Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 140507
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
107 AM EDT MON APR 14 2014

.AVIATION...

//DISCUSSION...

A FRONTAL BOUNDARY REMAINS DRAPED ACROSS SOUTHERN MI AND WILL
REMAIN THE FOCUS OF DEVELOPING SHOWERS AND THUNDERSTORMS THROUGH
THE NIGHT. WINDS WILL REMAIN ELEVATED IN SPEED AS WELL DUE TO
INCREASED GRADIENT FLOW JUST AHEAD OF THE FRONT. WINDS WILL BE
PREDOMINATELY FROM THE SOUTH...VEERING TO THE NORTHWEST BEHIND
THE FRONT 12-18Z. LOW LEVEL WIND SHEAR WILL BE AN ISSUE AS THE
LOW LEVEL JET BRINGS 50-60 KNOT FLOW DOWN TO AROUND 2-3KFT. A
SYSTEM WILL RIDE UP THE BOUNDARY AND THROUGH CENTRAL MI THIS
AFTERNOON AND WILL SWEEP A COLD FRONT THROUGH THE AREA. PASSAGE
LOOKING TO BE AROUND 16Z FOR FNT AND 20Z FOR DTW. SHOWERS AND
THUNDERSTORMS WILL INCREASE IN COVERAGE AS THE SYSTEM AS A WHOLE
SHIFTS EAST...BUT THROUGH THE NIGHT THE HIGHEST CHANCES WILL REMAIN
ACROSS THE NORTH INCLUDING FNT AND MBS. CIGS LOOK TO BE VFR EXCEPT
FOR THOSE LOCATIONS SEEING SHOWERS. CLOUDS WILL THICKEN AND LOWER
TOWARDS MORNING WITH THE NEXT LOW PRESSURE SYSTEM LIFTING INTO THE
AREA.

FOR DTW... WIND WILL SOON RAMP UP AND BECOME SOUTHWESTERLY AS THE
SURFACE WARM FRONT LIFTS BACK NORTH. THE MAIN AREA OF SHOWERS AND
THUNDERSTORMS SHOULD STAY TO THE NORTHWEST OF DTW UNTIL CLOSER TO
DAY BREAK. COLD AIR WILL FILTER INTO THE AREA BEHIND THE FRONT
TONIGHT. THIS WILL CHANGE PRECIPITATION TYPE TO SNOW...BUT
CONFIDENCE IS LOW ON TIMING AT THE MOMENT WITH THE SYSTEM TRENDING
SLOWER.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN WIND GUSTS GREATER THAN 35 KNOTS THIS
  MORNING.

* MEDIUM CONFIDENCE IN THUNDERSTORMS EARLY TODAY.

* HIGH CONFIDENCE IN CIGS BELOW 5000 FEET THIS MORNING.

* MEDIUM CONFIDENCE THAT PRECIPITATION TYPE WILL CHANGE TO SNOW
TONIGHT...BUT LOW CONFIDENCE IN TIMING.

&&

.PREV DISCUSSION...ISSUED 930 PM EDT SUN APR 13 2014

UPDATE...
THE FIRST BAND OF SHOWERS AND THUNDERSTORMS HAS LIFTED INTO MID MI
DROPPING AROUND A HALF INCH OF RAINFALL TO THE SAGINAW VALLEY AND
THUMB REGION...WHO REMAIN UNDER A FLOOD WATCH. MOST LOCATIONS WILL
SEE A BRIEF LULL IN RAINFALL FOR THE NEXT FEW HOURS.
THEN...SHOWERS WILL FILL BACK IN FROM THE SOUTHWEST AS THE LOW
LEVEL JET SURGES INTO SOUTHERN MI WITH ENHANCED MOISTURE TRANSPORT
AND THE SHORTWAVE INCHING EVER CLOSER. CURRENT FLOOD WATCH STILL
LOOKS GOOD WITH THE BULK OF THE PRECIP FAVORING OUR NORTHERN
COUNTIES TONIGHT.

