Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDTX 070357
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1157 PM EDT MON JUL 6 2015

.AVIATION...

MOISTURE SURGING NORTHWARD AHEAD OF THE COLD FRONT WILL CONTINUE TO
SUPPORT SHOWERS WITH THE GREATEST COVERAGE IN THE MBS AREA DURING
THE PRE-DAWN HOURS...ALONG WITH A FEW THUNDERSTORMS. SOME IFR WITHIN
FRONTAL ZONE WILL ALSO BE POSSIBLE THERE AS THE FRONT MOVES THROUGH
DURING THE COOLEST PART OF THE DAY. DAYTIME SURFACE HEATING WILL
LIKELY BE ABLE TO PREVENT IFR DEVELOPMENT FARTHER SOUTH/LATER IN THE
DAY BUT POTENTIAL REMAINS FOR SOLID MVFR CEILING WITH INCREASING
SHOWER COVERAGE AND ESPECIALLY WITH THE APPROACH/PASSAGE OF THE COLD
FRONT. THE POST FRONTAL WIND SHIFT TOWARD THE NORTH WILL BRING A
RAPID IMPROVEMENT IN CEILING FROM MID TUESDAY AFTERNOON INTO TUESDAY
EVENING.

FOR DTW... FRONTAL TIMING AT DTW IN 15-18Z TIME FRAME WILL BE
SUBJECT TO ADJUSTMENTS BASED ON EVENTUAL COVERAGE OF SHOWERS DURING
THE MORNING. GREATER COVERAGE WILL SUPPORT FASTER TIMING...GREATER
INTENSITY WILL SUPPORT SLOWER TIMING.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILING 5000 FEET OR LESS LATE MORNING THROUGH AFTERNOON
  ALONG AND BEHIND COLD FRONT.

* LOW FOR THUNDERSTORMS ALONG AND AHEAD OF COLD FRONT.

&&

.PREV DISCUSSION...ISSUED 943 PM EDT MON JUL 6 2015

UPDATE...

MID EVENING CONVECTION IS SURVIVING THE TRIP ACROSS LAKE
MICHIGAN AND INCREASING IN COVERAGE AS LOW LEVEL MOISTURE
TRANSPORT GENERATES ELEVATED INSTABILITY. UPDATED RAP OUTPUT
INDICATES 850 MB LI RUNNING NEAR -3C AND MATCHED UP WELL WITH THE
STRONGEST SHOWERS AND A FEW THUNDERSTORMS. EXPECT THIS PLUME OF
INSTABILITY WILL SPREAD STEADILY ACROSS LOWER MICHIGAN DURING THE
NIGHT. BOTH THE DTX AND APX 00Z SOUNDINGS ARE IMPRESSIVELY CAPPED
AND ARE A SNAPSHOT OF THE PREEXISTING LARGE SCALE ENVIRONMENT
THAT WILL CHANGE CONSIDERABLY OVER THE NEXT FEW HOURS. THE
INCREASING LOW LEVEL JET STRENGTH AND ASSOCIATED MOISTURE
ADVECTION IN SOUTHWEST LOW LEVEL FLOW WILL CONTINUE TO DESTABILIZE
THE PROFILE FROM BELOW. THERE IS NOT MUCH COOLING ALOFT BUT WEAK
HEIGHT FALLS AND SYNOPTIC SCALE LIFT WILL PROVIDE A MODEST
CONTRIBUTION TO THE PROFILE ALOFT. STILL EXPECT LIKELY/NUMEROUS
COVERAGE SPREADING NW TO SE OVER THE REGION DURING THE NIGHT
THROUGH TUESDAY MORNING. THE PREVIOUS FORECAST REASONING REMAINS
VALID REGARDING SEVERE POTENTIAL BEING LIMITED BY LOW OVERALL
INSTABILITY. A WEAK WIND PROFILE AND 14 KFT FREEZING LEVEL IS
ALSO A NEGATIVE FACTOR FOR ANYTHING MORE THAN FREQUENT LIGHTNING
STRIKES AND HEAVY DOWNPOURS.

