Severe Thunderstorm Warning 290, NWS Des Moines, IA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
315 PM CDT SUN AUG 13 2006

.SHORT TERM /REST OF TODAY/...
UPDATED ZONES AND GRIDS FOR SEVERE THUNDERSTORM WATCH /718/.

&&

.PREV DISCUSSION... (ISSUED 156 PM CDT SUN AUG 13 2006)

SHORT TERM /TONIGHT THROUGH TUESDAY/...
REGIONAL RADAR CURRENTLY DEPICTING AREA OF SHRA/TSRA ALONG A
KRST-KFOD-KLNK LINE...WHICH IS WELL-ALIGNED WITH SW-NE MOISTURE
PLUME EVIDENT IN THE WATER VAPOR IMAGERY. WV LOOP ALSO SHOWING
ADVANCING S/W TROUGH MOVING EWD ACROSS THE DAKOTAS SPREADING
SUFFICIENT LARGE SCALE ASCENT ACROSS MUCH OF THE UPPER MISSISSIPPI
VLY. MID AND HIGH LVL CLOUD DEBRIS HAS LIMITED OVERALL INSTABILITY
TO SOME DEGREE EARLY THIS AFT...HOWEVER APPEARS BEST SVR THREAT
WILL BE ALONG THE LEADING EDGE OF THE CONVECTION ACROSS THE
CENTRAL/SCENT CWA WHERE TEMPERATURES HAVE REACHED THE LOW-MID 80S
WITH DEWPOINTS REACHING THE LOW 70S DESPITE BKN-OVC SKIES. LATEST
RUC SEEMS TO HAVE A FAIRLY DECENT HANDLE ON THE EVOLUTION OF THE
CONVECTION AS IT DEVELOPS 1500-2000 J/KG MLCAPES ACROSS THE
AFOREMENTIONED AREA FM THIS AFT INTO TNT. LACK OF DRY AIR
INTRUSION/ENTRAINMENT INTO THE MID LVLS WILL LIMIT THE OVERALL
THREAT OF DAMAGING WINDS ALTHOUGH STILL POSSIBLE WITH 1000+ J/KG
DCAPE. HAIL NOT LIKELY GIVEN RATHER HIGH FZ LVLS. LOCALLY HEAVY
RAINFALL SEEMS LIKELY GIVEN SREF PWATS /2-3STD/ ABOVE NORMAL AND
STRONG LLVL MOISTURE CONVERGENCE/TRANSPORT ALONG THE COLD FRONT.
IN ADDITION...FAVORABLE RT ENTRANCE DYNAMICS OF AN /120+KT/ ULJ
WILL ALSO BE IN PLACE FM THIS EVE INTO TONIGHT WITH MAIN FOCUS
ACROSS THE FAR SOUTH. THUS...SLGHT RISK FOR EXCESSIVE RAINFALL
POTENTIAL WITH ISOLD 1.50-2.00 RAINFALL TOTALS NOT OUT OF THE
QUESTION ALTHOUGH OVERALL STORM MOVEMENT SHOULD BE PROGRESSIVE.
LLVL CAA IN THE WAKE OF THE FROPA WILL ESSENTIALLY KEEP TRAINING
OF CELLS TO A SHORT DURATION.

HAVE USED A MET/MAV BLEND FOR LOWS TNT AND GRADUALLY TAPER PCPN OUT
OF THE CWA BY 12Z MON. THE COLD FRONT WILL REACH THE GREAT LAKES/MID
MISSISSIPPI VLY BY MID-DAY MONDAY WITH SFC HI PRES DROPPING ESEWD
FM THE NORTHERN PLAINS. THE COOL HIGH PRES SYS WILL PROVIDE DRY
CONDITIONS THRU TUESDAY WITH SEASONABLY WARM DAYS AND RELATIVELY
COOL NIGHTS. HAVE MIXED DOWN NAM 850 T FOR HIGHS TOMORROW WHICH
WILL YIELD UPR 70S-LOW 80S FOR HIGHS. SREF PWATS /1-2STD/ BELOW
NORMAL COMBINED WITH CLEAR SKIES AND LIGHT WINDS WILL ALLOW FOR
IDEAL RADIATIONAL COOLING ON MONDAY NIGHT WITH NISH VLY LOCATIONS
AS WELL AS THE /KALO/KMIW/KAMW/ CORRIDOR TO SEE LOW/MID 50S WITH
/KMCW/KEST/ DIPPING TO AROUND 50. HAVE GONE AOB MET/MAV IN THIS
TIME FRAME. OVERALL...PLEASANT AND COMFORTABLE CONDITIONS WITH LOW
HUMIDITY WILL BE COMMON INTO MID WEEK.

