018
FXUS63 KDTX 160837
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
337 AM EST THU JAN 16 2025
KEY MESSAGES
- LIGHT SNOW WORKS ACROSS THE AREA THROUGH THIS AFTERNOON.
ACCUMULATIONS BETWEEN A HALF INCH TO 2 INCHES POSSIBLE. HIGHEST
AMOUNTS ARE EXPECTED IN THE THUMB.
- WIDESPREAD PRECIPITATION LIKELY EARLY SATURDAY. THERE IS STILL
UNCERTAINTY HOW MUCH RAIN MIXES IN WITH SNOW. 1 TO 3 INCHES
CURRENTLY FORECAST, WITH HIGHEST TOTALS OVER THE THUMB AND EASTERN I-
69/M-59 CORRIDORS.
- ARCTIC AIR IS EXPECTED ACROSS SOUTHEAST MICHIGAN SUNDAY THROUGH
WEDNESDAY.
- OVERNIGHT LOWS WILL DROP BELOW ZERO DEGREES WITH WIND CHILLS
FALLING BELOW -15 F, OR LOWER, EACH MORNING. HIGH TEMPERATURES ONLY
IN THE SINGLE DIGITS MONDAY AND TUESDAY.
DISCUSSION
LIGHT SNOW HAS BEGUN TO OVERSPREAD THE AREA AT TIME OF DISCUSSION
TIED TO A WEAK CLIPPER DROPPING THOUGH THE GREAT LAKES. PEAK RATES,
UP TO AROUND 0.1"/HR, OCCUR BETWEEN NOW AND 8AM AS THE PRIMARY VORT
MAX AND BASE OF THE MID-LEVEL TROUGH SWING OVER THE AREA. PRIOR
FORECAST STILL LOOKING ON TRACK WITH NO SIGNIFICANT ADJUSTMENTS MADE
TO THE SNOW TOTALS; THAT IS, AN INCH OR TWO MAINLY EAST OF I-75/US-
23 WITH TOTALS TO THE WEST AROUND AN INCH. THIS WAVE PUSHES TO OUR
EAST BY ~15Z FOLLOWED BY A TRAILING PARTIALLY SHEARED LOBE OF
VORTICITY ON THE BACKEDGE OF THE TROUGH CROSSING THE AREA THIS
AFTERNOON. DESPITE THE SHEARED NATURE OF THE WAVE AND DECREASING
UPPER SUPPORT AS GEOPOTENTIAL HEIGHTS BEGIN TO RISE, STEEPENING LOW
LEVEL LAPSE RATES AND TRAILING EDGE OF ENHANCED MID-LEVEL LAPSE
RATES FROM THE EARLY WAVE DO YIELD A SECONDARY BURST OF SCATTERED
LIGHT SNOW SHOWERS IN SEVERAL MODEL SOLUTIONS, PARTICULARLY THE NAM.
GIVEN THE WEAKER FORCING AND MEDIOCRE MOISTURE, ANY ADDITIONAL
ACCUMULATIONS LIKELY ONLY A TENTH OR TWO AT BEST.
LOW AMPLITUDE RIDGING EXPANDS OVER THE CENTRAL GREAT LAKES LATE
TONIGHT SETTING UP DEEPER LAYER SW RETURN FLOW INTO LOWER MI.
DEEPENING LOW PRESSURE TRAVERSING JUST NORTH OF LAKE SUPERIOR LEADS
TO RAPID DEVELOPMENT OF A 850-900MB LLJ INTO THE REGION WITH FLOW
EVENTUALLY REACHING 50-55KT DOWN TO AROUND 925MB. THIS STRONG JET
SUPPORTS ROBUST WAA INTO THE AREA WITH 850MB TEMPS RISING TO +2C BY
LATE FRIDAY AFTERNOON (UP FROM -10C TONIGHT) AS HIGHS REACH BACK
NEAR NORMAL IN THE LOWER 30S. BREEZY CONDITIONS CAN ALSO BE EXPECTED
WITH GUSTS LATTER HALF OF FRIDAY BETWEEN 25-30MPH.
ATTENTION THEN TURNS TO AN ARCTIC COLD FRONT DRAWN SOUTH BY THE
AFOREMENTIONED NORTHERN ONTARIO LOW FRIDAY NIGHT-SATURDAY MORNING.
