EF0 tornado, Stronach to High Bridge, Michigan, June 12, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
710 PM EDT THU JUN 12 2008

.AVIATION...SLOW MOVING COLD FRONT WILL BRING SHOWERS/THUNDERSTORMS
TO ALL TERMINALS OVERNIGHT.  MOST WIDESPREAD ACTIVITY EXPECTED TO
AFFECT KPLN/KTVC WHERE CIGS/VSBYS SHOULD OCCASIONALLY BE REDUCED
TO MVFR LEVELS...WITH POTENTIAL FOR LOCALLY HEAVY RAIN...WHILE
KAPN LOOKS TO AVOID PROLONGED PRECIP THRU MUCH OF THE NIGHT. LOW
LEVEL WIND SHEAR A CONCERN AT ALL TAF SITES AS 900MB JET CRANKS
OVERNIGHT UNDER STRONG WARM ADVECTION REGIME WHILE SFC WINDS
DIMINISH TO 12 KNOTS OR LESS. AREAS OF MVFR CIGS EARLY FRIDAY
MORNING WITH A FEW LIGHT SHOWERS...WITH VFR CONDITIONS DEVELOPING
AT ALL TERMINALS BY THE AFTERNOON.

JK
&&

.PREV DISCUSSION... /ISSUED 344 PM EDT THU JUN 12 2008/

DISCUSSION...SEASONABLY DEEP SURFACE LOW IN SOUTHERN MANITOBA.
OCCLUDED FRONT RUNS SE TO A WEAK TRIPLE POINT NORTH OF ROCHESTER MN.
COLD FRONT EXTENDS SOUTH FROM THERE TO EASTERN IOWA...THEN SW TO OK.
WARM FRONT IN CONVOLUTED THANKS TO ONGOING CONVECTION AND MARINE
INFLUENCES...BUT EXTENDS ESE TO NORTH OF CHICAGO...THE QUICKLY ZIGS
NORTHWARD TO NEAR THE M-55 CORRIDOR ACROSS CENTRAL LOWER MI. AS
EXPECTED...WARM ADVECTION-FORCED CONVECTION HAS REALLY GOTTEN
CRANKING OVER NORTHERN LAKE MI THIS AFTERNOON. PRECIP TRENDS...
INCLUDING THREAT FOR SVR WX AND HEAVY RAIN...ARE THE MAIN ISSUES FOR
TONIGHT.

TONIGHT...LOADING UP A RICH...JUICY AIRMASS IN NORTHERN IL THIS
AFTERNOON...WITH TEMPS PUSHING 90F AND DEW POINTS IN THE UPPER 60S.
MLCAPES AROUND 1500J/KG. LOW LEVEL SSW WINDS (30-40KT AT 850MB) ARE
DRAWING THIS AIRMASS NORTHWARD...WITH MUCAPES NEAR 1K J/KG ACROSS
LAKE MI AND INTO W CENTRAL LOWER MI. THIS ELEVATED INSTABILITY IS
FEEDING ONGOING VIGOROUS CONVECTION OVER NORTHERN LAKE MI.
INDIVIDUAL STORMS ARE LIFTING RAPIDLY NNE TOWARD PARTS OF EASTERN
UPPER MI...WHILE SLOWLY DEVELOPING EASTWARD WITH TIME. MEANWHILE...
STRONG CONVECTION CONTINUES TO DEVELOP SPORADICALLY ALONG WI/IL
BORDER.

ONGOING ACTIVITY OVER LAKE MICH COULD PULSE UP TO NEAR SVR FROM TIME
TO TIME...WITH A FAVORABLE OVERLAP OF MUCAPE AND SHEAR (0-6KM BULK
SHEAR 40-50KT). HOWEVER...OUR MAIN SVR THREAT WILL INVOLVE WHATEVER
GETS GOING BACK TOWARD CHICAGO. CONDITIONS WILL BE FAVORABLE FOR
CONVECTION TO BECOME WELL-ORGANIZED...LIFTING NE IN THE FORM OF BOWS
AND/OR LEWPY LINE SEGMENTS. BUT...AS MENTIONED EARLIER IN THE
DAY...WE NEVER QUITE REACH THE POINT WHERE WE HAVE SURFACE-BASED
INSTABILITY. DEW POINTS WILL CLIMB INTO THE MID 60S BY EVENING...BUT
BY THEN TEMPS WILL BE FALLING BACK THRU THE 70S. THUS WINDS WILL
HAVE SOME WORK TO DO TO GET TO THE GROUND...BUT THAT SHOULD BE VERY
DOABLE. THUS STRAIGHT-LINE WINDS ARE THE MAIN THREAT.

INDIVIDUAL STORMS WILL BE MOVING RAPIDLY TO THE NE AT 40KT. SOME
LOCALIZED HEAVY RAIN WILL OCCUR...THANKS TO BACKBUILDING ON THE SW
FLANK OF INDIVIDUAL STORMS. WIDESPREAD HEAVY RAIN IS NOT
ANTICIPATED.

MIN TEMPS MID 50S NORTH TO NEAR 70 SOUTH.

