Hail in Iowa, April 4, 2010

AREA FORECAST DISCUSSION...CORRECTED WORDING
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
342 AM CDT SUN APR 4 2010

.SYNOPSIS...
FAST ZONAL FLOW ALOFT PREVAILS OVER THE CENTRAL AND WESTERN CONUS
TONIGHT WITH ONE SHORTWAVE SEEN ON WV IMAGERY MOVING ACROSS SOUTHERN
MN AND ANOTHER LARGER WAVE MOVING INTO THE CENTRAL ROCKIES. AT THE
SURFACE...THE MN WAVE WAS PRODUCING A WEAK LOW OVER FAR NE SD WITH A
COLD FRONT TRAILING SOUTH ACROSS NEB INTO CENTRAL KS. AS EVIDENT IN
THE 00Z DVN AND NEIGHBORING SOUNDINGS...LOW AND MID LEVEL
MOISTURE WAS RATHER MEAGER ACROSS THE REGION AND ONLY WEAK HIGH
BASED SHOWERS WERE SEEN ON AREA 88DS AND SURFACE REPORTS CONFINED TO
JUST EAST AND N OF THE NRN PLAINS SYSTEM. A 50 TO 60KT SWRLY LOW
LEVEL JET ACROSS THE CENTRAL AND SOUTHERN PLAINS HAD YET TO TAP INTO
GULF MOISTURE...WHICH WAS LIMITED TO THE TX GREAT BEND REGION ON THE
00Z H8 ANALYSIS.

&&

.SHORT TERM...TODAY AND TONIGHT...
MAIN FOCUS IS ON THUNDERSTORM DEVELOPMENT LATER TODAY AND POTENTIAL
FOR SEVERE STORMS. FACTORS APPEAR TO BE COMING TOGETHER FOR
THUNDERSTORM DEVELOPMENT IN THE MID TO LATE AFTERNOON HOURS OVER THE
FORECAST AREA. THE FAST MID LEVEL FLOW IS PROGGED TO DRIVE THE
ROCKIES SHORTWAVE EAST INTO WESTERN IA BY 00Z. AHEAD OF THIS...A
DEVELOPING WEAK WARM FRONT ACROSS KS INTO SW MO EARLY THIS MORNING
WILL BE DRAWN NORTHWARD ALONG THE ADVANCING COLD FRONT RESULTING IN
A WEAK TRIPLE POINT INDICATED BY ESPECIALLY THE WRF/NAM OVER W
CENTRAL IL BY 00Z. AT THE SAME TIME...H8 MOISTURE IS SHOWN RAPIDLY
SPREADING NE ACROSS THE CENTRAL PLAINS INTO THE FORECAST AREA. WHILE
LOW LEVEL MOISTURE RETURN...WITH DEWPOINTS NOT LIKELY EXCEEDING THE
LOWER 50S...WILL BE A LIMITING FACTOR FOR SEVERE STORMS....OTHER
FACTORS INCLUDING STRONG MID AND UPPER LEVEL WINDS AND RESULTING
BULK SHEAR...AND MID LEVEL INSTABILITY WILL RESULT IN A THREAT OF
SEVERE STORMS OVER THE AREA AND SPC HAS A SLIGHT RISK OVER THE SE.
THE MAIN THREAT LOOKS TO BE DAMAGING WIND AND LOW END LARGE HAIL.

CURRENT MODEL TIMING HAS THE ADVANCING COLD FRONT ROUGHLY ALONG THE
MS RIVER AT 00Z AND HAVE KEPT LATE AFTERNOON CHANCE POPS OVER ALL
BUT THE FAR NW...THEN CHANCE TO LIKELY POPS ACROSS THE SE THIS
EVENING. CURRENT TIMING OF THE SURFACE FEATURES AND UPPER SHORTWAVE
SHOULD DRIVE ALL THUNDERSTORMS EAST OF THE AREA BY MIDNIGHT AND HAVE
REMOVED POPS AFTER 06Z.

DEEPER MIXING TO AT LEAST H8 SHOULD WARM TEMPERATURES INTO THE UPPER
60S NW TO MID 70S SE TODAY WITH THICKENING MID AND UPPER CLOUDS
AHEAD OF THE SHORTWAVE MID TO LATE AFTERNOON BEFORE THUNDERSTORMS
DEVELOP. TONIGHT...CURRENT AIRMASS WITH TEMPERATURES IN THE 30S
BEHIND THE FRONT IN THE PLAINS WILL OVERSPREAD THE AREA AND WITH
SOME MODIFICATION AND LIGHT WEST WINDS HAVE GONE WITH MINS NO LOWER
THAN THE 40S FOR NOW.
..SHEETS..

