Severe Thunderstorm Warning 42, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
325 PM EDT SUN AUG 2 2015

.SHORT TERM...THIS AFTERNOON AND TONIGHT

SCATTERED CONVECTION CONTINUES TO BUBBLE OVER FAR NORTHERN CWA ALONG
WEST TO EAST OUTFLOW BOUNDARY STALLED OVER THAT AREA ALONG SOUTHERN
PERIPHERY OF CONVECTIVE CLUSTER TRACK(S) FROM THIS MORNING AND EARLY
AFTERNOON. EXPECT THIS ACTIVITY TO GRADUALLY INCREASE IN COVERAGE
THROUGH THE REST OF THE AFTERNOON...AT LEAST NORTH OF THE INTERSTATE
69 CORRIDOR. GIVEN THE DEGREE OF INSTABILITY ADVECTING INTO AREA FROM
THE WEST AND SOUTHWEST AND FEEDING THIS ACTIVITY...EXPECT SOME OF
THESE STORMS TO BE SEVERE. TO THIS POINT...THIS ACTIVITY HAS HAS
REMAIN CONFINED TO THE SAGINAW VALLEY AND NORTHERN THUMB. IF THIS
REMAINS THE CASE...LATER ACTIVITY THIS EVENING SHOULD HAVE A
STRAIGHT SHOT INTO THE AREA WITHIN TOO MUCH IMPEDANCE FROM
STABILIZATION IN THE WAKE OF THIS LEAD CLUSTER OF SEVERE STORMS.

THIS MAIN WIDESPREAD ACTIVITY...WHICH WILL SPREAD SOUTHWARD THROUGH
THE AREA THIS EVENING...STILL LOOKS TO ORGANIZE FROM VARIOUS
CONVECTIVE CLUSTERS CURRENTLY ACTIVE OVER NORTHERN WISCONSIN AND
WESTERN NORTHERN LOWER MICHIGAN. AS A COLD FRONT AND STRONG UPPER
LEVEL SUPPORT FROM AMPLIFYING UPPER TROUGH WORK INTO THE
REGION...THESE CLUSTERS SHOULD COMBINE INTO A PRETTY SOLID LINE (OR
TWO) OF STORMS AND ACCELERATE THROUGH SOUTHEAST LOWER MICHIGAN FROM
MID TO LATE EVENING. WHILE LATE DAY INSTABILITY...CURRENTLY 2500
J/KG OF MLCAPE...WILL EASE BY THIS TIME...HIGH BULK SHEAR FROM
STRONG WIND FIELD...ALONG WITH GENERAL UPSCALE ORGANIZATION OF THE
MESOSCALE SYSTEM...SHOULD SUPPORT RATHER WIDESPREAD WIND DAMAGE.

AS OF 3 PM...IT APPEARS THE STORM CLUSTER THAT WILL LIKELY BECOME
OUR MAIN EVENT THIS EVENING IS ORGANIZING OVER NORTHERN WISCONSIN AS
THE FULL UPPER SUPPORT OF THE DEEPENING SHORTWAVE TROUGH IS NOW
SPREADING INTO THIS AREA. THIS CURRENT LOCATION SUPPORTS A SLIGHTLY
FASTER ADVANCE INTO THE AREA BY PERHAPS 1 OR 2 HOURS -VS- THE
PREVIOUS FORECAST THINKING. THIS BASICALLY FOCUSES THIS NEXT ROUND
OF SEVERE THUNDERSTORMS AT 23Z-00Z OVER THE FAR NORTHERN CWA TO 01Z-
02Z FLINT INTO NORTHERN METRO DETROIT...AND QUICKLY SOUTH FROM THERE
THE REST OF THE EVENING AS WHAT WILL MOST LIKELY BE A FORWARD
PROPAGATING MCS MATURES AND RACES THROUGH LOWER MICHIGAN.

&&

.LONG TERM...

