Severe Thunderstorm Warning 26, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
802 PM EDT MON JUN 22 2015

.AVIATION...

THE NEAR SURFACE PORTION OF THE ATMOSPHERE IS RECOVERING IN THE WAKE
OF EARLIER CONVECTION EVIDENCED BY BROAD SURFACE REPORTING OF
SOUTHWESTERLY WINDS OF 20 TO 25 KNOTS. THE QUESTION OUTSTANDING IS
WHERE EXACTLY THE EDGE OF THE MIDLEVEL LATENT HEATING/SUBSIDENCE CAP
RESIDES. LATEST LOOK ON VISIBLE SATELLITE SHOWS MUCH OF LOWER
MICHIGAN IS STILL UNDER THE GRIPS OF THE FEATURE WITH THE
CORRUGATED LOW CLOUD STRATOCUMULUS SUGGESTIVE OF SOME DUCTING
WITHIN A STABLE LAYER. WITH RECENT DISSIPATION OF CIRRUS WILL BE
LOOKING AT SOME ADDITIONAL RADIATIVE HEATING IN ADDITION TO THE
ADVECTION OF INSTABILITY WITHIN SW FLOW. THEREFORE...STILL
EXPECTING NUMEROUS TO WIDESPREAD DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS AHEAD OF AND THEN ALONG AND APPROACHING COLD FRONT.
BEST ESTIMATE ON ACTIVITY REACHING THE TERMINALS RANGES FROM 02Z
AT KMBS TO 05Z FOR KDTW. THE PASSAGE OF THE COLD FRONT WILL OCCUR
BETWEEN 09-12Z.

FOR DTW...WILL TAKE SOME TIME YET TO GET THUNDERSTORMS INTO THE DTW
TERMINAL. BEST ESTIMATE FOR DTW REMAINS AT/AFTER 05Z TONIGHT. STRONG
ENVIRONMENTAL WIND FIELDS WITH MODERATE INSTABILITY SUPPORTS A RISK
FOR SEVERE WEATHER TONIGHT.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIG AOB 5KFT TONIGHT.

* MEDIUM TO HIGH THUNDERSTORMS WILL IMPACT THE TERMINAL TONIGHT. LOW
  CONFIDENCE IN TIMING AND DURATION.

&&

.PREV DISCUSSION...ISSUED 337 PM EDT MON JUN 22 2015

SHORT TERM...TONIGHT

MASSIVE MCS OVER THE MIDWEST/WESTERN GREAT LAKES THIS MORNING HAS
BEEN WEAKENING/DIMINISHING THROUGH THE DAY AS IT TRACKS INTO LOWER
MICHIGAN...WITH IR CLOUD TOPS WARMING. LOW TO MODERATE INSTABILITY
OVER SOUTHEAST MICHIGAN THIS AFTERNOON...MLCAPES OF 500-1500 J/KG
WITH WARM FRONTAL ARM AT THE LEAD EDGE OF THE GOOD 0-6 KM BULK
SHEAR BACK ACROSS LAKE MICHIGAN. SURFACE WINDS HAVE VEERED TO THE
SOUTH-SOUTHWEST OVER SOUTHEAST MICHIGAN WHICH WILL GENERALLY
MINIMIZE TORNADO THREAT...BUT LOCALIZED BACK FLOW REMAINS
POSSIBLE. THE SEVERE THUNDERSTORM WATCH GOES UNTIL 9 PM...BUT MAY
BE DROPPED EARLY AS THE CENTER OF THE MCV WORKS EAST OF OUR
AREA...AND WE RESIDE IN THE SUBSIDENCE WAKE.

ATTENTION THEN TURNS TO THE ACTUAL COLD FRONT...DRIVEN SOUTHEAST BY
THE IMPRESSIVE NORTHERN STREAM UPPER LEVEL WAVE/CIRCULATION WORKING
THROUGH NORTHERN MINNESOTA AT THE PRESENT TIME. THE COLD FRONT LOOKS
TO BE ARRIVING CLOSE TO MIDNIGHT. 12Z EURO SHOWS GOOD DEEPENING OF
THE SURFACE LOW TACKING INTO ONTARIO...AND SHOULD HELP ACCELERATE
THE COLD FRONT OFF THE EAST...CERTAINTY DRYING OUT BY 12Z TUESDAY.
SEVERE THUNDERSTORM CHANCES TONIGHT ARE DEPENDENT ON THE AMOUNT OF
RECOVERY THIS EVENING...AS INCREASING HEIGHT FALLS AND LOW LEVEL JET
(50 KNOTS AT 850 MB) CERTAINLY ARGUES FOR SEVERE THREAT. THROW IN
THE FACT INSTABILITY REMAINS MODERATE TO HIGH (MLCAPES 2500+ J/KG
PER 18Z SPC ANALYSIS) ACROSS WESTERN OHIO VALLEY AND SOME ADVECTION
TAKES PLACE INTO EXTREME SOUTHERN LOWER MICHIGAN...WILL NEED TO
CLOSELY MONITOR UPSTREAM DEVELOPMENT WHICH COULD POTENTIALLY LEAD TO
BIG WIND THREAT.

