Flooding in Iowa, May 1 to 3, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 PM CDT TUE APR 30 2002

NARROWING BAND OF LIGHT RAIN/SPRINKLES BEING ERODED BY DRIER
NORTHERLY LLVL FLOW AS IT MOVES EAST OF ITS BETTER SUPPORT...AND
SHOULD BE MOSTLY DONE SO AS NOT TO HAVE TO WALK OUT IN EVENING ZONES.
OTHER THAN THAT...SLOWER MODEL RUNS WITH MAIN SHOW MAY MEAN MOST OF
NIGHT DRY. FAR NORTH AND SOUTH CWA MAY EVEN BE CHARACTERIZED BY
PARTLY CLOUDY SKIES TONIGHT. AS VORT...SEEN ON W/V IMAGERY OVER
NORTHERN WY...SHEARS EAST IN CONFLUENT FLOW OVER THE AREA BY LATE
TONIGHT...MAY COMBINE WITH INITIAL OVER-RUNNING SURGE FROM DEVELOPING
SOUTHERN PLAINS LOW OVER SOUTHERN MO BOUNDARY FOR SOME CLOUD AND
PRECIP GENERATION TOWARD MORNING ACRS SOUTH AND SOUTHWEST. MAY KEEP
NORTH DRY. WILL GO WITH LOWS SIMILAR TO LAST NIGHT...WHICH LINES UP
WELL WITH MAV/FWC BLEND.

NORTHERN STREAM VORTEX WILL LOOK TO ROLL TO SOUTHERN LK WINNIPEG
VCNTY BY 00Z THU. AS IT DOES...IT WILL TRY AND PHASE WITH SOUTHERN
STREAM...EFFECTIVELY ALIGNING CONFLUENT STORM PATH IN A WEST-
NORTHWEST FASHION FOR FURTHER NORTH PROPAGATION PATH...ALA AVN.
LATEST ETA HAS TRENDED FURTHER NORTH TO YESTERDAYS AVN RUN...BUT BOTH
HAVE SLOWED SYSTEM FOR DELAYED PRECIP ARRIVAL. ETA TAKES SFC LOW TO
JUST WEST OF STL BY 00Z THU...WHILE EVEN FURTHER NORTH AVN NOW NEAR
PIA BY 00Z. WILL JUMP ON AVN BAND WAGON WITH ITS CONSISTENCY LAST FEW
RUNS...WHICH COULD MEAN LOCALLY HEAVY RAIN ACRS NORTH HALF OF CWA
WITH WARM CONVEYOR BELT FEED OFF WEST GULF. SOUTHEAST CWA COULD SEE
LOCALLY HEAVY RAIN WED AFTERNOON AS WELL FROM POSSIBLY STRONG
CONVECTION AS TRIPLE POINT SWIPES THROUGH WEST CENTRAL IL. EVEN
FARTHER SOUTH ETA PLACES HEAVIER OVER-RUNNING PRECIP BANDS/PUSHING AN
INCH/ ACRS THE NORTHERN THIRD OF IA WED AFTERNOON AND EVENING. THIS
MAY WARRANT THE INTRODUCTION OF LOCALLY HEAVY RAIN WORDING FOR WED
AFTERNOON. FURTHER NORTH OF WARM SECTOR...ELEVATED INSTABILITY
MARGINAL FOR THUNDER...BUT WILL STILL KEEP FOR WED AFTERNOON THROUGH
AT LEAST CENTRAL PORTIONS/I-80 CORRIDOR. WITH CLOUD COVER AND PRECIP
SHIELD...WILL LEAN TOWARD COOLER MAV HIGHS. FAR SOUTHEAST WHICH MAY
EXPERIENCE A PERIOD OF WARM SECTOR WED AFTERNOON MAY RISE
CONSIDERABLY WARMER THAN REST OF CWA. THUS EXPECT A BIG TEMP GRADIENT
BY LATE WED AFTERNOON FROM DBQ...TO MACOMB. MACOMB COULD CLIMB WELL
INTO 70S...WHILE DBQ BATHED IN INCREASING NORTHEAST FLOW HELD IN THE
50S. WILL BANK ON BULK OF PRECIP TO BE EAST OF CWA BY 06Z THU.

AS UPPER VORTEX AND COOL POOL DROPS ACRS WI ON THU...EXPECT STEEP
LLVL LAPSE RATES AND CYCLONIC FLOW TO INDUCE PLENTY OF CU...TO MOSTLY
CLOUDY STATE ACRS NORTHEAST THIRD. AM LESS ENTHUSIASTIC OF
INSTABILITY SHOWERS WED AFTERNOON WITH LACK OF STEEPER MID LEVEL
LAPSE RATES...BUT WILL KEEP LOW POPS FOR WIDELY SCTRD SHOWERS WHERE
MOSTLY CLOUDY WORDING IS USED. WILL GO PARTLY CLOUDY AND DRY ACRS
SOUTHWEST HALF. WITH EXTENT OF H85 COOLING AND EXPECTED MIXING ON
THU...FEEL COOLER MAV LOOKS BETTER EVEN IN AREAS THAT RECEIVE SOME
INSOLATION.

.LONGER RANGE(FRI-TUE)...MEDIUM RANGE MODELS AGREE ON LOWER AND UPPER
RIDGING BRINGING MODERATING END TO WEEK. TEMPS SHOULD RECOVER BACK
WELL INTO THE 60S ON FRI WITH RETURN FLOW IN LOWER LEVELS. MODELS
GENERALLY AGREE ON SOUTHWEST FLOW REGIME THEN TAKING OVER FOR A MUCH
MILDER REST OF LONG RANGE PERIOD...ALBEIT PROBABLY A WET ONE AS WELL.
FIRST FRONT USHERED ACRS CWA BY PHASING NORTHERN AND SOUTHERN STREAMS
FOR SHOWER AND THUNDERSTORM CHANCE SAT AFTERNOON. BOUNDARY THEN GETS
LAID OUT IN WEST-SOUTHWEST FLOW SOMEWHERE IN VCNTY OF CWA...AND WITH
VORT ENERGY OCCASIONALLY GETTING FUNNELED UP OUT OF WESTERN CONUS L/W
TROUGH UP OVER AREA...LOOKS LIKE ALMOST DAILY PRECIP CHANCE INTO TUE.
EVEN WITH RATHER MOIST VERTICAL PROFILES AND CLOUD COVER...PROJECTED
LLVL THERMAL PARAMETERS SUPPORT 70S FOR HIGHS SUN THROUGH TUE.

COORDINATED WITH ILX...THANX

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

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