I-94. THE MORE
WIDESPREAD LIGHT SNOW COVERAGE WILL WANE THROUGH THE MORNING HOURS AS
FORCING TRANSITIONS FROM ISENTROPICALLY INDUCED TO LAKE EFFECT
DRIVEN LEADING INTO THE AFTERNOON HOURS. LAKE EFFECT MOISTURE WILL BE
DRIVEN PRIMARILY FROM LAKE HURON, THUS SOME BETTER COVERAGE OF SNOW
REMAINS POSSIBLE THROUGH THE TRI-CITIES AND THUMB, WITH MORE ISOLATED
TO SCATTERED COVERAGE FOR LOCATIONS SOUTH. THE MAIN CONCERN THROUGH
THE AFTERNOON AND EVENING HOURS WILL BE CENTERED OVER THE TRI-CITIES
AND THUMB, WHERE WINTER WEATHER ADVISORIES (WWA) REMAIN IN PLACE.
BACKED FLOW TO THE NE WILL BE ABLE TO CAPITALIZE ON THE OVERLAKE
INSTABILITY, SUPPORT EL LEVELS THROUGH 15KFT WHICH WILL BE WELL
SATURATED WRT ICE. THIS BRING THE CHANCE TO SEE AN ADDITIONAL QUICK
1-2 INCHES OF HIGHLY LOCALIZED ACCUMULATION IN A 1-3 HOUR WINDOW,
PENDING WHERE ANY SNOW BANDS SET UP. THIS WINDOW WILL FALL BETWEEN
11AM-3PM ACROSS THE TRI-CITIES. CONTINUED BACK FLOW THEN TRANSITIONS
THIS WINDOW FOR ELEVATED SNOW RATES INTO THE NORTHERN THUMB INTO THE
EARLY AFTERNOON WITH A POSSIBLE EXTENSION DOWN THROUGH THE LAKESHORE
INTO PORT HURON THROUGH THE EVENING HOURS IN THE 6PM TO 10PM TIME
FRAME. FOR LOCATIONS OUTSIDE OF THE WWA, ISOLATED TO SCATTERED
ACTIVITY WILL BE CAPABLE OF PRODUCING A QUICK DUSTING UP TO A HALF-
INCH TO INCH IN A HIGH END SCENARIO THIS AFTERNOON AND EARLY EVENING.
THERE REMAINS LOWER- END CHANCES THAT LAKE EFFECT BANDS CAN
CONTINUE TO IMPACT THE SHORELINE BEYOND 10PM THROUGH TOMORROW
MORNING, WHICH WILL BE ASSESSED AS NEW MODEL GUIDANCE COMES IN THIS
MORNING.
PREV DISCUSSION...
ISSUED AT 337 AM EST FRI DEC 20 2024
DISCUSSION...
MID-LEVEL TROUGH OVER THE GREAT LAKES IS TAKING ON A NEUTRAL TILT
THIS MORNING AS A POTENT VORT MAX DIGS ACROSS THE OHIO VALLEY WITH A
NWRLY 140+ KT JET STREAK ARRIVING ACROSS THE UPPER MIDWEST. THE
SURFACE LOW WILL TREK SW FROM CHICAGO THIS MORNING INTO WV BY AROUND
NOON. THIS ALLOWS AN AREA OF MODEST BUT PROLONGED ISENTROPIC ASCENT
TO CONTINUE TO PIVOT OVER LOWER MI THROUGH THE MORNING, RESULTING IN
WIDESPREAD LIGHT TO AT TIMES MODERATE SNOWFALL. SYSTEM RELATIVE
STREAMLINES SHOW FLOW BECOMING MORE PARALLEL TO ISENTROPES THIS
AFTERNOON WHICH WILL CAUSE RATES TO WIND DOWN THROUGH THE DAY FOR
THE MAJORITY OF THE AREA. AN ADDITIONAL 2 TO 3 INCHES OF SNOWFALL
CAN BE EXPECTED THROUGH MIDDAY FOR AREAS NORTH OF I-69 BEFORE THE
MORE WIDESPREAD SNOW TAPERS OFF. LOCALIZED TOTALS UP TO 4 INCHES
WILL BE POSSIBLE ACROSS THE EASTERN THUMB WHERE EASTERLY FLOW ACROSS
LAKE HURON IS LEADING TO LAKE ENHANCEMENT AND HIGHER RATES. OPTED TO
EXPAND THE WINTER WEATHER ADVISORY INTO THE THUMB WHERE THESE TOTALS
BRING HIGHER CONFIDENCE IN TRAVEL IMPACTS THIS MORNING. SOUTH OF THE
ADVISORY, ADDITIONAL TOTALS ON THE ORDER OF 0.5 TO 2 INCHES ARE MORE
LIKELY THROUGH MIDDAY WITH SLICK SPOTS LIKELY ON ANY UNTREATED ROADS
THROUGH THE MORNING COMMUTE.
