Severe Thunderstorm Warning 142, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
300 PM CDT SUN SEP 3 2000

LOWS CLOUDS CONTINUE TO LINGER OVER SECTIONS OF NORTH CENTRAL AND
NORTHEAST SOUTH DAKOTA THIS AFTERNOON. TEMPERATURES RANGED FROM THE
60S IN THE FAR NORTHEAST TO THE LOW TO MID 90S IN THE CENTRAL.
LATEST SATELLITE IMAGES INDICATED THAT LOW CLOUDS HAVE STARTED TO
MOVE SLOWLY WESTWARD TOWARD WATERTOWN OVER THE LAST HOUR OR TWO.
THINK THE CLEAR CONDITIONS FROM WATERTOWN TO NEAR REDFIELD WILL NOT
LAST TO LONG AND WILL JUST WORD THE ZONEGROUP CLOUDY. OTHERWISE...A
SHORTWAVE OVER THE CENTRAL PLAINS IS KICKING OFF SHOWER AND
THUNDERSTORM ACTIVITY IN NEBRASKA AND EXTREME SOUTHERN SOUTH DAKOTA
THIS AFTERNOON. THIS SYSTEM IS PROGGED TO MOVE NORTHEAST AND BRING A CHANCE
OF THUNDERSTORMS TONIGHT ACROSS THE CENTRAL AND MAINLY AFTER
MIDNIGHT ELSEWHERE. LIFTED INDICIES DROP TO AROUND -5 IN THE CENTRAL
WHILE LIFTED INDICIES IN THE FAR NORTHEAST ARE WELL ABOVE ZERO.
CAPES WERE IN THE ORDER OF 1000 TO 2000 J/KG. ONLY MENTIONED
THUNDERSTORMS IN THE CENTRAL AND SHOWERS AND THUNDERSTORMS IN THE
NORTH AND EAST WHERE STABLE AIR MASS IS IN PLACE. OTHERWISE...
UNSETTLED PERIOD CONTINUES INTO TUESDAY AS 500MB TROUGH ACROSS THE
WESTERN UNITED STATES REMAINS STATIONARY WHILE SHORTWAVES EJECT OUT
OF THE TROUGH INTO THE NORTHERN PLAINS. ETA/NGM/AVN ARE FAIRLY
SIMILIAR WITH THESE FEATURES WHILE TIMING THESE SYSTEMS WILL BE
DIFFICULT. CHANCE FOR PRECIPITATION LINGERS IN THE MORNING IN THE
NORTH AND EAST ON MONDAY...THEN THE SKY SHOULD BECOME PARTLY SUNNY IN THE
AFTERNOON MOST PLACES AS THE MODELS SHOW THAT THE LOW LEVEL MOISTURE
DECREASES DURING THE DAY. ANOTHER SHORTWAVE MOVES INTO THE REGION
LATE MONDAY AFTERNOON AND TUESDAY BRING ANOTHER CHANCE OF RAINFALL
MONDAY NIGHT INTO TUESDAY. MODELS CONTINUE TO SHOW THE BEST
INSTABILITY ACROSS THE CENTRAL. WITH SURFACE BOUNDARY REMAINING
ACROSS THE CWA...A WIDE RANGE OF HIGH TEMPERATURES CAN BE EXPECTED
ON BOTH LABOR DAY AND TUESDAY. TEMPERATURES IN THE NORTHEAST WILL
ONLY WARM INTO THE 70S WHILE TEMPERATURES WARM INTO THE 90S IN THE
CENTRAL.

.EXTENDED FORECAST...
EXTENDED MODELS SHOW THAT PERSISTANT WEST COAST TROF FINALLY MOVES
EAST..FLATTENING MIDWEST RIDGE AS IT MOVES UP AND OVER. MOST OF THE
MODELS ARE IN AGREEMENT THROUGH EXTENDED PERIOD...BUT THERE IS SOME
DISCORD...ESPECIALLY ON THURSDAY. BACKING UP...WEDNESDAY THE
LONGWAVE TROF MOVES EAST THROUGH CWA. SFC REFLECTION IS STRONG
CANADIAN LOW WITH WEAKER CLOSED LOW IN NEBRASKA...AND COLD
FRONT/TROF BETWEEN THEM. HI PWATS AHEAD OF SYSTEM LEAD TO CONT CLOUD
COVER UNTIL THIS MOVES THROUGH. MRF/NOGAPS/CANADIAN ALL AGREE ON
INCREASING 7H MOIST DURING NIGHT ON TUESDAY AS FRONT
APPROACHES...WITH LIFT ARRIVING BETWEEN 06Z-12Z WED FOR KMBG AND
KPIR AREAS...AND 12-18Z FOR KABR AND KATY AREAS. PCPN IS FCST BY
MDLS...WTH HEAVIEST ACROSS NORTH AND NE. BY 00Z THURSDAY...STRONG
DRYING SEEN AT 7H AND BOUNDARY LAYERS AS SUBSIDENCE AND HIGH
PRESSURE INVADES CWA. WILL ADD TUESDAY NIGHT GROUP TO EXTENDED TO
HELP COVER TSRA CHANCES. ON THURSDAY...MOST MODELS AGREE IN KEEPING
HIGH PRESSURE IN CONTROL WITH DRY NATURE TO ATMOS. THE ODD-BALL TO
THIS IS THE NOGAPS. THE NOGAPS STALLS THE NEBRASKA LOW DURING NIGHT
ON WEDNESDAY...ALLOWING IT TO STRENGTHEN. THIS KEEPS PCPN IN FCST
THROUGH THURSDAY ACROSS MOST OF CWA. DUE TO AMPLIFIED NATURE OF
PATTERN...SEE NO REASON WHY FRONT AND LOW WOULD STALL. WILL GO WITH
MORE PROGRESSIVE NATURE OF CANADIAN/MRF/UK ON HIGH PRESSURE
REMAINING WITH NEUTRAL TEMP ADVECTION. 5H RIDGE BUILDS BACK TO OUR
WEST ON THURSDAY...KEEPING NW FLOW OVER CWA. FOR FRIDAY...HIGH IS
EAST WITH RETURN FLOW AND WAA RETURNING BACK TO WRN CWA. 700MB RH
STAYS DRY AS DOES BOUNDARY LAYER RH. CANADIAN IS HINTING AT
SOMETHING MOVING IN AROUND 00Z FRI...BUT THAT FAR OUT WILL IGNORE
AND WATCH AS WE GET CLOSER. FMR/MEX TEMPS LOOK REASONABLE GIVEN
COOLISH NATURE TO 700MB AND 850MB TEMPS.

.ABR...NONE

ECKBERG/HINTZ