Flash Flood Warning 1, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
153 PM EDT MON MAY 31 2010

LATEST UPDATE...AVIATION...

.SYNOPSIS...(1231 PM EDT MON MAY 31 2010)
A COLD FRONT WILL BRING SHOWERS AND THUNDERSTORMS THIS AFTERNOON
WITH SOME HEAVY DOWNPOURS AND SMALL HAIL POSSIBLE. THE FRONT WILL
MOVE EAST TONIGHT AND FAIR WEATHER WILL RETURN FOR TUESDAY. MORE
SHOWERS AND THUNDERSTORMS ARE EXPECTED LATE WEDNESDAY INTO THURSDAY
AS LOW PRESSURE ARRIVES.

&&

.SHORT TERM...(1231 PM EDT MON MAY 31 2010)
(THIS AFTERNOON THROUGH WEDNESDAY)
MARGINAL SEVERE THREAT THIS AFTERNOON SOUTH OF INTERSTATE 96 WHERE
SOME UPDRAFTS MAY BE ABLE TO LAST LONG ENOUGH TO PRODUCE LARGE HAIL.
WIND THREAT IS MITIGATED BY ONLY 25 KTS OF SHEAR AND BY LACK OF DRY
AIR AT MID LEVELS. DO NOT EXPECT LONG LIVED ORGANIZED STORMS GIVEN
THE WEAK SHEAR. APPEARS MAIN IMPACTS WITH THESE STORMS WILL BE HEAVY
RAIN AND ISOLATED HAIL THREAT.

AS FOR TIMING...EXPECT THE FRONT TO CLEAR AZO AND GRR BY 5 PM AND
LAN AND JXN BY 00Z. DRYING AND SUBSIDENCE BEHIND THE FRONT WILL LEAD
TO RAPIDLY IMPROVING CONDITIONS TONIGHT. REST OF PREVIOUS DISCUSSION
FOLLOWS.

HIGH PRESSURE IS SOLIDLY IN PLACE FOR TUESDAY.  LOWER DEW POINTS AND
ABUNDANT SUNSHINE WILL MAKE FOR A VERY PLEASANT DAY.

SOME CHANGES HAVE OCCURRED IN THE MODEL SOLUTIONS INTO THE MID WEEK
PERIOD.  BY THIS TIME FRAME WE WILL BE IN A ZONAL FLOW AND THE
MODELS ARE STRUGGLING ON HOW TO HANDLE SHORT WAVES THAT ARE MOVING
THROUGH THIS REGIME.  IN GENERAL...THE MODELS HAVE BECOME MORE
ROBUST WITH A COLD FRONT THAT CROSSES THE AREA LATE TUESDAY NIGHT
INTO WEDNESDAY WITH MORE UPPER LEVEL SHORT WAVE SUPPORT.  WILL NOT
COMPLETE BITE ON THIS...BUT HAVE TRENDED THE FORECAST WETTER BY
ADDING POPS TO LATE TUESDAY NIGHT AND INCREASED POPS ON WEDNESDAY.
THE FRONT APPEARS TO SLOW DOWN AS IT CROSSES THE REGION.  THIS WILL
ADD TWO POTENTIAL ISSUES...HEAVIER RAINS AND ALSO THE CHANCE OF
SEVERE STORMS.  RAINFALL COULD APPROACH AN INCH...LARGELY DEPENDING
ON THE BEHAVIOR OF THE FRONT.  SEVERE POTENTIAL WOULD BE HIGHEST
OVER THE SOUTHERN CWA...SOUTH OF THE SLOW MOVING FRONT...WHERE
DAYTIME HEATING COULD LEAD TO STRONGER INSTABILITY.

&&

.LONG TERM...(409 AM EDT MON MAY 31 2010)
(WEDNESDAY NIGHT THROUGH SUNDAY)
THE CHALLENGE IS TIMING THE SHOWERS WITH EACH SHORTWAVE IN ZONAL
FLOW.

