FXUS63 KGRR 201147
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
745 AM EDT SAT SEP 20 2008
LATEST UPDATE...AVIATION...
.SYNOPSIS...(345 AM EDT SAT SEP 20 2008)
A COLD FRONT WILL DROP SOUTH SOUTHEAST ACROSS LOWER MICHIGAN TODAY. 
HOWEVER MOISTURE WITH THIS SYSTEM IS VERY LIMITED AND THERE IS JUST 
A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM THIS AFTERNOON AND 
EVENING NORTHEAST OF GRAND RAPIDS. BEHIND THE COLD FRONT A LARGE 
HIGH PRESSURE RIDGE WILL BUILD IN TO OUR EAST NORTHEAST AND PRODUCE 
FAIR WEATHER SUNDAY AND MONDAY. 
&&
.SHORT TERM...(345 AM EDT SAT SEP 20 2008)
(TODAY THROUGH MONDAY AFTERNOON)
THERE IS JUST A SLIGHT CHC OF A SHOWER OR TSTORM THIS AFTN AND EARLY 
EVE... PRIMARILY OVER OUR NE CWFA IN AN AREA OF (RELATIVELY) 
SLIGHTLY HIGHER 925-850 MB MEAN RH AND WEAK PVA. 00Z GFS GUIDANCE 
CONTINUES TO INDICATE SOME INSTABILITY WILL DEVELOP THIS AFTN WITH 
LI/S DOWN TO -4 AND SB CAPES REACHING 1000 J/KG. HOWEVER FCST 
SOUNDINGS ARE QUITE DRY AND STRONGER PVA PASSES NORTH OF OUR CWFA. 
THEREFORE WE EXPECT DRY CONDITIONS WILL PREVAIL ACROSS THE VAST 
MAJORITY OF OUR CWFA. MAX TEMPS WILL REACH THE 70S.  
CANADIAN HIGH PRESSURE WILL PRODUCE DRY WX SUNDAY AND MONDAY. THERE 
REALLY ISN/T MUCH OF A PUSH OF COOLER AIR TO SPEAK OF BEHIND THE 
COLD FRONT. TEMPS WILL BE SLIGHTLY COOLER BUT STILL NEAR NORMAL 
SUNDAY... AND WILL AVG SLIGHTLY ABOVE NORMAL MONDAY WITH LARGE 
DIURNALS ANTICIPATED WITH MOSTLY CLEAR SKIES AND THE DRY AIRMASS IN 
PLACE.  
&&
.LONG TERM...(345 AM EDT SAT SEP 20 2008)
(MONDAY NIGHT THROUGH FRIDAY)
HIGH PRESSURE WILL BE IN PLACE BOTH AT THE SURFACE AND ALOFT TO 
BEGIN THE LONG TERM PERIOD MONDAY NIGHT. RIDGING WILL HANG ON INTO 
TUESDAY NIGHT PROVIDING DRY WEATHER THE FIRST FEW PERIODS OF THE 
LONG TERM FORECAST.
WEDNESDAY IS WHERE SOME DIFFERENCES BEGIN TO POP UP. LATEST MODEL 
RUNS INDICATE SHORTWAVE ACTIVITY TRYING TO PUSH INTO THE MEAN RIDGE 
POSITION OVER THE GREAT LAKES. AT THE SURFACE A COLD FRONT TRIES TO 
PUSH INTO THE RIDGE AS WELL ON WEDNESDAY. AT THIS POINT DID NOT ADD 
POPS. WOULD LIKE TO SEE SOME CONSISTENCY WITH THIS FEATURE BEFORE 
ADDING POPS. 
CURRENTLY POPS ARE IN THE FORECAST FROM THURSDAY INTO FRIDAY UNDER 
THE ASSUMPTION THAT THE FRONT WOULD BE COMING THROUGH DURING THIS 
TIME FRAME. LATEST RUNS NOW HAVE RIDGING IN PLACE MUCH OF THIS TIME 
FRAME WITH THE EARLIER FRONTAL PASSAGE. AGAIN...GIVEN MODEL 
VARIABILITY NOT MAKING CHANGES IN THE WED-FRI TIME FRAME YET. 
TEMPERATURES SHOULD BE NEAR TO ABOVE NORMAL THROUGH THE PERIOD.
&&
.MARINE...(345 AM EDT SAT SEP 20 2008)
WINDS WILL GRADUALLY VEER TO THE NW AND EVENTUALLY NORTHEAST BEHIND 
THE COLD FRONT. DESPITE THE MODEST COLD AIR ADVECTION... THE 
OFFSHORE COMPONENT SHOULD RESULT IN HIGHER WAVES BEING MAINLY WEST 
OF OUR NSH AREA OF RESPONSIBILITY. HOWEVER SOME 3 TO POTENTIALLY 4 
FOOTERS COULD AFFECT BIG AND LITTLE SABLE POINTS FOR A WHILE THIS 
AFTN AND EVE WHEN WINDS ARE NORTHERLY. 
&&
.AVIATION...(745 AM EDT SAT SEP 20 2008)
SOME LIGHT FOG EXISTS IN SPOTS ACROSS THE GRR FORECAST AREA. THIS 
FOG SHOULD BURN OFF QUICKLY...BY 14Z. SOME SCATTERED CUMULUS 
DEVEOPMENT IS POSSIBLE TODAY...UP AROUND 5000FT. ABOVE THAT...CIRRUS 
LEVEL MOISTURE UP AROUND 20000-25000FT SHOULD BE PREVALENT. A COLD 
FRONT IS DROPPING SOUTH FROM THE UPPER PENINSULA THIS MORNING AND 
SHOULD MOVE INTO SOUTHWEST LOWER MICHIGAN THIS AFTERNOON. A FEW 
THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON AND EVENING ACROSS 
CENTRAL LOWER MICHIGAN UP TOWARD KMOP...BUT THEY SHOULD STAY NORTH 
OF THE TAF SITES. THE FRONT WILL SLIP SOUTH TONIGHT...BRINGING IN 
SLIGHTLY COOLER AIR ALONG WITH THE THREAT OF SOME FOG AND LOW 
CLOUDS. BROUGHT SOME MVFR CEILINGS INTO KLAN OVERNIGHT...AND SOME 
MVFR FOG AT MOST OTHER SITES. THE THREAT FOR LOWER CEILINGS AND FOG 
BEHIND THE FRONT OVERNIGHT IS THE MAIN ISSUE IN THESE TAFS AND WILL 
CONTINUE TO BE MONITORED.
&&
.HYDROLOGY...(345 AM EDT SAT SEP 20 2008)
VERY LITTLE IF ANY RAINFALL THROUGH THE UPCOMING WEEK WILL CONTINUE 
TO BE VERY CONDUCIVE TO A GRADUAL LOWERING IN RIVER LEVELS ACROSS 
OUR HSA. ONLY THREE SITES ON THE KALAMAZOO RIVER ARE STILL ABOVE 
FLOOD STAGE AND THEY CONTINUE TO SHOW WATER LEVELS ON THE DECLINE. 
COMSTOCK PARK ON THE GRAND RIVER SHOWS A SLOW RISE AND IS EXPECTED 
TO PEAK LATER TODAY JUST A LITTLE BELOW FLOOD STAGE. 
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&
$$
SYNOPSIS:     LAURENS
SHORT TERM:   LAURENS
LONG TERM:    DUKE
MARINE:       LAURENS
AVIATION:     DUKE 
HYDROLOGY:    IOD/LAURENS