Severe Thunderstorm Warning 220, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
752 PM CDT SAT AUG 2 2008

.UPDATE...
VFR LOW CLOUDS ARE EXPECTED TO BREAK UP BEHIND EXITING SHORT WAVE
ACROSS NORTHEAST SOUTH DAKOTA AND WEST CENTRAL MINNESOTA THROUGH
MIDNIGHT. NEXT SHORT WAVE WILL BE AFFECTING THE REGION AFTER
MIDNIGHT INTO SUNDAY MORNING. THE NAM...GFS...AND RUC ALL POINT TO
THE CONVECTION IN MT COMING ACROSS THE NORTHERN PART OF THE REGION
LATER TONIGHT AND SUNDAY MORNING. THE NAM WAS THE FURTHEREST
SOUTH WHERE THE CAP WAS THE STRONGEST. WILL HAVE TO WAIT AND SEE.
TOOK OUT POPS FOR THIS EVENING AND MAY HAVE TO ADJUST POPS FOR
AFTER MIDNIGHT A LITTLE YET.

&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT
FORECAST CHALLENGES INCLUDE CONVECTION TONIGHT THROUGH SUNDAY
NIGHT AND HIGH TEMPERATURES SUNDAY UNDER CLOUD COVER.

CURRENTLY...A TROF AXIS SITS ACROSS THE FAR WESTERN FORECAST AREA
WITH PLENTY OF LOW LEVEL MOISTURE/INSTABILITY AROUND. THE CAP AT
700HPA IS FORECAST TO UNDERGO CAA THIS EVENING...WITH TEMPS
COOLING FROM AROUND +17C TO +13C...WHICH WOULD LIKELY BE ENOUGH
COOLING ALOFT TO ALLOW FOR ISOLATED TO WIDELY SCATTERED
SUPER CELLULAR THUNDERSTORMS TO DEVELOP WITHIN THE TROF AXIS.

THERE IS ALSO 700HPA WARM AIR ADVECTION AND 850HPA MOISTURE
ADVECTION ONGOING ACROSS THE EASTERN CWA INTO THIS EVENING. WHEN
THE LOW LEVEL JET CATCHES UP TO IT...THE NOSE OF THE LL MAY HELP
INDUCE ISOLATED TO WIDELY SCATTERED ELEVATED SUPER CELLULAR
THUNDERSTORMS ACROSS THE EASTERN THIRD OF FORECAST ZONES LATE THIS
EVENING BEFORE THEY MOVE OFF INTO MINNESOTA. HAVE INSERTED T+RE+
MENTION FOR THESE TO POSSIBLE SCENARIOS AT OPPOSITE ENDS OF THE
FORECAST AREA. WILL ALSO HAVE TO KEEP AN EYE ON THE CONVECTION
OVER NORTH DAKOTA THAT NOW APPEARS TO BE TRYING TO BUILD SOUTHWARD
ALONG THE LEADING EDGE OF 700HPA WAA.

LATE TONIGHT ANOTHER MID-LEVEL IMPULSE OF LOW PRESSURE WILL MOVE
OUT ONTO THE NORTHERN HIGH PLAINS. LOW LEVEL RESPONSE WILL BE A
SURFACE LOW DEEPENING OVER SE MONTANA/NW SOUTH DAKOTA WITH 850HPA
MOISTURE ADVECTION AND BACKING LOW LEVEL WINDS POINTING RIGHT INTO
EXPECTED THUNDERSTORM CLUSTER THAT WILL BE WORKING WED INTO THE
DAKOTAS. EXPECTING THIS STORM CLUSTER TO LATCH ONTO INSTABILITY
GRADIENT AT 850HPA OVER THIS CWA AND WHERE THE BEST LOW LEVEL JET
SUPPORT SETS UP...RUMBLING EASTWARD OVERNIGHT INTO SUNDAY MORNING.
T+RE+ MENTION FOR LATE TONIGHT INSERTED INTO CENTRAL SOUTH DAKOTA
ZONES WHERE 20 TO 40 POPS WERE INTRODUCED WITH THIS PACKAGE TO
COVER POTENTIAL CONVECTION LATE TONIGHT. ONCE THE MCS
DISSIPATES/PUSHES EAST INTO MN...WILL WATCH THE LOW LEVELS RESET
ONCE AGAIN WITH LIKELY A REPEAT PERFORMANCE SUNDAY NIGHT INTO
MONDAY MORNING. NO SEVERE MENTION AS OF YET...THOUGH...IN THE
GRIDS FOR SUNDAY NIGHT.

UNDERCUTTING NUMERICAL GUIDANCE HAS BEEN QUITE SUCCESSFUL TODAY.
JAMES RIVER VALLEY SOCKED IN WITH STRATUS CLOUDS ALONG THE LEADING
EDGE OF 850HPA MOIST TONGUE SLOWLY ADVECTING EAST...AND JUST NEVER
FULLY DISSIPATED TODAY. AS SUCH...DID NOT SEE TRUE MAX T POTENTIAL
OF MID/UPPER 80S ACHIEVED ACROSS SAID AREA. WITH CONVECTIVE DEBRIS
CLOUDS EXPECTED TO BE AROUND DURING THE DAY ON SUNDAY AND SLIGHTLY
COOLER 850HPA TEMPS TO MIX OUT ON AN ENE BOUNDARY LAYER
WIND...EXPECTING HIGHS ON SUNDAY TO BE AROUND 3 TO 5 DEGREES
COOLER THAN TODAY.

