Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 242025
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
325 PM EST TUE FEB 24 2015

.SHORT TERM...TONIGHT

SNOW SHOWER ACTIVITY HAS BEEN SLOW TO START ACROSS SOUTHEAST
MICHIGAN...HOWEVER...ALL SIGNS ARE STILL POINTING TOWARDS SNOW
ARRIVING WITHIN THE NEXT FEW HOURS. CURRENT RADAR AND OBSERVATIONS
INDICATE SNOW BEGINNING IN THE NORTH AND WEST ALREADY AND IS SLOWLY
SLIDING SOUTHEASTWARD ACROSS THE CWA. THIS SNOW ACTIVITY WILL ONLY
RESULT IN A FLURRY OR A COUPLE TENTHS OF SNOW. THE MODELS AND
UPSTREAM OBSERVATIONS INDICATE THAT A COLD FRONT IS STILL DROPPING
DOWN FROM THE NORTHWEST AND WILL BE COMBINED WITH PLENTY OF
INSTABILITY AND MOISTURE THIS EVENING. THIS ARCTIC FRONT WILL BE THE
MAJOR SNOW MAKER THIS EVENING. ONCE THE SNOW WITH THE FRONTAL SYSTEM
STARTS EARLY THIS EVENING...LIGHT SNOW WILL CONTINUE THROUGHOUT MUCH
OF THE EVENING...ENDING BY 1 AM WEDNESDAY. POCKETS OF HEAVIER SNOW
SQUALLS COULD BE POSSIBLE AS THE FRONT PUSHES THROUGH THE REGION.
TOTAL SNOW ACCUMULATIONS SHOULD BE UNDER ONE INCH... WITH ONLY ABOUT
A HALF INCH IN THE METRO DETROIT AREA AND SOUTH TOWARDS OHIO.

GUSTY WINDS WILL DIMINISH QUICKLY BEHIND THE PASSAGE OF THIS COLD
FRONT AND CLOUD COVER WILL BECOME MORE SCATTERED IN NATURE. WITH
CLEARING SKIES OVERNIGHT...EXPECT TEMPERATURES TO DROP INTO THE
SINGLE DIGITS. WIND CHILLS WILL SOLIDLY BE IN THE NEGATIVE SINGLE
DIGITS WITH LOCATIONS IN THE THUMB POSSIBLY TOUCHING WIND CHILLS
BETWEEN -10 AND -15 DEGREES. WHILE WIND CHILLS IN THE NORTHERN THUMB
REGION WILL BE BORDERLINE ADVISORY CRITERIA...CURRENT THINKING IS
THAT WINDS WILL DIMINISH ENOUGH TO RESULT IN THESE AREAS ONLY
BRIEFLY REACHING -13 TO -15 DEGREES FOR AN HOUR OR TWO. AT THIS TIME
HAVE REFRAINED FROM ISSUING ANY WIND CHILL ADVISORIES FOR THE THUMB
REGION...HOWEVER...THIS WILL DEFINITELY HAVE TO BE CLOSELY MONITORED
AS THE EVENING AND OVERNIGHT PERIOD PROGRESSES.

&&

.LONG TERM...

WATCHING THE STRONG UPPER WAVE NOW ENTERING ALBERTA THIS AFTERNOON
DIVING SOUTHEAST THROUGH THE NORTHERN PLAINS TOMORROW...AND INTO THE
MIDWEST TOMORROW EVENING. THE MID LEVEL FLOW (700 MB) IS EXPECTED TO
TO BACK JUST ENOUGH TO TRANSPORT SPECIFIC HUMIDITY VALUES AROUND 1
G/KG NEAR SAGINAW BAY...TO UP TO 1.75 G/KG RIGHT AT THE SOUTHERN
MICHIGAN BORDER...PER 12Z EURO. WHETHER THIS 700 MB FGEN
FORCING/MOISTURE WILL BE ENOUGH TO PRODUCE LIGHT SNOW IS
QUESTIONABLE (SEE 12Z NAM)...AS THE LOW LEVELS WILL BE MUCH
DRIER...AS WINDS COME OUT OF THE NORTHEAST. HOWEVER...EVEN
THOUGH LAKE HURON IS MOSTLY FROZEN...SOME MOISTURE FLUX WILL STILL
OCCUR...AND WITH 12Z EURO/CANADIAN SOLUTIONS BOTH INDICATING
MEASURABLE QPF MOST OF SOUTHEAST MICHIGAN...SOLID CHANCE POPS
SEEM WARRANTED TO ME...AS EVEN THE 1000-500 MB MEAN MOISTURE IS
PROGGED TO REACH 90 PERCENT BY 12Z THURSDAY. MUCH DRIER AIR WILL
THEN RETURN LATE THURSDAY INTO THURSDAY NIGHT...AS EXTENSION OF THE
RIDGE AXIS FROM STRONG HIGH (1040+ MB) OVER THE MIDWEST EXTENDS EAST
INTO LOWER MICHIGAN...PROVIDING FAVORABLE RADIATING NIGHT. WITH WINDS
GOING CALM...MINS SHOULD HAVE NO PROBLEM FALLING INTO THE 5 TO 15
BELOW RANGE. WITH THE ADDED MOISTURE AND CLOUDS WEDNESDAY
NIGHT...RAISED MINS INTO THE -5 TO +5 F RANGE. OTHERWISE...RAISED
MAXES ON WEDNESDAY INTO THE TEENS...GIVING MORE CREDIT TO THE LATE
FEBRUARY SUNSHINE...AS EURO INDICATING 925 MB TEMPS AROUND -15 C.
NEGATIVE UPPER TEENS ON THURSDAY AT 925 MB SUGGESTS HIGHS MORE
AROUND THE 10 DEGREE MARK.