PREV DISCUSSION...ISSUED 310 PM EDT SUN APR 13 2014

SHORT TERM...THIS AFTERNOON AND TONIGHT

SURFACE BOUNDARY DRAPED ACROSS LOWER MICHIGAN /ROUGHLY ALONG A BAD
AXE TO MUSKEGON LINE/ WILL WAVER SOMEWHAT LATE THIS AFTERNOON AS A
WEAK SURFACE WAVE SLIDES NORTHEAST ALONG THE BOUNDARY.  THIS
BOUNDARY UNDULATION MAY PRODUCE ENOUGH LOWER-TROPOSPHERIC
CONVERGENCE TO GENERATE SOME FRESH CONVECTIVE...MAINLY ALONG AND
NORTH OF I-69.  THERE IS ENOUGH INSTABILITY - MUCAPE REACHING AROUND
1 KJ/KG - TO SUPPORT A FEW ROBUST UPDRAFTS AND BULK SHEAR WILL BE
ADEQUATE TO ESTABLISH ORGANIZATION TO ANY NEW STORMS. NOT EXPECTING
ANY KIND OF RESPONSE SIMILAR TO LAST EVENING/S OVERACHIEVING
CONVECTION.
MEANWHILE...THE BETTER DEEP MOISTURE SURGE OVER THE MID-MISSISSIPPI
VALLEY WILL CONTINUE TO GENERATE SHOWERS AND THUNDERSTORMS UPSTREAM
OVER ILLINOIS THAT WILL MAKE INROADS ACROSS THE SAGINAW VALLEY
AROUND SUNSET. THE LOW-LEVEL JET IS FORECAST TO INCREASE
SUBSTANTIALLY TONIGHT IN RESPONSE TO A MILD COUPLING OF TWO UPPER
JET STRUCTURES /13.12Z NAM MANUFACTURES 70 KTS/. THE AGGRESSIVE
UPTICK IN THE LOW LEVEL FLOW WILL BE MORE THAN AMPLE TO ADVECT THE
UPSTREAM MOISTURE RICH AIRMASS /PWATS APPROACHING 1.25 IN./ INTO THE
NEARLY STATIONARY FRONTAL STRUCTURE. NWP SUITE OFFERS PLENTY OF
SUPPORT FOR QPF VALUES IN THE 1-2 INCH RANGE ACROSS THE EXISTING
FLOOD WATCH AREA...WILL MAINTAIN THE WATCH AS ADVERTISED AND ALLOW
FOR THE RAINFALL DISTRIBUTION DICTATE ANY FUTURE UPGRADES.

WINDS WILL INCREASE APPRECIABLY OVERNIGHT AS THE STRONGER SURFACE
LOW RIDES NORTH INTO THE REGION.  EXPECTING ENOUGH BOUNDARY LAYER
STABILITY TO PREVENT GUSTINESS.  REGARDLESS...SUSTAINED WINDS
ECLIPSING 20 MPH WILL CAPTURE ONE/S ATTENTION.

LONG TERM...

THROUGH EARLY MONDAY, ORGANIZED SHOWER ACTIVITY WILL REMAIN CONFINED
TO THE NORTHERN HALF OF THE CWA ALONG THE LOW-LEVEL BAROCLINIC ZONE.
MOISTURE TRANSPORT AND CONVERGENCE ALONG THE PERIPHERY OF THE
LOW-LEVEL JET WILL BE SUFFICIENT TO PRODUCE ANOTHER 0.25-0.5" OF
RAIN ACROSS THE SAGINAW VALLEY. ELSEWHERE...EXPECT MORE WIDELY
SCATTERED ACTIVITY WITHIN LESS FOCUSED ASCENT ASSOCIATED WITH THE
WARM CONVEYOR. THE RESPONSIBLE SHORTWAVE WILL THEN RACE OFF TO THE
NORTHEAST BY MIDDAY WHICH WILL RESULT IN LARGE SCALE MOISTURE AND
FORCING QUICKLY STRIPPING AWAY FROM THE REGION. BEST CHANCE FOR RAIN
FOR THE REMAINDER OF THE AREA WILL COME AS A CONSEQUENCE OF
ENCROACHING UPSTREAM HEIGHT FALLS THAT WILL PUSH THE FRONT THROUGH
THE AREA 15-20Z. GIVEN THAT CROSS-SECTIONS REVEAL A DENSITY CURRENT
TYPE OF STRUCTURE TO THE LEAD EDGE OF THE FRONTAL ZONE, EXPECT A
NARROW CORRIDOR OF STRONG FORCING TO MAINTAIN A LINE OF SHOWERS AS
THE FRONT PUSHES THROUGH THE CWA. SHORT DURATION AND QUICK MOTION
WILL LIMIT RAINFALL AMOUNTS, THOUGH A FEW RUMBLES OF THUNDER WILL
NOT BE OUT OF THE QUESTION. ANY DEEP CONVECTION ALONG THE FRONT WILL
BE CAPABLE OF MIXING DOWN SOME HEFTY WIND GUSTS, BUT NOTHING SO
IMPRESSIVE TO WARRANT A MENTION OF SEVERE WX ATTM. GUSTS WITHIN THE
FRONTAL ZONE ITSELF MAY BE QUITE ROBUST AS WELL AND CANNOT RULE OUT
SOME WIND ADVISORY TYPE OF GUSTS, BUT THIS POTENTIAL ALSO APPEARS
MARGINAL AT BEST.