.LONG TERM...MONDAY THROUGH SATURDAY

MODELS CONTINUE IN GOOD AGREEMENT IN OVERALL PATTERN CHANGE FOR
THIS WEEK. WITH ZONAL FLOW ACROSS THE CWA TRANSITIONING TO
NORTHWEST FLOW AS FAIRLY STRONG TROF DIGS INTO THE EASTERN
CONUS...AND WESTERN CONUS RIDGE REESTABLISHES. THIS PATTERN WILL
ALLOW FOR COOLER AND DRIER AIR TO FILTER SOUTH OUT OF CANADA AND
INTO THE CWA...AND ALLOW FOR NEAR TO BELOW NORMAL TEMPERATURES
THROUGH THE LASTER HALF OF THE WORK WEEK. AS FOR PRECIPITATION
CHANCES...BEST OPPORTUNITY IS EARLY IN PERIOD WITH ZONAL FLOW
ALOFT AND SERIES OF SHORTWAVES SKIRTING THE DAKOTAS. HAVE ADDED
ADDITIONAL CHANCE FOR PRECIPITATION IN SOUTH CENTRAL SOUTH DAKOTA AS
BACKDOOR FRONT REINFORCES AN EARLIER CANADIAN AIRMASS UNDERGOING
MODIFICATION.

&&

.AVIATION...
VFR SKIES AND VISIBILITIES ARE EXPECTED TO CONTINUE THROUGH THE
NIGHT AND DAY SUNDAY. ANOTHER UPPER LEVEL SHORT WAVE WILL BE
AFFECTING THE REGION LATER TONIGHT AND SUNDAY FROM THE WEST. WE
MAY SEE SOME TSRAS DEVELOP OUT ACROSS THE WEST AND MOVE ACROSS THE
NORTHERN PART OF THE REGION. AT THIS POINT...DONT FORESEE ANY TSRAS
OR VICINITY THUNDER OCCURRING AT ANY ONE OF THE TAF STIES. WILL
WATCH AND AMEND IF NECESSARY.

&&

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

UPDATE...MOHR
SHORT TERM...DORN
LONG TERM...CONNELLY
AVIATION...MOHR

WEATHER.GOV/ABERDEEN

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
319 PM CDT SAT AUG 2 2008

MNZ039-046-SDZ008-020>023-032030-
TRAVERSE-BIG STONE-ROBERTS-CODINGTON-GRANT-HAMLIN-DEUEL-
319 PM CDT SAT AUG 2 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SLIGHT CHANCE FOR THUNDERSTORMS EXISTS ACROSS EXTREME EASTERN
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA TONIGHT. STORMS THAT
FORM LATE THIS EVENING WOULD BECOME SEVERE AND BE CAPABLE OF
PRODUCING LARGE HAIL.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

OFF AND ON CHANCES FOR THUNDERSTORMS EXIST FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT. A FEW STORMS COULD BE ON THE STRONG SIDE
WITH SMALL HAIL AND GUSTY WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE THIS EVENING.

SDZ005>007-010-011-032030-
MCPHERSON-BROWN-MARSHALL-EDMUNDS-DAY-
319 PM CDT SAT AUG 2 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS ARE POSSIBLE TONIGHT. HOWEVER...NO SEVERE STORMS ARE
EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

OFF AND ON CHANCES FOR THUNDERSTORMS EXIST FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT. A FEW STORMS COULD BE ON THE STRONG SIDE
WITH SMALL HAIL AND GUSTY WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THIS AFTERNOON OR TONIGHT.

SDZ003-004-009-032030-
CORSON-CAMPBELL-WALWORTH-
319 PM CDT SAT AUG 2 2008 /219 PM MDT SAT AUG 2 2008/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
SOUTH DAKOTA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SLIGHT CHANCE FOR THUNDERSTORMS EXISTS ACROSS NORTH CENTRAL
SOUTH DAKOTA LATE THIS EVENING. STORMS THAT FORM LATE THIS
EVENING WOULD BECOME SEVERE AND BE CAPABLE OF PRODUCING LARGE
HAIL AND DAMAGING WINDS.

A SECONDARY CLUSTER OF THUNDERSTORMS IS EXPECTED TO MAKE IT INTO
NORTH CENTRAL SOUTH DAKOTA LATE TONIGHT. HEAVY RAIN APPEARS TO BE
THE ONLY HAZARDOUS WEATHER CONCERN AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

OFF AND ON CHANCES FOR THUNDERSTORMS EXIST FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT. A FEW STORMS COULD BE ON THE STRONG SIDE
WITH SMALL HAIL AND GUSTY WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE THIS EVENING.

SDZ015>019-033>037-045-048-051-032030-
DEWEY-POTTER-FAULK-SPINK-CLARK-STANLEY-SULLY-HUGHES-HYDE-HAND-
JONES-LYMAN-BUFFALO-
319 PM CDT SAT AUG 2 2008 /219 PM MDT SAT AUG 2 2008/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SLIGHT CHANCE FOR THUNDERSTORMS EXISTS ACROSS CENTRAL AND SOUTH
CENTRAL SOUTH DAKOTA THIS EVENING. STORMS THAT FORM WOULD BECOME
SEVERE AND BE CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS.

A SECONDARY CLUSTER OF THUNDERSTORMS IS EXPECTED TO MAKE IT INTO
CENTRAL SOUTH DAKOTA LATE TONIGHT. THESE STORMS MAY BECOME SEVERE
WITH LARGE HAIL AND DAMAGING WINDS. HEAVY RAIN ALSO APPEARS TO BE
POSSIBLE WITH THESE STORMS LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

OFF AND ON CHANCES FOR THUNDERSTORMS EXIST FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT. A FEW STORMS COULD BE ON THE STRONG SIDE
WITH SMALL HAIL AND GUSTY WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING AND AGAIN LATE
TONIGHT.

DORN