FXUS63 KGRR 071920
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
316 PM EDT TUE SEP 7 2004

.SHORT TERM...
A RATHER QUIET WEATHER PERIOD FOR THE NEXT FEW DAYS. THE MAIN 
QUESTION IS TOWARD THE WEEKEND.  SEEMS THE POLAR FRONT COMES IN 
FASTER THAN WAS FORECAST BY THE MODELS YESTERDAY. OF LESS 
SIGNIFICANCE BUT STILL WORTH MENTIONING IS THE QUESTION OF HOW COLD 
IT WILL GET TONIGHT? THE 1000/925MB THICKNESS FIELD IS FORECAST TO 
GET AS COLD HAS IT HAS BEEN SINCE MID AUGUST. THEN THOUGH IT WAS 
DENSELY OVERCAST FOR A WEEK. SO...CAN WE SEE LOWS WELL DOWN INTO THE 
40S TONIGHT?  THAT IS THE SECOND SIGNIFICANT QUESTION FOR THIS 
FORECAST CYCLE. A THRID QUESTION IS WELL WE SEE ANY CLOUDS FROM THE 
REMAINS OF FRANCES AS IT PASSES TO OUR EAST WEDNESDAY INTO THURSDAY?

MODELS ARE LARGELY IN AGREEMENT ON THE OVERALL PICTURE. THAT IS THE 
REMAINS OF FRANCES PASS SOUTH AND EAST OF THE GRR CWA WEDNESDAY INTO 
THURSDAY. MEANWHILE A POLAR HIGH FROM ALBERTA INTO EASTERN NEBRASKA 
THIS AFTERNOON WILL MOVE EAST NORTHEAST TO SOUTHERN ONTARIO 
WEDNESDAY AS THE REMAINS OF FRANCES PASS NORTHEAST ACROSS WEST 
VIRGINIA. THURSDAY THE REMAINS OF FRANCES MOVES OVER WRN PA WHILE A 
SURFACE RIDGE BUILDS INTO LOWER MICHIGAN. ON FRIDAY THE NEXT SYSTEM 
ON THE PRIMARY POLAR JET MOVES INTO THE NORTHERN PLAINS. THAT 
DISPLACES THE SURFACE HIGH EAST TO PA WHICH PUTS SOUTHWEST MICHIGAN 
INTO A RETURN FLOW OF WARMER BUT STILL DRY AIR. 

TONIGHT...WITH HIGH PRESSURE AROUND...ONLY OPEN CELL CU IN THE 
AFTERNOON WITH 18Z SURFACE DEW POINTS FROM THE MID 40S TO LOWER 50S 
IT WOULD SEEM SKIES SHOULD CLEAR TONIGHT. IF NOT FOR THE 20 TO 25KT 
WINDS FORECAST TO DEVELOP NEAR 1000FT ONCE THE BOUNDARY LAYER 
DECOUPLES...LOWS WOULD PLUNGE INTO THE UPPER 30S TO MID 40S NORTH 
AND MID 40S TO NEAR 50 SOUTH TONIGHT. HOWEVER...THAT 20KT WIND WILL 
KEEP LOWS MOSTLY 50 TO 55 SOUTH AND 45 TO 50 NORTH. 

WEDNESDAY INTO THURSDAY THE REMAINS OF FRANCES PASS OFF TO THE EAST 
OF THE GRR CWA. MODELS SUGGEST SOME LOW LEVEL MOISTURE. THE ETA 
SHOWS THE 1000/850MB MEAN RH OVER 80PCT EAST OF GRR FROM 09/00Z TO 
09/12Z. THAT WOULD SUGGEST THE POSSIBLY OF BROKEN LOW CLOUDS AROUND. 
OTHERWISE THE 1000/850MB AND 1000/925MB THICKNESS FIELDS SUGGEST A 
SLOW WARMING TRENDS.  

ON FRIDAY WITH THE HIGH MOVING OFF TO THE EAST WARMING REALLY GETS 
UNDERWAY...THICKNESS FIELDS SUGGEST HIGHS COULD GET CLOSE TO 80F. 
NOT MUCH IN THE WAY OF CLOUDS...POSSIBLY SOME WARM ADVECTION CLOUDS 
THURSDAY NIGHT INTO FRIDAY NIGHT (MORE NORTH THAN SOUTH). 

.LONG TERM...
LATEST MEDIUM RANGE GUIDANCE SHOWS A SFC HIGH PRESSURE RIDGE WILL 
CONTINUE TO DOMINATE OUR WX FRIDAY NIGHT AND PRODUCE DRY WX WITH 
CLEAR TO PARTLY CLOUDY SKIES. LATEST MEDIUM RANGE GUIDANCE (GFS, 
ECMWF) CONTINUES TO TREND A BIT FASTER WITH THE FRONT FOR THIS 
WEEKEND AND NOW SHOWS IT WILL COME THROUGH SATURDAY NIGHT. BASED ON 
THIS FASTER FRONTAL TIMING TREND THAT WAS ALSO NOTED BY THE MID 
SHIFT IN THE 00Z GUIDANCE, WE BELIEVE A FEW TSTORMS COULD DEVELOP 
ACROSS OUR FAR NORTHERN CWA SATURDAY AFTERNOON AND OVER OUR ENTIRE 
CWA SATURDAY NIGHT.  

WE'LL GO WITH A DRY FORECAST FOR SUNDAY DUE TO THE FASTER FRONTAL 
TIMING. ANOTHER SFC HIGH PRESSURE RIDGE WILL BUILD IN BEHIND THAT 
FRONT AND PRODUCE CLEAR TO PARTLY CLOUDY SKIES WITH NEAR NORMAL 
TEMPS EARLY NEXT WEEK. 

&&

.GRR WATCHES/WARNINGS/ADVISORIES...NONE.

$$

WDM LAURENS