LULL ASSOCIATED WITH THE EXITING SHORTWAVE WILL ENSUE DURING THE
LATE AFTERNOON AS STRONG COLD ADVECTION CONTINUES BEHIND SURFACE
FRONT. AFTER SEEING EARLY MORNING HIGHS IN THE WARM SECTOR REACHING
THE LOW TO MID 60S, ALL LOCATIONS WILL BE SOLIDLY IN THE 40S BY
EVENING. LARGE SCALE TROUGH WILL THEN BEGIN TO ROTATE THROUGH THE
AREA, ASSUMING A NEUTRAL TILT BY LATE MONDAY NIGHT INTO TUESDAY
MORNING. AS THIS OCCURS, THE UPPER JET OVER THE LOWER PENINSULA WILL
STRENGTHEN CONSIDERABLY AND WILL EXCITE A ROUND OF STRONG
FRONTOGENESIS AS THE MID-LEVEL FRONT PROGRESSES THROUGH THE AREA
00Z-06Z. STATIC STABILITY WILL BE EXTREMELY LOW THROUGHOUT THE
COLUMN WITH POCKETS OF INSTABILITY PROBABLE. THOUGH PRECIP WILL
LIKELY BEGIN AS RAIN, ONGOING COLD ADVECTION AND VERY STRONG DEEP
LAYER ASCENT WILL BE SUFFICIENT TO CHANGE ALL LOCATIONS OVER TO SNOW
EVENTUALLY. GIVEN THE BORDERLINE NATURE OF FORECAST SOUNDINGS FROM
PTK AND POINTS NW, IT SEEMS REASONABLE TO EXPECT LOCATIONS WITHIN
THE CORRIDOR OF HEAVIEST PRECIP TO BE FORCED OVER TO SNOW A BIT
EARLIER THAN WOULD OTHERWISE BE ANTICIPATED. INTRODUCED A SWATH OF
1-3" ALONG A LINE FROM HOWELL TO BAD AXE TO GET THE BALL ROLLING.
AMOUNTS WILL LIKELY BE LIMITED TO 2" OR LESS IN THE FAR NW WHERE
FORCING DURATION/INTENSITY WILL BE LESS. WET GROUND/STANDING WATER
WILL PROBABLY MAKE INITIAL ACCUMULATION DIFFICULT THERE AS WELL.

MEANWHILE, ANOTHER WAVE WILL RIPPLE ALONG IN THE UPPER FLOW LATE
MONDAY NIGHT AS THE JET CORE SIMULTANEOUSLY SLIPS BY OVERHEAD.
RENEWED ASCENT ALONG WITH WITH SOME TILTING OF THE FRONTAL ZONE
WITHIN THE NOW-PROGRESSIVE RIGHT ENTRANCE REGION SUPPORTS CONTINUED
MENTION OF SNOW FOR THE REMAINDER OF MONDAY NIGHT. CERTAINLY
POSSIBLE THAT THIS SECOND ROUND OF LIGHT SNOW PADS ACCUMS A BIT OVER
THE SOUTHEAST PORTION OF THE AREA, JUSTIFYING A GENERAL 1-2" FOR
MOST OF THE METRO AREA.

