Flash Flood Warning 8, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
712 PM CDT SUN MAY 26 1996

THE 23Z MAPS ANALYSIS SHOWED THE SURFACE LOW NEAR THE PANHANDLE OF OK
WITH THE FRONTAL BOUNDARY EAST TO STL AND THEN INTO THE OH VALLEY. THE
PROFILER NETWORK ALONG WITH THE WATER VAPOUR MATINEE SHOWED A VIGOROUS
SHORTWAVE OVER WESTERN KS. AHEAD OF THE SHORTWAVE OVER EASTERN KS AND
EXTREME NORTHWEST MO...STRONG MOISTURE FLUX CONVERGENCE WAS SEEN. THE
COMBINATION WAS PRODUCING AN ACTIVE BLOB OF THUNDERSTORMS HEADING
NORTHEAST AT 30 KNOTS. THE MCV THAT AFFECTED THE CWA THIS AFTERNOON IS
NOW EAST OF THE AREA. FINALLY...AN AREA OF PERSISTANT ISENTROPIC LIFT
AT 305K WAS PRODUCING SOME SPRINKLES AND RW- ACROSS NORTHERN IA. IT/S
GONNA RAIN...THE QUESTION APTLY PUT BY THE PREVIOUS SFDDSM IS HOW
MUCH.

THE 12Z ETA/NGM INITIALIZED ALRIGHT...AND NEAR 00Z THE ETA HAD THE BEST
HANDLE ON THE MCV...SHORTWAVE OVER OK...AND SURFACE BOUNDARY.
OVERNIGHT...THE MODELS AGREE ON SLOWLY EJECTING THE UPPER LOW INTO THE
CENTRAL PLAINS WITH A 60 KNOT JET AT 500MB AND 90 JET AT 300MB. LOOKING
THE MOST RECENT 500MB PLAN PROFILER VIEW...IT APPEARS THE ETA HAS
UNDERESTIMATED THE STRENGTH OF THE SHORTWAVE...AS 85 KNOTS WAS SHOWN
IN NORTH CENTRAL OK. IMPRESSIVE DIVERGENCE IS FORECAST OVER WESTERN IA
INTO MO BY MIDNIGHT. THE LOW LEVEL JET RESPONDS BY MAINTAINING ITS
30-40 KNOT STRENGTH CROSSING THE SURFACE BOUNDARY INTO SOUTHERN IA.
THIS SHOULD HELP SUSTAIN CURRENT CONVECTION. QG AND FRONTOGENETICAL
FORCING IN THE LOW LEVELS IS VERY IMPRESSIVE OVER SOUTHWEST IA AT
06Z...AND THEN IT PROPAGATES EASTWARD BY 12Z.

CURRENT EXTRAPOLATION PUSHES THE CURRENT CONVECTION TO BRL BY 04Z AND
CID/MLI BY 06Z. PRECIPITABLE WATER VALUES ARE BEST SOUTH OF INTERSTATE
80...IN THE 1.4 INCH AREA. HENCE...THE HEAVIEST RAIN SOUTH FALL IN THAT
AREA. THE SEVERE THREAT SHOULD REMAIN SOUTH OF THE CWA...WHERE THE 23Z
ADAP DATA SHOWS THE BEST INSTABILITY AND SURFACE MOIST FLUX
CONVERGENCE. IF THIS SYSTEM REALLY IS STRONGER THAN THE MODELS
FORECAST...WE ARE IN FOR A LONG NIGHT.

I SUGGEST SHOWERS AND THUNDERSTORMS (RE)DEVELOPING CWA-WIDE. ALSO...LOW
TO MID 40S FOR DBQ LOOKS A LITTLE LOW. AND...A MENTION OF HEAVY RAIN VIS
WARRANTED FOR EXTREME SOUTHEAST IA. THE COOLER FAN GUIDANCE BETTER
REPRESENTS EXPECTED LOWS.

CID 050/++  DBQ 048/++  MLI 051/++  BRL 053/++

HELGESON

IAZ099-ILZ034-035-270815-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
108 AM CDT MON MAY 27 1996

...URBAN AND SMALL STREAM FLOOD ADVISORIES CONTINUE FOR LEE COUNTY IN
IOWA AND HANCOCK AND MCDONOUGH COUNTIES UNTIL 300 AM THIS MONDAY
WARNING...

AT 105 AM...NWS DOPPLER RADAR CONTINUES TO INDICATED STRONG
THUNDERSTORMS OVER THE ABOVE MENTIONED COUNTIES WITH TORRENTIAL RAIN...
FREQUENT DEADLY LIGHTNING AND SOME GUSTY WIND.  RAINFALL RATES
OF AN INCH PER HOUR WILL BE COMMON WITH THESE THUNDERSTORMS. PERSONS
WHO LIVE IN LOW LYING AREAS OR FLOOD PRONE AREAS SHOULD BE PREPARED TO
MOVE TO HIGHER GROUND IF FLOODING IS OBSERVED.

PERSONS OUT DRIVING TONIGHT SHOULD NOT D~RIVE INTO AREAS WHERE WATER
COVERS THE ROADS AS ONLY WATER A FOOT DEEP CAN SWEEP A CAR OFF THE ROAD.

HOLSTEN