Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 300754
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
354 AM EDT TUE JUN 30 2015

.SHORT TERM...TODAY AND TONIGHT

AN IMPRESSIVE +100 KNOT UPPER LEVEL JETLET CASCADING DOWN THE
FORWARD FACE OF THE WESTERN NOAM RIDGE INTO NORTHERN MINNESOTA THIS
MORNING WILL CAUSE A RAPID REINFORCEMENT OF THE DOWNSTREAM TROUGH
DURING THE NEXT 6 TO 9 HOURS. THE MODELS CLEARLY DEFINE A TIGHT
SHEAR GRADIENT ON THE DOWNSTREAM FLANK OF U/L JET MAXIMUM OVER
PORTIONS OF WI AND IL BY 18Z. EMBEDDED SHORTWAVE ENERGY WITHIN THE
REPOSITIONING TROUGH AXIS...INCLUDING THE STRONGER LAKE
SUPERIOR/U.P. SHORTWAVE WILL SWEEP ACROSS LOWER MICHIGAN DURING THE
AFTERNOON AND EARLY EVENING HOURS TONIGHT.

A WEAKER AND LESS PROGRESSIVE SURFACE REFLECTION OVER WESTERN LAKE
ERIE THIS PAST EVENING HAS LARGELY BEEN OVERWHELMED BY DEVELOPING
SOUTHERLY FLOW IN ADVANCE OF THE APPROACHING SHORTWAVE. THIS HAS
ALLOWED AN OLD NEAR SURFACE OCCLUSION OR FRONTAL BOUNDARY TO LIFT
NORTHWESTWARD INTO THE DETROIT AREA. THERE HAS BEEN SOME
DRIZZLE/SPRINKLES/LIGHT RAIN WITHIN THIS THETA E RIBBON IN ADDITION
TO LOW CLOUD STRATUS. RADAR EVOLUTION THIS MORNING SUGGESTS THIS
SHOULD CONTINUE TO IMPACT THE AREA DURING THE NEXT 3 HOURS BEFORE
ADVECTING FARTHER NORTHWARD.

THE ENHANCED MOISTURE PLUME IS EXPECTED TO TRACK TO THE NORTHERN CWA
BY THE LATE MORNING...POST 15Z. SIGNAL WITHIN THE CAM DATSETS IN
ADDITION TO FCST SOUNDING ANALSYIS SUGGESTS AT SOME POTENTIAL FOR
SCATTERED SHOWERS TO INITIATE OFF OF THIS MOISTURE WITH DAYTIME
HEATING. THESE INTIAL SHOWERS APPEAR TO BE SHALLOW...WITH TOPS AT 15
KFT AGL.

UPSTREAM SHORTWAVE ENERGY COLLECTED ALONG THE AFOREMENTIONED SHEAR
GRADIENT WILL THEN BE KICKED EASTWARD FAIRLY QUICKLY DURING THE
AFTERNOON HOURS DUE TO A NUMBER OF FACTORS. THE INCREASE IN
MAGNITUDE OF DIFFERENTIAL CYCLONIC VORTICITY ADVECTION WILL THEN ADD
A SIGNIFICANT COMPOMENT OF SYNOPTIC SCALE SUPPORT FOR ASCENT. IT
REMAINS DIFFICULT TO ADD MUCH DETAIL UNDER LITTLE TO NO CAPPING AND
FAVORABLE LARGE SCALE ASCENT. LOOKING AT MODEL DATA...THERE APPEARS
TO BE A STRONG DEPENDENCE FOR CONVECTION BASED ON SFC DEWPOINTS.
THIS SUGGESTS THAT AREAS IN THE WESTERN CWA AND THE TRI CITIES STAND
THE BEST POTENTIAL TO WITNESS HIGHER QPF AMOUNTS. A MORE PERSISTENT
LIGHT EASTERLY FLOW OVER THE THUMB DOWN INTO THE DETROIT METRO AREA
WILL LIKELY TEMPER THE DEWPOINT RESPONSE THERE. AN INCREASE IN THE
MEAN 600-400MB MOISTURE CONINCIDENT TO THE DEEP TROUGH AXIS SUPPORTS
GOING WITH A LIKELY/NUMEROUS POP THIS AFTERNOON. TALL SKINNY CAPE
WITH SUB 400 J/KG SBCAPE SUPPORTS NO ORGANIZED SEVERE WEATHER RISK.
AN ISOLATED HEAVY RAIN THREAT IS AGAIN IN PLAY...WITH VERY SLOW
STORM MOTION PREDICTED. COLUMN MEAN WIND SUGGESTS ANY CONVECTIVE
CELLS THIS AFTERNOON WILL TRACK SW TO NE AT APPROXIMATELY 15 MPH.
WITH SUCH WEAK FLOW THERE IS POTENTIAL FOR STORM MOTION TO BECOME
MODULATED BY SHORTWAVE/VORTICITY CENTERS. IN FACT...COULD ACTUALLY
SEEM SOME MINOR BACKBUILDING AND TRAINING OF SHOWER OR THUNDERSTORM
CELLS TOWARDS EVENING. ATTM...THE BEST POTENTIAL FOR THIS TO OCCUR
IS OVER CENTRAL SECTION OF THE CWA...AWAY FROM THE RAISN RIVER BASIN.

