Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251433
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1033 AM EDT SAT JUL 25 2015

.UPDATE...

CURRENT FORECAST ON TRACK FOR SATURDAY AFTERNOON AND EVENING. 12Z
SOUNDING FOR DTX SUGGESTS ABOUT 1000 K/KG OF ML CAPE WITHOUT ANY
ADDITIONAL MOISTURE ADVECTION IN THE MIXED LAYER. THERE IS SOME
POOLING OF THAT MOISTURE ALONG THE FRONT GIVEN THE DEW POINTS IN
THE UPPER 60S TO AROUND 70 FOR EXTREME SE WI AND NRN IL. STILL
SOME QUESTION IF WE GET ALL OF THAT LOW LEVEL MOISTURE TO REALIZE
2000 J/KG OF ML CAPE...BUT THERE SHOULD BE ENOUGH OF AN INCREASE
TO GET IN THE 1500 J/KG NEIGHBORHOOD. WIND FIELDS MAY BE STRONGEST
THIS MORNING AND ACTUALLY WEAKEN THROUGH THE AFTERNOON. STILL MAY
BE ENOUGH FOR SOME ORGANIZATION OF THE CONVECTION AND MAYBE ONE OR
TWO STORMS TO GET CLOSE TO SEVERE LIMITS. 00Z HI RES RUNS ALL
WERE BULLISH ON MORNING CONVECTION ACROSS NRN AND WC LOWER WHICH
WOULD HAVE IMPACTS ON ITS DEPICTION OF CONVECTION FOR SE LOWER.
THE LATER HRRR AND RAP/RUC CYCLES ARE A LITTLE BETTER AND CONTINUE
THE IDEA OF 16-20Z TIMING FOR THE TRI CITIES...18-22Z FOR THUMB TO
ARB AND 20-00Z FOR METRO DETROIT.

CLOUDS WERE QUITE VARIABLE ACROSS LOWER MICHIGAN. EXPECT THAT TO
CONTINUE AS THE LOWER SC LIFTS INTO A CU FIELD WHILE AREAS OF AC
CONTINUE TO MOVE ACROSS THE REGION. END RESULT SHOULD BE ENOUGH
SUN TO REACH FORECAST HIGHS WHILE THERE WILL NOT BE TOO MUCH SUN
TO GO ANY HIGHER.

&&

.AVIATION...ISSUED 603 AM EDT SAT JUL 25 2015

A COLD FRONT WILL SWEEP THROUGH THE REGION TODAY...AROUND 16Z FOR
MBS AND 21Z FOR DTW...BRINGING A WINDOW OF LOWER CIGS AND POSSIBLE
TSTORMS. VFR CONDITIONS WILL PREVAIL BOTH BEFORE AND AFTER THIS
NARROW WINDOW OF THE FRONTAL PASSAGE IN WHICH MVFR CIGS/VSBYS MAY
OCCUR. CONFIDENCE IS LOW WITH COVERAGE OF POTENTIAL TSTORMS AS
SIGNALS ARE POINTING TO ISOLATED/SCATTERED COVERAGE. WILL INCLUDE A
BRIEF 2 HOUR TEMPO TO ACCOUNT FOR THIS NARROW WINDOW OF POTENTIAL
FOR PTK SOUTHWARD WITH JUST SHOWERS FOR FNT/MBS DUE TO EARLIER
TIMING AND LESS INSTABILITY. NORTHERLY WINDS BEHIND THE FRONT WILL
BRING DRIER AIR BACK TO THE AREA ERODING THE CLOUDS THIS EVENING
INTO THE OVERNIGHT FROM NORTH TO SOUTH. WINDS WILL BRIEFLY INCREASE
FROM THE SW AHEAD OF THE FRONT BUT WILL RELAX SOME OVERNIGHT AS
WIND SWITCH TO NORTHERLY WITH THE NEXT HIGH SETTLING IN.

FOR DTW...COLD FRONT LOOKS TO BE MOVING THROUGH DURING PEAK HEATING
OF SATURDAY...WARRANTING THE TEMPO FOR TSTORMS FROM 20-22Z. UPSTREAM
OBS AND FORECAST SOUNDINGS SUGGEST CIGS WILL HOVER NEAR THE VFR/MVFR
THRESHOLD BUT THINKING IS VFR WILL DOMINATE WITH MVFR BEING MORE
SCATTERED SO WILL FAVOR VFR WITH THE TAFS.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM FOR CIGS AOB 5KFT SATURDAY AFTERNOON AND EVENING.

