Severe Thunderstorm Warning 45, NWS Gaylord, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1045 PM EDT SAT MAY 30 1998

MAINLY COSMETIC CHANGES EXPECTED TO NRN LWR/ERN UPR MI ZONE FCST
UPDATES. MAIN CONCERN OVERNIGHT WILL BE THE THREAT FOR SEVERE WEATHER.
00Z REGIONAL SOUNDINGS AND MODEL FCSTS CONTINUE TO INDICATE IMPRESSIVE
SHEAR PROFILE OVERNIGHT. MODIFIED KAPX 00Z HODOGRAPH FOR EXPECTED
CONDITIONS AT 09Z (USING 21Z RUC DATA) SHOWS STORM-RELATIVE HELICITIES
OF 230 IN 0-2 KM LYR AND 150 IN 0-3 KM LYR...ASSUMING STORM MOTION
EQUALING 0-3 KM MEAN WIND (250 AT 30-35 KTS). THIS WOULD TEND TO FAVOR
MULTICELL CLUSTER/LINE STORMS WITH GOOD BOW ECHO POTENTIAL. HWVR...
GIVEN EXPECTED WIND PROFILE A SLIGHT RIGHT TURN IN THE STORM MOTION
WOULD SIGNIFICANTLY INCREASE LOW LVL STREAMWISE HELICITY AND THUS
SUPERCELL POTENTIAL AS LONG AS THE INSTABILITY IS THERE.

PRIMARY QUESTION THEN WILL BE DEGREE OF LOW LVL INSTABILITY NECESSARY
TO TRANSPORT THESE HIGH WIND SPEEDS DOWN TO SFC. CURRENT KAPX WSR-88D
LOOPS INDICATING ELEVATED/WARM FRONTAL CONVECTION FIRING ACROSS
PORTIONS OF NW LWR. STRONG POSITIVE THTE ADVECTION AT 850 NOTED
UPSTREAM IN WAKE OF WARM FRONT...THOUGH INCREASING MSTR AT MID LVLS
WILL TEND TO LIMIT 850-700 MB THTE LAPSE RATES AND THUS POTENTIAL
INSTABILITY WITH ANY LIFT. 21Z RUC INDICATES MSTR FLUX CONVERGENCE AT
LOW LVLS PEAKING AROUND 09Z...WITH STRONG DYNAMICAL LIFT STILL EXPECTED
FROM RIGHT ENTRANCE/ LEFT EXIT COUPLING OF UPPER LEVEL JET CORES. 21Z
RUC ALSO SHOWS SFC DWPTS CREEPING INTO THE MIDDLE/UPR 60S ACRS SRN PTNS
OF NRN LWR BY 09Z...MUCH HIGHER THAN WHAT IS INDICATED BY NGM/FWC
GUIDANCE. THIS WORST-CASE SCENARIO WOULD LIMIT THE SFC-850 STABILITY/
CONVECTIVE INHIBITION (SFC BASED CAPES 1000-1500 G/KG, 850 MB BASED
CAPES OF 2000-2500 J/KG) AND THUS ALLOW A BETTER CHANCE FOR WET
MICROBURSTS. WILL HAVE TO CERTAINLY KEEP AN EYE ON IT...K-INDICIES
PEAKING OVER 40 WOULD CERTAINLY SUGGEST GOOD HEAVY RAIN POTENTIAL.

HURLEY

MIZ008-015>036-041-042-311800-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GAYLORD MI
110 AM EDT SUN MAY 31 1998

...SEVERE WEATHER POTENTIAL STATEMENT FOR NORTHERN LOWER AND EASTERN
UPPER MICHIGAN...

DISPATCHERS PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

THERE IS A MODERATE RISK OF SEVERE WEATHER FOR ALL OF NORTHERN LOWER
MICHIGAN SOUTH OF M-32...AND A SLIGHT RISK OF SEVERE WEATHER NORTH OF
M-32 ACROSS THE FAR NORTHERN PORTION OF THE LOWER PENINSULA TO INCLUDE
THE STRAITS AREA. AS A RESULT...SPOTTER ACTIVATION WILL LIKELY BE NEEDED
LATE TONIGHT TROUGH DAYBREAK. AT THIS TIME...ANY THUNDERSTORMS THAT
DEVELOP ACROSS EASTERN UPPER MICHIGAN ARE NOT EXPECTED TO BECOME
SEVERE.

