Severe Thunderstorm Warning 126, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
300 PM CDT SAT JUL 12 1997

MAIN FORECAST PROBLEM THIS AFTERNOON AND TONIGHT IS THE CHANCES OF
THUNDERSTORMS AND THE POTENTIAL FOR SEVERE WEATHER...

ETA/NGM/AVN ARE SIMILAR IN HANDLING THE VORT MAX COMING OUT OF SW
IDAHO WITH NGM SHOWING POSITION SHIFT TO THE SOUTHEAST OF AVN/ETA
POSITION BY 36 HOURS WHEN IT MOVES INTO THE CENTRAL DAKOTAS. AT THAT
TIME...AVN/ETA HAVE CENTER OF THE VORTEX ALONG THE SD/ND BORDER WITH
LOBE OF HIGHER REL VORT THRU NEB ALONG ANW-LBF LINE. BY 48 HOURS...THE
VORTEX WILL BE CENTERED IN NORTHERN MINNESOTA WITH LOBE AXIS THROUGH
FSD-OFK-SLN. SO...IT SEEMS THAT AT LEAST SOME PART OF THE NORTH PLATTE
UPDATE AREA WILL BE UNDER THE THREAT OF THUNDERSTORMS THROUGH SUNDAY
AND INTO SUNDAY EVENING. AT 800MB...340K PLUS THETA-E RIDGE IS FORECAST
BY ETA THIS AFTERNOON TO BE IN EASTERN WYOMING. THIS IS SUPPORTED BY
ADAP SFC MOISTURE CONVERGENCE AT 18Z. SO THAT IS PROBABLY THE AREA OF
INITIAL CONVECTIVE DEVELOPMENT FOR THIS EVENING. THEN...THE AXIS OF
HIGH THETA-E SHIFTS INTO THE EASTERN PART OF THE LBF WARNING AREA BY
12Z SUNDAY. UNDER THESE CIRCUMSTANCES...SOME MENTION OF PRECIP IS
APPROPRIATE THROUGH SUNDAY IN THE NORTHEAST PART OF THE WARNING AREA...
BUT COULD PROBABLY DROP MENTION OR USE A POP OF 20 PERCENT OR LESS IN
THE SOUTHWEST FOR SUNDAY. THE STRONGEST CHANCES APPEAR TO BE TONIGHT
BEFORE MIDNIGHT WEST OF ANW-BBW AND BETWEEN MIDNIGHT AND 7 AM CDT EAST
OF THAT LINE. LOOKS LIKE MCS DEVELOPMENT IS MOST LIKELY IN AREA BOUNDED
BY CYS-IML-AKO WITH POSSIBLE BACK-BUILDING IN SOUTHEAST WYOMING AND
NORTHEAST COLORADO WHERE DIFFLUENT THICKNESS IS PROGGED BY AVN/ETA.
ALSO...THE STRONGEST QG FORCING IN THE 850-500MB LAYER IS PROGGED BY
THE ETA TO BE IN WESTERN SOUTH DAKOTA AND NORTHWEST NEBRASKA. SO...
HIGHEST CHANCES OF STRONG THUNDERSTORMS TONIGHT IS IN THE NORTH AND IN
THE NORTHWEST PART OF THE STATE. HIGHEST CAPE IS EXPECTED IN EASTERN
NEBRASKA TONIGHT...SO CONVECTIVE SYSTEM IS LIKELY TO BUILD ITS POWER AS
IT MOVES INTO CENTRAL AND NORTH CENTRAL NEBRASKA WHERE CAPES OF 2000
J/KG OR HIGHER BEGIN (NORTH AND EAST OF A MCK-AIA LINE). LOWEST LI'S
ARE ALSO EXPECTED IN THAT AREA. SUGGEST A POP OF 40 PERCENT TONIGHT
SOUTH OF BBW-SNY LINE AND 50 TO 60 PERCENT NORTH OF THAT LINE.

THE NEXT QUESTION IS TEMPERATURES. THE AVN/ETA 1000-500MB THICKNESS
PATTERN SHOWS LITTLE CHANGE BETWEEN THIS MORNING AND SUNDAY MORNING...
BUT 60M FALLS APPEAR BETWEEN SUNDAY AND MONDAY MORNING. ALSO...FALLS OF
60M ARE INDICATED BETWEEN THIS AFTERNOON AND SUNDAY AFTERNOON.
SO TEMPERATURES SUNDAY SHOULD BE 5 TO 10 DEGREES LOWER THAN TODAY'S...
AND LOWS MONDAY MORNING 5 TO 10 DEGREES COOLER THAN SUNDAY MORNING'S.

LOOKING AT ETA MSL PRESSURE FIELDS...ETA FRH WINDS LOOK GOOD...THOUGH
MIGHT BE A LITTLE HIGH AT 06Z AND 18Z SUNDAY.

