Hail and Damaging Winds in Michigan, July 26, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
358 PM EDT THU JUL 26 2007

.SHORT TERM...THIS AFTERNOON AND TONIGHT

THE UPPER LEVEL LOW OVER SAGINAW BAY CONTINUES TO SPIRAL NORTH AND
WEST RESULTING IN A WESTERLY STEERING FLOW FOR LOWER PENINSULA.
CONVECTION THIS AFTERNOON HAS REMAINED MILD WITH MORNING CLOUD DECK
TEMPERING THE THE FRUITION OF INSTABILITY. IN ADDITION...SHALLOW
NATURE OF BOUNDARY LAYER MOISTURE ALLOWED FOR ENOUGH MIXING TO KEEP
MLCAPES OF ONLY 500-800 J/KG. THE WIND FIELD WILL REMAIN WEAK
THROUGH THE FIRST HALF OF TONIGHT WITH THE COLUMN NIL UNDER THE
VORTEX. THEREFORE...SLOW PROPAGATION OF CELLS WILL KEEP HEAVY
RAINFALL THE BIGGEST CONCERN.

LATER TONIGHT...ATTENTION TURNS TO THE POTENTIAL FOR WIDESPREAD
RAINFALL. THE STRONGER KICKING WAVE CURRENTLY OVER NORTHERN
MINNESOTA...WILL DEVELOP A MCS (CURRENTLY UNDERWAY) AND DRIVE IT
SOUTHEAST TOWARDS THE FORECASTING AREA. HEIGHT FALLS IN ADVANCE OF
THE WAVE COMBINED WITH NOCTURNAL COOLING OF BOUNDARY LAYER WILL
DEVELOP A ZONAL LOW LEVEL JET (OF AT LEAST 35 KNOTS) INTO WESTERN
PORTIONS OF LOWER MICHIGAN. MOISTURE TRANSPORT WILL BE HIGHLY
EFFICIENT SINCE 850MB DEWPOINTS OF UP TO 14C WILL BE DRIVEN INTO THE
FORECAST AREA ON THE NOSE OF THE LLJ. THIS ADDED MOISTURE AT THE TOP
OF THE BOUNDARY LAYER WILL GIVE ELEVATED INSTABILITY AS SEEN WITH
SHOWALTERS VALUES APPROACHING -3 C.  SO EXPECTING CONVECTION TO FIRE
ON THE NOSE OF THE LLJ (ARRIVING IN LOWER MICHIGAN 6Z-8Z TIMEFRAME)
WELL IN ADVANCE OF THE MAIN MCS LAGGING TO THE WEST. THERE HAS BEEN
UNCERTAINTY IN THE MODEL SOLUTIONS IN REGARDS TO THE LOCATION OF THE
HEAVIER PRECIPITATION...BUT WITH THE RELATIVELY LIMITED DAYTIME
HEATING AND LOCATION OF THE LLJ FEEL THE SOUTHERN PORTIONS OF THE
STATE...MAINLY SOUTH OF A LINE FROM SAGINAW TO PORT HURON...STAND
THE BEST CHANCE TO SEE THE DEVELOPMENT PRIOR TO 12Z. SUPPORT FOR
PRECIPITATION LOOKS IMPRESSIVE WITH AMOUNT OF MODEL 850-500MB UVVS
AND STRONG ISENTROPIC LIFT. MAIN CONCERN TONIGHT WILL...YOU GUESSED
IT...AGAIN BE HEAVY RAINFALL AS PWATS CLIMB TO 1.50 INCHES. SHEAR
WILL INEVITABLY INCREASE TONIGHT WITH THE ARRIVAL OF THE LLJ BUT
LIMITED INSTABILITY LIMITS MUCH OF A SEVERE THREAT.  FREEZING
HEIGHTS BEGIN CLIMBING AS WELL WITH THE WAA TO AROUND 12/13 KFT.

TEMPERATURES TONIGHT WILL BE A LITTLE MORE MILD DROPPING INTO THE
MID 60S WITH ABUNDANT CLOUD COVER AND TROPOSPHERIC WAA.

