Severe Thunderstorm Warning 141, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
218 PM CDT THU AUG 8 2002

...FIRST FORECAST CONCERN REVOLVES AROUND FROPA & POPS TONIGHT
FOLLOWED BY THE BIG PATTERN CHANGES IN THE EXTENDED...

SYNOPSIS...LATE MORNING SFC ANALYSIS HAS 1012 LOW OVER ND WITH COLD
FRONT/LEE TROUGH STRETCHING SOUTH THROUGH WESTERN SOUTH DAKOTA
ALONG THE NE/WY BORDER.  AT H5 A FAIRLY STRONG TROUGH OVER ID WITH
30 GPM HEIGHT FALLS OUT AHEAD OF IT.  45KT MID LEVEL JET CURRENTLY
ROTATING AROUND THE BASE OF THIS TROUGH SO PROBABLY NOT GOING TO
DEEPEN ALL THAT MUCH MORE IN THE SHORT TERM.  UPPER LOW IS CUT
OFF AT H3 WITH 70 GPM HEIGHT FALLS TO THE EAST OF IT AND 70-80KT
JET ROUNDING THE BASE OF THE UPPER LOW.

SHORT TERM...SFC LOW OVER THE DAKOTAS WILL DRAG THE FRONT THROUGH
THE AREA OVERNIGHT.  LEAD S/W CAUSING CONVECTION TO FIRE FROM VTN-IML
AS OF 19Z WILL GO SCT NE POPS ALONG/AHEAD OF STORMS. WILL MAKE
LAST MINUTE DECISION...BUT CARRY POPS ELSEWHERE WITH SUBSIDENCE
BEHIND LEAD S/W PROBABLY PRECLUDING MUCH EVENING DEVELOPMENT BEHIND
THE INITIAL LINE. ON THE UPSIDE FOR THUNDERSTORMS OVERNIGHT INCLUDE
THE DECENT MOISTURE POOLING OUT AHEAD OF THE FRONT...DECENT
CONVERGENCE ALONG THE FRONT...MODERATE INSTABILITY.  ON THE DOWN SIDE
FOR TONIGHT THE FRONT MOVING THROUGH AT A DIURNAL DOWN-TIME FOR
CONVECTION...WEAK WIND FIELD NOT FAVORING ORGANIZED CONVECTION...AND
OF COURSE WE ARE IN A DROUGHT WITH ALL THAT IN MIND WILL PROBABLY GO
WITH 30-40 POPS FOR TONIGHT...BUT WILL REVIEW RADAR TRENDS AND
18Z ETAX PRIOR TO ISSUANCE.  FRONT SHOULD CLEAR THE CWA BY AROUND 12Z
WITH SOME MOISTURE LINGERING BEHIND THE FRONT...MAINLY EARLY.  WILL
LEAVE SLIGHT CHANCE POPS FOR TOMORROW AM SE 1/2 CWA NOT TOO EXCITED
ABOUT RAIN WITH BEST FORCING WELL SOUTH OF THE AREA.

SHOULD BE DRY WITH NEAR SEASONAL TEMPS FRIDAY NIGHT THRU SAT NIGHT
AS THE SFC RIDGE PASSES OVER THE AREA.  SHOULD BE FAIRLY COOL FRI
NIGHT AS SFC RIDGE BUILDS IN.  STILL SOME GRADIENT FRI NIGHT SO NOT
GOING TO STRAY TOO FAR FROM GUIDANCE...BUT IF RIDGING MOVES IN A
LITTLE FASTER MAY SEE FEW AREAS IN NW CWA DROP INTO THE 40S

NEXT ISSUE IS WITH SUNDAY TEMPERATURES...ETAX HAS 2M TEMPS AROUND
100 FAR SOUTH AND WELL INTO THE 90S ELSEWHERE.  WITH LEE TROUGH
PUSHING INTO THE WESTERN AREAS BY LATE AFTERNOON AND WITH THE GOOD
TRACK RECORD OF THE ETA 2M THIS SEASON WILL GO AHEAD AND GIVE TEMPS
A HEALTHY BOOST ON SUNDAY AFTERNOON AS SUMMER TAKES ITS LAST SHOT AT
THE AREA FOR A WHILE IF YOU BUY INTO THE MEDIUM RANGE MODELS...

