Flash Flooding and Hail in Iowa, June 26 to 27, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
402 AM CDT THU JUN 26 2014

.SYNOPSIS...
ISSUED AT 323 AM CDT THU JUN 26 2014

HIGH PRESSURE IS PULLING OFF TO THE EAST AS SOUTHERLY FLOW SETS UP
OVER THE CWA. A STRONG SHORT WAVE WILL LIFT NORTHEAST ACROSS THE
STATE SATURDAY NIGHT. COLD FRONT WILL MOVE THROUGH THE STATE
MONDAY WITH HIGH PRESSURE BUILDING IN FOR THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM /TODAY/...
ISSUED AT 323 AM CDT THU JUN 26 2014

SMALL RIBBON OF THETA-E ADVECTION IN CONJUNCTION WITH SOME WEAK
ISENTROPIC UPGLIDE AND LOW LEVEL INSTABILITY HAS SPAWNED A FEW
ISOLATED THUNDERSTORMS ACROSS CENTRAL PORTION OF THE FORECAST
AREA. UPDRAFTS ARE BARELY TOPPING 30KFT BUT THE WARM LAYER CLOUD
DEPTHS ARE OVER 12KFT AND PRECIPITABLE WATER ARE 1.4 TO 1.6
INCHES. THESE STORMS DO HAVE SOME HEAVY RAIN ASSOCIATED WITH THEM
IN A SHORT PERIOD OF TIME. EXPECTING STORMS TO MIGRATE NORTHEAST
THROUGH 12Z ALONG THE 305-310K ISENTROPIC SURFACE AS THE FORCING
SHIFTS INTO EASTERN IOWA.

ANOTHER WEAK AREA OF LIFT AND THETA-E ADVECTION LOOK TO MOVE INTO
SOUTHWEST IOWA AFTER 12Z AND WILL BRING ANOTHER ROUND OF ISOLATED
THUNDERSTORMS THROUGH MIDDAY BEFORE DAYTIME HEATING ALLOWS FOR POP-
UP THUNDERSTORM ACTIVITY ACROSS THE FORECAST AREA THIS AFTERNOON.
LOW CONFIDENCE WITH WIDESPREAD SEVERE WEATHER...BUT WITH THE
INSTABILITY PRESENT AND WEAK SHEAR AVAILABLE...CANNOT RULE OUT A
BRIEF SEVERE WRT TO HAIL.

MAX TEMPS TODAY WENT CLOSE TO MOS GUIDANCE WITH THE STAGNANT MOIST
AIR MASS IN PLACE AND THE SLIGHTLY WARMER START THAN YESTERDAY AND
MOST AREAS ENDED UP BEING ABOVE GUIDANCE FOR MAX TEMPS ON WEDNESDAY.
BUT WITH THE PEPPERED CONVECTION TODAY AND CLOUD COVER...TOUGH TO GO
ANY MORE THAN A DEGREE OR TWO WARMER THAN GUIDANCE.
.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 323 AM CDT THU JUN 26 2014

SCATTERED THUNDERSTORMS WILL BE IN THE FORECAST FOR MOST PERIODS
INTO MONDAY MORNING AS THE COLD FRONT APPROACHES THE STATE. BEST
CHANCES FOR SIGNIFICANT RAINFALL WILL COME WITH THE LLJ SAT AND
SUN NIGHT. PWAT VALUES WILL BE IN THE 2 TO 3 SIGMA RANGE. FURTHER
FLOODING WILL BE POSSIBLE WITH THE LIKELIHOOD OF LOCAL RAINFALL
OF OVER 3 INCHES WITH EACH OF THESE EVENTS. THERE IS CONSIDERABLE
INSTABILITY BOTH NIGHTS WITH 3000 TO 5000 J/KG OF CAPE AVAILABLE.
SUNDAY NIGHT MORE OF A CONCERN FOR SEVERE WEATHER WITH THE EML
HOLDING THINGS DOWN IN THE LATE AFTERNOON...INSTABILITY BEING
HIGHER...AND MID LEVEL LAPSE RATES APPROACHING 8 C. ANOTHER
CONSIDERATION IS THE INCREASING MID LEVEL WIND SPEEDS AS THE
INFLUENCE OF THE UPPER LOW OVER SK AND MB BECOMES A BIGGER FACTOR.

