Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 242054
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
354 PM EST MON NOV 24 2014

.SHORT TERM... THROUGH TONIGHT

WIND EVENT CONTINUES OVER SE MI THIS AFTERNOON. INITIAL WIND SURGE
ON THE COLD FRONT MOVED THROUGH THE DETROIT METRO/OHIO BORDER REGION
EARLIER THIS AFTERNOON WITH A QUICK POP OF 50 KT GUSTS TIED TO STEEP
INITIAL ISENTROPIC POST-FRONTAL DOWNGLIDE. BUBBLE OF SURFACE
PRESSURE FALLS OF 7-8 MB/3HR WORKING THROUGH THE REGION AT THIS
HOUR ALONG WITH CONTINUED AGRESSIVE LOW-LEVEL COLD AIR ADVECTION
MAINTAINING STEEP LAPSE RATES WILL CAUSE GUSTS OF 40-50 KT TO
CONTINUE INTO LATE AFTERNOON/EARLY EVENING. FEEL THAT 50 KT
GUSTS...WHILE STILL VERY POSSIBLE...WILL BE THE EXCEPTION FOR THE
REMAINDER OF THE PERIOD SO NO CHANGES TO ADVISORY/WARNING ARE
PLANNED AT THIS POINT...THOUGH WILL CONTINUE TO MONITOR TRENDS.
WINDS WILL DIMINISH SLOWLY DURING THE OVERNIGHT PERIOD AS STEEP LOW-
LEVEL LAPSE RATES ARE MAINTAINED...WITH 30 KT GUSTS STILL POSSIBLE
THROUGH AROUND MIDNIGHT.

TROWAL AREA/DEFORMATION AXIS CURRENTLY RESPONSIBLE FOR WIDESPREAD
PRECIPITATION OVER NORTHWEST HALF OF OUR CWA. THIS WILL CONTINUE TO
LIFT SLOWLY NORTH WHILE COLDER AIR CONTINUES TO FILTER IN FROM THE
WEST AND SOUTHWEST. THE COLDER AIR WILL CAUSE A RATHER QUICK
CHANGEOVER TO SNOW FROM ABOUT 00Z-03Z FROM WEST TO EAST OVER THE
CWA. BY THAT TIME THE PRECIP SHIELD WILL BE LOCATED OVER THE SAGINAW
VALLEY AND CONTINUING TO LIFT NORTH. IT IS A CLOSE CALL FOR
ACCUMULATING SNOW...BUT 12Z MODEL SUITE IS IN AGREEMENT THAT MOST OF
THE PRECIPITATION SHOULD BE TO THE NORTH OF OUR CWA BY THE TIME
CHANGEOVER HAPPENS. WHAT SNOW DOES FALL WILL LIKELY TAKE A
FEW HOURS TO ACCUMULATE GIVEN RELATIVELY WARM GROUND AND
SURFACE TEMPS. CURRENT GRIDS REFLECT THIS WITH JUST AROUND A
HALF INCH TO AN INCH EXPECTED OVER MIDLAND AND BAY COUNTIES.
SOUTHEAST HALF OF THE CWA SHOULD REMAIN MOSTLY DRY OVERNIGHT...BUT
GRADUAL VEERING OF THE LOW/MIDLEVEL WINDS WITH TIME SHOULD ALLOW
SOME LIGHT LAKE-ENHANCED SHOWERS TO EXPAND BACK SOUTHWARD TOWARD THE
I-69 CORRIDOR BY LATE TONIGHT. TEMPERATURES WILL CONTINUE TO
PLUMMET FROM THEIR HIGHS IN THE 50S TO NEAR 60 EARLIER TODAY...ON
THEIR WAY TO LOWS AROUND 30 BY 12Z TUESDAY.