ENSEMBLE AND DETERMINISTIC GUIDANCE CONTINUE TO SHOW FAVORABLE
PHASING TIMING/POSITIONING BETWEEN THE NORTHERN STREAM TROUGH AND A
SOUTHERN SHORTWAVE LIFTING OUT OF THE SOUTHERN PLAINS. THAT ALLOWS
SOUTHERN STREAM VORTICITY TO LIFT OVER SE MI SATURDAY MORNING AS THE
SURFACE ARCTIC FRONT AND ITS ATTENDANT PV ANOMALY PUSH INTO WEST MI.
HIGH CONFIDENCE IN WIDESPREAD PRECIP OVER THE REGION SATURDAY
MORNING INCLUDING AT LEAST SOME ACCUMULATING SNOW, THOUGH EXACTLY
HOW MUCH IS REMAINS THE MAIN POINT OF UNCERTAINTY. THIS COMES DOWN
TO THE SPEED OF COLD ADVECTION INTO SE MI FROM THE NORTHERN TROUGH
THAT IS BEGINNING TO SLIDE OVERHEAD AS SOUTHERN STREAM SHORTWAVE
ARRIVES. CURRENTLY THE FAVORED SCENARIO IS FOR AN INITIAL RAIN-SNOW
MIX (BETWEEN ~06-12Z) FOR AREAS OUTSIDE THE THUMB/NORTHERN PORTION
OF THE GLACIAL MORAINE (NORTH OF M-59) AS NEAR-SURFACE LAYER TEMPS
HOVER 32-34F. FORECAST SOUNDINGS FOR THE EXCEPTION AREAS, DUE TO
MORE SNOW DEPTH AND TERRAIN EFFECTS FOR THE MORAINE, ADVERTISE
SURFACE TEMPS 31-32F AND COLD COLUMNS TO SUPPORT ALL SNOW (OR AT
VERY LEAST MINIMAL RAIN MIX). CONTINUED COLD ADVECTION THEN SHOULD
FACILITY A TRANSITION TO MOSTLY/ALL SNOW FOR THE REST OF THE AREA
MID TO LATE MORNING. ENSEMBLE AND DETERMINISTIC MODEL FAMILIES IN
FAIRLY GOOD AGREEMENT WITH BOTH THE OVERALL QPF BEING BETWEEN 0.1-
0.3" AND THE BULK OF THAT FALLING DURING THE 06-12Z WINDOW BEFORE
THE ARCTIC COLD FRONT THEN DRIVES ACROSS THE REGION LATE MORNING-
EARLY AFTERNOON SHUNTING PRECIP TO OUR EAST. DUE TO THIS, THE
HIGHEST ACCUMULATIONS ARE CURRENTLY FORECAST OVER THE THUMB AND
EASTERN I-69/M-59 CORRIDORS (EAST OF I-75/US-23) WHERE 1-3" ARE
POSSIBLE. THE REST OF THE REGION ARE FORECAST TO SEE 0.5-1.5". THESE
TOTALS ARE HIGHLY SENSITIVE TO ANY CHANGES IN THE TEMPERATURE
FORECAST HOWEVER, GIVEN THE NEAR FREEZING SETUP, SO EXPECT FURTHER
ADJUSTMENTS AS WE GET CLOSER.
TEMPERATURES RAPIDLY DROP FOLLOWING THE ARCTIC FRONT GOING FROM
AROUND 32F SAT MORNING TO AROUND 20F BY SAT EVENING, AND EVENTUALLY
OVERNIGHT LOWS UPPER SINGLE DIGITS/LOWER TEENS. GIVEN THE WETTER
NATURE OF THE EARLY DAY SNOW, IT WILL QUICKLY TURN ICY. COLDEST AIR
OF THE WINTER THUS FAR THEN SETTLES OVER THE CENTRAL CONUS SUNDAY
THROUGH THE FIRST HALF OF NEXT WEEK AS LOCAL 850MB TEMPS FALL TO
AROUND -25C. HIGHS ONLY IN THE TEENS SUNDAY AND WEDNESDAY WITH THE
COLDEST DAYS BEING MONDAY AND TUESDAY WHERE SINGLE DIGIT HIGHS ARE
LIKELY. WIND CHILLS (AND OVERNIGHT LOWS) THROUGHOUT THIS PERIOD ARE
FAVORED TO REMAIN BELOW ZERO WITH -15 TO -20F APPARENT TEMPS
POSSIBLE MON/TUES WHICH WOULD EASILY MEET COLD WEATHER ADVISORY
CRITERIA.
