Severe Thunderstorm Warning 27, NWS Marquette, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
350 PM EDT FRI JUN 30 2000

MAIN FORECAST CONCERN IS CHANCE OF SHRA/TSRA THROUGH THE ENTIRE
PERIOD.

12Z RAOBS SHOW UPR RIDGE FROM SW CONUS EXTENDING NORTH ALONG
ALB/SASKATCHEWAN BORDER. DOWNSTREAM...A TROF EXTENDS FROM UPPER LOW
OVER HUDSON BAY TO NEW ENGLAND. WV IMAGERY SHOWS ONE SHORTWAVE OVER
N ALBERTA ABOUT TO CREST RIDGE AND ANOTHER DISTINCT SHORTWAVE
ROTATING AROUND WESTERN EDGE OF HUDSON BAY LOW ABOUT TO ENTER NW
ONTARIO. H85 RAOBS ALSO SHOW ABUNDANT GULF MOISTURE (DEWPOINT
DEPRESSIONS AOB 5C) PUSHING INTO KANSAS UNDER SOUTHERLY FLOW. 16Z
SFC ANAL SHOWS TROF/DIFFUSE LOW AHEAD OF SHORTWAVE FROM SASKATCHEWAN
EASTWARD TO CNTL ONTARIO.

MODELS IN GENERAL AGREEMENT...BUT SHOW DIFFERENCES IN POSITION OF
FRONTAL BOUNDARY WHICH WILL DROP NEAR/ACROSS UPR MI SAT EVE/NIGHT
AND SUNDAY. NGM PUSHES FRONT SOUTH OF UPR MI BY 12Z SUN. ETA DROPS
FRONT INTO N UPR MI LATE SAT AFTERNOON AND BECOMES STATIONARY FROM
KIWD TO KERY THROUGH SUN MORNING. AVN DOESNT BRING FRONT ACROSS UPR
MI UNTIL SUN AFTERNOON...THEN BRINGS A LOW CENTER ACROSS CNTRL WI
AND GENERATES OVER 2 INCH BULLSEYE SUNDAY NIGHT OVER WI BORDER
COUNTIES IN WHAT LOOKS LIKE A CONVECTIVE FEEDBACK PROBLEM. STRENGTH
OF AVN SHORTWAVE AT 72 HOURS LIKELY RELATED TO THIS SAME
PROBLEM...AS ARE HIGH PRECIP AMOUNTS. I LIKE THE ETA SOLUTION OF
DROPPING FRONT INTO THE U.P. AND KEEPING IT STATIONARY. CONFIDENCE
SOMEWHAT LACKING IN EXACT POSITION OF FRONT...SO WONT GET TOO FANCY.

TONIGHT...WILL COVER DIURNALLY DRIVEN SHRA/TSRA CURRENTLY OBSERVED
BY KMQT 88D WITH SCATTERED EVENING WORDING. MODELS IN SIMILAR
AGREEMENT IN TAKING SHORTWAVE AROUND HUDSON BAY LOW TO JAMES BAY BY
12Z SAT. SFC LOW ALSO BECOMES MORE CONSOLIDATED NEAR JAMES BAY BY
12Z AS ASSOCIATED TRAILING COLD FRONT MOVES TO JUST NORTH OF LAKE
SUPERIOR. ETA BRINGS PRECIP ACROSS MAINLY N COUNTIES OVERNIGHT AS
FRONT SINKS SOUTHWARD. WEAK H7-H3 QVEC CONV AHEAD OF SHORTWAVE
OVERSPREADS UPR MI AFTER 06Z WHILE SI INDICES HOVER NEAR 0. A FEW
SHOWERS OCCURRING NEAR LAKE WINNIPEG BASED ON CANADIAN RADAR AND SFC
OBS. WILL MENTION SCATTERED SHOWERS AND ISOLATED TSRA DEVELOPING
OVERNIGHT...BUT PLAY IT DOWN FOR SOUTHERN COUNTIES FARTHER FROM
FRONT.

SATURDAY...SW WINDS INCREASE LOW LEVEL MOISTURE AND INSTABILITY.
FORECAST SOUNDINGS SHOW GOOD MIXING TO AROUND 800MB. BUMPED WINDS UP
TO 10 TO 20 MPH RANGE. MAY NEED TO NUDGE UP A LITTLE MORE. ETA CAPES
REACH VALUES NEAR 2000 J/KG DURING AFTERNOON BASED ON DEWPOINTS NEAR
65F. ETA DEWPOINTS ARE HIGH COMPARED TO AVN/NGM AND MOS OUTPUT. EVEN
WITH DEWPOINTS AROUND 60F...MODIFIED ETA FORECAST SOUNDING FOR MQT
GENERATES 1600 J/KG CAPE AND LI NEAR -5 WITH T/TD OF 80F/60F...MORE
THAN ENOUGH FOR TSRA. WILL EMPHASIZE AFTERNOON FOR TIMING WITH BEST
HEATING AND FRONT NEAR NORTHERN COUNTIES.

