Severe Thunderstorm Warning 179, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
255 PM CDT FRI SEP 22 2000

LATEST SFC AND MSAS ANALYSIS INDICATING SFC LOW ACRS SOUTHWEST IA...WITH
MAIN WARM FRONT EXTENDING EAST-SOUTHEAST ACRS FAR SOUTHEAST IA INTO
WEST CENTRAL IL. ETA BEST IN HANDLING THESE POSITIONS...AS WELL AS
OTHER PARAMETERS SUCH AS RH AND PRECIP AND WILL FOLLOW GENERAL ETA/
MESOETA SOLUTIONS THRU FCST PERIODS. AS ELEVATED MCS MOVES OFF
NORTHEAST OF CWA...VIS SAT LOOPS INDICATING BREAKS IN CLOUD COVER
BUILDING ACRS SOUTH HALF OF CWA. SOME ATMOSPHERIC RECOVERY/
DESTABILIZATION TAKING PLACE ACRS THOSE AREAS WITH INSOLATION AND DPTS
CREEPING UP INTO THE 60S...BUT ENOUGH TO FUEL SVR STORMS LATER?

FEEL IT MAY...LOOKING AT MSAS LOOP AND LARGE PRESSURE FALLS FROM WEST
CENTRAL WI...EXTENDING SOUTH ACRS DVN CWA. LOCAL VAD WIND PROFILE
ALSO SHOWING STRONG LLVL SHEAR CONTINUING AS WELL. SFC LOW AND TRIPLE
POINT WILL LOOK TO PROPAGATE ACRS CENTRAL INTO THE NORTHEAST CWA THRU
06Z SAT...WITH MOST OF CWA IN LINE FOR ANOTHER ROUND OF CONVECTION. BEST
CAPES...BREACHING THE 1K J/KG MARK...ARE PROGGED ACRS THE SOUTHEAST CWA
FROM 00Z-06Z...AND FEEL MOST INTENSE/SVR THREAT WILL BE SOUTH OF WARM
FRNT ACRS SOUTHEAST THIRD OF CWA THIS EVENING. AFTER PASSAGE OF MAIN
VORT THIS AFTERNOON...UPPER SUPPORT WILL BE LACKING AND SOMEWHAT OF A
LIMITING FACTOR...ALTHOUGH SOME JET DYNAMICS WILL CONTINUE JUST TO THE
NORTH OF THE REGION. WEAK VORT NOW SEEN ON W/V IMAGERY PUSHING ACRS THE
NE PANHANDLE...WILL SHEAR JUST TO THE NORTH ACRS MN AND WI TONIGHT...
MAYBE PROVIDING A GLANCING SHOT OF UVV/S ACRS PORTIONS TO THE DVN CWA...
BUT NOT TIL LATE TONIGHT/SAT MORNING. WITH GOOD SFC-H85 THTA-E ADVECTION
CONTINUING ACRS EAST IA/NORTHWEST IL FOR FIRST HALF OF TONIGHT AND
POTENTIAL FOR MORE HEFTY STORMS...ADDITIONAL HEAVY RAIN IS POSSIBLE ACRS
MUCH OF THE CWA...AND WILL SERIOUSLY PONDER POSSIBLITIY OF A FLASH FLOOD
WATCH TONIGHT OVER AREAS THAT RECEIVED HEAVY RAIN THIS MORNING AND
AFTERNOON. TEMPERATURES WILL HOLD STEADY OR EVEN CONTINUE TO RISE
OVERNIGHT OVER EAST HALF OF CWA...UNTIL DROPPING OFF A BIT TOWARD 11Z OR
SO...FOR OVERNIGHT LOWS.

UPPER LEVEL FLOW WILL REMAIN WEST-SOUTHWEST ACRS AREA THROUGH AT LEAST
12Z SUN...AS L/W TROUGH OUT WEST TRIES TO PINCH OFF INTO A CUT-OFF
UPPER LOW OVER THE CENTRAL ROCKIES. MAIN SFC FRONT WILL GET ORIENTED
PARALLEL TO UPPER FLOW JUST TO THE EAST AND SOUTH OF THE CWA TONIGHT
AND SAT...AND THUS GET HUNG UP AND SLOW TO MOVE. LARGE SFC RIDGE
BUILDING OUT OF ALBERTA AND SASK. WILL EVENTUALLY SHUNT THE FRONT
FURTHER SOUTHEAST BY THE END OF THE WEEKEND. UNTIL THEN...H85
BAROCLINICITY/FRONT WILL SHIFT BACK SOUTH ACRS THE NORTHWEST CWA BY
12Z SAT...AND THEN CREEP SLOWLY SOUTHEAST ACRS THE REST OF THE CWA
THROUGH 12Z SUN AS FRONT GETS SLOWED BY WESTERLY UPPER FLOW. LLVL/H85
RH/S AND LMRH/S REMAIN HIGH ACRS THE CWA THROUGH AT LEAST 18Z SUN
BEFORE SOME LLVL DRYING FINALLY TAKE PLACE LATE SUN AFTERNOON/EVENING.
AS LLVL CAA KICKS IN ON SAT INTO JUICED ATMOSPHERE IN PLACE OVER EAST
IA/NW IL...AND LINGERING H85 FRONT AND SOME CONVERGENCE AS WELL...
WILL KEEP RAIN/DRIZZLE WORDING GOING ALL DAY. TEMPS SHOULD HOLD
STEADY...OR EVEN DROP OFF BY LATE AFTERNOON. PRECIP SHOULD END SAT NIGHT
...ALTHOUGH DRIZZLE MAY LINGER IN THE EVENING. CLOUD COVER WILL HELP
FROM TEMPS REALLY BOTTOMING OUT SAT NIGHT. CONFLUENT UPPER FLOW AND
SOME VORTS LOOK TO SHIFT ACRS IA ON SUNDAY...BUT BEST PRECIP THREAT BY
THEN WILL BE SOUTH OF CWA...ALTHOUGH ADDITIONAL DRIZZLE MAY FALL ACRS
SOUTHERN CWA THROUGH AT LEAST MIDDAY.