SEASONABLY COLD AIR IN THE UPPER 30S WILL BE FIRMLY ENTRENCHED OVER
THE AREA ON TUESDAY. FAVORABLE POSITIONING OF THE THERMAL TROUGH
OVERHEAD ALONG WITH DAYTIME HEATING WILL SUPPORT AN EXPANSION OF
BOUNDARY LAYER CLOUD COVER EARLY IN THE DAY ALONG WITH THE TYPICAL
CHANCE FOR FLURRIES. BUILDING HIGH PRESSURE AND REBOUNDING HEIGHTS
ALOFT WILL FAVOR CLEARING TUESDAY NIGHT.

TEMPERATURES WILL SLOWLY START TO REBOUND TOWARD THE END OF THE
WEEK...WITH HIGHS GETTING BACK TO AROUND NORMAL. MOST OF THE CWA IS
EXPECTED TO REMAIN DRY WEDNESDAY NIGHT AND THURSDAY...DUE TO THE
CONTINUED INFLUENCE OF HIGH PRESSURE OVER THE NEW ENGLAND AREA.  THE
EXCEPTION WILL BE OVER EXTREME NORTHEAST PORTIONS OF THE CWA WHERE A
SLIGHT CHANCE FOR SHOWERS REMAINS AS MODELS ARE SHOWING A
PERTURBATION IN THE UPPER LEVEL FLOW MOVING OVER THE NORTHERN GREAT
LAKES.  THE NEXT APPRECIABLE CHANCES FOR PRECIPITATION LOOKS TO COME
IN THE FRIDAY AND SATURDAY TIMEFRAME...AS A LOW PRESSURE SYSTEM FROM
THE SOUTHERN PLAINS MOVES NORTHEAST TOWARDS THE REGION.

MARINE...

FRESH SOUTHWEST WINDS WILL APPROACH GALE FORCE AT TIMES OVER THE
SOUTHERN HALF OF LAKE HURON LATE TONIGHT AS A WEAK LOW PRESSURE
SYSTEM LIFTS TOWARD GEORGIAN BAY. ALTHOUGH WARM STABLE FLOW WILL
INITIALLY INHIBIT WIND GUST POTENTIAL...GUSTY NORTHWEST FLOW WILL
QUICKLY BUILD IN MONDAY EVENING INTO MONDAY NIGHT. THE PERSISTENT
NORTHWEST FETCH WILL ALLOW WAVES TO BUILD INTO THE 3 TO 5 FOOT RANGE
ALONG THE EXPOSED NEARSHORE WATERS OF THE THUMB MONDAY EVENING
THROUGH LATE TUESDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR THIS
PERIOD.

HYDROLOGY...
LAST NIGHT/S RAINFALL DISTRIBUTION IS AFFORDING A BETTER DEPICTION
OF HOW THE LOCAL RIVER RISES WILL TRANSPIRE.  FORECASTS HAVE HIGH
CONFIDENCE FOR THE TITTABAWASSEE TO GO INTO MODERATE FLOOD...AND
CHALLENGE MAJOR FLOOD...DEPENDING ON HOW TONIGHT/S RAIN EVENT
TRANSPIRES.  FATHER DOWNSTREAM ON THE SAGINAW...THERE IS MORE TIME
TO ASSESS THE TOTAL BASIN COLLECTION.  THE CASS RIVER IS STILL ON
THE VERGE OF REACHING FLOOD STAGE WITH THE CURRENT FORECAST...BUT
MINOR CHANGES IN PRECIP DISTRIBUTION WILL HAVE BIG INFLUENCES ON THE
FORECAST.

CLIMATE...
SNOWIEST WINTER SEASON

CITY       2013-2014        RECORD
FLINT       82.6"      82.9" (1974-75)
DETROIT     91.7"      93.6" (1880-81)

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...FLOOD WATCH...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055...UNTIL 8
     PM MONDAY.

LAKE HURON...NONE.

LAKE ST CLAIR...NONE.

MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....DRK
UPDATE.......DRK
SHORT TERM...MANN
LONG TERM....JVC/SS
MARINE.......JVC
HYDROLOGY....MANN
CLIMATE......JVC


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








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