LONG TERM /WEDNESDAY THROUGH SUNDAY/...
NO SIG CHANGES IN THE XTNDD GIVEN PENDING SVR WX THREAT THIS AFT.
AFOREMENTIONED SFC HIGH WILL SLIDE EWD INTO THE LWR GREAT LAKES BY
WEDNESDAY WITH WAA/RETURN FLOW REGIME COMMENCING ACROSS THE CENTRAL
PLAINS/MID MO VLY. FIRST SHOT AT PCPN APPEARS TO BE WED EVE/NGHT
ACROSS THE FAR W AS SURGE OF 850-700MB THETA-E ADV MOVES NNEWD
ACROSS THE MID MO VLY. LEE SFC TROUGH DEVELOPS ACROSS THE HIGH
PLAINS BY THURS AS NRN STREAM UPR RIDGING TRANSLATES EWD INTO THE
UPR GRT LAKES. MED RANGE MODEL SOLNS BEGIN TO DIVERGE BY THIS
TIME AS THE ECMWF MORE AGGRESSIVE WITH ADVANCING FRONTAL SYSTEM
THAN THE GFS. 13/00Z MREF AND NCEP ENSEMBLE MEAN SEEM TO BE A GOOD
COMPROMISE IN THE OUTER PDS GIVEN OVERALL UNCERTAINTY WITH RESPECT
TO THE UPPER LEVEL PATTERN WHICH FEATURES SEVERAL NRN STREAM
DISTURBANCES TRANSLATING EWD ON THE SRN EDGE OF THE WESTERLIES.

AVIATION...
OCNL MVFR VIS/CIGS IS TSRA THIS AFT/EVE AS COLD FRONT TRANSLATES
ESEWD ACROSS THE STATE. IMPROVEMENT IS EXPECTED BY LATE IN THE PD AS
HI PRES MOVES SEWD FROM THE NORTHERN PLAINS AND INTO THE UPPER
MISSISSIPPI VALLEY. SSE SFC WNDS BCMG NWERLY IN THE WAKE OF FROPA.

HYDROLOGY...
LOCALLY HEAVY RAINFALL /RATES/ MAY CAUSES SOME MINOR FLOODING
/URBAN-POOR DRAINAGE AREAS/ PROBLEMS FM THIS AFT INTO TONIGHT AS
CONVECTION CONTINUES TO MOVE EWD ALONG ADVANCING COLD FRONT.
HOWEVER...STORM MOTION WILL BE RATHER PROGRESSIVE WHICH SHOULD
LIMIT ANY WIDESPREAD +RA. IN ADDITION...SLIGHT RISK OF EXCEEDING
FFG ACROSS PTNS OF FAR SOUTHERN IA CWA PER HPC.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...SEVERE THUNDERSTORM WATCH 718
ALONG AND EAST OF A GREENFIELD...STORY CITY TO PARKERSBURG LINE.

&&

.SHORT TERM...STEINBUGL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
115 PM CDT SUN AUG 13 2006

IAZ004>007-015>017-023>025-033>035-044-045-141100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-SAC-CALHOUN-WEBSTER-CRAWFORD-CARROLL-
115 PM CDT SUN AUG 13 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA
GENERALLY NORTHWEST OF A LINE FROM CARROLL TO FORT DODGE TO MASON CITY.

.DAY ONE...THIS AFTERNOON AND TONIGHT
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE
REDEVELOPING INTO EARLY EVENING...BEFORE MOVING OFF TO THE EAST.
EXPECT BRIEF DOWNPOURS AND OCCASIONAL LIGHTNING...BUT MOST OF THE THREAT
FOR SEVERE WEATHER OR HEAVY RAIN SHOULD BE OFF TO THE SOUTHEAST OF
CARROLL...FORT DODGE AND MASON CITY.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THERE IS A CHANCE OF THUNDERSTORMS FROM WEDNESDAY NIGHT INTO NEXT
WEEKEND. IT IS TOO EARLY TO DETERMINE SEVERE POTENTIAL.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE NOT LIKELY TO BE NEEDED.

IAZ026>028-036>039-046>050-057>062-070>075-081>086-092>097-141100-
FRANKLIN-BUTLER-BREMER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-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-
115 PM CDT SUN AUG 13 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA
GENERALLY SOUTHEAST OF A LINE FROM CARROLL TO FORT DODGE TO MASON
CITY.

.DAY ONE...THIS AFTERNOON AND TONIGHT

ONGOING THUNDERSTORMS SHOULD BEGIN TO RE-INTENSIFY LATER THIS
AFTERNOON FROM SOUTHWEST IOWA INTO CENTRAL IOWA AND THE IOWA FALLS
AND WATERLOO AREAS. THE MAIN THREAT FROM THESE STORMS SHOULD BE
HEAVY RAINFALL...BUT THERE IS ALSO A SLIGHT RISK FOR DAMAGING
THUNDERSTORM WINDS WITH A FEW OF THE STRONGER STORMS. ISOLATED
RAINFALL AMOUNTS IN EXCESS OF 2 INCHES ARE POSSIBLE...WHICH COULD
CAUSE URBAN FLOODING. THE THUNDERSTORMS SHOULD GRADUALLY MOVE OFF
TO THE SOUTHEAST...EXITING SOUTHERN AND SOUTHEAST IOWA BETWEEN 9
PM AND MIDNIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THERE IS A CHANCE OF THUNDERSTORMS FROM WEDNESDAY NIGHT INTO NEXT
WEEKEND. IT IS TOO EARLY TO DETERMINE SEVERE POTENTIAL.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ACTIVATION IS LIKELY OVER PORTIONS OF CENTRAL AND
SOUTHERN IOWA BETWEEN 4 PM AND 9 PM.

JUNGBLUTH