IN THE EXTENDED...MON-TUE-WED...MRF HAS COME AROUND CLOSER TO EUROPEAN
SOLUTION THIS RUN OF RIPPLING CLOSED UPPER LOW ALONG SOUTHERN PERIPHERY
OF HUDSON BAY POLAR VORTEX...ALTHOUGH MRF BIT FURTHER SOUTH AND MORE
PROGRESSIVE. STILL...AS THIS FEATURE SWEEPS ACRS THE MIDWEST ON MON AND
LLVL BAROCLINICITY SETS UP JUST SOUTH OF THE REGION...LOOKS LIKE COOL
OVER-RUNNING RAIN EVENT FOR FIRST DAY OF EXTENDED. BOTH EURO AND MRF
THEN MOVE PRECIP EAST OF CWA MON NIGHT AS ANOTHER CANADIAN SFC RIDGE
STARTS TO BUILD INTO THE UPPER MIDWEST. FEEL AND WRAP AROUND PRECIP
IN STRONG CYCLONIC FLOW ALOFT...WILL REMAIN NORTHEAST OF CWA CLOSER TO
BETTER CVA SUPPORT. WILL REMOVE TUE PRECIP CHANCE. WITH SOME INSOLATION
GETTING INTO THE CWA ON TUES...FMR MAY BE A BIT COOL...EVEN WITH SUCH
COOL H85 TEMPS PROGGED ACRS THE AREA. FELL TEMPS WILL AT LEAST CREEP UP
INTO THE LOWER 60S. TUE NIGHT COULD BE COLD ENOUGH FOR SOME FROST AS
FULL COOLING EFFECT WILL BE REALIZED AS SFC RIDGE CENTER SETTLES ACRS
THE AREA. WILL CONTINUE DRY TREND INTO WED AS SFC RIDGE SINKS TO THE
SOUTHEAST. SOME RETURN FLOW WARMING ON BACKSIDE...BUT AFTER SUCH A COOL
START TO DAY...WILL GO SIMILAR TO TUE HIGHS ON WED.

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

JDH

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-009-
015>018-024>026-034-035-MOZ009-010-230930-

SIGNIFICANT WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
351 PM CDT FRI SEP 22 2000

...SHOWERS AND THUNDERSTORMS REDEVELOPING THIS EVENING...
...SEVERE THUNDERSTORMS AND HEAVY RAINS POSSIBLE...

A WARM FRONT WILL LIFT NORTH INTO SOUTHEAST IOWA AND NORTHWEST ILLINOIS
THIS EVENING...POSSIBLY TO NEAR A MOUNT PLEASANT TO QUAD CITIES TO
MORRISON LINE.  A COLD FRONT WILL SWEEP INTO THE AREA LATE TONIGHT...
PUSHING THE WARM FRONT EAST OF THE AREA.  SEVERE THUNDERSTORMS WILL BE
POSSIBLE TONIGHT NEAR AND JUST NORTH OF THE WARM FRONT...AND ALSO
SOUTH TOWARDS BURLINGTON AND KEOKUK AHEAD OF THE ADVANCING COLD FRONT.
THE PRIMARY THREAT WILL BE HIGH WINDS OF UP TO 60 MPH AND LARGE HAIL
OF UP AN INCH OR THE SIZE OF QUARTERS.

HEAVY RAINS WILL BE POSSIBLE TONIGHT NEAR AND NORTH OF THE WARM FRONT.
THE GREATEST THREAT FOR STREAM FLOODING WILL BE IN AREAS THAT HAD
HEAVY RAIN EARLIER TODAY...INCLUDING IOWA...KEOKUK...JOHNSON...CLINTON
...JACKSON...AND CEDAR COUNTIES.  A FLASH FLOOD WATCH WILL BE IN EFFECT
TONIGHT FOR EASTERN IOWA AND NORTHWEST ILLINOIS...NEAR AND NORTH OF A
LINE FROM KEOSAUQUA TO MOUNT PLEASANT TO WAPELLO TO KEWANEE TO
PRINCETON.

SPOTTERS...LOCAL LAW ENFORCEMENT...AND EMERGENCY MANAGERS IN THE
OUTLINED AREA ABOVE SHOULD PLAN FOR POTENTIALLY SEVERE WEATHER AND
LOCALLY HEAVY RAINS WHICH MAY PRODUCE FLOODING THIS EVENING OR
OVERNIGHT.

REA