Flood in Iowa, June 17 to 27, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
337 AM CDT THU JUN 17 2010

.SYNOPSIS...
SFC HIGH WAS CENTERED OVER THE GREAT LAKES AT 06Z WITH RIDGE AXIS
EXTENDING THROUGH EASTERN HALF OF CWA. NEAR CALM WINDS AND
INCREASE IN MOISTURE WITH SFC DEWPTS IN THE L60S RESULTING IN
SOME AREAS OF FOG MAINLY ALONG AND E OF MISSISSIPPI RVR INTO NW IL.
00Z UPPER AIR ANALYSIS AND WATER VAPOR SHOW WEAK IMPULSE OVER MO
MOVING E ACCOMPANIED BY SCT SHRA/TSRA. POTENT SHORTWAVE TROUGH
WAS BEGINNING TO EJECT OUT OF GREAT BASIN WITH SFC CYCLONE
DEEPENING OVER PORTIONS OF SE MT AND WRN SD. STRONG DIFFLUENT
FLOW AND WARM/MOIST ADVECTION ON 40-50+ KT LLJ AIDING SEVERAL STRONG
TO STORM CLUSTERS OVER THE DAKOTAS.  ..05..

&&

.SHORT TERM...TODAY AND TONIGHT...
MAIN CONCERNS WITH PCPN CHCS AND SEVERE WX AND HEAVY RAIN/FLASH
FLOOD POTENTIAL TNGT.

SFC RIDGE AXIS WILL CONTINUE TO SLIDE E THIS AM WITH MOISTURE
INCREASING ON STRENGTHENING/GUSTY SLY LLVL WINDS ON BACKSIDE.
SMALL PCPN CHCS EXIST TODAY IN BROAD WARM...MOIST ADVECTION...
MAINLY S SECTIONS THIS AM IN CLOSE PROXIMITY TO MO IMPULSE AND
THEN MAINLY W SECTIONS THIS AFTN WITH APPROACH OF WHAT APPEARS
TO BE WEAK IMPULSE OVER NE EARLY THIS AM PER WATER VAPOR IMAGE.
PROGGED LLVL THICKNESS AND VERIFICATION FROM HIGHS ON WEDNESDAY
SUPPORTS WIDESPREAD M/U 80S FOR MAXES WITH 90-94F IN FAVORED WARM
SITES SOUTH.

THIS AFTN/EARLY EVE EXPECT SEVERE WX OUTBREAK OVER PORTIONS
OF NORTHERN PLAINS INTO UPPER MIDWEST AHEAD OF APPROACHING POTENT
SHORTWAVE TROUGH AND OCCLUDING SFC LOW... WITH SFC BASED ACTIVITY
BUILDING SWD INTO IA IN STRONG INSTABILITY WITH MLCAPES OF
2000-3500 J/KG IN ADVANCE OF DRY LINE BULGE AND TRIPLE POINT.
VARIOUS TOOLS AND TECHNIQUES SUGGEST UPSCALE GROWTH TO MCS WHICH
WILL LIKELY PROPAGATE ACROSS THE AREA... WITH SUGGESTIONS OF
NEAR MATURE STAGE ENTERING N/W SECTIONS THIS EVE BEFORE GRADUAL
WEAKENING WHILE MOVING S/SE. SPC SWODY1 LOOKS REASONABLE.
MAIN THREAT WILL BE DAMAGING STRAIGHT LINE WINDS OF 60-70+ MPH.
CONCERNED THAT QUITE VULNERABLE TO WIDESPREAD AND POTENTIALLY
SIGNIFICANT TREE DAMAGE WITH ANY HIGH WINDS GIVEN ROOT STRUCTURES
WEAKENED WITH GROUND SO SATURATED. HAVE RAISED POPS INTO LIKELY
CAT NORTH 1/2... BUT NAM AND ECM SUGGEST MOST IF NOT ALL AREA TO
SEE RAIN AND THUS LATER SHIFTS MAY NEED TO RAISE POPS FURTHER ALL
AREAS. ALSO... FLASH FLOODING WILL BE A SIGNIFICANT CONCERN WITH
HEAVY RAINFALL RATES IN EXCESS OF 1-2 IN/HR GIVEN PWATS OF
NEARLY 2 INCHES. HEAVIEST QPF MOST LIKELY TO FOCUS PORTIONS
OF AREA NORTH OF I-80 WHERE 1HR/3HR FFG VALUES ARE GENERALLY ON
THE ORDER OF 1.5-2 INCHES... AND THIS AREA MORE ABLE TO HANDLE
THIS RAIN COMPARED WITH THE SOUTHERN COUNTIES. SPEED OF SYSTEM IF
ORGANIZED MCS WITH COLD POOL MAY CUT DOWN SOME ON QPF AND
POTENTIAL FOR WIDESPREAD FLASH FLOODING. EXPECT WEAKENING OF
SYSTEM AS IT MOVES SOUTH ACROSS THE AREA... BUT STILL CONCERNS IN
THE SOUTH FOR FLASH FLOODING ESPECIALLY WITH VEERED 30+ KT LLJ AND
IF COLD POOL FOR CONTINUED DEVELOPMENT. ENOUGH UNCERTAINTY WITH
MAGNITUDE AND PLACEMENT OF QPF TO HOLD OFF ON FLASH FLOOD WATCH
FOR NOW BUT WILL CONTINUE TO HIGHLIGHT IN HWO AND GRAPHICAL WX
STORY.   ..05..

.LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY...
FRIDAY...ASSESSING THE NEW 00Z RUN MODELS AND SCENARIOS...NOT MUCH
CHANGE FROM PREVIOUS SHIFT/S THINKING ABOUT THIS POTENTIALLY
VOLATILE PERIOD. EXPECT THU NIGHT REMNANT CONVECTIVE DEBRIS AND
OUTFLOWS TO CONTINUE TO ROLL THROUGH THE CWA FRI MORNING...THEN
AIRMASS RECOVERY COMMENCES BY AFTERNOON. IF THIS DEBRIS CAN EXIT
OR DISSIPATE IN TIME FOR THE LOCAL COLUMN TO HEAT UP TO AROUND 90
DEGREES OR LOW 90S WITH DPTS INCREASING INTO THE LOW TO MID 70S...
SBCAPES WILL GROW OVER 3K J/KG AND PROBABLY ECLIPSE THE 4K J/KG MARK
BY LATE AFTERNOON ACRS MUCH OF THE DVN CWA. HEAT INDICES MAY GET
CLOSE TO LOW END HEAT ADVISORY CRITERIA ESPECIALLY SOUTH OF I80 FRI
AFTERNOON. EXPECT AFTERNOON CONVECTIVE DEVELOPMENT TO TAKE OFF ALONG
NORTHWEST GRADIENT FLANK OF THE LOCAL DEEP CONVECTIVE INDEX POOL AND
VERTICAL THTA-E GRADIENT GENERALLY FROM JUST NORTHWEST OF THE DSM
AREA...NORTHEASTWARD TOWARD NORTH CENTRAL WI IN VCNTY OF INCOMING
FRONT. MANY FACTORS SUCH AS EXTENT OF SHEAR ON EDGE OF HIGH CAPE
ENVIRONMENT SUGGEST SUPERCELLULAR DEVELOPMENT IN THESE AREAS JUST
NORTHWEST OF THE LOCAL CWA...WITH SOME OF THEM MAKING THEIR WAY INTO
THE CWA BY FRI EVENING WITH AN ASSOCIATED LARGE HAIL...DAMAGING WIND
AND TORNADO THREAT. BUT BULK OF THE INCOMING EVENTUAL STORM COMPLEX
WOULD TRANSLATE INTO A WIDESPREAD DAMAGING WIND AND HEAVY RAIN
MACHINE ERODING WEAK CAP IN PLACE OVER THE AREA AND SPREADING/FEEDING
SOUTHEASTWARD OVER MOST OF THE DVN CWA THROUGH LATE FRI EVENING.
ALTHOUGH CURRENT INDICATIONS SUGGEST STRAIGHT LINE WINDS OF AT LEAST
80 MPH POSSIBLE FRI AFTERNOON/EVENING...STILL TIME TO GET CLOSER TO
THE EVENT TO ASSESS IN MORE DETAIL THE TRUE SVR THREAT.

SATURDAY...LATEST 00Z RUM MEDIUM RANGE GUIDANCE TRENDING TOWARD SAT
ACTUALLY BEING A LULL DAY IN WAKE OF FRI NIGHT MCS. CONVECTIVE
DEBRIS AND OUTFLOW TO LINGERING MORNING WITH MAIN LLVL BOUNDARY/
FRONT GETTING SHUNTED FROM WEST-TO-EAST JUST SOUTH OF THE DVN CWA
UNDER BROAD BUT AMPLIFYING MID AND UPPER RIDGE PATTERN ACRS THE
CENTRAL CONUS. WILL STILL KEEP LOW TO MODERATE CHC POPS FOR NOW
ESPECIALLY IN THE SOUTHERN CWA IN EXPECTED VCNTY OF OUTFLOWS OR MAIN
FRONTAL PLACEMENT. WARM UP ON SAT DEPENDENT ON DEBRIS CLEAR OUT...
BUT POTENTIAL FOR ANOTHER VERY WARM AND STICKY DAY CONTINUES.
EXTRAPOLATING MEAN EDGE OF STEERING RIDGE/STORM TRACK...ANY RIDGE-
RIDING WAVE WOULD IGNITE A STORM COMPLEX ACRS THE CENTRAL PLAINS SAT
NIGHT WITH THE POTENTIAL OF THIS SYSTEM TO THEN PROPAGATE EASTWARD
ACRS IA TOWARD THE DVN CWA BY LATE SAT NIGHT OR SUNDAY MORNING. PW/S
OF 1.8 TO 2 INCHES SUGGEST FLOODING RAINS THE MAIN THREAT IF THIS
SYSTEM COMES ACRS LATE ENOUGH AS OPPOSED TO WIDESPREAD SVR STORMS.