&&

.LONG TERM...TUESDAY THROUGH SUNDAY

A NORTHERN STREAM SHORTWAVE TROUGH WILL DROP INTO THE NORTHERN GREAT
LAKES TUESDAY HELPING TO STALL THE EXIT OF THE SFC TROUGH LAID OUT
BY MONDAYS STRONG LOW PRESSURE SYSTEM. COLD AIR WILL BE FILL IN
QUICKLY BEHIND THE DEPARTING LOW WITH A THERMAL TROUGH AROUND -11C
AT 850MB AND -6C AT 925MB BY 12Z TUESDAY. MOISTURE WILL STILL BE
LINGERING OVER CENTRAL MI FROM THE DEPARTING LOW...WITH MODEL
SOUNDINGS SHOWING MOISTURE THROUGHOUT THE COLUMN UP TO 700MB. IN
ADDITION...THE THERMAL PROFILE MAY BE ENOUGH TO KICK UP A FEW LAKE
ENHANCED SNOW SHOWERS OFF LAKE MI...BUT SHOULD STRUGGLE TO REACH SE
MI AS THE FORCING IS ON THE WEAK SIDE. WITH THE ADDITIONAL BROAD
LIFT FROM THE SHORTWAVE TROUGH...AND A THERMAL PROFILE WORTHY OF AT
LEAST A MENTION OF LAKE EFFECT GENERATION OFF LAKE MI...WILL
CONTINUE WITH LIKELY POPS ACROSS THE SAGINAW VALLEY...TAPERING OFF
TO THE SOUTH. HIGHEST CHANCE OF SHOWERS WILL BE IN THE
MORNING...DECREASING THROUGH THE DAY AS THE FORCING AND MOISTURE
THIN OUT AS HIGH PRESSURE BUILDS INTO THE AREA.

WEDNESDAY SHOULD END UP BEING A FAIRLY QUIET DAY WITH THE
AFOREMENTIONED HIGH SLIDING OVERHEAD. THE BROAD VIEW SHOWS SEVERAL
FEATURES THAT WE MAY DODGE WITH A POTENTIAL NOR`EASTER TRACKING ON
THE ATLANTIC COAST...A WEAK CLIPPER TRACKING SOUTH THROUGH THE OHIO
VALLEY...AND RESIDUAL TROUGHING TO OUR NORTH. THIS HIGH WILL DRY OUT
THE COLUMN ABOVE 900MB...BRING LIGHT WINDS...AND TRY TO ERODE THE
LOW LEVEL CLOUD DECK. UNFORTUNATELY...THE PEAKS OF SUN WILL DO
LITTLE TO THE THERMAL FIELD RESULTING IN HIGH TEMPS IN THE LOW/MID
30S.

THANKSGIVING WILL START WITH H85 TEMPS IN THE -10 TO -15C RANGE AS A
500 MB TROUGH AXIS SWINGS THROUGH. A LOBE OF POTENTIAL VORTICITY
COINCIDENT WITH PEAK DIURNAL EFFECTS WILL HELP KICK UP A LAKE EFFECT
SNOW RESPONSE. FLOW GENERALLY FROM THE NORTHWEST WILL KEEP ALL OF
SOUTHEAST MICHIGAN GAME FOR BANDING TO SETUP. HAVE A BROAD BRUSH
HALF INCH OF ACCUMULATIONS ACROSS THE AREA...BUT AS WE APPROACH
THURSDAY WILL BE ABLE TO PIN DOWN LOCATION OF LOW LEVEL CONVERGENCE
AND STEERING FLOW A BIT BETTER. AS OF NOW, BETTER ACCUMS SHOULD STAY
NW OF THE GLACIAL RIDGE. THE REMAINDER OF THE EXTENDED FORECAST WILL
BE WELL BELOW NORMAL FOR TEMPS /SAVE SATURDAY/ WITH LOW CONFIDENCE
ON ANY PARTICULAR SNOW CHANCE.

&&

.MARINE...

A STRONG LOW PRESSURE SYSTEM THAT PASSED THROUGH NORTHERN MICHIGAN
IS NOW ENTERING WESTERN QUEBEC. COMBINATION OF COLD AIR ENTERING THE
REGION AND A TIGHT PRESSURE GRADIENT IS RESULTING IN A WIDESPREAD
WIND EVENT ACROSS THE GREAT LAKES. MOST MARINE ZONES ARE
EXPERIENCING HIGH END GALE FORCE WINDS WITH THE EXCEPTION OF LAKE
ERIE WHICH HAS STORM FORCE. THIS PATTERN WILL CONTINUE THROUGH THE
OVERNIGHT...ESPECIALLY OVER CENTRAL LAKE HURON...AS TROUGHING WILL
LINGER EVEN AS THE LOW CONTINUES TO LIFT NORTHEAST. CURRENT
HEADLINES WILL REMAIN UNCHANGED AS THE EVENT IS UNDERWAY AND THE
FORECAST IS ON TARGET. LOW WATER ADVISORY ALSO REMAINS IN EFFECT FOR
LAKE ERIE AS SOUTHWEST FLOW WILL DROP WATER LEVELS SEVERAL FEET BELOW
DATUM. DESPITE THE SOUTHWEST GALES OVER SAGINAW BAY...THE FORECASTED
WATER LEVEL IS PROGGED TO REMAIN JUST ABOVE CHART DATUM...BOTTOMING
OUT LATE THIS EVENING. WINDS WILL DIMINISH RATHER QUICKLY OVERNIGHT
WITH ONLY OPEN WATERS OF LAKE HURON STILL HOLDING ON TO GALES. HIGH
PRESSURE WILL START TO BUILD INTO THE REGION TUESDAY FROM THE SOUTH
WHICH WILL RESULT IN DECREASING WINDS THROUGH MID WEEK.

