[LeArc] Forecast Discussion : MLI@ 8/2/2003 3:43:15 AM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 020840 AAA
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
340 AM CDT SAT AUG 2 2003

UPPER LOW CONTINUES TO SPIN OVER SOUTHWEST ONTARIO WITH RESULTING 
CYCLONIC FLOW OVER CWA KEEPING LOW THUNDERSTORM POPS OVER AREA 
THROUGH WEEKEND AS EMBEDDED WAVES TRAVERSE THE AREA. EARLY THIS 
MORNING... THREE SHORTWAVE WERE EVIDENT ON WATER VAPOR IMAGERY. ONE 
WAS OVER NORTHWEST IL...THE SECOND PUSHING INTO NORTHWEST IA...AND A 
THIRD IN NORTH DAKOTA. THE WAVE MOVING INTO IA WAS INTERACTING WITH 
A SURFACE BOUNDARY TO PRODUCE THUNDERSTORMS IN SOUTHWEST IA. THIS 
BOUNDARY EXTENDED FROM NEB PANHANDLE EAST ALONG IA/MO 
BORDER...CURVING NORTHEAST TO WEAK LOW OVER LAKE MI. IT APPEARED TO 
BE MORE CLOSELY ASSOCIATED WITH THE FRONT AT H85. AREA 88DS SHOW 
OCCASIONAL THUNDERSTORMS ALONG AND SOUTH OF THIS BOUNDARY ACROSS 
NORTHERN MO INTO WEST CENTRAL IL. MAIN SYNOPTIC STATIONARY FRONT WAS 
FURTHER SOUTH WITH MORE WIDESPREAD ORGANIZED THUNDERSTORM COMPLEXES 
REMAINING WELL TO SOUTH. ADDED SLIGHT CHANCE POPS FOR AREA ROUGHLY 
SOUTH OF HIGHWAY 34 FOR THIS MORNING AS THIS SHORTWAVE SLIDES 
THROUGH. 

GFS HAD BEST HANDLE ON THE UPSTREAM SHORTWAVE OVER NORTH DAKOTA THAT 
WILL SLIDE ACROSS AREA THIS AFTERNOON. BEST THUNDERSTORM CHANCES 
LOOK TO BE EAST OF MISS RIVER IN AFTERNOON...WHERE COOL POOL ALOFT 
RESULTS IN OVERLAP OF STEEP LOW LEVEL LAPSE RATES IN FAR NW IL THAT 
OVERLAPS AREA OF META CAPES ABOVE 1500 J/KG AND H85 FRONT. RAISED 
AFTERNOON POPS TO 40 PERCENT THERE...TAPERING BACK TO SLIGHT OVER SE 
IA AND FAR NORTHEAST MO. WENT A BIT ABOVE GFS MOS FOR HIGHS. UPPER 
LOW WOBBLES INTO NORTHWEST WI BY SUNDAY MORNING. KEPT LOW CHANCES 
GOING MAINLY OVER EAST SATURDAY NIGHT...FOR EAST OF MISS RIVER UNDER 
UPPER TROUGH AXIS SHOWN TO EXTEND SOUTH FROM LOW. UPPER LOW 
GRADUALLY FILLS SUNDAY...AND SETTLES SOUTH TO NEAR CHI BY MONDAY 
MORNING. MAIN VORT MAXIMA ROTATING AROUND LOW CROSS CWA IN AFTERNOON 
AND EVENING HOURS AND THUS KEPT THE LOW SCATTERED POPS IN THAT 
TIMEFRAME.  ...SHEETS

MONDAY AND MONDAY NIGHT...THERE IS SOME QUESTION ABOUT WHETHER THE 
UPPER LEVEL LOW WILL MANAGE TO SHIFT EAST ENOUGH FOR MONDAY TO BE 
DRY FOR AT LEAST PART OF THE CWA.  MODELS TYPICALLY TRY TO PUSH 
SYSTEMS LIKE THIS THROUGH THE FLOW TOO QUICKLY...THOUGH PATTERN 
RECOGNITION TECHNIQUES WOULD CERTAINLY IMPLY THAT MONDAY SHOULD BE 
DRY FOR AT LEAST THE NORTHWESTERN PORTIONS OF THE CWA.  HAVE LEFT 
THE LOW CHANCE POPS FOR REMAINDER OF CWA.  TEMPS TO CONTINUE TO RUN 
WELL BELOW NORMAL...WITH RIDGE BUILDING IN AND NORTHERLY FLOW 
CONTINUING.  

TUESDAY THROUGH FRIDAY...THE UPPER LEVEL AND SURFACE RIDGE BUILDS IN 
NICELY...WITH NORTHWEST FLOW ALOFT.  AM A LITTLE CONCERNED ABOUT THE 
DRY FORECAST FOR THE TUESDAY NIGHT AND WEDNESDAY TIMEFRAME...WITH 
STILL ENOUGH ENERGY WITH A VORT MAX DROPPING SOUTH OUT OF WI TO 
SQUEEZE OUT SOME SHOWERS. THE VORT MAX ACTUALLY MOVES THROUGH LATE 
TUESDAY NIGHT...AND DUE TO THE TIMING AND LACK OF A FEW OTHER 
FEATURES...HAVE DECIDED TO LEAVE DRY FOR NOW...AND LATER SHIFTS CAN 
RE-CONSIDER.  OTHERWISE...GRADUAL WARMING TREND THROUGH THE PERIOD.
...LE

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

$$