Severe Thunderstorm Warning 15, NWS Gaylord, MI

AREA FORECAST DISCUSSION...CORECTED
NATIONAL WEATHER SERVICE GAYLORD MI
350 PM EDT THU JUL 3 2003

ADDED MENTION OF HEAVY RAIN FRIDAY PM

BAND OF MOISTURE/INSTABILITY AS PUSHING THROUGH THE FORECAST AREA
THIS AFTERNOON...WITH WIDESPREAD CONVECTION ACROSS THE NORTH.

FORECAST CONCERN IN SHORT TERM IS CONVECTIVE TRENDS THIS
EVENING/OVERNIGHT. THEN...ATTENTION TURNS TO SIGNIFICANT SEVERE
POTENTIAL ON THE 4TH.

WIDESPREAD PRECIP WILL PUSH E OF NORTHERN COUNTIES BY 6 PM.
HOWEVER...LAKE BREEZE CONVERGENCE ACROSS THE EASTERN UP AND
CONVERGENCE PROVIDED BY THUNDERSTORMS OUTFLOW WILL JUSTIFY LINGERING
CHANCE POPS THROUGH THIS EVENING. THEN...12Z ETA DEPICTS AXIS OF LOW
LEVEL DRYING AND Q VECTOR DIVERGENCE ADVANCING INTO THE FORECAST
AREA FOR THE OVERNIGHT...SO THERE WILL LIKELY BE NO PRECIP AFTER
MIDNIGHT.

POTENTIAL EXISTS FOR AN ACTIVE SEVERE WEATHER DAY ON THE
4TH...ESPECIALLY DURING THE AFTERNOON/EVENING HOURS.
AT 12Z...THUNDERSTORM COMPLEX MAY BE ONGOING OVER LAKE
SUPERIOR...WHERE BAND OF 850 MB WINDS 20-25 KTS WILL CONTRIBUTE TO
LOW LEVEL CONVERGENCE WITHIN DEVELOPING THETA E RIDGE/SW TO NE BAND
OF 850 MB DEWPOINTS +10C TO +12C...WITH ASCENT AIDED BY 850-500 QG
FORCING. INITIALLY...THIS ACTIVITY SHOULD BE AT WORST MARGINALLY
SEVERE UPSTREAM AND SHOULD EVEN BE IN A WEAKENING MODE AS IT
PROPAGATES E/ESE INTO RELATIVELY DRY (900-700 MB MEAN RH AROUND
35%)/STABLE (ELEVATED CAPES STRUGGLING TO REACH 100 J/KG AND 0-6 KM
BULK SHEAR AROUND 30 KTS. HOWEVER...DESTABILIZATION WILL RESULT IN
CAPES 1500-2000 J/KG (MID 80S TEMPS/MID 60S DEWPTS) BY EARLY
AFTERNOON...WHILE 0-6 KM BULK SHEAR IS FORECAST TO INCREASE TO
GREATER THAN 50 KTS (UNTIL 0Z) WITHIN AXIS OF 850-500 MB QG
FORCING...WITH ASCENT ENHANCED BY UPPER DIVERGENCE THAT WILL SPREAD
ACROSS THE REGION IN RIGHT REAR OF 120 KT JET MAX. THUS...CONDITIONS
WILL BECOME FAVORABLE FOR THUNDERSTORMS TO DEVELOP AND BECOME
ORGANIZED ACROSS THE NORTH FRIDAY AFTERNOON...WITH BULK SHEAR
MAGNITUDE MORE THAN SUFFICIENT FOR SUPERCELLS PRODUCING DAMAGING
MICROBURSTS AND EVEN ISOLATED LARGE HAIL.

MEANWHILE...POTENTIAL FOR SIGNIFICANT SEVERE EVENT EXISTS
FRIDAY AFTERNOON/EVENING...ESPECIALLY ACROSS CENTRAL/S COUNTIES OF
NORTHERN LOWER MI...AS A SEVERE MCS WILL DEVELOP WEST OF THE
FORECAST AREA...ALONG EDGE OF CAP (700 MB TEMPS +11C TO +12Z ACROSS
THE SOUTHERN LAKES)...WHERE 30-35 KT LOW LEVEL JET WILL DEVELOP
WITHIN REGION OF AT LEAST 40-50 KT 0-6 KM BULK SHEAR...850-500 MB QG
FORCING/300-250 MB DIVERGENCE...AND COMPLEX WILL PUSH EAST INTO AT
LEAST SOUTHERN 1/2 OF FORECAST AREA FRIDAY AFTERNOON/EVENING...WHERE
CAPES WILL HAVE INCREASED TO AROUND 3000 J/KG. WIND DAMAGE POTENTIAL
WILL BE ENHANCED BY RIBBON OF 50-65 KT WINDS IN THE 700-500 MB
LAYER.

