Severe Thunderstorm Warning 99, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
320 AM EDT WED AUG 9 2000

SHORT TERM DISCUSSION...
STATIONARY BOUNDARY SLICES THE FORECAST AREA IN TWO THIS MORNING
WITH DEW POINTS AROUND 70 IN THE SOUTH...DROPPING TO AROUND 60 IN
THE FAR NORTH UP TOWARD CADILLAC. THE STATIONARY FRONT ACTUALLY
STRETCHES FROM THE THUMB...WEST TO NEAR MUSKEGON...THEN FURTHER WEST
ACROSS CENTRAL PORTIONS OF WI. IT APPEARS THAT THERE IS A WEAK LOW
LOCATED IN NW WISCONSIN...FROM WHICH A COLD FRONT EXTENDS SOUTHWEST INTO
CENTRAL IOWA. THROUGH THE SHORT TERM PERIOD...WISCONSIN LOW IS
PULLED DOWN THE FRONT TODAY...WHICH WILL SWEEP THE COLD FRONT
THROUGH THE STATE. BY EVENING THE LOW IS FORECAST TO HAVE MOVED INTO
NORTHEAST OHIO WITH THE TRAILING COLD FRONT DROPPING INTO THE OHIO
VALLEY. HIGH PRESSURE BUILDS IN BEHIND THE COLD FRONT TONIGHT AND
THURSDAY. ALOFT...SHORTWAVE ASSOCIATED WITH THE SFC WAVE IS SEEN IN
THE WATER VAPOR IMAGERY OVER NRN WISCONSIN. THIS WAVE WILL SWING
ACROSS THE NORTHERN GREAT LAKES TODAY WITH A WEAKER VORT LOBE PROGD
TO MOVE THROUGH THE SOUTHERN GREAT LAKES.

BIGGEST FORECAST CONCERN WILL BE TO ASSESS THE THREAT FOR
THUNDERSTORMS AHEAD OF THE ADVANCING COLD FRONT TODAY.
OTHERWISE...CLOUD COVER WILL BE THE CHALLENGE. SHORT TERM MODELS ALL
SIMILAR WITH THE MAIN FEATURES...BUT HAVE OPTED TO FOLLOW THE ETA.

FOR TODAY...IT APPEARS THERE WILL BE ENOUGH OF A CHANCE TO MENTION A
SCATTERED SHOWER OR THUNDERSTORM POSSIBLE. BEST CHANCE WILL BE IN
THE FAR SOUTHEAST TOWARD JACKSON THIS AFTERNOON...AS THE AIR MASS
WILL HAVE A CHANCE TO DESTABILIZE THROUGH HEATING. VORT LOBE TO
AFFECT THE FCST AREA IS ON THE WEAK SIDE...AND NOT MUCH IN THE WAY
OF WARM AIR ADVECTION TO SPEAK OF EITHER. WE ACTUALLY START TO BRING
IN COOLER AIR AT 850MB/S THIS AFTERNOON. JET RELATED LIFT NOT A BIG
HELP EITHER WITH THE AXIS OVERHEAD. LEFT EXIT REGION LIFT WILL BE TO
THE NORTHEAST OF THE AREA...AND THE RIGHT ENTRANCE REGION LIFT WILL
BE TO OUR SOUTH. GIVEN BOUNDARIES MOVING THROUGH THE AREA AND LOWER
TROP MOISTURE STILL IN PLACE THOUGH...WILL USE 30 POPS TO COVER THINGS.
BEST CHANCES FOR ANY SIGNIFICANT CONVECTION APPEAR TO BE OFF TO THE
EAST AND SOUTH OF THE GRR FCST AREA. HIGHS SHOULD RANGE FROM AROUND
80 TO THE NORTH AND THE LOWER 80S IN THE SOUTHEAST. CU SCHEME
INDICATES GOOD POTENTIAL TODAY FOR CUMULUS DEVELOPMENT...SO MAY JUST
USE A PARTLY CLOUDY WORDING.

TONIGHT...FCST AREA WILL BE ON THE EDGE OF UPPER LEVEL CYCLONIC
FLOW...WITH THE POTENTIAL FOR AC AND CI PATCHES DRIFTING BY. WILL
CONTINUE THE GOING FORECAST OF PARTLY CLOUDY.

ON FRIDAY MUCH OF THE SAME...WITH CYCLONIC UPPER FLOW HANGING ON AND
CU POTENTIAL ONCE AGAIN. WILL USE THE GOING PARTLY CLOUDY WORDING.
WILL STAY NEAR GUIDANCE VALUES TONIGHT AND WED REGARDING TEMPS.

DUKESHERER

EXTENDED FORECAST DISCUSSION...
EXTENDED PERIOD STILL LOOKS DRY AND PLEASANT AT THIS POINT...WITH
MEDIUM RANGE MODELS IN FAIR AGREEMENT WITH RESPECT TO UPPER LEVEL
FEATURES. LATEST 00Z CANADIAN DOES BRUSH NRN LOWER MI WITH THE
TAIL-END OF A WEAKENING SHORTWAVE LATE SAT/EARLY SUN...BUT ALL OTHER
MODELS KEEP THIS FEATURE FARTHER N ACROSS ONTARIO. FLATTENED RIDGE
TO BUILD IN FOR WEEKEND WITH WEAK ZONAL FLOW ACROSS THE FORECAST
AREA. INCREASING HEAT AND HUMIDITY WILL BUILD ACROSS THE REGION ON
SUN WITH A SWRLY SFC FLOW BECOMING ESTABLISHED. ECMWF AND PREVIOUS
RUN OF MRF LAY THE GROUNDWORK FOR A HOT WEEK NEXT WEEK...POSSIBLY
THE HOTTEST OF THE SUMMER THUS FAR. THIS WILL BE SOMETHING TO WATCH
IN THE COMING DAYS.

GREENE

.GRR...NONE.

T