Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 112253
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
653 PM EDT THU SEP 11 2014


.AVIATION...

//DISCUSSION...

MOISTURE TRAPPED IN A STRONG INVERSION HAS BROUGHT A CONTINUED MVFR
DECK OVER ALL OF SOUTHEAST MICHIGAN THIS EVENING. WINDS WILL EASE
A BIT TONIGHT AS FLOW TURNS NORTHEASTERLY OFF OF LAKE HURON. THE
RESULTANT CONTINUED MOIST ADVECTION IS EXPECTED TO ENSURE
PERSISTENCE OF STRATUS THROUGH THE OVERNIGHT PERIOD. CIGS MAY RISE A
BIT THROUGH DAYTIME HEATING FRIDAY MORNING TO AROUND 3500
FT...HOWEVER CONFIDENCE IN THIS SCENARIO IS NOT PARTICULARLY HIGH.

FOR DTW...SOME VARIATION IN CEILINGS IS EXPECTED, AND THEY MAY
ACTUALLY RISE A BIT TONIGHT DUE TO WARMER NORTHEAST FETCH COMING OFF
OF LAKE HURON. HOWEVER THE PERSISTANCE OF THE MVFR STRATUS
THROUGHOUT THE DAYTIME HOURS DOES NOT LEND ITSELF TO HIGH CONFIDENCE
THAT CIGS WILL IMPROVE ABOVE 3K FT TONIGHT.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET DURING THE TAF PERIOD.

&&

.PREV DISCUSSION...ISSUED 345 PM EDT THU SEP 11 2014

SHORT TERM...TONIGHT

THE SHARP INVERSION ON THIS MORNING`S 12Z DTX SOUNDING HAS SUPPORTED
A SOLID COVERAGE OF STRATUS THROUGH THE AFTERNOON. AT THE BEST, THE
INVERSION SHOULD REMAIN STRONG ENOUGH SUPPORT MOST OF THE PREEXISTING
STRATUS THROUGH THE BULK OF THE OVERNIGHT PERIOD. AT WORST, WINDS
VEERING TO THE NORTHEAST AROUND THE EASTERN PERIPHERY OF THE SURFACE
HIGH TO OUR NORTH WILL AUGMENT THE STRATUS DECK AS A MOIST UNSTABLE
FETCH DEVELOPS OVER SOUTHERN LAKE HURON. EVEN THE NWP, WHICH
ROUTINELY FAIL TO ADEQUATELY HANDLE TIGHT VERTICAL THERMAL PROFILES
OF THIS NATURE, SUPPORT A CONTINUATION OF STRATOCU THROUGH THE
NIGHT. AS A RESULT, LOW TEMPERATURES HAVE BEEN RAISED SEVERAL
DEGREES TO ACCOUNT FOR EXPECTED PERSISTENCE OF BOUNDARY LAYER CLOUDS.

SECONDARY FORECAST ISSUE IS THE POTENTIAL FOR LAKE EFFECT TONIGHT.
CURRENT VISIBLE IMAGERY INDICATES A DOMINANT BAND IN THE PREFERRED
CONVERGENT CORRIDOR JUST NORTH OF THE THUMB STREAMING INTO THE
ONTARIO PENINSULA. THE EXETER RADAR IS SHOWING LIGHT RETURNS
ASSOCIATED WITH THIS BAND. AS NWLY BOUNDARY LAYER FLOW VEERS TO NELY
OVERNIGHT, THIS BAND WILL MIGRATE TOWARD THE THUMB AND POTENTIALLY
BRING A ROUND OF LIGHT SHOWERS AS IT MAKES LANDFALL. 12Z NWP ALSO
INDICATE ADDITIONAL LAKE EFFECT DEVELOPMENT AS BOUNDARY LAYER
CONVERGENCE INCREASES IN THE THUMB IN ASSOCIATION WITH EMERGING
NORTHEAST FLOW. THIS SEEMS REASONABLE GIVEN MODEST 0-1KM THETA-E
LAPSE RATES OF -5C TO -8C AND A RESPECTABLE FETCH. CONTINUED WITH
CHANCE POPS FROM I-69 NORTH AND INCREASED TO 40 POP ALONG THE
IMMEDIATE SHORELINE AND INTERIOR THUMB REGION.

LONG TERM...FRIDAY THROUGH WEDNESDAY

BROAD UPPER LEVEL TROUGHING ACROSS THE CENTRAL PLAINS AND GREAT
LAKES WILL MOVE LITTLE THROUGH THE WEEKEND. EXPANSIVE CANADIAN
SURFACE HIGH WILL REACH EASTWARD ACROSS THE STATE FRIDAY BUT WILL
TEMPORARILY BE INTERRUPTED BY A MIDLEVEL SHORTWAVE FRIDAY NIGHT INTO
SATURDAY. AFTER THIS PERIOD OF SHOWERS...THE WESTWARD SEGMENT OF THE
SURFACE HIGH WILL THEN WORK INTO THE AREA SATURDAY EVENING. THIS
WILL KEEP UNSEASONABLY COOL CONDITIONS ACROSS THE REGION INTO NEXT
WEEK.

