Damaging Winds in Iowa, May 17, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 PM CDT WED MAY 16 2001

COLD FRONT HAS SAGGED TO OUR SE THIS AFTERNOON AND WAS FROM LOW OVER
LAKE MI W-SW TO W CENTRAL KS...WHERE VISIBLE SATELLITE SHOWS
CONVECTION FIRING. MID LEVEL WARM AIR ADVECTION CLOUDS EVIDENT OVER
SE NEB INTO WESTERN IA DEVELOPING AHEAD OF PRESSURE FALLS IN NEB
PANHANDLE AND WRN SD IN RESPONSE TO SHORTWAVE MOVING INTO EASTERN
MT. MAIN FORECAST CHALLENGE IS RAIN CHANCES TONIGHT THROUGH THURSDAY
AS CONVECTIVE SYSTEM MOVES ALONG AND NORTH OF FRONT JUST TO SOUTH OF
FORECAST AREA.

AVN MODEL HAD BEST DEPICTION OF SURFACE FEATURES AT 18Z. NGM HAD QPF
OVER CLEAR AREAS TODAY AND THEN WAS SIMILAR TO ETA IN LATER
PERIODS. ETA HAD FRONTAL POSITION SIMILAR TO AVN THROUGH FRIDAY...
BUT HAD QPF TOO FAR NORTH OF FRONT INTO E CENTRAL IA BY 00Z FRIDAY
AND THUS DISCOUNTED. AVN PERSISTENT WITH INDICATING MCS TO DEVELOP
AND MOVE EAST ALONG AND N OF STALLED FRONT LATE TONIGHT AND EARLY
THURSDAY. WITH CONVECTION ALREADY DEVELOPING OUT WEST CLOSER TO ETA
SOLUTION...WENT ALONG WITH COMPROMISE BETWEEN ETA AND AVN.

VIGOROUS H5 SHORTWAVE MOVING INTO DAKOTAS WILL HELP MCS SYSTEM TO
DEVELOP ALONG FRONT IN NRN KS/SRN NE THIS EVENING. THIS WILL MOVE
RAPIDLY EAST WITH ZONAL FLOW ALOFT TO REACH SW ZONES BEFORE MIDNIGHT
AND SPREAD EAST ACROSS CWFA OVERNIGHT. WENT JUST BELOW AVN/MAV
POPS...WITH LIKELY IN SOUTH AND SCATTERED CENTRAL AND NORTH
OVERNIGHT. SURFACE HIGH PRESSURE WEDGES INTO NW IA FRIDAY...AND WENT
CLOSER TO AVN IN KEEPING ANY CONVECTION THAT MAY FIRE ALONG FRONT TO
IMPACT ONLY SRN ZONES. FRIDAY MUCH COOLER AND DRYER AS SURFACE FLOW
REMAINS NORTHERLY WITH HIGH PRESSURE MOVING OVER IA.

IN EXTENDED WILL ADD THUNDERSTORM CHANCES TO SUNDAY AS NEW AVN HAS
SHORTWAVE MOVING ACROSS AREA WITH SURFACE FRONT PUSHING BACK NORTH.
NO OTHER MAJOR CHANGES ANTICIPATED TO EXTENDED.

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

SHEETS