UPPER LOW CENTER WILL SLOWLY TRACK FROM ONTARIO TO QUEBEC MONDAY AND
TUESDAY. THIS WILL KEEP THE NORTHERN AND CENTRAL GREAT LAKES
CONFINED WITHIN COOLER WEST TO NORTHWEST FLOW AROUND THE BACKSIDE OF
THE SYSTEM. COOLER AND QUIETER WEATHER CAN BE EXPECTED FOR THE FIRST
PART OF THE WORK WEEK...ALTHOUGH A FEW SHORTWAVE TROUGHS WILL STILL
PIVOT DOWN ACROSS MICHIGAN. MODELS ARE STILL KEYING IN ON A
SECONDARY COLD FRONT DROPPING DOWN THROUGH NORTHERN AND CENTRAL
LOWER MICHIGAN LATE MONDAY THROUGH THE FIRST PART OF MONDAY NIGHT.
FORECAST CONTINUES TO CARRY A LOW CHANCE OF POPS FROM I-69 NORTH
WHERE MORE MOISTURE WILL BE AVAILABLE AND WHERE COOLER MID-LEVEL AIR
WILL OVERLAP WITH DIURNAL HEATING AHEAD OF THE FRONT. THE SECONDARY
FRONT WILL REMAIN SETTLED OVER CENTRAL MICHIGAN INTO TUESDAY...AND
MAY AGAIN PROVIDE A FOCUS FOR SHOWERS AND A FEW THUNDERSTORMS
TUESDAY AFTERNOON/EVENING AS A SHORTWAVE TROUGH CLIPS ACROSS THE
REGION. CONDITIONS WILL FEEL COOLER WITH DEWPOINTS DROPPING INTO
MORE COMFORTABLE READINGS IN THE 50S...AND AS DAYTIME HIGHS ONLY
REACH INTO THE MID 70S TO LOW 80S MONDAY AND INTO THE 70S ON TUESDAY.

WEDNESDAY THROUGH SUNDAY.

FAIR WEATHER IS STILL ON TRACK FOR WEDNESDAY AS HIGH PRESSURE MOVES
OVER THE REGION. DRY CONDITIONS SHOULD HOLD OVER MOST OF SOUTHEAST
MICHIGAN ON THURSDAY MORNING...WITH EXCEPTION OF THE SOUTHERN MOST
COUNTIES WHERE SCATTERED SHOWERS WILL BEGIN TO POP. CHANCES OF
SHOWERS AND THUNDERSTORMS WILL SPREAD NORTHWARD THROUGH THE
AFTERNOON AND EVENING OFF LOW PUSHING INTO NORTHERN OHIO. CONFIDENCE
AND TIMING ON THIS SYSTEM IS LOW TO MODERATE DUE TO MODEL
INCONSISTENCIES. POTENTIAL FOR SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS WILL LINGER INTO SATURDAY.

&&

.MARINE...

STRONG SOUTHWEST WINDS WITH GUSTS OF 25 TO 30 KNOTS WILL CONTINUE
INTO TONIGHT IN ADVANCE OF A COLD FRONT DROPPING THROUGH THE GREAT
LAKES. THE STRONGEST WINDS WILL BE OVER SAGINAW BAY...WHERE
SOUTHWEST WINDS WILL FUNNEL. THE FRONT AND A WARM AND UNSTABLE
AIRMASS PRECEDING IT WILL ALSO PROVIDE ROUNDS OF SHOWERS AND
THUNDERSTORMS THROUGH TONIGHT...SOME OF WHICH WILL BE SEVERE. THE
MOST LIKELY THREAT WITH THUNDERSTORMS WILL BE WIND GUSTS TO 50
KNOTS. WINDS WILL TURN WEST AND THEN NORTHWEST BEHIND THE FRONT
MONDAY. WIND SPEEDS MONDAY LOOK TO BE GREATEST OVER NORTHERN LAKE
HURON...WHERE THEY WILL REACH BETWEEN 15 TO 25 KNOTS MONDAY NIGHT
THROUGH TUESDAY NIGHT AS COOLER AIR SETTLES OVER THE CENTRAL GREAT
LAKES REGION.

&&

.AVIATION...ISSUED 146 PM EDT SUN AUG 2 2015

THUNDERSTORMS TO THE NORTH SHOULD CONGEAL AND DROP SOUTH THROUGH
AREA THIS EVENING AS A COLD FRONT DROPS SOUTH THROUGH THE CENTRAL
GREAT LAKES. EXPECT A DECENT CHANCE OF A POCKETS OF SEVERE WEATHER
WITHIN THIS EXPECTED AREA OF THUNDERSTORMS...WHICH WILL MOST LIKELY
PROGRESS FROM MBS AT 00Z-01Z TO THE I-94 TERMINALS BY 03Z-05Z AND
THEN EXIT SOUTH OF WHOLE AREA AFTER 06-07Z. OTHERWISE THAN PATCHY
LATE NIGHT FOG TONIGHT...VFR CONDITIONS SHOULD...ONCE AGAIN...BE THE
RULE ONCE THE STORMY WEATHER ENDS TONIGHT.

FOR DTW...MOST PROBABLE TIME FOR TSTORMS WILL BE 03-06Z IN ADVANCE
OF APPROACHING COLD FRONT.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR TSTORMS THIS AFTN. MEDIUM AFTER 03Z TONIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT UNTIL 10 PM EDT THIS EVENING FOR MIZ049.

LAKE HURON...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR LHZ421-422-441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR LEZ444.

&&

SHORT TERM...DG
LONG TERM....HLO/DE
MARINE.......HLO
AVIATION.....DG

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

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