Special Weather Statement, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
715 AM EDT THU AUG 7 2008

LATEST UPDATE...AVIATION AND SHORT TERM...

.SYNOPSIS...(358 AM EDT THU AUG 7 2008)
ANOTHER UPPER LEVEL DISTURBANCE WILL MOVE ACROSS MICHIGAN TODAY.
THIS WILL TRIGGER WIDELY SCATTERED THUNDERSTORMS...MOST LIKELY
INLAND FROM LAKE MICHIGAN TOWARD MID DAY INTO THE EARLY EVENING
HOURS.  HIGH PRESSURE WILL THEN BUILD INTO THE REGION TONIGHT AND
FRIDAY LEADING TO DRY WEATHER WITH TEMPERATURES A BIT BELOW NORMAL.
THE HIGH BEGINS TO SLIP TO THE SOUTH BY FRIDAY NIGHT AND SATURDAY.
THIS ALLOWS ANOTHER UPPER LEVEL DISTURBANCE TO MOVE IN THE AREA.
THIS WILL RESULT IN PARTLY CLOUDY SKIES WITH AN ISOLATED CHANCE OF
SHOWERS OR STORMS.

&&

.SHORT TERM...(715 AM EDT THU AUG 7 2008)
(TODAY THROUGH SATURDAY)
I ADDED THUNDERSTORMS TO THE EARLY MORNING PART OF THE FORECAST
SINCE THERE IS AN AREA OF THUNDERSTORMS DROPPING SOUTHEAST WEST OF
US-131 NORTH OF CADILLAC. THESE ARE ASSOCIATED WITH THAT SHORTWAVE
DROPPING SOUTH ACROSS NORTHERN LOWER MICHIGAN AT THIS TIME. IT SHOWS
NICELY ON THE WATER VAPOR LOOPS.

PREVIOUS DISCUSSION...WE REMAIN IN NORTHWEST FLOW THROUGH THE SHORT
TERM AND THE PATTERN OF PERIODIC SHORT WAVES COMING THROUGH IN THIS
MEAN FLOW WILL ALSO PERSIST.

THE FIRST SUCH SHORT WAVE WAS OVER THE MN ARROWHEAD REGION THIS
MORNING AND DROPPING SE.  THE TIMING ON THIS WAVE ACROSS SW LOWER
MICHIGAN WILL NOT BE AS FAVORABLE AS LAST EVENING/S WAVE WAS.  THIS
WAVE WILL ARRIVE EARLIER IN THE DAY RESULTING IN A QUICKER INCREASE
IN CLOUD COVER AND THEREFORE LESS INSTABILITY TO WORK WITH.  THERE
WAS ACTUALLY VERY LITTLE CLOUD COVER WITH THIS FEATURE THIS
MORNING...HOWEVER THE MID AND LOW LEVEL MOISTURE WAS RATHER ROBUST
AND WE WILL SEE A RAPID DIURNAL CLOUD DEVELOPMENT BY LATE MORNING.
SHOWER/STORM DEVELOPMENT SHOULD BE SOMEWHAT LIMITED DUE TO THE WEAK
INSTABILITY...HOWEVER THE BEST CHANCE OF SEEING SOME PCPN WILL OCCUR
INLAND WHERE THE BEST INSTABILITY SHOULD BE REALIZED.

DRIER AIR SLOWLY MOVES INTO THE WESTERN CWA THIS EVENING AS THE
SHORT WAVE DEPARTS...SO WILL KEEP THE DRY FORECAST GOING THERE.
HOWEVER A SERIES OF WEAK VORT MAXES CASCADE ACROSS THE EASTERN
PORTION OF THE STATE OVERNIGHT WHICH COULD RESULT IN LINGER CLOUD
COVER AS WELL AS ISOLATED SHOWERS/STORMS FOR THE EASTERN GRR CWA
COUNTIES.

WE WILL BE ON THE BACKSIDE ON THE SHORT WAVE BY FRIDAY WITH NVA AND
SURFACE RIDGING GRADUALLY WORKING IN.  HAVE REMOVED POPS ACROSS MUCH
OF THE CWA...HOWEVER WILL LEAVE A SMALL POP IN THE EASTERN COUNTIES
IN CASE THE WAVE IS DELAYED A BIT.  THIS IS SUGGESTED BY THE GFS AND
NGM AS THE UPPER TROUGH ACROSS EASTERN CANADA SHARPENS A BIT.