LONG TERM...TUESDAY THROUGH MONDAY

FOLLOWING THE COLD FRONT TONIGHT...HIGH PRESSURE WILL DEVELOP OVER
LOWER MICHIGAN FOR TUESDAY. THE SURFACE HIGH WILL BE WEAK AND THE
UPPER RIDGE WILL BE LOW AMPLITUDE AND PROGRESSIVE BUT GOOD ENOUGH TO
KEEP SE MICHIGAN DRY THROUGH TUESDAY NIGHT. COOLER AND LESS HUMID NW
WIND WILL KNOCK MAX TEMPS DOWN A CATEGORY OR TWO INTO THE UPPER 70S
AND LOWER 80S.

WEDNESDAY WILL BE THE TRANSITION DAY INTO THE NEXT ROUND OF ACTIVE
WEATHER. SE MICHIGAN WILL BE IN BETWEEN A BACKDOOR FRONT OVER THE
NORTHERN GREAT LAKES AND THE PRIMARY FRONTAL ZONE STILL OVER THE
OHIO VALLEY. LOW AMPLITUDE SHORT WAVE ENERGY IN THE UPPER LEVEL
WESTERLIES WILL HAVE LOW PREDICTABILITY IN THE MODEL DATA BUT THERE
IS GENERAL AGREEMENT IN A PATTERN OF ELEVATED SHOWERS/WEAK STORMS
WEDNESDAY NIGHT INTO EARLY THURSDAY. THE MAIN QUESTION IS WHETHER
LOW PRESSURE WILL BE STRONG ENOUGH TO PULL THE PRIMARY OHIO VALLEY
FRONT BACK NORTH INTO LOWER MICHIGAN LATER THURSDAY INTO THURSDAY
NIGHT. THE PREPONDERANCE OF 12Z MODEL SOLUTIONS INDICATES A WEAKER
WAVE RIPPLING ALONG THE FRONT AS IT LINGERS SOUTH OF THE OHIO
BORDER. EVEN WITHOUT THE OTHER SOLUTIONS AS SUPPORT...THE GFS
APPEARS TO SUFFER FROM OVER-DEVELOPED SURFACE FEATURES DUE TO
UPSCALE GROWTH OF CONVECTION. IT DOES OUTLINE WHERE THE UNCERTAINTY
WILL BE IN THE FORECAST DURING THIS TIME PERIOD...MAINLY IN THE
POSSIBILITY OF A FARTHER NORTH TRACK OF A WEAKER WAVE THAT WOULD
FOCUS GREATER COVERAGE OF CONVECTION OVER OUR AREA IN LATER
FORECASTS.

A FEW LINGERING SHOWERS COULD BE POSSIBLE EARLY FRIDAY MORNING AS
LOW LEVEL MOISTURE STICKS AROUND AND THE DEPARTING LOW PRESSURE
TRACKS EASTWARD. HIGH PRESSURE THEN BUILDS INTO THE REGION DURING
THE DAY ON FRIDAY AND LASTS THROUGH SUNDAY. THIS WILL RESULT IN DRY
CONDITIONS THROUGH THE WEEKEND. HIGH TEMPERATURES WILL HOLD
STEADY IN THE MID 70S FRIDAY THROUGH SUNDAY. OVERNIGHT LOW
TEMPERATURES WILL ALSO HOLD IN THE UPPER 50S TO 60S THROUGH SUNDAY
NIGHT.

MARINE...

THE MARINE HAZARDS PRESENTED BY THE SEVERE THUNDERSTORM PATTERN
REMAIN VALID THROUGH TONIGHT. SMALL CRAFT ADVISORIES ALSO REMAIN
IN EFFECT AS SOUTHERLY WINDS INCREASE TODAY AHEAD OF STRONG LOW
PRESSURE TRACKING THROUGH LAKE SUPERIOR TONIGHT. THERE WILL ALSO
BE A PERIOD OF STRONGER WEST TO NORTHWEST WINDS ALONG AND BEHIND
THE ASSOCIATED COLD FRONT TONIGHT INTO TUESDAY. GUST POTENTIAL
WILL BE LIMITED SOMEWHAT BY STABILITY OVER THE COOLER WATER OVER
THE OPEN WATERS...HOWEVER THERE WILL BE POTENTIAL FOR GUSTS OF 25
TO 30 KNOTS OVER ALL MARINE AREAS...EITHER IN THE SOUTHERLY FLOW
AHEAD OF THE FRONT OR IN THE WEST/NORTHWEST FLOW BEHIND THE FRONT.
THE WIND WILL DECREASE TUESDAY AFTERNOON AS HIGH PRESSURE BUILDS
INTO THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 AM EDT TUESDAY FOR LHZ421-422-441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 10 AM EDT TUESDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT TUESDAY FOR LEZ444.

&&

AVIATION.....CB
SHORT TERM...SF
LONG TERM....BT/RK
MARINE.......BT

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