SUNDAY INTO MONDAY...LATEST GUIDANCE RUNS ARE STILL OMINOUS AND PAINT
A STORMY WINDOW THIS PERIOD AS THE DVN CWA TO BE UNDER THE MCS GUN.
COMPOUNDED HEAVY RAIN EVENTS MAY TRANSLATE INTO SOME SERIOUS RIVER
ISSUES BY THE START OF NEXT WEEK...BUT MUCH WILL DEPEND ON WHERE
THE STORMS CAN TRACK AND IF THERE WILL BE REPEATED PATHWAYS/TRAINING.
LARGE TEMPERATURE GRADIENTS POSSIBLE FROM NORTH TO SOUTH...WITH THE
SOUTH STEAMY AND NEAR HEAT ADVISORY CRITERIA WHILE THE NORTH MAY
CONTINUED TO BE IMPACTED BY CONVECTIVE DEBRIS/COOL POOL OUTFLOWS.
LITTLE CHANGE NEEDED TO ONGOING GRIDS FROM SUNDAY ON. THE EURO
STILL PAINTS A PICTURE OF THE HEAT DOME/UPPER RIDGE AMPLIFYING
ENOUGH ACRS THE MS RVR VALLEY TO SHUNT THE MAIN STORM TRACK/RING OF
FIRE NORTH OF THE REGION ACRS THE DAKOTAS...MN AND INTO THE
NORTHWESTERN GRT LKS BY MID WEEK. ALTHOUGH THIS WOULD BRING MUCH
NEEDED RELIEF FROM SVR STORMS AND FLOODING RAINS...THE AREA WOULD
LIKELY BE BATHED IN HEAT ADVISORY CRITERIA.      ..12..

&&

.AVIATION...
VFR CONDITIONS EXPECTED TODAY WITH GUSTY S/SE WINDS DEVELOPING ON
BACKSIDE OF DEPARTING HIGH PRESSURE. SMALL SHRA/TSRA CHCS EXIST
TODAY IN BROAD WARM ADVECTION REGIME AHEAD OF POTENT WESTERN
TROUGH... BUT CONFIDENCE ON IMPACTING TERMINALS TOO LOW TO WARRANT
MENTION ATTIM. TNGT... STRONG TO POTENTIALLY SEVERE CONVECTIVE
SYSTEM LIKELY TO IMPACT THE REGION WITH MAIN THREAT DAMAGING WINDS.
EXPECT MVFR TO IFR CONDITIONS WITH SHRA/TSRA AND GUSTY WINDS
ARRIVING AT MOST TERMINALS THIS EVE AND LINGERING FOR A PERIOD
OVRNGT.   ..05..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

05/12

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
516 AM CDT THU JUN 17 2010

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-181030-
BUCHANAN-DELAWARE-DUBUQUE-BENTON-LINN-JONES-JACKSON-IOWA-JOHNSON-
CEDAR-CLINTON-MUSCATINE-SCOTT-KEOKUK-WASHINGTON-LOUISA-JEFFERSON-
HENRY IA-DES MOINES-VAN BUREN-LEE-JO DAVIESS-STEPHENSON-CARROLL-
WHITESIDE-ROCK ISLAND-HENRY IL-BUREAU-PUTNAM-MERCER-HENDERSON-
WARREN-HANCOCK-MCDONOUGH-SCOTLAND-CLARK-
516 AM CDT THU JUN 17 2010

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

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING NORTHWEST OF A LINE FROM DUBUQUE
IOWA TO WASHINGTON IOWA... AND A SLIGHT RISK FOR THE REST
OF EASTERN IOWA AND FAR NORTHWEST ILLINOIS.

ISOLATED TO WIDELY THUNDERSTORMS WILL BE POSSIBLE THIS
MORNING AND EARLY AFTERNOON MAINLY WEST OF THE MISSISSIPPI
RIVER. THESE STORMS ARE NOT EXPECTED TO BE SEVERE.

