000
FXUS63 KGRR 051730
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
131 PM EDT FRI SEP 5 2008

LATEST UPDATE...AVIATION...

.SYNOPSIS...(345 AM EDT THU SEP 4 2008)
CLOUDS AND SHOWERS WILL LINGER INTO THE MORNING HOURS TODAY.
IT WILL BECOME PARTLY SUNNY LATER THIS AFTERNOON WITH DRY WEATHER
ANTICIPATED TONIGHT. ISOLATED TO SCATTERED SHOWERS WILL IMPACT OUR
REGION THIS WEEKEND AS SEVERAL UPPER LEVEL DISTURBANCES OVER THE
NORTHERN PLAINS MOVE EAST.

&&

.SHORT TERM...(345 AM EDT THU SEP 4 2008)
(TODAY THROUGH SUNDAY AFTERNOON)

STEADY RAIN WILL GRADUALLY END DURING THE EARLY TO MID MORNING HRS
BUT A FEW LIGHTER SHOWERS WILL LINGER THROUGH MID TO LATE MORNING
BEFORE COMING TO AN END BY AROUND 16Z. LOW CLOUDS WILL LINGER
THROUGH EARLY TO MID AFTN IN CYCLONIC LOW AS INDICATED BY TIME
HEIGHT RH PROGS. HOWEVER SKIES WILL BECOME PARTLY SUNNY MID TO LATE
THIS AFTN AS DRIER AIR ADVECTS IN. SFC RIDGING WILL RESULT IN A
CONTINUATION OF DECREASING CLOUD COVER TONIGHT.

THE H5 LONGWAVE TROUGH OVER THE NORTHERN PLAINS WILL SHIFT EAST
INTO SATURDAY. MOISTURE IS SOMEWHAT LIMITED BUT WE AGREE WITH THE
PREVIOUS SHIFT IN GOING WITH LOW POPS FOR OUR NORTHERN CWFA
SATURDAY. THIS IN AN AREA OF WEAK PVA AND RELATIVELY HIGHER 925-850
MB MEAN RH.

NUMERICAL MODEL GUIDANCE CARRIES RATHER LOW POPS SUNDAY BUT WE FEEL
A (RELATIVELY) BETTER CHC FOR SHOWERS WILL COME AT THAT TIME FOR
MOST OF OUR CWFA AS STRONGER PVA DEVELOPS. THE LONGWAVE H5 TROF WILL
STILL BE ENTRENCHED ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST.
HOWEVER IT SHOULD BE STRESSED THAT EVEN ON SUNDAY MOST OF THE DAY
WILL BE DRY AND QPF AMOUNTS WILL BE LIGHT.

&&

.LONG TERM...(345 AM EDT FRI SEP 5 2008)
(SUNDAY NIGHT THROUGH THURSDAY)

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 SUNDAY NIGHT THROUGH 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. SOME
RETURN MOISTURE AND OVERRUNNING SHOWERS EXPECTED WEDNESDAY NIGHT AND
THURSDAY.

&&

.MARINE...(345 AM EDT FRI SEP 5 2008)
LOW LEVEL WIND FIELDS WILL VEER TO THE NW TO N TODAY BEHIND THE LOW.
BASED ON FAIRLY STRONG FLOW VEERING NW TO N AND 00Z GLERL WAVE MODEL
GUIDANCE WHICH BUILDS WAVES INTO THE 3 TO 5 FOOT RANGE... WE HAVE
DECIDED TO HOIST A SCA FOR ALL OF OUR NSH ZONES THROUGH 22Z TODAY.

WAVE HEIGHTS WILL DIMINISH TONIGHT AS WIND SPEEDS DECREASE.

&&

.AVIATION...(131 PM EDT FRI SEP 5 2008)
LOOK FOR IMPROVING CIGS ACROSS THE TAF SITES THROUGH THE AFTERNOON.
VFR CONDITIONS WILL SPREAD FROM NW TO SE. VISIBLE SATELLITE IMAGERY
SHOWS A CLEARING LINE CURRENTLY EXTENDING FROM NEAR CADILLAC SW TO
GRAND HAVEN MOVING STEADILY SE. SKIES WILL SCATTER OUT AROUND
SUNSET. VFR CONDITIONS THEN EXPECTED THROUGH 18Z SAT.

&&

.HYDROLOGY...(345 AM EDT FRI SEP 5 2008)
AS ANTICIPATED... NUMEROUS LOCATIONS ACROSS OUR WESTERN HSA HAVE
RECEIVED TWO TO THREE INCHES OF RAINFALL SINCE IT BEGAN YESTERDAY...
WITH A FEW LOCALLY HIGHER AMOUNTS PARTICULARLY FROM GRR WNW TO MKG.

HOWEVER GIVEN THE LONG DURATION OF RAINFALL... AND LACK OF HIGHER
RAINFALL AMOUNTS IN A SHORTER TIME PERIOD... HYDRO ISSUES SHOULD
REMAIN MAINLY CONFINED TO THE URBAN AND SMALL STREAM VARIETY.

IN THE AREAS THAT RECEIVED THE MOST RAINFALL... THE WORST CASE
SCENARIO REMAINS THAT A FEW RIVER FCST POINTS COULD REACH ACTION
STAGE DURING THE NEXT 2-3 DAYS. HOWEVER RIVERS SHOULD NOT REACH OR
EXCEED FLOOD STAGE.

IN FACT THIS HAS COME AS VERY WELCOME AND BENEFICIAL RAINFALL TO
MOST FOLKS ACROSS OUR HSA... WITH NO WORD OF ANY SIGNIFICANT HYDRO
ISSUES THUS FAR. QPF AMOUNTS WITH SHOWERS THIS WEEKEND WILL BE QUITE
LIGHT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SCA ST. JOSEPH TO MANISTEE THROUGH 22Z TODAY.

&&

$$

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