Severe Thunderstorm Warning 170, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
2 PM CDT SAT JUL 28 2001

MAIN ISSUE IS THE OLE SUMMERTIME FAVORITE AND MOST DIFFICULT TO
FORECAST...CONVECTION. FOR TONIGHT SUSPECT THAT SMALL VORT MOVING
ACROSS SOUTHERN ND WILL HAVE LITTLE IF ANY EFFECT ON REGION. WEAK
ACTIVITY CONTINUES NORTH OF THE SD/ND BORDER BUT IS HAVING A HARD
TIME DEVELOPING ANY FURTHER SOUTH. ATTENTION TURNS WEST AND TO THE
NEXT S/W VERY EVIDENT IN SAT PIX OVER NE WY. MODELS HAVE PICKED UP
ON THIS FEATURE BUT GENERALLY DAMPEN IT. HOWEVER WITH CAP STILL NOT
FIRMLY ESTABLISHED...DEVELOPMENT OF LLJ AND INCREASING BOUNDARY
LAYER MOISTURE...FEEL THAT LOW SCT POP IS JUSTIFIED AND WILL
CONTINUE THIS IN FORECAST. SMALL CHANCE OF LINGERING ELEVATED
ACTIVITY IN EASTERN CWA SUNDAY MORNING OTHERWISE FEEL CAPPING WILL
HOLD ACTIVITY AT BAY OVER THE CWA FOR THE REMAINDER OF THE DAY. AS
PERTAINS TO SFC FRONTAL MOVEMENT...ETA PROBABLY TOO AGRESSIVE AND
FAST MOVING FEATURE TO THE EAST...PREFER THE AVN. OF COURSE SFC
FRONTAL POSITION PLAYS TRUE HAVOC WITH LATITUDINAL POSITIONING OF
ANY MCS THAT MIGHT FORM SUNDAY NIGHT AND/OR MONDAY NIGHT. AND
ETA/AVN ARENT PARTICULARY CLOSE. WILL BROAD BRUSH MOD SCT POP BOTH
NIGHTS. FRANKLY THE CONFIDENCE FACTOR IS QUITE LOW WITH THE
THUNDERSTORM CHC PLACEMENT. ONCE AGAIN HAVE GONE CLOSER TO WARMER
FWC GUIDANCE WHICH IS SUPPORTED BY QUITE WARM 8H TEMPS.

.EXTENDED DISCUSSION...
BROAD SOUTHWEST UPPER FLOW WILL CONTINUE TO BE A THORN IN THE
FORECASTERS SIDE THROUGH THE EXTENDED. MODELS HAVE BACKED OFF
(ESPECIALLY ECMWF) IN BUILDING UPPER RIDGE AND ARE NOW GEARED MORE
TOWARD MID TO LATE NEXT WEEK WITH THE MAJOR MID/UPPER LEVEL HEIGHT
RISES AND RETROGRESSION. ALSO FEEL THAT MRF MIGHT BE TOO
ENTHUSIASTIC WITH EASTWARD PROGRESSION OF THE SFC FRONT. THEREFORE
WILL HOLD BACK FRONT AND KEEP PCPN MENTIONED FOR WED. HOPEFULLY FOR
FRIDAY AND SATURDAY THE MID LEVEL RIDGE WILL HAVE BUILT BACK ENOUGH
TO SQUASH ANY CONVECTIVE CHANCES. AS USUAL MEX TEMPS WERE A LITTLE
TOO COOL.

.ABR...NONE.
TDK

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