[LeArc] Forecast Discussion : MLI@ 9/29/02 2:36:41 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 291945
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 PM CDT SUN SEP 29 2002

SLOW NORTHERN PROGRESSION OF WARM FRONT EVIDENT BY THE RAPID
DISSISSIPATION OF STRATUS ACROSS NORTHERN IA LATE THIS MORNING AND
EARLY AFTERNOON.  SOUTH OF THE BOUNDARY TEMPS IN THE MID AND UPPER 80S
COMMON ACROSS MOST OF CWA BY 19Z.  UPPER LEVEL FLOW DOMINATED BY BROAD
SWLY FLOW BETWEEN TROUGH OVER W COAST AND UPPER RIDGE OVER SERN U.S.

MAIN CONCERN WILL BE PCPN THREAT THIS EVENING WITH BOUNDARY RETREATING
NORTH THEN PCPN THREAT TUESDAY/WEDNSDAY AS FRONT MOVES BACK THROUGH
THE REGION.

MODELS IN GOOD AGREEMENT THIS MORNING HANDLING WRN U.S. TROUGH AND
WEAK IMPULSES EJECTING OUT OF TROUGH THROUGH MONDAY.  THERE IS SOME
DISAGREEMENT WITH CANADIAN S/W THATS PROGGED TO DRIVE SFC THROUGH
THROUGH THE REGION BY MID WEEK.  AVN IS A LITTLE SLOWER WITH THE WAVE
AND THEREFORE MOVES SURFACE BOUNDARY THROUGH THE REGION A LITTLE LATER
THAN ETA. THIS WILL HAVE SIGNIFICANT IMPACTS ON TEMPS AND PCPN TRENDS
TUESDAY AND WEDNESDAY. SLOWER MOVEMENT OF THE AVN IS FAVORED SINCE
FRONT WILL BE PARALLEL TO THE UPPER FLOW AND WILL BE MOVING INTO UPPER
RIDGE.


WARM FRONT AT 18Z ROUGHLY FROM SOUTH OF SUX TO NE CORNER OF IA.
DESPITE GOOD WARMING AND LOW 60 DEWPOINTS SOUTH OF BOUNDARY...
THERE IS NO FOCUS NEAR CWA TO FORCE CONVECTION.  ALSO EARLY
AFTERNOON LAPS DATA INDICATING SUFFICIENT CAPPING TO SUPPRESS
THUNDERSTORM DEVELOPMENT.  DRY FORECAST WILL CONITNUE OVER
NIGHT WITH TEMPERATURES STAYING ON THE MILD SIDE. SOUTHERLY FLOW TONIGHT
AND DEW POINTS AROUND 60 WILL KEEP TEMPS IN THE MID 60S. WE SHOULD SEE
ANOTHER WARM DAY ON MONDAY WITH  STRONG SOUTHERLY FLOW AND SUNSHINE.
WILL GO WITH TEMPS A NOTCH HIGHER THAN TODAY...WHICH BY THE WAY WILL BE
JUST UNDER RECORD HIGHS FOR THE 30TH. MODELS ARE SHOWING SWRN U.S.
S/W MOVING NW OF CWA AROUND MID DAY MONDAY.  HOWEVER...IT DOESN'T APPEAR
IMPULSE WILL BE CLOSE ENOUGH TO BE OF MUCH CONCERN.  AVN IS
SUGGESTING PCPN POSSIBLE FOR MONDAY NIGHT AS IT TRIES TO DROP BOUNDARY
TO JUST NORTH OF CWA. ALSO WAVE DEVELOPING ALONG FRONT OVER KS MAY
PROVIDE A FOCUS FOR LATE NIGHT CONVECTION AND UPPER FLOW SHOULD MOVE IT
NORTHEAST.  WILL INTRODUCE A LOW CHANCE LATE TUESDAY NIGHT TO COVER THIS
THREAT. CHANCE POPS WILL CONTINUE THEN THROUGH WEDNESDAY AS FRONT
PROGRESSES SLOWLY SOUTH THROUGH REGION. MAV NUMBERS LOOK REASONABLE
TUESDAY AND WEDNESDAY.


EXTENDED (THURSDAY THROUGH SUNDAY)

LONG RANGE MODELS ALL AGREE ON THE GENERAL IDEA OF EJECTING SW TROUGH
DURING THE FIRST HALF OF THE EXTENDED PERIOD.  BUT THERE IS SOME
DISAGREEMENT ON THE TIMING OF THE SYSTEM AS IT MOVES THROUGH THE
MISSISSIPPI VALLEY AND THROUGH THE GREAT LAKES FRIDAY. 12Z AVN
MUCH SLOWER THAN 00Z RUN WITH 12Z AVN STILL DEPICTING A CLOSED SYSTEM AT
H5 FRIDAY MORNING AND HOLDING SURFACE LOW OVER ERN NE. 00Z MRF WAS
CONSIDERABLY FASTER WITH AN OPEN WAVE AND SURFACE SYSTEM OVER THE UPPER
MS RIVER VALLEY BY EARLY FRIDAY. COMPLICATING THIS PICTURE WILL BE THE
REMANTS OF LILLI WITH ALL LONG RANGE MODLES SHOWING LILLI MOVING
ONSHORE LATE NEXT WEEK AND LIFTING NE AHEAD OF EJECTING SW U.S. TROF.
DEPENDING ON HOW THINGS EVOLVE LATE NEXT WEEK...THIS COULD BE A
SIGNIFICANT RAINFALL EVENT FOR THE MID MISSISSIPPI VALLEY. WILL SIDE
WITH THE SLOER AVN SOLUTION FOR THIS FORECAST...WHICH WILL KEEP TRENDS
CLOSE TO CURRENT FORECAST PACKAGE.  BASED ON 12Z AVN WILL HAVE TO
INTRODUCE POPS FOR THURSDAY AND CONTINUE MENTION ON FRIDAY.  AVN
BRINGS FRONT BACK NORTH WEDNESDAY NIGHT.  SO WITH FRONT IN THE AREA
THROUGH ITS HARD TO GO WITH A DRY FCST. AVN LIFTS FRONT THROUGH CWA
DURING DAY THURSDAY AHEAD OF DEVELOPING PLAINS LOW...SO MILD TEMPS
SHOULD MAKE A BRIEF RETURN. TEMPS SHOULD CRASH BY SATURDAY AS SYSTEM
PULLS TO THE EAST AND COOL CANADIAN AIR MOVES INTO REGION. MEX NUMBERS
FOR SATURDAY LOOK REASONABLE WITH SURFACE RIDGE STILL TO OUR WEST AT
12Z. WILL GO A LITTLE COOLER THAN MEX SUNDAY MORNING WITH MRF SHOWING
SFC RIDGE OVER AREA. RIDGE MOVES EAST BY 00Z MON...ALLOWING RETURN FLOW
TO SET UP.

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