Severe Thunderstorm Warning 315, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
255 PM CDT SAT SEP 4 2004

...FORECAST CHALLENGES ARE PRECIP CHANCES THIS WEEKEND...THEN MID
WEEK FRONTAL PASSAGE AND ASSOCIATED PRECIP CHANCES AND TEMPS...

.DISCUSSION...
.NEAR TERM (TONIGHT THROUGH TUESDAY)...MAIN FORECAST CHALLENGE LIES
WITH THE TIMING OF THE ONSET OF PRECIPITATION...THEN TIMING OF THE
EXITING TROF AND END OF PRECIPITATION ON SUNDAY AFTERNOON. SO
FAR...ONGOING GRIDS LOOK IN GOOD SHAPE WITH RESPECT TO WEATHER OVER
THE NEXT 36 HOURS. AM PLANNING ON INCREASING POPS INTO THE HIGH
LIKELY CATEGORY AFTER 03Z THIS EVENING. SURFACE LOW OVR SWRN NEBR
WILL CREEP EWD OVERNIGHT. BOTH THE ETA AND GFS ARE INDICATING A
STRONG DEFORMATION FIELD TO THE NORTH AND WEST OF THE LOW WITH
STRONG MID LEVEL FRONTOGENESIS ORIENTED FROM THE PANHANDLE TO KONL
OVERNIGHT. WITH PWS WELL OVER AN INCH THROUGHOUT THE EVENT AND WITH
THE TROF APPEARING TO LINK UP WITH THE TROPICAL SYSTEM OFF THE BAJA
CA COAST AS WE SPEAK...ENOUGH LOW LEVEL MOISTURE EXISTS FOR A FAIRLY
SUSTAINABLE RAIN EVENT OVERNIGHT. ADDED SUPPORT WILL COME INTO THE
PICTURE OVERNIGHT AS A DECENT JET STREAK ARRIVES. PRECIP WILL
CONTINUE INTO MOST OF TOMORROW AS THE FA REMAINS UNDERNEATH OR AHEAD
OF THE TROF FOR THE BETTER PART OF SUNDAY. WITH PERSISTENT
CLOUDINESS AND PRECIPITATION EXPECTED...TEMPS WERE NOSED DOWN FURTHER
INTO THE 60S. AFTER SUNDAY...FAIR CONDS WILL RETURN ON MONDAY AND
TUESDAY AS PATTERN TRANSITIONS TO ZONAL ONCE AGAIN...ALLOWING TEMPS
TO REBOUND INTO THE 70S AND LWR 80S.
.LONG TERM (WEDNESDAY THROUGH SATURDAY)...NO SURPRISE AS THE GFS
SOLUTION LAST NIGHT (00Z) AND 06Z RUN OF THE GFS EARLIER THIS AM...
SLOW THE ACTION DOWN NEXT WEEK. WITH THE LATEST RUN...THE FRONT WILL
BE KNOCKING ON OUR DOOR THURSDAY NIGHT. AS FOR PRECIP...CONDS SHOULD
REMAIN FAIRLY DRY INTO THURSDAY...WITH A SLIGHT CHANCE OF PRECIP
MENTIONED ON THURSDAY NIGHT...FRIDAY AND EARLY SATURDAY ASSOC WITH
THE FROPA. AS FOR TEMPS...HIGHS WILL BE MAINLY IN THE UPPR 70S/LWR
80S...FOR WEDS AND THURSDAY...WITH THEM COOLING BACK INTO THE LWR TO
MID 70S FOR FRIDAY AND SATURDAY. FOR DAYS 8 THROUGH 10...THE GFS
CONTINUES TO HINT AT A FAIRLY SIGNIFICANT FRONT ON SUNDAY AND
MONDAY.

