Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 040354
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1154 PM EDT TUE MAY 3 2016


.AVIATION...

A REGION OF RAIN WILL SLOWLY PUSH TOWARD THE EAST DURING THE EARLY
MORNING. MID LEVEL MOISTURE ADVECTION IN ADVANCE OF THE MAIN REGION
OF RAIN MAY TRIGGER SOME BRIEF HIGH BASED LIGHT SHOWERS PRIOR TO
DAYBREAK. RECENT MODEL GUIDANCE SUGGESTS THE MAIN REGION OF RAIN
WILL WORK INTO MBS AND FNT JUST PRIOR TO DAYBREAK. WITH THE UPPER
WAVE FORECAST TO DEVELOP INTO A CLOSED MID LEVEL LOW OVER NRN
INDIANA ON WEDNESDAY...THE AXIS OF STRONGER FORCING WILL STRUGGLE
TO PUSH MUCH FARTHER EAST THAN FNT AND PERHAPS PTK. INITIAL DRY
AIR IN THE LOW LEVELS WILL LEAD TO A RATHER GRADUAL LOWERING OF
CEILING HEIGHTS DURING THE COURSE OF THE MORNING. SOME DEGREE OF
MVFR TYPE CIGS ARE EXPECTED AT FNT AND MBS BY AFTERNOON.
DEVELOPING SFC LOW PRESSURE FORECAST TO TRACK SOUTH OF THE REGION
WED AFTERNOON WILL DRAW A LITTLE COOLER LOW LEVEL AIR INTO FNT AND
MBS...OFFERING A GOOD CHANCE OF LOW END MVFR AND/OR IFR CIGS LATE
WED AFTERNOON/EVENING. A PERSISTENT INFLUX OF LOW LEVEL DRY AIR
FARTHER EAST MAY IN FACT LEAD TO A RATHER NARROW REGION BETWEEN
IFR/MVFR CONDITIONS AND VFR CONDITIONS.

FOR DTW...RECENT RADAR IMAGERY IS SUGGESTING THE SCATTERED HIGH
BASED SHOWERS WILL IMPACT METRO DETROIT DURING AT LEAST THE FIRST
TWO TO FOUR HOURS OF THE TAF PERIOD. OTHERWISE...RECENT MODEL TRENDS
SUGGEST DRIER LOW LEVEL AIR GETTING ADVECTED INTO METRO DETROIT FROM
THE EAST ON WEDNESDAY AS THE SFC LOW DEVELOPS TO THE SOUTHWEST. THIS
MAY HOLD THE MORE WIDESPREAD RAIN AND LOWER CEILINGS WEST OF METRO
AIRPORT.

//DTW THRESHOLD PROBABILITIES...

* LOW IN CEILINGS AT OR BELOW 5000 FT THIS MORNING. MEDIUM THIS
  AFTERNOON.

* LOW IN THUNDERSTORMS IMPACTING THE AREA TODAY.

&&

.PREV DISCUSSION...ISSUED 957 PM EDT TUE MAY 3 2016

UPDATE...

THE MID LEVEL FORCING DRIVING THE REGION OF LIGHT RAIN ACROSS NW
LOWER MI WILL LARGELY REMAIN FOCUSED WEST OF THE FORECAST AREA
THROUGH THE OVERNIGHT. THIS IS A RESULT OF THE MAIN RIBBON OF MID
LEVEL HEIGHT FALLS ASSOCIATED WITH THE DEEPENING UPPER WAVE TO THE
NORTH STAYING FOCUSED ACROSS WISCONSIN AND NRN ILLINOIS TONIGHT.
MID LEVEL MOISTURE ADVECTION DURING THE OVERNIGHT WITH STEEPENING
MID LEVEL LAPSE RATES SHOULD ALLOW SOME SHOWERS TO DEVELOP OUT
AHEAD OF THE MAIN RIBBON OF LARGE SCALE ASCENT...SUPPORTING THE
CURRENT CHANCE POPS. HIGHER POPS WILL REMAIN ACROSS THE SAGINAW
VALLEY AND FAR WESTERN PORTIONS OF THE AREA WHERE THE LARGER SCALE
ASCENT MAY SLIDE IN JUST PRIOR TO DAYBREAK. OVERALL...MINIMAL
UPDATES ARE NEEDED TO THE GOING FORECAST.

PREV DISCUSSION...ISSUED 317 PM EDT TUE MAY 3 2016

DISCUSSION...

LATEST WATER VAPOR IMAGERY SHOWS HIGHLY AMPLIFIED UPPER LEVEL RIDGE
OVER THE ROCKIES OF NORTH AMERICA... WITH IMPRESSIVE UPPER LEVEL
LOW/CIRCULATION TRACKING THROUGH THROUGH WESTERN ONTARIO. THIS
SYSTEM WILL BE TENDING TO TAKE ON A NEGATIVE TILT AS IT DROPS SOUTH
THROUGH WESTERN/CENTRAL GREAT LAKES...WITH THE 500 MB COLD POOL OF
-28 C TRACKING THROUGH LAKE MICHIGAN...PER 12Z EURO. THIS IS
IMPORTANT...AS THE VARIOUS OTHER MODELS (GFS/NAM/REGIONAL GEM) HAVE
THE -25 TO -28 C COLD POOL TRACKING JUST WEST OF LAKE MICHIGAN.

