Severe Thunderstorm Warning 86, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/N-EAST SD AND W-CENTRAL MN
NATIONAL WEATHER SERVICE ABERDEEN SD
200 PM CDT FRI JUL 5 2002

MAIN FORECAST CHALLENGE IS THE CHANCE FOR THUNDERSTORMS LATER
TONIGHT THROUGH SUNDAY. 19Z SURFACE ANALYSIS SHOWED LOW PRESSURE
CENTERED OVER EXTREME NORTHWESTERN SOUTH DAKOTA/SOUTHWESTERN NORTH
DAKOTA. THE COLD FRONT WITH THIS LOW WAS THROUGH JUST THE VERY
NORTHWESTERN CORNER OF THE STATE. THIS FRONT WILL BE THE MAIN FOCUS
FOR ANY CONVECTIVE DEVELOPMENT THROUGH THE WEEKEND AS IT BECOMES
STATIONARY ALONG THE NORTH DAKOTA/SOUTH DAKOTA BORDER BY SATURDAY
MORNING. RIGHT NOW IT APPEARS THE BEST UPPER ENERGY WILL STAY TO THE
NORTH OF THE FRONT AS A LARGE UPPER HIGH REMAINS SETTLED IN OVER THE
CENTRAL AND SOUTHERN PLAINS. WILL GO WITH JUST A SLIGHT CHANCE OF
STORMS IN THE WESTERN CWA LATER TONIGHT AS THE FRONT
APPROACHES...WITH SOME INCREASE IN DEWPOINTS NOTED IN THAT REGION.
WILL THEN KEEP THE NORTHERN CWA UNDER A CHANCE OF STORMS ON SATURDAY
DUE TO THE STATIONARY FRONT BEING SET UP RIGHT IN THAT AREA. MID
LEVEL WINDS BECOME SOUTHERLY OVER THE WESTERN CWA SATURDAY
NIGHT...BUT WILL BE OUT OF THE WEST TO NORTHWEST IN THE EASTERN PART
OF THE CWA...WHICH MAY ALLOW A FEW STORMS TO DRIFT INTO THAT REGION.
ON SUNDAY...THE FRONT BEGINS TO MOVE SOUTHWARD AGAIN AS A COLD
FRONT...SO WILL CARRY A CHANCE OF STORMS FOR THE ENTIRE CWA. THE
FRONT WILL THEN BE WELL SOUTH OF THE STATE SUNDAY NIGHT INTO MONDAY
WITH HIGH PRESSURE MOVING IN OUT OF CANADA...KEEPING THE EARLY PART
OF THE WEEK DRY.

.EXTENDED DISCUSSION...
OVERALL...EXTENDED MODELS MAINTAIN A RIDGE JUST WEST OF THE CWA
THROUGH DAY 7. SOME VARYING DEGREES OF STRENGTH TO THIS RIDGE WITH A
GENERAL TREND TOWARD FLATTENING THE RIDGE BY DAY 7. AVN DOES TRY TO
DRAG A SFC BOUNDARY THROUGH THE CWA TUES. THIS IS THE FIRST
INDICATION OF THIS FEATURE AND AM INCLINED TO DISCOUNT IT ATTM GIVEN
FAIRLY WARM H7 TEMPS AND BEST MID LVL OMEGA REMAINING NORTH OF THE
CWA. WITH RIDGE TO THE WEST AND GENERAL NW FLOW OVER THE REGION
WOULD NOT BE SURPRISED TO SEE SHORT WAVES DROP INTO THE FAR NE
PORTION OF THE CWA AT ANY TIME DURING THE EXTENDED PERIOD...BUT HARD
TO TIME THESE. ENSEMBLES INDICATE CONTINUED LOW POPS FOR EVEN LIGHT
QPF THROUGH THE PERIOD WITH GOOD AGREEMENT AMONG THE MEMBERS
REGARDING PLACEMENT AND STRENGTH OF THE RIDGE TO THE WEST. WITH THE
INITIAL BREAKDOWN OF THE RIDGE SHOWING UP BY DAY 7 WE SHOULD SEE A
BETTER CONDITION FOR SHORT WAVES TO INTRUDE INTO NRN SECTIONS BY
LATE FRIDAY...BUT FOR NOW WILL LEAVE EXTENDED DRY. IF NEXT MODEL RUN
HOLDS ON TO SFC BOUNDARY TUESDAY...MAY NEED TO ADD POPS NE. GIVEN
PRESENCE OF THE RIDGE THROUGH THE FORECAST WILL GO SLIGHTLY ABOVE
GUIDANCE FOR TEMPS.

.ABR...NONE.

PARKIN/FAUCETTE