Severe Thunderstorm Warning 14, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
305 PM EDT MON MAY 06 2002

MAIN FORECAST PROBLEMS IN THE NEAR TERM ARE FOR POPS TONIGHT...AND
AGAIN ON TUE NIGHT...AND FOR MAX TEMPS ON TUE. THE AREA OF CLEARING
ACROSS SOUTHERN WISCONSIN HAS RESULTED IN SOME SFC BASED INSTABILITY
THIS AFTERNOON...WITH LAPS SOUNDINGS SHOWING LIS IN THE -6 TO -8
RANGE THERE ATTM. SFC COLD FRONT WILL BE MOVING INTO THIS AREA THIS
EVENING AND COULD FOCUS SOME ORGANIZED CONVECTION. SOME QUESTION AS
TO THE EXTENT AND COVERAGE OF THESE STORMS AS THEY MOVE INTO GRR
CWA...WHERE CLOUDS HAVE BEEN SLOW TO BREAK UP THIS AFTERNOON. WILL
GO WITH CHANCE POPS AS IT APPEARS AT LEAST SCATTERED COVERAGE IS
LIKELY WITH THE APPROACH OF THE FRONT. AS FOR SVR...ENVIRONMENTAL
WINDS ARE NOT OVERLY IMPRESSIVE...WITH 50 KT WINDS CONFINED TO AOA
10 KFT. FREEZING LEVEL IS AOA 10 KFT...SO IT WOULD TAKE SOME HEFTY
STORMS TO PRODUCE SVR HAIL.

THE COLD FRONT PUSHES THROUGH THE SE CWA AROUND 12Z TUE...AND WILL
NOT CARRY POPS FOR THE SECOND PERIOD. SHOULD BE PLENTY OF STRATUS
BEHIND THE FRONT DURING MORNING...WITH SFC HIGH NOSING IN AND DRYING
OCCURRING BY AFTERNOON. CLOUDS SHOULD BREAK UP WITH SKIES BECOMING
MOSTLY SUNNY AFT 18Z. BIG DISPARITY BETWEEN FWC AND MAV TEMPS. WILL
GO CLOSER TO THE COOLER MAV...AS SHALLOW COOL AIR MASS SHOULD WORK
IN BY THE TIME THE CLOUDS BREAK UP BEHIND THE FRONT.

FRONT MOVES BACK AS A WARM FRONT LATE TUE NIGHT. GOOD OVERRUNNING
SETS UP AS LOW LEVEL JET INTERSECTS THE FRONT. WILL BRING IN
LIKELY POPS LATE FOR SOUTHERN HALF OF CWA...AND GO CHANCE NORTH.
MAIN SLUG OF QPF COMES THROUGH WEDNESDAY MORNING AS WARM FRONT
MARCHES ACROSS CWA. WILL LEAVE CHANCE POPS GOING FOR WED NIGHT AS
SFC LOW MOVES THROUGH AND COLD FRONT APPROACHES.

OSTUNO

EXTENDED FORECAST DISCUSSION...
NEGATIVELY-TILTED UPPER TROUGH SHOULD MOVE ACROSS THE FORECAST AREA
THURSDAY MORNING...BRINGING AN END TO EARLY MORNING SHOWERS AS THE
SFC COLD FRONT MOVES THROUGH. STRONG COLD ADVECTION NOTED BY 12Z AVN
BEHIND THIS SFC FRONT...WITH 850MB TEMPS FALLING BELOW ZERO DEG C
THURSDAY AFTERNOON. CLOSED UPPER LOW WILL REMAIN NORTH OF LAKE
SUPERIOR...THEREFORE IT APPEARS THE WRAP-AROUND LOW LEVEL MOISTURE
WILL BYPASS OUR FORECAST AREA TO THE NORTH. WILL FEATURE IMPROVING
SKY CONDITIONS WITH FALLING TEMPS THURSDAY AFTERNOON.

THE FROST/FREEZE POTENTIAL FOR THURSDAY NIGHT DOES NOT LOOK AS
SIGNIFICANT...DUE TO SFC WIND SPEEDS WHICH MAY STAY UP DUE TO
PRESSURE GRADIENT ACCORDING TO 12Z AVN. AS HIGH PRESSURE MOVES TO
MID-ATLANTIC BY 12Z SATURDAY...SFC FLOW BECOMES SOUTH TO SOUTHEAST
AND UPPER FLOW SWRLY. PREFER SLOWER AND MORE AMPLIFIED DEPICTION OF
NEXT UPSTREAM UPPER WAVE AND WILL HOLD OFF ON PRECIP UNTIL
SUNDAY...PER ECMWF. PASSAGE OF UPPER WAVE AND SFC FRONT SHOULD BRING
DRIER AND SLIGHTLY COOLER AIR INTO THE REGION BY MONDAY. THIS FRONT
WILL BE OF PACIFIC ORIGIN...THEREFORE TEMPERATURES BY MONDAY SHOULD
BE NEAR CLIMATOLOGICAL NORMALS.

GREENE

.GRR...NONE.