Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 021109
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
609 AM EST TUE FEB 2 2016


.AVIATION...

EARLIER NORTHEAST FLOW OFF LAKE HURON AIDED IN SOME MVFR/IFR STRATUS
DEVELOPMENT ACROSS THE THUMB AND SAGINAW VALLEY. THE LOW LEVEL FLOW
HAS TURNED TOWARD THE E-SE WHICH SHOULD HALT THE SOUTHERN PROGRESS
OF THESE LOW CLOUDS. THE LOW LEVEL SE FLOW WILL INCREASE DURING THE
MORNING WHICH SHOULD LIFT THE REMNANT LOW CLOUDS TO THE NORTH...
EXITING MBS AROUND 15Z. EASTERLY SURFACE WINDS WILL INCREASE DURING
THE COURSE OF THE DAY WITH THE APPROACH OF THE LOW PRESSURE SYSTEM.
DAYTIME MIXING DEPTHS SHOULD BE GREAT ENOUGH TO SUPPORT GUSTS OVER
25 KNOTS AT TIMES LATE THIS AFTERNOON AND EVENING. THE RAIN
/POSSIBLY MIXED WITH SLEET AT MBS/ WILL ARRIVE AT THE TERMINALS
BETWEEN 21Z AND 23Z. ONCE THE RAIN ARRIVES...CEILINGS WILL UNDERGO A
RAPID LOWERING TO IFR /POSSIBLY LIFR/ DURING THE EVENING.

FOR DTW...RECENT SATELLITE DATA SUGGEST THE LOW STRATUS DECK WILL
REMAIN NORTH OF METRO THIS MORNING. DRY LOW LEVEL AIR ACROSS THE
OHIO VALLEY WILL MAINTAIN HIGH CLOUD BASES INTO LATE AFTERNOON. THE
EASTERLY WINDS WILL HOWEVER BEGIN A STEADY INCREASE AFTER 14 OR 15Z.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CLOUDS BELOW 5000 FT LATE THIS AFTERNOON THROUGH TONIGHT.

* MODERATE FOR EASTERLY WIND GUSTS EXCEEDING CROSS WIND THRESHOLDS
  LATE THIS AFTERNOON AND EVENING.

* HIGH IN PRECIP TYPE BEING ALL RAIN THIS AFTERNOON AND TONIGHT.

* LOW IN THUNDERSTORMS AFFECTING THE REGION THIS EVENING.

&&

.PREV DISCUSSION...ISSUED 340 AM EST TUE FEB 2 2016

DISCUSSION...

QUIETER CONDITIONS...OUTSIDE OF SOME FOG EARLY THIS MORNING...WILL
HOLD THROUGH AT LEAST THE EARLY AFTERNOON BEFORE PRECIP QUICKLY
TAKES OVER. A STRONG LOW PRESSURE SYSTEM LOCATED OUT OVER THE
SOUTHERN PLAINS IS CURRENTLY UNDERGOING CYCLOGENESIS AND WILL
CONTINUE TO DEEPEN AS IT MOVES NORTHEAST TODAY.  HIGH CLOUDS
FILTERING IN FROM THE SOUTHWEST WILL INCREASE IN COVERAGE GOING
THROUGH THE MORNING AHEAD OF THE APPROACHING SYSTEM. AS THIS LOW
MOVES UP TOWARDS THE GREAT LAKES AREA...UPPER LEVEL DYNAMICS WILL
ALSO COME TOGETHER AS CORE OF JET STREAK MOVES UP OVER LOWER
MICHIGAN.  MAIN WINDOW FOR ONSET OF PRECIP IS BETWEEN 21Z AND
00Z...WITH THE BULK OF THE PRECIP EXPECTED TO FALL OVERNIGHT
TONIGHT.  CHALLENGE WITH THIS SYSTEM IS THE PTYPE OVER FAR NORTHERN
PARTS OF THE CWA.  LOCATIONS SOUTH WILL REMAIN ABOVE FREEZING FOR
THE MAIN BULK OF THE PRECIP WITH ALL RAIN AS THE PTYPE.
EAST/SOUTHEAST FLOW INCREASES THROUGHOUT THE DAY AND WITH THE ONSET
OF PRECIP LATER IN THE DAY WILL BE LOOKING AT A BETTER CHANCE FOR
SLEET IN THOSE AREAS TO THE NORTH AS TEMPS HOVER AROUND FREEZING.
EVAPORATIVE COOLING ALSO AIDS IN THE WINTER PTYPE ISSUES BEFORE
SOUTHERLY FLOW PICKS UP RESULTING IN CHANGING EVERYTHING OVER TO ALL
RAIN AROUND MIDNIGHT TONIGHT.