&&

.AVIATION...ISSUED 1242 PM EST MON NOV 24 2014

//DISCUSSION...

SURGE OF HIGHER WINDS WORKING ACROSS THE DETROIT METRO AREA AT
THIS HOUR...WITH A QUICK INCREASE IN GUSTS TO NEAR 45 KT LIKELY IN
THE NEAR TERM. WINDS WILL THEN RAMP UP IN A NORTHWARD
FASHION...SPREADING INTO MBS LATEST. EXPECT STRONG WINDS WITH
GUSTS UP TO 45 KT TO PERSIST INTO THE LATE AFTERNOON/EVENING
HOURS AFTER THIS SURGE...HIGHEST FROM PTK SOUTH. CEILINGS WILL
DROP BACK TO MVFR BASED ON UPSTREAM OBS AND HOLD THROUGH MUCH OF
THE NIGHT. PRECIP SHIELD NOW OVER SW LOWER MI WILL WORK ITS WAY
INTO MBS THIS AFTERNOON...WITH ACCOMPANYING IFR CIGS FOR A TIME.
COLDER AIR FILTERING IN BEHIND THIS SYSTEM WILL CAUSE RAIN TO
CHANGE TO SNOW FOR MBS...BUT BY THAT TIME THE MAIN AREA OF FORCING
IS EXPECTED TO BE OFF TO THE NORTH AND WEST SO DID NOT INCLUDE A
MENTION OF SN FOR MBS. WINDS WILL DIMINISH SLOWLY OVERNIGHT AS
SURFACE LOW PULLS AWAY.

FOR DTW...WIND GUSTS TO 45 KT...PERHAPS BRIEFLY 50 KT...WILL
CONTINUE INTO THE LATE AFTERNOON/EARLY EVENING. EXPECTED WIND
DIRECTION OF 230 DEGREES WILL MITIGATE CROSSWIND CONCERNS ON THE
NNW/SSE RUNWAYS. ANY BRIEF LIFTING OF THE CEILINGS EARLY THIS
AFTERNOON WILL QUICKLY BE FILLED IN BY MVFR STRATUS FOR THE REST
OF THE DAY INTO THE NIGHT. WINDS WILL BEGIN TO DECREASE AFTER
AROUND 00Z...BUT GUSTS TO NEAR 30 KT WILL STILL BE POSSIBLE INTO
THE EARLY OVERNIGHT HOURS.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5000 FEET TONIGHT THROUGH
  TONIGHT

* HIGH CONFIDENCE IN WIND GUSTS NEAR 45 KT INTO THIS EVENING...BUT
  WIND DIRECTION OF 230 DEGREES WILL MITIGATE CROSSWIND CONCERNS
  ON NNW/SSE RUNWAYS

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...HIGH WIND WARNING UNTIL 10 PM EST THIS EVENING FOR MIZ075-076-082-
     083.

     WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR MIZ047>049-053>055-
     060>063-068>070.

LAKE HURON...GALE WARNING UNTIL 11 AM EST TUESDAY FOR LHZ363-462>464.

     GALE WARNING UNTIL 5 AM EST TUESDAY FOR LHZ421-422-441>443.

     GALE WARNING UNTIL 5 AM EST TUESDAY FOR LHZ362.

LAKE ST CLAIR...GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...LOW WATER ADVISORY UNTIL 4 PM EST TUESDAY FOR LEZ444.

     STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR LEZ444.

&&

$$

SHORT TERM...DT
LONG TERM....DRK/MM
MARINE.......DRK
AVIATION.....DT


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



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