THERE WAS A LARGE STORM OVER THE CENTRAL PACIFIC JUST EAST OF THE
DATELINE SUNDAY NIGHT. THAT STORM IS EXPECTED TO MOVE SLOWLY ACROSS
THE GULF OF ALASKA INTO THE END OF THIS WEEK.  AS THAT DOES SO...IT
BUILDS THE UPSTREAM RIDGE OVER NORTH CENTRAL CANADA (NUNAVUT) THAT
LARGELY REMAINS IN PLACE THROUGH THIS COMING WEEK. THIS THEN CREATES
AN OMAGE BLOCK FROM ALASKA EASTWARD INTO EASTERN CANADA. THAT WILL
HELP MAINTAIN A ZONAL FLOW ACROSS THE NORTHERN UNITED STATES THROUGH
MOST OF THIS COMING WEEK. THE PRIMARY POLAR JET CORE WILL BE NEAR 45
NORTH... OVER THE GREAT LAKES... THROUGH A GOOD PART OF THIS COMING
WEEK.

THE PROBLEM OF COURSE IS TIMING AND DEVELOPMENT OF SHORTWAVES
MOVING THROUGH THIS ZONAL FLOW. THE MODELS DO NOT DO WELL WITH THESE
SORT OF FEATURE IN ZONAL FLOW. THE NEXT SYSTEM TO COME THROUGH THIS
AREA IS THE RESULT OF THE JET ENTRANCE REGION THAT CROSSES UPPER
MICHIGAN ON WEDNESDAY. THERE ARE MULTIPLE WAVE SEGMENTS ASSOCIATED
WITH THIS SYSTEM AND IT SEEMS THERE WILL BE TWO PERIODS OF
SHOWERS/THUNDERSTORMS.... WEDNESDAY THEN THURSDAY. THE LOCATIONS AND
TIMING OF THESE CHANGE ON EVERY MODEL RUN AND FROM MODEL TO MODEL.
THERE IS SOME POTENTIAL FOR STRONG STORMS DEPENDING ON JUST HOW THIS
ALL PLAYS OUT. CONFIDENCE FOR STRONG STORMS OVER THE GRR CWA
THURSDAY IS VERY LOW.

THERE IS ANOTHER MAJOR SYSTEM THAT COMES INTO THE WESTERN GREAT
LAKES OVER THE WEEKEND AND THAT SYSTEM HAS EVEN MORE QUESTIONS THAN
THE WED/THU SYSTEM DOES.

GIVEN THAT I DID NOT FEEL IT SERVED MUCH PURPOSE TO CHANCE THE
CURRENT GRIDS MUCH IF AT ALL. SO I MADE ONLY COSMETIC CHANGES AND
CALLED THAT GOOD.

&&

.AVIATION...(153 PM EDT MON MAY 31 2010)
AN AREA OF THUNDERSTORMS IN ASSOCIATION WITH A COLD FRONT WAS MOVING
ONSHORE ACROSS SOUTHWESTERN LOWER MICHIGAN EARLY THIS AFTERNOON. THE
LINE AS A WHOLE WILL BE MOVING EAST WHILE A FEW INDIVIDUAL
THUNDERSTORMS AHEAD OF THE LINE MAY MOVE NORTHEAST. WIND GUSTS TO 25
KTS CAN BE EXPECTED WITH THESE STORMS...BUT THAT IS SUBJECT TO
CHANGE IF THE STORMS INTENSIFY. HAIL IS POSSIBLE FOR AZO...BTL...AND
JXN WITH THESE STORMS BUT LEFT OUT THE MENTION OF THAT AND WILL
AMEND IF NECESSARY THIS AFTERNOON/EVENING. ANY THUNDERSTORM THAT
DEVELOPS MAY PRODUCE FREQUENT TO CONTINUOUS LIGHTNING...BOTH IN
CLOUD AND CLOUD TO GROUND.

MKG...GRR...AND LAN WILL ESCAPE THE BRUNT OF THE THUNDERSTORM
ACTIVITY TODAY. IFR VISBYS ARE POSSIBLE IN THE STRONGEST STORMS FOR
THE SOUTHERN TAFS GIVEN THE HEAVY RAIN THREAT. CIGS WILL LIFT AND
SKIES WILL CLEAR TONIGHT FROM NW TO SE...RETURNING ALL SITES TO VFR
CONDITIONS AS THE WINDS ALSO VEER TOWARD THE WNW. OVERNIGHT AND INTO
TUESDAY...TRANQUIL WEATHER WILL PROVIDE FOR GOOD FLYING
CONDITIONS.

