Severe Thunderstorm Warning 83, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
205 PM CDT MON JUN 25 2001

WITH RADAR-ESTIMATED ANTECEDENT RAINFALL OF 2-3 INCHES IN LAST
NIGHT'S CONVECTION (AFTER ATTEMPTING TO CORRECT FOR HAIL)...HEAVY
RAINFALL POTENTIAL IN THE FIRST PERIOD IS A MAJOR CONCERN NEAR THE
LINCOLN, PERKINS, CHASE, HAYES COUNTY JUNCTION, AND IN CENTRAL HOLT
COUNTY.

...18Z SYNOPSIS...
    A SURFACE FRONT WAS DRAPED FROM NORTH CENTRAL NEBRASKA INTO A
LOW IN NORTHEAST COLORADO. THERE WERE APPARENTLY SEVERAL BOUNDARIES
OR WINDSHIFT LINES IN CENTRAL SOUTH DAKOTA AND NORTH CENTRAL
NEBRASKA...IN THE WARMER AIR OVER SOUTHWEST NEBRASKA...AND IN
NORTHEAST NEBRASKA WHERE THIS MORNING'S CONVECTION WAS. THE KLNX WSR-
88D AND VISIBLE SATELLITE SHOWED CONVECTION IN CENTRAL AND NORTH
CENTRAL NEBRASKA. WIND PROFILERS AND WATER VAPOR IMAGERY LOOPS
INDICATED WEAK UPPER WIND FIELDS OVER 15-30KT 850MB AND 700MB
WIND IN KANSAS AND NEBRASKA.
...MODELS...
    THE ETA IS THE MODEL OF CHOICE FOR THE NEW FORECAST THIS
AFTERNOON FOR THE FIRST THREE PERIODS WITH THE AVN PREFERRED FOR
THE FOURTH AND FIFTH PERIODS AND DAYS 3 AND 4. THE MRF SEEMS OKAY
FOR DAYS 5-7.
    THE PREVIOUS RUNS OF THE ETA AND AVN DID WELL WITH THE
LOCATIONS OF THE UPPER LOWS IN THE SOUTHEAST AND ALONG THE COAST OF
BRITISH COLUMBIA. THEY ARE ALSO CONSISTENT WITH THE PREVIOUS RUN.
    THE MRF CONTINUES SHOWING GOOD CONTINUITY BETWEEN RUNS...AND THE
25/00Z RUN DID WELL WITH THE STRENGTH AND LOCATION OF THE UPPER
FEATURES THIS MORNING.