.SYNOPSIS...H5 ANALYSIS THIS AM HIGHLIGHTED WITH A DEEP TROF IN THE
WEST AND STRONG RIDGING IN THE EASTERN CONUS. CLOSED LOW HAS
DEVELOPED IN EXTREME SWRN UT AND WV IMAGERY FROM 18Z POSITIONS THE
UPPR LOW OVR SOUTH CENTRAL UT. THIS POSN IS IN FAIRLY GOOD AGREEMENT
WITH THE 12Z GFS AND ETA RUNS. AT THE SURFACE...ANALYSIS AS OF 19Z
HAS THE FRONT ALIGNED FROM LBF TO NEAR AINSWORTH. UNDER A DENSE
CANOPY OF CLOUDS...TEMPERATURES HAVE STRUGGLED TO REACH 60 OVER THE
FAR NWRN ZONES THIS AFTERNOON. IN CONTRAST...ONEIL WAS 88 AND
MCCOOK WAS 91 AS OF 2 PM CDT. FIRST INITIAL SHORTWAVE ARRIVING ATTM
OVER E CENTRAL COLORADO AND NW KS AS TSRAS HAVE BEGUN TO SPROUT
SOUTH OF GLD.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...NONE.

&&

CLB

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
340 PM CDT SAT SEP 4 2004

NEZ004>010-022>029-035>038-056>059-069>071-094-051030-
ARTHUR NE-BLAINE NE-BOYD NE-BROWN NE-CHASE NE-CUSTER NE-DEUEL NE-
EASTERN CHERRY NE-FRONTIER NE-GARDEN NE-GARFIELD NE-GRANT NE-
HAYES NE-HOLT NE-HOOKER NE-KEITH NE-KEYA PAHA NE-LINCOLN NE-LOGAN NE-
LOUP NE-MCPHERSON NE-PERKINS NE-ROCK NE-SHERIDAN NE-THOMAS NE-
WESTERN CHERRY NE-WHEELER NE-
INCLUDING THE CITIES OF...AINSWORTH...ARNOLD...ARTHUR...BASSETT...
BIG SPRINGS...BREWSTER...BROKEN BOW...BURWELL...CHAPPELL...CURTIS...
GORDON...GRANT...HAY SPRINGS...HAYES CENTER...IMPERIAL...MULLEN...
NORTH PLATTE...ONEILL...OGALLALA...OSHKOSH...RUSHVILLE...SPENCER...
SPRINGVIEW...STAPLETON...TAYLOR...THEDFORD...TRYON AND VALENTINE
340 PM CDT SAT SEP 4 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND NORTH CENTRAL
NEBRASKA.

.DAY ONE...TONIGHT

A VIGOROUS COLD FRONT SLIDING SLOWLY SOUTHEAST THROUGH WESTERN
NEBRASKA WILL BE THE FOCUS FOR SHOWER AND THUNDERSTORM DEVELOPMENT.
SHOWERS WILL BECOME MORE WIDESPREAD OVERNIGHT AS THE UPPER LEVEL LOW
PRESSURE MOVES ACROSS THE AREA. A FEW THUNDERSTORMS ARE POSSIBLE IN
THE MORE UNSTABLE AIR...MAINLY EAST OF A LINE FROM ONEILL TO NORTH
PLATTE TO IMPERIAL...WITH SMALL HAIL AND GUSTY WINDS POSSIBLE. THE
STORMS ARE EXPECTED TO REMAIN BELOW SEVERE CRITERIA.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE SURFACE FRONT WILL BEGIN TO ADVANCE EASTWARD ON SUNDAY AS THE
UPPER LEVEL TROUGH ADVANCES THROUGH WESTERN NEBRASKA. WHILE SHOWERS
AND THUNDERSTORMS ARE LIKELY IN EASTERN PORTIONS OF THE OUTLOOK
AREA...DRIER AIR BEHIND THE SYSTEM SHOULD BRING AN END TO
PRECIPITATION IN THE NORTHWEST DURING THE AFTERNOON.

IT APPEARS THE FIRST SIGNS OF AUTUMN WILL ARRIVE BY FRIDAY BEHIND A
STRONG COLD FRONT SWEEPING THROUGH THE OUTLOOK AREA AS EARLY AS
THURSDAY. ALTHOUGH IT IS TOO EARLY TO TELL HOW COLD THIS AIRMASS WILL
BE...THERE WILL BE THE POTENTIAL FOR MORNING LOW TEMPERATURES TO DIP
INTO THE 30S ACROSS PORTIONS OF WESTERN AND NORTH CENTRAL NEBRASKA
ON FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

DDB