Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241742
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1242 PM EST MON NOV 24 2014


.AVIATION...

//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

&&

.PREV DISCUSSION...ISSUED 1140 AM EST MON NOV 24 2014

UPDATE...
HAVE UPGRADED TO HIGH WIND WARNING FOR SOUTHERN 4 COUNTIES BASED
ON LATEST SATELLITE/SFC OBS. VIS SAT INDICATES CLEAR SLOT
PROGRESSING TO NEAR THE OH/MI BORDER ATTM...CONCIDENT WITH A
SURGE IN WINDS. THIS COINCIDES WITH 12NAM SURGE OF ISENTROPIC
DESCENT WORKING THROUGH THE REGION 16-18Z...ITS LEADING EDGE
AFFECTING AREAS FROM METRO DETROIT SOUTHWARD DURING THAT
TIMEFRAME. EXPECT A BRIEF UPTICK IN STRONG WIND GUSTS WITH THE
PASSAGE /E.G. KFWA WIND GUST TO 50 KT/ FOLLOWED BY THE POTENTIAL
OF PERIODIC GUSTS TO WARNING CRITERIA THROUGHOUT THE AFTERNOON AND
INTO THE EVENING AS DAYTIME MIXING DEEPENS THE BOUNDARY LAYER.
ELSEWHERE...A MORE GRADUAL RAMP- UP OF WINDS EXPECTED...BUT STILL
RELATIVELY GOOD CONFIDENCE IN WIND ADVISORY CRITERIA BEING MET
I-69 SOUTH. UPDATE TO POPS TO REFLECT A SHARPER DRYING TREND POST-
FRONT OVER THE SOUTH...WITH THE SAGINAW VALLEY/NORTHERN THUMB
CATCHING THE DEFORMATION FORCING THIS AFTERNOON NOW EVIDENT OVER
SW LOWER. CATEGORICAL POPS THERE.

PREV DISCUSSION...ISSUED 342 AM EST MON NOV 24 2014

SHORT TERM... TODAY AND TONIGHT

A DYNAMIC MID LEVEL FLOW ANCHORED ALONG THE EASTERN FLANK OF AN
INBOUND HIGHER AMPLITUDE TROUGH NOW EXITING THE PLAINS WILL REMAIN
FIRMLY IN PLACE LOCALLY TODAY.  SUBSTANTIAL INTERACTION OF MULTIPLE
POTENTIAL VORTICITY FILAMENTS WORKING THROUGH THIS FLOW ALREADY
PROMPTING A STEADY DEEPENING OF THE ATTENDANT SURFACE LOW CURRENTLY
POSITIONED NEAR HOLLAND.  THIS LOW REMAINS FORECAST TO DEEPEN AN
ADDITIONAL 6-8 MILLIBARS AS IT PROGRESSES NORTHWARD AND INTO SOUTH
CENTRAL ONTARIO TODAY.  EASTWARD EXTENDING WARM FRONTAL STRUCTURE
WILL EXIT TO THE NORTH IN CONCERT...LEAVING SE MICHIGAN TEMPORARILY
WITHIN A MILDER SOUTHWEST FLOW THROUGH THE LATE MORNING/EARLY
AFTERNOON PERIOD.  GIVEN THAT READINGS ARE ALREADY IN THE MIDDLE AND
UPPER 50S IN SOME LOCALES...NOW LOOKING AT HIGHS PEAKING IN THE 60
DEGREE RANGE ACROSS AT LEAST SOUTHERN SECTIONS DURING THIS TIME.
UPSTREAM RADAR TRENDS SUGGEST THE WEAK WARM AIR ADVECTIVE PROCESS
MAY PROMOTE SOME ADDITIONAL LIGHT SHOWER DEVELOPMENT THROUGH THIS
TIME...STILL WORTHY OF A HIGH END POP.

