Severe Thunderstorm Warning 194, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
325 AM CDT MON JUL 6 1998

...THE MAIN CHALLENGE WITH THIS MORNINGS FORECAST IS THE LOCATION,
EXTENT, AND STRENGTH OF CONVECTION WITH THE NEXT SHORT WAVE TROUGH. THE
TIMING APPEARS TO BE FAIRLY CLEAR-CUT...

MODEL PERFORMANCE DISCUSSION...
    THE 05/00Z ETA/NGM MODEL RUN WAS A LITTLE SLOW WITH THE VORT MAXES
IN MINNESOTA AND THE ONE IN NORTHERN UTAH (WHICH IS THE NEXT ONE TO
AFFECT NEBRASKA). THE 05/12Z RUN ADJUSTMENT CAME A LITTLE CLOSER, BUT
STILL WAS A LITTLE SLOW WITH IT. HOWEVER, THE ETA AND NGM DID BETTER
WITH THIS FEATURE THAN THE AVN (WHICH DIDNT HAVE IT INDICATED AT ALL)
IN ADDITION, THE ETA AND NGM SOLUTIONS ARE SIMILAR WITH THE VORTICITY
AND HEIGHT FIELDS AT 500 MB OUT TO 36 HOURS. BY 48 HOURS THOUGH, THE
DIFFERENCES BECOME VERY STRONG. AT THAT TIME, THE ETA HAS A VORT MAX
MOVING INTO WESTERN KANSAS WHILE THE NGM HAS IT IN SOUTHEAST NEW
MEXICO. BOTH MODELS ARE KIND OF ERRATIC BETWEEN CYCLES WITH THEIR 48
HOUR FORECASTS. AS A RESULT, IT IS DIFFICULT TO EVALUATE THEIR
PERFORMANCE WITH END PERIOD FORECASTS. IT SEEMS THAT THE ETA HAS DONE
BETTER THAN THE NGM OVERALL FOR THE PAST FEW DAYS. ALSO, THE 48H
FORECAST FROM THE 05/00Z RUN IS COMPARABLE TO THE 24H FORECAST FROM
LAST NIGHTS RUN IN THE LOCATION OF THE AXIS OF HIGHER VORTICITY. SO,
HAVE SELECTED THE ETA FOR THIS MORNINGS FORECAST CYCLE.

FIRST AND SECOND PERIOD DISCUSSION...
    THE POSITION OF THE 850MB THETA-E RIDGE AND 850-500MB INSTABILITY
THIS AFTERNOON INDICATES THAT THUNDERSTORMS ARE MOST LIKELY ALONG AND
EAST OF AN ANW-BBW LINE. BY 00Z...THE THETA-E RIDGE AND INSTABILITY
ARE EXPECTED OUT OF THE NORTH PLATTE UPDATE AREA. ALTHOUGH SIGNIFICANT
UPWARD VERTICAL VELOCITY IN THE 700-500MB LAYER IS INDICATED IN MUCH OF
CENTRAL AND WESTERN NEBRASKA, INCLUDING THE PANHANDLE, THE POSITION OF
THE THETA-E RIDGE AND AXIS OF MAXIMUM INSTABILITY WOULD SEEM TO
PRECLUDE SIGNIFICANT PRECIPITATION IN THE WEST IF THUNDERSTORMS DO
DEVELOP. AS A RESULT, SEE NO REASON TO CHANGE PRESENT FIRST AND SECOND
PERIOD FORECASTS IN THE WEST. HOWEVER, I WOULD SUGGEST GOING WITH
THUNDERSTORMS LIKELY THIS AFTERNOON AND EVENING IN THE CENTRAL AND
NORTH CENTRAL ZONES.
    LOOKING AT THE 1000-500MB THICKNESS AND 850MB TEMPERATURES, SLIGHT
WARM ADVECTION IS INDICATED. WITH THAT IN MIND, TEMPERATURES SLIGHTLY
WARMER THAN YESTERDAYS LOOK GOOD AS CURRENT FORECAST ALLOWS.

THIRD PERIOD...
    BY 18Z TUESDAY...THE 850MB THETA-E RIDGE WILL SHIFT BACK INTO
WESTERN NEBRASKA ALONG A VTN-OGA LINE, SO AFTERNOON THUNDERSTORMS MAY
DEVELOP IN THE WESTERN HALF OF THE NORTH PLATTE UPDATE AREA. IN THE
EASTERN HALF, HOWEVER, THEY WILL PROBABLY NOT MOVE IN UNTIL TUESDAY
NIGHT.
    SLIGHTLY COOLER TEMPERATURES ARE INDICATED FOR TUESDAY BY THE
THICKNESS AND 850MB TEMPERATURES. ADD IN A LITTLE MORE CLOUDINESS IN
THE WEST, AND GOING DOWN A FULL CATEGORY SEEMS APPROPRIATE AS THE
PRESENT FORECAST INDICATES.

SUGGESTED CCF

PRELIMINARY GUIDANCE FOR COORDINATION ONLY. OFFICIAL FORECAST IS
CONTAINED WITHIN THE PRODUCT OMAZFPNE.

LBF BB 093/064 088/063 088 49223
VTN BB 091/065 087/064 087 49223

OGA BB 093/065 088/064 088 49223
IML BB 095/067 090/066 090 49223
BBW BU 088/067 088/066 086 49660
ANW BU 088/068 088/067 085 49660
ONL BB 087/068 088/067 084 49660

SPRINGER

NEZ004>010-022>029-035>038-056>059-069>071-071200-

SEVERE WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1050 AM CDT (950 AM MDT) MON JUL 6 1998

THIS OUTLOOK PERTAINS TO THE FOLLOWING NEBRASKA COUNTIES...

