Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 131720
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
120 PM EDT SUN APR 13 2014

.AVIATION...

//DISCUSSION...

GUSTY SOUTHWEST WINDS ARE THE FIRST ORDER OF BUSINESS TODAY.
VIGOROUS MIXING HAS BECOME WELL ESTABLISHED OVER THE SOUTHERN
TERMINAL SITES AND THIS WILL CONTINUE THROUGH THE BALANCE OF THE
AFTERNOON. EXPECT GUSTS TO SETTLE OFF OF THE RECENT 30+ KT VALUES AT
A FEW LOCATIONS /FORCING FOR THAT GUSTINESS HAS MOVED EAST INTO
ONTARIO/. THE GUSTS SHOULD SUBSIDE AN HOUR OR TWO AFTER SUNSET...
HOWEVER THE GRADIENT FLOW WILL BE SUBSTANTIAL SUPPORTING NEARLY 20
KTS AS A SURFACE LOW RIPPLES NORTHEAST INTO THE SOUTHERN LAKES
REGION.

THE GREATEST CHANCES FOR SHOWERS AND THUNDERSTORMS REMAINS ACROSS
THE SAGINAW REGION DURING THE EVENING HOURS. THERE IS A SHOT AT SOME
WARM SECTOR DEVELOPMENT IN THE VICINITY OF FLINT AND PONTIAC.
OTHERWISE...THE MAIN BAND OFF PRECIPITATION SHOULD BECOME
ESTABLISHED ALONG A SAGINAW TO GRAND RAPIDS LINE THEN CRAWL EASTWARD
OVERNIGHT. THERE IS SUBSTANTIAL FORCING TO MAINTAIN THUNDER CHANCES
THROUGH NIGHT AND INTO EARLY MONDAY. THAT SAME FORCING WILL
ESTABLISH VERY STRONG WINDS JUST ABOVE THE SURFACE...THEREFORE HAVE
INTRODUCED WIND SHEAR IN THIS FORECAST OFFERING TO REFLECT THE NEAR
60 KTS IN THE LOWEST SEVERAL THOUSAND FEET.

FRONTAL PASSAGE NOW APPEARS TO BE SLOWER THAN PREVIOUSLY
ADVERTISED.  THEREFORE...THE PRECIPITATION CHANCES AND GUSTY DAYTIME
CONDITIONS WILL PERSIST LONGER THAN PREVIOUS FORECASTS.

FOR DTW...GUSTY SOUTHWEST WINDS WILL BE THE MAIN STORY THE REST OF
TODAY. THE MAIN AREA OF SHOWERS AND THUNDERSTORMS WILL REMAIN WEST
AND NORTH OF DTW UNTIL LATE TONIGHT. EXPECTATIONS ARE FOR SHOWER AND
THUNDERSTORMS TO AFFECT THE TERMINAL IN THE POST SUNRISE HOURS OF
MONDAY. VERY GUSTY SOUTHWEST WINDS WILL ALSO RESUME SHORTLY AFTER
DAYBREAK AS WELL AND WILL PERSIST UNTIL THE COLD FRONT PASSES JUST
AFTER NOON.

//DTW THRESHOLD THREATS...
* MEDIUM CONFIDENCE IN WIND GUSTS GREATER THAN 35 KNOTS MONDAY
  MORNING.
* MEDIUM CONFIDENCE IN THUNDERSTORMS EARLY MONDAY
* HIGH CONFIDENCE IN CIGS BELOW 5000 FEET TONIGHT AND MONDAY.