THIS DYNAMIC SYSTEM NOT ONLY BRINGS IN ISSUES WITH PTYPE...IT ALSO
BRINGS IN GUSTY WINDS AND A CHANCE FOR A FEW RUMBLES OF THUNDER. SPC
CONTINUES TO HIGHLIGHT MOST OF THE CWA IN GENERAL THUNDER.  HAVE
KEPT MENTION OF THUNDER IN THE FORECAST SINCE THERE ARE STILL
MARGINAL SHOWALTER VALUES AND A COUPLE HUNDRED J/KG OF 0-3KM MUCAPE
THAT SUPPORT THIS.  TRACK OF THE LOW IS STILL ON TARGET TO MOVE
NORTHEAST OVER NORTHWEST LOWER MICHIGAN TONIGHT.  THE TIGHTENING
PRESSURE GRADIENT AHEAD OF THE LOW WILL BRING IN GUSTY WINDS LATER
THIS AFTERNOON BEFORE WINDS SETTLE DOWN AS THE CENTER OF THE LOW
MOVES THROUGH. WINDS PICK UP AGAIN DURING THE DAY ON WEDNESDAY AS
THE PRESSURE GRADIENT TIGHTENS ON THE BACKSIDE OF THE LOW AS IT
MOVES AWAY FROM THE AREA.  PRECIP QUICKLY CUTS OFF FROM WEST TO EAST
AS DRY SLOT WORKS IN AROUND 12Z WEDNESDAY.  SURFACE COLD FRONT LAGS
BEHIND THE DRY SLOT AND IS EXPECTED TO MOVE ACROSS LOWER MICHIGAN
AROUND 00Z THURSDAY.  SOME WRAP AROUND MOISTURE WILL LINGER BEHIND
THE FRONTAL PASSAGE BRINGING A CHANCE FOR SCATTERED SNOW SHOWERS
WITH THE WEST/NORTHWEST FLOW.

CALMER WEATHER CONDTIONS TAKE OVER FOR THE END OF THE WEEK AS WEAK
RIDGING BUILDS IN BRIEFLY.  TROUGHING OVER THE REGION HOLDS THROUGH
THE WEEKEND AS A WEAK UPPER LEVEL WAVE MOVES ACROSS THE NORTHERN
GREAT LAKES THIS WEEKEND.  MODELS ARE THEN SHOWING A MORE PROMINENT
LONGWAVE TROUGH DIGGING SOUTHWARD BY EARLY NEXT WEEK.

MARINE...

EASTERLY WINDS WILL INCREASE DURING THE DAY AS A RESULT OF A
TIGHTENING GRADIENT BETWEEN LOW PRESSURE LIFTING INTO THE MIDWEST
AND HIGH PRESSURE ANCHORED OVER EASTERN CANADA. THERE WILL BE A
SHALLOW UNSTABLE LAYER OVER LAKE HURON WHICH WILL SUPPORT SOME GUSTS
TO GALE FORCE OVER PORTIONS OF THE LAKE. THE TIME PERIOD OF
STRONGEST WINDS WILL BE FROM 5 PM THIS EVENING UNTIL ROUGHLY 2 AM
TONIGHT. WARMER AIR ADVANCING ACROSS LAKE ERIE WILL LIKELY RESULT IN
VERY HIGH STABILITY AND THUS MAKE IT MUCH LESS LIKELY THAT GALE FORCE
WIND GUSTS WILL BE ABLE TO MAKE IT TO THE SURFACE ON LAKE ERIE. THE
SURFACE LOW WILL MOVE INTO THE WESTERN GREAT LAKE TONIGHT ALREADY
OCCLUDING. THE GRADIENT WILL ACTUALLY RELAX CONSIDERABLY AS THE LOW
APPROACHES...LEADING TO WEAKENING WINDS LATE TONIGHT INTO WEDNESDAY
MORNING. THE LOW IS FORECAST TO TRACK ACROSS NORTHERN LAKE HURON
WEDNESDAY AFTERNOON BEFORE LIFTING INTO CANADA WED NIGHT.
STRENGTHENING SOUTHWEST WINDS WILL RESULT /ESPECIALLY ACROSS THE SRN
HALF OF THE LAKE/ AS THIS LOW PASSES THROUGH. THERE IS REASONABLY
HIGH PROBABILITY THAT THE SOUTHWEST WIND GUSTS WILL REACH 25 TO 30
KNOTS. THERE IS A CHANCE THAT WIND GUSTS MAY REACH GALE FOR A SHORT
PERIOD WED AFTERNOON AND EVENING.

HYDROLOGY...

STRONG GULF OF MEXICO MOISTURE TRANSPORT AHEAD OF A LOW PRESSURE
SYSTEM WILL SUPPORT WIDESPREAD RAIN LATE THIS AFTERNOON INTO
TONIGHT. THE HEAVIEST RAINFALL IS EXPECTED TO OCCUR AFTER 4 PM AND
PERSIST THROUGH LATE EVENING...WITH SOME SNOW AND SLEET EXPECTED AT
THE ONSET ACROSS THE SAGINAW VALLEY AND THUMB. THERE IS HIGH
CONFIDENCE THAT TOTAL RAINFALL AMOUNTS FROM THIS AFTERNOON THROUGH
TONIGHT WILL RANGE FROM A HALF INCH TO THREE QUARTERS OF AN INCH.
THERE IS A CHANCE FOR SOME BRIEF PERIODS OF HIGHER INTENSITY
RAINFALL THIS EVENING. THIS MAY SUPPORT SOME LOCALLY HIGHER RAINFALL
TOTALS...POSSIBLY UP TO AN INCH.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING FROM 7 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR
     LHZ361>363-462.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....SC
DISCUSSION...SS
MARINE.......SC
HYDROLOGY....SC


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


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