Severe Thunderstorm Warning 230, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1250 PM CDT THU SEP 2 1999

...FORECAST CHALLENGE...LOCATION HEAVY RAIN AND POPS IN EXTENDED...

...SYNOPSIS...QUASI-STATIONARY SURFACE FRONT/BOUNDARY FROM SE COLORADO
UP THROUGH SOUTHERN NEB...EXITS NE NEB INTO MN. UPSLOPE/ISENTROPIC
LIFT CONTINUES ALONG AND NORTH OF FRONT...SPURRING SC -SHRA IN SD/NORTH
NEB THIS MORNING. PRODUCED ABOUT .7 TO 1 INCH OF RAINFALL OVER SHERIDAN
AND WESTERN CHERRY COUNTY IN NORTHWEST CORNER OF CWA. KEEPING THIS IN
MIND FOR FFG LATER ON PER LATEST 94E GRAPHIC.

NGM PCPN FIELDS NOT BAD AT INITIALIZATION...BUT ETA A LITTLE MORE IN
LINE WITH REALITY AS FAR AS PLACEMENT OF PCPN THIS MORNING. GOING WITH
ETA FOR MOISTURE FIELDS. NGM MOVES UPPER LEVEL TROF EAST FASTER THAN
ETA THRU PD.  BELIEVE ETA TIMING BETTER ON TRACK CONSIDERING STRENGTH OF
ENERGY/DEPTH OF COLD POOL IN THE TROF WOULD TEND TO SLOW DOWN
PROGRESSION.

...TONIGHT...
ABOUT ENTIRE CWA IS IN SLIGHT RISK (94O) SO AM ANTICIPATING POSSIBLE
WATCH BOX THIS EVENING OR TONIGHT FOR PANHANDLE AND PORTIONS OF WESTERN
CWA REGION DEPENDING ON TIMING OF SHORT WAVE. LOOKS LIKE ANOTHER LATE
EVENING/NIGHT EVENT FOR OUR CWA. ALSO OUTLOOKED IN A PORTION OF
NORTHWEST CWA WITH THE 94E FOR POSSIBLE HEAVY RAINFALL. STRONG LLJ IS
PROGGED...NOSE OF IT (PER ETA) AT 06Z TNT FM OGA TO VTN. NOT SURE WE
WILL DECOUPLE MUCH UNTIL 06Z...ESPLY OVR SW PART OF CWA. UPR LEVEL
DIVERGENCE COUPLED WITH H8 CONVERGENCE OVER VTN BY 00Z...AND OVER WY/SD
THROUGH NIGHT. EXPECT ANOTHER MCS TO DEVELOP NEAR WHERE LAST NIGHT'S
DID. PER COORDINATION WITH HSI...LOOKS LIKE LAST NIGHT/S MEAN WIND WAS
STRONGER THAN LLJ...AND THEREFORE RESULTED AS THE MAIN STEERING
MECHANISM FOR MCS THAT DEVELOPED (RATHER THAN THE CORFIDI VECTORS WHICH
WOULD HAVE TAKEN SYSTEM SOUTHEAST.) LLJ IS ALSO PROGGED TO STRENGTHEN
TONIGHT. ETA PROGS 850 WINDS TO BE STRONGER THAN H7 OR H5 BY 06Z FRI SO
ANY MCS WHICH DEVELOPS MAY TAKE A SOUTHEASTERN TRACK.

...FRIDAY/NIGHT...LOOKING PRETTY GOOD FOR YET ANOTHER ROUND OF PCPN.
SOME LINGERING SHRA PERHAPS IN NORTHEAST COUNTIES (ANW ONL) IN THE
MORNING. SFC FRONT WAFFLES AROUND SOME AS USUAL SO EXACT PLACEMENT OF
PCPN IS DIFFICULT...BUT APPEARS TO SHIFT SOUTH.  ETA BULLSEYES KEARNEY
BY FRI AFTERNOON LATE UNTIL ABOUT SAT MORN. SFC LOW MOVES TOWARDS GARDEN
CITY KS FM ERN CO. AVN/ETA DISAGREE ON PCPN FIELDS OVER CWA
FRIDAY...BUT THEN SIMILAR AGAIN BY SATURDAY MORNING.

...SATURDAY...LOOKS LIKE THE AREA BEGINS TO DRY OUT WITH SFC RIDGING
TAKING PLACE BEGINNING IN THE NW. CAA AT 850 WILL KEEP US SOMEWHAT
COOLER...BUT STILL THINK LBF HIGH OF 66 (PER MRF) IS TOO COOL. LIKE FWC
GUIDANCE OF AROUND 80. HIGH PUSHES EVERYTHING OFF TO THE SOUTH.

EXTENDED...PREFER MRF SOLUTION SINCE ECMWF DATA LIMITED. MRF IS ALSO
SOMEWHAT MORE CONSISTENT WITH PREVIOUS PATTERN...IS REDEVELOPING SIMILAR
PATTERN NEXT WEEK THAT WE HAVE BEEN SEEING THIS SUMMER WITH SFC LOW
FORMING OVER ERN CO UNDER RIDGE ALOFT NEXT TUESDAY LATE. MODELS AGREE
SUNDAY LOOKS DRY...WITH EXCEPTION OF FAR NORTHWEST CORNER OF CWA.
MONDAY IS LOOKING PRETTY DRY NOW ALSO...AND POSSIBLY DRY THROUGH ALL OF
TUESDAY. CLIMATE AVERAGES FOR HIGH TEMPS LOOK OK. KEEPING LOWS UdP A
TAD.

.LBF...NONE

SLM