* LOW FOR THUNDERSTORMS SATURDAY AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 356 AM EDT SAT JUL 25 2015

SHORT TERM...TODAY AND TONIGHT

A WEAKENING COLD FRONT WILL PASS THROUGH LOWER MI TODAY BRINGING THE
CHANCE OF SHOWERS AND THUNDERSTORMS. THE PARENT LOW FOR THE FRONT IS
LOCATED OVER NORTHERN ONTARIO AND WILL CONTINUE SLOWLY EASTWARD
THROUGH THE DAY WHILE THE FRONT PIVOTS AROUND IT AND THROUGH THE
AREA. THE TIMING OF THE FRONT PASSAGE WILL BE IN THE AFTERNOON
AROUND 18-00Z...DURING PEAK HEATING. THIS WILL OF COURSE FAVOR STORM
DEVELOPMENT AS SFC TEMPS REACH INTO THE LOW/MID 80S WITH DEWPOINTS
LOOKING TO REACH 70. WILL CONTINUE WITH CHANCE POPS FOR SHOWERS AND
THUNDERSTORMS TODAY WITH THE MAIN ADJUSTMENT COMING IN THE TIMING OF
THE PRECIP...ELIMINATING ALL POPS BEFORE 14Z AS THE LINE OF
CONVECTION IS STILL FAR TO THE WEST OVER CENTRAL WI. DETAILS OF THE
SETUP TO FOLLOW...

THE UPPER LEVEL JET MAX HAS WORKED ITS WAY ACROSS THE MS RIVER AND
WILL REACH MID MI THIS MORNING. MODELS ALL SHOW THIS TO WEAKEN
THROUGH THE DAY FROM 100 KNOTS DOWN TO AROUND 70 KNOTS. THIS WILL
ALLOW DECENT SHEAR AHEAD OF THE FRONT WITH 0-3KM VALUES AROUND 25-30
KNOTS WHICH WILL BE ENOUGH TO TRY TO ORGANIZE SOME STORMS THAT CAN
DEVELOP. THIS WILL HELP COMPENSATE SOMEWHAT FOR THE LACK OF NOTABLE
FRONTAL FORCING ANYWHERE ALONG THE FRONT. AS HAS BEEN THE CASE MUCH
OF THE CONVECTIVE SEASON...MID LEVEL LAPSE RATES LOOK TO BE VERY
WEAK ONCE AGAIN BUT LL LAPSE RATES WILL BE PRETTY GOOD AS SFC TEMPS
QUICKLY RISE INTO THE MID 80S ONCE AGAIN. CAPE WILL ALSO BE
FAVORABLE AS A CORRIDOR OF 70 DEGREE DEWPOINTS AHEAD OF THE FRONT
SLIDES THROUGH THE AREA. A FAIR VALUE LOOKS TO BE AROUND 1500-2000
J/KG AVAILABLE THIS AFTERNOON. BEST CHANCES FOR ORGANIZED...POSSIBLE
STRONG TO SEVERE...STORMS WILL BE OVER THE SOUTHERN AND EASTERN
LOCATIONS AS THEY WILL HAVE SEVERAL ADDITIONAL HOURS OF HEATING TO
WORK WITH. IN ADDITION THERE APPEARS TO BE A SECONDARY COLD FRONT OR
SHORTWAVE SLIDING IN THIS AFTERNOON WHICH MAY PROVIDE A LITTLE EXTRA
BOOST LATER IN THE DAY. FOR ANY ONE LOCATION THERE LOOKS TO BE
AROUND A 3-5 HOUR WINDOW WHERE THESE ISOLATED TO SCATTERED STORMS
COULD IMPACT THEM. MBS WILL START EARLY IN THE DAY AS THE FRONT
APPROACHES AROUND 14Z...WHICH WILL LIMIT STRENGTH OF THESE
STORMS...WITH DTW HOLD OFF TIL CLOSER TO 18-20Z FOR A START TIME.
ALL ACTIVITY LOOKS TO PASS TO THE SOUTH/EAST BY 00Z. ANY ORGANIZED
STORM WILL HAVE THE POTENTIAL TO PRODUCE 60 MPH GUSTS AND/OR LARGE
HAIL. SPC HAS SOUTHEAST LOWER MI INCLUDED IN THE MARGINAL RISK AREA
WHICH SEEMS REASONABLE FOR THE SETUP.

