439
FXUS63 KDTX 172048
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
348 PM EST FRI JAN 17 2025
KEY MESSAGES
- WIDESPREAD RAIN/SNOW TO SNOW EXPECTED TONIGHT INTO SATURDAY
MORNING. SNOW ACCUMULATION TOTALS OF A HALF-INCH UP TO 2 INCHES
LIKELY, WITH HIGHER-END AMOUNTS POSSIBLE WITHIN THE IRISH HILLS.
- THE COLDEST TEMPERATURES OF THE WINTER THUS FAR ARRIVE EARLY NEXT
WEEK. DANGEROUS WIND CHILLS OF -15 TO -25 LIKELY FOR THE MORNING
HOURS, WITH LITTLE RELIEF FOR THE AFTERNOON, CENTERED MONDAY THROUGH
WEDNESDAY.
DISCUSSION
SHORTWAVE RIDGE AXIS PASSED TO OUR EAST THIS MORNING OPENING THE
DOOR FOR GUSTY SOUTHWESTERLY WINDS AROUND THE BROAD SURFACE HIGH
PRESSURE CENTERED OVER THE EASTERN CONUS. GUSTS TO 30 KNOTS HAVE
HELPED USHER A FAIRLY WARM AIRMASS INTO THE REGION THIS AFTERNOON,
AND AIDED BY PEAKS OF SUN, HAS RESULTED IN TEMPS INTO THE UPPER 30S
ACROSS SOUTHEAST MI. THIS WARM AIR WILL BE SHORT LIVED AS A STRONG
LOW TRACKING THROUGH SOUTHERN CANADA TONIGHT WILL OPEN THE DOOR FOR
LONG DURATION COLD AIR ADVECTION WITH MULTIPLE SURGES OF ARCTIC AIR
THROUGH THE REGION AS THE LONGWAVE TROUGH STALLS AND DIGS DOWN TO
THE GULF INTO THE MIDWEEK PERIOD. THIS WILL BE ONE OF THE COLDEST
AIRMASSES WE'VE EXPERIENCED IN THE LAST FEW YEARS.
FOR TONIGHT, THE LOW PRESSURE SYSTEM WILL PASS THROUGH ONTARIO
TONIGHT, PULLING AN ARCTIC COLD FRONT THROUGH SE MI SATURDAY
MORNING. AS THIS NORTHERN STREAM TROUGH DIGS SOUTHWARD THROUGH THE
MS VALLEY IT WILL PARTIALLY PHASE WITH THE SOUTHERN STREAM AND A
SHORTWAVE TRACKING THROUGH OK/MO. A STRONG LOW LEVEL JET AHEAD OF
THE DEEPENING TROUGH WILL PEAK AROUND 60 KNOTS TONIGHT OVER SOUTHERN
MI AND IS ALREADY CLOSING IN ON 40 KNOTS HELPING TO GENERATE THE
GUSTS THIS AFTERNOON. THIS WILL ALSO BRING A SURGE OF MOISTURE UP
INTO THE AREA JUST AHEAD OF THE ARCTIC FRONT RESULTING IN SEVERAL
HOURS OF PRECIPITATION TONIGHT INTO SATURDAY MORNING. MODELS HAVE
BEEN FAIRLY CONSISTENT WITH AROUND 0.25 INCHES OF QPF, BUT THE PTYPE
WILL BE AN ISSUE WITH THIS EVENT. STARTING OFF NEAR 40 THIS EVENING,
WITH TEMPS ABOVE 32F UP THROUGH 6KFT WILL OFFER THE INITIAL PTYPE
ISSUE WITH TOO MUCH WARM AIR AT ONSET AROUND MIDNIGHT. SO FIRST FEW
HOURS WILL BE RAIN OR A RAIN SNOW MIX WORKING SOUTH TO NORTH THROUGH
THE REGION. WARM LAYER GRADUALLY COOLS THROUGH THE NIGHT WITH
SOUNDING FAVORING COLDER PROFILES AFTER ABOUT 5AM WHICH WOULD OFFER
MORE SNOW, OR MELTING SNOW, FOR MUCH OF THE AREA ESPECIALLY THE
HIGHER TERRAIN OF THE IRISH HILLS. LOWER TERRAIN FROM MONROE COUNTY
UP THROUGH WAYNE AND INTO MACOMB ARE EXPECTED TO HOLD THE WARM AIR
LONGER. TEMPS MOST OF THE NIGHT WILL RESIDE IN THE LOW TO MID 30S
ALSO HELPING TO REDUCE SNOW ACCUMULATION. NAM IS DEFINITELY ONE OF
THE COLDER MODELS WHICH ISN'T SURPRISING WITH HRRR AND RAP COMING IN
MUCH WARMER, KEEPING RAIN ALMOST THROUGH 12Z SAT. SO WITH SUCH A
FINE LINE BETWEEN RAIN AND SNOW IN THESE SCENARIOS, WILL HOLD WITH A
MAINLY 1-2 INCH FORECAST FOR A PORTION OF THE AREA WITH 3 INCHES NOT
OUT OF THE QUESTIONS IF THE COLD AIR CAN SURGE IN FASTER AND MAINLY
FOR THE IRISH HILLS. WITH WARM TEMPERATURES HOLDING AT THE SURFACE,
ANY ACCUMULATION WILL LIKELY BE MINIMIZED ON PAVED SURFACES THAT ARE
WET TO START AND WARM AT TRANSITION. SO HIGHER ACCUMULATIONS
EXPECTED ON GRASS OR ELEVATED SURFACES.