&&

.PREV DISCUSSION...ISSUED 344 AM EDT SUN APR 13 2014

SHORT TERM...TODAY AND TONIGHT

AFTER EVENING CONVECTION WORKED EAST...A GENERAL DRYING TREND BEGAN
ACROSS MUCH OF SE MI. THE CONVECTION LAID OUT A SERIES OF OUTFLOW
BOUNDARIES WHICH ARE IN THE PROCESS OF WASHING OUT AS WHICH WILL
ONCE AGAIN LEAD TO DOMINATE SW FLOW TODAY. THE MAIN FRONTAL SURFACE
REMAINS DRAPED ACROSS MID MI THEN SW TOWARD IOWA WHICH KEEPS US IN
THE WARM SECTOR THROUGH TONIGHT. MODEL SOUNDINGS ADVERTISE ANOTHER
DAY WITH A WELL MIXED BL DEVELOPING...UP TO AROUND 750MB. THIS
SHOULD ALLOW WIND GUSTS OF 20-30 MPH TO DEVELOP THIS AFTERNOON.
CURRENTLY THERE IS A SHORTWAVE OVER IOWA WHICH GOT A GOOD NOCTURNAL
BOOST FROM THE LL JET. THIS WAVE WILL RIDE NE ALONG THE FRONT
THROUGH NORTHERN LOWER MI THIS AFTERNOON. IT LOOKS LIKE THE BULK OF
THE SHOWERS AND THUNDERSTORMS SHOULD PASS MOSTLY WEST AND NORTH OF
OUR CWA WITH THE EXCEPTION OF THE SAGINAW VALLEY WHICH WILL LIKELY
GET CLIPPED BY THE SYSTEM. HIGHEST POPS/QPF REMAIN OVER THAT AREA.
THERE WILL REMAIN A TIGHT GRADIENT OF POPS/QPF FRO NORTHWEST TO
SOUTHEAST ACROSS THE CWA THROUGH TONIGHT AS THE NEXT STRONGER SFC
LOW WILL PREVENT THE FRONT FROM MOVING MUCH AT ALL THROUGH THAT
PERIOD. A CHANGE IN THE UPPER LEVELS...WITH STRONG JET DIGGING
THROUGH THE PLAINS CARVING A TROUGH DOWN INTO TEXAS...WILL SWING
THROUGH THE MISSISSIPPI VALLEY AS THE SHEARING OUT SFC LOW LIFTS
INTO THE AREA. THE MORE PROGRESSIVE FLOW WILL ALLOW THE SYSTEM TO
TAKE A MORE EASTWARD TRACK OVERNIGHT. THIS WILL ALLOW BETTER
COVERAGE OF SHOWERS TO MOVE INTO THE AREA.

HEAVY RAINS AND TRAINING THUNDERSTORMS ARE STILL PRESENTING POSSIBLE
FLOODING CONCERNS FOR AREAS NORTH OF I69...ESPECIALLY THE SAGINAW
BAY AREA. RAINFALL AMOUNTS FROM SATURDAY EVENINGS CONVECTION RANGED
FROM 1-2 INCHES WITH THE MIDLAND COOP STATION REPORTING 1.88
INCHES AT MIDNIGHT. WITH AN ADDITIONAL 1-3 INCHES OF RAIN POSSIBLE
FOR THAT AREA OVER THE NEXT 2 DAYS...THE CURRENT FLOOD WATCH WILL
CONTINUE AND THE AREA MONITORED CLOSELY.

LONG TERM...

THE FRONTAL BOUNDARY PARKED TO OUR WEST WILL PUSH EAST THROUGH THE
CWA AS A COLD FRONT ON MONDAY AS AN APPROACHING MID LEVEL TROUGH
CAUSES HEIGHT FALLS OVER THE CENTRAL GREAT LAKES REGION. MODEL CROSS
SECTIONS SHOW ABUNDANT LOW AND MID LEVEL FGEN AS THE FRONT TRACKS
EAST ON MONDAY WITH COPIOUS AMOUNTS OF MOISTURE AS PWAT VALUES
APPROACH 1.4 INCHES. THUNDERSTORMS ARE STILL POSSIBLE AHEAD OF THE
FRONT ACROSS THE SOUTHEASTERN PORTION OF THE CWA MONDAY MORNING WITH
LINGERING INSTABILITY AHEAD OF THE COLD FRONT. THE HIGH AMOUNT OF
FORCING AND MOISTURE AVAILABLE ON MONDAY WILL MEAN A CONTINUED
THREAT FOR FLOODING...ESPECIALLY ACROSS THE SAGINAW VALLEY AND
NORTHERN THUMB WHICH WILL SEE SEVERAL ROUNDS OF HEAVY RAIN BEFORE
MONDAY. WITH 1.5 TO 2.5 INCHES OF RAIN ALREADY FALLING OVER THE
NORTHERN THUMB AND SAGINAW VALLEY WILL EXTEND THE FLOOD WATCH
INTO THE NORTHERN THUMB THROUGH MONDAY.