PREV DISCUSSION...ISSUED 353 PM EDT MON JUL 6 2015

SHORT TERM...THROUGH TONIGHT

HIGH STABILITY SHOWN ON KDTX RAOB THIS MORNING...INDICATIVE OF THE
UPPER RIDGE STILL LINGERING OVER THE AREA...WILL KEEP THE WEATHER
DRY AND QUIET THROUGH THE REMAINDER OF TODAY. CU FIELD OVER WESTERN
MICHIGAN HAS BEEN EXPANDING EASTWARD THIS AFTERNOON AS SOUTHERLY
FLOW HAS ALLOWED FOR A SLOW BUT STEADY INCREASE IN MOISTURE UNDER AN
INVERSION. RADAR IMAGERY OVER WISCONSIN SHOWS SHOWERS AND
THUNDERSTORMS BEGINNING TO BREAK OUT AHEAD OF A COLD FRONT AND AHEAD
OF A STRONG UPPER SHORTWAVE THAT CAN BE SEEN ON WATER VAPOR IMAGERY
TRACKING ACROSS WISCONSIN. THE STRONGEST STORMS ARE FIRING JUST
AHEAD OF THE UPPER WAVE AND WHERE LOW-LEVEL THETA-E ADVECTION LOOKS
THE STRONGEST PER NAM/GFS. THE UPPER SHORTWAVE WILL TRACK THROUGH
NORTHERN MICHIGAN THIS EVENING AND OVERNIGHT...SPREADING SHOWERS AND
A FEW THUNDERSTORMS EAST. CONSENSUS OF THE LATEST HI-RES AND GLOBAL
MODELS HAS BEEN TO SPEED UP THE ARRIVAL OF PRECIPITATION
SLIGHTLY...PARTICULARLY OVER NORTHERN MICHIGAN AND LAKE HURON. NEWER
TIMING DOES LOOK GOOD...AS MODELS SEEM TO HAVE GOTTEN A BETTER
HANDLE ON THE PLACEMENT AND STRENGTH OF THE UPPER WAVE OVER
WISCONSIN...AND WITH A LOW-LEVEL JET THAT WILL INCREASE MOISTURE AND
ELEVATED INSTABILITY OVER LOWER MICHIGAN LATER TONIGHT. EXPECT
PRECIPITATION TO SPREAD INTO THE AREA AFTER MIDNIGHT AS DEEPER
MOISTURE AND INSTABILITY ARRIVE...WITH HIGHEST POTENTIAL OVER THE
SAGINAW VALLEY TOWARDS SUNRISE. A FEW THUNDERSTORMS WILL ALSO BE
POSSIBLE BUT EXPECT OVERALL COVERAGE TO BE LIMITED. WARMER AIR ALOFT
SURGING IN WITH THE LOW-LEVEL JET WILL KEEP ACTIVITY (AND
INSTABILITY) ELEVATED AND EVEN MID-LEVEL LAPSE RATES ARE NOT ALL TOO
IMPRESSIVE. SEVERE WEATHER IS NOT ANTICIPATED.

MIN TEMPERATURES WILL BE ON THE WARM SIDE WITH INCREASING
CLOUDS...RISING DEWPOINTS...AND AROUND 10 MPH OF WIND FROM THE
SOUTH. ONLY EXPECTING LOWS TO FALL INTO THE MID 60S TO NEAR 70.

LONG TERM... TUESDAY THROUGH SUNDAY

STEADY SOUTHEASTWARD EXPANSION OF LOWER HEIGHTS UNDERWAY ACROSS THE
NORTHERN PLAINS THIS AFTERNOON...PROMPTED BY A COMBINATION OF A
STRONGER INBOUND WAVE ENTERING NORTH DAKOTA AND A WEAKER IMPULSE
LIFTING INTO SOUTHERN MINNESOTA.  THE SOUTHERN EXTENT OF THESE
HEIGHT FALLS WILL CONTINUE EASTWARD OVER THE NEXT 24 HOURS...
EFFECTIVELY SHIFTING THE ATTENDANT COLD FRONT ACROSS SE MICHIGAN ON
TUESDAY.  A PERIOD OF DEEPER PRE-FRONTAL SOUTHWEST FLOW WILL DRAW
THE RESERVOIR OF HIGHER MOISTURE EXISTING JUST UPSTREAM /PW VALUES
AROUND 2 INCHES/ INTO THE REGION LATE TONIGHT AND EARLY TUESDAY.
DIMINISHING STABILITY AS THIS PROCESS UNFOLDS AND WITH THE ONSET OF
DAYTIME HEATING WILL PROVIDE A FAVORABLE BACKGROUND ENVIRONMENT FOR
SHOWER AND THUNDERSTORM DEVELOPMENT/MAINTENANCE AS MODEST FRONTAL
CONVERGENCE TRANSLATES THROUGH DURING THE DAYLIGHT PERIOD.

