Severe Thunderstorm Warning 76, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
252 AM CDT FRI JUN 18 2010

.DISCUSSION...TODAY THROUGH THURSDAY...
...SEVERE WEATHER AND HEAVY RAINFALL APPEAR POSSIBLE THIS
AFTERNOON...AND THIS EVENING...
HOWEVER...THE EXACT DETAILS OF ANY POTENTIAL EVENT ARE NOT TOTALLY
CERTAIN AS IT WILL BE STRONGLY INFLUENCED BY MESOSCALE FEATURES LEFT
FROM THIS MORNINGS MCS.  SYNOPTICALLY...A SEVERE WEATHER EVENT SEEMS
IN THE OFFING AS LONG AS WE BUILD SUFFICIENT CAPE AND CAN KEEP WINDS
BACKED AHEAD OF THE FRONT.  IN ALL LIKELIHOOD THE CURRENT MCS SHOULD
ASSIST IN KEEPING WINDS BACKED...BUT IT POTENTIALLY COULD ROB CAPE
VALUES KEEPING THE POTENTIAL EVENT INTO A MUCH LOWER MAGNITUDE.

THAT ALL SAID...THE CURRENT MCS SEEMS TO HAVE HIT A WALL OVER THE
IOWA AND MISSOURI BORDER.  LOOKING AT THE CURRENT EVOLUTION...IT
APPEARS THAT THE MCS SHOULD PROPAGATE INTO NORTHEAST MISSOURI AND
WEST CENTRAL ILLINOIS THIS MORNING BEFORE DISSIPATING.  ANOTHER AREA
OF DEVELOPING STORMS IS FOUND IN CENTRAL NEBRASKA....WHERE THE LLJ
IS INTERSECTING THE 850MB BOUNDARY.  THIS MAY LIGHT UP FURTHER
BEFORE DAWN...AND COULD BE ANOTHER CAPE ROBBING MECHANISM. DESPITE
THE TWO AREAS OF CAPE KILLING CONCERN...IT DOES APPEAR THAT AT LEAST
SEVERAL HOURS OF PREFRONTAL HEATING WILL OCCUR. THUS...THE LATE
AFTERNOON THROUGH MID EVENING COLD FROPA WITH GOOD DYNAMICS CARRIES
A LIKELY CHANCE OF STRONG TO SEVERE CONVECTION.
INITIALLY...SUPERCELLS SHOULD FORM ALONG THE FRONT...ALONG AND NORTH
OF THE OUTFLOW BOUNDARY.  THIS WILL CARRY A TORNADO THREAT...AS WELL
AS WIND AND HAIL. BY EARLY EVENING...A LINEAR STORM MODE IS
FAVORED...WITH WIND BEING THE MAIN THREAT UNTIL THE LINE EXITS THE
EASTERN CWA LATE IN THE EVENING. AFTER MIDNIGHT...SOME SCATTERED
STORMS MAY FIRE ABOVE THE COLD POOL...BUT THIS THREAT APPEARS LOW AT
THIS TIME.

THE FORECAST IS DOMINATED BY A HIGH POTENTIAL FOR HEAVY
RAINFALL...FLASH AND RIVER FLOODING...AND SEVERE RISK THROUGHOUT.
THIS IS A VERY SIMILAR SCENARIO PAINTED BY PREVIOUS AFD ISSUANCES.
DUE TO THE CURRENT MCS...WE WILL LEAVE THE FORECAST AS IS...WHICH IS
EXTREMELY WET AND STORMY.   THIS PERIOD WILL BE ADDRESSED STRONGLY
IN THE HWO PRODUCT.

SINCE THE DEVELOPMENT OF STORMS IS EXPECTED TO BE PROGRESSIVE
TONIGHT...AND SINCE OVERNIGHT QPF DID NOT APPEAR TOO
HIGH...GENERALLY AROUND 0.5 INCH...A FLASH FLOOD WATCH HAS NOT BEEN
ISSUED.  THAT SAID...TODAY AND TONIGHTS STORMS COULD POSE A RAPID
RUN OFF FLASH FLOOD THREAT THAT COULD OVER WHELM STORM DRAINS IN ANY
URBAN LOCATION...AND THAT WILL NEED TO BE WATCHED CLOSELY.
...ERVIN...
&&

