Severe Thunderstorm Warning 31, NWS Gaylord, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
400 PM EDT THU JUL 13 2000

EARLY AFTERNOON SURFACE ANALYSIS SHOWS A COUPLE OF TROFS NEARBY...ONE
ACROSS CENTRAL UPPER/NORTHEAST WI...WHICH ENHANCED BY LAKE BREEZE HAS
INITIATED A LINE OF SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN UPPER.  A
SECOND TROFS RUNNING NORTHEAST-SOUTHWEST ACROSS MN.  LAPS CAPE ANALYSIS
SHOWING A LARGE AREA ABOVE 1000 J/KG ACROSS NORTHERN LOWER...WITH 12Z
APX/GRB SOUNDING SHOWING A GOOD DEAL OF DRY AIR IN THE MID LEVELS WHILE
LAPSE RATES STEEPEN AT 850MB THERMAL RIDGE NUDGES INTO THE REGION.  WIND
PROFILES ARE UNIDIRECTIONAL...WITH STRONGER MID LEVEL WINDS CROSSING
INTO WI.  RAIN CHANCES THE MAIN PROBLEM THROUGH THE PERIOD.

TONIGHT...MID LEVEL SHORT WAVE PROGGED TO DROP SOUTHEAST INTO THE STATE
OVERNIGHT AS SURFACE REFLECTION ALSO CROSSES LOWER MI.  DECENT LOW LEVEL
LAPSE RATES/INSTABILITY AS LOW LEVEL CONVERGENCE AXIS CROSSES STATE...
ALONG WITH SUPPORT FROM UPPER TROF AXIS.  SO WILL CONTINUE MENTION OF
SHOWERS/THUNDERSTORMS LIKELY ALL AREAS TONIGHT. SEVERE POTENTIAL STILL
EXISTS ACROSS THE REGION...THOUGH THREAT SHOULD LESSEN OVERNIGHT AS
INSTABILITY DECREASES SOMEWHAT WITH LOSS OF HEATING.  ALREADY SOME
ISOLATED SEVERE ACROSS EASTERN UPPER THIS AFTERNOON.

FRIDAY...STRONG LOW LEVEL CYCLONIC FLOW AROUND LOW PASSING TO THE EAST
COMBINED WITH LINGERING INSTABILITY SHOULD RESULT IN SCATTERED SHOWER
AND THUNDERSTORM ACTIVITY ACROSS THE AREA TOMORROW...SIMILAR TO WHAT IS
OCCURRING TODAY ACROSS CENTRAL/WESTERN ONTARIO.  MUCH OF IT SHOULD BE
PRIMARILY DIURNALLY DRIVEN BUT WITH SOME LARGE SCALE FORCING ALREADY IN
PLACE DURING THE MORNING WILL KEEP POPS OPEN ENDED AND NOT TRY TO TIME
POTENTIAL DEVELOPMENT.  WILL GO MAINLY WITH SCATTERED COVERAGE WITH
INCREASING QG DOWNWARD FORCING DURING THE AFTERNOON.  WITH SOME CLOUDS
AROUND...EXPECT AFTERNOON HIGHS MAINLY IN THE 70S AREAWIDE.

FRIDAY NIGHT/SATURDAY...CYCLONIC FLOW HANGS ON FRIDAY NIGHT...THOUGH
Q-VECTOR PROGS CONTINUE TO SHOW STRONG DOWNWARD FORCING.  SO OTHER THAN
SOME LINGERING SHOWERS INTO THE EVENING...EXPECT RAIN CHANCES TO
DIMINISH WITH LOSS OF DIURNAL COMPONENT.  SIMILAR SITUATION SATURDAY AS
RIDGING SLOWLY TRIES TO PRESS IN FROM THE WEST...BUT IS HELD UP BY
DIGGING TROF INTO THE MID ATLANTIC.  AGAIN LARGE SCALE FORCING IS
PREDOMINANTLY DOWNARD IN LRQ OF SPEED MAX TO THE WEST.  MODELS ARE
SHOWING SOME SMALL CAPES DURING THE AFTERNOON...BUT RIGHT NOW THINK
RAIN CHANCES WILL BE TOO ISOLATED TO WARRANT A MENTION.  BEST CHANCES
LOOK TO BE OVER SOUTHEAST COUNTIES.

.EXTENDED...MODELS CONTINUE TO TREND TOWARD A MORE TYPICAL MID JULY
PATTERN WITH ZONAL FLOW ACROSS THE NORTHERN TIER OF STATES EARLY NEXT
WEEK WHILE A BROAD UPPER RIDGE TAKES UP RESIDENCE ACROSS THE SOUTHERN
PLAINS AND ROCKIES.  SHORT WAVE OFF THE BC COAST WILL GET KICKED EAST
AND FLATTEN UPPER RIDGE CURRENTLY OVER THE NORTHERN ROCKIES.  SUNDAY
STILL LOOKS DRY AS UPPER RIDGE AXIS SLIDES INTO THE WESTERN GREAT LAKES.
ALTHOUGH MAIN ENERGY REMAINS TO THE NORTH...COLD FRONT ASSOCIATED WITH
PROGRESSIVE BC SHORT WAVE WILL BRING A CHANCE FOR SHOWER/THUNDERSTORMS.
AS DISCUSSED YESTERDAY...WITH STRONG WESTERLIES IN THE VICINITY...
POSITION OF ASSOCIATED LOW LEVEL FRONTAL ZONE WILL PLAY A ROLE IN
MIDWEEK WEATHER.  MRF HAS BACKED OFF ON ITS HIGHLY SUSPICIOUS 1+" QPF
BULLSEYE OVER NORTHERN LOWER BY 12Z WEDNESDAY...INSTEAD PLACING ITS QPF
AXIS FROM IA EASTWARD INTO SOUTHERN LOWER/NORTHERN IN...A BETTER FIT TO
ITS PROGGED POSITION OF THE SURFACE BOUNDARY.  PLAN TO CONTINUE DRY
FORECAST FOR TUESDAY AND WEDNESDAY WITH A COUPLE OF CAVEATS...NORTHERN
LOWER MAY SEE SOME SHOWERS TUESDAY DEPENDING ON HOW FAR SOUTH THE FRONT
CAN PUSH BY THAT TIME...AND RETURN FLOW/WAA PRECIPITATION A CONCERN FOR
UPPER MICHIGAN WEDNESDAY THOUGH ATTM MRF KEEPING DEEPER MOISTURE JUST
TO THE NORTH.  WITH A RATHER PROGRESSIVE FLOW...TIMING OF SMALLER WAVES
BECOMES SUSPECT IN THE LONGER TIME PERIODS.  MODELS HINTING AT ANOTHER
SHORT WAVE MOVING ACROSS CENTRAL CANADA BY THURSDAY...STILL FAR ENOUGH
WEST THAT WILL GO DRY THURSDAY BUT THIS .MAY CHANGE DEPENDING ON SPEED
OF THIS SYSTEM.

COORDINATED WITH MQT (SHORT TERM/EXTENDED)/DTX.

.APX...NONE.

JPB