Severe Thunderstorm Warning 91, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
300 PM EDT WED AUG 2 2000

...DRY WEATHER ON THE WAY...

ONCE THE COLD FRONT CROSSES SOUTHWEST MICHIGAN THIS EVENING COOLER
AND DRIER AIR MOVES IN WITH SFC HIGH PRESSURE.  SFC WINDS BECOME
ANTICYCLONIC AFT 06Z AND WITH THE DRY AIR (1000 TO 500 MEAN RH 30
PCT AT 12Z THU) AND NORTH WINDS TO ALMOST 700 MB... CLEARING IS
NEARLY CERTAIN OVERNIGHT.  WILL FCST LOWS MID TO UPPER 50S NORTH...
NEAR 60 SOUTH.

THURSDAY THE INVERSION HEIGHT WILL FALL TO NEAR 5000 FT SO ONLY
LIMITED CU EXPECTED.  SIMILAR 1000/850 TEMP AND THICKNESS IN JULY
GAVE US HIGHS FROM MID TO UPPER 70S... SO WILL FCST HIGHS CLOSE TO
MOS.

THURSDAY NIGHT FINDS THE HIGH OVER LOWER MICHIGAN WITH MEAN
1000 TO 500 HR NEAR 25 PCT WITH LIGHT WINDS SO GOOD RADIATIONAL
COOLING EXPECTED... LOWS BELOW MOS.

NEXT SYSTEM COMING OVER THE TOP OF THE UPPER RIDGE WILL RESULT IN
INCREASING CLOUDINESS LATER FRIDAY BUT AT THIS POINT WILL BE
OPTIMISTIC AND FORECAST MOSTLY SUNNY.  THICKER CLOUDS WILL MOVE IN
FRIDAY NIGHT.

IN SHORT TERM CAPES STILL IN THE 1500 TO 2800 RANGE OVER CWA AND
FRONT JUST ABOUT TO COME THROUGH MKG AT 18Z. NVA INHIBITING CONVECTION
OVER SW LWR MI BUT SFC DEWPOINTS IN LOWER TO MID 70S NEAR JXN... SO
EXPECT CONVECTION TO DEVELOP EAST OF GRR LATE THIS AFTERNOON.
CONVECTION OVER WI NOT MAKING ACROSS LAKE DUE TO LAKE BREEZE/NNE
WINDS BEHIND FRONT SO DO NOT SEE THAT REACHING GRR AREA. THUS...
WILL HAVE SCT TSTMS ERN 1/2 CWA THIS EVENING AND CLEARING EVERYWHERE
OVERNIGHT.

ZONES BY 400 PM.

WDM

EXTENDED FORECAST DISCUSSION...
WILL MAINTAIN THE THEME OF THE PREVIOUS EXTENDED FORECAST... WHICH
KEPT THINGS DRY UNTIL LATE SATURDAY. THE WESTERN UPPER RIDGE
FLATTENS SOME DURING THE EXTENDED PERIOD... AS SHORTWAVES RIDE
OVERTOP OF IT AND TRY TO DIVE INTO THE NORTHEAST US. THE UPPER FLOW
LOOKS AS THOUGH IT WILL BECOME ZONAL FOR A SHORT TIME AS THE WESTERN
RIDGE FLATTENS... BUT IT DOES APPEAR THAT THINGS WILL AMPLIFY ONCE
AGAIN ON AND BEYOND DAY 5. IT/S DEFINITELY TOO EARLY TO CALL... BUT
SOME OF THE NEW GUIDANCE SUGGESTS THE WESTERN RIDGE MAY RE-ESTABLISH
ITSELF A BIT FURTHER EAST NEXT WEEK... WHICH COULD BRING SOME WARMER
WEATHER OUR WAY. IN ANY EVENT... OUR MAIN PCPN CHANCES DURING THE
EXTENDED WILL BE WITH THE WARM FRONT AND MOISTURE RETURN WHICH LOOKS
LIKE IT WILL OCCUR LATE SATURDAY... AND WITH THE COLD FRONTAL
PASSAGE WHICH LOOKS LIKE IT WILL OCCUR SUNDAY/SUNDAY NIGHT. THE
MODELS ARE A BIT DIFFERENT IN THEIR INDIVIDUAL TIMING OF THINGS...
BUT THE GENERAL THEME IS THE SAME. THE LATEST AVN AND CANADIAN
MODELS SUGGEST A POSSIBILITY OF SOME PCPN FRIDAY NIGHT WITH THE
INITIAL SURGE OF WARMER AIR AND MOISTURE... BUT WILL LEAVE THIS OUT
OF THE FORECAST FOR NOW... AND TIE PCPN CHANCES TO THE MAIN WARM
FRONTAL PASSAGE LATE SATURDAY. THE MRF IS SLOWEST TO PUSH THE COLD
FRONT THROUGH... NOT CLEARING IT SOUTH OF THE CWFA UNTIL MONDAY
MORNING. WILL TIME THINGS CLOSER TO THE CANADIAN... WHICH WOULD HAVE
ANY PCPN OUT OF THE AREA BY MONDAY.

TRH

.GRR...NONE.