Flash Flood Warning 5, NWS Rapid City, SD

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
230 PM MDT SAT AUG 24 2002

MID LEVEL CIRCULATION SEEN IN WATER VAPOR PICS OVER SRN MT...WITH
TROF AXIS EXTENDING SEWD INTO WRN NEB. JET STREAK IS NOW ENTERING
WRN WY. CONVECTION ALREADY FIRING OVR WRN HALF OF CWFA WHERE CAPPING
INVERSION HAS WEAKENED SIGNIFICANTLY. HOWEVER...MID/HI LVL CLDS HAVE
KEPT CAP IN PLACE OVR WRN SD PLAINS. CONCERNS EVE REMAIN HEAVY RAIN
POTENTIAL WITH SLOW STORM MOTIONS...MAINLY EARLY THIS EVE...AS WELL
AS LARGE HAIL.

MID LEVEL TROF AXIS WILL LIFT SLOWLY NEWD ACRS CWFA THIS EVE. PLENTY
OF UVV WILL BE GENERATED FOR WIDESPREAD CONVECTIVE ACTIVITY. SHEAR
VALUES ARE MINIMAL ACRS FAR NERN ZONES...BUT INCREASE IN VALUE
TOWARDS THE SWRN ZONES. THEREFORE...EXPECT MOST INTENSE ROTATING
UPDRAFTS TO REMAIN OVR OR JUST SOUTH OF SWRN ZONES.
HOWEVER...POTENTIAL STILL IN PLACE FOR LOCALLY HEAVY RAINS AS STORM
MOTIONS WILL BE VERY SLOW...AND ALSO FOR LARGE HAIL WITH MID LVL
COLD POCKET AND LOW WET-BULB ZERO TEMPS. THE ACTIVITY WILL COME TO
AN END LATER THIS EVE IN THE SW...AND LIKELY CONT THRU THE NIGHT IN
THE NE.

NRN STREAM TROF WILL WORK SLOWLY EWD THRU NRN PLAINS/SRN CANADA
REMAINDER OF 3 DAY FCST. THIS WILL KEEP CWFA UNDER SW FLOW ALOFT FOR
CONTD UNSETTLED WX AND NEAR CLIMO TEMPS. HOWEVER...HEAVY RAIN THREAT
APPEARS TO DECREASE AS PRECIP H20 VALUES LOWER AND FASTER MID LVL
FLOW RETURNS.

EXTENDED...MED RANGE GUIDANCE SUGGESTS PAC COAST TROF MOVG LITTLE
THRU THU...THUS KEEPING CWFA IN UNSETTLED PATTERN. IT IS DIFFICULT
TO TIME SHORT WAVES SO WILL KEEP CHC PCPN IN FCST THU DAY 5. WEAK
RIDGING MAY CUT OFF MOISTURE SOURCE TOWARDS END OF WEEK.

.UNR...FLOOD WATCH CONTINUES UNTIL SAT EVE FOR BLKHLS PORTIONS OF
       LAWRENCE COUNTY.

JOHNSON