A ROBUST MID AFTERNOON COLD FRONTAL PASSAGE EXPECTED ACROSS SE
MICHIGAN....STRENGTH OF THE THERMAL GRADIENT SOLIDIFIED BENEATH
STRONG EXIT REGION JET DYNAMICS AND A CONTRACTING/CONSOLIDATING MID
LEVEL HEIGHT FIELD.  A SOLID PERIOD OF 280-290K ISENTROPIC DESCENT
WILL EMERGE WITHIN THE IMMEDIATE WAKE OF THE FRONTAL PASSAGE.  THIS
PROCESS WILL OCCUR IN CONJUNCTION WITH INCREASING ISALLOBARIC
FORCING...RECENT MODEL GUIDANCE DISPLAYING A PRESSURE CHANGE OF
GREATER THAN 8 MB/3 HR ACROSS SOUTHERN AND CENTRAL SECTIONS OF THE
FORECAST AREA CENTERED ON 20Z-00Z.  MIXING POTENTIAL TOUGHER TO
GAUGE...A LOWER CEILING AND PROSPECTS FOR LINGERING PRE-FRONTAL
SHOWERS PERHAPS MUTING THE POTENTIAL SOMEWHAT.  DIMINISHING
INSTABILITY DOES LEAVE THE POSSIBILITY FOR A SHALLOW LINE OF
CONVECTIVE SHOWERS /A RUMBLE OF THUNDER?/ TO EMERGE ALONG THE
FRONTAL INTERFACE...WHICH WOULD IN ITSELF PRESENT A GREATER
POTENTIAL TO TAP INTO THE ELEVATED WIND FIELD. REGARDLESS...CURRENT
SETUP POINTS TOWARD A PERIOD OF EFFICIENT DOWNWARD TRANSPORT OF THE
EXISTING STRONG WINDS JUST OFF THE SURFACE /40-45 KNOTS AT 925 MB/
FROM MID AFTERNOON INTO THE EVENING HOURS.  GIVEN THIS WIND
FIELD...WILL GO AHEAD WITH A WIND ADVISORY FOR ALL LOCATIONS.
GREATEST WIND GUST POTENTIAL /OVER 50 MPH/ WILL EXIST ACROSS
SOUTHERN SECTIONS...THIS CORRIDOR MORE FAVORABLY POSITIONED FOR A
BETTER ISOLLOBARIC RESPONSE AND GREATER MIXING.  NOT ENOUGH EVIDENCE
TO TIP THE SCALES OR LEND CONFIDENCE FOR A WARNING LEVEL RISK AT
THIS STAGE...BUT A SOLID POP OF WIND TIED IMMEDIATELY TO THE FROPA
AND/OR A SHALLOW CONVECTIVE LINE COULD GENERATE A FEW HIGH END
ADVISORY GUSTS.

ENSUING COLD AIR ADVECTION TAKES HOLD RIGHT THROUGH TONIGHT...A GOOD
15C 24 HOUR DROP IN TEMPERATURES ACROSS THE 850-925 MB LAYER BY
DAYBREAK.  THIS WILL BRING LOWS DOWN INTO THE UPPER 20S/LOWER 30S.
TRAILING DEFORMATION NOW APPEARS TO HOLD JUST TO THE NORTHWEST AS
THE THERMAL PROFILE PLUMMETS THROUGH A GOOD PORTION OF THE
NIGHT...ONLY THE TRI-CITIES AT THE CUSP OF A FADING FORCING FIELD
EXPECTED TO WASH BACK IN LATE TONIGHT.  RATHER MODEST LOOKING LAKE
RESPONSE TONIGHT SUGGESTS A LIMITED IMPACT FOR OUR DOWNSTREAM
POSITION...AGAIN THE EXISTING SOUTHWEST OR WEST-SOUTHWEST GRADIENT
DIRECTING THE MOISTURE FLUX INTO THE TRI-CITIES.  THIS WILL
TRANSLATE INTO SOME MINOR ACCUMULATION THROUGH THIS CORRIDOR...
PERHAPS UP TO AN INCH BY MID MORNING.  ELSEWHERE...POTENTIAL FOR A
FEW SNOW SHOWERS DURING THE LATTER HALF OF THE NIGHT GIVEN ADEQUATE
MOISTURE DEPTH AND LAPSE RATES WITHIN THE EXISTING STRATUS
DECK...LITTLE OR NO ACCUMULATION EXPECTED.