UNCLEAR WHETHER NORTHERN CONVECTION AND SOUTHERN CONVECTION WILL
REMAIN SEPARATE FEATURES OR WILL MERGE INTO ONE COMPLEX. AT ANY
RATE...AT LEAST LIKELY POPS ARE IN ORDER FOR ALL AREAS FRIDAY INTO
FRIDAY EVENING.

WITH AXIS OF PWATS AROUND 2 INCHES PUSHING INTO REGION...HEAVY RAIN
IS POSSIBLE FRIDAY AFTERNOON/EVENING.

MAY BE PATCHY FOG FRIDAY NIGHT. THEN...WILL CONTINUE DRY FORECAST
SATURDAY...ALTHOUGH I AM CONCERNED THAT A FEW THUNDERSTORMS MAY POPS
UP WHERE LAKE BREEZE CONVERGENCE BECOMES A FACTOR ACROSS THE E/SE IN
THE AFTERNOON/EVE...BUT GIVEN MORE PRESSING ISSUES ADDITION OF
ISOLATED THUNDERSTORMS ARE BEST SAVED FOR LATER ISSUANCES.

BY SUNDAY...12Z MODELS DEPICT ANOTHER SHORTWAVE/WEAK SURFACE
BOUNDARY EMBEDDED IN FAST WNW FLOW REGIME PUSHING INTO THE
REGION...PERHAPS PRODUCING ANOTHER ROUND OF THUNDERSTORMS. TIMING
AND LOCATION OF POPS IS HIGHLY UNCERTAIN AT THIS POINT...BUT AREA
COLLABORATION SUGGESTS CHANCE POPS ARE IN ORDER SUNDAY ACROSS N/W
COUNTIES.

A FAIRLY STRONG SHORTWAVE/COLD FRONT (WITH SEVERE POTENTIAL) SHOULD
PUSH THROUGH THE REGION MONDAY...THEN 0Z GFS/CANADIAN/UKMET
OPERATIONAL MODELS (AND MANUAL GUIDANCE) NOW POINT TOWARD A
PROGRESSIVE SCENARIO...WITH SURFACE HIGH PRESSURE BUILDING INTO THE
REGION BY TUESDAY AND REMAINING OVER REGION THROUGH
WEDNESDAY...PROVIDING DRY CONDITIONS. SINCE 12Z GFS DEPICTS A LESS
PROGRESSIVE SCENARIO...THERE REMAINS UNCERTAINTY ABOUT TIMING...AND
LATER ADJUSTMENTS MAY BE NEEDED. THEN...NEXT ROUND OF CONVECTION
(PERHAPS IN MCS MODE) WILL TRAVERSE PERIPHERY OF UPPER RIDGE AND MAY
DROP INTO THE REGION IN NW FLOW REGIME THURSDAY...JUSTIFYING CHANCE
POPS.

.APX...NONE.

ROWLEY

MIZ008-015>036-041-042-041100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GAYLORD MI
540 PM EDT THU JUL 3 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHERN LOWER AND EASTERN
UPPER MICHIGAN.

.DAY ONE...TONIGHT

ISOLATED THUNDERSTORMS MAY PRODUCE DAMAGING WIND GUSTS TO 60 MPH
ACROSS NORTHERN MICHIGAN UNTIL MIDNIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH THURSDAY

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
LOWER MICHIGAN...AND A SLIGHT RISK FOR SEVERE THUNDERSTORMS ACROSS
EASTERN UPPER MICHIGAN...ON INDEPENDENCE DAY. THE GREATEST THREAT
FOR SEVERE WEATHER WILL EXIST DURING THE AFTERNOON AND EVENING
HOURS. WIDESPREAD DAMAGING WIND GUSTS EXCEEDING 60 MPH WILL BE THE
PRIMARY SEVERE THREAT...ESPECIALLY ACROSS NORTHERN LOWER
MICHIGAN...BUT ISOLATED THUNDERSTORMS MAY ALSO PRODUCE HAIL
EXCEEDING ONE INCH IN DIAMETER ANYWHERE ACROSS NORTHERN MICHIGAN.

THUNDERSTORMS ARE POSSIBLE ACROSS PARTS OF NORTHERN MICHIGAN
SUNDAY...ACROSS NORTHERN MICHIGAN MONDAY AND AGAIN ON THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED FRIDAY...ESPECIALLY DURING THE
AFTERNOON AND EVENING HOURS. DISPATCHERS...PLEASE NOTIFY YOUR
EMERGENCY MANAGERS IMMEDIATELY.

&&

MORE INFORMATION MAY BE OBTAINED AT THE FOLLOWING URL:
HTTP://WWW.CRH.NOAA.GOV/APX (ALL LOWER CASE)

ROWLEY