River Flood Warning 121, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
250 PM CDT THU MAY 29 2008

.SHORT TERM...TONIGHT AND FRIDAY...
IT IS STILL SHAPING UP TO BE A POTENTIALLY SERIOUS FLOODING/FLASH
FLOODING SCENARIO UNFOLDING TONIGHT AND FRIDAY DUE TO IMPACTS OF
HEAVY RAIN PRODUCING MCS/MCSS. AREAS MOST SUSCEPTIBLE ARE ALONG
AND NORTH OF I80 WHERE FFG VALUES RANGE FROM 1.5 TO 3.0 FOR 3 TO 6
HRS. SECONDARY WING OF CONVERGENT LLJ AND LEAD VORT NOW INDUCING
ELEVATED SHOWERS AND STORMS OVER CENTRAL IA...WITH THE ACTIVITY
TEMPORARILY WANING AS IT PROPAGATES EAST OF BETTER SUPPORT AND OVER A
MORE STABLE AIRMASS OVER EASTERN IA. THIS ACTIVITY EXPECTED TO
CONTINUE INTO THE EVENING...BUT AS SLIGHTLY VEERING LLJ INCREASES
INTO THE WESTERN CWA...WILL BE BETTER LLVL THTA-E ADVECTION
AND CONVERGENT SUPPORT TO KEEP ELEVATED CONVECTION GOING AND MORE
ROBUST THEN IT IS CURRENTLY...POSSIBLY FORMING AS A LEAD MCS. THIS
LABELED A LEAD MCS BECAUSE THE MAIN PUNCH OF MCS SPAWNING PARAMETERS
COME TOGETHER TO INITIATE SEVERE CONVECTION OVER CENTRAL NEB INTO
SOUTHEAST CO OVER THE NEXT 2-4 HRS. THEN...A PROGGED 50+ KT LLJ
EXPECTED TO TAKE AIM AT THE DVN CWA AS THE NIGHT PROGRESSES...
ALLOWING EXTREME ELEVATED THTA-E ADVECTION AND CONVERGENT PATTERN AND
THE ASSOCIATED MCS THAT WILL BE FEEDING ON THIS FETCH...TO MIGRATE
EASTWARD INTO THE LOCAL FCST AREA FROM THE WEST AS WELL TOWARD 06Z
AND BEYOND. COULD SEE A SCENARIO WHERE THE WESTERN ACTIVITY
PROPAGATES EAST AND MELDS INTO THE CENTRAL AND EASTERN IA LEAD
ACTIVITY OVERNIGHT...LEADING TO A WIDESPREAD HEAVY RAIN EVENT OF 1-3
INCHES AND LOCALLY UP TO 5 INCHES WITH THE NORTH HALF OF THE DVN CWA
RIGHT NOW LOOKING TO BE UNDER THE GUN OF RECEIVING THE MAIN
COMPLEX. HAVE ALREADY EXPANDED THE FLASH FLOOD WATCH EAST AND
SOUTH...AND WITH THE NORTHWEST 2-5 COUNTIES ALREADY RECEIVING
PERSISTENT RAINFALL TODAY AND GETTING PRIMED...MAY BE ISSUING FLASH
FLOOD WARNINGS FOR BUCHANAN/DELAWARE/DUBUQUE BY EARLY EVENING IF
CURRENT ACTIVITY PERSISTS OR INCREASES. IF NOT THIS EVENING...FCST
SOUNDINGS WITH DEEP SATURATION AND LIFT FROM 06Z ON AND PW/S OF
OVER 1.6 INCHES ALSO SUPPORT THE POTENTIAL NEED OF FFW/S IN MANY
COUNTIES OF THE DVN CWA LATER TONIGHT. HEAVY RAIN MAY GET INTO THE
SOUTHERN CWA AS WELL...BUT WITH HIGHER FLASH FLOOD GUIDANCE DOWN
THERE WILL HOLD OFF EXPANSION OF A WATCH FURTHER SOUTH FOR NOW. A
WATCH MAY BE NEEDED CWA-WIDE FOR FRIDAY IF CONVECTION PERSISTS WELL
INTO TOMORROW.

SVR THREAT FOR TONIGHT SECONDARY TO HEAVY RAIN AND FLASH FLOOD
POTENTIAL...BUT SLIGHTLY ELEVATED STORMS MAY STILL PRODUCE MARGINAL
SEVERE WX IN THE FORM OF HAIL UP TO 1 INCH...AND ISOLATED WIND MIX
DOWNS OF 55 TO 60 MPH. THESE SVR THREATS ALREADY ADVERTISED BY THE
PREVIOUS NIGHT CREW AND HAVE NOT CHANGED MUCH. THE MAQUOKETA...
WAPSI...AND CEDAR RIVER BASINS ARE IN LINE TO EXPERIENCE LARGE
RISES IF THE HEAVY RAIN PRODUCING STORM PROJECTIONS ARE IN LINE.

