Severe Thunderstorm Warning 107, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
153 AM CDT SAT JUN 30 2001

...CHC OF THUNDERSTORMS AND TEMPS ARE CHALLENGES THRU PERIOD...

PERSISTENT UPPER LEVEL PATTERN WITH RIDGE OVER DESERT SOUTHWEST...
LOW OVER HUDSON/S BAY. UPPER LEVEL TROUGH OVER SOUTHEAST STATES
CONTINUES TO RETROGRADE...AND IS FORECAST TO WEAKEN AND HEAD SOUTH
BY MONDAY.  AT THE SURFACE...SOME RELIEF FROM HEAT MAY BE ON THE WAY
FOR MISSOURI RIVER VALLEY SUNDAY AS CANADA HIGH SLIDES SOUTH.

TEMPS HAVE BEEN 5 DEGREES ABOVE GUIDANCE FORECASTS ALL THIS PAST
WEEK...AND SEE NO REASON WHY SATURDAY WOULD BE DIFFERENT.  WARM
FRONT TO SET UP SOMEWHERE ALONG THE NEB-SD BORDER BY 18Z SAT...
SINKING SOUTH WITH LOW PRESSURE CENTER BY 06Z TOWARD GLD AS CANADA
HIGH BEGINS TO ENTER AREA. SMALL VORT MAXES TRAVERSING CWA FROM
NORTHWEST TO SOUTHEAST DURING THE DAY MAY KICK OFF BRIEF ROUNDS OF
SHOWERS AND STORMS...BUT NOT UNTIL 00Z SUNDAY DOES THE MAIN VORT MAX
ENTER CWA IN NORTH CENTRAL NEBRASKA...PLUNGING SOUTH. SATURDAY
EVENING LOOKS TO BE ACTIVE ACROSS MOST OF CWA.   MAIN THREAT FOR SVR
WOULD LIKE BE ACROSS EASTERN HALF OF CWA...BUT DUE TO UNCERTAINTY OF
MODEL TRACK THE CURRENT SWODY1 LOOKS OK. SWODY1 MENTIONS ADEQUATE
DIRECTIONAL SHEAR TO SUPPORT ROTATION AND LARGE HAIL.  SHOWERY
ACTIVITY PRIOR TO MAIN ONSET OF CONVECTION WILL LAY OUT BOUNDARIES
ACROSS CWA. NOT CLEAR IF UPPER LEVEL TROUGH SWINGING THROUGH CANADA
NORTH OF MN WILL ADD ENERGY TO OUR AREA DURING THE EVENING...BUT IT
WILL AT LEAST HELP PUSH CONVECTION SOUTH.

SUNDAY...STRONG BAROCLINIC ZONE TO SET UP AS SURFACE HIGH PRESSURE
FROM CANADA SINKS SOUTHEAST TOWARD WISCONSIN.  TEMP GRAD
ACROSS CWA WILL BE RATHER STEEP...RANGING FROM NEAR 90 IN SOUTHWEST
CWA TO 60 IN ONL AREA. SOUTHEAST SURFACE WINDS WILL POOL MOISTURE
AND DEWPOINTS IN THE 50S OVER MUCH OF CWA SUNDAY MORNING...AND AVN
HAS DEWPOINTS PROGGED TO REACH MID 60S BY SUNDAY AFTERNOON. ANOTHER
VORT MAX ENTERING NORTHWEST PORTION OF CWA 00Z MONDAY WILL MOVE
SOUTHEAST ACROSS CWA PER AVN...MAKING FOR MORE CHANCES OF SCT
SHRA/TSRA ACTIVITY SUNDAY EVENING. AVN FASTER BY ABOUT 6 HOURS WITH
THIS FEATURE THAN ETA. BOTH MODELS SIMILAR WITH TIMING OF SECOND
MAJOR VORT MAX TO ENTER NORTH CENTRAL NEB NR VTN BY 12Z MONDAY.
TEMPS SHOULD BE CLOSER TO GUIDANCE VALUES MONDAY ACROSS CWA AS IT
APPEARS THERE WILL BE SOME CLOUDS ALL DAY AS WELL.

EXTENDED...TUESDAY LOOKS LIKE IT MAY BE DRY...BUT AS WESTERN RIDGE
AMPLIFIES...RIDGE RUNNERS OVER AREA IN NORTHWEST FLOW CONTINUE TO
BE PROBLEMATIC.  MRF QPF FIELDS VERY NOISY. SFC HI TO PUSH IN
THURSDAY. WILL NOT CHANGE CURRENT EXTENDED UNLESS NEW MRF SHOWS BIG
CHANGES.

.LBF...NONE.

SLM

NEZ004>010-022>029-035>038-056>059-069>071-302045-

SEVERE WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1111 AM CDT SAT JUN 30 2001

...STORM SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND
TONIGHT...

THERE IS A CHANCE FOR THUNDERSTORM DEVELOPMENT ACROSS ALL OF
WESTERN AND NORTH CENTRAL NEBRASKA THROUGH TONIGHT. SOME OF THE
THUNDERSTORMS MAY REACH SEVERE LIMITS...WITH LARGE HAIL...DAMAGING
WINDS AND ISOLATED TORNADOES POSSIBLE.

A SEMI STATIONARY FRONT WILL MOVE SLOWLY SOUTH ACROSS THE STATE
TODAY...AS HIGH PRESSURE BUILDS IN FROM THE NORTH. THE CONVERGENT
WIND FLOW BETWEEN THESE SYSTEMS WILL PRODUCE UPSLOPE FLOW ACROSS THE
NORTHWEST THIS AFTERNOON. ONGOING THUNDERSTORMS WILL ENTER NORTH
CENTRAL NEBRASKA EARLY THIS AFTERNOON FROM THE NORTH...AND AS THEY
PROGRESS INTO AN INCREASINGLY UNSTABLE ATMOSPHERE...SEVERE
THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE. ADDITIONAL THUNDERSTORM
DEVELOPMENT WILL BE POSSIBLE ACROSS NORTHWEST PORTION OF THE OUTLOOK
AREA LATE THIS AFTERNOON...MAINLY WEST OF A LINE FROM VALENTINE...TO
MULLEN AND LISCO LINE. THE STORMS ARE EXPECTED TO MOVE TO THE SOUTH
AND EAST...ADVANCING THROUGH THE REMAINDER OF THE OUTLOOK AREA
TONIGHT.

THE THUNDERSTORMS WILL BE CAPABLE OF PRODUCING VERY HEAVY RAIN...
WITH THE PRIMARY SEVERE WEATHER THREAT TO BE LARGE HAIL.

DP