Severe Thunderstorm Warning 5, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
325 AM EDT THU APR 20 2000

SFC LOW CENTERED IN NORTHWEST MISSOURI THIS MORNING...WITH A SFC
WARM FRONT EXTENDING TO THE EAST ACROSS NORTHERN ILLINOIS AND
INDIANA. 850MB WARM TO THE NORTH OF THE SFC FRONT EXTENDING ACROSS
SOUTHERN WISCONSIN AND SOUTHERN LOWER MICHIGAN. LLJ ACROSS ILLINOIS
INTERSECTS THIS ELEVATED BOUNDARY AND CONTINUES TO INITIATE
CONVECTION TO THE WEST WHICH MOVES EAST INTO MICHIGAN WITH THE MEAN
FLOW. KILX (CENTRAL ILLINOIS) VAD WIND PROFILE INDICATES A 65KT LLJ
OUT OF THE SOUTH WHICH IS OBVIOUSLY PROVIDING STRONG CONVERGENCE
ALONG THE ELEVATED WARM FRONT...HENCE THE WIDESPREAD CONVECTION.
THROUGH THE SHORT TERM...ATTENTION OBVIOUSLY FOCUSED ON THE SYSTEM
IN MISSOURI WHICH MOVES EAST TOWARD THE SOUTHERN GREAT LAKES TODAY.
PCPN CHANCES ARE THE MAIN CONCERN ALONG WITH HEAVY RAINFALL.

AVN HAS DONE VERY WELL WITH THIS SYSTEM AND HAS BEEN CONSISTENT FOR
FOUR RUNS IN A ROW IN BRINGING THE SFC LOW ACROSS NORTHERN INDIANA.
ETA AND NGM HAVE COME BACK TO A NORTHERN SOLUTION...SO HARD TO ARGUE
WITH THE CONSISTENCY OF THE AVN. CURRENT PRESSURE FALLS OVER THE
SOUTHERN GREAT LAKES ALSO SUPPORT A TRACK TOWARD SOUTHERN LOWER
MICHIGAN OUT OF NORTHERN MISSOURI.

TODAY...LLJ OVER ILLINOIS...SHIFTS TO THE EAST AS WILL THE FOCUS FOR
CONVECTION. EXPECT PERIODS OF SHOWERS AND THUNDERSTORMS TO CONTINUE
TODAY AS THE ELEVATED WARM FRONT WILL REMAIN ACROSS THE AREA WITH
PLENTY OF MOISTURE STREAMING NORTH ON THE LLJ. 850MB DEW POINTS IN
THE LOWER TEENS ARE PLENTY ENOUGH TO PRODUCE ELEVATED INSTABILITY.
DIFFERENTIAL THETA-E CONTINUES TO SHOW THETA-E DECREASING WITH
HEIGHT IN THE 850-500MB LAYER CONFIRMING THE ELEVATED INSTABILITY.
BULLSEYE OF THETA-E CONVERGENCE ALSO MOVING ACROSS THE AREA. NEXT
CONCERN TODAY IS THE POTENTIAL FOR HEAVY RAIN. P-WATER VALUES ARE IN
EXCESS OF AN INCH TODAY...AND WITH THE WARM FRONT PROVIDING THE
FOCUS...TRAINING PCPN WILL OCCUR...MAKING HEAVY RAIN POSSIBLE. WILL
CONTINUE THE MENTION OF HEAVY RAIN TODAY.

TONIGHT...FOCUS FOR CONVECTION WILL SHIFT EAST DURING THE LATE
AFTERNOON...SO...WILL NOT MENTION ANY THUNDER IN THE TONIGHT PORTION
OF THE FORECAST. WILL USE AN OCCASIONAL RAIN TYPE OF WORDING AS THE
UPPER LOW SLIPS BY TO THE SOUTH.