&&

.LONG TERM...FRIDAY THROUGH THURSDAY

A PROGRESSIVE NORTHERN STREAM TROUGH...CURRENTLY MOVING INTO
NORTHERN ONTARIO HAS AN ASSOCIATED FRONTAL BOUNDARY STRETCHING
ACROSS MINNESOTA AND INTO THE CENTRAL PLAINS. THE 12Z MODEL SUITE
FORECAST THE NORTHERN STREAM TROUGH TO LIFT INTO NORTHERN QUEBEC ON
FRIDAY...ALLOWING THE UPPER LOW CURRENTLY NORTH OF THE THUMB TO
QUICKLY BE LIFTED OFF TO THE NORTHEAST. A MID LEVEL SHORT
WAVE...CURRENTLY OVER MINNESOTA...IS FORECAST TO MOVE SOUTHEAST FROM
NORTHERN IL THROUGH INDIANA ON FRIDAY. EXPECT THE STRONGEST
CONVECTION WILL BE TIED TO THIS FEATURE GIVEN THE BETTER INFLOW AND
LOW LEVEL INSTABILITY IN THIS REGION. THE 12Z MODEL SUITE SHOW SOME
SEMBLANCE OF A SURFACE LOW ASSOCIATED WITH THIS FEATURE TRACKING
INTO INDIANA...WITH THE SURFACE BOUNDARY MOVING INTO SE MI DURING
THE AFTERNOON. UPPER LEVEL DIFFLUENT FLOW ALONG WITH BOUNDARY LAYER
CONVERGENCE WILL PROVIDE A FOCUS FOR CONVECTION. UPSTREAM RAOBS
SUPPORT CURRENT MODEL PROJECTIONS WHICH SHOW PRECIPITABLE WATER
VALUES INCREASING TO AROUND 1.8 INCHES BY FRI AFTERNOON. AT THIS
POINT...IT APPEARS CLOUD COVER AND POTENTIAL EARLY MORNING
CONVECTION WILL KEEP INSTABILITY DOWN. SO NOT EXPECTING MUCH SEVERE
WEATHER AT THIS POINT. GIVEN THE DEGREE OF MOISTURE...WILL HOWEVER
MAINTAIN THE CURRENT MENTION OF HEAVY RAIN.

THE GFS CONTINUES TO SHOW MORE AMPLIFICATION IN THE WAVE MOVING INTO
THE UPPER OHIO VALLEY FRI NIGHT INTO SATURDAY...THUS MAINTAINING
MORE LOW LEVEL CYCLONIC FLOW AND INSTABILITY OVER THE SOUTHERN
PORTIONS OF THE FORECAST AREA INTO SATURDAY. WITH SUPPORT OF THE 12Z
CANADIAN AND UKMET...WILL LEAN TOWARD THE GFS SOLUTION. THIS
WARRANTS MAINTAINING THE LOW CHANCE POPS INTO THE SOUTHERN PORTIONS
OF THE FORECAST AREA INTO SATURDAY BEFORE SURFACE HIGH PRESSURE
SETTLES INTO THE AREA FROM THE NORTH BY THE END OF THE WEEKEND.

