Severe Thunderstorm Warning 57, NWS Gaylord, MI

000 
WWUS34 KAPX 220615
SVSAPX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE GAYLORD MI
215 AM EDT SAT SEP 22 2007

MIC031-141-220625-
/O.EXP.KAPX.SV.W.0057.000000T0000Z-070922T0615Z/
CHEBOYGAN MI-PRESQUE ISLE MI-
215 AM EDT SAT SEP 22 2007

...THE SEVERE THUNDERSTORM WARNING FOR PRESQUE ISLE AND CHEBOYGAN
COUNTIES HAS EXPIRED...

AT 213 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED THAT
THE STORM WHICH PROMPTED THE SEVERE THUNDERSTORM HAD WEAKENED 
SOMEWHAT...AND WAS MOVING OUT OVER LAKE HURON. THE WARNING HAS 
THEREFORE BEEN ALLOWED TO EXPIRE.

AT AROUND 145 AM...THIS STORM CONTRIBUTED TO DOWNED POWER LINES IN 
THE INDIAN RIVER AREA.

LAT...LON 4524 8447 4555 8461 4567 8428 4560 8413
      4556 8410 4551 8409 4551 8395 4539 8370
TIME...MOT...LOC 0613Z 248DEG 55KT 4558 8393

$$


JZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
116 AM EDT SAT SEP 22 2007

.AVIATION...STRONG COLD FRONT CURRENTLY SLIDING ACROSS NORTHERN
MICHIGAN WILL DRIVE A BAND OF SHOWERS...AND PERHAPS AN ISOLATED
THUNDERSTORM...THROUGH THE AREA UNTIL ABOUT 10Z THIS MORNING. MAINLY
VFR CONDITIONS EXPECTED...THOUGH COULD SEE A BRIEF MVFR CEILING WITH
SOME OF THE SHOWERS. OTHERWISE...THE BIG STORY WILL BE THE
CONTINUATION OF GUSTY WINDS...INITIALLY FROM THE SOUTHWEST BUT
QUICKLY SHIFTING WEST EARLY THIS MORNING WITH THE FRONTAL PASSAGE.
RATHER TIGHT GRADIENT LOOKS TO REMAIN IN PLACE THROUGH THE AFTERNOON
HOURS...WITH GOOD MIXING OF RESIDUAL STRONG FLOW ALOFT...SO EXPECT
SUSTAINED WINDS IN THE 12 TO 20KT RANGE...WITH OCCASIONAL GUSTS UP
TO 30 KNOTS...PARTICULARLY THROUGH ABOUT 18Z. WITH VERY DRY AIR
MOVING INTO THE REGION...SHOULD SEE MAINLY CLOUD-FREE CONDITIONS AS
WELL...THOUGH A FEW AFTERNOON CU NOT OUT OF THE QUESTION. HIGH
PRESSURE WILL ARRIVE BY LATE EVENING...WITH WINDS QUICKLY
DIMINISHING TO UNDER 8 KNOTS AND SKIES REMAINING CLEAR.

LAWRENCE

&&

.UPDATE...ISSUED 1222 AM SAT SEP 22...

A SERIES OF UPDATES TO GET RID OF SVR TSTORM WATCH...AS ACTIVITY HAS
BEEN TREMENDOUSLY INSTABILITY-STARVED DESPITE IMPRESSIVE DYNAMICS.
STILL NOT OUT OF THE QUESTION TO SEE A HIGH GUST OR TWO...BUT MORE
LIKELY ALONG THE FRONT WHERE HAVE SEEN A FEW GUSTS TO 40 KNOTS
UPSTREAM (SEE PREVIOUS DISCUSSION FOR ADDITIONAL INFO REGARDING
THINKING BEHIND THIS). NO OTHER CHANGES MADE FOR TONIGHT...OTHER
THAN TO REALIGN POP GRIDS FOR BETTER TIMING...AS EXPECT WIDE AREA OF
SHOWERS TO PROGRESS ACROSS THE CWA OVERNIGHT AS BEST FORCING SLIDES
OVER THE NORTHERN LAKES.

