Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 282312
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
712 PM EDT SUN SEP 28 2014

.AVIATION...

//DISCUSSION...

DIFFUSE SURFACE HIGH PRESSURE WILL REMAIN IN CONTROL OF THE WEATHER
OVER SE MICHIGAN TONIGHT THROUGH MONDAY MORNING. THIS WILL ONCE
AGAIN PRESENT A SCENARIO FOR FOG DEVELOPMENT WITH ONLY SCATTERED
CIRRUS CLOUDS AND SURFACE DEWPOINT IN THE MID 50S. MODEL FORECAST
SOUNDINGS POINT TO SHALLOW BOUNDARY LAYER MOISTURE DEPTH WHICH TENDS
TO RESULT IN GROUND FOG WITH WIDE SWINGS IN VISIBILITY AND
INCONSISTENT COVERAGE. PLAN TO HOLD THE LINE ON THE MVFR FORECAST
WITH A BRIEF DROP INTO IFR IN PRONE AREAS LIKE FNT AND PTK. LIGHT
WEST WIND AND VFR CONDITIONS WILL SET UP BY LATE MONDAY MORNING
AND LAST THROUGH THE AFTERNOON AHEAD OF A SHARP COLD FRONT
EXPECTED TO REACH MBS BY MONDAY EVENING.

//DTW THRESHOLD THREATS...

* NONE.

&&

.PREV DISCUSSION...ISSUED 335 PM EDT SUN SEP 28 2014

SHORT TERM...THROUGH TONIGHT

ANOTHER QUIET NIGHT IN STORE AS HIGH PRESSURE CONTINUES TO HOLD OVER
THE REGION. SOME CLOUD COVER THIS AFTERNOON...MAINLY CIRRUS DEBRIS
FROM THE UPPER LOW THAT WILL PASS OVER THE AREA TONIGHT...WHICH
SHOULD WANE THROUGH THE EVENING AS DRIER AIR MOVES BACK IN. THIS
WILL OPEN THE DOOR FOR ANOTHER NIGHT OF FOG DEVELOPMENT. MODELS NOT
AS AGGRESSIVE WITH FOG TONIGHT EVEN WITH THE LACK OF CIRRUS WE DEALT
WITH LAST NIGHT. THIS IS LIKELY THE RESULT OF LIGHT LL WINDS
SHIFTING FROM EASTERLY TO NORTHWESTERLY LESSENING THE LAKE MOISTURE
FEED INROADS. STILL ENOUGH RESIDUAL MOISTURE UNDER THE INVERSION
WITH SFC DEWPOINTS THIS AFTERNOON INTO THE MID 50S TO PRODUCE
ANOTHER THIN LAYER OF FOG BY LATE TONIGHT...WHICH IS SUPPORTS BY
HIRES MODELS. LOWS SHOULD DIP TO AROUND 50 TONIGHT...WITH UPPER 40S
IN MORE RURAL AREAS.

LONG TERM...

ELONGATED SHORTWAVE ENERGY CURRENTLY NOTED ON WATER VAPOR SHEARING
ACROSS SOUTHERN MANITOBA WILL STEADILY DEEPEN AS IT EJECTS SOUTHEAST
ACROSS THE NORTHERN GREAT LAKES OVER THE NEXT 36 HOURS...EVENTUALLY
CLOSING OFF AS IT TRACKS ACROSS LAKE HURON BY MONDAY NIGHT.  MODEST
SURFACE RESPONSE TO THE INBOUND HEIGHT FALLS WILL WORK THE ATTENDANT
COLD FRONT THROUGH SE MICHIGAN MONDAY NIGHT.  MOISTURE ADVECTION
WILL LARGELY REMAIN ANCHORED WITH THE FRONTAL PASSAGE AND DURING THE
POST-FRONTAL COLD AIR ADVECTION...LEAVING PLENTY OF SUNSHINE FOR THE
DAYTIME PERIOD ON MONDAY.  A MODERATELY MIXED BOUNDARY LAYER UNDER
SLIGHTLY DEEPER WESTERLY PRE-FRONTAL LOW LEVEL FLOW WITH A SIMILAR
850-925 MB TEMPERATURE PROFILE AS TODAY WILL SUPPORT HIGHS OF MIDDLE
AND UPPER 70S.

