387
FXUS63 KDTX 141731
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1231 PM EST SAT DEC 14 2024
KEY MESSAGES
- TEMPERATURES WARMING UP INTO THE MID 30S THIS AFTERNOON.
- PRECIPITATION MOVES IN EARLY SUNDAY MORNING WITH A CHANCE FOR
LIGHT FREEZING RAIN BEFORE DAYBREAK, PRIMARILY IN THE HIGHER
ELEVATIONS OF THE IRISH HILLS AND TRI CITIES. ROADWAYS MAY BECOME
SLIPPERY WITH POTENTIAL FOR DIFFICULT TRAVEL SUNDAY MORNING.
- TRANSITION TO ALL RAIN OCCURS SUNDAY WITH A SECOND ROUND OF
RAINFALL ON MONDAY. COMBINED RAINFALL TOTALS MAY EXCEED ONE INCH IN
SOME LOCATIONS.
- SEASONABLY WARM TEMPERATURES APPROACH 50 DEGREES ON MONDAY BEFORE
DROPPING BACK TOWARD NORMAL BY MID-WEEK.
AVIATION
STRONG HIGH PRESSURE TO THE EAST MAINTAINS A DRY E TO ESE WIND
AROUND 10 KNOTS THROUGH THIS EVENING WITH PREVAILING VFR BENEATH
INTERVALS OF BKN CIRRUS. LOW PRESSURE OVER THE CENTRAL PLAINS WILL
WEAKEN AS IT TRACKS NE TOWARD THE GREAT LAKES TONIGHT. THIS SYSTEM
WILL BRING RAPIDLY INCREASING MOISTURE DURING THE OVERNIGHT PERIOD,
RESULTING IN DETERIORATING AVIATION CONDITIONS AS RAIN SPREADS IN
AND CEILINGS/VISIBILITIES LOWER. PRECIP ARRIVAL AROUND OR SHORTLY
AFTER MIDNIGHT OFFERS POTENTIAL FOR AN INITIAL BRIEF PERIOD OF LIGHT
FREEZING RAIN OR DRIZZLE BEFORE MILDER AIR BRINGS SURFACE
TEMPERATURES ABOVE FREEZING THROUGH THE EARLY MORNING HOURS. HIGHEST
PROBABILITIES FOR -FZRA CONTINUE TO EXIST FOR THE TRI-CITIES AND
AREAS WEST OF US-23, AND MADE NO SIGNIFICANT CHANGES TO THE
INHERITED TAFS. LOW CEILINGS WILL SPREAD IN FROM THE SOUTHWEST
DURING THE EARLY MORNING WITH HIGH PROBABILITIES FOR IFR THROUGH
MUCH OF SUNDAY AS ABUNDANT LOW-LEVEL MOISTURE HOLDS. LIFR WILL BE A
POSSIBILITY AS WELL. POCKETS OF RAIN WILL CONTINUE, ESPECIALLY
ACROSS THE SOUTHEAST PART OF THE STATE, THROUGH MUCH OF THE DAYLIGHT
HOURS BEFORE TAPERING OFF SUNDAY EVENING.
FOR DTW...A VERY LOW PROBABILITY EXISTS FOR LIGHT FREEZING RAIN OR
DRIZZLE EARLY SUNDAY MORNING /07Z-09Z/ SHOULD PRECIPITATION
MATERIALIZE AS TEMPERATURES HOVER NEAR FREEZING. A GREATER SURGE OF
MOISTURE AFTER 09Z WILL BE ACCOMPANIED BY WARMING TEMPERATURES,
SUPPORTING JUST RAIN.
DTW THRESHOLD PROBABILITIES...
* HIGH FOR CEILINGS AOB 5KFT LATE TONIGHT AND SUNDAY.
* VERY LOW FOR PRECIPITATION TYPE AS FREEZING RAIN BETWEEN 07Z-09Z
EARLY SUNDAY MORNING.
PREV DISCUSSION
ISSUED AT 417 AM EST SAT DEC 14 2024
DISCUSSION...