RECOMMENDED FORECAST

NEZ005-023>025-130915-
CHERRY-GRANT-HOOKER-THOMAS-
INCLUDING THE COMMUNITIES OF VALENTINE...MULLEN
400 PM CDT SAT JUL 12 1997

.TONIGHT...THUNDERSTORMS LIKELY WITH HEAVY RAIN POSSIBLE.  LOW 60 TO
65. VARIABLE WIND 5 TO 10 MPH...BECOMING NORTHWEST 10 TO 15 MPH.
PROBABILITY OF MEASURABLE RAIN 60 PERCENT.
.SUNDAY...DECREASING CLOUDINESS WITH A 20 PERCENT CHANCE OF SHOWERS OR
THUNDERSTORMS.  HIGH IN THE MID 80S.  NORTHWEST WIND INCREASING TO 15 TO
25 MPH.
.SUNDAY NIGHT...MOSTLY CLEAR.  LOW 55 TO 60.
.MONDAY...MOSTLY SUNNY.  HIGH IN THE UPPER 80S.

NEZ006>010-026-029-038-130915
KEYA PAHA-BOYD-BROWN-ROCK-HOLT-BLAINE-LOUP-GARFIELD-WHEELER-CUSTER-
INCLUDING THE COMMUNITIES OF AINSWORTH...O NEILL...BURWELL...BROKEN BOW
400 PM CDT SAT JUL 12 1997

.TONIGHT...THUNDERSTORMS LIKELY WITH HEAVY RAIN POSSIBLE...ESPECIALLY
AFTER MIDNIGHT.  LOW IN THE MID 60S.  VARIABLE WIND 5 TO 10 MPH.
.SUNDAY...DECREASING CLOUDINESS WITH A 40 PERCENT CHANCE OF SHOWERS OR
THUNDERSTORMS.  HIGH IN THE MID 80S.  WIND BECOMING NORTHWEST AND
INCREASING TO 15 TO 25 MPH.
.SUNDAY NIGHT...MOSTLY CLEAR.  LOW 55 TO 60.
.MONDAY...MOSTLY SUNNY.  HIGH IN THE MID 80S.

NEZ004-022-130915-
SHERIDAN-GARDEN-
INCLUDING THE COMMUNITY OF OSHKOSH
400 PM CDT SAT JUL 12 1997

...TORNADO WATCH UNTIL 800 PM MDT...

.TONIGHT...THUNDERSTORMS LIKELY WITH SEVERE STORMS POSSIBLE.  LOW 60 TO
65.  WIND BECOMING NORTHWEST 10 TO 15 MPH.  PROBABILITY OF MEASURABLE
RAIN 60 PERCENT.
.SUNDAY...BECOMING PARTLY CLOUDY.  HIGH IN THE MID 80S.  NORTHWEST WIND
INCREASING TO 15 TO 25 MPH.
.SUNDAY NIGHT...MOSTLY CLEAR.  LOW IN THE MID 50S.
.MONDAY...MOSTLY SUNNY.  HIGH IN THE UPPER 80S.

NEZ035>037-056>059-069>071-130915-
ARTHUR-MCPHERSON-LOGAN-DEUEL-KEITH-PERKINS-LINCOLN-CHASE-HAYES-
FRONTIER-
INCLUDING THE CITIES OF OGALLALA...NORTH PLATTE...IMPERIAL
400 PM CDT SAT JUL 12 1997

.TONIGHT...A 40 PERCENT CHANCE OF THUNDERSTORMS.  LOW IN THE MID 60S.
WIND BECOMING NORTHWEST 10 TO 15 MPH.
.SUNDAY...BECOMING PARTLY CLOUDY WITH A 20 PERCENT CHANCE OF SHOWERS OR
THUNDERSTORMS.  HIGH IN THE MID 80S.  NORTHWEST WIND INCREASING TO 15
TO 25 MPH.
.SUNDAY NIGHT...MOSTLY CLEAR.  LOW 55 TO 60.
.MONDAY...MOSTLY SUNNY.  HIGH IN THE UPPER 80S.

VTN PP 064/085 058/088 053 49620
ANW PP 064/085 059/087 055 49640
ONL PP 066/084 060/086 058 49640
BBW PP 063/085 058/085 056 49640
LBF PP 064/086 058/086 055 49420
OGA PP 065/087 059/087 057 49420
IML PP 064/087 060/088 058 49420

SPRINGER

NEZ022-130150-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORTH PLATTE NE
819 PM CDT (719 PM MDT) SAT JUL 12 1997

...TORNADO WATCH NUMBER 597 ISSUED PREVIOUSLY FOR PARTS OF THE
EASTERN PANHANDLE HAS BEEN CANCELLED...

THE TORNADO WATCH ISSUED EARLIER THIS AFTERNOON FOR GARDEN COUNTY
HAS BEEN CANCELLED. HOWEVER...SCATTERED THUNDERSTORMS WILL STILL BE
POSSIBLE THROUGH THE EVENING...SOME OF WHICH MAY CONTAIN HEAVY RAIN
AND GUSTY WINDS.

STAY TUNED TO NOAA WEATHER RADIO...LOCAL RADIO OR TELEVISION...OR
CABLE TELEVISION FOR THE LATEST UPDATES CONCERNING THIS WEATHER
SITUATION.

JWS