Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 022258
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
558 PM EST TUE FEB 2 2016


.AVIATION...

RAIN SHOWERS WILL OVERSPREAD THE AREA THIS EVENING...BECOMING MORE
NUMEROUS WITH TIME. SNOW/SLEET WILL MIX WITH AND CHANGE TO SHRA 00Z-
02Z. EXPECT LOWER VFR/MVFR CIGS TO LOWER TO IFR AT TIMES TONIGHT AS
MOISTURE INCREASE ACROSS THE AREA AS ENE FLOW VEERS TO THE SOUTH AND
THEN SSW. CIGS WILL THEN RISE AND BECOME MORE BKN ON WEDNESDAY AS
DRY SLOT WORKS INTO AREA AROUND 12Z AROUND PASSING LOW PRESSURE.
INCREASING COLD POOL OF AIR WILL THEN WORK EAST INTO AREA AND LEAD
TO SCT SHRASN BY AFTERNOON WITHIN GUSTY SW FLOW IN ADVANCE OF TROUGH
AXIS.

FOR DTW...RAIN WILL PREDOMINATE THE FORECAST THIS EVENING. INITIAL
CLUSTER OF ENHANCED SHOWERS EARLY MAY ALSO CONTAIN A RUMBLE OR TWO
OF THUNDER THROUGH 01Z OR SO. CIGS WILL TREND FROM VFR TO MVFR AND
THEN IFR AT TIMES OVERNIGHT WITHIN MOISTENING SOUTHERLY FLOW. COLD
FROPA WILL BRING SSW FLOW BY 12Z WITH SHRAS ENDING AND CIGS RISING
THEREAFTER.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIGS AT OR BELOW 5000 FT MUCH OF THE FORECAST.

* LOW FOR EASTERLY WIND GUSTS EXCEEDING CROSS WIND THRESHOLDS
  EARLY THIS EVENING.

* HIGH IN PRECIP TYPE BEING ALL RAIN TONIGHT.

* LOW CONFIDENCE IN THUNDERSTORMS DIRECTLY IMPACTING TERMINAL
  EARLY THIS EVENING.

&&

.PREV DISCUSSION...ISSUED 515 PM EST TUE FEB 2 2016

UPDATE...

UPDATED TO INCLUDE A PERIOD OF SLEET AND SNOW FROM THE SAGINAW
VALLEY INTO THE NORTHERN THUMB. EVAPORATIVE COOLING WILL MAINTAIN
A NARROW BAND OF FROZEN PRECIPITATION FOR A FEW HOURS EARLY THIS
EVENING BEFORE THE TRANSITION TO RAIN OCCURS. WHILE MOST OF THIS
PRECIPITATION WILL BE ON THE LIGHT SIDE...SOME ENHANCED AREAS
NOTED ON AREA 88DS SUGGEST UP TO HALF AN INCH OF SNOW WILL BE
POSSIBLE BEFORE THE CHANGE TO RAIN. THIS MINOR ACCUMULATION WILL
BE MOST LIKELY OVER THE NORTHERN SAGINAW VALLEY AND WILL BE
CONFINED TO MAINLY GRASSY SURFACES GIVEN CURRENT SURFACE OBS HAVE
TEMPERATURES ABOVE FREEZING.

PREV DISCUSSION...ISSUED 326 PM EST TUE FEB 2 2016

DISCUSSION...

