Severe Thunderstorm Warning 21, NWS Marquette, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
330 PM EDT MON JUL 5 1999

...SHORT TERM FOCUS WILL BE ON CONVECTIVE/SVR THREAT...

UPR FLOW CHARACTERIZED BY BROAD UPR LEVEL HI CENTERED OVR SE CONUS
TODAY WITH N GREAT LKS ON N FRINGE OF CAPPED ATM PROFILE. MSAS ANALYSIS
DEPICTED 1004MB SFC LO OVR SW ONTARIO AT 17Z WITH COLD FRONT
EXTENDING INTO SW MN. MOIST SW LL FLOW CONTINUES TO TRANSPORT HI
THETA-E AIR INTO UPR MI WITH SFC DWPTS IN THE UPR 60S TO MID 70S.
12Z GRB SNDING CONTINUES TO SHOW A CAP NR 850MB...BUT IMPRESSIVE POS
ENERGY ABOVE CAPE ON ORDER OF 3500J/KG. CLUSTER OF SVR TSRA HAS
ALREADY PROGATED EASTWARD ACROSS N WI (NW OF GRB) THIS
MORNING...IMPLYING CAP CAN BE BROKEN. ETA PROG SOUNDING INDICATING
CAPE NR 2500J/KG AT MQT BY 23Z WITH LIS OF -7C. ETA EHIS OF
2.0-3.0 AT MQT/RHI ALSO IMPLY POTENTIAL FOR TORNADIC SUPERCELLS LATE
TODAY. RESIDUAL OUTFLOW BDRY AT 17Z EXTENDING ACROSS N WI LIKELY
BE FOCUS FOR NEXT ROUND OF CONVECTION. W CWA MOSTLY CLOUDY FREE AT
17Z WITH LK BREEZE CU EVIDENT ON VIS FROM ONT-CMX. THIS BNDRY COULD
ALSO FOCUS DEVELOPMENT LATE THIS AFTERNOON. WITH MID LEVEL W FLOW
INCREASING TO 40-50 KTS LATE TODAY...MAIN THREAT WITH SVR TSRA WILL
BE STRONG WINDS. ISO TORNADOES POSSIBLE IN REGIONS OF LOCALLY
ENHANCED LL DIRECTIONAL SHEAR...ESPECIALLY IN VICINITY OF LK BREEZE
FRONTS.

TONIGHT...NGM CONTINUES TO BE FASTER THAN ETA. PREFER ETA WITH
BETTER RUN TO RUN CONSISTENCY. COLD FRONT APPROACHES IWD AROUND 03Z
AND EXITS E CWA BY DAYBREAK. WILL GO WITH SCT SHRA/TSRA...ENDING BY
MIDNIGHT FAR WEST AND BY DAYBREAK EAST...WITH WORDING FOR SVR RISK.
NGM/ETA BOTH DEPICT INCREASING 700-300MB QVECTOR DIV OVR UPR MI
TUESDAY. ETA CU PARAMETERS SUGGEST A MOSTLY SUNNY DAY AS SFC LOW
DEEPENS OVER E ONTARIO. SFC HI PRS BUILDS INTO REGION TUE
NIGHT/WED... PROVIDING MORE SEASONABLE TEMPS. SHORTWAVE INBEDDED IN
NW UPR FLOW MAY INTRODUCE SOME CLDS ON TUES NIGHT/WED. QVECTOR
FIELDS ON BOTH NGM/ETA DO SUGGEST WK CONV BY 12Z WED. ETAS RH TIME
SECTION DEPICTS ONLY MODEST INCREASE IN MID-LEVEL MOISTURE TUESDAY
NIGHT...WHILE FWC REFLECTS NGM IS MORE MOIST. WILL GO PARLTY SUNNY
WEDNESDAY.

IN EXTENDED PERIOD...500MB FLOW RETROGRADES MOVING THE BROAD UPR
RIDGE OVR THE HI PLAINS ON WED TO A MEAN POSITION ALONG THE W NOAM
COAST BY FRI/SAT. THIS ULTIMATELY RESULTS IN DOWNSTREAM TROFFING OVR
E CANADA AND THE NE CONUS. AS THE SFC HI PRS RIDGE MVS EAST OF CWA
ON THURSDAY...THE MRF ADVERSTISES LEE SIDE CYCLOGENISIS OVR N HI
PLAINS IN RESPONSE TO DIGGING SHORTWAVE OVR NW CONUS. NCEP ENSEMBLE
MEMBERS SUGGEST MRF TOO AMPLIFIED WITH THIS FEATURE. THIS BIAS
CONTINUES THRU THE EXTENDED PERIOD WITH THE BUILDING RIDGE ALONG THE
W NOAM COAST. ECMWF SUPPORTS WEAKER SOLUTION SFC LO PRS TRACKING NE
ACROSS GREAT LAKES ON FRIDAY...AND INTO EASTERN CANADA SATURDAY.