&&

.MARINE...(1231 PM EDT MON MAY 31 2010)
THUNDERSTORMS WILL BE ACROSS LAKE MICHIGAN SOUTH OF WHITEHALL THIS
AFTERNOON AS A COLD FRONT MOVES THROUGH. WINDS WILL SHIFT TO THE NW
BEHIND THE FRONT BY LATE AFTERNOON AND WAVES MAY BUILD TO AROUND 3
FEET TOWARD EVENING. WINDS AND WAVES WILL DIMINISH LATER TONIGHT AND
TUESDAY WILL SEE LOWER WINDS AND WAVES.

THEN SOUTH WINDS WILL INCREASE ON THE BACK SIDE OF HIGH PRESSURE
TUESDAY NIGHT AND WAVES NEAR 4 FEET ARE POSSIBLE AROUND THE SABLE
POINTS TUESDAY NIGHT.

&&

.HYDROLOGY...(1231 PM EDT MON MAY 31 2010)
BASIN AVERAGE QPF OF A QUARTER TO HALF INCH IS POSSIBLE TODAY AS A
COLD FRONT COMES THROUGH. SOME LOCALLY HEAVY DOWNPOURS OF AN INCH OR
TWO REMAIN POSSIBLE SOUTH OF INTERSTATE 96 THIS AFTERNOON.

SOME HEAVIER RAIN IS POSSIBLE TUESDAY NIGHT AND WEDNESDAY WITH HALF
OF AN INCH TO AS MUCH AS AN INCH OF RAIN POSSIBLE AS A SLOW MOVING
FRONT COMES THROUGH.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI....NONE.
LM....NONE.

&&

SYNOPSIS:     OSTUNO
SHORT TERM:   JK/OSTUNO
LONG TERM:    WDM
AVIATION:     HOVING
MARINE:       OSTUNO
HYDROLOGY:    OSTUNO

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
527 AM EDT MON MAY 31 2010

LMZ844>849-MIZ037>040-043>046-050>052-056>059-064>067-071>074-010930-
ST JOSEPH TO SOUTH HAVEN MI-SOUTH HAVEN TO HOLLAND MI-
HOLLAND TO GRAND HAVEN MI-GRAND HAVEN TO WHITEHALL MI-
WHITEHALL TO PENTWATER MI-PENTWATER TO MANISTEE MI-MASON-LAKE-
OSCEOLA-CLARE-OCEANA-NEWAYGO-MECOSTA-ISABELLA-MUSKEGON-MONTCALM-
GRATIOT-OTTAWA-KENT-IONIA-CLINTON-ALLEGAN-BARRY-EATON-INGHAM-
VAN BUREN-KALAMAZOO-CALHOUN-JACKSON-
527 AM EDT MON MAY 31 2010

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED INTO LATE MORNING AS A COLD
FRONT MOVES INTO SOUTHWEST LOWER MICHIGAN BY LATE THIS MORNING.
THE STRONGEST STORMS COULD HAVE HAIL TO THREE QUARTERS OF AN INCH
AND WIND GUSTS TO 40 MPH AS THEY MOVE NORTHEAST AROUND 20 MPH.

BY EARLY AFTERNOON THE STORMS ARE EXPECTED TO BECOME BETTER
ORGANIZED JUST EAST OF GRAND RAPIDS...BEHIND THE COLD FRONT. THE
STRONGEST STORMS MAY APPROACH SEVERE LIMITS WITH WIND GUSTS TO NEAR
60 MPH AND HAIL TO ONE INCH. DUE TO THE SLOW MOVEMENT OF THESE
STORMS...LOCALIZED STREET FLOODING IS POSSIBLE. THE STORMS SHOULD
BE OUT OF THE AREA BY EARLY THIS EVENING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

ADDITIONAL THUNDERSTORMS ARE POSSIBLE WEDNESDAY INTO THURSDAY AS A
SERIES OF WAVES ON THE FRONT MOVE THROUGH THE AREA. SOME OF THESE
STORMS COULD BE STRONG AND PRODUCE LOCALLY HEAVY RAINFALL.

A STORM OVER THE WEEKEND COULD BRING ADDITIONAL THUNDERSTORMS TO
THE AREA.

.SPOTTER INFORMATION STATEMENT...

WHILE SPOTTER ACTIVATION IS NOT EXPECTED... PLEASE CALL IN ANY
SIGHTINGS OF HAIL OR DAMAGING WINDS.

WDM

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