HIGH PRESSURE INFLUENCE IS PREVALENT THIS MORNING AS SE MICHIGAN
RESIDES UNDER MOSTLY CLEAR SKIES, ASIDE FROM THE OCCASIONAL CIRRUS
STREAMER. EXCELLENT RADIATIONAL COOLING CONDITIONS HAVE ALLOWED
TEMPERATURES TO BOTTOM OUT OVERNIGHT, WITH MANY LOCATIONS REPORTING
LOWS IN THE SINGLE DIGITS. THIS ARCTIC AIRMASS IS TRAPPED UNDERNEATH
AN ACTIVE LAYER OF WARM ADVECTION THAT IS REINFORCING THE SUBSIDENCE
INVERSION ALOFT. JUDGING FROM UPSTREAM TRENDS (I.E. 00Z SOUNDINGS AT
DVN AND ILX), WOULD EXPECT A NEARLY +10 C RISE IN 850 MB
TEMPERATURES IN THE 12Z KDTX SOUNDING IN COMPARISON TO 00Z. AT THE
SURFACE THIS EQUATES TO A NOTABLE INCREASE IN TEMPERATURES
THROUGHOUT THE DAY, PEAKING IN THE MID 30S THIS AFTERNOON.
THE DRIVING MECHANISM BEHIND THIS WARM ADVECTION PATTERN IS A
DEVELOPING LOW PRESSURE SYSTEM THAT IS CURRENTLY OVER CENTRAL
KANSAS. WHILE TODAY IS STARTING OFF CLEAR, THE UPPER LEVEL MOISTURE
PLUME WILL ADVECT OVERHEAD TO PROMOTE INCREASING HIGH CLOUD COVER.
THE MORE IMPACTFUL ASPECT OF THIS SYSTEM HOWEVER IS THAT IT WILL
BRING THE CHANCE FOR LIGHT FREEZING RAIN EARLY SUNDAY MORNING. AFTER
00Z TONIGHT, A COMBINATION OF TOP-DOWN SATURATION AND THETA-E
ADVECTION WILL WORK TOGETHER TO SATURATE THE SUB-600MB LAYER. IT
WILL TAKE QUITE A BIT OF MOISTURE TO OVERCOME THE PRESENT DRY
AIRMASS, MAKING IT DIFFICULT FOR WET BULBING ALONE TO ENTIRELY
SATURATE THE COLUMN AND LIKELY EATING INTO THE FRONT END OF
PRECIPITATION.
NONETHELESS, MOST MODELS EVENTUALLY TRANSITION FROM VIRGA TO
SPOTTY/LIGHT PRECIPITATION SOMETIME BETWEEN 07Z-09Z (2AM-4AM) WHICH
LEAVES A SHORT PRECIPITATION WINDOW IN WHICH SUB-FREEZING SURFACE
TEMPERATURES EXIST BELOW THE WARM NOSE ALOFT. THE IRISH HILLS AND
SAGINAW VALLEY CONTINUE TO BE THE TWO FAVORED LOCATIONS FOR
TEMPERATURES TO HOLD BELOW FREEZING, OWING TO BOTH POSITIONING OF
THE WARM FRONT AND LOCAL TERRAIN EFFECTS. THESE LOCATIONS MAY SEE
MINOR ICE ACCUMULATIONS OF A FEW HUNDREDTHS OF AN INCH BEFORE
DAYBREAK. LIGHT SNOW ACCUMULATIONS ARE EVEN A POSSIBILITY FOR THE
SAGINAW VALLEY, WHERE THE LATEST GUIDANCE HAS COME IN WITH A
SLIGHTLY COLDER WET BULB PROFILE. WHETHER ICE OR SNOW, ANY EARLY
MORNING ACCUMULATIONS WILL BE LIGHT. FOR THE EASTERN PORTIONS OF THE
CWA, WARMER ONSHORE FLOW OFF OF THE LAKES SHOULD KEEP TEMPERATURES
ABOVE FREEZING TO SUPPORT MAINLY RAIN EVEN AT ONSET.