THE MEDIUM RANGE MODEL SUITE CONTINUE TO SHOW SURFACE HIGH PRESSURE
REMAINING OVER THE GREAT LAKES THROUGH MID WEEK. MODELS HAVE TRENDED
A LITTLE STRONGER WITH THE EASTERN NORTH AMERICAN TROUGH NEXT
WEEK...BUT MAINTAIN NORTHWEST FLOW ALOFT ACROSS MI WITH THE UPPER
RIDGE STILL FORECAST TO BUILD INTO THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. THE GFS SOLUTION SHOWS A BACK DOOR COLD FRONT
TRYING TO SINK SOUTH ACROSS THE STATE MONDAY AND MONDAY NIGHT. THERE
ALSO APPEARS TO BE SOME POTENTIAL FOR SHORT WAVE ENERGY TO DROP DOWN
FROM NORTHERN ONTARIO OVER THE PERIPHERY OF THE RIDGE AXIS. THE
MEDIUM RANGE MODEL SUITE INDICATES LIMITED MOISTURE OVER THE
REGION...WITH THE GULF MOISTURE SUPPLY CUT OFF. SO WILL MAINTAIN A
DRY FORECAST MON THROUGH WED WITH TEMPERATURES WARMING TO ABOVE
NORMAL BY MID WEEK. THE DEEP UPPER LOW CURRENTLY OFF THE COAST OF
BRITISH COLUMBIA IS FORECAST TO MOVE ACROSS CENTRAL CANADA NEXT
WEEK. THERE IS ACTUALLY GOOD AGREEMENT AMONG THE GFS...CANADIAN AND
ECMWF IN SHOWING AN ASSOCIATED SURFACE FRONT DROPPING INTO THE
NORTHERN GREAT LAKES REGION ON THURSDAY. WITH RIDGING EXPECTED TO
HOLD ACROSS THE OHIO VALLEY AND LIMITED MOISTURE ALONG THE
FRONT...WILL HOLD OFF ON PUTTING POPS INTO THE THURSDAY PERIOD AT
THIS TIME.

&&

.MARINE...

A FRONTAL BOUNDARY WILL SLOWLY SETTLE INTO THE REGION ON FRIDAY.
THERE IS A CHANCE OF THUNDERSTORMS TONIGHT THROUGH THE DAY ON FRIDAY
ASSOCIATED WITH THIS FEATURE. THE FRONT WILL GRADUALLY SETTLE SOUTH
OF THE AREA BY SATURDAY MORNING. THE GRADIENT WILL BE FAIRLY WEAK
ALONG THE FRONT. WITH AMPLE LOW LEVEL MOISTURE ALONG THE
BOUNDARY...THERE IS A POTENTIAL FOR FOG ON THE LAKES LATE FRIDAY
AFTERNOON THROUGH EARLY SATURDAY MORNING BEFORE NORTH-NORTHEASTERLY
WINDS INCREASE TO 15 TO 20 KNOTS BY LATE SATURDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 146 PM EDT THU JUL 26 2007

AVIATION...

SAME TALE WITH PERSISTENT UPPER LEVEL LOW NOW CENTERED OVER THE
THUMB. THUNDERSTORM CHANCES ARE REFLECTED IN THE TAFS WITH TEMPO
GROUP THIS AFTERNOON...TIED TO THE DIURNAL PEAK IN INSTABILITY.
ADDITIONALLY...LATEST SPC MESOANALYSIS SHOWS CONVECTIVE INHIBITION
TO BE REACHED SHORTLY WITH LCL-LFC NEAR SATURATION. THE BIG
CONCERN FOR TONIGHT IS THE POTENTIAL FOR WIDESPREAD RAINFALL AFTER
06UTC. HAVE LEFT THE MENTION AS SHRA AT BORDERLINE MVFR/IFR
CONDITIONS...BUT DID NOT MENTION THUNDER DUE TO THE UNCERTAINTY OF
EXACTLY WHERE THE UPSTREAM MCS WILL DEVELOP/TRACK. DESPITE THE
UPPER LEVEL CIRCULATION...LIGHT SURFACE FLOW SHOULD GENERALLY STAY
OUT OF THE SOUTH THE NEXT 24 HOURS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

SHORT TERM...CB
LONG TERM....CONSIDINE
MARINE.......CONSIDINE
AVIATION.....CB

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

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
450 AM EDT THU JUL 26 2007

MIZ047>049-053>055-060>063-068>070-075-076-082-083-270900-
MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER-
ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE-
450 AM EDT THU JUL 26 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF SOUTHEAST
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP THIS MORNING IN A
MOIST AND UNSTABLE AIRMASS. COVERAGE OF SHOWERS AND THUNDERSTORMS
WILL INCREASE DURING THE AFTERNOON AND EVENING. THUNDERSTORMS ARE
NOT EXPECTED TO BE SEVERE...BUT BRIEF HEAVY RAINFALL IS POSSIBLE.
STORM MOTION WILL BE TO THE NORTH AT 10 TO 15 MPH THROUGH THE
MORNING...THEN SHIFT EAST AT 10 TO 15 MPH DURING THE AFTERNOON.

