Severe Thunderstorm Warning 137, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
338 PM CDT TUE JUL 11 2000

MAIN CONCERN TDA STILL TSTM TRENDS AND POSSIBLE HVY RAINS.  WATER
VAPOR IMAGERY SHOWS WEAK SHRT WV PUSHING INTO WRN IA WITH ASSOCD
TSTM COMPLEX THAT DVLPD AHD OF IT ALL BUT GONE.  SCND STGR SHRT WV
THAT WAS OVR NV YDA NOW PUSHING THRU DAKOTAS WITH DVLPG MCS AHD OF
IT.  STLT IMAGERY AND PROFILER DATA SHOW H85 FNT FM MCS SEWD JUST S
OF SLA AND THEN TO NR KPIA.  19Z SFC ANLYS PLACES FNT JUST SW OF
THIS AREA AS XPCD FM BTWN KONL-KYKN THRU KOMA METRO INTO CNTRL MO.
MSAS MSTR CNVGNC QUITE STG IN THESE LOCATIONS WITH TREMENOUS THETA-E
POOLING BUT SFC BASED CONVECTION HAS HAD A HARD TIME DVLPG WITH LAPS
CIN STILL AOA 40 J/KG AND OVR 100 IN MOST LOCATIONS.  SUSSIDENCE
BHND SHRT WV MAY BE SUPPRESSIVE DVLPMT TOO.  WEAK SFC WV NOTED ACRS
MO AND FEEL THAT CONVECTION ASSOCD WITH THESE FEATURE SHOULD MAINLY
DVLP FM MO EWD WHEN WHAT LOW LVL JET THERE IS STARTS UP.

OUR BEST CHCS SEEM TO BE WITH SD MCS AND FEEL THAT 12Z AVN AND 18Z
ETA HAVE BEST HANDLE ON EVOLUTION WITH HIGHER QPF AMTS.  THINK THAT
MCS WILL EVENTUALLY BCM MORE ELEVATED AS IT MOVES INTO FA LATER TNGT
ALG OR JUST S OF AFOREMENTIONED H85 BNDRY.  WDL PROFILER WIND SHEAR
CERTAINLY STG ENOUGH TO SUPPORT ORGANIZED TSTMS TOO WITH DAMAGING WINDS
CONSIDERING AMT OF INSTABILITY.  LOW LVL INFLOW WL BE FAIRLY WEAK
HWVR SO DO NOT XPC WDSPRD OR SGFNT HVY RAINS...MUCH LIKE REFLECTED
IN AVN/ETA QPF.  PWS STILL VRY HIGH...APCHG 2 INCHES TNGT...SO THERE
MAY BE LCLLY HVY RAINS...BUT NOT ENOUGH TO WARRANT FLASH FLOOD WATCH
ATTM.  SHRT WV SHOULD KEEP SYS PROGESSIVE ENOUGH.  WL KEEP MENTION
OF LCLLY HVY RAINS IN ZNS THOUGH.

PCPN CHCS SHOULD DMSH EARLY WED WITH MAINLY WRM AND HUMID WX TIL
START OF WEEKEND.  DID ADD LOW POPS NWRN SXNS THU INTO THU NGT HWVR
AS WRM ADVCTN RTRNS ARND MID LVL RDG.  FAN TEMPS AGN LOOK TOO COOL
SO WENT NR OR JUST BLO FWCS.

IN EXTENDED...MOST MDLS NOW COMING TOGETHER WITH FASTER SOLUTION FOR
GLF AK LOW...ALTHOUGH CANADIAN STILL MUCH LESS PROGRESSIVE.  THIS
FLATTENS RDG ENOUGH TO DROP WEAK BNDRY ACRS FA SUN...BUT DOES NOT
CHG AMS MUCH. RDG STILL HOLDING STG THRU CNTRL U.S. WITH H5 HGTS AOA
588 DM.  MRF HINTS AT SHRT WV CROSSING FA IN WEAK NWLY FLOW FRI WITH
SUBTLE H85 WRMFNT OVR SWRN SXNS BUT DO NOT FEEL CHCS HIGH ENOUGH TO
INTRODUCE INTO FCST ATTM.  MID LVL TEMPS MAY BE WRM YENOUGH TO
SUPPRESS MUCH DVLPMT BUT NEXT CHCS SEEM TO BE SUN.  AMS QUITE
UNSTABLE SO WL MENTION CHC TSTMS ALG AHD OF BNDRY.

COORD/W...DVN...ARX...EAX.

.DSM...NONE

SMALL

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-121100-

CENTRAL IOWA THUNDERSTORM OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE DES MOINES IA
429 PM CDT TUE JUL 11 2000

HAZARD--SCATTERED THUNDERSTORMS WITH DAMAGING WINDS OVER 60 MPH...
AND ISOLATED RAINFALL RATES OF 2 INCHES PER HOUR. LARGE HAIL
NEAR ONE INCH IN DIAMETER CAN NOT BE RULED OUT...BUT HAIL WILL NOT
BE THE MAIN THREAT.

AREA OF CONCERN--ALL OF CENTRAL IOWA.

