FXUS63 KGRR 051436
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1035 AM EDT SUN SEP 5 2004

.UPDATED...

WE PULLED OUT THE FOG ADVISORY FROM THE FORECAST AS VISIBILITIES 
HAVE INCREASED ABOVE A 1/2MILE ACROSS THE CWA. I EXPECT THE LOW 
CLOUDS AND FOG TO BE TOTALLY GONE BY NOON.

THERE IS A SMALL AREA OF SHOWERS OVER CNTRL LAKE MICHIGAN ASSOCIATED 
WITH A SHORTWAVE MOVING EAST NORTHEAST TOWARD CNTRL LOWER MICHIGAN 
THIS AFTERNOON. LAPS...RUC AND ETA SOUNDINGS LARGELY SUGGEST A 
DECENT SUBSIDENCE INVERSIONS THIS AFTERNOON...WITH 850MB LI VALUES 
NEAR 4C.  DTX...APX AND GRB SOUNDINGS AT 12Z SHOW A SUBSTANTIAL 
SUBSIDENCE INVERSION NEAR 700MB ALREADY.  THE 700MB TO 300MB 
POSITIVE DPVA IS EAST OF GRR BY 18Z AND EAST OF THE CWA BY 21Z. THAT 
WILL INCREASE THE STRENGTH OF THE SUBSIDENCE INVERSION BEHIND IT. 
EVEN SO...THERE IS THE ISSUE OF A WEAK LAKE BREEZE AND THE DPVA OVER 
THE EASTERN CWA INTO MID AFTERNOON.  I WOULD LIKE TO BELIEVE THE 4C 
850MB LI WOULD STOP ANY CONVECTION (RUC SUGGESTING 17,000 EQL BEHIND 
THE SHORTWAVE BUT 40,000 EQL AHEAD OF IT). WANTING TO BE ON THE SAFE 
SIDE OF THINGS I WENT WITH A 20 PCT POP ACROSS THE CWA.  MORE THEN 
LIKELY THE SHOWER CLUSTER OVER LK MICHIGAN WILL DISSIPATE AS IT 
MOVES ON SHORE IN 2 HOURS AND THERE WILL BE NO CONVECTION THIS 
AFTERNOON OVER THE GRR CWA... BUT SINCE I CAN NOT TOTALLY RULE IT 
OUT WITH THE SHORTWAVE MOVING ACROSS THE CWA AND WITH SFC DEW POINTS 
NEAR 70F AND SFC TEMPS IN THE MID 80S BY 3PM... IT WOULD NOT BE OUT 
OF THE QUESTION. WHICH IS WHY I KEPT THE 20PCT POP THIS AFTERNOON.

OTHERWISE LITTLE CHANGE TO THE FORECAST. ONE COULD SAY ALL THOSE LOW 
CLOUDS WILL LIMIT THE WARMING OVER THE EASTERN CWA BUT WITH SOUTH 
WINDS I WOULD THING THE WARMER AIR WILL ADVECT IN FROM THE SOUTH 
ANYWAY SINCE THE CLOUD AREA IS ONLY A FEW COUNTIES WIDE ANYWAY.

&&

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

$$

 WDM