SYNOPTIC SCALE FORCING IS EXPECTED TO CARRY A RAIN CHANCE INTO THE
EVENING HOURS BEFORE THE LOSS OF DIURNAL HEATING ENDS THE POTENTIAL
AFTER MIDNIGHT.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY

SURFACE LOW PRESSURE WILL CONTINUE TO EXIT THE AREA ON
WEDNESDAY...WHILE HIGH PRESSURE BEGINS TO EXPAND INTO THE NORTHERN
AND WESTERN GREAT LAKES. UPPER SHORTWAVE WILL DROP THROUGH THE U.P.
AND INTO ONTARIO LATE WEDNESDAY INTO WEDNESDAY NIGHT. THIS MAY
TRIGGER A FEW SHOWERS OR THUNDERSTORMS IN THE AFTERNOON/EVENING AS A
COLD FRONT IN THE PROCESS OF WASHING OUT DROPS DOWN INTO THE AREA
AND DAYTIME HEATING ALLOWS SOME SURFACE-BASED INSTABILITY TO BUILD.
BEST CHANCES FOR ANY ACTIVITY LOOK BEST OVER THE SAGINAW VALLEY AND
THUMB...AND EVEN THEN CHANCES DO NOT LOOK HIGH WITH LIMITED MOISTURE
AVAILABLE AND POTENTIAL FOR A MID-LEVEL CAP TO REMAIN IN PLACE.

SURFACE HIGH WILL SHIFT DOWN INTO THE CENTRAL GREAT LAKES ON
THURSDAY AND THURSDAY NIGHT. THIS WILL PROVIDE QUIET WEATHER AND
MOSTLY SUNNY SKIES FOR THE AFTERNOON. ONE MORE PIECE OF ENERGY IS
THEN EXPECTED TO DROP THROUGH THE LONGWAVE TROUGH THAT HAS BEEN
STUCK OVER THE GREAT LAKES AND NEW ENGLAND ON FRIDAY BEFORE THE
PATTERN SHIFTS. THE PROBLEM IS THAT MODELS ALL SEEM TO HANDLE THIS
ENERGY DIFFERENTLY...00Z GFS SLIDES IT THROUGH ONTARIO...12Z EURO
DROPS IT ACROSS MICHIGAN...AND THE 00Z GEM DROPS IT THROUGH THE
MIDWEST AND ACROSS THE OHIO VALLEY. EURO SOLUTION WOULD BE THE MORE
FAVORABLE ONE FOR SHOWERS/TSTORMS...BUT WITH POOR MODEL
CONTINUITY...WILL KEEP THE FORECAST DRY.

MODEL SOLUTIONS CONTINUE TO SHOW UPPER RIDGING SLIDING OVERHEAD FOR
THE HOLIDAY WEEKEND. THIS WOULD SUPPORT A DRY FORECAST AND A WARMING
TREND WITH MAX TEMPERATURES NUDGING TOWARDS 80 DEGREES. GFS/EURO
BOTH ARE KEYING IN ON AN UPPER LOW TRACKING THROUGH ONTARIO EARLY
NEXT WEEK BUT SHOW INCONSISTENCIES WITH TIMING. THIS WILL PROVIDE A
PERIOD OF SHOWERS/TSTORMS IN THE MONDAY OR TUESDAY TIMEFRAME.

&&

.MARINE...

LOW PRESSURE SLOWLY PASSING OVERHEAD WILL BRING RELATIVELY LIGHT
WINDS TODAY...OUTSIDE OF A PUSH OF 15 KNOT WEST WINDS LATE THIS
AFTERNOON AND EVENING OVER WESTERN LAKE ERIE. WINDS WILL THEN TURN
NORTHWESTERLY BEHIND A WEAK FRONT TONIGHT...BUT REMAIN 15 KNOTS OR
LESS. HIGH PRESSURE BUILDING INTO THE GREAT LAKES WILL THEN PROVIDE
QUIET WEATHER AND LIGHT WINDS WEDNESDAY THROUGH THURSDAY NIGHT.

&&

.AVIATION...ISSUED 1152 PM EDT MON JUN 29 2015

THE LOW LEVEL S-SE WINDS HAVE BEEN ADVECTING A STRATUS DECK
NORTHWARD THIS EVENING. SATELLITE TRENDS SUGGEST THESE CLOUDS WILL
EVENTUALLY LIFT NORTH INTO FNT AND MBS BY OR SHORTLY AFTER 06Z.
CLOUD BASES ARE EXPECTED TO TREND TOWARD MVFR OVER THE NEXT FEW
HOURS AS ADDITIONAL LOW LEVEL MOISTURE ARRIVES FROM THE SOUTHEAST.
THESE LOW CLOUDS WILL LIKELY PERSIST THROUGH DAYBREAK UNDER A
SHALLOW INVERSION BEFORE DAYTIME HEATING LIFTS THE CLOUDS TO A VFR
STRATO CU FIELD BY AFTERNOON.

FOR DTW...THERE HAVE BEEN A FEW OBSERVATIONS ACROSS NRN OHIO WITH
IFR CIGS IN THE VICINITY OF A WEAK SURFACE LOW. THIS FEATURE WILL
LIFT EAST OF METRO DETROIT 08-12Z AND WILL SUPPLY SOME ADDITIONAL
LOW LEVEL MOISTURE ADVECTION. THIS WILL REMAIN SUPPORTIVE OF A
PERIOD OF IFR CEILINGS AT METRO EARLY TUES MORNING.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CIGS BELOW 5000 FT TONIGHT AND TUES MORNING.

* MEDIUM IN THUNDERSTORMS TUESDAY AFTERNOON AND EVENING.

&&

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

$$

SHORT TERM...CB
LONG TERM....HLO
MARINE.......HLO
AVIATION.....SC


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



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