FXUS63 KGRR 061730
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
131 PM EDT SAT SEP 6 2008

LATEST UPDATE...AVIATION...

.SYNOPSIS...(330 AM EDT SAT SEP 6 2008)
AN UPPER LEVEL TROUGH ACROSS THE MID SECTION OF THE NATION WILL
RESULT IN A SOMEWHAT UNSETTLED WEATHER PATTERN THROUGH EARLY NEXT
WEEK. SEVERAL UPPER LEVEL DISTURBANCES WILL LEAD TO SEVERAL CHANCES
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. HOWEVER DRY
CONDITIONS WILL PREVAIL THE MAJORITY OF THE TIME THIS WEEKEND AND
OUR BEST CHANCE FOR PRECIPITATION SHOULD HOLD OFF UNTIL LATE MONDAY.

&&

.SHORT TERM...(1150 AM EDT SAT SEP 6 2008)
(TODAY THROUGH MONDAY AFTERNOON)
HAD TO EXPAND POPS SLIGHTLY FARTHER SOUTH IN AN EARLIER AMENDMENT TO
ACCOUNT FOR THE SHOWERS CURRENTLY MOVING INTO THE GRAND HAVEN AND
FERRYSBURG AREAS. POPS ARE NOW IN THE GRIDS NORTH OF A LINE FROM
ROUGHLY SOUTH HAVEN TO GRAND RAPIDS TO ALMA.

WEAK N-S ORIENTED SFC TROUGH OVER LAKE MICH (LIKELY ENHANCED BY
MORNING LAND BREEZE) HAS BEEN GENERATING A FEW ISOLATED SHOWERS THIS
MORNING BETWEEN GRAND HAVEN AND LUDINGTON. AS THIS FEATURE PUSHES TO
THE EAST... A MORE UNIFORM WEST SOUTHWEST WIND FLOW SHOULD DEVELOP
OVER THE LAKE. THIS OUGHT TO END THE SHOWER THREAT AT THE LAKESHORE
BY 18Z AND THE BETTER SFC CONVERGENCE SHOULD BE FOCUSED INLAND AFTER
18Z.


PVA ACROSS OUR ENTIRE CWFA LOOKS FAIRLY IMPRESSIVE TONIGHT.
THEREFORE WE WILL CONTINUE TO MENTION A SLIGHT CHC FOR SHOWERS
ACROSS OUR CWFA... ESPECIALLY AFTER REVIEWING 00Z GFS GUIDANCE.

GIVEN THE UPPER LEVEL PATTERN SUNDAY INTO EARLY NEXT WEEK... WE WILL
NEED TO CONTINUE TO CARRY POPS THROUGH MONDAY AFTERNOON. IT STILL
APPEARS THAT POPS WILL INCREASE GRADUALLY... PARTICULARLY LATE
MONDAY AS THE PRIMARY SHORTWAVE MOVES IN. HOWEVER TIMING SHORTWAVES
IN THIS TYPE PATTERN IS TRICKY... AND POPS WILL REMAIN NECESSARY
SUNDAY THROUGH MONDAY.

IT SHOULD BE STRESSED THAT DRY CONDITIONS WILL PREVAIL THE MAJORITY
OF THE TIME THIS WEEKEND. OUR BEST CHC FOR RAIN SHOULD HOLD OFF
UNTIL LATE MONDAY.

&&

.LONG TERM...(330 AM EDT SAT SEP 6 2008)
(MONDAY NIGHT THROUGH FRIDAY)

NO SIGNIFICANT CHANGES TO THE EXTENDED PERIOD. THERE IS GENERALLY
GOOD MODEL AGREEMENT ON EVOLUTION OF A SHORTWAVE TROUGH EARLY IN THE
WEEK. WILL KEEP CHANCE POPS MONDAY NIGHT WITH DEEPER MOISTURE AND
PRECIP DEPARTING TO THE EAST BY 12Z TUESDAY. SFC HIGH BUILDS IN WITH
FAIR WEATHER FOR TUESDAY AND WEDNESDAY. DROPPED POPS FOR WEDNESDAY
NIGHT AS IT APPEARS RETURN MOISTURE AND OVERRUNNING SHOWERS WILL NOT
ARRIVE UNTIL AFTER 12Z THURSDAY. LOOKS LIKE A WIDESPREAD RAIN EVENT
FOR THURSDAY OR FRIDAY AS SHORTWAVE TROUGH AND SFC LOW ARRIVE WITH
TRAILING COLD FRONT PUSHING THROUGH BY THE END OF THE EXTENDED
PERIOD.

&&

.MARINE...(1150 AM EDT SAT SEP 6 2008)
THE POSSIBILITY OF WATERSPOUTS WAS DISCUSSED THIS MORNING AS THE
CUMULUS OVER THE LAKE ON VIS SATELLITE HAD A SIMILAR APPEARANCE TO
THE EVENT ABOUT A MONTH AGO. HOWEVER LIMITING FACTORS ARE THAT LK MI
SFC WATERS TEMPS ARE IN THE MID 40S TO MID 50S IN THE VICINITY OF
THE SHOWERS AND THE DEPTH OF THE CONVECTIVE LAYER IS RELATIVELY
SHALLOW.

&&

.AVIATION...(131 PM EDT SAT SEP 6 2008)
SHOWERS WILL DIMINISH ACROSS THE NRN CWA THIS AFTERNOON. MUCH OF THE
CWA WILL SEE SCT CU THIS AFTERNOON. AN UPPER LOW WILL MOVE ACROSS
THE REGION LATE TONIGHT AND EARLY SUNDAY. THIS MAY GENERATE SHOWERS
ACROSS THE CWA. TAF SITES SHOULD REMAIN VFR.

&&

.HYDROLOGY...(330 AM EDT SAT SEP 6 2008)
RAINFALL AMOUNTS THIS WEEKEND WILL AVERAGE BELOW ONE HALF INCH AND
RAIN WILL BE SCATTERED IN COVERAGE. THIS SHOULD HAVE LITTLE TO NO
IMPACT ON THE CURRENT HYDRO SITUATION.

&&

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

&&

$$

SYNOPSIS: LAURENS
SHORT TERM: LAURENS/MEADE
LONG TERM: OSTUNO
MARINE: MEADE
AVIATION: 93
HYDROLOGY: LAURENS








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