ON FRIDAY...LIFT VIA THE UPPER LOW LINGERS AS DOES MOISTURE...WILL
USE CHANCE WORDING NORTH FOR MORNING SHOWERS. IN THE SOUTH SHOWERS
WILL BE LIKELY IN THE MORNING...TAPERING OFF IN THE EARLY AFTERNOON
AS THE SUPPORT PULLS AWAY TO THE EAST. WILL MENTION SKIES BECOMING
PARTLY CLOUDY NORTH IN THE AFTERNOON...AND PARTIAL CLEARING POSSIBLE
IN THE SOUTH DURING THE LATE AFTERNOON.

NGM MOS GENERALLY IN THE BALLPARK...BUT WILL GO HIGHER IN THE SOUTH
DAY AS THE WARM FRONT ENCROACHES ON THE AREA.

DUKESHERER

EXTENDED FORECAST DISCUSSION...
EXTENDED PERIOD STILL LOOKS DRY WITH PLENTY OF SUNSHINE FOR EASTER
WEEKEND. UPPER LEVEL LOW WILL PULL AWAY FRI NIGHT...WITH CLOUDS
CLEARING THE FORECAST AREA FROM WEST TO EAST. COLDER AIR IN THE WAKE
OF THE SYSTEM...BUT RESIDUAL PRES GRADIENT SHOULD PREVENT
DECOUPLING...SO WILL KEEP TEMPS ABOVE FREEZING FRI NIGHT. DECIDED TO
INTRODUCE SOME CLOUDS INTO SATURDAYS FORECAST AS NRN STREAM
SHORTWAVE BRUSHES ACROSS THE NRN GREAT LAKES. EXPECT NOTHING MORE
THAN AC/CI SAT AFTERNOON. SUN AND MON LOOK MAINLY CLEAR WITH A SLOW
WARMING TREND. NIGHTS WILL BE CHILLY AND FROST/FREEZE CERTAINLY A
POSSIBILITY SAT AND SUN NIGHTS. H5 NWRLY FLOW PATTERN WILL
TRANSITION INTO RIDGING FROM SUN TO MON...BRINGING A SLOW WAA
PATTERN.

GREENE

.GRR...NONE.

MIZ037>040-043>046-050>052-056>059-064>067-071>074-211000-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
655 AM EDT THU APR 20 2000

...HAZARDOUS WEATHER POTENTIAL STATEMENT FOR THE SOUTHWEST QUARTER OF
LOWER MICHIGAN FOR TODAY AND TONIGHT...

DISPATCHERS PLEASE PASS THIS INFORMATION ALONG TO YOUR EMERGENCY
MANAGERS.

HAZARDS...
THUNDERSTORMS ARE EXPECTED TODAY...WITH LIGHTNING AND HEAVY RAINFALL
BEING THE PRIMARY THREATS. LOCAL PONDING OF WATER ON AREA ROADWAYS
AND RISING WATER IN SMALL CREEKS AND STREAMS CAN BE EXPECTED. IN
ADDITION A FEW OF THE STRONGEST STORMS HAVE THE POTENTIAL TO
PRODUCE HAIL TO A HALF INCH IN DIAMETER. THUNDERSTORMS CAN BE
EXPECTED FROM DAYBREAK THROUGH ABOUT 700 PM THIS EVENING. STORM
MOVEMENT WILL BE TO THE NORTHEAST AT 20 TO 30 MPH.

DISCUSSION...
A WARM FRONT WILL REMAIN IN PLACE TO THE SOUTH OF THE STATE OF
MICHIGAN OVER NORTHERN PORTIONS OF INDIANA TODAY. THE WARM FRONT
WILL BE THE FOCUS FOR SHOWERS AND THUNDERSTORMS TODAY AS WARM MOIST
AIR RIDES UP AND OVER THE WARM FRONT. SHOWERS AND THUNDERSTORMS WILL
REPEATEDLY MOVE OVER THE SAME AREAS ACROSS SOUTHERN LOWER MICHIGAN
MAKING HEAVY RAINFALL A GOOD POSSIBILITY. THE HEAVIEST RAINFALL
THROUGH DAYBREAK HAS BEEN ALONG AND SOUTH OF INTERSTATE 96.
AMOUNTS BETWEEN AN INCH AND A INCH AND A HALF HAVE BEEN REPORTED AT
GRAND RAPIDS...HOLLAND AND MUSKEGON SINCE YESTERDAY. ANOTHER HALF TO
AROUND ONE INCH OF RAIN IS POSSIBLE DURING THE NEXT 24 HOURS.

