Severe Thunderstorm Warning 127, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
222 PM CDT FRI AUG 14 2009

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT FORECAST CONCERNS INCLUDE
THE POSSIBILITY OF SEVERE WEATHER TONIGHT AND SATURDAY...AS WELL AS
LOCALLY HEAVY RAINFALL THROUGH SATURDAY NIGHT.

AN AREA OF SFC LOW PRESSURE WILL STRETCH FROM ND TO EASTERN CO
TONIGHT. A SHORTWAVE WILL MOVE FROM SW TO NORTH CENTRAL SD
TONIGHT. AFTER 0Z TONIGHT...THE 4KM WRF FROM NSSL SHOWS A LINE OF
STORMS DEVELOPING ALONG THE MISSOURI RIVER IN ASSOCIATION WITH
THIS SHORTWAVE. MLCAPE VALUES ARE BETWEEN 2000 AND 3200 J/KG...WITH
0-6KM SHEAR OF 40 KNOTS. THE BEST CAPE AND SHEAR VALUES HOWEVER
ARE NOT COLLOCATED. IF THUNDERSTORMS DO DEVELOP THIS
EVENING...SOME MAY BECOME STRONG TO MARGINALLY SEVERE. CANNOT RULE
OUT LARGE HAIL OR GUSTY WINDS WITH THESE ELEVATED STORMS
ESPECIALLY FROM THE MISSOURI RIVER WEST. DUE TO WARM AIR ALOFT ACROSS
THE EASTERN CWA...EXPECT THUNDERSTORMS WILL PROPAGATE
EASTWARD...AND MAY BECOME MORE OF A HEAVY RAIN EVENT AS STORMS
BEGIN TO TRAIN OVER NORTHCENTRAL SD. PWATS ARE UP TO 2 INCHES BOTH
TONIGHT AND SATURDAY WITH THE WRF SHOWING LOCALLIZED AREAS OF OVER
4 INCHES OF ACCUMULATION TONIGHT. DO NOT EXPECT THIS TO
MATERIALIZE BUT IF TRAINING SETS UP OVER THE NORTHWESTERN PART OF
THE CWA MAY SEE VERY LOCAL AMOUNTS OF UP TO 2 INCHES.

THERE MAY BE A BREAK IN THE ACTION ON SATURDAY...MAINLY BETWEEN
15-21Z...BEFORE THE NEXT SHORT WAVE MOVES THROUGH SATURDAY NIGHT.
AFTER 21Z...MODELS DEPICT A COLD FRONT APPROACHING THE CWA FROM
THE WEST. MLCAPE VALUES ARE BELOW 2000 J/KG HOWEVER 0-6KM BULK
SHEAR IS SHOWN TO BE AOA 35 KNOTS. THIS ACTUALLY OCCURS BEHINDS
THE COLD FRONT AS CAA MOVES IN ALOFT. GIVEN THE SLOW MOVEMENT OF THE
COLD FRONT ACROSS THE CWA...AND ADDED UPPER LEVEL LIFT...BELIEVE
LOCALLY HEAVY RAINFALL IN THE NORTHEAST PART OF THE CWA MAY BE
POSSIBLE SATURDAY AFTERNOON AND SATURDAY NIGHT. THUNDERSTORMS ARE
ALSO PROBABLE BUT WHETHER OR NOT THEY WILL REACH SEVERE LEVELS
WILL DEPEND ON HOW MUCH CONVECTION TAKES PLACE TONIGHT. WILL LEAVE OUT
THE MENTION OF LOCALLY HEAVY RAINFALL FOR NOW.

ON SUNDAY THE TROUGH WILL CONTINUE TO MOVE THROUGH THE AREA WITH
SOME LINGERING SHOWERS IN ITS WAKE. AFTER THAT HIGH PRESSURE WILL
BEGIN TO BUILD IN.

TEMPERATURE WISE...EXPECT NEAR TO BELOW NORMAL ON SATURDAY.
EXPECT HIGHS ON SUNDAY WILL BE AS MUCH AS 10 DEGREES BELOW
NORMAL...WITH HIGHS IN THE MID 70S.

.LONG TERM...12Z MONDAY THROUGH FRIDAY
MAIN FCST CHALLENGE FACING THE LONG TERM DEALS WITH PCPN CHANCES
THROUGH THE PERIOD.

