Severe Thunderstorm Warning 50, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
329 PM CDT THU JUN 7 2001

MAIN CONCERN WILL BE PRECIP CHANCES TONIGHT AND TEMPERATURES ON
FRIDAY.

ALL MODELS INITIALIZED WELL THIS MORNING AT 500 MB WITH ONLY SLIGHT
DIFFERENCES NOTED IN 850 MB TEMPERATURES AND MOISTURE.  MORNING 850
MB ANALYSIS SHOWS MOISTURE RETURNING TO NEBRASKA PANHANDLE WHILE
CENTRAL AND EASTERN NEBRASKA REMAIN DRY.  CONVECTION FORMING ACROSS
THE PANHANDLE HAS BEEN WEAKENING INTO SHOWERS ONCE MOVING INTO DRIER
AIR AS WELL.  ETA APPEARS TO HAVE A GOOD HANDLE ON THIS MOISTURE
FIELD SO WILL LEAN TOWARDS IT FOR THIS PACKAGE.

TONIGHT...SURFACE HIGH WILL REMAIN ACROSS CENTRAL NEBRASKA WHICH
WILL CONTINUE TO PRODUCE A RETURN FLOW OF MOISTURE TO THE
PANHANDLE.   EXPECT WAVE COMING ACROSS CENTRAL ROCKIES TO HELP
INITIATE CONVECTION ACROSS EASTERN WYOMING AND THE FAR WESTERN
PANHANDLE IN AREA OF TOTAL TOTALS OF 50 TO 55 AND CAPE VALUES OF
1500-2000 J/KG.  THE BIG QUESTION THEN BECOMES THE EASTWARD EXTENT
OF PRECIPITATION.  WITH ETA STILL ADVERTISING DRY AIR ACROSS CENTRAL
AND EASTERN NEBRASKA UNDER HIGH PRESSURE...PRECIPITATION SHOULD HAVE
A HARD TIME MAKING IT INTO CENTRAL NEBRASKA.  HOWEVER...CURRENT
CONVECTION IS CONTINUING ACROSS THIS AREA DESPITE THE DRIER AIR AND
MORE STABLE 700-500 MB LAPSE RATES.  FOR THIS REASON WILL LEAVE A
SLIGHT CHANCE FOR SHOWERS ACROSS CENTRAL AND EASTERN ZONES FOR
TONIGHT.  ETA BOUNDARY LAYER RH DOES INDICATE SOME PATCHY FOG IN
SOUTHWEST ZONES AS WELL TONIGHT...SO WILL MENTION PATCHY FOG ACROSS
THIS AREA.

FRIDAY AND FRIDAY NIGHT...SURFACE HIGH THEN SHIFTS INTO MISSOURI
RIVER VALLEY AS UPPER RIDGE BUILDS ACROSS THE HIGH PLAINS.  500 MB
HEIGHTS WILL CLIMB TO NEAR THE 588 LINE ACROSS SOUTHWEST AREA WITH
850 MB TEMPERATURES RISING TO NEAR 25 DEGREES CELSIUS IN THE
PANHANDLE.  HIGHS IN THE 90S WEST AND 85 TO 90 EAST LOOK GOOD AT
THIS TIME.  WITH TEMPERATURES NEAR THE CONVECTIVE TEMP IN THE NORTH
CENTRAL AND NORTHWEST...EXPECT SOME SCATTERED CONVECTION TO DEVELOP
ACROSS THIS SAME AREA BY LATE AFTERNOON.  ETA DOES NOT INDICATE MUCH
IN THE WAY OF QPF OVER THIS TIME PERIOD...BUT WITH TOTAL TOTALS
AROUND 60 AND CAPE VALUES IN EXCESS OF 2000 J/KG WILL MENTION A
SLIGHT CHANCE FOR THUNDERSTORMS ACROSS CENTRAL AND NORTHERN ZONES
FRIDAY AFTERNOON INTO FRIDAY NIGHT.

SATURDAY AND SATURDAY NIGHT...UPPER RIDGE REMAINS ACROSS AREA FOR
THE FIRST HALF OF THE WEEKEND.  THIS ALONG WITH 850 MB TEMPERATURES
OF 28 DEGREES CELSIUS IN THE WEST AND 22 DEGREES CELSIUS IN THE EAST
SHOULD BRING A WARM SATURDAY.  TEMPERATURES PUSHING 90 OR ABOVE IS
NOT UNREASONABLE FOR SATURDAY UNDER A MOSTLY SUNNY SKY.  THE ONLY
CHANGE FROM THIS PATTERN LOOKS TO BE SOME SCATTERED CONVECTION
ACROSS THE WESTERN HALF OF CWA SATURDAY AFTERNOON INTO SATURDAY
NIGHT.  ATMOSPHERE LOOKS TO BE CAPPED FOR THE MOST PART AS 500 MB
VORT MAX MOVES ACROSS AREA...HOWEVER TEMPERATURES NEAR CONVECTIVE
TEMP SHOULD PRODUCE SOME ISOLATED TO SCATTERED CONVECTION IN THE
WEST.

IN THE EXTENDED...MEDIUM RANGE MODELS AGREE ON BUILDING UPPER RIDGE
ACROSS AREA ON SUNDAY AS UPPER TROUGH DIGS ACROSS THE PACIFIC
NORTHWEST.  TIMING DIFFERENCES THEN BEGIN TO SHOW UP FROM DAY 4
THROUGH THE END OF THE EXTENDED.  THE ECMWF...UKMET AND MRF ALL
SHIFT UPPER TROUGH ACROSS REGION BUT THE MRF IS AROUND 24 HOURS
FASTER THAN THE OTHER TWO MODELS.  MRF ENSEMBLE SPREADS DO INDICATE
SOME DISAGREEMENT ON PUSHING UPPER TROUGH ACROSS AREA AS QUICK AS
OPERATIONAL MRF INDICATES.  FOR THIS REASON WILL USE A SLIGHTLY
SLOWER MRF ALONG WITH ECMWF AND UKMET BLEND FOR THE EXTENDED.  WITH
WAVE AND FRONT NOT EXPECTED TO MOVE ACROSS AREA UNTIL TUESDAY...WILL
SUNDAY DRY WITH A CHANCE FOR PRECIP LATE MONDAY THROUGH EARLY
WEDNESDAY.  THURSDAY LOOKS TO BE A TRANSITION DAY SO WILL LEAVE IT
DRY AS WELL.  PRE-FRONTAL WARMING SHOULD KE4EP TEMPERATURES ABOVE
GUIDANCE VALUES ON MONDAY...BUT SHOULD FALL NEAR FMR VALUES THROUGH
THE REMAINDER OF THE EXTENDED.

.LBF...NONE.

AWJ