ARTHUR     BLAINE     BOYD       BROWN      CHASE      CHERRY
CUSTER     DEUEL      FRONTIER   GARDEN     GARFIELD   GRANT
HAYES      HOLT       HOOKER     KEITH      KEYA PAHA  LINCOLN
LOGAN      LOUP       MCPHERSON  PERKINS    ROCK       SHERIDAN
THOMAS     WHEELER

...STORM SPOTTER ACTIVATION MAY BE REQUIRED ACROSS PARTS OF NORTH
CENTRAL NEBRASKA LATE THIS AFTERNOON INTO TONIGHT...

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS NORTH OF A LINE FROM
AINSWORTH TO ONEILL BY TONIGHT...WITH A SLIGHT RISK NORTH OF A LINE
FROM MERRIMAN TO BROKEN BOW. ISOLATED TO WIDELY SCATTERED THUNDERSTORMS
ARE POSSIBLE ELSEWHERE ACROSS THE OUTLOOK AREA BUT ARE EXPECTED TO
REMAIN BELOW SEVERE LIMITS.

A STATIONARY FRONT LOCATED NEAR THE SOUTH DAKOTA AND NEBRASKA BORDER
WILL REMAIN IN NEARLY THE SAME PLACE THROUGH THE EVENING. ACROSS NORTH
CENTRAL NEBRASKA...LOW LEVEL MOISTURE WILL BE PLENTIFUL AND WITH THE
HELP OF DAYTIME HEATING...WILL ALLOW THE ATMOSPHERE TO BECOME QUITE
UNSTABLE BY LATE AFTERNOON. AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS
THE AREA LATE THIS AFTERNOON INTO THIS EVENING...SCATTERED
THUNDERSTORMS ARE EXPECTED TO DEVELOP AND MAY BECOME SEVERE QUICKLY
NORTH OF A LINE FROM MERRIMAN TO BROKEN BOW...AND ESPECIALLY NORTH OF A
LINE FROM AINSWORTH TO ONEILL. THE MAIN SEVERE WEATHER THREAT WILL BE
LARGE HAIL AND DAMAGING WINDS AND VERY HEAVY RAIN WILL BE POSSIBLE AS
WELL.

WARM TEMPERATURES IN THE MID LEVELS OF THE ATMOSPHERE ARE EXPECTED TO
LIMIT THUNDERSTORMS ACTIVITY FURTHER SOUTH INTO SOUTHWEST
NEBRASKA...AND ANY THUNDERSTORMS THAT DO DEVELOP ARE EXPECTED TO REMAIN
BELOW SEVERE LIMITS.

STOPPKOTTE

NEZ004>010-022>029-035>038-056>059-069>071-071200-

SEVERE WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE...CORRECTED FOR TYPO
1050 AM CDT (950 AM MDT) MON JUL 6 1998

THIS OUTLOOK PERTAINS TO THE FOLLOWING NEBRASKA COUNTIES...

ARTHUR     BLAINE     BOYD       BROWN      CHASE      CHERRY
CUSTER     DEUEL      FRONTIER   GARDEN     GARFIELD   GRANT
HAYES      HOLT       HOOKER     KEITH      KEYA PAHA  LINCOLN
LOGAN      LOUP       MCPHERSON  PERKINS    ROCK       SHERIDAN
THOMAS     WHEELER

...STORM SPOTTER ACTIVATION MAY BE REQUIRED ACROSS PARTS OF NORTH
CENTRAL NEBRASKA LATE THIS AFTERNOON INTO TONIGHT...

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS NORTH OF A LINE FROM
AINSWORTH TO ONEILL BY TONIGHT...WITH A SLIGHT RISK NORTH OF A LINE
FROM MERRIMAN TO BROKEN BOW. ISOLATED TO WIDELY SCATTERED THUNDERSTORMS
ARE POSSIBLE ELSEWHERE ACROSS THE OUTLOOK AREA BUT ARE EXPECTED TO
REMAIN BELOW SEVERE LIMITS.

A STATIONARY FRONT LOCATED NEAR THE SOUTH DAKOTA AND NEBRASKA BORDER
WILL REMAIN IN NEARLY THE SAME PLACE THROUGH THE EVENING. ACROSS NORTH
CENTRAL NEBRASKA...LOW LEVEL MOISTURE WILL BE PLENTIFUL AND WITH THE
HELP OF DAYTIME HEATING...WILL ALLOW THE ATMOSPHERE TO BECOME QUITE
UNSTABLE BY LATE AFTERNOON. AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS
THE AREA LATE THIS AFTERNOON INTO THIS EVENING...SCATTERED
THUNDERSTORMS ARE EXPECTED TO DEVELOP AND MAY BECOME SEVERE QUICKLY
NORTH OF A LINE FROM MERRIMAN TO BROKEN BOW...AND ESPECIALLY NORTH OF A
LINE FROM AINSWORTH TO ONEILL. THE MAIN SEVERE WEATHER THREAT WILL BE
LARGE HAIL AND DAMAGING WINDS AND VERY HEAVY RAIN WILL BE POSSIBLE AS
WELL.

WARM TEMPERATURES IN THE MID LEVELS OF THE ATMOSPHERE ARE EXPECTED TO
LIMIT THUNDERSTORM ACTIVITY FURTHER SOUTH INTO SOUTHWEST
NEBRASKA...AND ANY THUNDERSTORMS THAT DO DEVELOP ARE EXPECTED TO REMAIN
BELOW SEVERE LIMITS.

STOPPKOTTE