A MORE ORGANIZED BAND OF LAKE EFFECT SNOW HAS BEEN APPARENT ON CASET
AND KAPX RADARS OVERNIGHT, MAINLY DIRECTED NW AND AWAY FROM THE
THUMB SHORELINE. THIS WILL CHANGE AS THE LOW SLIDES SOUTH TODAY,
CAUSING FLOW TO QUICKLY BACK FROM EASTERLY TO NORTHERLY BY THIS
EVENING. IF THIS BANDING CAN HOLD TOGETHER THROUGH THE DAY, IT WILL
PIVOT SOUTHWARD ACROSS SAGINAW BAY AND INTO THE THUMB THROUGH THE
EVENING HOURS. WOULD EXPECT EXCELLENT MICROPHYSICS AND VERY HIGH
SLRS IN ANY OF THIS LAKE EFFECT AS AVAILABLE SOUNDINGS SHOW AN OMEGA
BULLSEYE VERY NEAR OR WITHIN THE SUPERSATURATED DGZ, COINCIDENT WITH
UPRIGHT INSTABILITY CHARACTERIZED BY CAPE OF 50 TOO 100 J/KG AND
CONVECTIVE DEPTHS OF UP TO 10 KFT AGL. THIS WOULD FAVOR A VERY
FLUFFY SNOW TYPE AND RATES IN EXCESS OF 1"/HR. THE LIMITING FACTOR
FOR HIGHER TOTALS WILL BE RELATIVELY SHORT RESIDENCE TIME FOR ANY
ONE LOCATION AS THE BAND PROGRESSES SOUTH, BUT A QUICK ADDITIONAL 1
TO 3 INCHES WILL BE POSSIBLE. THE BULK OF THIS ACTIVITY WILL OCCUR
BETWEEN 1PM (SAGINAW BAY AREA) AND 10PM (PORT HURON AREA). THE
WINTER WEATHER ADVISORY WILL ENCOMPASS THIS TIME PERIOD TO ACCOUNT
FOR THE AFTERNOON/EVENING BANDING AS WELL AS THIS MORNING'S SNOWFALL.
WIND TRAJECTORIES WILL CONTINUE TO BACK TO NW LATE THIS EVENING
WHICH WILL USHER IN A MUCH DRIER AIR MASS AND FORCE THE BULK OF THE
LAKE EFFECT BAND OFFSHORE. HI-RES GUIDANCE ADVERTISES VEERED NNW TO
N FLOW BEING MAINTAINED OVER LAKE HURON WHICH DOES KEEP THE BAND IN
CLOSE PROXIMITY - OFFERING ANOTHER CHANCE FOR THE EASTERN THUMB TO
GET CLIPPED EARLY SATURDAY MORNING. OTHERWISE ARCTIC HIGH PRESSURE
BUILDS INTO THE AREA THROUGH THE DAY SATURDAY PROMOTING MAINLY DRY
BUT COLD CONDITIONS WITH HIGHS IN THE 20S. POCKETS OF SATURATION
RESIDING IN THE DGZ AT THE TOP OF THE MIXED LAYER MAY BE ENOUGH TO
GENERATE OCCASIONAL FLURRIES THROUGHOUT THE DAY. VERY COLD
CONDITIONS EXPECTED SATURDAY NIGHT INTO SUNDAY MORNING WITH LOWS
DIPPING INTO THE SINGLE DIGITS. A LACK OF WIND WILL HOLD WIND CHILLS
NEAR THE ACTUAL AIR TEMP.
THE HIGH SLIDES EAST ON SUNDAY BUT CONTINUES TO DOMINATE THE
FORECAST WITH DRY CONDITIONS FAVORED. HIGHS WILL AGAIN ONLY REACH
THE 20S BUT BURGEONING SOUTH WIND WILL INDUCE A THICKNESS ADVECTION
PATTERN TO SET THE STAGE FOR A MILDER DAY ON MONDAY. THE NEXT WAVE
WITHIN THE ACTIVE NORTHWEST FLOW PATTERN ALOFT WILL BRING THE NEXT
CLIPPER TO THE REGION ON MONDAY. A FARTHER NORTH TRACK WITH THIS
SYSTEM COMPARED TO TODAY'S WILL PLACE THE BULK OF THE ISENTROPIC
ASCENT AND DEFORMATION SNOW TO OUR NORTH, BUT PRECIP BECOMES
INCREASINGLY LIKELY DURING THE DAYLIGHT HOURS AS MOISTURE TRANSPORT
RIDES IN AHEAD OF THE LOW. THE WARM FRONT LOOKS TO SEND TEMPERATURES
INTO THE MID 30S WHICH FAVORS A TRANSITION TO A RAIN/SNOW MIX OR
POSSIBLY JUST RAIN ACROSS THE SOUTH. NEUTRAL TEMPERATURE ADVECTION
BEHIND THIS SYSTEM WILL MAINTAIN SEASONABLE CONDITIONS THROUGH THE
MID-WEEK PERIOD.
MARINE...
SNOW SHOWERS PERSIST MAINLY OVER THE SOUTHERN HALF OF THE REGION
THIS MORNING AS LOW PRESSURE DROPS TOWARDS THE EASTERN OHIO VALLEY.
LIKEWISE AS A RESULT, WINDS STEADILY TURN FROM E TO NE AND
EVENTUALLY N BY THIS EVENING. STRONGEST WINDS CAN BE EXPECTED OVER
THE SOUTHERN BASIN OF LAKE HURON WHERE GUSTS WILL BE ABLE TO REACH
20-25KTS. LESSER WINDS, 15-20KTS, LIKELY OVER THE REST OF THE
REGION. SMALL CRAFT ADVISORIES REMAIN IN EFFECT THROUGH SATURDAY
EVENING AROUND THE THUMB NEARSHORE WATERS DUE TO THIS ONSHORE FLOW
AND SUBSEQUENT HIGHER WAVE ACTION. ARCTIC HIGH PRESSURE EXPANDS OVER
THE CENTRAL GREAT LAKES THIS WEEKEND BRINGING COLDER, BUT DRIER AND
CALMER CONDITIONS.
DTX WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR MIZ047-
048-053-054.
WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR MIZ049-055-
063.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 PM EST SATURDAY FOR LHZ421-441>443.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....AA
UPDATE.......AM
DISCUSSION...TF
MARINE.......KDK
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AT WWW.WEATHER.GOV/DETROIT.
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