Severe Thunderstorm Warning 29, NWS North Platte, NE

AREA FORECAST DISCUSSION...CORRECTED TYPO IN 3RD PARAGRAPH
NATIONAL WEATHER SERVICE NORTH PLATTE NE
256 PM CDT MON MAY 18 1998

...FORECAST PROBLEM WILL BE TEMPERATURES...LOW CLOUDS AND THUNDERSTORM
CHANCES...

MODELS SIMILAR FORMING NEW 500 LOW AND WEST COAST TROUGH AND
MAINTAINING 500 RIDGE OVER CENTRAL U.S. WITH HINT OF WEAK SHORTWAVE
MOVING ACROSS NEBRASKA BY 00Z WEDNESDAY IN A WEAK VORT LOBE. THERE IS
ANOTHER HINT OF ANOTHER SHORTWAVE INTO EASTERN COLORADO AT END OF
FORECAST PERIOD. 850 FRONT GETS HUNG UP ON KS...NEB BORDER BY 36 HOURS
WHERE IT REMAINS THROUGH END OF FORECAST PERIOD AND THIS FRONT IS THE
KEY TO THE FORECAST.

18Z SFC ANALYSIS SHOWED A COLD FRONT EAST OF ABR TO EAST OF ONL TO HLC
WITH LEE SIDE TROUGH OUT AHEAD OF FRONT. AVN AND NGM SHOW LLJ COMING
INTO NEB TONIGHT AND TOMORROW NIGHT WHILE ETA DOES NOT SHOW THIS BUT
SHOWS MOISTURE BACKING IN FROM EAST INTO CWA. 850 DEWPOINTS INCREASE
TONIGHT AND TOMORROW IN LBF CWA WITH ETA BEING THE WETTEST MODEL WITH
MORE MOISTURE THAN NGM SHOWING 0 TO 8 DEGREE DEWPOINTS ACROSS CWA AT
00Z TONIGHT WHILE NGM SHOWS 3 TO 6 DEGREE DEWPOINTS WITH MOST MOISTURE
IN EASTERN CWA WHERE MOST UNSTABLE AIR REMAINS. ETAS TREND ON 850
DEWPOINTS CONTINUES ON 00Z TUESDAY WITH 6-16 DEW POINTS AT 00Z WHILE
NGM RANGES FROM 7-9. ETA CONTINUES TO BE THE MOST UNSTABLE MODEL AND
700-500 DELTA T ON BOTH MODELS GREATER THAN 20 THROUGH THE PERIOD WHILE
CWA REMAINS IN 700 THTE RIDGE AND 850 RIDGES BUILDS BACK INTO CWA
TOMMORROW. THERE IS SOME Q VECTOR CONVERGENCE TOMORROW WITH 250
DIVERGENCE...850 CONVERGENCE AND SFC MOISTURE FLUX CONVERGENCE AT 00Z
IN CWA AND THERE IS ALSO SOME GOOD UPSLOPE. THE BIG LIMITING FACTOR ON
THUNDERSTORM DEVELOPMENT WILL BE THE WARM 700 TEMPS WHERE ETA REMAINS
WARMER THAN THE NGM WITH COOLEST 700 TEMPS IN NORTH AND WARMEST IN THE
SOUTH. ETA PROGS 700 TEMPS OF 9-10 OVER ALL OF CWA TONIGHT AND 8-10
TOMOROW WHILE NGM IS COOLER WITH TEMPS IN THE 7-9 DEGREE RANGE. THIS
CAP WILL CONTINUE TO TRY TO SUPPRESS CONVECTION TONIGHT WITH BEST
CHANCE IN THE NORTH. ONE PROBLEM FOR TOMORROW WOULD BE THE UPSLOPE
COMBINED WITH THE 850 MOISTURE COMING BACK IN AND FEEL THAT STRATUS
WILL DEVELOP TONIGHT AND ADVECT IN FROM EAST AND THIS WOULD KEEP THE
MORNING CLOUDY ACROSS THE CWA AND THIS COULD AFFECT THE STABILITY
TOMORROW DEPENDING ON HOW LONG THE STUFF TAKES TO BURN OFF. THIS
STRATUS WILL BE FACTORED IN FOR TEMPERATURES AND WILL GO BETWEEN WARM
FAN GUIDANCE AND COOLER FWC GUIDANCE.

GOING FORECAST LOOKS GOOD BUT RECOMMEND BECOMING CLOUD LATE FOR LOW
CLOUDS AND STRATUS TO OVERSPREAD AREA AND THEN RECOMMEND HAVING MORNING
MENTION IN 2ND PERIOD FOR LOW CLOUDS BURNING OFF BY LATE MORNING.

PRELIMINARY GUIDANCE FOR COORDINATION ONLY.  OFFICIAL FORECASTS ARE
CONTAINED WITHIN PRODUCT OMAZFPNE.

CCF
LBF EE 053/081 054/082 054 701233  ANW BB 054/081 055/080 055 702243
OGA EE 052/082 054/082 054 701233  ONL BB 057/080 058/081 057 702243
IML EE 053/083 055/084 055 701233  BBW EE 055/081 056/082 055 701233
VTN BB 051/081 054/080 054 702233

MICHELS