ONCE THE FRONT PASSES...HIGH PRESSURE WILL CLEAR OUT THE CLOUDS FOR
THE OVERNIGHT BUT TEMPS WILL REMAIN ELEVATED AS THE POST FRONTAL
AIRMASS IS SPORTING DEWPOINTS IN THE LOW 60S.

LONG TERM... SUNDAY THROUGH FRIDAY

A TEMPORARY DIP IN THE UPPER HEIGHT FIELD OVER THE NEXT 24 HOURS
WILL HELP EASE THE ATTENDANT WEAK FRONT INTO THE OHIO VALLEY BY
EARLY SUNDAY.  POST-FRONTAL ENVIRONMENT SUNDAY WILL BE MORE NOTABLE
FOR A REDUCTION IN HUMIDITY RELATIVE TO TODAY...WITH NO REAL CHANGE
EXPECTED IN THE TEMPERATURES.  THE DRIER AND MORE STABLE CONDITIONS
AS HIGH PRESSURE SLIDES THROUGH WILL TRANSLATE INTO A HIGH DEGREE OF
SUNSHINE.  THIS INSOLATION POTENTIAL INTO A DRIER AND MODESTLY MIXED
PROFILE FAVORS A GREATER DIURNAL TEMPERATURE RESPONSE...AND WILL
NUDGE HIGHS UP A COUPLE DEGREE ACCORDINGLY FOR SUNDAY AFTERNOON.
GOING FORECAST HOLDING FIRM WITH EXPECTATIONS THAT CONVECTIVE
ACTIVITY THAT EMERGES ALONG THE FRONTAL ZONE WILL REMAIN SOUTH OF
THE BORDER SUNDAY AND SUNDAY NIGHT.

PREDOMINANT SOUTHERN CONUS UPPER RIDGING WILL UNDERGO STEADY
AMPLIFICATION INTO THE GREAT LAKES THROUGH THE EARLY WEEK PERIOD.
THE ACCOMPANYING RISE IN MEAN THICKNESSES THROUGHOUT THE COLUMN WILL
TRANSLATE INTO SEVERAL DAYS OF ABOVE NORMAL WARMTH.  WARMEST
CONDITIONS CENTERED ON THE TUESDAY AND WEDNESDAY PERIODS AS THE
UPPER RIDGE AXIS PIVOTS OVERHEAD...850 MB TEMPERATURES REACHING INTO
THE 18 TO 20C RANGE DURING THIS TIME.  THIS WILL SUPPORT READINGS IN
THE VICINITY OF 90 DEGREES BOTH DAYS.  CONVECTIVE POTENTIAL HAMPERED
BY THE INCREASING MID LEVEL TEMPERATURES AND LACK OF SUFFICIENT
FORCING BOTH MONDAY AND TUESDAY.  NEXT FRONTAL PASSAGE CENTERED
WITHIN THE WEDNESDAY AND WEDNESDAY NIGHT PERIODS...AS THE SOUTHERN
EXTENT OF HEIGHT FALLS ASSOCIATED WITH A DEEPENING WAVE LIFTING INTO
SOUTHERN CANADA ENTERS THE GREAT LAKES.  THIS WILL PROVIDE THE NEXT
OPPORTUNITY FOR THUNDERSTORM DEVELOPMENT.  COOLER...OR A TRANSITION
BACK TOWARD NORMAL...TEMPERATURES IN THE WAKE OF THE FRONT FOR THE
END OF THE WORK WEEK.

MARINE...

A COLD FRONT ACROSS LAKE HURON AND LOWER MICHIGAN TODAY.  THIS FRONT
WILL BRING A CHANCE OF THUNDERSTORMS TO ALL MARINE AREAS.   MODERATE
SOUTHWESTERLY WINDS IN ADVANCE OF THIS FRONT...SHIFTING TO NORTH
POST FRONT THROUGH EARLY TONIGHT.  WEAK HIGH PRESSURE SETTLING
ACROSS THE REGION WILL BRING FAVORABLE MARINE CONDITIONS SUNDAY
THROUGH EARLY NEXT WEEK.

&&

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

$$

UPDATE.......RBP
AVIATION.....DRK
SHORT TERM...DRK
LONG TERM....MR
MARINE.......MR


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


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