ISOLATED TO SCATTERED THUNDERSTORMS WILL CONTINUE OVERNIGHT. THESE
THUNDERSTORMS ARE ALSO NOT EXPECTED TO BE SEVERE AS THEY TRACK
EASTWARD AT 15 TO 20 MPH. BRIEF HEAVY RAINFALL IS POSSIBLE WITH
THESE STORMS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL AFFECT
SOUTHEAST MICHIGAN ON FRIDAY. HEAVY RAINFALL WILL BE THE MAIN THREAT
FROM THESE THUNDERSTORMS...ALTHOUGH FEW STRONG STORMS MAY DEVELOP
NEAR THE OHIO BORDER.

THUNDERSTORM ACTIVITY WILL TAPER OFF FROM NORTH TO SOUTH FRIDAY
NIGHT...WITH ONLY ISOLATED THUNDERSTORMS EXPECTED ON SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

LCZ422-423-460-LEZ444-LHZ421-422-441>443-462>464-270900-
ST. CLAIR RIVER-DETROIT RIVER-LAKE ST. CLAIR-
MICHIGAN WATERS OF LAKE ERIE-OUTER SAGINAW BAY-INNER SAGINAW BAY-
PORT AUSTIN TO HARBOR BEACH MI-HARBOR BEACH TO PORT SANILAC MI-
PORT SANILAC TO PORT HURON MI-
LAKE HURON OFFSHORE BEYOND 5 NM FROM PORT AUSTIN TO HARBOR BEACH MI-
LAKE HURON OFFSHORE BEYOND 5 NM FROM HARBOR BEACH TO PORT SANILAC MI-
LAKE HURON OFFSHORE BEYOND 5 NM FROM PORT SANILAC TO PORT HURON MI-
450 AM EDT THU JUL 26 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR LAKE ST CLAIR...THE MICHIGAN
WATERS OF LAKE ERIE AND LAKE HURON.

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP THIS MORNING IN A
MOIST AND UNSTABLE AIRMASS. COVERAGE OF SHOWERS AND THUNDERSTORMS
WILL INCREASE DURING THE AFTERNOON AND EVENING. THUNDERSTORMS ARE
NOT EXPECTED TO BE SEVERE...BUT BRIEF HEAVY RAINFALL IS POSSIBLE.
STORM MOTION WILL BE TO THE NORTH AT 10 TO 15 MPH...ALTHOUGH STORMS
OVER LAKE ST CLAIR AND LAKE ERIE WILL BEGIN TO MOVE EASTWARD AT 10
TO 15 MPH DURING THE AFTERNOON.

OVERNIGHT...ISOLATED TO SCATTERED THUNDERSTORMS WILL CONTINUE.
THESE THUNDERSTORMS ARE ALSO NOT EXPECTED TO BE SEVERE AS THEY TRACK
EASTWARD AT 15 TO 20 MPH. BRIEF HEAVY RAINFALL IS POSSIBLE WITH
THESE STORMS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL AFFECT THE
MARINE AREAS ON FRIDAY. HEAVY RAINFALL WILL BE THE MAIN THREAT FROM
THESE THUNDERSTORMS...ALTHOUGH A FEW STRONG STORMS MAY DEVELOP NEAR
LAKE ERIE.

THUNDERSTORM ACTIVITY WILL TAPER OFF FROM NORTH TO SOUTH FRIDAY
NIGHT...WITH ONLY ISOLATED THUNDERSTORMS EXPECTED ON SATURDAY OVER
LAKE ST CLAIR AND LAKE ERIE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

HLO

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