Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250454
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1154 PM EST TUE FEB 24 2015

.AVIATION...

COVERAGE OF SNOW SHOWERS WILL DIMINISH RAPIDLY WITH THE PASSAGE OF
THE ARCTIC FRONT EARLY THIS MORNING.  A PERIOD OF GUSTY NORTHWEST
WINDS WILL DEVELOP AS THIS COLDER AIR SURGES IN THROUGHOUT THE
MORNING HOURS.  SOME RESIDUAL POST-FRONTAL STRATUS WILL DECREASE IN
COVERAGE AS WELL...DRIER LOW LEVEL CONDITIONS TAKING A PROGRESSIVE
HOLD AND SUSTAINING VFR CONDITIONS THROUGH WEDNESDAY.

FOR DTW...ARCTIC FRONT MOVES THROUGH AROUND 08Z...BRINGING A WIND
SHIFT TO NORTHWEST AT THIS TIME.  GUSTY NORTHWEST WINDS WILL EXIST
THROUGH THE MORNING PERIOD...GENERALLY IN THE 20 KNOT RANGE.

//DTW THRESHOLD PROBABILITIES...

* LOW CONFIDENCE IN CEILING BELOW 5000 FT EARLY THIS MORNING.

&&

.PREV DISCUSSION...ISSUED 946 PM EST TUE FEB 24 2015

UPDATE...

ARCTIC FRONTAL BOUNDARY NOW AT THE DOORSTEP OF THE TRI-CITIES...ON
SCHEDULE TO QUICKLY ADVANCE SOUTHEAST AND THROUGH SE MICHIGAN
OVER THE NEXT 4-5 HOURS. THE UPTICK IN FRONTAL CONVERGENCE AND THE
ASSOCIATED INCREASE IN CONVECTIVE DEPTH AS COLDER AIR RUSHES IN
BEHIND MAINTAINING A COUPLE FRAGMENTS OF GREATER CONVECTIVE SNOW
SHOWERS/SQUALLS. GREATER COVERAGE WILL TEND TO SWEEP THROUGH THE
TRI-CITIES/THUMB IN CLOSER PROXIMITY TO THE BETTER ASCENT...BUT
ALL LOCATIONS REMAIN VULNERABLE TO SEEING A QUICK BURST /30 TO 45
MINUTES/ OF ACCUMULATING SNOW ANCHORED ON THE FRONT BETWEEN
03Z-07Z. ACCUMULATION OF A HALF INCH OR LESS GIVEN THE LIMITED
RESIDENCE TIME.

ENSUING COLD/DRY AIR ADVECTION WILL BRING AN ABRUMPT END TO THIS
OPPORTUNITY BEHIND 07Z...FOCUS TURNING TO THE LANDING POINT FOR
LOW TEMPERATURES BY MORNING.  GIVEN UPSTREAM TRENDS AND LATEST
MODEL GUIDANCE...SINGLE DIGIT READINGS REMAIN ON TARGET BY MID
MORNING...COLDEST LOCALES ACROSS THE NORTH MAKING A RUN TOWARD THE
ZERO MARK. A PRECIPITIOUS REDUCTION IN WIND SPEEDS AND GUST
FREQUENCY POST-SUNSET WILL SIMPLY RETAIN A MODEST WIND
CHILL...BUT NO REAL EVIDENCE TO SUGGEST A HEADLINE WORTHY /BELOW -15F/
PERIOD OF WIND CHILL WILL EXIST OVER THE MORE EXPOSED NORTHERN
TRI-CITIES/THUMB CORRIDOR.

PREV DISCUSSION...ISSUED 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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

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

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



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