AS FOR FRIDAY...BESIDES THE HEAVY RAIN THREAT PERSISTING AND
SHIFTING SOUTHWARD...SPC HAS OUTLOOKED ALMOST THE ENTIRE CWA FOR A
MODERATE RISK. THE 12Z NAM SUPPORTS THIS...BUT ALSO SUGGESTS THAT
THE DVN CWA NOT RECEIVING MUCH TONIGHT AND ALLOWING THE CWA TO HEAT
UP AND DESTABILIZE AS STRONG NORTHERN STREAM WAVE DROPS SOUTHEAST
ACRS THE WESTERN GRT LKS. OF COURSE...MUCH WILL DEPEND ON
MCS ACTIVITY TONIGHT AND HOW MUCH OF THE CWA IT IMPACTS...AS
WELL AS WHERE IT LAYS OUT RESULTANT COLD POOLS AND MESOSCALE
BOUNDARIES. PERSISTENT CONVECTION AND DEBRIS FROM TONIGHT AND
LASTING INTO FRIDAY LATE MORNING OVER MOST OF THE DVN CWA COULD
NULLIFY THE MODERATE THREAT AND SHIFT IT MAINLY ALONG AND SOUTH/EAST
OF THE DVN CWA. IF THE SOUTH DOES NOT RECEIVE MUCH OR CONVECTION
ERODES QUICKER THAN EXPECTED FOR DAYTIME RECOVERY...THE SOUTHEAST
HALF OF THE DVN CWA WILL BE IN TROUBLE FOR SEVERE STORM SFC
BASED INITIATION. WILL STILL KEEP HIGH POPS GOING FOR HEAVY
CONVECTION THROUGH AT LEAST EARLY FRI AFTERNOON. AS FOR TEMPS ON
FRI...SIMILAR TO THE STORM POTENTIAL...THEY ARE HIGHLY DEPENDENT ON
WHAT OCCURS TONIGHT AND LINGERS INTO FRI. AM AFRAID OF GOING MUCH
WARMER THAN CURRENTLY ADVERTISED VALUES TAKING INTO ACCOUNT
CONVECTIVE DEBRIS/COLD POOLS.    ..JDH..

.LONG TERM...FRIDAY NIGHT THROUGH NEXT THURSDAY...
FRIDAY NIGHT WILL SEE THE CONVECTION EXIT QUICKLY TO THE SOUTHEAST
OF THE CWA...AND THIS MAY BE VERY EARLY IN THE PERIOD. AFTER IT
LEAVES...THE CWA WILL EXPERIENCE A GENERALLY QUIET WEEKEND...WITH
MINIMAL CHANCES FOR SHOWERS OR THUNDERSTORMS SATURDAY AFTERNOON AND
SUNDAY. THIS ACTIVITY SHOULD BE WEAK AND VERY SCATTERED.

THE PREFERRED EXTENDED SOLUTION BY OUR OFFICE AND HPC IS THE ECMWF.
MONDAY THROUGH NEXT THURSDAY IS EXPECTED TO BE VERY BUSY ONCE
AGAIN...WITH AN ACTIVE SOUTHWEST TO ZONAL FLOW...AND A NEARLY
STATIONARY OR WAVERING FRONT IN THE MIDWEST. THIS SHOULD PROVIDE
SEVERAL ROUNDS OF STRONG ORGANIZED CONVECTION...WITH BOTH STRONG TO
SEVERE STORMS AND HEAVY RAINFALL QUITE POSSIBLE. THIS PERIOD WILL
LIKELY RESULT IN INCREASED STREAM AND RIVER LEVELS...BUT UNTIL
CONFIDENCE INCREASES AFTER THE NEXT 24 HOURS...THE INDIVIDUAL RIVER
BASIN IMPACTS ARE UNRESOLVED.    ..ERVIN..

&&

.AVIATION...
THE DBQ AND POSSIBLY THE CID TERMINALS TO BE IMPACTED BY MVFR CIGS
AND VSBYS BY PASSING SHOWERS AND EMBEDDED THUNDERSTORMS THROUGH AT
LEAST 00Z...WITH ACTIVITY POSSIBLY NOT STOPPING UNTIL LARGER STORM
COMPLEX ARRIVES FROM THE WEST AFTER 04Z. THE MLI...DBQ AND CID
TERMINALS MOST SUSCEPTIBLE FOR THIS STRONGER ACTIVITY AFTER 05Z AND
ASSOCIATED IFR VSBYS/RAIN INTENSITIES AND CIGS REDUCED BELOW 2K
FEET. PASSING THUNDERSTORMS MAY ALSO PRODUCE HAIL AND VARIABLE WIND
GUSTS UP TO 40 KTS. THE MLI AND BRL TERMINALS WILL EXPERIENCE A
BRISK SOUTHERLY WIND FLOW AFTER 03Z WITH WARM FRONTAL PUSH TO THE
NORTH. ALL IN ALL A TURBULENT NIGHT IN THE VCNTY OF MOST OF THE DVN
TAF SITES.     ..JDH..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH FRIDAY
     MORNING FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-
     IOWA-JACKSON-JOHNSON-JONES-KEOKUK-LINN-LOUISA-MUSCATINE-
     SCOTT-WASHINGTON.

