Severe Thunderstorm Warning 138, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
345 AM CDT TUE AUG 3 2004

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT
FORECAST CHALLENGE WILL BE TIMING THE END OF MORNING CONVECTION AND
WHEN NEXT ROUND BEGINS TODAY. TRICKY TEMP FORECAST AS WELL.

MORNING MCS/MINI-BOW ECHO NOW APPROACHING WESTERN CWA FRINGE. THIS
CLUSTER OF STORMS SHOULD CONTINUE TO PROPAGATE ALONG STATIONARY
BOUNDARY DRAPED ACROSS WESTERN SODAK SEWD INTO NORTHEAST NE...WHERE
BEST POOLING OF LOW LEVEL MOISTURE AND MID-LEVEL INSTABILITY RESIDE.
SVR T-STORM WATCH NUMBER 693 IN EFFECT UNTIL 8 AM CDT FOR CENTRAL/SC
SODAK.

THOUGHTS SURROUNDING DAY 1 TEMP FORECAST MAINLY CONCERNED WITH
CONVECTIVE DEBRIS CLOUDINESS AND COOL OUTFLOW BOUNDARY LAYER
INHIBITING REALIZATION OF A FULLY-MIXED/FULL INSOLATION DAY. KNOCKED
SEVERAL DEGREES OFF OF 850HPA PROGGED MAX T ACROSS NW CWA AS A
RESULT. ALSO...GFS AND ETA 00Z RUNS COMING IN MUCH COOLER FOR DAY 2
AND DAY 3 WITH 850HPA THERMAL PROGS COOLING INTO +10 TO +15C
RANGE...WHICH WOULD READ AS LOWER 70S FOR HIGHS. MET GUIDANCE
SUPPORTING THAT IDEA...BUT OPTED TO ONLY SHAVE ABOUT A CATEGORY OF
TEMPERATURE OFF OF MAX T GRID. TEMPS MAY STILL NEED TO BE KNOCKED
DOWN SOME MORE.

S/WS ABOUND ACROSS INTERMOUNTAIN WEST AND NORTHERN PLAINS THIS
MORNING THROUGH LATE THIS EVENING. NEXT S/W OF CONCERN LIFTING INTO
MT IN SW FLOW ALOFT...AND SHOULD BE SLAMMING INTO CWA JUST ABOUT OR
SHORTLY AFTER PEAK HEATING TODAY. LOW LEVELS ON ENERLY FLOW SLOW TO
DRY OUT TODAY...SO ONE MORE DECENT SHOT FOR MEASURABLE PRECIP...WITH
FOCUS TONIGHT BEING SHIFTED APPX 100 MILES EAST OF WHERE PRECIP IS
FALLING THIS MORNING...AS PER GFS AND ETA PROGGED MID-LEVEL LIFT AND
UPPER LEVEL JET SUPPORT. NUMEROUS OUTFLOW BOUNDARIES NOTED ON
REGIONAL 88DS...SO ONE WOULD THINK THE LOW LEVEL FOCUS MECHANISMS
WILL BE HANGING AROUND TO INITIATE TS AGAIN BY LATE THIS AFTERNOON.
BY 12Z WEDNESDAY...MAJORLY DRIED OUT LOW LEVELS COMBINED WITH
STABILIZING AFFECT OF COOLER AIR IN SFC TO 700HPA LAYER SHOULD SPELL
AN END TO PRECIP POTENTIAL THROUGH THE REMAINDER OF SHORT TERM...AS
CANADIAN SFC HIGH STILL PROGGED TO SET UP CAMP ACROSS CWA.

.LONG TERM...FRIDAY THROUGH MONDAY
FEW CHANGES TO THE MEDIUM RANGE.  FRIDAY MORNING OPENS WITH A LEE
SIDE UPPER TROUGH AND AN OLD LOW OVER THE EASTERN UNITED STATES.
SURFACE FLOW FROM THE SOUTH AND A GRADUAL H5 HEIGHT RISE WILL ALLOW
AIR TO BECOME MORE UNSTABLE.  WENT ALONG WITH CHANCE OF
THUNDERSTORMS FRIDAY NIGHT AND SATURDAY MORNING.  ANOTHER CHANCE
SATURDAY AFTERNOON AS COLD FRONT ASSOCIATED WITH H5 LOW MOVING
THROUGH THE RIDGE SATURDAY.  CHANCE OF THUNDERSTORMS WILL LAST INTO
SUNDAY MORNING AS COLD FRONT PASSES.  UPPER RIDGE THEN TRIES TO
REESTABLISH BUT AT TIMES MORE RESEMBLES FAST WESTERLY PATTERN.

&&

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

DORN/KEEFE