Severe Thunderstorm Warning 35, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
324 AM CDT THU MAY 31 2001

...MAIN FORECAST CONCERN IS PRECIPITATION CHANCES TODAY AND THEN
LEVEL OF WIND ON FRIDAY...

ALL MODELS APPEAR TO HAVE INITIALIZED WELL THIS PAST EVENING IN THE
MID AND LOW-LEVELS.  LATEST WATER VAPOR IMAGERY ALONG WITH HEIGHT
TENDENCIES AT 500 MB INDICATE A CONTINUED SLOW NORTHEAST MOVEMENT OF
UPPER LOW.  THE MODELS REFLECT A SIMILAR TREND OVER THE NEXT 24
HOURS...WITH ONLY SLIGHT VARIATIONS NOTED.  FOR THIS REASON
WILL USE A BLEND OF MODELS FOR THIS FORECAST PACKAGE.

TODAY...UPPER LOW PRESSURE WILL CONTINUE TO DRIFT EAST TODAY
ALLOWING NORTHEAST CORNER OF CWA TO FINALLY DRY OUT.  ONLY HITCH FOR
THIS MORNING IS LINGERING LOW CLOUDS AND FOG.  ETA RH FIELDS
INDICATE GRADUAL CLEARING FROM WEST TO EAST AS SURFACE TROUGH MOVES
ACROSS AREA.  UPPER JET MAX ACROSS SOUTHWEST CANADA THEN SHIFTS INTO
EASTERN MONTANA AND THE WESTERN DAKOTAS DURING THE AFTERNOON AS
SURFACE TROUGH CONTINUES TO MOVE ACROSS CWA.  THIS LEAVES A LARGE
PORTION OF CWA UNDER LEFT EXIT REGION OF UPPER JET WITH SOME
MODERATE LIFT NOTED IN THE 700-500 MB LAYER.  BELIEVE ETA IS A
LITTLE TO HIGH ON SURFACE DEWPOINTS AHEAD OF TROUGH BUT UPPER 40 TO
LOWER 50 DEGREE DEWPOINTS ARE STILL POSSIBLE.  MID LEVEL LAPSE RATES
OF 6 TO 6.5 DEGREES CELSIUS SHOULD KEEP THE INSTABILITY ON THE
WEAKER SIDE WITH MAINLY A FEW SHOWERS EXPECTED. HOWEVER...WITH THE
0-6 KM SHEAR SLIGHTLY UNDER 50 KNOTS I CANNOT RULE OUT JUST ENOUGH
CELL ORGANIZATION FOR ONE OR TWO THUNDERSTORMS AS WELL.
TEMPERATURES NEAR GUIDANCE VALUES LOOK GOOD.

TONIGHT...SURFACE TROUGH REMAINS ACROSS EXTREME EASTERN CWA DURING
THE EVENING BEFORE SHIFTING EAST OF AREA BY MIDNIGHT.  THIS WILL
KEEP A SLIGHT CHANCE FOR EARLY EVENING SHOWERS OR THUNDERSTORMS
ACROSS EASTERN THIRD OF CWA.  OTHERWISE...AREA MOVES INTO SUBSIDENT
REGION OF JET WITH PARTLY CLOUDY TO MOSTLY CLEAR SKIES EXPECTED.
GUIDANCE LOW TEMPERATURES LOOK GOOD EXCEPT FOR NORTHEAST CWA WHERE
TEMPERATURES SHOULD BE AROUND A CATEGORY COLDER THAN SHOWN.

FRIDAY AND FRIDAY NIGHT...COLD FRONT MOVES OUT OF THE DAKOTAS AND
ACROSS CWA BY 18Z.  BEHIND THE FRONT LOW-LEVEL LAPSE RATES OF 8.5 TO
9 DEGREES CELSIUS ALONG WITH SOME DOWNWARD OMEGA NOTED IN THE
850-700 MB LAYER WILL MIX DOWN STRONGER WINDS.  IT LOOKS AS THOUGH
ALL BUT FAR SOUTHWEST CORNER OF CWA WILL MEET BREEZY CONDITIONS AND
NORTHEAST CORNER INTO THE WINDY CATEGORY.  WITH SUBSIDENCE
CONTINUING INTO FRIDAY NIGHT AND SURFACE HIGH PRESSURE BRINGING
LIGHT WINDS...BELIEVE TEMPERATURES WILL FALL AROUND A CATEGORY LOWER
THAN FWC GUIDANCE IS INDICATING BUT NEAR MAV GUIDANCE NUMBERS.

IN THE EXTENDED...LATEST MRF/AVN IS CONTINUING TO SHOW RIDGING
ACROSS AREA FOR THE FIRST HALF OF WEEKEND.  THEN MRF/AVN CHANGES
ABRUPTLY FROM PREVIOUS RUN BY FORMING A STRONG UPPER LOW ACROSS
NORTHERN PLAINS ON MONDAY INTO TUESDAY.  THIS SEEMS A LITTLE HARD TO
BELIEVE SINCE THE MODEL BREAKS THE UPPER RIDGE DOWN WITHIN 12
HOURS.  WILL NOT MAKE ANY CHANGES TO EXTENDED AT THIS TIME AND WILL
LET DAY CREW SEE HOW 12Z AVN INVOLVES THIS SYSTEM BEFORE CHANGING
CURRENT FORECAST.

.LBF...NONE.

AWJ

NEZ004>010-022>029-035>038-056>059-069>071-312045-

SEVERE WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1122 AM CDT THU MAY 31 2001

...STORM SPOTTER ACTIVATION IS NOT ANTICIPATED...

THERE IS A SLIGHT CHANCE OF SHOWERS...AND A FEW ISOLATED
THUNDERSTORMS...THIS AFTERNOON AND EVENING OVER PORTIONS OF WESTERN
AND NORTH CENTRAL NEBRASKA. THESE THUNDERSTORMS ARE NOT EXPECTED TO
REACH SEVERE LEVELS.

A WEAK COLD FRONT WILL MOVE SOUTHEAST THROUGH WESTERN AND NORTH
CENTRAL NEBRASKA THIS AFTERNOON INTO EARLY THIS EVENING. SHOWERS AND
A FEW ISOLATED THUNDERSTORMS MAY DEVELOP ALONG THE FRONT. HOWEVER...
ANY THUNDERSTORMS THAT DO FORM ARE NOT EXPECTED TO BECOME SEVERE
SINCE THE ATMOSPHERE WILL REMAIN MODERATELY STABLE.

DDB