697
FXUS63 KDTX 142115
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
415 PM EST SAT DEC 14 2024
KEY MESSAGES
- A WINTER WEATHER ADVISORY IS IN EFFECT TONIGHT FOR PORTIONS OF
SOUTHEAST MICHIGAN AS LIGHT FREEZING DRIZZLE/RAIN LIFTS INTO THE
WESTERN AREAS.
- ROADWAYS MAY BECOME SLIPPERY LATE TONIGHT BEFORE PRECIPITATION
TRANSITIONS TO ALL LIQUID RAIN BY SUNDAY MORNING.
- SEASONABLY WARM TEMPERATURES BREAK THE 50 DEGREE MARK (SOUTH OF I-
69) MONDAY WITH MORE RAIN, THEN READINGS DECLINE THROUGHOUT THE
WORKWEEK.
DISCUSSION
ALTHOUGH STILL BELOW CLIMATOLOGICAL AVERAGES TODAY, A LOW PRESSURE
SYSTEM OVER THE PLAINS AND ITS APPROACHING WARM SECTOR HAVE HELPED
MODERATE THE AIRMASS AS SOME READINGS CLIMB ABOVE THE FREEZING MARK
FOR THE FIRST TIME SINCE WEDNESDAY. THIS WARM-UP BECOMES MORE
PRONOUNCED SUNDAY AND MONDAY, BUT NOT BEFORE ANOTHER DOSE OF WINTRY
WEATHER OVERNIGHT. CONUS 14.12Z RAOB DATA REVEALED THE SYSTEM'S
ELEVATED WARM FRONT MARKED BY H8 TEMPS OF 3C/4C AT KILX/KILN WHICH
ATTEMPTS TO PUSH NNE INTO SOUTHEAST MICHIGAN. ACTUAL H8 TEMPS WILL
LIKELY BE COOLER AS THE LOW-LEVEL WARM AIR ADVECTS INTO THE REGION,
BUT STILL EXPECT A 2-4 KFT LAYER OF POSITIVE (CELSIUS) AIR BETWEEN H9
AND H8 WHICH LENDS CONFIDENCE IN LIQUID PRECIPITATION TYPE UPON
ARRIVAL OF THE LOW'S PRECIPITATION SHIELD. TIMING FOR THIS IS LARGELY
EXPECTED TO HOLD OFF UNTIL CLOSER TO 03Z AS THE OVER-RUNNING PRECIP
REACHES THE WESTERN CWA BOUNDARY.
OPTED TO ISSUE A TWO-SEGMENT WINTER WEATHER ADVISORY TONIGHT GIVEN
ENOUGH CONFIDENCE IN A DRY ESE SURFACE WIND (LOW DEWPOINTS), RETURN
OF SUB-FREEZING TEMPERATURES (OFF DAYTIME HIGHS IN THE MID 30S), AND
AMPLE COLD/SNOW COVERED SURFACES. FOR THE SHORTER SEGMENT WHICH
ENCOMPASSES THE COUNTIES OUTSIDE OF THE TRI-CITIES (MIDLAND, BAY, AND
SAGINAW COUNTIES), OVERALL DURATION OF LIGHT FREEZING RAIN/DRIZZLE
SHOULD ONLY LEAD TO A THIN COATING (AROUND ONE OR TWO HUNDRETHS) OF
ICING DURING THE FIRST HALF OF THE NIGHT. EVENTUALLY, THE NON-
DIURNAL WARM ADVECTION WINS OUT AT THE SURFACE AND LIFTS TEMPERATURES
ABOVE 32F AS (NON-FREEZING) RAINFALL RATES INCREASE. UNCERTAINTY
STILL EXISTS WITH TIMING THE FRONT-END VIRGA TO PRECIP TRANSITION,
THE RATE OF EVENING COOLING TO RECONDITION THE LOW-LEVEL THERMAL
ENVIRONMENT, AND ARRIVAL OF MODERATE RAINFALL WHICH MAY ULTIMATELY
RESULT IN NEGLIGIBLE ICING IF ALL THREE COMPONENTS FAIL TO
ASSIMILATE. THIS WOULD, INSTEAD, YIELD JUST A COLD AND SOGGY NIGHT.
OTHER CONSIDERATIONS OF NOTE FOR THIS SEGMENT INCLUDE THE POTENTIAL
FOR STARK DIFFERENCES BETWEEN THE WESTERN AND EASTERN PORTIONS OF
EACH COUNTY. GIVEN THE CONDITIONALITY ON TIMING THE CHANGEOVER TO
PURE LIQUID RAINFALL, THE WESTERN PORTIONS OF THE COUNTIES WILL BE
MORE SUSCEPTIBLE TO FREEZING RAIN ACCUMULATIONS THAN THE EASTERN SIDE
OF EACH COUNTY. ALSO, MOST OF OAKLAND COUNTY SHOULD AVOID FREEZING
RAIN, BUT THE TERRAIN EFFECTS ALONG THE IRISH HILLS COULD WARRANT A
MORE TARGETED SPS (OR LAST-MINUTE UPGRADE) ONCE THE THE EVENT BEGINS
TO UNFOLD TONIGHT.
AS FOR THE TRI-CITIES, THE WINTER WEATHER ADVISORY IS LONGER IN
DURATION AND WILL LIKELY SEE SLIGHTLY HIGHER ICE TOTALS (BUT STILL
AOB A TENTH). THIS ACCOUNTS FOR A DELAY IN THE ARRIVAL OF THE WARMER
AIRMASS (SEE LATEST AIR TEMPERATURE FORECAST) AND LIGHTER
PRECIPITATION RATES WHICH ARE EXPECTED TO PERSIST UNTIL CLOSER TO
12Z. THIS AREA ALSO STANDS A BETTER CHANCE TO SEE MORE WIDESPREAD
IMPACTS TO ROADWAYS (INSTEAD OF JUST ELEVATED SURFACES) AS HIGH
TEMPERATURES HOLD NEAR/BELOW THE FREEZING MARK THIS AFTERNOON AND
OVERNIGHT.
