Severe Thunderstorm Warning 229, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
233 PM CDT MON JUL 3 2006

.SYNOPSIS...
MID/UPPER LEVEL FLOW BCMG MORE AMPLIFIED THROUGH THE WEEK AS A MID-
LEVEL TROF JUST W OF HUDSON BAY SLIDES EWD INTO THE NORTHEAST/SRN
ONTARIO. FURTHER WEST...AN UPPER LEVEL RIDGE WL GRADUALLY
BUILD/TRANSLATE EWD ACROSS THE GREAT BASIN/INTERMOUNTAIN WEST AND
INTO THE UPPER MISSISSIPPI VALLEY WITH H5 HGTS INC TO AOA 585 DM
BY FRI. AS A RESULT...MUCH OF THE AREA WILL BE IN THE FAVORABLE
SUBSIDENCE REGION DOWNSTREAM OF THE WRN RIDGE AXIS RESULTING IN
DRY CONDS AND A SLOW TEMP MODERATION /WARMING/ THROUGH THE
WEEKEND. THE UPPER LEVEL PATTERN APPEARS TO BREAK DOWN BY THIS
TIME A S/W TROF AND ASSOCD JET MAX MOVE EWD ACROSS WRN CANADA/PAC
NW.

AT THE SFC...DUEL FRNTL BNDRY/S FROM WL SLIDE SWD THROUGH IA AND
INTO THE LWR MO VALLEY TONIGHT INTO EARLY TUESDAY WITH SCT SHRA/TSRA
DEC IN COVERAGE FM N TO S. MUCH OF THE REMAINDER OF THE PERIOD WILL
BE CHARACTERIZED BY AN ANOMALOUS SFC ANTICYCLONE DROPPING SWD FM
SCENT CANADA AND INTO THE UPPER/MIDDLE MISSISSIPPI VALLEY. THE NEXT
WEATHER FEATURE OF NOTE WILL BE A FRNTL SYS PUSHING ESE FM THE NRN
PLAINS/UPR MIDWEST SUN/MON.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
CONVECTION BEGINNING TO DVLP THIS AFT WITH RAPIDLY INC
INSTABILITY /ML CAPE VALUES 1000-2000 J/KG AND SFC LI/S
APPROACHING -10. 18Z ANALYSIS SHOWS COLD FRONT XTNDG FM THE WRN
GRT LAKES SSWD BACK THROUGH SRN MN AND INTO NRN IA. IN
ADDITION...SECOND...MORE DIFFUSE BNDRY DRAPED ACROSS CENT IA ATTM.
FOCUS FOR SEVERE STORMS APPEARS TO BE ASSOCIATED WITH BOTH BNDRY/S
WITH A VERY UNSTABLE...UNCAPPED AIRMASS IN PLACE WITH PLENTY OF BL
MOISTURE /65-75 TD/. WL LIKELY SEE AN INC IN STORMS AS THE
FRONT/S/ TRANSLATE ESE ACROSS THE AREA. THEREFORE...GIVEN STRONG
SFC BASED BUOYANCY AND FAVORABLE VERTICAL /SPEED/ SHEAR PROFILES
ALONG WITH STEEP LOW LEVEL LAPSE RATES...HAVE INTRODUCED SEVERE
WORDING INTO THE TEXT FORECAST AND THE GRIDS FOR LARGE HAIL/DAMAGING
WINDS. PWAT VALUES OVER 1.5 WILL ALSO CONTRIBUTE TO LOCALLY HEAVY
RAINFALL. XPECT SCT STORMS TO CONTINUE TO DEVELOP INTO TONIGHT
ALONG/AHEAD OF THE BNDRY/S.

FRONT/S WILL SETTLE INTO THE LWR MO VALLEY BY EARLY TUESDAY BEHIND
ANOMALOUS /1-3STD ABV NORMAL/ SFC HIGH PRES...WHICH WILL PROVIDE DRY
CONDITIONS THROUGH THE REMAINDER OF THE WORK WEEK. SREF 850MB
TEMPS /1-2STD BLO NORMAL/ IN CONJUNCTION WITH THE STRONG SFC HIGH
WL RESULT IN SLIGHTLY COOLER THAN NORMAL TEMPS THROUGH THUR /WARM
DAYS AND COOL NIGHTS/.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
MEDIUM RANGE MODELS IN FAIRLY GOOD AGREEMENT WITH THE H5 RIDGE AXIS
CROSSING THE UPPER MISSISSIPPI VALLEY BY FRIDAY AND MOVING EWD INTO
THE WRN GRT LAKES. AFOREMENTIONED SFC HIGH WILL SLIDE SEWD INTO THE
OHIO VALLEY WITH RETURN FLOW DEVELOPING ACROSS THE REGION.
MEANWHILE...DEAMPLIFICATION OF THE UPPER LEVEL FLOW WILL LIKELY
OCCUR IN RESPONSE TO A MID-LEVEL S/W TROF MOVING INTO WRN CANADA AND
PROGRESSING EWD. SFC REFLECTION /CLD FRNTL POSITION/ CONSENSUS AMONG
THE ECMWF...GFS AND THE 03/00Z MREF APPEARS TO BRING THE FNTL BNDRY
INTO THE REGION SOMETIME SUN INTO MON. HAVE ADDED IN SCHC-CHC POPS
INTO D7 AND BEYOND TO ACCOUNT FOR THIS FEATURE IN COORDINATION WITH
SURROUNDING OFFICES. MUCH OF THE XTNDD UNCHANGED WITH ONLY A FEW
MINOR TWEAKS HERE AND THERE GIVEN THE PENDING SVR WX.

&&

.AVIATION...
VFR CONDS WITH MVFR VIS/CIGS IN TSRA LATE THIS AFT/EARLY EVE AS A
COLD FRONT PUSHES ESE ACROSS THE STATE. WRLY SFC WNDS SHIFTING TO
NNW UPON FROPA.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

.SYNOPSIS...STEINBUGL
.SHORT TERM...MS/STEINBUGL
.LONG TERM...STEINBUGL
.AVIATION...MS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
210 PM CDT MON JUL 3 2006

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-041100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-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-
210 PM CDT MON JUL 3 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS WILL BE SCATTERED OVER MUCH OF CENTRAL IOWA THIS
AFTERNOON THROUGH MUCH OF TONIGHT.  SCATTERED SEVERE THUNDERSTORMS
WILL BE LIKELY NORTHWEST OF A WATERLOO...DES MOINES...TO BEDFORD
LINE THROUGH 5 PM...AND OVER MUCH OF CENTRAL IOWA INTO THE EVENING.
SOME STORMS COULD PRODUCE HAIL AROUND ONE INCH IN DIAMETER...AND
STRAIGHT LINE WIND GUSTS OF 60 TO 70 MPH. ISOLATED HEAVY RAINFALL
AMOUNTS OF 1 TO 2 INCHES ARE POSSIBLE SOUTH OF INTERSTATE 80 THROUGH
SUNRISE TUESDAY.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

ISOLATED NON-SEVERE THUNDERSTORMS ARE POSSIBLE TUESDAY IN FAR SOUTHERN
IOWA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THROUGH 7 PM NORTHWEST OF A
WATERLOO...DES MOINES...BEDFORD LINE AND FROM 4 PM THROUGH 11 PM
SOUTHEAST OF THAT LINE.

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