THE 00Z SUITE OF MODEL RUNS CONTINUE THE 12Z MODEL SOLUTIONS OF
CONTINUED PRECIPITATION MONDAY NIGHT WITH LINGERING MID LEVEL FGEN
AND UPPER LEVEL DIVERGENCE UNDER THE RIGHT ENTRANCE REGION OF A 110
KNOT JET STREAK OVER THE NORTH CENTRAL GREAT LAKES REGION. GIVEN THE
CONTINUITY OF THIS FEATURE WILL CONTINUE THE PREVIOUS SHIFTS
THOUGHTS AND RAISE POPS ANOTHER NOTCH ACROSS SOUTHEAST MICHIGAN ON
MONDAY NIGHT. MODEL SOUNDINGS INDICATE THE ATMOSPHERE CONTINUES TO
COOL OFF BEHIND THE COLD FRONT...SUPPORTING A TRANSITION FROM RAIN
TO ALL SNOW DURING THE OVERNIGHT HOURS. THIS TRANSITION COULD
TRANSLATE TO ACCUMULATING SNOWFALL ACROSS THE AREA MONDAY
NIGHT...PARTICULARLY ACROSS THE NORTH WHERE THE TRANISTION WILL
OCCUR EARLIER IN THE EVENING. ALTHOUGH THESE ACCUMULATIONS WILL BE
LIGHT...THEY HAVE THE POTENTIAL OF BREAKING THE RECORD FOR THE
SNOWIEST YEAR ON RECORD AT FLINT WHICH IS ONLY 0.4 INCHES FROM
BREAKING THE RECORD. DETROIT LOOKS TO NEED ANOTHER EVENT AS THEY ARE
STILL 2 INCHES FROM BREAKING THE RECORD.

CONDITIONS EVENTUALLY DRY OUT TUESDAY AND TUESDAY NIGHT AS HIGH
PRESSURE BUILDS IN OVER THE CENTRAL GREAT LAKES WITH COOLER
TEMPERATURES EXPECTED THROUGH THE MIDDLE PART OF THE WEEK.

HYDROLOGY...
FLOOD WATCH IN EFFECT FOR THE SAGINAW VALLEY AND NORTHERN THUMB THIS
EVENING THROUGH MONDAY EVENING.  MULTIPLE EPISODES OF
RAINFALL...HEAVY AT TIMES WILL TEND FOCUS ALONG A FRONTAL BOUNDARY
IN THE VICINITY OF THIS AREA.  RAINFALL AMOUNTS RANGING FROM 1 TO 3
INCHES.  THIS WILL LEAD TO RISES IN AREA RIVERS AS WELL AS POSSIBLE
FLOODING OF LOWLAND AREAS.  LATEST FORECAST FOR THE RIVER BASINS
ALONG THIS CORRIDOR
/PARTICULARLY THE TITTABAWASSEE AND SAGINAW RIVERS/ SHOW AN
INCREASED RISK OF FLOODING BEGINNING SOMETIME TUESDAY OR TUESDAY
NIGHT.  HYDROLOGIC OUTLOOK ISSUED YESTERDAY AFTERNOON /ESFDTX/
HIGHLIGHTS THE DETAILS.  A FLOOD WARNING WILL BE NECESSARY SHOULD
THIS FORECAST HOLD AND CONFIDENCE INCREASES IN SEEING THE HIGHER END
OF THE EXPECTED RAINFALL AMOUNTS.

MARINE...

MODERATE SOUTH TO SOUTHWEST WINDS WILL PERSIST THROUGH TONIGHT
SOUTH OF A FRONTAL BOUNDARY DRAPED ACROSS CENTRAL LOWER MICHIGAN.
THIS FRONTAL BOUNDARY WILL PROVIDE THE FOCUS FOR SHOWER AND
THUNDERSTORM DEVELOPMENT THROUGH MONDAY.   GUSTY NORTHWEST WINDS
WILL EMERGE AS THE FRONT SAGS SOUTHEAST MONDAY AND MONDAY NIGHT.
WINDS WILL REMAIN GUSTY OUT OF THE NORTHWEST AS COLDER AIR FUNNELS
IN THROUGH TUESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FLOOD WATCH...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055...FROM 8 PM
     SUNDAY TO 8 PM MONDAY.

LAKE HURON...NONE.

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

&&

$$

AVIATION.....MANN
SHORT TERM...DRK
LONG TERM....KURIMSKI
MARINE.......KURIMSKI
HYDROLOGY....KURIMSKI


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






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