Severe Thunderstorm Warning 114, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
315 PM CDT WED JUL 18 2001

INTERESTING DAY. VERY UNSTABLE AIR IN PLACE OVER THE AREA.  MORNING
SOUNDING SHOWED 5500 J/KG CAPE AND LI OF -12.5C WITH A PRECIPITABLE
WATER OF 1.42.  NOT BAD FOR A MORNING SOUNDING.  LAST EVENINGS
SOUNDING SHOWED CAPES OF 7800 AND -16.  VERY INTERESTING VALUES FOR
THIS PART OF THE COUNTRY.  AFTERNOON HEATING CONTINUES TO DESTABILZE
AIR UNDER FAIRLY STRONG CAP.  LATEST GOES DERIVED PRODUCTS FROM 16Z
CONFIRM VERY HIGH CAPE VALUES AND DECREASING CINH VALUES UNDER 100
J/KG JUST WEST OF ABERDEEN.  STILL HAVE VERY WARM MID LAYER IN PLACE
WITH H7 TEMPERATURE OF +11 ON 12Z SOUNDING AND +12 ON GOES DERIVED
SOUNDING.  THIS WARM MID LAYER WOULD NORMALLY BE ENOUGH TO INHIBIT
CONVECTION IN THIS AREA.  HOWEVER AGREE WITH SPC ON EXISTENCE OF SUB
SYNOPTIC BOUNDARIES CLOSE TO THIS AREA TO FOCUS CONVERGENCE AS WELL
AS SYNOPTIC BOUNDARIES TO THE NORTH AND WEST.  H5 WAVE IS MOVING
OVER EAST CENTRAL PART OF THE STATE THAT WILL ALSO AID DEVELOPMENT.
WITH CAP ERODING WILL MENTION CHANCE OF THUNDERSTORMS...SOME
POSSIBLY SEVERE...IN THE EASTERN HALF OF THE AREA.  EXPECT THE MOST
LIKELY AREA TO BE THE NORTH AND EAST PART OF AREA.  NEXT SIGNIFICANT
CHANCE WILL OCCUR THURSDAY NIGHT AND FRIDAY AS STRENGTHENING H5 WAVE
CLOSES OFF OVER NORTHEAST SOUTH DAKOTA.

.EXTENDED DISCUSSION...
EXTENDED MODELS CONTINUE TO SHOW NO RELIEF IN THE HEAT OR HUMIDITY
THROUGH MUCH OF THE EXTENDED PERIOD AS 500MB RIDGE MOVES LITTLE
THROUGH PERIOD. THEREFORE...BIGGEST ISSUE WILL BE THE CHANCES FOR
CONVECTION. THINK MOST OF THE CONVECTION SATURDAY AND SUNDAY WILL
STAY NORTH OF THE AREA AS AVN MODEL WOULD SUGGEST THAT WE WOULD BE
CAPPED. WEAK FRONTAL BOUNDARY PUSHES THROUGH THE REGION ON MONDAY
WHICH WILL GIVE MUCH OF THE CWA A CHANCE FOR STORMS...THEN HIGH
PRESSURE MOVES IN ON TUESDAY. THE HIGH THEN PUSHES OFF TO THE EAST
ON WEDNESDAY AS MRF DEPICTS ANOTHER LEESIDE TROUGH PUSHING INTO THE
WESTERN PLAINS DURING THE DAY. WITH LITTLE CHANGE IN THE RIDGE
PATTERN ALOFT...WENT SIGNIFICANTLY WARMER THAN MRF/MEX GUIDANCE FOR
HIGHS EACH DAY. LOWS SEEMED A TAD LOW IN THE LATER PERIODS...
THEREFORE WENT AT OR SLIGHTLY ABOVE GUIDANCE VALUES DURING THE
PERIOD.

.ABR...NONE.

KEEFE/ECKBERG

HAZARDOUS WEATHER OUTLOOK...UPDATED-UPGRADED RISK OF SEVERE WEATHER
NATIONAL WEATHER SERVICE ABERDEEN SD
215 PM CDT WED JUL 18 2001

MNZ039-046-SDZ005>008-010-011-017>023-191600-
BIG STONE-BROWN-CLARK-CODINGTON-DAY-DEUEL-EDMUNDS-FAULK-GRANT-
HAMLIN-MARSHALL-MCPHERSON-ROBERTS-SPINK-TRAVERSE-
INCLUDING THE CITIES OF...ABERDEEN...BIG STONE CITY...BRITTON...
CLARK...CLEAR LAKE...ESTELLINE...EUREKA...FAULKTON...GROTON...
IPSWICH...MILBANK...ORTONVILLE...REDFIELD...SISSETON...WATERTOWN...
WEBSTER AND WHEATON
204 PM CDT WED JUL 18 2001

...UPDATED HAZARDOUS WEATHER OUTLOOK THROUGH THURSDAY MORNING...
THE SLIGHT RISK OF SEVERE THUNDERSTORMS HAS BEEN UPGRADED TO A
MODERATE RISK FOR TONIGHT. SCATTERED THUNDERSTORMS ARE EXPECTED TO
DEVELOP OVER NORTHEAST SOUTH DAKOTA THIS EVENING...THEN PUSH INTO
MINNESOTA OVERNIGHT. SOME OF THE STORMS ARE EXPECTED TO BECOME
SEVERE...WITH THE PRIMARY THREAT BEING DAMAGING WINDS AND LARGE
HAIL. HEAVY RAINFALL AND DANGEROUS LIGHTNING WILL ALSO ACCOMPANY
THESE STORMS.

SPOTTER ACTIVATION MAY BE REQUIRED LATE THIS EVENING.

SDZ003-004-009-015-016-033>037-045-048-191600-
CAMPBELL-CORSON-DEWEY-HAND-HUGHES-HYDE-JONES-LYMAN-POTTER-STANLEY-
SULLY-WALWORTH-
INCLUDING THE CITIES OF...FORT PIERRE...GETTYSBURG...HIGHMORE...LOWER
BRULE...MCLAUGHLIN...MILLER...MOBRIDGE...MURDO...ONIDA...PIERRE...
PRESHO AND SELBY
215 PM CDT WED JUL 18 2001

...UPDATED HAZARDOUS WEATHER OUTLOOK THROUGH THURSDAY MORNING...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS
NORTH CENTRAL SOUTH DAKOTA. IF THUNDERSTORMS FORM...THERE IS A
CHANCE THAT A FEW OF THE STORMS MAY BECOME SEVERE.

SPOTTER \ACTIVATION MAY BE REQUIRED THIS EVENING.

ECKBERG