EXTENDED DISCUSSION...QUICK COMPARISON OF THE GLOBAL MODELS DOES
REVEAL SOME DIFFERENCES WITH AMPLITUDE AND TIMING WITH H5 PATTERN
NEXT WEEK. THE ECMWF AND THE GLOBAL BOTH SEEM TO BE IN FAIR AGREEMENT
ON DEVELOPING A MID-CONTINENTAL LONG WAVE TROUGH NEXT WEEK WITH
RIDGING INTO THE GULF OF ALASKA AND ALSO OVER THE EAST COAST. WILL
GENERALLY FOLLOW THE GLOBAL MODEL AS THE RUN TO RUN CONSISTENCY HAS
BEEN FAIRLY GOOD AT H5.

LAST COUPLE RUNS OF THE GLOBAL HAVE BEEN QUITE CONSISTENT WITH
REGARDS TO TIMING OF THE FROPA SCHEDULED FOR SUN NIGHT.
INITIAL THOUGHT WAS THAT THE FROPA WOULD BE DELAYED SOME BASED
ON THE ENSEMBLES LESS PROGRESSIVE SOLUTION...BUT AFTER LOOKING
AT THE ETAX AND THIS MORNINGS AVN WILL GO AHEAD AND KEEP HE
FROPA SUN NIGHT.  BEST CHANCE OF PRECIP WILL PROBABLY BE SUN NIGHT
WITH MOST OF THE CWA DRY MONDAY.  WILL PROBABLY HANG ONTO SLIGHT
CHANCE FAR EAST.  FRONT IS FORECASTED TO MAKE SOME FAIRLY
DECENT PROGRESSION SOUTHWARD AS RIDGING BUILDS IN FROM CANADA.  MODEL
QPF SEEMS WAY OVERDONE THIS FAR NORTH BEHIND THE FRONT IN TUE/WED
TIME FRAME.  AT THIS POINT I REALLY DONT SEE A STRONG ARGUMENT TO
INTRODUCE POPS THIS FAR OUT SO WILL GO WITH A DRY FORECAST THROUGH
THURS.

AS FAR AS TEMPS GO...THIS RUN IS MUCH FURTHER SOUTH AND COOLER IN THE
TUES-THUR TIME FRAME. SUPPORT FROM THE VARIOUS ENSEMBLE MEMBERS IS
QUITE STRONG FOR A SIGNIFICANT COOL DOWN NEXT WEEK.  NEARLY THREE
FOURTHS OF THE MEMBERS IN THE ENSEMBLE SUITE ARE ADVERTISING H8
TEMPS MORE THAN 1 STANDARD DEVIATION BELOW NORMAL.  COOLEST DAYS
LOOK TO BE TUE/WED WITH H8 TEMPS PROGGED TO RANGE FROM AROUND 10
EAST TO AROUND 16 IN THE PANHANDLE TUES EVENING AND WED EVENING. H8
TEMPS THIS LOW WOULD SUPPORT HIGHS IN THE LOW 70S. HOWEVER GOING
FORECAST ALREADY HAS TEMPS ABOUT 10+ DEGREES BELOW CLIMO AND GIVEN
THE COOL BIAS OF THE MODEL THIS SEEMS FAIRLY REASONABLE FOR NOW.
WILL BEGIN A SLIGHT MODERATING TREND WITH THE INTRODUCTION OF THURS
INTO THE ZFP.

.LBF...NONE.

IZZI/KECK

NEZ004>010-022>029-035>038-056>059-069>071-094-082045-

HAZARDOUS WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1054 AM CDT THU AUG 8 2002

...THERE IS A RISK OF SEVERE THUNDERSTORMS IN WESTERN AND NORTH
CENTRAL NEBRASKA THIS AFTERNOON AND TONIGHT...

A TROUGH OF LOW PRESSURE MOVING SLOWLY TO THE EAST OVER WESTERN
AND NORTH CENTRAL NEBRASKA THIS AFTERNOON WILL BE THE FOCUS FOR
SEVERE THUNDERSTORM DEVELOPMENT THIS AFTERNOON AND TONIGHT. SOME
THUNDERSTORMS MAY BE SEVERE WITH DAMAGING WIND. STORM SPOTTER
ACTIVATION MAY BE NECESSARY THIS AFTERNOON AND TONIGHT. THE PRIMARY
RISK OF SEVERE WEATHER IS ALONG AND EAST OF A LINE FROM CODY...IN
NORTHERN CHERRY COUNTY...TO CHAPPELL IN DEUEL COUNTY...IN THE
SOUTHERN NEBRASKA PANHANDLE.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
255 PM CDT THU AUG 8 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

153 PM     VALENTINE                 NE   62 MPH TSTM GUST
08/08/02   CHERRY

232 PM     VALENTINE                 NE   0.75 INCH HAIL
08/08/02   CHERRY

CLB