SPOTTER ACTIVATION...
AT THIS TIME...SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR
TONIGHT.

...HAZARDOUS WEATHER POTENTIAL OUTLOOK FOR FRIDAY THROUGH
MONDAY...

HAZARDOUS WEATHE;R IS NOT EXPECTED IN THE OUTLOOK PERIOD OF FRIDAY
THROUGH MONDAY.

DUKESHERER

MIZ037>040-043>046-050>052-056>059-064>067-071>074-211000-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
900 AM EDT THU APR 20 2000

...HAZARDOUS WEATHER POTENTIAL STATEMENT FOR THE SOUTHWEST QUARTER OF
LOWER MICHIGAN FOR TODAY AND TONIGHT...

DISPATCHERS PLEASE PASS THIS INFORMATION ALONG TO YOUR EMERGENCY
MANAGERS.

HAZARDS...
THUNDERSTORMS ARE EXPECTED TODAY...WITH LIGHTNING AND HEAVY RAINFALL
BEING THE PRIMARY THREATS. MINOR OVERFLOW OF THE  SMALL CREEKS AND
STREAMS CAN BE EXPECTED. POOR DRAINAGE FLOODING WILL OCCUR IN URBAN
AREAS AS WELL.

ADDITION A FEW OF THE STRONGEST STORMS HAVE THE POTENTIAL TO
PRODUCE HAIL TO A HALF INCH IN DIAMETER AND SOME WIND GUSTS TO
60 MPH. ONE CLUSTER OF THUNDERSTORMS OVER CHICAGO THIS MORNING
WILL PULL THROUGH SOUTHWEST LOWER MICHIGAN BY NOON.  THESE STORMS
HAVE HAD A HISTORY OF PRODUCING DAMAGING WINDS IN ILLINOIS.

DISCUSSION...
A WARM FRONT WILL REMAIN IN PLACE TO THE SOUTH OF THE STATE OF
MICHIGAN OVER NORTHERN PORTIONS OF INDIANA TODAY. THE WARM FRONT
WILL BE THE FOCUS FOR SHOWERS AND THUNDERSTORMS TODAY AS WARM MOIST
AIR RIDES UP AND OVER THE WARM FRONT. SHOWERS AND THUNDERSTORMS WILL
REPEATEDLY MOVE OVER THE SAME AREAS ACROSS SOUTHERN LOWER MICHIGAN
MAKING HEAVY RAINFALL A GOOD POSSIBILITY. THE HEAVIEST RAINFALL
THROUGH DAYBREAK HAS BEEN ALONG AND SOUTH OF INTERSTATE 96.
AMOUNTS BETWEEN AN INCH AND A INCH AND A HALF HAVE BEEN REPORTED AT
GRAND RAPIDS...HOLLAND AND MUSKEGON SINCE YESTERDAY. ANOTHER HALF TO
AROUND ONE INCH OF RAIN IS POSSIBLE DURING THE NEXT 24 HOURS.

SPOTTER ACTIVATION...
AT THIS TIME...SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR
TONIGHT.

...HAZARDOUS WEATHER POTENTIAL OUTLOOK FOR FRIDAY THROUGH
MONDAY...

HAZARDOUS WEATHER IS NOT EXPECTED IN THE OUTLOOK PERIOD OF FRIDAY
THROUGH MONDAY.

MJS