.LONG TERM...MONDAY THROUGH SATURDAY...
MAIN CONCERN IN THIS TIME FRAME IS SEVERE WEATHER CHANCES EARLY THIS
WEEK.  MODELS ARE FAIRLY SIMILAR THROUGH EARLY TUESDAY THEN DIVERGE
FOR THE REST OF THE WEEK.

MODELS AGREE IS RETURNING THE FRONTAL BOUNDARY NORTHWARD MONDAY WITH
THE NAM FURTHEST SOUTH...GFS FURTHEST NORTH...AND ECM IN BETWEEN.
POPS ARE LOW DURING THE MORNING HOURS WITH THE FRONT WELL TO OUR
SOUTH...BUT INCREASE DURING THE AFTERNOON WITH SOLAR HEATING AND THE
ADVANCING BOUNDARY.

THE SEVERE POTENTIAL IS TIED TO NEAR THE SURFACE FRONT WHERE
FAVORABLE LOW-LEVEL CONVERGENCE WILL INITIATE STORMS.  SHEAR WILL BE
HIGH...SO INSTABILITY IS THE LIMITING FACTOR WITH THE AMOUNT OF
SUNSHINE CRITICAL.  SOUNDINGS SUGGEST SUPERCELL TYPE STORMS WITH
BOTH TORNADOES AND HAIL AS POSSIBLE THREATS GIVEN SUFFICIENT
INSTABILITY.

THE FRONT CONTINUES NORTHWARD THROUGH THE NIGHT AS THE LLJ DEVELOPS
CONTINUING A THREAT OF STORMS.  THE WEST COAST TROUGH BEGINS
SHIFTING EASTWARD INTO THE PLAINS TUESDAY PUSHING THE SURFACE LOW
INTO IOWA.  AFTER NOCTURNAL STORMS SUBSIDE...ANOTHER THREAT OF
STORMS EXISTS WITH THE COLD FRONTAL PASSAGE SOMETIME LATE TUESDAY
OR EARLY WEDNESDAY.

MODELS DIVERGE ON THE TIMING OF THE FRONTAL PASSAGE WITH THE GFS/GEM
THE FASTEST AND NAM/ECM SLOWER.  THIS IS IMPORTANT AS THE LATE
AFTERNOON/EARLY EVENING TIMING OF THE GFS/GEM WOULD MAXIMIZE SOLAR
HEATING.  AND WITH STRONG SHEAR IN PLACE...SOLAR HEATING AND
INSTABILITY WILL AGAIN BE A DETERMINING FACTOR IN THE STORMS
POTENTIAL SEVERITY.  THE NOCTURNAL FRONTAL PASSAGE OF THE NAM/ECMWF
WOULD LESSEN THIS POTENTIAL.

MUCH COOLER AIR PUSHES INTO THE AREA WEDNESDAY THROUGH FRIDAY WITH
RETURN FLOW KICKING BACK IN ON SATURDAY.  DEPENDING ON THE
MODEL...THERE ARE INDICATIONS OF A WEAK WAVE DROPPING THROUGH THE
AREA THURSDAY...BUT HAVE NOT REFLECTED THIS IN THE POPS.  SO...
GENERALLY DRY WEATHER SHOULD PREVAIL LATE WEEK.   WOLF

&&

.AVIATION...
VFR CONDITIONS TO PERSIST THROUGH MID AFTERNOON AT ALL TERMINALS.
STRONG SOUTH WINDS AROUND 40 TO 50KT OFF THE DECK AROUND 1800 TO
2000 FT AGL...OVER S-SE SURFACE WINDS AROUND 10 KTS OF LESS WILL
RESULT IN LOW LEVEL WIND SHEAR CONDITIONS EARLY THIS MORNING. HAVE
LLWS CONDITIONS IN TERMINALS UNTIL AROUND 14Z WHEN SURFACE WINDS
INCREASE AND SHEAR WEAKENS. A COLD FRONT MOVING THROUGH THE AREA
WILL TRIGGER THUNDERSTORMS MAINLY AFTER 21Z. THESE MAY REDUCE CIGS
AND VSBYS MAY DIP INTO MVFR CONDITIONS...AND POSSIBLY PRODUCE
STRONG WINDS AND SMALL HAIL LATE AFTERNOON INTO EARLY EVENING AT MLI
AND BRL.
..SHEETS..