HIGH PRESSURE WILL MAKE PRECIP DIFFICULT TO COME BY FRIDAY ALTHOUGH
THE RESULTANT NE FLOW OFF LAKE HURON WITH CAA ALOFT...850MB TEMPS
STILL IN THE SINGLE DIGITS C...WILL LEAD TO SOME LAKE EFFECT RAIN
SHOWERS THROUGH THE FIRST HALF OF THE DAY FOR THE THUMB. PLENTY OF
STRATUS WILL BE PRESENT THROUGHOUT THE DAY AS THE STOUT INVERSION
REMAINS IN PLACE TRAPPING THE LL MOISTURE BENEATH THE INVERSION.
MODELS EVENTUALLY ADVECT SOME DRIER AIR IN THE BL WHICH WILL ACT TO
LIFT THE STRATUS TO AROUND 3-4KFT. MID LEVELS WILL MOISTEN IN THE
AFTERNOON AHEAD OF THE APPROACHING SHORTWAVE. THIS WILL BEGIN OVER
THE SAGINAW VALLEY...CONTINUING SOUTHWARD THROUGH THE EVENING. THE
POSITIVELY TILTED WAVE WILL PIVOT TO A NEGATIVE TILT AS IT TRACKS
ACROSS THE REGION. MID LEVEL RIDGING JUST AHEAD OF THE WAVE WILL
KEEP PRECIP MOSTLY SHUT OFF TIL AFTER 00Z WHEN MID LEVEL DIFFLUENCE
MAXIMIZES AND THE CORE OF THE JET DROPS OVER THE AREA. THE PRECIP
WILL LAST THROUGH SATURDAY MORNING...SHUTTING OFF IN THE EARLY
AFTERNOON AS SUBSIDENCE BUILDS OVERHEAD. IN ADDITION...HIGH PRESSURE
BUILDS BACK INTO THE AREA FOR THE REST OF SATURDAY AND SATURDAY
NIGHT.

TEMPERATURES WILL STAY ON THE COOL SIDE OF NORMAL AS 500MB TEMPS IN
THE NEGATIVE TEENS AND 850MB TEMPS HOLD IN THE POSITIVE SINGLE
DIGITS. JUDGING FROM TODAYS STRUGGLES WITH MAX TEMPS...WENT ON THE
COOLER SIDE OF GUIDANCE FOR FRIDAY AND SATURDAY. CLOUD COVER AND
RAIN WILL KEEP FRIDAY NIGHT IN THE MID 40S BUT CLEARING SKIES WITH
HIGH PRESSURE SATURDAY NIGHT SHOULD ALLOW A DROP TO AROUND 40...WITH
LOCALLY COOLER SPOTS DROPPING INTO THE UPPER 30S.

HIGH PRESSURE WILL HOLD THROUGH THE END OF THE WEEKEND BEFORE A
SHORTWAVE TRACKING IN FROM THE NORTH BRINGS THE NEXT ROUND OF
UNSETTLED WEATHER TO THE REGION.  THIS SHORTWAVE WILL BRING
INCREASED RAIN CHANCES OVER THE AREA ON MONDAY BEFORE ANOTHER HIGH
PRESSURE SYSTEM BUILDS BACK IN.  SOUTHEAST MICHIGAN WILL CONTINUE TO
BE BELOW NORMAL IN TERMS OF TEMPERATURES THROUGH THE EXTENDED.

MARINE...

SMALL CRAFT CONDITIONS WILL PERSIST THROUGH THIS EVENING WITH GUSTY
NORTHERLY FLOW AND ELEVATED WAVE HEIGHTS OVER THE NEARSHORE ZONES.
THE WINDS WILL DECREASE OVERNIGHT AS HIGH PRESSURE SETTLES OVER THE
GREAT LAKES. THE WEAK FLOW WILL THEN VEER TO MORE EASTERLY FRIDAY
AFTERNOON. ONE CONCERN FOR TONIGHT IS THE POSSIBILITY OF WATERSPOUTS
AS COOLER AIR RESIDES OVER THE WARMER LAKE WATERS WITH LAKE EFFECT
RAIN BANDS PRESENT. THIS WILL MAINLY AFFECT SOUTHERN LAKE
HURON...INCLUDING SAGINAW BAY...LATE TONIGHT THROUGH FRIDAY MORNING.
THE THREAT WILL END EARLY FRIDAY AFTERNOON AS THE LAKE EFFECT
CEASES. NEXT CHANCE OF RAIN WILL COME FRIDAY NIGHT THROUGH SATURDAY
MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING OUTER SAGINAW BAY...UNTIL 8 PM THURSDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....KURIMSKI
SHORT TERM...JVC
LONG TERM....DRK/SS
MARINE.......DRK


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