THE OVERALL POTENTIAL FOR DEEPER CONVECTIVE GROWTH AND ORGANIZATION
APPEARS LIMITED.  MAIN CORRIDOR OF HEIGHT FALLS AND FAVORABLE
ENTRANCE REGION UPPER JET SUPPORT WILL SHIFT INTO SOUTHERN CANADA
DURING THIS TIME...LEAVING SE MICHIGAN LARGELY POSITIONED SOUTH OF
THE GREATER MID LEVEL ASCENT AND CORRESPONDING DEEP LAYER WIND
FIELD.  IN ADDITION...RESIDUAL WARMER MID LEVEL TEMPERATURES AND
QUESTIONABLE PROSPECTS FOR GREATER BOUNDARY LAYER DESTABILIZATION
GIVEN AN EARLIER FRONTAL TIMING /CENTERED 14Z-18Z/ WILL LEAVE PALTRY
LOW AND MID LEVEL LAPSE RATES IN PLACE.  12Z NAM AGAIN RUNNING HIGH
ON PROJECTED DEWPOINTS /3-5 DEGREES TOO MOIST/...YIELDING AN
OVERZEALOUS EARLY AFTERNOON CONVECTIVE RESPONSE.  A MORE MODIFIED
PARCEL WITH A T/TD OF 80/70 DOES ALLOW FOR MLCAPE VALUES WITHIN THE
1000-1500 J/KG RANGE.  THIS COULD PROVE SUFFICIENT TOWARD SUPPORTING
A FEW STRONGER UPDRAFTS...WITH A CORRESPONDING WINDOW FOR GUSTY
WINDS.  MAIN ISSUE GIVEN THE HIGH MOISTURE CONTENT WILL BE LOCALLY
HEAVY RAINFALL.

PROGRESSIVE POST-FRONTAL DRYING LATE TUESDAY INTO TUESDAY EVENING
FROM NORTHWEST TO SOUTHEAST.  THIS WILL LEAD IN A BRIEF PERIOD OF
DRY/STABLE CONDITIONS TUESDAY NIGHT AND WEDNESDAY AS HIGH PRESSURE
BUILDS ACROSS THE REGION.  HIGHS WEDNESDAY OF LOWER AND MIDDLE 70S
WITH NOTICEABLY LOWER HUMIDITY RELATIVE TO TUESDAY.

MID LEVEL FLOW TRANSITIONS TO LOWER AMPLITUDE SOUTHWESTERLIES
IMMEDIATELY UPSTREAM OF EXPANDING SUBTROPICAL RIDGING TAKING HOLD
OVER THE SOUTHEAST U.S.  THIS EVOLUTION WILL POTENTIALLY RESULT IN A
PERIODICALLY ACTIVE PERIOD THROUGH THE LATTER HALF OF THE LONG TERM
PERIOD.  THIS PROCESS WILL INITIATE WEDNESDAY NIGHT AND THURSDAY AS
A LEAD WAVE EJECTS OUT OF THE GROWING UPPER HEIGHT FIELD ACROSS THE
SOUTHERN CONUS.   RESPECTABLE SURFACE WAVE APPEARS TO EMERGE WITH
THIS FEATURE...RESULTING IN A COMPACT BUT STRONG CORRIDOR OF FORCING
AND ACCOMPANYING MOISTURE TRANSPORT THAT SHIFTS INTO THE OHIO
VALLEY/GREAT LAKES DURING THIS TIME.  EXACT TIMING AND POSITIONING
REMAINS SOMEWHAT ILL-DEFINED YET...POTENTIAL FOR AT LEAST NORTHERN
PORTIONS OF SOUTHEAST MICHIGAN TO REMAIN NORTH OF THE EVENTUAL
PRECIPITATION SWATH.  THIS CONTINUES TO WARRANT A BROADER AND MORE
CONSERVATIVE DISTRIBUTION OF PRECIPITATION CHANCES AT THIS STAGE.
THE EXTENSIVE HIGHER CLOUD AND EASTERLY LOW LEVEL GRADIENT WILL CAP
HIGHS IN THE 70S THURSDAY...REGARDLESS OF PRECIPITATION
TIMING/COVERAGE.

FRIDAY INTO NEXT WEEKEND...UPPER LEVEL ANTICYCLONE OVER THE
SOUTHEASTERN US WILL EXPAND NORTH/WESTWARD. THIS LOOKS TO RAISE
HEIGHTS LOCALLY TO SOME DEGREE LEADING TO A MODEST WARMING TREND.
THIS DOES NOT LOOK TO BE A CLEAN PROCESS THOUGH WITH THE PASSAGE OF
A FEW SHORTWAVES IN QUASI-ZONAL FLOW ALLOWING FOR PRECIP CHANCES TO
CONTINUE THROUGH THIS PERIOD.

MARINE...

MODERATE SOUTHERLY FLOW TONIGHT WILL SHIFT TO SOUTHWESTERLY TUESDAY
AS A COLD FRONT SETTLES ACROSS THE REGION.  THIS FRONT WILL BRING A
GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS ON TUESDAY.  POST-FRONTAL
10 TO 20 KNOT NORTHWEST WINDS DEVELOP LATE TUESDAY AND TUESDAY
EVENING.  WINDS THEN DIMINISH TUESDAY NIGHT INTO EARLY WEDNESDAY AS
HIGH PRESSURE BUILDS ACROSS THE REGION.  A PERIOD OF MODEST EASTERLY
FLOW MAY DEVELOP AS LOW PRESSURE TRACKS THROUGH THE OHIO VALLEY ON
THURSDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
UPDATE.......BT
SHORT TERM...HLO
LONG TERM....MR/DT
MARINE.......MR


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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.