&&

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

SHEETS/WOLF

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
524 AM CDT SUN APR 4 2010

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-051030-
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-
524 AM CDT SUN APR 4 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 CHANCE FOR SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO
EARLY EVENING. THE AREA OF GREATEST POTENTIAL IS ALONG AND SOUTH OF
A LINE FROM FAIRFIELD...THROUGH THE QUAD CITIES...TO PRINCETON
ILLINOIS WHERE THE STORM PREDICTION CENTER HAS PLACED A SLIGHT RISK.
THUNDERSTORMS ARE EXPECTED TO DEVELOP AFTER 3 PM ALONG A COLD FRONT
IN THIS AREA. THE GREATEST SEVERE WEATHER THREATS ARE DAMAGING WIND
GUSTS AND HAIL AROUND 1 INCH IN DIAMETER. STRONG WIND SHEAR MAY LEAD
TO A FEW SUPERCELL THUNDERSTORMS...AND AN ISOLATED TORNADO CANNOT BE
RULED OUT.

WARM TEMPERATURES...STRONG WINDS...LOW RELATIVE HUMIDITIES...AND
DRIED VEGETATION WILL COMBINE TO RESULT IN A VERY HIGH THREAT OF
GRASS FIRES THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A SLOW MOVING UPPER LEVEL TROUGH AND DEVELOPING SURFACE LOW PRESSURE
SYSTEM WILL BE THE FOCUS FOR POTENTIAL SEVERE THUNDERSTORMS MONDAY
THROUGH TUESDAY.

A WARM FRONT WILL MOVE INTO THE AREA MONDAY AND PROVIDE A FOCUS
FOR POTENTIALLY SEVERE THUNDERSTORMS. IF SOLAR HEATING
SUFFICIENTLY DESTABILIZES THE ATMOSPHERE DURING THE AFTERNOON AND
EARLY EVENING...SHEAR WILL BE STRONG ENOUGH TO SUPPORT DEVELOPMENT
OF SUPERCELL THUNDERSTORMS. THE GREATEST SEVERE THREAT WOULD BE
IN CLOSE PROXIMITY TO THE WARM FRONT...AND STORMS COULD BE CAPABLE
OF PRODUCING LARGE HAIL AND TORNADOES.

STORMS WILL CONTINUE OVERNIGHT FUELED BY A STRONG LOW-LEVEL JET.
AS THE SURFACE LOW MOVES CLOSER TO THE AREA TUESDAY...THE SEVERE
WEATHER THREAT WILL RETURN WITH PASSAGE OF THE COLD FRONT. AT THIS
TIME...IT IS UNCLEAR WHETHER THE FRONT WILL MOVE THROUGH THE AREA
LATE TUESDAY AFTERNOON OR OVERNIGHT. IF IT MOVES THROUGH TUESDAY
AFTERNOON AND WE AGAIN GET SUFFICIENT SUNSHINE TO DESTABILIZE THE
ATMOSPHERE...SEVERE THUNDERSTORMS ARE POSSIBLE. IF THE FRONT MOVES
THROUGH OVERNIGHT WITHOUT BENEFIT OF DAYTIME HEATING...THE SEVERE
WEATHER THREAT WOULD BE LOWER.

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS POSSIBLE
DURING THE NEXT THREE DAYS.

SHEETS/WOLF

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1113 AM CDT SUN APR 4 2010

IAZ089-099-ILZ025-026-034-035-041800-
DES MOINES-LEE-HENDERSON-WARREN-HANCOCK-MCDONOUGH-
INCLUDING THE CITIES OF...BURLINGTON...FORT MADISON...OQUAWKA...
MONMOUTH...CARTHAGE...MACOMB
1113 AM CDT SUN APR 4 2010

...ISOLATED THUNDERSTORMS POSSIBLE THROUGH 1 PM...

A FEW SHOWERS AND THUNDERSTORMS WILL LIFT NORTHEAST THROUGH WEST
CENTRAL ILLINOIS THROUGH 1 PM...WITH SMALL HAIL POSSIBLE IN THE
STRONGER STORMS. THESE SHOWERS AND THUNDERSTORMS MAY ALSO IMPACT
THE CITY OF BURLINGTON.

ERVIN