LAWRENCE

&&

.PREV DISCUSSION.../ISSUED 1008 PM EDT FRI SEP 21 2007/

UPDATE...UPSTREAM CONVECTIVE EVENT UNFOLDING PRETTY MUCH AS
ANTICIPATED BY EARLIER FORECAST SHIFTS...AND ONLY A FEW CHANGES MADE
FOR THE EVENING PACKAGE UPDATE. STRONG SHORTWAVE PROGRESSING THROUGH
THE UPPER MIDWEST (500MB HEIGHT FALLS ON THE ORDER OF 100DM IN
ADDITION TO INCREASINGLY NEGATIVE TILT TO THE SYSTEM) CONTINUES TO
FORCE A WELL-DEFINED LINE OF MAINLY PRE-FRONTAL CONVECTION...WITH A
SMALL SECONDARY AREA ALONG THE IMMEDIATE FRONTAL BOUNDARY.
TREMENDOUS LOW/MID LEVEL WIND FIELDS...WITH 0-6KM BULK SHEAR ON THE
ORDER OF 50+ KNOTS HAS NOT SURPRISINGLY RESULTED IN QUITE A FEW
REPORTS OF DAMAGING WINDS UPSTREAM...AND THE POTENTIAL FOR SEVERE
WEATHER REMAINS THE PRIMARY FORECAST CHALLENGE TONIGHT.

AMBIENT ENVIRONMENT ACROSS MUCH OF NORTHERN MICHIGAN NOT OVERLY
SUPPORTIVE FOR CONVECTION PER 00Z APX RAOB SHOWING PLENTIFUL CAPPING
STILL INTACT...WITH RATHER UNIMPRESSIVE MOISTURE PROFILE AS WELL
(PWAT ONLY ABOUT AN INCH). HOWEVER...STRONG FORCED ASCENT IN ADVANCE
OF THE APPROACHING SHORTWAVE COUPLED WITH PRONOUNCED LOW LEVEL
CONVERGENCE ALONG THE FRONT AND NARROW RIBBON OF MOISTURE/DECREASED
STABILITY SLIDING INTO THE REGION SHOULD PROVIDE A MECHANISM TO
DRIVE CONVECTION EASTWARD OVER THE NEW FEW HOURS. IN TYPICAL
FASHION...APPEARS GREATEST THREAT FOR CONVECTION WILL BE FOUND OVER
MAINLY THE WESTERN HALF OF THE CWA WHERE DECREASED STABILITY OVER
THE LAKE (EVIDENCED BY RECENT ADDITIONAL CONVECTIVE DEVELOPMENT OVER
THE WATER) LIKELY TO COME INTO PLAY ALONG WITH GREATER DYNAMIC
FORCING/MOISTURE CHANNELING BEFORE BEST SUPPORT SHEARS OUT INTO
EASTERN ONTARIO. GIVEN SUCH STRONG WIND FIELDS (925-850MB WINDS ON
THE ORDER OF 45 TO 50 KNOTS)...CERTAINLY ANY ORGANIZED CONVECTION
WILL BE EASILY CAPABLE OF PRODUCING DAMAGING WIND GUSTS...AND THIS
WILL BE COVERED BY NEWLY ISSUED SVR TSTORM WATCH BASICALLY
ALONG/NORTH OF M-32.

IN ADDITION TO THE SEVERE THREAT...STILL APPEARS A BRIEF PERIOD OF
STRONGER SYNOPTIC WINDS MAY BE IN STORE FOR MUCH OF THE CWA AS WELL
ALONG AND JUST BEHIND THE PASSAGE OF THE FRONT. TIGHTENING GRADIENT
IN THE WAKE OF THE FRONT COUPLED WITH QUICK PUSH OF DEEP
SUBSIDENCE/DOWNWARD MOMENTUM TRANSFER AND AMBIENT VERY STRONG WIND
FIELDS ALOFT INDICATE THE POTENTIAL FOR A 1 OR 2 HOUR PERIOD OF
STRONGER GUSTS TO AROUND 45 KNOTS IMMEDIATELY BEHIND THE FRONT AS
STRONG COLD ADVECTION GETS UNDERWAY. THIS POTENTIAL ALSO SHOWN VIA
PV TIME HEIGHTS WITH GOOD LINKAGE ALOFT INDICATIVE OF SHARP TROP
FOLD EVENT WITH DEEP SUBSIDENCE IN THE WAKE OF THE FRONT. GIVEN
ALREADY GUSTY ENVIRONMENT ALONG WITH POTENTIAL FOR STRONG WINDS WITH
ANY CONVECTION...PREFER TO NOT MENTION ANY ADDITIONAL PRODUCTS TO
ADDRESS THE WIND...AS PERIOD OF BEST POTENTIAL WILL BE LIMITED TO A
NARROW WINDOW JUST BEHIND THE FRONT.