THE FREEZING LINE WILL MAKE A STEADY MARCH NORTHWARD ACROSS THE CWA
BY DAYBREAK, TRANSITIONING ANY FREEZING PRECIP TO ALL RAIN BY MID-
MORNING AT THE LATEST. THE UPPER LOW WILL SLIDE DIRECTLY OVER SE
MICHIGAN SUNDAY AFTERNOON, BRINGING A DRY SLOT WITH IT AND TAPERING
OFF RAIN CHANCES THROUGH THE EVENING. WHEN ALL IS SAID AND DONE,
RAINFALL TOTALS WILL RANGE BETWEEN A TENTH TO HALF INCH ACROSS SE
MICHIGAN. A NORTHERN STREAM SURFACE LOW WILL FOLLOW CLOSELY BEHIND
TONIGHT'S SYSTEM, PUSHING AN OCCLUDED FRONT ACROSS THE AREA ON
MONDAY. SE MICHIGAN WILL BE COMFORTABLY WITHIN THE WARM SECTOR FOR
THIS EVENT, IMPLYING ALL RAIN AS TEMPERATURES RISE TOWARD 50 DEGREES
ON MONDAY. ENSEMBLE MEAN QPF FOR THIS SECOND ROUND OF RAINFALL IS
AROUND A HALF INCH. THE PASSAGE OF THE OCCLUDED FRONT ACROSS THE CWA
WILL MARK THE RETURN OF COLDER TEMPERATURES MORE TYPICAL OF DECEMBER
IN SE MICHIGAN.
MARINE...
MODERATE (15-25 KNOTS) SOUTHEAST WINDS WILL DEVELOP AS STRONG HIGH
PRESSURE BUILDS OVER EASTERN CANADA. THIS WILL LEAD TO BUILDING
WAVES OVER LAKE HURON WITH SMALL CRAFT ADVISORIES NEEDED OVER THE
NEARSHORE WATERS FROM SATURDAY INTO SUNDAY BEFORE WINDS VEER TO THE
SOUTH AND WEAKEN. WARMER AIR WILL GRADUALLY WORK INTO THE REGION
ALLOWING FOR MOST OF THE PRECIPITATION FALLING AS RAIN FOR THE
SECOND HALF OF THE WEEKEND AS WEAKENING LOW PRESSURE TRACKS IN FROM
THE MIDWEST. THIS LOW AND ANY COLD AIR FIZZLE OUT IN FAVOR OF THE
STRONGER/MORE AMPLIFIED UPPER LEVEL TROUGH OVER THE NORTHERN PLAINS
SUNDAY NIGHT.
RESUMED MODERATE SOUTHERLY FLOW CAN BE EXPECTED WITH ADDITIONAL RAIN
BY MONDAY. HOWEVER, THE COLD AIR BEHIND THE COLD FRONT MONDAY NIGHT
INTO TUESDAY NOW LOOKS TEMPERED, AS THE MAIN LOW IS PROGGED TO BE
MUCH FARTHER NORTH (NEAR JAMES BAY). DESPITE THIS, THERE REMAINS A
CHANCE FOR GALES OVER LAKE HURON, OR AT LEAST MARGINAL BRIEF GUSTS
TO GALES AS MIXING DEPTHS RAMP UP MONDAY NIGHT INTO TUESDAY. AN EVEN
STRONGER COLD FRONT LOOKS TO BE TRACKING THROUGH ON WEDNESDAY, AND
NORTHERLY WINDS WEDNESDAY NIGHT AND THURSDAY MAY END UP BEING
SIGNIFICANTLY STRONGER THAN THE OUTGOING FORECAST, MORE IN THE 20-30
KNOT RANGE. THERE IS A DEVELOPING LOW PRESSURE SYSTEM TRACKING
THROUGH THE KENTUCKY/TENNESSEE VALLEY WHICH WILL ALSO HAVE SOME
INFLUENCE ON THE OUTCOME.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM
EST SUNDAY FOR LHZ421.
SMALL CRAFT ADVISORY UNTIL 10 PM EST SUNDAY FOR LHZ441-442.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST SUNDAY
FOR LHZ443.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....TF
DISCUSSION...MV
MARINE.......SF/DG
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