A SHIFT IN THE OVERALL PATTERN IS EXPECTED FOR THE BEGINNING OF
MARCH AS UPPER LEVEL ZONAL FLOW BEGINS TO TAKE OVER.  AS HIGH
PRESSURE AND RIDGING BUILD IN...TEMPS WILL REBOUND BACK INTO THE
UPPER 20S.  EVEN THOUGH TEMPS REMAIN BELOW NORMAL...A SWING IN THE
TEMP TREND WILL BE A WELCOMED ONE GIVEN THE NEGATIVE TEMPS THAT HAVE
GRIPPED THE AREA.  ATTENTION THEN TURNS TO SUNDAY AS A SYSTEM THAT
MODELS HAVE BEEN ADVERTISING TO MOVE UP FROM THE SOUTHWEST WITH THE
LATEST GUIDANCE SHIFTING THE SYSTEM MORE SOUTH WITH TEMPS STAYING
BELOW FREEZING.  SNOW CHANCES QUICKLY DIMINISH MONDAY AS SURFACE
HIGH PRESSURE MOVES BACK IN OVER THE REGION.

&&

.MARINE...

GALE FORCE SOUTHWEST WINDS WILL BE COMING TO AN END AS THE COLD
FRONT SLOWLY WORKS THROUGH THE CENTRAL GREAT LAKES TONIGHT. GOOD
SURGE OF LOW LEVEL ADVECTION WILL OCCUR BEHIND THE FRONT LATE
TONIGHT INTO TOMORROW...BUT WIND GUST SPEEDS ARE EXPECTED TO HOLD IN
THE 25 TO 30 KNOT RANGE. SURFACE RIDGE BUILDING INTO THE AREA
WEDNESDAY NIGHT WILL ALLOW WINDS TO DIMINISH...BECOMING LIGHT ON
THURSDAY. LIGHT WINDS WILL PERSIST INTO FRIDAY AS STRONG SURFACE HIGH
BUILDS INTO THE OHIO VALLEY.

&&

.AVIATION...ISSUED 1231 PM EST TUE FEB 24 2015

LIGHT SNOW IS EXPECTED TO SLOWLY MOVE INTO THE REGION BY EARLY
STARTING FIRST IN THE MBS AREA EVENTUALLY REACHING THE SOUTHERN TAF
SITES BY MID TO LATE AFTERNOON. WITH STRONG SOUTHWESTERLY WINDS IN
COMBINATION WITH SNOW FALLING...EXPECT SOME BLOWING SNOW CONDITIONS
ACROSS ALL TERMINALS THIS AFTERNOON. WINDS DIMINISH IN THE EARLY
EVENING HOURS...HOWEVER...SNOW SHOWERS WILL STILL BE POSSIBLE BEFORE
MIDNIGHT. DRY CONDITIONS WILL PERSIST THROUGH THE REMAINDER OF THE
TAF PERIOD WITH SCATTERED TO BROKEN CLOUDS PRESENT.

FOR DTW... SOUTHWEST WIND INCREASING TO 30 KNOT GUSTS COMBINED WITH
FALLING SNOW COULD CAUSE BLOWING SNOW VISIBILITY RESTRICTIONS DURING
THE  MID AFTERNOON HOURS. NEW SNOW ACCUMULATION WILL BE LESS THAN 1
INCH BY EVENING. SNOW SQUALLS ALONG THE NEXT ARCTIC FRONT ARE
EXPECTED TO REMAIN NORTH OF DTW OR WEAKEN AS THEY MOVE INTO THE DTW
AREA MID TO LATE EVENING. ALL SNOW SHOULD END AROUND MIDNIGHT WITH A
SCATTERED CLOUD DECK REMAINING OVER DTW THROUGH WEDNESDAY AFTERNOON.
MVFR CONDITIONS RETURN BY WEDNESDAY EVENING AS THE NEXT SYSTEM
APPROACHES.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE THAT CEILINGS WILL FALL BELOW 5000 FT AFTER 20Z
  TUESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LHZ361>363-421-422-
     441>443-462>464.

LAKE ST CLAIR...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LEZ444.

&&

$$

SHORT TERM...RK
LONG TERM....SF/SS
MARINE.......SF
AVIATION.....RK


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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