111
FXUS63 KDTX 190529
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1229 AM EST THU DEC 19 2024
KEY MESSAGES
- FLURRIES OR A STRAY SNOW SHOWER THIS EVENING GIVE WAY TO PARTIAL
CLEARING LATE TONIGHT.
- THE NEXT LOW PRESSURE SYSTEM MOVES INTO THE GREAT LAKES LATE
THURSDAY WITH A ROUND OF SNOW EXPECTED TO LAST THROUGH FRIDAY. SNOW
COVERED ROADS ARE LIKELY TO AFFECT THE FRIDAY MORNING COMMUTE.
- A GENERAL 1 TO 3 INCH SNOW ACCUMULATION IS EXPECTED ACROSS SE
MICHIGAN DURING THE THURSDAY NIGHT AND FRIDAY TIME PERIOD.
- LOCALLY HIGHER TOTALS ARE POSSIBLE DUE TO LAKE EFFECT BANDS IN THE
THUMB, ESPECIALLY FRIDAY INTO FRIDAY NIGHT.
- MUCH COLDER AIR MOVES IN FOR THE WEEKEND LIMITING DAYTIME
TEMPERATURES TO THE 20S WITH SINGLE DIGIT READINGS POSSIBLE AT
NIGHT.
DISCUSSION
MORNING LIGHT SNOW GAVE WAY TO CLOUDS FOR THE AFTERNOON WHICH
CONTINUE THIS EVENING ALONG WITH FLURRIES OR A STRAY SNOW SHOWER.
COLDER NW LOW LEVEL FLOW HAS ACTIVATED THE NORTHERN GREAT LAKES AND
THERE IS STILL SEVERAL HOURS OF SUB 850 MB COLD ADVECTION TO GO THIS
EVENING. THIS MAKES A STRAY SNOW SHOWER POSSIBLE MAINLY TOWARD THE
TRI CITIES AND THUMB IN THE STEEP LOW LEVEL LAPSE RATE ENVIRONMENT
UNTIL CONVECTIVE DEPTH IS FORCED DOWN IN LARGER SCALE SUBSIDENCE
ALOFT TOWARD MIDNIGHT. UPSTREAM SATELLITE OBSERVATIONS SUPPORT
18/12Z MODEL PROJECTIONS OF THE 500 MB SHORT WAVE RIDGE AND
CONFLUENT FLOW BUILDING FROM CENTRAL CANADA AND THE UPPER MIDWEST
INTO THE GREAT LAKES WITH ENOUGH SUBSIDENCE TO EVEN PRODUCE A FEW
CLOUD BREAKS LATE TONIGHT INTO THURSDAY MORNING. GUIDANCE LOWS IN
THE MID 20S THEN LOOK ON TARGET AS SURFACE WIND DIMINISHES WITH A
BRIEF PERIOD OF HIGH PRESSURE THURSDAY MORNING.
THE FORECAST FOCUS QUICKLY SHIFTS TO THE NEXT LOW PRESSURE SYSTEM
STILL EXPECTED TO BRING WIDESPREAD SNOW ACCUMULATION TO LOWER MI
BEGINNING LATE THURSDAY AND LASTING THROUGH FRIDAY. SATELLITE
IMAGERY THIS AFTERNOON SHOWS THE SUBJECT MID LEVEL CIRCULATION
MOVING INTO THE ROCKIES WHILE PRESENTING RESPECTABLE STRENGTH. IT
BENEFITS INITIALLY FROM RAPID LONG WAVE AMPLIFICATION AND LEE SIDE
SURFACE CYCLOGENESIS IN NORTHERN PLAINS TONIGHT AND THURSDAY, IN
TIME TO BRING A STRONG SURGE OF MID LEVEL WARM ADVECTION INTO THE
GREAT LAKES LATE THURSDAY AND THURSDAY NIGHT. MODEL AGREEMENT ON THE
TRACK OF THE SURFACE LOW COULD BE BETTER WITHIN 48 HOURS, HOWEVER
THEIR IS SOME CLARITY ON THE GENERAL EVOLUTION OF THE SYSTEM FROM A
STRENGTH AND ORGANIZATION PERSPECTIVE. THE EVENT PEAK IS FOCUSED ON
THE LEADING SURGE OF STRONG WARM ADVECTION THURSDAY NIGHT FOLLOWED
BY THE LOSS OF ORGANIZATION FRIDAY AS FORCING CHANGES CHARACTER TO
BECOME MORE CELLULAR/CONVECTIVE. THIS TRANSITION OCCURS AS THE SHORT
WAVE CIRCULATION DIVES WELL SOUTH INTO THE TN VALLEY LEAVING THE
LONG WAVE TROUGH/COLD POOL OVER LOWER MI TO SET UP THE UNSTABLE
THERMAL PROFILE BUT NOT MUCH ELSE. ACCUMULATION IN THE 1 TO 3 INCH
RANGE STILL LOOKS GOOD WHEN INCORPORATING THE PEAK WARM ADVECTION
FORCING WITH THE TREND TOWARD SCATTERED SNOW SHOWERS DURING FRIDAY.
