[LeArc] Forecast Discussion : MLI@ 8/23/02 1:21:13 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 230625
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
125 AM CDT FRI AUG 23 2002

.OVERVIEW...INTENSE FLOODING CONTINUES WITH NEXT MCS/MCC...WILL BE
BRIEF.  INTENSE CONVECTION STILL INTENSIFYING ALONG FRONT FROM CENTRAL
ILLINOIS TO NEAR DES MOINES INTO A MCC IN WEST CENTRAL IOWA.  SURFACE
AND UPPER AIR ANALYSIS SUPPORT WAVE MOVING ALONG BOUNDARY ACROSS
HIGHWAY 34 WITH SURFACE LOW PASSING EAST TOWARD MID DAY FRIDAY.  THIS
SUPPORTS HEAVY PRECIP CHANCES ENDING FROM WEST TO EAST ON FRIDAY
MORNING INTO EARLY AFTERNOON.  ALREADY NUMEROUS COUNTIES WITH 2 TO 4
INCHES AND ANOTHER 3 TO 6 INCHES POSSIBLE WITH WAVE.   ALL INDICATIONS
SUGGEST LARGE AREA OF ANOTHER OF 4 TO 10 INCHES OR MORE NEXT 8-12
HOURS...WITH BEST ESTIMATE ALONG AND SOUTH OF HIGHWAY 34.  THIS ON TOP
OF MAJOR FLOODING NORTH OF I-80 FROM YESTERDAY/S 6 TO 11 INCHES ALONG
HIGHWAY 20. APPEARS SEVERE CHANCES LIMITED TO MORE ISOLATED VARIETY DUE
TO VERY MOIST ATMOSPHERE AND MARGINAL FORCING/INSTABILITY WITH ACTIVITY
NEAR DSM AT 06Z BIGGEST POTENTIAL WITH SMALL BOW SEGMENT WITH WINDS.

...MAJOR FLOODING BIG CONCERN...

.DIAGNOSIS AND DAYS 1-3...MODELS INITIALIZE VERY POORLY ON QPF WITH
INTENSE CONVECTION IN WRONG PLACE (ESPECIALLY ETA/NGM WHICH HAVE HEAVY
RAINS IN MISSOURI!)...AVN IS FAIR AND WILL COMBINE IT WITH UKMET AND
LATEST ANALYSIS TOOLS SUPPORTING FLOOD WATCH ALONG AND SOUTH OF I-80
TODAY AS WILL NOT GET CUTE WITH ENDING DUE TO SERIOUS NATURE OF EVENT AS
IT UNFOLDS.  ALREADY NUMEROUS FLASH FLOOD WARNING NEEDED WITH PROLIFIC
RAINS AS THIS COULD BE AS BAD...IF NOT WORSE THEN LAST NIGHTS EVENT...
ESPECIALLY WITH AREA COVERAGE OF HIGH QPF AMOUNTS.  PLAN TO ADJUST TEMPS
DOWN TODAY WITH CLOUDS AND PRECIPITATION.  IF HAVE TIME MAY MAKE MINOR
CHANGES TO DAYS 2/3 OF TEMPS BUT HIGH PRESSURE SHOULD LIMIT ANY
ADDITIONAL QPF CHANCES.

.EXTENDED (MON-THU)...ECMWF HAS MAJOR TROUGH AND FRONT BY MID WEEK.
WILL TRY AND LOOK AT UKMET AND AVN/MRF BUT PLAN LITTLE OR NO CHANGES AT
THIS TIME.

COORDINATED WITH LSX...DSM...LOT...ILX...THANKS.

.DVN...FLOOD WATCH TODAY.
IA...ALONG/SOUTH OF I-80.
IL...ALONG/SOUTH OF I-80.
MO...EXTREME NE MISSOURI.

NICHOLS