HIGH PRESSURE WILL BUILD SOUTHEAST INTO THE CENTRAL U.S. FOLLOWINGTHE
COLD FRONT WITH A FEW DAYS BREAK FROM ANY RAIN AND TEMPERATURES
NEAR TO A LITTLE BELOW NORMAL.

&&

.AVIATION...26/06Z
ISSUED AT 1141 PM CDT WED JUN 25 2014

STILL EXPECTING CONVECTION TO DEVELOP OVERNIGHT...MAINLY WIDELY
SCT ALONG WEAK SFC BOUNDARY OVER IA NOW AND INCREASING MOISTURE
FIELD ALOFT AT H850 FROM WEST OF AREA TO NEAR KOMA. FORCING
REMAINS LIMITED FOR NOW...BUT WITH INCREASING WEAK LL JET AND MCS
OVER THE PLAINS HEADING EAST...CHANCES FOR -TSRA WILL INCREASE
TOWARD 12Z WEST AND PROGRESS EAST THROUGH THE PERIOD. INSTABILITY
WILL INCREASE DURING THE DAY THUR WHICH WILL KEEP CHANCE CAT POPS
OVER THE FORECAST AREA. STILL SOME UNCERTAINTY ON COVERAGE AND
TIMING...SO WILL CONTINUE WITH VCTS COVERAGE FOR NOW. 12Z PACKAGE
WILL HAVE BETTER IDEA ON TIMING...EVOLUTION OF SYSTEM CROSSING
PLAINS WHICH WILL IMPACT REMAINDER OF PERIOD. /REV

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SYNOPSIS...MS JUN 14
SHORT TERM...PODRAZIK
LONG TERM...MS JUN 14
AVIATION...REV

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
500 AM CDT THU JUN 26 2014

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-271100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-
CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-
APPANOOSE-DAVIS-
500 AM CDT THU JUN 26 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

FLOOD WARNINGS ARE IN EFFECT FOR SOME RIVER BASINS. PLEASE REFER
TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES
FOR FURTHER DETAILS.

SCATTERED THUNDERSTORMS WITH BRIEF PERIODS OF HEAVY RAINFALL ARE
EXPECTED. SEVERE WEATHER IS NOT LIKELY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

ADDITIONAL THUNDERSTORMS ARE POSSIBLE EACH DAY FRIDAY INTO MONDAY.
THERE IS LITTLE RISK OF SEVERE WEATHER BEFORE SATURDAY AFTERNOON.
SEVERE STORMS ARE POSSIBLE SATURDAY NIGHT AND AGAIN SUNDAY NIGHT.
HEAVY RAINFALL IS QUITE POSSIBLE THROUGH THE PERIOD BUT SPECIFIC
THREATS WILL BE BETTER DEFINED IN THE COMING DAYS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED TODAY BUT MAY BE NEEDED AT
TIMES THIS WEEKEND.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
328 AM CDT THU JUN 26 2014

IAZ059-060-073-261100-
DALLAS-POLK-WARREN-
INCLUDING THE CITIES OF...PERRY...WAUKEE...ADEL...DES MOINES...
INDIANOLA...NORWALK...CARLISLE
328 AM CDT THU JUN 26 2014

...QUICK BURSTS OF HEAVY RAIN...

ISOLATED THUNDERSTORMS OVER PORTIONS OF THE DES MOINES METRO AND
SURROUNDING AREAS WILL BE CAPABLE OF PRODUCING HEAVY RAIN IN A FEW
SHORT TIME PERIOD. UP TO AN INCH IN LESS THAN AN HOUR IS POSSIBLE
AND MAY LEAD TO STREET FLOODING AND REDUCED VISIBILITY AT TIMES
DUE TO THE HEAVY RAIN.

KLP