Flash Flood in Iowa, November 3, 2003

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
200 PM CST MON NOV 3 2003

.DISCUSSION...
TWO MAIN ISSUES FOR TONIGHT ARE FZRA/FZDZ THREAT FAR NW COUNTIES AND
HEAVY RAINFALL AND SMALL HAIL REST OF THE CWA.

CURRENT RADAR MOSAIC AND LOCAL 88D SHOWING WELL DEFINED BAND OF
ELEVATED CONVECTION SHIFTING ONLY 20-30 MILES N ALL MORNING LONG.
THIS BAND IS WITHIN THE MINIMUM OF 750 MB LIFTED INDEX WHICH
STRETCHES BACK INTO KS WHERE VALUES DECREASE TO -4. 24 HOUR RAINFALL
OF 1 TO OVER 3 INCHES IS WELL SUPPORTED BY PWAT FEED OVER 1-1.5
INCHES AND SURFACE DEW POINTS IN THE UPPER 60S FLOWING ATOP THE COLD
DOME.   NEXT BAND AROUND OMAHA METRO AREA WILL ARRIVE IN CENTRAL IA
BY 21Z.  ANOTHER BATCH IS FIRING S OF KCNK IN KS WHERE 750 MB LIS
ARE LOWEST AND SHOULD ALSO ENTER IA AND LIKELY EXPAND.  FLASH
FLOODING IS UNLIKELY, WITH MINOR TO MODERATE RISES FORECAST ON AREA
RIVERS WHICH HAVE BEEN RUNNING JUST A TRICKLE.  THE NW PORTION OF
THE CWA IS STILL EXPERIENCING -FZRA OR FZDZ.  DEVELOPING INVERTED
TROF IN CENTRAL AND NC IA SHOULD KEEP NE FLOW TRAJECTORIES AND
FURTHER SUPPORT LOW LEVEL COOLING.  PRESSURE FALL CENTER IN NE IA
SUPPORTS MODEL FORECAST OF WARM FRONT AND LOW TRACK.  KEST STILL
REPORTING FZRA, ALTHOUGH LACK OF RADAR ECHOES INDICATES IT IS MORE
LIKELY FZDZ ATTM.  ALTHOUGH A MARGINAL CASE, AN ADVISORY IS
WARRANTED.  EXPECT FZDZ TO BE DOMINANT PRECIP LATER TONIGHT AS DRY
SLOT WORKS IN AND MID LEVELS CONTINUE TO WARM. WARM SECTOR MAY
ACTUALLY STAY RAINFREE, WITH MOST PRECIP STAYING ELEVATED N OF
BOUNDARY.  EVENTUALLY, CONVECTION MAY BECOME ROOTED IN BOUNDARY
LAYER. THREAT OF SMALL HAIL STILL EXISTS.

SHORTWAVE ON WEDNESDAY DEPICTS SOME DECENT MID-HIGH LEVEL Q-DIV, BUT
WITH LIMITED MOISTURE. SO FOR NOW, WILL PROBABLY HOLD OFF.  WILL
CHECK ISC FIRST.

LATER PERIODS HAVE BEEN COOLED TO REFLECT LATEST ENSEMBLE /
OPERATIONAL GFS RUNS WITH SURFACE HIGH AND COLD AIR DROPPING EVEN
FURTHER S.  HAVE DELAYED PRECIP UNTIL SUNDAY WHEN WARM ADVECTION
ENTERS REGION AS HIGH BREAKS DOWN.  STILL LOW CONFIDENCE ON TIMING
ESPECIALLY WITH PACIFIC SYSTEM CUTTING OFF.
&&

.DMX...WATCHES/WARNINGS/ADVISORIES...WINTER WEATEHR ADVISORY TONIGHT
NW OF KMCW-POCAHONTAS LINE.

&&

KULA

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-041200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
548 AM CST MON NOV 3 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

RAIN AND SCATTERED THUNDERSTORMS WILL BE WIDESPREAD ACROSS THE AREA
TODAY AND TONIGHT.  THE PRECIPITATION WILL COME IN 2 MAIN WAVES.
THE FIRST WILL BE THIS MORNING WITH THE INTENSITIES DIMINISHING FROM
SOUTHWEST TO NORTHEAST BY NOON.  ANOTHER WAVE OF RAIN AND
THUNDERSTORMS IS EXPECTED TO BEGIN BY THE MID EVENING HOURS.  IN
ADDITION...PRECIPITATION WILL TAKE THE FORM OF MIXED
RAIN...SLEET...SNOW...AND SOME FREEZING RAIN THIS MORNING NORTHWEST
OF A DENISON TO MASON CITY LINE.  THIS WILL CAUSE SOME SLIPPERY
DRIVING CONDITIONS INTO THE MID MORNING HOURS.

THE ONLY THREAT FROM THE THUNDERSTORMS THIS MORNING WILL BE THE
LIGHTNING.  THE NEXT ROUND WILL PRODUCE LIGHTNING AND MAY PRODUCE
SOME SMALL HAIL DURING THE OVERNIGHT HOURS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A LOW PRESSURE AREA WILL LIFT NORTHEAST THROUGH IOWA DURING THE DAY
TUESDAY ALONG A STATIONARY FRONTAL BOUNDARY.  AS THE LOW
PASSES...THE FRONT WILL MOVE SOUTHEAST AS A COLD FRONT.
THUNDERSTORMS WILL BE ONGOING TUESDAY MORNING.  THE WILL OCCUR AHEAD
OF THE LOW AND AHEAD OF THE COLD FRONT.  THE THUNDERSTORMS WILL END
FROM WEST TO EAST BY TUESDAY EVENING WITH THE PASSAGE OF THE FRONT.
THE PRIMARY THREAT FROM THE THUNDERSTORMS WILL BE LIGHTNING AND SOME
SMALL HAIL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

&&

MORE INFORMATION CAN BE OBTAINED AT WWW.CRH.NOAA.GOV/DMX (ALL LOWER
CASE).