DYNAMIC MID LEVEL CLOSED SYSTEM AT PEAK INTENSITY THIS AFTERNOON
WILL RAPIDLY LIFT NORTHEAST FROM THE CENTRAL PLAINS INTO THE UPPER
MS VALLEY THROUGH TONIGHT.  WELL DEFINED DEEP LAYER MOISTURE PLUME
ANCHORED WITHIN A FIELD OF STRENGTHENING WARM AIR ADVECTION
IMMEDIATELY DOWNSTREAM ON TRACK TO RAPIDLY EXPAND INTO SE MICHIGAN
DURING THE EVENING PERIOD.  THIS MOISTURE SURGE BACKED BY A SOLID
PERIOD OF LOW AND MID LEVEL FORCING...DRIVEN BY A COMBINATION OF
STRONG ISENTROPIC ASCENT AND UPPER JET DYNAMICS/DIFFLUENCE.  AN
ADDED ELEMENT OF WEAK MID LEVEL INSTABILITY GIVEN THE MAGNITUDE OF
THIS INBOUND THETA-E ENVIRONMENT WILL CONTRIBUTE TO A GOOD SOAKING
RAINFALL AREAWIDE...WITH THE POSSIBILITY OF A FEW RUMBLES OF
THUNDER. RAINFALL AMOUNTS OF .5 TO .75".  ONSET MAY PROVIDE A VERY
BRIEF PERIOD OF ICE PELLETS/SLEET AREAWIDE AS WET BULBING COMMENCES.
OTHERWISE LOOKING AT A QUICK PROGRESSION TOWARD ALL RAIN AS
SATURATION DEEPENS. A FIRM SOUTHEAST WIND WILL EMERGE FOR A TIME
THIS EVENING AS THE GRADIENT BRIEFLY STRENGTHENS. A DEEP LAYER OF
STABILITY BELOW 850 MB WILL LIKELY CAP THE GUST MAGNITUDE POTENTIAL
/35 MPH OR LESS/ DESPITE THE STRONG WIND FIELD RESIDING JUST OFF THE
SURFACE /40+ KNOTS ABOVE 1500 FT/.  INTRUSION OF THE MATURE MID
LEVEL DRY SLOT AND ACCOMPANYING PASSAGE OF THE COLD/OCCLUDED FRONT
WILL SCOUR THIS MOISTURE OUT FROM WEST TO EAST THROUGH THE EARLY-MID
MORNING PERIOD.TODAY.


A WARMING THERMAL PROFILE TONIGHT WILL LEAVE TEMPERATURES QUITE MILD
WEDNESDAY MORNING...WITH READINGS IN THE 40S /NEAR 50 SOUTH/.  A
LIMITED DEGREE OF COLD AIR ADVECTION WITH THIS LEAD FRONTAL PASSAGE
WILL SEEMINGLY DO LITTLE TO OFFSET AN INCREASINGLY MIXED
SOUTHWESTERLY FLOW.  THIS CONTINUES TO SUPPORT FAVORING THE WARMER
END OF THE GUIDANCE SPECTRUM...WITH WELL ABOVE NORMAL READINGS
LIKELY HOLDING FIRM THROUGH THE DAY /MID 40S NORTH TO LOWER 50S
SOUTH/. THIS PROFILE WILL FAVOR GUSTY CONDITIONS...TOPPING OUT IN
THE 30 TO 35 MPH RANGE DURING THE AFTERNOON.  LITTLE SUPPORT FOR
PRECIPITATION DEVELOPMENT UNTIL LATE AFTERNOON/EVENING...BOTH
MOISTURE DEPTH AND FORCING LACKING DURING MUCH OF THE DAYLIGHT
PERIOD.  MAIN HEIGHT FALL GRADIENT WILL FINALLY SHIFT EAST BY
WEDNESDAY EVENING...AN ACCOMPANYING INCREASE IN BOTH COLD AIR
ADVECTION AND MOISTURE DEPTH DURING THIS TIME.  SETUP SUFFICIENT TO
DELINEATE A LOW END POP FOR SNOW SHOWERS AREAWIDE WEDNESDAY
EVENING...AND ACROSS SOUTHERN SECTIONS INTO THE OVERNIGHT PERIOD AS
MOISTURE FLUX INCREASES OFF LAKE MICHIGAN IN COLDER WEST-NORTHWEST
FLOW.

THE EXISTING THERMAL/MOISTURE PROFILE MAY PROVE ADEQUATE ENOUGH WITH
SOME DIURNAL ASSISTANCE TO SUSTAIN A FEW LIGHT SNOW SHOWERS OR
FLURRIES THROUGH THURSDAY...BUT NOTHING OF REAL CONSEQUENCE GIVEN
THE MARGINAL OVERLAKE INSTABILITY AND WEAKLY FORCED RESIDUAL MID
LEVEL CYCLONIC FLOW. A NOTEWORTHY DOWNWARD TREND IN TEMPERATURES
THURSDAY IN LIGHT OF THE RECENT WARMTH...BUT WITH DAYTIME READINGS
STILL RIGHT AROUND EARLY FEBRUARY NORMS /LOWER 30S/.