MARINE
A WEAK CLIPPER SYSTEM WILL TRACK SOUTHEAST ACROSS THE GREAT LAKES
TODAY, BRINGING WIDESPREAD LIGHT SNOWFALL. SOUTHWEST WINDS AHEAD OF
THIS SYSTEM WILL BE GUSTY EARLY THIS MORNING, MAINLY IN THE 20 TO 25
KNOT RANGE BUT OCCASIONALLY REACHING 30 KNOTS WHERE FETCH IS
MAXIMIZED DOWN SAGINAW BAY INTO CENTRAL LAKE HURON. WINDS WEAKEN
THROUGH MIDDAY AS THE SURFACE TROUGH EASES INTO THE AREA, THEN WIND
DIRECTION SHIFTS TO THE NORTHWEST TONIGHT AND INCREASES TO THE 20 TO
25 KNOT RANGE AGAIN. A BRIEF LULL IN WIND MAGNITUDE FOLLOWS BETWEEN
SYSTEMS EARLY FRIDAY, THEN SOUTHERLY WINDS QUICKLY RAMP UP THROUGH
THE AFTERNOON FRIDAY AS A STRONG LOW-LEVEL JET PASSES OVER THE
REGION. THIS WILL BE TIED TO A STRONGER LOW PRESSURE SYSTEM TRACKING
JUST NORTH OF THE GREAT LAKES. A GALE WATCH REMAINS IN EFFECT FROM
FRIDAY AFTERNOON THROUGH FRIDAY NIGHT AS MODEL DATA CONTINUES TO
SHOW HIGH PROBABILITY FOR SOUTHERLY GALES. A BRIEF WINDOW FOR PEAK
GUSTS AROUND 40 KNOTS EXISTS LATE FRIDAY EVENING. MILDER AIR AND A
CHANCE OF RAIN AND SNOW WILL ACCOMPANY THIS SYSTEM BEFORE FRIGID
ARCTIC AIR SETTLES OVER THE REGION TO START NEXT WEEK.
PREV DISCUSSION
ISSUED AT 1147 PM EST WED JAN 15 2025
AVIATION...
FAVORABLE CONDITIONS WILL EMERGE OVERNIGHT AND EARLY THURSDAY FOR AN
INCREASE IN SNOW SHOWER COVERAGE. INITIAL ACTIVITY WILL DEVELOP
WITHIN THE 07Z-10Z WINDOW, WITH SOME VARIABILITY LIKELY IN BOTH
CLOUD BASE AND VISIBILITY AS LOW LEVEL MOISTURE GRADUALLY INCREASES
AND SNOW SHOWER INTENSITY REMAINS LIGHT. HIGHEST PROBABILITY FOR
SNOW SHOWERS WITH ASSOCIATED IFR CONDITIONS AND ACCUMULATION
POTENTIAL WILL EXIST DURING THE MID-LATE MORNING HOURS. POTENTIAL
DOES EXIST FOR THIS ACTIVITY TO LINGER SLIGHTLY LONGER INTO THE
AFTERNOON, DEPENDING ON THE PACE OF A PASSING MID LEVEL WAVE. WINDS
VEERING WITH TIME FROM SOUTHWEST TO WEST THRU THE MORNING PERIOD,
THEN BECOMING NORTHWESTERLY WITH MODEST GUSTINESS IN THE AFTERNOON.
FOR DTW...INCREASING PROBABILITY FOR SNOW SHOWERS AFTER 08Z, WITH
THE HIGHEST COVERAGE EXPECTED BETWEEN 10Z AND 16Z THURSDAY MORNING.
DTW THRESHOLD PROBABILITIES...
* HIGH FOR CEILINGS AOB 5000 FEET THROUGH THURSDAY.
* HIGH FOR PTYPE OF SNOW OVERNIGHT AND THURSDAY MORNING.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...GALE WATCH FROM FRIDAY AFTERNOON THROUGH LATE FRIDAY NIGHT FOR
LHZ362-363-421-441-462>464.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...KDK
MARINE.......TF
AVIATION.....MR
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