SATURDAY NIGHT AND SUNDAY...FRONT REMAINS NEARLY STATIONARY FROM
KIWD TO KERY THROUGH THE PERIOD. CAPE VALUES RANGE FROM 200 J/KG
(NORTH) TO OVER 1000 J/KG (SOUTH) DURING THE PERIOD. ETA HINTS AT
CONVECTIVE SYSTEM FORMING IN AREA OF H85 CONV SUN MORNING NEAR W UPR
MI/N WISCONSIN. WILL KEEP CHANCE POPS FOR SAT NIGHT...AND LIKELY FOR
SUNDAY. GIVEN UNCERTAINTY OF EXACT FRONTAL LOCATION AND SOME
ISENTROPIC LIFT DEPICTED TOWARD SW COUNTIES...WILL USE 60 POPS
EVERYWHERE FOR SUNDAY. NUDGED TEMPS DOWN FOR SUNDAY BASED ON
EXPECTED CLOUD COVER AND POSSIBLE COOLER AIR NORTH OF FRONT. FWC
GUIDANCE IN LOW 70S MAINLY DUE TO NGM PUSHING FRONT FARTHER SOUTH
AND COOLER NORTH WIND.

EXTENDED...NO SIGNIFICANT CHANGES PLANNED TO EXTENDED PERIOD.
MRF/ECMWF/UKMET REMAIN IN AGREEMENT IN STRENGTHENING THE SUBTROPICAL
RIDGE OVER CENTRAL CONUS OVER WEEKEND AND EARLY NEXT WEEK. MRF
ENSEMBLES SUPPORT THIS SCENARIO...WITH MANY ENSEMBLE MEMBERS
DEPICTING A STRONGER CENTRAL CONUS HIGH. LATEST MRF RUN HAS BACKED
AWAY FROM SWINGING DEEP HUDSON BAY LOW SOUTHEAST TUE/WED.
CONSEQUENTLY...EXPECT UPR MI TO REMAIN UNDER PERIPHERY OF UPR RIDGE
RATHER THEN HAVING A TEMPORARY COOLER NW FLOW. LATEST MEX/FMR
GUIDANCE REFLECTS THIS...MAINTAINING TEMPS GENERALLY 75-80F RANGE
NORTH AND 80-85F SOUTH. DONT HAVE MUCH CONFIDENCE IN HOW MRF TIMES
WEAK SHORTWAVES RIDING OVER RIDGE...SO WILL JUST MENTION CHANCE
SHRA/TSRA...BUT EMPHASIZE THE WARMTH/HUMIDITY DURING THE WEEK.

.MQT...NONE.

JS

MIZ001>007-009>014-302100-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MARQUETTE MI
1205 PM EDT FRI JUN 30 2000

...SEVERE WEATHER OUTLOOK FOR WEST AND CENTRAL UPPER MICHIGAN...

ISOLATED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER
UPPER MICHIGAN LATE THIS AFTERNOON AS INCREASING SURFACE TEMPERATURES
DESTABILIZE THE ATMOSPHERE. THE BEST CHANCE FOR THUNDERSTORMS THIS
AFTERNOON WILL BE OVER INLAND PORTIONS OF WEST UPPER MICHIGAN AND
NEAR LAKE MICHIGAN TO THE SOUTHEAST. TONIGHT...ADDITIONAL
THUNDERSTORMS MAY DEVELOP OVER WEST AND CENTRAL UPPER MICHIGAN AS
MORE WARM MOIST AIR MOVES TOWARD THE AREA FROM THE SOUTHWEST. NONE
OF THE STORMS THIS AFTERNOON OR TONIGHT ARE EXPECTED TO BECOME
SEVERE. ANY STORMS THAT DEVELOP WILL MOVE EAST AT 20 MPH AND MAY
PRODUCE HAIL TO A HALF INCH...GUSTY WINDS TO 45 MPH ALONG WITH
DEADLY LIGHTNING.

STAY TUNED TO NOAA WEATHER RADIO...OR COMMERCIAL RADIO AND
TELEVISION FOR FUTURE STATEMENTS ON DEVELOPING THUNDERSTORMS.

JLB