MODELS START OFF IN FAIRLY GOOD AGREEMENT...WITH CLOSED 500HPA
SYSTEM IN PLACE ACROSS NWRN MN/SRN CANADA. THERE ARE SOME MINOR
FEATURES THAT ROTATE THROUGH ON THE BACKSIDE OF THIS
SYSTEM...PROVIDING MINOR CHANCES OF PCPN. STILL BROADBRUSHED THESE
CHANCES AS TIMING/LOCATION/EXTENT OF THESE MINOR RIPPLES MOVING
THROUGH IS TOUGH TO NAIL DOWN THIS FAR OUT. BY 12Z WEDNESDAY THE
MODELS BEGIN TO DIVERGE...WITH THE GFS TAKING THE NEXT STRONGER
500HPA/700HPA WAVE FURTHER TO THE WEST...DROPPING THIS FEATURE
INTO MT. THE EC REMAINS PROGRESSIVE WITH THIS FEATURE...KEEPING IT
EMBEDDED IN THE DOMINATE NW FLOW WITH ONLY GENERAL TROFINESS NOTED
IN THE 500 HPA FLOW. BY 12Z THURSDAY THE GFS CLOSES OFF THIS
SYSTEM...WHILE THE EC KEEPS WITH THE OPEN WAVE LOOK. THE GEFS
AGREES WITH THE MORE PROGRESSIVE SOLN...WITH THE CANADIAN ALSO
HAVING A MORE EC FEEL TO IT THAN THE GFS. SO HAVE OPTED TO LEAN
MORE TOWARD THE EC SOLN. THUS...MORE SUBSIDENCE/DOWNGLIDE ON THE
THETA SURFACES ARE PRESENT...RESULTING IN REDUCED CHANCES FOR
PCPN. BEGAN SHADING PCPN CHANCES FURTHER TO THE EAST TOWARD THE
END OF THE PERIOD AS DRIER AIR WORKS IN FROM THE NW.

TEMP WISE...THEY STILL LOOK SUBSEASONAL THROUGH THE PERIOD WITH
COOL NW FLOW ESTABLISHED.

&&

.AVIATION...
A SURFACE LOW/FRONT LOCATED ACROSS CENTRAL SD WILL BE THE FOCUS
FOR MORE THUNDERSTORM CHANCES LATER THIS AFTERNOON/EVENING ACROSS
THE AREA. SOME ISOLD MVFR CIGS/VSBYS ARE POSSIBLE WITH THE HEAVY
RAIN...BUT CONFIDENCE IS LOW TO FORECAST EXACTLY WHEN/WHERE THESE
CONDITIONS WILL OCCUR. LOCALLY HEAVY RAIN IS ALSO POSSIBLE WHICH
MAY AFFECT RUNWAY CONDITIONS. BY 10Z TUESDAY MOST OF THE PCPN
SHOULD HAVE MOVED EAST OF THE JAMES RIVER VALLEY...AFFECTING THE
KABR/KATY TERMINALS.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

SHORT TERM...WISE
LONG TERM...HINTZ
AVIATION...HINTZ

WEATHER.GOV/ABERDEEN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
426 AM CDT FRI AUG 14 2009

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-151000-
TRAVERSE-BIG STONE-CORSON-CAMPBELL-MCPHERSON-BROWN-MARSHALL-
ROBERTS-WALWORTH-EDMUNDS-DAY-DEWEY-POTTER-FAULK-SPINK-CLARK-
CODINGTON-GRANT-HAMLIN-DEUEL-STANLEY-SULLY-HUGHES-HYDE-HAND-JONES-
LYMAN-BUFFALO-
426 AM CDT FRI AUG 14 2009 /326 AM MDT FRI AUG 14 2009/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL
MINNESOTA...CENTRAL SOUTH DAKOTA...NORTH CENTRAL SOUTH DAKOTA AND
NORTHEAST SOUTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS THIS
AFTERNOON FOR LOCATIONS ALONG AND WEST OF THE JAMES RIVER. WHILE
WIDESPREAD SEVERE WEATHER IS NOT ANTICIPATED...SOME THUNDERSTORMS
MAY BECOME STRONG WITH THE MAIN THREAT BEING SMALL HAIL AND GUSTY
WINDS.

ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE DURING
THE OVERNIGHT HOURS ACROSS THE ENTIRE AREA. DEPENDING ON THE TIME
OF THUNDERSTORM DEVELOPMENT...SOME OF THESE MAY BECOME STRONG TO
SEVERE. THE MAIN THREAT WITH INITIAL THUNDERSTORMS WILL BE LARGE
HAIL AND GUSTY WINDS. THE BEST LOCATION FOR THUNDERSTORM
DEVELOPMENT APPEARS TO BE WEST OF THE MISSOURI RIVER. THUNDERSTORMS
MAY EVOLVE INTO THE LINE OF STORMS AS THEY MOVE EAST ACROSS THE
STATE. LOCALLY HEAVY RAINFALL AND STRONG WINDS WILL BE THE MAIN
THREAT ONCE THE STORMS EVOLVE INTO THE LINE OF STORMS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE SLOW MOVING WEATHER SYSTEM WILL CONTINUE TO TRACK ACROSS THE
NORTHERN PLAINS THROUGH THE WEEKEND. WHILE WIDESPREAD SEVERE WEATHER
IS NOT ANTICIPATED...LOCALLY HEAVY RAINFALL MAY BE POSSIBLE...ESPECIALLY
SATURDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR TONIGHT.

SD

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