Severe Thunderstorm Warning 14, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
310 PM CDT THU MAY 11 2000

SHORT TERM...TRIPLE POINT IS STARTING TO SHOW ITS HAND IN THE VSB
IMAGERY...NR SLB OR STORM LAKE. MOST LIKELY INIT AREA SHOULD BE FROM
THAT LOCATION TWDS ALO AND JUST TO THE N. 18Z DSM GOES SOUNDER
SOUNDING CAPE WAS 4200 WITH A CIN OF 100. SPICKARD IS EVEN MORE
INTERESTING BUT NOT REALITY. CU FLD OVRHD IS THICKENING ABIT WITH
RECORD HIGH AT HAND. CAP IS IN PLACE S OF IMAGERY WRMFNT. XPCG
DVLPMT VCNTY TRIPLE PT BTWN 6 TO 9 PM.

LONGER TERM...NEW MESOETA AND MORE SUBTLY THE 12Z ETA DVLPS
CONVECTIVE FEEDBACK OVR ERN IA AND ROLLS IT TWD CHI TNGT. THUS A
COMPLEX SIMILAR TO LAST NGT IS XPD OVR ERN PTN CWA EWD. PUSH OF SFC
NWLY FLOW SLOWS TMR AS UPR SUPPORT LIFTS ACRS MN. MORE CONVECTION
THEN PSBL ACRS SERN IA TMR. CD SURGE ARRIVES FRI NGT AND SAT WITH
SOME THREAT OF SHWRS ACRS NRN CWA AS H8 TMP GOES TO ZERO BY 48HRS
NKRN CWA. OPTTED TO LEAVE OUT OF FCST ATTM. PREV FCST TMPS MATHCED
WELL WITH SUGGESTED NUMBERS. WL NOT XTEND WND ADVISORY.

.DSM...NONE
MYERS

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-112300-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1244 PM CDT THU MAY 11 2000

HAZARD--ISOLATED SEVERE THUNDERSTORMS PRODUCING HAIL UP TO 2 INCHES
IN DIAMETER...DAMAGING WINDS EXCEEDING 60 MPH...AND TORNADOES.

AREA OF CONCERN--NORTH OF HIGHWAY 30 AND EAST OF INTERSTATE 35.

TIMING DETAILS--FROM 5 PM TO MIDNIGHT.

METEOROLOGICAL COMMENTS--VERY WARM AND HUMID AIR IS SURGING NORTHEAST
ACROSS SOUTHWEST IOWA AT MIDDAY AS A LOW PRESSURE AREA NEARS OMAHA.
WINDS HAVE REACHED 40 MPH AT TIMES ALONG THE MISSOURI BORDER AS
DEWPOINTS HAVE RISEN TO AROUND 70 DEGREES. CLOUDS ARE CLEARING
RAPIDLY ACROSS CENTRAL IOWA ALLOWING TEMPERATURES TO JUMP INTO THE
80S. THESE EVENTS ARE DESTABILIZING THE LOWER ATMOSPHERE QUICKLY.
HOWEVER...A STRONG WARM LAYER IN THE MIDDLE LEVELS OF THE ATMOSPHERE
IS PROVIDING A STRONG CAP WHICH WILL LIKELY PREVENT SIGNIFICANT
THUNDERSTORM DEVELOPMENT SOUTH OF HIGHWAY 30 AND POSSIBLY AS FAR
NORTH AS HIGHWAY 20 INTO THE EARLY EVENING. THE MOST LIKELY AREA TO
SEE RAPID THUNDERSTORM INITIATION WILL BE NEAR THE JUNCTION OF THE
LOW PRESSURE AREA AND ATTENDANT COLD AND WARM FRONTS WHICH ARE
FORECAST TO TRAVEL EASTWARD NEAR HIGHWAYS 20 AND 30. THE LOW IS
FORECAST TO BE NEAR CARROLL AT 4 PM...BETWEEN AMES AND IOWA FALLS BY
7 PM AND NEAR WATERLOO BY 10 PM. AFTER SUNDOWN...THUNDERSTORMS MAY
THEN ERUPT FROM NORTHEAST IOWA BACK SOUTHWEST INTO SOUTH CENTRAL OR
SOUTHEAST SECTIONS OF THE STATE AS THE CAP WEAKENS SOMEWHAT
OVERNIGHT.

SPOTTER ACTIONS--SKYWARN AND AMATEUR RADIO SPOTTER GROUPS SHOULD
PLAN FOR ACTIVATION THIS EVENING.

MYERS