12Z MODEL SUITE CONTINUE TO PRESENT A NARROW /3-4 HR/ BUT SOLID
INCREASE IN UPWARD VERTICAL MOTION TIED TO BOTH THE FRONTAL FORCING
AND CYCLONIC VORTICITY ADVECTION MONDAY NIGHT.  MOISTURE QUALITY
WILL RAMP UP AT THE SAME...850 MB DEWPOINTS IN THE 10C RANGE
ATTENDANT TO THE FRONTAL SLOPE.  RECENT TRENDS OF THE NAM AND GFS IN
THE DIRECTION OF THE MORE BULLISH ECMWF LEND CONFIDENCE TOWARD
INCREASING RAINFALL CHANCES DURING THIS TIME.  HIGHEST PROBABILITY
WILL EXIST TOWARD THE NORTH AND EAST...IN CLOSER PROXIMITY TO THE
BEST FORCING.  LOWS RANGING FROM UPPER 40S TO MID 50S MONDAY NIGHT.

STRONG COLD AIR ADVECTION TAKES HOLD LATE MONDAY NIGHT AND INTO
TUESDAY UNDER DEEPER NORTHWEST FLOW.  850 MB TEMPERATURES WILL
BOTTOM OUT IN THE MIDDLE SINGLE DIGITS BY MONDAY AFTERNOON.  THE
COMBINATION OF THE STRONG LOW LEVEL ADVECTIVE COMPONENT AND SOME
RESIDUAL MID LEVEL CYCLONIC FLOW WILL SUSTAIN AN EXTENSIVE STRATUS
DECK BENEATH A STRENGTHENING INVERSION THROUGHOUT TUESDAY.  THIS
WILL CONTRIBUTE TO A SIGNIFICANTLY COOLER DAY...HIGHS RANGING FROM
MID 60S SOUTH TO UPPER 50S NORTH.  LOW LEVEL FLOW WILL VEER TO
NORTHEASTERLY BY TUESDAY NIGHT AS HIGH PRESSURE NOSES IN FROM THE
WEST.  THIS WIND DIRECTION WILL FAVOR SOME DEGREE OF MOISTURE FLUX
OFF LAKE HURON...SUGGESTING THAT A FIRM STRATUS DECK WILL REMAIN
LOCKED IN BENEATH THE INVERSION THROUGH THE NIGHT.

THE LAST SEMBLANCE OF UPPER LEVEL RIDGING WILL BE EVADING SOUTHEAST
MICHIGAN AFTER WEDNESDAY. A COLD FRONT WILL ACCOMPANY MUCH LOWER H5
HEIGHT LEVELS TOWARD THE END OF THE WORK WEEK AS RAIN...BRISK WINDS
..AND COOLER TEMPERATURES SPREAD ACROSS THE REGION. TEMPS WILL
START TO TREND 5 DEGREES BELOW NORMAL INTO THE END OF THE EXTENDED
PERIOD.

MARINE...

PERSISTENT HIGH PRESSURE WILL SUSTAIN A LIGHT WIND FIELD ACROSS THE
MARINE AREAS THROUGH TONIGHT.  SOUTHWEST WINDS WILL DEVELOP ON
MONDAY AS LOW PRESSURE TRACKS ACROSS THE NORTHERN GREAT LAKES.  THIS
LOW WILL SEND A COLD FRONT ACROSS THE REGION MONDAY NIGHT.
INCREASING NORTHERLY WINDS WILL FOLLOW IN THE WAKE OF THIS SYSTEM
MONDAY NIGHT INTO TUESDAY. WINDS WILL THEN GRADUALLY DIMINISH
TUESDAY NIGHT INTO WEDNESDAY AS HIGH PRESSURE BUILDS BACK ACROSS THE
REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
SHORT TERM...DRK
LONG TERM....MR/MM
MARINE.......MR


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