LONG TERM...

LINGERING SURFACE TROUGHING/CYCLONIC FLOW ON TUESDAY OVER THE
CENTRAL GREAT LAKES...WITH 850 MB TEMPS OF -10 TO -12 C...WHICH IS
NOT IDEAL FOR SNOW SHOWER ACTIVITY. STILL...THERE IS MOISTURE UP AT
700 MB...AS COLD POOL OF -14 TO -15 C WORKS THROUGH...AND WITH SOME
ENHANCEMENT OFF LAKE MICHIGAN...SCATTERED TO NUMEROUS LIGHT SNOW
SHOWERS ARE EXPECTED WITH STEEP BUT SHALLOW LOW LEVEL LAPSE RATES.
925 MB TEMPS OF -4 TO -5 C SUPPORT MAXES IN THE MID 30S.

PRONOUNCED SURFACE RIDGING AND WARMING OF THE MID LEVELS WILL ATTEMPT
TO SCOUR OUT CLOUDS TUESDAY NIGHT...BUT EURO/NAM STILL INDICATING
HIGHER RH (80+ PERCENT) AT 925 MB (RIGHT UNDERNEATH THE SUBSIDENCE
INVERSION)...AND WILL CALL FOR PARTIAL CLEARING AT THIS POINT...AND
CONSERVATIVE MINS FORECAST IN THE LOWER 20S. WITH BETTER CLEARING AND
FAVORABLE RADIATING CONDITIONS...POTENTIAL FOR TEENS...ESPECIALLY
IF WE CAN GET SOME TYPE OF SNOW COVER FROM TONIGHT/TOMORROW.

COMPACT BUT INTENSE UPPER WAVE/PV CENTER ON WEDNESDAY IS PROGGED TO
TRACK WELL SOUTH (MISSOURI/ALONG OR SOUTH OF OHIO RIVER)...AND IT
LOOKS LIKE IT WILL END UP DRY (PARTIAL SUNSHINE) AS EAST COAST STORM
IS TOO FAR TO THE EAST AS WELL. NORTHERN STREAM TROUGH AXIS AND
ASSOCIATED COLD FRONT WILL BE ARRIVING THURSDAY MORNING...WITH
COLDER AIR TO FOLLOW (850 MB TEMPS BACK INTO THE MID NEGATIVE
TEENS)...SUFFICIENT TO GET SOME (SCATTERED) LAKE ENHANCED SNOW
SHOWER ACTIVITY GOING.

MARINE...

STRONG LOW PRESSURE CURRENTLY MOVING THROUGH LOWER MICHIGAN EARLY
THIS MORNING. AS THE SYSTEM LIFTS NORTHEAST INTO ONTARIO THIS
AFTERNOON...SOUTHWEST GALES ARE EXPECTED AS MUCH COLDER AIR FILTERS
INTO THE CENTRAL GREAT LAKES. THE STRONGEST WINDS
LOOK TO BE FOCUSED ACROSS CENTRAL AND SOUTHERN PORTIONS OF LAKE
HURON EARLY THIS EVENING...WITH BRIEF GUSTS TO STORM FORCE NOT OUT
OF THE QUESTION. GALE WARNINGS WILL BE ISSUED FOR ALL MARINE AREAS
WITH THIS FORECAST PACKAGE. 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 JUST SOME MARGINAL LINGER GALES OVER
THE OPEN WATERS OF SOUTHERN LAKE HURON TUESDAY MORNING. SURFACE
RIDGE BUILDING INTO THE AREA TUESDAY NIGHT WILL CONTINUE TO LEAD TO
DIMINISHING WINDS...WITH LIGHT WINDS AROUND FOR WEDNESDAY.

&&

.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 MIZ055-060>063-
     068>070.

     WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR MIZ047>049-053-054.

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

     GALE WARNING UNTIL 5 AM EST TUESDAY FOR LHZ441>443.

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

     GALE WARNING FROM 6 PM THIS EVENING TO 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.

&&

$$

AVIATION.....DT
UPDATE.......DT
SHORT TERM...MR
LONG TERM....SF
MARINE.......SF


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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