IL...FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH FRIDAY
     MORNING FOR CARROLL-JO DAVIESS-ROCK ISLAND-STEPHENSON-
     WHITESIDE.

MO...NONE.

&&

JDH/ERVIN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
455 AM CDT THU MAY 29 2008

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-300900-
BENTON IA-BUCHANAN IA-BUREAU IL-CARROLL IL-CEDAR IA-CLARK MO-CLINTON
IA-DELAWARE IA-DES MOINES IA-DUBUQUE IA-HANCOCK IL-HENDERSON IL-HENRY
IA-HENRY IL-IOWA IA-JACKSON IA-JEFFERSON IA-JO DAVIESS IL-JOHNSON IA-
JONES IA-KEOKUK IA-LEE IA-LINN IA-LOUISA IA-MCDONOUGH IL-MERCER IL-
MUSCATINE IA-PUTNAM IL-ROCK ISLAND IL-SCOTLAND MO-SCOTT IA-
STEPHENSON IL-VAN BUREN IA-WARREN IL-WASHINGTON IA-WHITESIDE IL-
455 AM CDT THU MAY 29 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
ILLINOIS...NORTHWEST ILLINOIS...WEST CENTRAL ILLINOIS...EAST
CENTRAL IOWA...NORTHEAST IOWA...SOUTHEAST IOWA AND NORTHEAST
MISSOURI.

.DAY ONE...TODAY AND TONIGHT

TODAY...SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE MAINLY THIS
MORNING...ALONG AND NORTH OF I-80.  ANY THUNDERSTORMS ARE NOT
ANTICIPATED TO BE SEVERE.

TONIGHT...A LARGE AREA OF THUNDERSTORMS WILL MOVE ACROSS MOST OF THE
REGION LATE THIS EVENING AND OVERNIGHT. THESE STORMS WILL PRODUCE
LOCALLY HEAVY RAIN WITH RAINFALL RATES OF 2 INCHES AN HOUR OR MORE
POSSIBLE.  WIDESPREAD RAIN TOTALS OF 1 TO 3 INCHES OR MORE IS
EXPECTED DUE TO A TRAINING OF THUNDERSTORMS OVER THE SAME AREA. THIS
HEAVY RAIN COULD FALL ON ALREADY MOIST SOILS ALLOWING FOR THE RISK OF
LOCALIZED FLASH FLOODING. LOCATIONS MOST SUSCEPTIBLE FOR HEAVY RAIN
AND FLASH FLOODING IS NORTH OF I-80 IN IOWA...FOR THIS REASON...A
FLASH FLOOD WATCH IS IN EFFECT FROM 10 PM THIS EVENING INTO FRIDAY
MORNING.

SOME OF THE STRONGEST STORMS LATE THIS EVENING AND OVERNIGHT MAY
ALSO APPROACH OR REACH SEVERE LEVELS WITH LARGE HAIL UP TO THE SIZE
OF NICKELS. STRONG WINDS OF 30 TO 50 MPH ARE ALSO POSSIBLE WITH
ISOLATED DAMAGING WINDS UP TO 60 MPH.  LOCATIONS THAT COULD
EXPERIENCE SEVERE WEATHER ARE PRIMARILY ALONG AND NORTH OF HIGHWAY
34.

THE STORM PREDICTION CENTER HAS A SLIGHT RISK FOR SEVERE
THUNDERSTORMS WEST OF A MANCHESTER TO FAIRFIELD LINE FOR TODAY AND
TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A LARGE THUNDERSTORM COMPLEX WILL DISSIPATE ACROSS THE AREA FRIDAY
MORNING. THERE IS A THREAT OF HEAVY RAIN ALONG AND NORTH OF
INTERSTATE 80. AN ISOLATED STORM MAY BE SEVERE WITH HAIL OR DAMAGING
WINDS.

THUNDERSTORMS WILL REDEVELOP FRIDAY AFTERNOON AND CONTINUE INTO THE
EVENING HOURS. SEVERE STORMS WILL BE POSSIBLE LATE FRIDAY AFTERNOON
AND EVENING. CURRENT INFORMATION SUGGESTS THAT HAIL OR DAMAGING
WINDS WOULD BE THE PRIMARY THREAT. THE AREA MOST AT RISK FRIDAY
AFTERNOON IS SOUTH OF A LINE FROM OTTUMWA IOWA TO STERLING ILLINOIS.

SATURDAY...THERE IS A CHANCE OF THUNDERSTORMS.

THERE IS A DAILY CHANCE OF THUNDERSTORMS MONDAY THROUGH WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS POSSIBLE TONIGHT.   PLEASE REPORT AND SEVERE
WEATHER...HEAVY RAIN AND FLOODING TO THE QUAD CITIES WEATHER FORECAST
OFFICE.

NICHOLS/08

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