I HAVE ADDED SLIGHT CHANCE POPS TO THE NORTHERN CWA FRIDAY NIGHT AND
CWA-WIDE SATURDAY AS THE PATTERN OF NORTHWEST FLOW SHORT WAVES
CONTINUES.  THERE IS STILL A DEGREE OF UNCERTAINTY IN THIS...BUT THE
SURFACE HIGH WEAKENS AND SLIPS SOUTH BY THIS TIME FRAME.  ALSO THE
EVOLUTION OF THE EASTERN CANADIAN TROUGH/UPPER LOW WILL DICTATE THE
POSITION/MOVEMENT OF ANY SHORT WAVES ON IT/S WESTERN EDGE.

&&

.LONG TERM...(358 AM EDT THU AUG 7 2008)
(SATURDAY NIGHT THROUGH WEDNESDAY)
I MADE ONLY MINOR CHANGES TO OUR ON GOING FORECAST THIS MORNING.
MOSTLY THIS WAS BECAUSE I HAVE VERY LOW CONFIDENCE IN THE CURRENT
MODEL SOLUTIONS BEYOND SUNDAY. THE MODELS CONTINUE TO SHOW
SIGNIFICANT DIFFERENCES BEYOND THE SUNDAY TIME FRAME. TO SOME EXTENT
THE GFS HAS GRADUALLY LEANED TOWARD THE ECMWF FOR THE SOUTHERN
STREAM POSITION IN THE MONDAY THROUGH WEDNESDAY TIME FRAME. THAT
WOULD IMPLY THE EASTERN TROUGH WILL BE NUDGED OUT MORE QUICKLY. IN
ANY EVENT...A WARMING TREND SEEMS LIKELY EARLY NEXT WEEK DUE TO
RISING HEIGHTS.

ON A LARGER SCALE...THERE IS THE ISSUE OF THAT STORM FROM CENTRAL
ASIA THAT MOVES TO THE DATE LINE BY NEXT WEDNESDAY.  WHILE THIS MAY
SEEM UNIMPORTANT TO WEST MICHIGAN WEATHER THE TRUTH IS JUST ABOUT
ALL THE MODELS SHOW THIS STORM BECOMING THE LARGEST SYSTEM IN THE
NORTHERN HEMISPHERE BY WEDNESDAY.  THE UPPER LEVEL CYCLONIC FLOW
COVERS FROM THE COAST OF ALASKA TO THE KAMCHATKA PENINSULA  WITH A
SYSTEM THAT HUGE... IT WILL INFLUENCE THE DOWNSTREAM WAVE PATTERN
THROUGH ROSSY WAVE DISPERSION. MORE THAN LIKELY THIS WOULD MEAN
A LESS MERIDIONAL FLOW PATTERN OVER THE CENTRAL AND NORTHERN UNITED
STATES BY THE MIDDLE OF NEXT WEEK. WHICH MEANS THE SOUTHERN STREAM
WOULD BE ABLE TO GET FARTHER NORTH AGAIN. THE ECMWF CONTINUES
TO FORECAST A TROPICAL LOOKING SYSTEM PASSING JUST SOUTH OF
MICHIGAN IN THE TUESDAY TIME FRAME...FOR 3 DAYS NOW. THIS SEEMS
OVER DONE AND TOO FAST. HOWEVER MAYBE THAT DOES NOT MATTER TO OUR
POP FOR THAT TIME FRAME. THE FRONT BETWEEN THE POLAR AIR TO THE
NORTH AND SUBTROPICAL AIR TO THE SOUTH WOULD LIKELY BE OVER LOWER
MICHIGAN DURING THE TUESDAY THROUGH THURSDAY TIME FRAME DUE TO THAT
HUGE SYSTEM FROM ASIA MOVING TO THE DATELINE. THIS WOULD MEAN
PERIODS OF THUNDERSTORMS AS WAVES MOVE ALONG THE FRONT. THUS I AM
NOT BUYING THE IDEA OF A DRY FORECAST FOR THE MID WEEK PERIOD...FOR
THE GRR CWA.  THE ENSEMBLES OF THE GFS FROM THE 07TH AT 00Z SHOW
THIS NICELY WITH A 35 TO 40 PCT CHANCE OF MORE THAN A TENTH OF AN
INCH OF QPF BETWEEN 12Z TUESDAY AND 00Z WEDNESDAY. TIMING THE WAVES
WILL BE TRICKY...SO I DID NOT CHANCE THE POP AND WEATHER GRID MUCH
BUT I BELIEVE WE WILL MORE THAN LIKELY SEE SHOWERS TUE THROUGH THU
DUE TO A STATIONARY FRONT NEAR LOWER MICHIGAN.