AXIS OF MAXIMUM THETAE ADVECTION CURVES CYCLONICALLY UP FROM THE
OHIO VALLEY INTO SOUTHERN LOWER MICHIGAN LATE TONIGHT INTO SUNDAY
MORNING BENEATH JET-LEVEL DIVERGENCE WHICH FAVORS PERIODS OF
MODERATE RAINFALL RATES. SOME AREAS COULD SEE RAINFALL TOTALS
APPROACHING A HALF INCH BY SUNDAY AFTERNOON. THE MID-LEVEL VORTMAX
EXITS INTO THE SOUTHERN ONTARIO PENINSULA BY 00Z MONDAY WHICH
ENSURES ALL LOCATIONS DRY OUT BY SUNSET SUNDAY EVENING. HEIGHT RISES
FILL-IN AGGRESSIVELY SUNDAY NIGHT INTO MONDAY WITH A PERIOD OF
RIDGING AND DIFFERENTIAL THERMAL ADVECTION. HIGHS BREAK INTO THE 50S
FOR MUCH OF THE REGION MONDAY AS H8 TEMPS CLIMB INTO THE UPPER
SINGLE DIGITS (C). CYCLOGENESIS OCCURING OVER THE DAKOTAS DEEPENS TO
A 998 MB LOW OVER SOUTH-CENTRAL CANADA MONDAY WITH A COLD FRONT
EXTENDING INTO THE MISSISSIPPI VALLEY. PRE-FRONTAL MOISTURE AND
PWATS IN EXCESS OF 0.75 INCHES SHOULD LEAD TO ANOTHER ROUND OF RAIN
MONDAY, THIS TIME FRONTALLY FORCED. COLDER AIR THEN SETTLES IN
THROUGH THROUGHOUT THE WORKWEEK.
MARINE
SOUTHEAST WINDS OF 15 TO 25 KNOTS HAVE DEVELOPED OVER LAKE HURON
THIS AFTERNOON AS EXPECTED, ALLOWING 4+ WAVES TO IMPACT THE
NEARSHORE ZONES THROUGH TOMORROW, WITH WINDS ATTEMPTING TO BECOME
MORE DUE SOUTHERLY INTO SUNDAY NIGHT. WARMER AIR WILL GRADUALLY WORK
INTO THE REGION ALLOWING FOR MOST OF THE PRECIPITATION FALLING AS
RAIN LATE TONIGHT/SUNDAY 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. COLD FRONT, ATTACHED TO LOW PRESSURE TRACKING THROUGH
ONTARIO AND NEAR JAMES BAY, WILL SWING THROUGH THE CENTRAL GREAT
LAKES EARLY MONDAY EVENING. TIGHT PRESSURE GRADIENT WITH 850 MB
TEMPS LOWERING TO AROUND -8 C LOOKS SUPPORTIVE OF WIND GUSTS IN
THE 30 TO 35 KNOT RANGE OVER CENTRAL AND NORTHERN LAKE HURON, LATE
MONDAY NIGHT INTO EARLY TUESDAY MORNING. HOWEVER, GUSTS TO GALES
APPEAR TO BE BRIEF, AS THE PRESSURE GRADIENT QUICKLY RELAXES DURING
THE DAY ON TUESDAY. THUS, NOT PLANNING ON GALE WATCH AT THIS TIME.
AN EVEN STRONGER COLD FRONT LOOKS TO BE MOVING THROUGH ON WEDNESDAY,
AND NORTHERLY WINDS LATE WEDNESDAY THROUGH THURSDAY MORNING WILL
LIKELY REACH INTO THE 20 TO 30 KNOT RANGE, BUT ULTIMATELY INFLUENCED
BY THE STRENGTH AND POSITION OF LOW PRESSURE TRACKING THROUGH/NEAR
THE SOUTHERN OHIO VALLEY. A RIDGE OF HIGH PRESSURE QUICKLY FOLLOWS,
ALLOWING FOR A PERIOD OF LIGHT WINDS TO END THE WORK WEEK.
HYDROLOGY
AREAS OF FREEZING DRIZZLE/RAIN TRANSITION TO ALL LIQUID RAIN TONIGHT
WITH PERIODS OF MODERATE RAINFALL RATES POSSIBLE ALONG/SOUTH OF I-
94. SOME OF THESE AREAS COULD SEE UP TO A HALF INCH OF RAINFALL BY
SUNDAY EVENING. NO FLOODING IS EXPECTED, BUT PONDING ON ROADWAYS AND
IN LOW-LYING AREAS IS POSSIBLE. AN ADDITIONAL QUARTER TO A THIRD OF
AN INCH OF RAIN MAY DEVELOP MONDAY WITH THE ARRIVAL OF A COLD FRONT.
PREV DISCUSSION
ISSUED AT 1231 PM EST SAT DEC 14 2024
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.
DTX WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST SUNDAY
FOR MIZ047-048-053.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 AM EST SUNDAY
FOR MIZ054-060-061-068-075-082.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 AM EST SUNDAY FOR LHZ421.
SMALL CRAFT ADVISORY UNTIL 10 PM EST SUNDAY FOR LHZ441-442.
SMALL CRAFT ADVISORY UNTIL 4 PM EST SUNDAY FOR LHZ443.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...KGK
MARINE.......SF
HYDROLOGY....KGK
AVIATION.....TF
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