THE EXCEPTION AND ADDITIONAL CHALLENGE IS FACTORING LAKE ENHANCEMENT
INTO THE THUMB WHICH COULD BE SUBSTANTIAL IN A POTENTIAL DOMINANT
BAND SCENARIO. TRENDS TO MONITOR INCLUDE THE DEVELOPMENT OF A
NORTH/SOUTH SURFACE TROUGH THAT COULD FOCUS A DOMINANT BAND THAT
GETS PULLED ONSHORE AS THE SURFACE LOW EXITS THE OHIO VALLEY LATE
FRIDAY.
THE LONG WAVE TROUGH ASSOCIATED WITH THE FRIDAY SYSTEM REMAINS
PROGRESSIVE HEADING INTO THE WEEKEND. DEEP NORTHERLY FLOW FOLLOWS
THE TROUGH AXIS PASSAGE WHICH USHERS IN ANOTHER ROUND OF ARCTIC AIR
ACROSS THE GREAT LAKES. GUIDANCE TEMPERATURES IN THE 20S DURING THE
DAY AND SINGLE DIGITS AT NIGHT MATCH UP WITH EXTENDED RANGE MODEL
SOLUTIONS THAT SHOW A BROAD AREA OF POLAR SURFACE HIGH PRESSURE
SETTLING ACROSS THE REGION. ANOTHER PACIFIC SHORT WAVE CIRCULATION
IS ALSO PROJECTED WITH REASONABLE AGREEMENT TO BRING ANOTHER ROUND
OF SNOW TO THE GREAT LAKES TO START NEXT WEEK.
MARINE
WINDS QUICKLY DECREASE THIS MORNING AS HIGH PRESSURE BRIEFLY SLIDES
ACROSS THE CENTRAL GREAT LAKES. MODEST EASTERLY FLOW (15-20KT) WILL
DEVELOP BY EVENING IN ADVANCE OF A CLIPPER SYSTEM DROPPING THROUGH
THE UPPER MIDWEST. THIS SYSTEM ARRIVES OVER OUR REGION LATE TODAY
THROUGH THE FIRST HALF FRIDAY BRINGING WIDESPREAD SNOW SHOWERS.
WINDS VEER TO NORTHERLY LATTER HALF OF FRIDAY ON THE BACKSIDE OF THE
LOW THOUGH WINDS ARE STILL ONLY EXPECTED TO REACH 20-25KTS,
STRONGEST IN THE BAY AND NEAR THE THUMB. THAT SAID, ONSHORE FLOW
WILL REQUIRE ANOTHER SMALL CRAFT ADVISORY FOR THE THUMB/BAY
NEARSHORE WATERS. A SECOND HIGH THEN BUILDS OVER THE REGION THIS
WEEKEND.
PREV DISCUSSION
ISSUED AT 706 PM EST WED DEC 18 2024
AVIATION...
UPPER LEVEL TROUGHING AND ASSOCIATED COLD ADVECTION WILL SUPPORT
HIGH MVFR TO VFR STRATOCUMULUS OVER SOUTHEAST MICHIGAN TONIGHT.
INCREASED TURBULENT MIXING MAY CAUSE CEILING HEIGHTS TO RISE 500
FEET OR SO OVERNIGHT. SURFACE WINDS ARE EXPECTED TO EMERGE OUT OF
THE SOUTHEAST AFTER DAYBREAK THURSDAY. THE LEAD WARM ADVECTION WING
TO THE CLIPPER SYSTEM WILL ARRIVE NORTH OF I 69 CORRIDOR AFTER 21Z
THURSDAY WITH LOWER CONFIDENCE ON TIMING OF ONSET AT DTW TERMINALS.
DTW THRESHOLD PROBABILITIES...
* HIGH FOR CEILING AT OR BELOW 5000 FEET TONIGHT AND THURSDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR LHZ421-441-442.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...CB
MARINE.......KDK
AVIATION.....CB
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