LOW PRESSURE DEVELOPING ALONG THE FRONTAL BOUNDARY WILL TEND TO
STALL THE FRONT DURING THE DAY...WITH A GOOD DEFORMATION ZONE
SETTING UP...ALTHOUGH EXACT LOCATION OF LOW LEVEL CONVERGENCE
ZONE/CIRCULATION VARIES AMONGST 12Z GFS/NAM/REGIONAL GEM. BUT
AGAIN...IF ONE FAVORS THE FARTHER EAST SOLUTION OF THE EURO...AREAS
ALONG AND WEST OF U.S 23 STAND GOOD CHANCE TO BE EMBEDDED WITH THE
HEAVIER RAINFALL AXIS (IN EXCESS OF HALF AN INCH). PW VALUE WILL BE
RUNNING AROUND 0.75 INCHES...AND THERE DOES LOOK TO BE SOME
CONVECTIVE ELEMENTS/POSSIBLE THUNDERSTORMS WITH PRETTY GOOD MID
LEVEL LAPSE RATES (UP TO 7 C/KM FROM 700-500 MB). 12Z NAM SUGGEST
1000-850 MB CAPES UP TO 500 J/KG...BUT THAT IS LIKELY OVERDONE. IN
ADDITION...LOW LEVEL MOISTURE QUALITY IS NOT THAT GREAT WITH 850 MB
DEW PTS OF 3 C AND SURFACE DEW PTS ONLY IN THE 40S...LEADING TO
SOME UNCERTAINTY WITH AREAL COVERAGE OF ACTIVITY...AND BULK OF
ACTIVITY WILL PREDOMINATELY BE FOCUSED ALONG THE SHEAR/CONVERGENCE
AXIS DRAPED ACROSS THE WESTERN THIRD OF THE CWA.

THERE DOES LOOK TO BE SOME LOW LEVEL WARM ADVECTION OCCURRING OVER
THUMB REGION AND FAR EASTERN AREAS...WHERE TEMPERATURES WILL HAVE A
SHOT AT REACH OR EXCEED 60 DEGREES TOMORROW BEFORE SHOWERS/CONVECTION
PUSHES EAST.

FORTUNATELY...GOOD SOUTHWARD MOMENTUM SHOULD PUSH 500 MB LOW/COLD
CENTER OVER THE EASTERN TENNESSEE VALLEY THURSDAY MORNING
(ALLOWING SHOWERS TO TAPER OFF FROM NORTH TO SOUTH WEDNESDAY
EVENING ...WITH PRONOUNCED UPPER LEVEL RIDGING EXTENDING EASTERN
INTO THE GREAT LAKES REGION FOR END OF THE WORK WEEK...ALLOWING
FOR A WARMUP INTO FRIDAY WITH TEMPERATURES PUSHING TO 70 DEGREES
AS 850 MB TEMPS RISE INTO THE UPPER SINGLE NUMBERS BY DAY`S END.

12Z MODEL SUITE CONTINUES THE FASTER TREND FOR THE WAVE AND
ASSOCIATED FRONT FOR SATURDAY...NOW SUPPORTING A BETTER CHANCE OF
SHOWERS AND THUNDERSTORMS DURING THE DAY. MODELS HAVE BEEN
CONSISTENT IN AGGRESSIVELY EXPANDING HIGH PRESSURE INTO THE GREAT
LAKES IN THE WAKE OF THE FRONT. ASSUMING THIS SCENARIO PLAYS
OUT...SUNDAY WOULD BE DRY AND COOLER. RIDGING AT THE SURFACE AND
ALOFT WILL FAVOR DRY WEATHER INTO MONDAY...WITH HEIGHT FALLS AND
ASSOCIATED PRECIP CHANCES RETURNING BY TUESDAY.

MARINE...

A LIGHT SOUTHERLY WIND WILL EXIST THIS EVENING IN ADVANCE OF A COLD
FRONT. AN AREA OF LOW PRESSURE WILL DEVELOP OVER LOWER MI ALONG THIS
THIS COLD FRONT AS IT MOVES THROUGH ALL WATERWAYS LATE TONIGHT AND
WEDNESDAY. WINDS WILL BECOME NORTHERLY AND STRENGTHEN WITH THIS
FRONTAL PASSAGE BY WEDNESDAY NIGHT. STRONGEST WINDS WILL BE ACROSS
SOUTHERN SECTIONS OF LAKE HURON...WHERE A PERIOD OF WINDS UP TO 20
KNOTS APPEARS LIKELY. THE ONSHORE FLOW WILL LEAD TO A PERIOD OF
ELEVATED WAVE CONDITIONS ALONG THE THUMB WEDNESDAY NIGHT AND
THURSDAY. HIGH PRESSURE WILL THEN BRING TRANQUIL MARINE CONDITIONS
FOR THE LATE WEEK PERIOD.

HYDROLOGY...

THE NEXT SYSTEM WAS DIVING SOUTH AND WILL STRENGTHEN AS IT MOVES
OVER LOWER MI.  SHOULD BE STRONG FORCING ON THE NORTHWEST FLANK OF
THE SYSTEM SETTING UP A 9 TO 12 HOUR WINDOW THAT WILL FOCUS SOME
HEAVIER RAINFALL DURING THE DAY ON WEDNESDAY. STILL SOME UNCERTAINTY
ON THE PLACEMENT OF HEAVY RAINFALL AXIS...BUT AREAS AROUND LAN TO
MBS TO HTL LOOK MOST LIKELY TO GET UP TO AN INCH. AREAS SOUTH AND
EAST WILL HAVE A MORE SHOWERY PATTERN WITH SOME THUNDERSTORMS. THESE
MAY PRODUCE SOME HEAVIER RAINFALL BUT A BASIN AVERAGE SHOULD BE A
QUARTER TO A HALF INCH. ALL OF THIS PULLS AWAY AS THE SYSTEM MOVES
SOUTHEAST WEDNESDAY NIGHT WITH GENERALLY DRY WEATHER THURSDAY AND
FRIDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....SC
UPDATE.......SC
DISCUSSION...SF/DT
MARINE.......RBP
HYDROLOGY....RBP


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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