IN DAILIES...RETURN MOISTURE RETURN FLOW/WAD DEVELOPS ACROSS
MISSISSIPPI VALLEY ON THURSDAY...INTRODUCES NEXT RISK OF CONVECTION INTO
W CWA...WHILE E CWA REMAINS STABLE. THURS NIGHT/FRIDAY SHORTWAVE
FEATURE AND ASSOCIATED SFC BNDRY MOVES THRU GREAT LAKES REGION WITH
GREATEST SHRA/TSRA THREAST GIVEN MINIMUM IN SHOWALTER INDEX. SAT LKS
DRIEST AND COOL WITH BELOW NORMAL TEMPS...FOLLOWED BY WEAK WAD AS
SFC HI PRS PASSES TO E ON SUNDAY. NEXT CHANCE OF SHRA ON MONDAY WITH
NEXT SHORTWAVE FEATURE DROPPING SE IN NW UPR FLOW.

COORD WITH APX.

.MQT...NONE.

WOLF

MIZ001-052145-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MARQUETTE MI
347 PM EDT MON JUL 5 1999

...SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 9 PM EDT...

A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR THE WESTERN HALF OF
LAKE SUPERIOR...INCLUDING ISLE ROYALE...UNTIL 9 PM EDT.

ISOLATED SEVERE THUNDERSTORMS ARE ALSO POSSIBLE OVER WEST AND
CENTRAL UPPER MICHIGAN LATER THIS EVENING.

IF YOU ARE CAUGHT OUTSIDE... SEEK REFUGE FROM THE STORM IN A
STRONG BUILDING. BOATERS ON WESTERN LAKE SUPERIOR SHOULD TAKE
SHELTER. DAMAGING WIND... LARGE HAIL... VERY HEAVY RAIN... AND
DANGEROUS LIGHTNING ARE ALL LIKELY. DO NOT SEEK SHELTER UNDER TREES
OR OTHER ISOLATED TALL OBJECTS. THESE ATTRACT LIGHTNING.

DAO

MIZ001-052145-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MARQUETTE MI
347 PM EDT MON JUL 5 1999

...SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 9 PM EDT...

A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR THE WESTERN HALF OF
LAKE SUPERIOR...INCLUDING ISLE ROYALE...UNTIL 9 PM EDT.

ISOLATED SEVERE THUNDERSTORMS ARE ALSO POSSIBLE OVER WEST AND
CENTRAL UPPER MICHIGAN LATER THIS EVENING.

IF YOU ARE CAUGHT OUTSIDE... SEEK REFUGE FROM THE STORM IN A
STRONG BUILDING. BOATERS ON WESTERN LAKE SUPERIOR SHOULD TAKE
SHELTER. DAMAGING WIND... LARGE HAIL... VERY HEAVY RAIN... AND
DANGEROUS LIGHTNING ARE ALL LIKELY. DO NOT SEEK SHELTER UNDER TREES
OR OTHER ISOLATED TALL OBJECTS. THESE ATTRACT LIGHTNING.

DAO

MIZ001>007-009>014-060400-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MARQUETTE MI
553 PM EDT MON JUL 5 1999

...A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR ALL OF WEST AND
CENTRAL UPPER MICHIGAN UNTIL MIDNIGHT EDT/11 PM CDT...

A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR GOGEBIC...
ONTONAGON...HOUGHTON...KEWEENAW...BARAGA...MARQUETTE...IRON...
DICKINSON...MENOMINEE...DELTA...SCHOOLCRAFT...ALGER AND LUCE
COUNTIES.

AT 550 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
NUMEROUS STRONG THUNDERSTORMS EXTENDING FROM WESTERN LAKE SUPERIOR
INTO NORTHWEST WISCONSIN. THE STORMS WILL QUICKLY MOVE EAST ACROSS
WEST AND CENTRAL UPPER MICHIGAN DURING THE EVENING. DAMAGING WINDS
IN EXCESS OF 60 MPH AND HAIL TO ONE INCH IN DIAMETER WILL BE
POSSIBLE WITH THE STRONGEST STORMS. VERY HEAVY RAIN WILL ALSO CAUSE
LOCAL PONDING OF WATER ON ROADS AND LOW-LYING AREAS.

BE ALERT FOR THREATENING WEATHER AND BE PREPARED TO MOVE TO STURDY
SHELTER SHOULD SEVERE WEATHER THREATEN. LISTEN TO NOAA WEATHER
RADIO...COMMERCIAL RADIO OR TELEVISION FOR FURTHER STATEMENTS AND
POSSIBLE WARNINGS.

ROLFSON