SATURDAY NIGHT INTO MONDAY WILL SEE FAIR SKIES AND PLEASANT
TEMPERATURES AS THE POLAR JET RETREATS NORTHEAST OF LOWER MICHIGAN
IN THAT TIME FRAME.

&&

.MARINE...(358 AM EDT THU AUG 7 2008)
WILL HOLD OFF ON ISSUING ANY SMALL CRAFT ADVISORY AT THIS POINT.
NORTHWEST FLOW AND COLD ADVECTION WILL CAUSE A CHOPPY LAKE TODAY
THROUGH FRIDAY...ESPECIALLY SOUTH OF GRAND HAVEN AND NEAR THE BIG
AND LITTLE SABLE POINTS.  EXPECTING WAVES MOSTLY IN THE 2-4 FOOT
RANGE.  WINDS AND WAVES SHOULD BE SUBSIDING BY LATE FRIDAY AFTERNOON
AS HIGH PRESSURE MOVES IN.

&&

.AVIATION...(715 AM EDT THU AUG 7 2008)
ONCE THE FOG BURNS OFF...LIKELY BY 10 AM... VFR CONDITIONS SHOULD
PREVAIL THROUGH TONIGHT. THERE WILL BE SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WILL LEAD THE SHORTWAVE SOUTH THIS MORNING
INTO EARLY THIS AFTERNOON. ONCE THAT IS THROUGH SUBSIDENCE BEHIND
THE SHORTWAVE SHOULD CLEAR THE SKY. I EXPECT MOSTLY CLEAR SKIES
TONIGHT.

&&

.HYDROLOGY...(358 AM EDT THU AUG 7 2008)
SHOWERS AND STORMS THROUGH THE SHORT TERM WILL BE ISOLATED TO WIDELY
SCATTERED WITH MINIMAL HYDRO IMPACT.

&&

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

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1150 AM EDT THU AUG 7 2008

MIZ037>040-043>046-050>052-056>059-064>067-071>074-080915-
MASON-LAKE-OSCEOLA-CLARE-OCEANA-NEWAYGO-MECOSTA-ISABELLA-MUSKEGON-
MONTCALM-GRATIOT-OTTAWA-KENT-IONIA-CLINTON-ALLEGAN-BARRY-EATON-
INGHAM-VAN BUREN-KALAMAZOO-CALHOUN-JACKSON-
1150 AM EDT THU AUG 7 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS ARE POSSIBLE EARLY THIS AFTERNOON NEAR AND
SOUTH OF GRAND HAVEN AND SEVERAL WATERSPOUTS HAVE BEEN REPORTED IN
ASSOCIATION WITH THIS ACTIVITY.

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP EAST OF ROUTE 131
BY EARLY AFTERNOON AND CONTINUE INTO THE EARLY EVENING. WHILE NONE
OF THESE STORMS ARE EXPECTED TO BE SEVERE... GUSTY WINDS...SMALL
HAIL AND BRIEF DOWNPOURS WILL ACCOMPANY THE STRONGER STORMS.STORMS
WILL MOVE SOUTHEAST AROUND 35 MPH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A FEW NON SEVERE THUNDERSTORMS ARE EXPECTED TO REDEVELOP LATER
FRIDAY AFTERNOON AND CONTINUE INTO SATURDAY. FOR THE MOST PART
THEY WILL BE EAST OF ROUTE 131.

THE RETURN OF WARMER AND MORE HUMID AIR WILL TOUCH OFF ADDITIONAL
THUNDERSTORMS MONDAY NIGHT THROUGH WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED.

LMZ844>849-080915-
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-
1150 AM EDT THU AUG 7 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

WATERSPOUTS ARE POSSIBLE THIS AFTERNOON PRIMARILY NEAR AND SOUTH OF
GRAND HAVEN. WAVES WILL BUILD TO 3 TO 5 FEET NORTH OF GRAND HAVEN BY
EVENING. WAVES OF THAT HEIGHT ARE HAZARDOUS TO SMALL WATER CRAFT AND
ALSO CAUSE RIP CURRENTS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

WINDS AND WAVES COULD WILL BE HAZARDOUS TO SMALL CRAFT FRIDAY.
RIP CURRENTS ARE ALSO POSSIBLE.

SCATTERED THUNDERSTORMS WILL RETURN MONDAY NIGHT THROUGH
WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED.

LAURENS

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