Severe Thunderstorm Warning 499, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
330 AM CDT MON AUG 16 2004

.DISCUSSION...
UPDATED ZONES WILL BE OUT SHORTLY WITH THE ONLY MAJOR CHANGES TO THE
WX GRIDS FOR TODAY AND EARLY TONIGHT. SFC THETA-E AND CONVERGENCE
PROGS INDICATED THAT THUNDER MAY INITIATE A BIT FARTHER EAST THAN
GOING FORECAST. INSTABILITY AND SHEAR PARAMETERS STILL LOOK GOOD FOR
A FEW SVR STORMS IN THE EASTERN ZONES TODAY.  FOR HIGHS AM A BIT
CONCERNED THAT WESTERN ZONES WILL NOT HEAT TO THE MAX WITH SOME
LINGERING POST FRONTAL STRATUS AND MORE CLOUD COVER...SO BACKED OF
OFF HIGHS A TAD.

&&

.PREV DISCUSSION...
UPPER LEVEL WAVE CONTINUING TO MOVE SOUTHEAST...JUST ENTERING FAR
WESTERN MN AS OF 08Z AND SPARKING ADDITIONAL TSRA NORTH OF OUR MN
COUNTIES. EXPECT MOST OF THIS MORNING ACTIVITY TO BE EAST OF OUR CWA
BY DAYBREAK...BUT WILL CARRY A LOW POP EARLY TO COVER ANY LINGERING
TSRA IN THE FAR EASTERN COUNTIES.  FOCUS FOR THE AFTERNOON TURNS TO
COLD FRONT...WHICH AT 08Z WAS LOCATED NEAR A KABR-KPIR LINE...THEN
WEST BETWEEN KPHP AND KRAP.  SLOWER MODEL SOLUTION OF PREVIOUS DAYS
APPEARS TO HAVE BEEN MORE ON TARGET WITH TIMING...ALTHOUGH 00Z ETA
HAS COME AROUND TO SLOWER GFS SOLUTION...AND FRONT SHOULD BE NEAR A
KBKX-TYNDALL LINE BY MIDDAY...AND ROUGHLY SLAYTON-VERMILLION LINE BY
21Z.  MODELS SHOWING QUITE A BIT OF MOISTURE RETURN AHEAD OF THE
FRONT...WITH SURFACE DEWPOINTS FORECAST TO REACH THE MID TO UPPER
60S AHEAD OF THE FRONT BY LATE AFTERNOON.  THIS MAY BE A LITTLE
AGGRESSIVE...AS THIS MOISTURE IS STILL QUITE FAR SOUTH IN FAR SOUTH
CENTRAL KS AND OK...BUT SHOULD STILL SEE WIDESPREAD MID 60S OVER
NORTHWEST IOWA.  THIS INCREASE IN MOISTURE HELPS SBCAPE VALUES JUMP
TO NEAR 2500 J/KG...WITH 0-1KM MUCAPES CLOSER TO 3500 J/KG.  SO WITH
THIS AMOUNT OF INSTABILITY...AND DECENT SHEAR AVAILABLE...COULD SEE
A FEW SUPERCELL STORMS ALONG THE FRONT BEFORE IT EXITS NORTHWEST
IOWA THIS EVENING.

DRY TONIGHT AND MOST OF TUESDAY...BUT WILL KEEP A SLIGHT CHANCE OF
SHRA OR TSRA ALONG WITH MO RVR VALLEY TUESDAY AFTERNOON WITH BAND OF
MID LEVEL FRONTOGENESIS.  LEANED A LITTLE CLOSER TO ETA PRECIP IDEA
AS GFS SEEMS TO BE PAINTING QPF TOO FAR NORTH GIVEN LOCATION OF
STRONGEST MID LEVEL FRONTOGENESIS.  FAR SOUTH WILL AT LEAST SEE MORE
CLOUD COVER WITH THIS LIFT...SO HAVE KEPT HIGHS A FEW DEGREES BELOW
FULL MIXING POTENTIAL ALONG THE RIVER.  GFS AND ETA CLOSER IN TIMING
NEXT FRONT DROPPING SOUTH WEDNESDAY/WEDNESDAY NIGHT...BUT NOT REALLY
A LOT OF MOISTURE TO WORK WITH...AND ANY UPPER LEVEL SUPPORT IS WELL
NORTH OF THE AREA SO HAVE ADJUSTED POPS TO JUST A SLIGHT CHANCE IN
THE NORTHEAST AND EAST...NEAR STRONGEST FRONTOGENESIS.  DESPITE
SIMILARITY IN FRONTAL TIMING...MODELS STILL QUITE DIFFERENT WITH
RESPECT TO LOW LEVEL TEMPS.  SHOULD BE GOOD MIXING...BUT WITH 00Z
THURSDAY 850MB TEMPS 4-5C DIFFERENT BETWEEN ETA AND GFS...MIXING
GIVES ABOUT 10F DIFFERENCE IN SURFACE TEMPS.  GOING FORECAST IS A
GOOD COMPROMISE BETWEEN THE TWO...AND WILL STICK WITH THAT FOR NOW.

NO CHANGES TO LONGER RANGE FORECAST AT THIS TIME.

&&

.FSD...WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

 JRM/HACKER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1149 AM CDT SUN AUG 15 2004

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-161200-
AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA-
CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE-
DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON-
IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN-
LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN-
OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN-
SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON-
1149 AM CDT SUN AUG 15 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA...
SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE BEFORE 2 PM
ACROSS MUCH OF THE AREA. THESE STORMS ARE NOT EXPECTED TO BECOME
SEVERE...ALTHOUGH PEA SIZE HAIL COULD ACCOMPANY THE STRONGEST
STORMS.

SCATTERED THUNDERSTORMS WILL DEVELOP LATE THIS AFTERNOON NORTH OF
A GREGORY SOUTH DAKOTA TO MARSHALL MINNESOTA LINE...THEN SPREAD
SOUTHEAST ACROSS THE REMAINDER OF THE AREA DURING THE EVENING AND
OVERNIGHT. SEVERE THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON
AND INTO THE EVENING HOURS. LARGE HAIL WILL BE THE MAIN THREAT
WITH THESE STORMS...BUT 60 MPH WIND GUSTS ARE ALSO POSSIBLE. AS
THUNDERSTORMS CONTINUE TO PUSH SOUTH ACROSS THE AREA OVERNIGHT
THEY WILL GRADUALLY WEAKEN AND THE SEVERE WEATHER THREAT WILL
DIMINISH.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

SOUTHEAST OF A LINE FROM VERMILLION SOUTH DAKOTA...TO ROCK RAPIDS
IOWA TO WINDOM MINNESOTA...SCATTERED THUNDERSTORMS WILL LINGER
INTO MONDAY MORNING.  THESE THUNDERSTORMS ARE NOT EXPECTED TO BE
SEVERE.  THIS SAME AREA WILL SEE A SLIGHT CHANCE OF REDEVELOPMENT
DURING THE AFTERNOON.  IF STORMS CAN DEVELOP DURING THE
AFTERNOON... AN ISOLATED STORM COULD PRODUCE PENNY SIZE HAIL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE POSSIBLE AFTER 3 PM NORTH OF A GREGORY
TO MARSHALL LINE. SPOTTER ACTIVATION WILL BE POSSIBLE ACROSS THE
REST OF SOUTHEAST SOUTH DAKOTA AND SOUTHWEST MINNESOTA AFTER 6
PM.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.CRH.NOAA.GOV/FSD. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.