Severe Thunderstorm Warning 144, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
410 PM EDT SAT JUL 17 2004

.SHORT TERM...
THE MAIN ISSUES TONIGHT ARE HOW QUICKLY THE CONVECTION ENDS THIS
EVENING...THEN WHERE WILL IT BE IN OUR CWA ON SUNDAY AFTERNOON (MORE
DAY TIME HEATING ISSUES), THEN FINALLY, HOW MUCH AND WHERE WILL THE
CONVECTION BE MONDAY NIGHT AND TUESDAY WITH THE NEXT NORTHERN STREAM
SHORTWAVE.  SEEMS THERE IS LITTLE THREAT OF SEVERE WEATHER THROUGH
TUESDAY... SAVE THE RISK OF AN ISOLATED MARGINAL HAIL REPORT EARLY
THIS EVENING.

TONIGHT...DEPARTING UPPER SYSTEM COMBINED WITH 1000 TO 2000 J/KG OF
CAPE AND LAPSE RATES NEAR 6.5C/KM WITH NO CAPE HAVE ALLOWED SCT
SHOWERS AND THUNDERSTORM TO DEVELOP.  LAKE BREEZE HAS MADE IT INLAND
TO US-31. SINCE DEEP LAYER SHEAR IS VERY LOW (MOSTLY UNDER 10 KNOTS)
AND NO SIGNIFICANT LOW OR MID LEVEL JET IS NEAR THIS AREA...I DO NOT
EXPECT SEVERE WEATHER.  HAVING WRITTEN THAT...NOTE THAT WITH THE
FREEZING LEVEL NEAR 10,500FT... AND CAPES NEAR 2000 J/KG FROM THE
LAPS SOUNDINGS FROM MKG TO BIG RAPIDS AT 18Z... ISOLATED 3/4 INCH
HAIL NOT OUT OF THE QUESTION. ALL OF THIS SHOULD END BY 02Z OR SO
ONCE THE SUN HAS SET AND ALL OF THE RELATED INSTABILITY IS GONE.
THUS WILL PULL THE RISK OF SHOWERS FROM THE FORECAST OVERNIGHT.

SUNDAY THE UPPER LEVEL WILL CONTINUE TO SLOWLY DEPART FROM MICHIGAN
AS UPPER LEVEL WINDS BECOME ANTICYCLONIC.  EVEN SO...AREAS SOUTH AND
EAST OF A LINE FROM AZO TO LANSING STILL HAVE ENOUGH INSTABILITY AND
DEEP LAYER MOISTURE WITH CYCLONIC WIND FIELD TO ALLOW FOR AFTERNOON
CONVECTION AGAIN.  SO I WENT WITH AFTERNOON SHOWERS AND
THUNDERSTORMS SOUTH AND EAST OF THAT LINE.  OTHERWISE PARTLY CLOUDY.
HIGH TEMPERATURES BASED ON 1000/925MB THICKNESS FIELD FORECAST WHICH
DID VERY WELL FOR TODAY...EVEN WITH CLOUDS AROUND

SUNDAY NIGHT HIGH SKIES SHOULD BECOME MOSTLY CLEAR HAS SURFACE HIGH
AND SHORTWAVE RIDGE MOVES THROUGH SOUTHWEST MICHIGAN.

MONDAY NEXT SHORTWAVE ON NORTHERN STREAM HEADS TOWARD MICHIGAN. THE
INSTABILITY AND MOISTURE DOES NOT MOVE IN UNTIL MONDAY NIGHT. SO I
HAVE THE SHOWERS AND THUNDERSTORMS IN THAT TIME FRAME. THE SHORTWAVE
MOSTLY STAYS IN CANADA SO I DO NOT EXPECT MUCH OUT OF THIS. THERE IS
SOME JET EXIT REGION DYNAMICS THOUGH. SO THAT SHOULD HELP. EVEN SO
THE LOW LEVEL JET IS MARGINAL IF THERE AT ALL.  THUS WENT WITH 30
PCT POP AND CALLED THAT GOOD.

TUESDAY...A LOW LEVEL JET DEVELOPS OVER NEAR INTERSTATE 94 DURING
THE AFTERNOON AND THE ETA SHOWS -3 TO -4C 850MB LI AND CAPES NEAR
2500 J/KG.  HARD TO DISREGARD THAT GIVEN THE JET EXIT REGION LIFT
AND THE LOW LEVEL JET PLUS THE WARM AIR COMING IN. THUS WENT WITH
CHC POP OVER THE ENTIRE CWA. HIGHS AGAIN BASED ON THE 1000/925MB
THICKNESS TOOL THAT CONTINUES TO DO VERY NICELY THANK YOU.

.LONG TERM...
THE UPPER PATTERN DURING THE EXTENDED PERIOD WILL SLOWLY EVOLVE FROM
A ZONAL FLOW TO A TROUGH OVER THE UPPER MS VALLEY BY NEXT WEEKEND.
ON
THE SFC HIGH PRESSURE WILL DRIFT EAST OF THE CWA BY TUESDAY NIGHT.
THE NEXT COLD FRONT AND PREFRONTAL TROUGH WILL MOVE INTO THE WESTERN
LAKES WEDNESDAY NIGHT AND WELL KEEP THE MENTION OF TSRA FROM WED
AFTERNOON THROUGH THURSDAY. THE MAIN COLD FRONT WONT PUSH THROUGH
UNTIL THURSDAY NIGHT. WILL KEEP THE MENTION OF SHOWERS THU NIGHT. A
LARGE AREA OF HIGH PRESSURE THEN SINKS SOUTH FRIDAY AND SATURDAY
PRODUCING DRY WX.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...NONE.

&&

WDM 93

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1145 AM EDT SAT JUL 17 2004

MIZ037>040-043>046-050>052-056>059-064>067-071>074-181000-
ALLEGAN-BARRY-CALHOUN-CLARE-CLINTON-EATON-GRATIOT-INGHAM-IONIA-
ISABELLA-JACKSON-KALAMAZOO-KENT-LAKE-MASON-MECOSTA-MONTCALM-MUSKEGON-
NEWAYGO-OCEANA-OSCEOLA-OTTAWA-VAN BUREN-
1145 AM EDT SAT JUL 17 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST LOWER
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP WEST OF A LINE FROM
BIG RAPIDS TO GRAND RAPIDS TO BATTLE CREEK ON THE LAKE BREEZE
CONVERGENCE BOUNDARY AFTER 1 PM THIS AFTERNOON. ISOLATED
THUNDERSTORMS ARE EXPECTED ELSEWHERE.  THESE STORMS SHOULD END AS
THE SUN SETS THIS EVENING.

THESE STORMS ARE NOT EXPECTED TO BE SEVERE. EVEN SO...THE STORMS
WILL MOVE ONLY SLOWLY TO THE SOUTH AROUND 10 MPH. THE STRONGER
STORMS WILL HAVE RAINFALL RATES OVER OVER ONE INCH PER HOUR
ASSOCIATED WITH THEM. DUE TO THE SLOW MOVEMENT OF THESE STORMS...
LOCAL URBAN AND SMALL STREAM FLOODING IS ALSO POSSIBLE. PEA SIZE
HAIL WOULD NOT BE OUT OF THE QUESTION FROM SOME OF THE STRONGER
THUNDERSTORMS. FREQUENT CLOUD TO GROUND LIGHTNING IS EXPECTED WITH
THOSE STRONGER THUNDERSTORMS TOO.

.DAYS TWO THROUGH SEVEN...

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH THE PERIOD.

DUKE WDM