TIMING--GENERALLY AFTER 8 PM CDT THROUGH THE OVERNIGHT HOURS.

METEOROLOGICAL COMMENTS--A COMPLEX OF SHOWERS AND THUNDERSTORMS WILL
MOVE SOUTHEAST THIS EVENING ACROSS EASTERN PORTIONS OF THE DAKOTAS
AND WESTERN MINNESOTA. AS THE SYSTEM PROGRESSES SOUTHEAST...IT WILL
BE FED BY MOIST AND VERY UNSTABLE AIR BEING TRANSPORTED NORTHWARD.
THIS COMPLEX WILL AFFECT CENTRAL IOWA LATER TONIGHT...ESPECIALLY WELL
AFTER SUNSET. THE OTHER FACTOR THAT COULD AID IN THUNDERSTORM
DEVELOPMENT THIS EVENING IS A SLOW MOVING WARM FRONT LOCATED IN
WESTERN IOWA. CONVERGENCE ALONG THIS FRONT AS WELL AS THE COMPLEX OF
STORMS SLIDING SOUTHEAST TONIGHT WILL COMBINE TOGETHER TO HELP
ENHANCE CONVECTION...ALL LEADING TO THE POSSIBILITY OF DAMAGING
WINDS...HEAVY RAINFALL...AND LARGE HAIL.

PRECAUTIONS--MONITOR LATER FORECAST UPDATES AND POSSIBLE WATCHES
THAT MAY BE ISSUED LATER TONIGHT REGARDING THIS DEVELOPING WEATHER
SITUATION.  SPOTTER ACTIVATION WILL LIKELY BE NEEDED LATER THIS
EVENING THROUGH THE OVERNIGHT HOURS.

KNOLLHOFF

ABUS31 KDSM 112206
RWSDSM

REGIONAL/IOWA WEATHER SUMMARY
NATIONAL WEATHER SERVICE DES MOINES IA
930 PM CDT TUE JUL 11 2000

IAZ035-039-060-120915-

...THE REGIONAL WEATHER SUMMARY...
A COMPLEX OF SHOWERS AND THUNDERSTORMS...FED BY MOIST AND UNSTABLE
AIR BEING TRANSPORTED NORTH...DEVELOPED OVER THE DAKOTAS THIS
EVENING.  THIS COMPLEX WILL MOVE SOUTHEAST...AND AFFECT CENTRAL IOWA
LATER TONIGHT. THE OTHER FACTOR THAT COULD AID IN THUNDERSTORM
DEVELOPMENT THIS EVENING IS A SLOW MOVING WARM FRONT LOCATED IN
WESTERN IOWA. CONVERGENCE ALONG THIS FRONT WILL ALSO AID IN THE
DEVELOPMENT OF THUNDERSTORMS.  SOME OF THESE THUNDERSTORMS COULD
BECOME SEVERE...HEAVY RAINFALL...AND LARGE HAIL...AND A SEVERE
THUNDERSTORM WATCH HAS BEEN ISSUED FOR PORTIONS OF NORTHWEST
IOWA...SOUTHWEST MINNESOTA...SOUTHEAST SOUTH DAKOTA...AND NORTHEAST
NEBRASKA. A FRONTAL SYSTEM ACROSS NORTHERN KANSAS...NORTHERN
MISSOURI AND INTO ILLINOIS WILL HELP CREATE AN UNSETTLED WEATHER
PATTERN INTO WEDNESDAY.  BY WEDNESDAY MORNING...THE EASTERN
TWO-THIRDS OF THE STATE SHOULD SEE SOME RAINFALL AS THE TWO SYSTEMS
BEGIN TO MOVE EAST. IMPROVING WEATHER WILL THEN OCCUR BY LATE
WEDNESDAY AS THE RAIN MOVES INTO ILLINOIS. HUMID CONDITIONS WILL
CONTINUE THE REST OF THE WEEK AS A WEAK HIGH PRESSURE AREA LINGERS
IN THE AREA INTO FRIDAY. HIGHS THE REMAINDER OF THE WEEK WILL BE IN
THE 80S TO LOWER 90S. LOWS WILL HOVER IN THE MIDDLE 60S TO LOWER 70S.

IAZ035-039-060-120915-

...THE IOWA WEATHER SUMMARY...
SKIES WERE MOSTLY CLOUDY AROUND THE STATE THIS EVENING...AND SOME
LIGHT FOG HAD DEVELOPED OVER PORTIONS OF SOUTH CENTRAL AND SOUTHEAST
IOWA.  HIGH TEMPERATURES THIS AFTERNOON WERE GENERALLY IN THE LOWER
80S...AND RANGED FROM 79 AT ESTHERVILLE TO 88 IN THE COUNCIL BLUFFS
AREA.  AT 9PM...TEMPERATURES HAD FALLEN INTO THE UPPER 70S IN MUCH
OF CENTRAL AND EASTERN IOWA...WITH A FEW LOWER 80S REPORTED IN THE
WEST.  WINDS WERE FROM THE SOUTHEAST AT 5 TO 10 MILES AN HOUR.

SCOTT