WITH THE ARCTIC FRONT SWEEPING ACROSS SATURDAY MORNING, THE MOISTURE
AND WARM AIR WILL ALL GET SHUNTED EAST WITH COLD AIR ADVECTION
KICKING IN. SOME LINGERING LIGHT SNOW IN THE MORNING WILL BE
POSSIBLE UNTIL THE FRONT FINALLY PASSES BUT DRIER AIR WILL END THAT
BY NOON. WARMEST TEMPS WILL BE EARLY IN THE MORNING WITH TEMPS THEN
FALLING THROUGH THE DAY. AFTER INCREASING TO AROUND +4C FRIDAY
EVENING, 850MB TEMPS WILL FALL TO AROUND -4C BY SATURDAY MORNING AND
-10C BY EVENING. AFTER FALLING FURTHER TO AROUND -20C BY SUNDAY
AFTERNOON, ECMWF SUGGESTS -25C IS IN PLAY FOR MONDAY WITH THE
COLDEST AIRMASS SWEEPING THROUGH TUESDAY CLOSE TO -30C. EXPECT A
LONG DURATION COLD OUTBREAK WITH TEMPERATURES HOLDING BELOW 20F FROM
SATURDAY NIGHT THROUGH WEDNESDAY NIGHT WITH HIGHS ON TUESDAY AND
WEDNESDAY IN THE SINGLE DIGITS. WIND CHILL VALUES WILL FALL INTO THE
NEGATIVE RANGE SUNDAY NIGHT AND WILL REMAIN BELOW ZERO THROUGH
WEDNESDAY NIGHT. AT THIS TIME THEY LOOK TO BOTTOM OUT IN THE -10 TO -
20F RANGE WHICH WILL NEED TO BE WATCHED AS WE REFINE THINGS. LOOKS
LIKELY THAT WE WILL NEED A COLD WEATHER ADVISORY FOR A PERIOD THIS
WEEK AT A MINIMUM.
MARINE
A STRONG LOW PRESSURE SYSTEM TRACKING NORTH OF LAKE SUPERIOR IS
SETTING UP A CORRIDOR OF STRONG SOUTHERLY WINDS OVER THE CENTRAL
GREAT LAKES THIS AFTERNOON. THESE WINDS REACH A PEAK IN MAGNITUDE
THIS EVENING WITH GUSTS OF 35 TO 40 KNOTS OVER CENTRAL/SOUTHERN LAKE
HURON. A GALE WARNING REMAINS IN EFFECT THERE THROUGH TONIGHT.
ELSEWHERE, WINDS WILL BE MAINLY IN THE 20 TO 30 KNOT RANGE. GALES
WILL TAPER OFF EARLY SATURDAY MORNING AS THE SYSTEM'S COLD FRONT
SLIDES THROUGH. THIS WILL BE FOLLOWED BY NORTHWEST WINDS PICKING UP
AS COLD ADVECTION ENSUES. THESE PEAK BETWEEN 20 AND 30 KNOTS
SATURDAY AFTERNOON BUT REMAIN ACTIVE THROUGH THE WEEKEND AS FRIGID
ARCTIC AIR WORKS INTO THE REGION. INTERVALS OF LAKE EFFECT SNOW
SHOWERS AND FREEZING SPRAY CAN BE EXPECTED OVER LAKE HURON SUNDAY
THROUGH WEDNESDAY.
PREV DISCUSSION
ISSUED AT 1243 PM EST FRI JAN 17 2025
AVIATION...
DRY AIR MASS BETWEEN THE SURFACE AND 15.0 KFT AGL WILL ENSURE VFR
CONDITIONS THROUGH THIS EVENING. WILL BE AMENDING SHORTLY FOR NON
CONVECTIVE LOW LEVEL WIND SHEAR THIS EVENING. AN AREA OF
FRONTOGENESIS WILL CLIP SOUTHEAST MICHIGAN LATE TONIGHT AND EARLY
SATURDAY. ABRUPT BOTTOM UP SATURATION WITH SURFACE TEMPERATURES
AT/ABOVE FREEZING WILL ALLOW FOR A RAIN SNOW MIX TO BEGIN AFTER 06Z.
STEADY PRECIPITATION RATES WILL EVENTUALLY ALLOW PRECIPITATION TO
CHANGEOVER TO ALL SNOW AFTER 10Z SATURDAY BEFORE ENDING AFTER 18Z
SATURDAY. MVFR TO IFR CONDITIONS IN FALLING SNOW IS EXPECTED WITH
SOME BRIEF AND VERY SHORT DURATION LIFR POSSIBLE AT THE DETROIT
TERMINALS AROUND DAYBREAK SATURDAY. LOW VFR TO MVFR STRATUS IS
EXPECTED
DTW THRESHOLD PROBABILITIES...
* LOW FOR CEILING AOB 5000 FEET TODAY. HIGH AFTER 06Z TONIGHT.
* MEDIUM FOR A PRECIPITATION TYPE OF RAIN AND MELTING SNOW AT
ONSET AFTER 06Z TONIGHT. HIGH FOR ALL SNOW POST FRONT LATE
TONIGHT INTO SATURDAY MORNING.
* LOW FOR CROSSWIND THRESHOLD EXCEEDENCE SATURDAY AFTERNOON.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 4 AM EST SATURDAY FOR LHZ362-363-421-441-462>464.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...DRK
MARINE.......TF
AVIATION.....CB
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