THUNDERSTORMS THAT DEVELOPED LATE LAST EVENING WERE ASSOCIATED WITH A
WARM FRONT THAT WILL LIFT NORTHEAST AND CLEAR MUCH OF NORTHERN LOWER
MICHIGAN. SOUTH OF THIS WARM FRONT...BASICALLY SOUTH OF M-32...THE
AIRMASS IS EXPECTED TO BECOME MORE UNSTABLE LATE TONIGHT AS ANOTHER
LINE OF THUNDERSTORMS IS ANTICIPATED TO DEVELOP AHEAD OF A QUICK MOVING
COLD FRONT. THESE STORMS ARE EXPECTED TO REACH THE LAKE MICHIGAN
SHORELINE BETWEEN 3 AND 5 AM...THEN RACE EAST-NORTHEAST AT 45 MPH AND
REACH NORTHEAST LOWER MICHIGAN BETWEEN 5 AND  7 AM. STORMS SHOULD THEN
MOVE OUT OF NORTHERN LOWER MICHIGAN BY 8 AM.

THE PRIMARY SEVERE WEATHER THREAT FROM THESE STORMS WILL BE WIND GUSTS
OF 60 TO 70 MPH ASSOCIATED WITH SQUALL LINES. 1/2 TO 3/4 INCH HAIL IS
ALSO POSSIBLE.

THIS WEATHER SITUATION HAS THE POTENTIAL TO BECOME EXTREMELY DANGEROUS.
PLEASE STAY TUNDED TO NOAA WEATHER RADIO...YOUR LOCAL TELEVISION OR
RADIO STATIONS...OR THE INTERNET FOR THE LATEST WEATHER INFORMATION
CONCERNING THE THREAT OF SEVERE WEATHER IN NORTHERN LOWER MICHIGAN. ON
THE INTERNET GO TO WWW.CRH.NOAA.GOV/APX IN LOWER CASE LETTERS.

HURLEY

MIZ008-015>036-041-042-311800-

SEVERE WEATHER OUTLOOK...CORRECTED.
NATIONAL WEATHER SERVICE GAYLORD MI
110 AM EDT SUN MAY 31 1998

...SEVERE WEATHER POTENTIAL STATEMENT FOR NORTHERN LOWER AND EASTERN
UPPER MICHIGAN...

DISPATCHERS PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

THERE IS A MODERATE RISK OF SEVERE WEATHER FOR ALL OF NORTHERN LOWER
MICHIGAN SOUTH OF M-32...AND A SLIGHT RISK OF SEVERE WEATHER NORTH OF
M-32 ACROSS THE FAR NORTHERN PORTION OF THE LOWER PENINSULA TO INCLUDE
THE STRAITS AREA. AS A RESULT...SPOTTER ACTIVATION WILL LIKELY BE NEEDED
LATE TONIGHT TROUGH DAYBREAK. AT THIS TIME...ANY THUNDERSTORMS THAT
DEVELOP ACROSS EASTERN UPPER MICHIGAN ARE NOT EXPECTED TO BECOME
SEVERE.

THUNDERSTORMS THAT DEVELOPED LATE LAST EVENING WERE ASSOCIATED WITH A
WARM FRONT THAT WILL LIFT NORTHEAST AND CLEAR MUCH OF NORTHERN LOWER
MICHIGAN. SOUTH OF THIS WARM FRONT...BASICALLY SOUTH OF M-32...THE
AIRMASS IS EXPECTED TO BECOME MORE UNSTABLE LATE TONIGHT AS ANOTHER
LINE OF THUNDERSTORMS IS ANTICIPATED TO DEVELOP AHEAD OF A QUICK MOVING
COLD FRONT. THESE STORMS ARE EXPECTED TO REACH THE LAKE MICHIGAN
SHORELINE BETWEEN 3 AND 5 AM...THEN RACE EAST-NORTHEAST AT 45 MPH AND
REACH NORTHEAST LOWER MICHIGAN BETWEEN 5 AND  7 AM. STORMS SHOULD THEN
MOVE OUT OF NORTHERN LOWER MICHIGAN BY 8 AM.

THE PRIMARY SEVERE WEATHER THREAT FROM THESE STORMS WILL BE WIND GUSTS
OF 60 TO 80 MPH ASSOCIATED WITH SQUALL LINES. 1/2 TO 3/4 INCH HAIL IS
ALSO POSSIBLE.

THIS WEATHER SITUATION HAS THE POTENTIAL TO BECOME EXTREMELY DANGEROUS.
PLEASE STAY TUNDED TO NOAA WEATHER RADIO...YOUR LOCAL TELEVISION OR
RADIO STATIONS...OR THE INTERNET FOR THE LATEST WEATHER INFORMATION
CONCERNING THE THREAT OF SEVERE WEATHER IN NORTHERN LOWER MICHIGAN. ON
THE INTERNET GO TO WWW.CRH.NOAA.GOV/APX IN LOWER CASE LETTERS.

HURLEY