TEMPERATURES THIS EVENING SHOULD REALLY GO NOWHERE WITH STROUT
SOUTHWEST FLOW AHEAD OF THE FRONT...AND WILL TREND NUMBERS TO SHOW A
MORE STEADY TREND. HOWEVER...STRONG COLD ADVECTION TAKING SHAPE FROM
WEST TO EAST LATE TONIGHT WILL KNOCK TEMPS DOWNWARD FAIRLY QUICKLY
TOWARD 10Z OR SO...WITH LOWS IN THE MID-UPPER 50S APPEARING ON
TRACK.

LAWRENCE

&&

.APX WATCHES/WARNINGS/ADVISORIES...
     GALE WARNING...THROUGH 12Z SATURDAY...
       LSZ321-322-LMZ323-341-342-344-345-LHZ345.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GAYLORD MI
1225 AM EDT SAT SEP 22 2007

LHZ345>349-361-362-LMZ323-341-342-344-345-363-LSZ321-322-MIZ008-
015>036-041-042-221000-
STRAITS OF MACKINAC-ST IGNACE TO FALSE DETOUR CHANNEL-
MACKINAC BRDG TO PRESQUE ISLE LT-PRESQUE ISLE LT TO STURGEON PT-
STURGEON PT TO ALABASTER-MICHIGAN WATERS OF NORTHERN LAKE HURON-
MICHIGAN WATERS OF CENTRAL LAKE HURON-GRAND TRAVERSE BAY-
SEUL CHOIX PT TO MACKINAC BRDG-NORWOOD TO MACKINAC BRDG-
SLEEPING BEAR PT TO GRAND TRAVERSE LT-MANISTEE TO SLEEPING BEAR PT-
MICHIGAN WATERS OF NORTHERN LAKE MICHIGAN-WHITEFISH BAY-
ST. MARYS RIVER-CHIPPEWA-MACKINAC-EMMET-CHEBOYGAN-PRESQUE ISLE-
CHARLEVOIX-LEELANAU-ANTRIM-OTSEGO-MONTMORENCY-ALPENA-BENZIE-
GRAND TRAVERSE-KALKASKA-CRAWFORD-OSCODA-ALCONA-MANISTEE-WEXFORD-
MISSAUKEE-ROSCOMMON-OGEMAW-IOSCO-GLADWIN-ARENAC-
1225 AM EDT SAT SEP 22 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE HURON...LAKE
MICHIGAN...LAKE SUPERIOR...EASTERN UPPER MICHIGAN AND NORTHERN LOWER
MICHIGAN.

.DAY ONE...TONIGHT

AN ISOLATED THUNDERSTORM IS POSSIBLE TONIGHT. SEVERE THUNDERSTORMS
ARE NO LONGER EXPECTED.

A STRONG COLD FRONT MOVING ACROSS THE AREA TONIGHT WILL BRING A FEW
HOURS OF GUSTY WINDS TO NORTHERN MICHIGAN OVERNIGHT. OCCASIONAL WIND
GUSTS OF 40 TO 50 MPH WILL BE POSSIBLE BETWEEN 1 AM AND 5 AM AS THE
FRONT QUICKLY MOVES THROUGH THE AREA.

IN ADDITION...GALE FORCE WINDS WILL BE PRESENT ON THE NEARSHORE AND
OPEN WATERS OF LAKES MICHIGAN AND SUPERIOR TONIGHT. A FEW GALE FORCE
GUSTS ARE ALSO EXPECTED ON LAKE HURON LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT INTO TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED TONIGHT...HOWEVER SPOTTERS ARE
ENCOURAGED TO REPORT WIND GUSTS...EITHER OVER LAND OR ON THE WATER.

LAWRENCE