...FORECAST...
    THE HEAVY RAIN AREA IN THE SOUTHWEST WAS EXTREMELY LOCALIZED. OUR
HIGHEST GROUND TRUTH REPORTS SO FAR IN THE SOUTHWEST HAVE BEEN 1.00-
1.50 INCHES IN THE AREA SURROUNDING THE BULLSEYE NEAR WALLACE. IN THE
NORTHEAST...ACTUAL REPORTS HAVE BEEN ABOUT AN INCH IN THE HEAVIEST
AREAS. SO, FOR NOW, I WILL NOT GO WITH FFA'S TONIGHT.
    THIS MORNING'S 850MB DEWPOINT ANALYSIS SHOWED 15C ON AN AXIS
INL-FSD-LNK...AND PRECIPITABLE WATER THIS MORNING RANGED FROM AN
INCH IN WESTERN NEBRASKA TO NEARLY 1.5 IN THE EAST. THE HIGHEST
INSTABILITY AND WEAKEST INHIBITION WILL BE EAST OF A VTN-LBF LINE
INITIALLY WHERE THE DEEPEST MOISTURE WAS INDICATED THIS MORNING. BY
06Z THE MOISTURE AND INSTABILITY SHIFTS TO THE NORTHWEST IN THE AREA
NORTH AND WEST OF AN ANW-MHN-BFF LINE AND FINALLY WELL INTO SOUTH
DAKOTA. WITH STEERING WIND LESS THAN 15KT...SLOW-MOVING CELLS AND
PERSISTENT OR EVEN BACK-BUILDING CLUSTERS ARE LIKELY WHERE THEY DO
DEVELOP. THE BEST FORCING WILL BE NORTH AND WEST OF AN ONL-LXN-IML
LINE WHERE 800-700MB WARM ADVECTION AND 2D-FRONTOGENESIS ARE
STRONGEST. THIS COINCIDES WITH THE STRONGEST LOW LEVEL CONVERGENCE.
THE 700-300MB DCVA IS STRONGEST ALONG THE SOUTH DAKOTA BORDER WEST
AND NORTH OF VALENTINE AND MULLEN THROUGH THE NIGHT. FACTORING IN THE
LOW LEVEL JET DEVELOPING TOWARD 06Z...THE BEST POTENTIAL FOR MCS
DEVELOPMENT IS NORTH AND WEST OF AN ONL-BBW-MHN LINE. WITH
CONVECTION DEVELOPING ALREADY IN CENTRAL AND NORTH CENTRAL
NEBRASKA...I WOULD EXPECT ALL BUT THE SOUTHWEST TO BE PRIME AREA FOR
CONTINUED DEVELOPMENT. IN THE SOUTHWEST THERE REALLY IS NO BOUNDARY
FOR FOCUSING CONVECTION...THOUGH INSTABILITY AND HEAT ARE THERE.
    THE NORTHWARD PROGRESS CONTINUES INTO WEDNESDAY NIGHT. IN THE
SAME TIME...THE LOW LEVEL RH DECREASES. SO...PARTLY CLOUDY AND DRY
CONDITIONS ARE LIKELY. WITH 850MB TEMPERATURES OF 23-29C AND 925MB
VALUES OF 31-34C...DAYTIME TEMPERATURES SHOULD HAVE NO TROUBLE
GETTING INTO THE 90S. EVEN INTO THURSDAY NIGHT...THE FORCING AND
MOISTURE STAY EAST OF THE FORECAST AREA.
    IN THE EXTENDED PORTION...I WILL PRETTY MUCH CONTINUE WITH WHAT
THE CURRENT FORECAST IS SHOWING. ALTHOUGH 850MB 2D-FRONTOGENESIS AND
CONVERGENCE RETURN TO WESTERN NEBRASKA FRIDAY...THE MOISTURE STAYS
IN THE DAKOTAS UNTIL SATURDAY EVENING. FOR TUESDAY...LOW LEVEL
CONVERGENCE, RH, AND 2D-FRONTOGENESIS IS SUFFICIENT TO IWARRANT A
CHANCE OF THUNDERSTORMS. THE 850MB TEMPERATURES WILL BE ABOUT 3C
COOLER THAN MONDAY AND ABOUT THE SAME AS SUNDAY.

.LBF...NONE.

SPRINGER

NEZ004>010-022>029-035>038-056>059-069>071-262045-

SEVERE WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1055 AM CDT TUE JUN 26 2001

...STORM SPOTTER ACTIVATION WILL LIKELY BE NEEDED TODAY INTO
TONIGHT...

THERE IS A CHANCE OF SEVERE THUNDERSTORMS TODAY INTO TONIGHT OVER
ALL OF WESTERN AND NORTH CENTRAL NEBRASKA.  THE GREATEST RISK OF
SEVERE WEATHER WILL INITIALLY BE EAST OF BURTON TO TAYLOR LINE LATE
THIS MORNING BUT WILL THEN SHIFT WEST OF A VALENTINE TO CURTIS LINE
BY EARLY AFTERNOON.  THE RISK OF SEVERE THUNDERSTORMS WILL THEN
SHIFT SLOWLY EAST ACROSS THE REMAINDER OF THE OUTLOOK AREA BY LATE
AFTERNOON INTO THE EVENING.

A COLD FRONT WILL REMAIN NEARLY STATIONARY ACROSS WESTERN AND NORTH
CENTRAL NEBRASKA TODAY BEFORE FINALLY LIFTING BACK NORTH INTO
SOUTH DAKOTA BY LATE TONIGHT.  A VERY MOIST AND UNSTABLE ATMOSPHERE
WILL EXIST ALONG THIS FRONT THROUGH TONIGHT HELPING NUMEROUS
THUNDERSTORMS TO DEVELOP ACROSS THE AREA.  WITH WEAK WINDS ALOFT
THESE STORMS WILL EXHIBIT VERY LITTLE MOVEMENT AND HAVE THE
POTENTIAL TO PRODUCE HEAVY RAINFALL AND LOCALIZED FLASH FLOODING.
LARGE HAIL AND BRIEF DAMAGING WINDS WILL ALSO BE A THREAT WITH
THESE THUNDERSTORMS.

AWJ