.AVIATION...
CURRENT MCS OVER THE AREA IS SLOWLY DECAYING. BOUNDARIES FROM MCS
WILL LIKELY CAUSE CONVECTION TO PERSIST THROUGH 14-15Z BEFORE
ENDING. VSBYS 3-5SM WITH VCTS POSSIBLE WITH CIGS 2-3KFT AT WORST.
NEW CONVECTION TO FIRE ALONG/AHEAD THE COLD FRONT AFT 18Z. ALL TAF
SITES WILL BE AFFECTED WITH THE MOST LIKELY TIME PERIOD BEING 22Z/18
THROUGH 05Z/19. DURING THIS TIME PERIOD EXPECT VCTS WITH TSRA
LIKELY. VSBYS OF 3-5SM WITH ARND 1SM IN HEAVIER TSRA. CIGS JUST ABV
3KFT BUT 1-2KFT CIGS LIKELY IN TSRA. VFR CONDITIONS AFT 06Z/19.
...08...

&&

.HYDROLOGY...
ANOTHER HEAVY RAIN EVENT WILL IMPACT THE AREA THIS AFTERNOON AND
TONIGHT WITH ANOTHER HEAVY RAIN EVENT SUNDAY.  SEVERAL MORE APPEAR
POSSIBLE BEYOND.

THE EXACT IMPACT TO AREA WATERWAYS IS NOT FULLY KNOWN BUT MODERATE
TO SIGNIFICANT ADDITIONAL RISES WILL OCCUR. FLOODING ON SMALLER
TRIBUTARY RIVERS IS LIKELY. EMERGENCY MANAGERS AND ANYONE LIVING
NEAR OR WITH INTERESTS ALONG AREA RIVERS AND STREAMS SHOULD PAY
ATTENTION TO BOTH WEATHER AND RIVER FORECASTS OVER THE NEXT 7
DAYS.    ...ERVIN...

&&

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

&&

ERVIN/08

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
914 AM CDT FRI JUN 18 2010

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-191415-
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-
914 AM CDT FRI JUN 18 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

THE STORM PREDICTION CENTER IS FORECASTING A MODERATE RISK FOR SEVERE
THUNDERSTORMS OVER MUCH OF THE OUTLOOK AREA TODAY AND TONIGHT. A
COLD FRONT WILL MOVE THROUGH THE REGION THROUGH TONIGHT...AND IS
LIKELY TO PRODUCE ANOTHER ROUND OF STRONG TO SEVERE THUNDERSTORMS.
AS TEMPERATURES RISE TO THE UPPER 80S TO LOWER 90S...THE COLD
FRONT WILL SWEEP INTO THE AREA. A LINE OF SEVERE THUNDERSTORMS
WILL MOVE ACROSS THE OUTLOOK AREA LATE THIS MORNING AND AFTERNOON.
DAMAGING WINDS OF 60 TO 70 MPH CAN BE EXPECTED. SUPERCELL
THUNDERSTORMS MAY ALSO FORM THIS AFTERNOON...WITH THE THREAT OF
ISOLATED TORNADOES...LARGE HAIL...AND DAMAGING WINDS. THIS IS
EXPECTED MAINLY OVER NORTHEAST IOWA. BY EARLY EVENING...THE
STORMS ARE EXPECTED TO MERGE INTO ANOTHER LINE...WITH A THREAT OF HEAVY
RAINFALL AND DAMAGING WINDS OVER ALL OF THE OUTLOOK AREA.

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

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

MANY ADDITIONAL ROUNDS OF STRONG TO SEVERE THUNDERSTORMS WITH
HEAVY RAINFALL ARE EXPECTED OVER THE OUTLOOK AREA THIS WEEKEND AND
UPCOMING WEEK. A NEAR DAILY THREAT OF FLASH FLOODING...AND
INCREASING RIVER FLOODING IS EXPECTED. IN ADDITION...AREAS SOUTH
OF INTERSTATE 80 MAY EXPERIENCE HEAT INDEX READINGS OVER 100
DEGREES MONDAY THROUGH THURSDAY.

.SPOTTER INFORMATION STATEMENT...

AN EMERGENCY MANAGERS CONFERENCE CALL WILL BE CONDUCTED AT 1030 AM
THIS MORNING FOR ALL COUNTIES.

SPOTTER ACTIVATION WILL BE REQUIRED TODAY AND TONIGHT.

HAASE

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