HIGH PRESSURE REMAINS OVER THE REGION ON FRIDAY BEFORE DRIFTING
SOUTHEASTWARD BY FRIDAY NIGHT WHICH WILL RESULT IN THE REGION
REMAINING DRY. WEAK LOW PRESSURE WILL TRACK ACROSS THE NORTHERN
GREAT LAKES ON SATURDAY...BRINGING SOME SNOW SHOWERS MAINLY TO THE
NORTHERN CWA. LITTLE TO NO ACCUMULATION IS EXPECTED AT THIS TIME. A
WEAK RIDGE OF HIGH PRESSURE RETURNS FOR SATURDAY NIGHT AND INTO
SUNDAY BEFORE THE NEXT LOW PRESSURE SYSTEM MOVES IN ON SUNDAY NIGHT.
THIS SYSTEM WILL TRACK SOUTHEASTWARD OUT OF THE NORTHERN PLAINS AND
SETTLE OVER THE GREAT LAKES BY MONDAY. TEMPERATURES WILL BE COLD
ENOUGH TO PRODUCE SOME SNOW WITH THIS SYSTEM...HOWEVER IT IS TOO
EARLY TO DETERMINE AMOUNTS AT THIS TIME.

MARINE...

EASTERLY WINDS WILL CONTINUE TO RAMP UP THIS AFTERNOON INTO THIS
EVENING AS LOW PRESSURE TRACKS THROUGH THE WESTERN GREAT LAKES
TONIGHT. GALE WARNINGS CONTINUE FOR THE NORTH OF LAKE HURON...WITH
SMALL CRAFT ADVISORIES FOR SOUTH HALF OF LAKE HURON...WHERE WINDS
WILL SHIFT TO THE SOUTH OVERNIGHT. LIGHTER WINDS EXPECTED TOMORROW
MORNING AS LOW TRACKS THROUGH NORTTODAY.
HERN LAKE HURON. SOUTHWEST WINDS
WILL THEN INCREASE IN THE AFTERNOON...WITH MARGINAL GALES POSSIBLE
OVER THE CENTRAL SECTION OF LAKE HURON TOWARD EVENING. COLD WESTERLY
FLOW FOLLOWING FOR WEDNESDAY NIGHT...WITH SOLID GUSTS TO 30 KNOTS
EXPECTED ACROSS MUCH OF THE OPEN WATERS OF LAKE HURON...DIMINISHING
DURING THURSDAY.

HYDROLOGY...

A STRONG LOW LEVEL JET WILL TRANSPORT A GOOD DEAL OF MOISTURE
THROUGH LOWER MICHIGAN THIS EVENING...AS PW VALUES RISE ABOVE 1
INCH. RAINFALL TOTALS TONIGHT ARE EXPECTED TO RANGE FROM HALF AN
INCH TO THREE QUARTERS OF AN INCH...WITH EVEN SLIGHTLY HIGHER TOTALS
POSSIBLE WITH ANY THUNDERSTORM DEVELOPMENT...WHERE WILL LEAD TO
BRIEF HEAVIER INTENSITY RAINFALL. MINOR FLOODING IS POSSIBLE...BUT
NO SIGNIFICANT FLOODING IS EXPECTED AS FLOOD GUIDANCE IS MOSTLY
RUNNING AROUND 2 INCHES. OUTSIDE OF SOME SCATTERED LIGHT RAIN AND
SNOW SHOWERS LATE TOMORROW AFTERNOON/EVENING...MAINLY DRY
CONDITIONS ARE THEN EXPECTED THROUGH THE WEEKEND.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR
     LHZ362-363-462.

     GALE WARNING UNTIL 4 AM EST WEDNESDAY FOR LHZ361>363-462.

     SMALL CRAFT ADVISORY UNTIL 4 AM EST WEDNESDAY FOR LHZ441>443.

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

$$

AVIATION.....DG
UPDATE.......DG/RK
DISCUSSION...MR/RK
MARINE.......SF
HYDROLOGY....SF


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