Severe Thunderstorm Warning 161, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
235 AM CDT SUN AUG 11 2002

FORECAST CHALLENGE TO BE PLACEMENT OF POPS THIS AFTN AND EVENING...

ONGOING UPPER AIR SYNOPSIS TONIGHT HIGHLIGHTED BY CUTOFF LOW OVER
WRN ONTARIO...ANOTHER OVER WRN ALBERTA AND A COUPLE OF SW TROFS TO
NOTE...ONE OVER NERN MT AND THE OTHER SKIRTING ACROSS THE FA
TONIGHT. THE LATTER HAS FIRED OFF SEVERAL TSRAS AS IT INTERACTED
WITH A SURFACE BOUNDARY ANCHORED FROM AIA TO OFK. TREND OVERNIGHT IS
FOR BOUNDARY TO CONTINUE TO LIFT NWD INTO SRN SD BY SUNRISE. MAIN DILEMMA
FOR FCST WILL BE PLACEMENT AND TIMING OF PRE FRONTAL TROF EXPECTED
TO EXTEND FROM THE CENTRAL DAKOTAS INTO THE SW FA BY THIS AFTN.

TODAY AND TONIGHT...BEFORE MENTIONED SFC BOUNDARY LIFTS INTO SERN SD
BY AFTN. SOUTH OF THE BOUNDARY...ETA ADVERTISED SFC DEW POINTS IN
THE 50S SEEM REASONABLE. PREFRONTAL TROF APPROACHES FA BY 18Z AND
EXTENDS FROM VTN TO IML BY 21Z. SHOULD SEE TEMPS WARMEST W AND ALONG
THIS BOUNDARY AS THEY WILL REAP BENEFIT OF SWRLY FLOW. ALONG AND
JUST EAST OF THE PRE FRONTAL TROF...SOUNDINGS INDICATING ELEVATED
INSTABILITY WHICH SPELLS ONLY ISOLATED PCPN. WILL GO WITH A DRY
FCST W OF A LINE FROM VTN TO LBF WITH ISOLATED ALONG AND EAST OF
THIS LINE AND SCATTERED IN THE NERN ZONES WHERE THE BEST LOW LEVEL
MOISTURE...UPPR DYNAMICS...AND RESIDUAL SFC BOUNDARY WILL BE FOUND.
PRE FRONTAL TROF CLEARS CWA BY MID EVENING...THEN FRONT PASSES ON
ITS HEELS AND CLEARS CWA BY 12Z. WINDS COULD BE AN ISSUE TOMORROW
MORNING. 3 HR PRESSURE RISES OF 5-7 MB BEHIND THE FRONT WILL FORCE
NRLY WINDS OF 25 TO 35 MPH. THE INCREASED SPEEDS WILL BE BRIEF AS
PRESSURE RISES RELAX SUBSTANTIALLY FARTHER BEHIND THE FRONT.

MONDAY AND TUESDAY...AFTER A WINDY START EARLY MONDAY...SHOULD SEE A
DRY FCST WITH FRONT PUSHED WELL INTO KANSAS. ETA INDICATING SOME MID
AND HIGH CLOUDINESS INITIALLY POST FRONTAL...AND CONVECTIVE
CLOUDINESS IN THE AFTN. WITH EXPECTED H5 TEMPS OF -12C
EXPECTED...STEEPENING LAPSE RATES WILL MAKE THIS A REALITY. MAY NEED
TO UNDERCUT GUIDANCE A TAD FOR CLOUDINESS. VERY DRY SFC DEW POINTS
MON NIGHT INDICATIVE OF FORTIES ACROSS THE FA. ETA EXTENSION AND AVN
BEGIN TO DIVERGE SIGNIFICANTLY ON TRACK OF SFC HIGH ON TUESDAY. AVN
SOLN TAKES HIGH WELL SOUTH INTO ERN COLORADO WHILE THE ETA EXTENSION
WASHES THIS OUT PLACING THE FA IN ERLY AN SERLY FLOW. PREFER A
COMPROMISED SOLN HERE WITH HIGH DIVING SOUTH INTO COLORADO...HOWEVER
BELIEVE H85 TEMPS STILL WAY TOO COOL.

WEDNESDAY AND BEYOND...CONFIDENCE IS LOW IN THE WEDNESDAY NIGHT
FCST. AVN IS TRENDING FARTHER NORTH WITH THE UPPR LOW. H5-H10
THICKNESSES INDICATIVE OF VERY LIMITED CAA ACROSS THE NRN TIER...SO
FRONT MAY HAVE A DIFFICULT TIME MAKING ITS WAY INTO THE NRN CWA.
WITH MAJOR RUN TO RUN INCONSISTENCIES...WILL LEAVE PD ALONE FOR NOW.
WITH NEW AVN ADVERTISING A MORE ZONAL PATTERN...NO SURPRISE IT IS
SUBSTANTIALLY WARMER IN THE LOWER LVLS ON THURSDAY...DRY FCST ON
TRACK IN ALL AREAS EXCEPT THE NE EARLY AND WILL NOT MODIFY IT. WILL
EXAMINE NEW MRF AND MAKE MODIFICATIONS AS NECESSARY TO ONGOING
PKG.

.LBF...NONE.

CLB

NEZ004>010-022>029-035>038-056>059-069>071-094-111630-

HAZARDOUS WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
540 AM CDT SUN AUG 11 2002

...SEVERE THUNDERSTORMS ARE POSSIBLE TODAY IN WESTERN AND NORTH
CENTRAL...

THERE IS A RISK OF SEVERE THUNDERSTORMS TODAY EAST OF A LINE FROM
VALENTINE TO IMPERIAL. A TROUGH AND FRONT IN NEBRASKA THIS AFTERNOON
AND EVENING WILL GENERATE THUNDERSTORMS. WITH EXTREMELY UNSTABLE
CONDITIONS DEVELOPING LATE THIS AFTERNOON SEVERE WEATHER MAY
ACCOMPANY THE STORMS...SO STORM SPOTTERS MAY NEED TO BE DEPLOYED. THE
PRIMARY SEVERE WEATHER THREAT IS DAMAGING WIND. LARGE HAIL IS ALSO
POSSIBLE. AFTER ABOUT 500 AM CDT MONDAY...THE THREAT DROPS
SIGNIFICANTLY.

NEZ004>010-022>029-035>038-056>059-069>071-094-111630-

HAZARDOUS WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
540 AM CDT SUN AUG 11 2002

...SEVERE THUNDERSTORMS ARE POSSIBLE TODAY IN WESTERN AND NORTH
CENTRAL NEBRASKA...

THERE IS A RISK OF SEVERE THUNDERSTORMS TODAY EAST OF A LINE FROM
VALENTINE TO IMPERIAL. A TROUGH AND FRONT IN NEBRASKA THIS AFTERNOON
AND EVENING WILL GENERATE THUNDERSTORMS. WITH EXTREMELY UNSTABLE
CONDITIONS DEVELOPING LATE THIS AFTERNOON SEVERE WEATHER MAY
ACCOMPANY THE STORMS...SO STORM SPOTTERS MAY NEED TO BE DEPLOYED. THE
PRIMARY SEVERE WEATHER THREAT IS DAMAGING WIND. LARGE HAIL IS ALSO
POSSIBLE. AFTER ABOUT 500 AM CDT MONDAY...THE THREAT DROPS
SIGNIFICANTLY.