LATE THIS AFTERNOON AND EVENING... SEVERE THUNDERSTORMS
OVER THE NORTHERN PLAINS AND UPPER MIDWEST ARE EXPECTED
TO DEVELOP INTO A LARGE COMPLEX AND MOVE SOUTHEAST ACROSS
PORTIONS OF THE OUTLOOK AREA. THE PRIMARY THREAT WITH
THESE STORMS WILL BE DAMAGING WINDS OF 60 TO 80 MPH...
MAINLY OVER PORTIONS OF EASTERN IOWA... WITH LARGE HAIL
AROUND THE SIZE OF QUARTERS ALSO POSSIBLE. IN ADDITION...
HEAVY RAINFALL IN EXCESS OF AN INCH WILL BE POSSIBLE
BRINGING A RISK OF FLASH FLOODING.

AREA RIVERS ARE EXPERIENCING FLOODING. PLEASE SEE THE LATEST
FLOOD STATEMENTS AND FLOOD WARNINGS FOR DETAILS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A FRONTAL SYSTEM PUSHING INTO A VERY WARM AND HUMID AIRMASS
ACROSS THE REGION WILL IGNITE STRONG TO SEVERE THUNDERSTORMS
IN OR NEAR THE OUTLOOK AREA FRIDAY AFTERNOON AND EVENING.
INDIVIDUAL STORM CELLS MAY BE ABLE TO PRODUCE LARGE
HAIL...DAMAGING WINDS AND EVEN A FEW TORNADOES BY LATE
FRIDAY AFTERNOON NORTHWEST OF A LINE FROM IOWA CITY...TO
DUBUQUE. THESE INDIVIDUAL STORMS ARE THEN EXPECTED TO BECOME
A LARGER COMPLEX OF STORMS PRODUCING DAMAGING STRAIGHT LINE
WINDS AS THEY SPREAD ACROSS THE REST OF THE AREA THROUGH
FRIDAY NIGHT. THESE STORMS WILL ALSO HAVE THE POTENTIAL TO
PRODUCE LOCALLY HEAVY RAIN AND FLASH FLOODING. THE STORM
PREDICTION CENTER HAS PLACED THE ENTIRE AREA UNDER A SLIGHT
RISK OF SEVERE WEATHER FRIDAY AND FRIDAY NIGHT. BEFORE THE STORMS
ARRIVE...TEMPERATURES AROUND 90 DEGREES WITH HIGH HUMIDITY WILL
PRODUCE VERY UNCOMFORTABLE HEAT INDICES IN THE MID TO UPPER 90S.

PORTIONS OF THE OUTLOOK AREA WILL CONTINUE TO BE UNDER THE GUN
FOR MORE ROUNDS OF THUNDERSTORMS FROM SATURDAY THROUGH AT LEAST
NEXT MONDAY. MUCH WILL DEPEND ON WHERE A WEST-TO-EAST ORIENTED
FRONTAL BOUNDARY ALIGNS ITSELF DURING THIS PERIOD THAT WILL ALLOW
CERTAIN AREAS TO EXPERIENCE MORE THUNDERSTORM ACTIVITY THAN
OTHERS. WITH A VERY WARM AND HUMID AIRMASS REESTABLISHING ACROSS
THE REGION THROUGH THE WEEKEND...SOME STORMS MAY BECOME SEVERE
WITH DAMAGING WINDS BEING THE PRIMARY THREAT. ALSO...THESE
THUNDERSTORM COMPLEXES WILL PRODUCE VERY HEAVY RAINFALL AND MAKE
AREAS SUSCEPTIBLE TO FLASH FLOODING. REPEATED ROUNDS OF HEAVY
RAINFALL THROUGH EARLY NEXT WEEK WILL AGGRAVATE ONGOING RIVER
FLOODING SITUATIONS...OR CREATE NEW ONES.

STAY TUNED FOR FURTHER UPDATES AND FORECASTS WHICH WILL BETTER
DEFINE AREAS THAT WILL BE MORE SUSCEPTIBLE TO SEVERE WEATHER OR
FLOODING RAINS THROUGH UPCOMING WEEKEND.

.SPOTTER INFORMATION STATEMENT...

AN EMERGENCY MANAGERS CONFERENCE CALL WILL LIKELY BE SCHEDULED
FOR PORTIONS OF THE OUTLOOK AREA LATER THIS MORNING.

SPOTTER ACTIVATION WILL LIKELY BE NEEDED THIS EVENING... AND IS
POSSIBLE AGAIN FRIDAY AFTERNOON AND EVENING.