JZ

REST OF THE FORECAST (FRIDAY THROUGH NEXT THURSDAY)...THE LONG WAVE
TROUGH EVIDENT ON WATER VAPOR LOOP CENTERED TO OUR WEST ACROSS THE
GREAT BASIN WILL MEANDER TO THE EAST AND STALL ACROSS EAST CENTRAL
CANADA LATER THIS WEEKEND THEN REVERSE COURSE AND HEAD SOUTHEAST EARLY
NEXT WEEK. RIDGING MAY THEN TRY TO BUILD INTO THE REGION TOWARD
THE END OF THE FORECAST PERIOD. THIS IS EXPECTED TO LEAD TO
CONTINUED SHOWERY CONDITIONS AT TIMES OVER THE NEXT FEW DAYS AS
WELL AS NORMAL TO SLIGHTLY BELOW NORMAL TEMPERATURES...ESPECIALLY
FOR THE EARLY AND MIDDLE PARTS OF NEXT WEEK. THE MAIN FORECAST
CONCERNS REVOLVE AROUND POPS THROUGH A MAJORITY OF THE FORECAST.

FRIDAY...SURFACE LOW MOVES NORTH NORTHEAST INTO NORTHEAST ONTARIO.
THE COLD FRONT OCCLUDES AND DOES NOT APPEAR THAT IT IS EVER QUITE
ABLE TO MOVE THROUGH AS THE EASTERN RIDGE HOLDS UP ITS PROGRESS AND
A WAVE OF LOW PRESSURE MOVES UP ALONG THE FRONT (ALONG WITH
ASSOCIATED DIV-Q). MODELS ALSO LINGER THETA-E RIDGE ACROSS THE
REGION SO WILL CONTINUE WITH CATEGORICAL POPS ACROSS THE
EAST...LIKELY POPS CENTRAL AND CHANCE POPS ACROSS THE WEST.
POTENTIAL FOR SEVERE APPEARS TO BE LIMITED...DUE TO THE LACK OF
SURFACE HEATING. BEST CHANCE FOR SEVERE STORMS TO OUR SOUTHEAST BUT
ANY AFTERNOON CLEARING WOULD ALLOW FOR STORMS TO TAP INTO 30-35 KT
850 MB WIND AND AROUND 50 KNOT 500 MB WINDS. HIGHS WILL BE TRICKY
WITH THE MILD START OFFSET BY EXPECTED ABUNDANT CLOUD COVER. WILL
KEEP HIGHS IN THE 70S BUT SOME LOWER 80S POSSIBLE IF CLOUDS DO END
UP SCATTERING OUT.

FRIDAY NIGHT...MID LEVEL DRY SLOT MOVES INTO THE REGION AS STORM
SYSTEM PINWHEELS TO THE NORTH ACROSS WESTERN ONTARIO.
THEREFORE...WITH THE EXCEPTION OF POSSIBLE LINGERING SHOWERS/STORMS
ACROSS THE SOUTHEAST IN THE EVENING PRECIPITATION FREE CONDITIONS ARE
EXPECTED. LOWS RANGING FROM THE LOWER 50S NORTHWEST TO THE UPPER 50S
SOUTHEAST.

SATURDAY...A BIT OF WRAP AROUND MOISTURE ROTATES SOUTHEAST AS UPPER
TROUGH TAKES UP RESIDENCE ACROSS NORTHERN ONTARIO. THIS IN
COMBINATION WITH DAYTIME HEATING MAY SPARK A MAINLY AFTERNOON SHOWER
OR STORM. HIGHS IN THE 70S.

SATURDAY NIGHT...NEARLY ZONAL FLOW ALOFT OPENS THE POSSIBILITY OF
MCS DEVELOPMENT UPSTREAM SO WILL EXPAND CHANCE POPS EASTWARD.

SUNDAY...LINGERING MOISTURE ALONG WITH AN APPROACHING SURFACE COLD
FRONT WILL LEAD TO MORE CHANCE POPS. HIGHS AGAIN EXPECTED TO BE IN
THE 70S.

MONDAY THROUGH THURSDAY...UPPER LEVEL TROUGH REVERSES COURSE AND
HEADS SOUTHEAST TOWARD THE WESTERN GREAT LAKES REGION LIKELY LEADING
TO COOLER TEMPERATURES ALONG WITH THE CHANCES FOR SHOWERS FOR AT
LEAST MONDAY. NATIONAL GUIDANCE HAS TUESDAY DRY...BUT 12Z ECMWF AND
OTHER EXTENDED MODELS WOULD LINGER CHANCES RIGHT INTO TUESDAY AS
WELL (BUT WILL NOT ADD IN POPS AT THIS TIME). INCREASING
RIDGING/RISING HEIGHTS EXPECTED TO LEAD TO WARMER CONDITIONS BY THE
END OF THE WEEK. HIGHS ONLY IN THE MIDDLE 60S TO LOWER 70S MONDAY
THROUGH WEDNESDAY THEN BACK INTO THE 70S THURSDAY.

SULLIVAN

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LMZ341.

LH...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LHZ346>349.

LS...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LSZ321-322.

&&

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