Hail and Damaging Wind in Nebraska, July 30, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
215 PM CDT TUE JUL 30 2002

...FORECAST PROBLEM TODAY IS THE CHANCES OF THUNDERSTORMS TONIGHT IN
THE EASTERN FORECAST AREA AND AFTER MID-WEEK...

...18Z SYNOPSIS...
     SURFACE ANALYSIS INDICATED A FRONT ACROSS SOUTH DAKOTA AND A
DEWPOINT BOUNDARY FROM VALENTINE TO IMPERIAL. SURFACE BASED LIFTED
INDEX WAS -2C TO -10C FROM WEST TO EAST. THE 6.7U IMAGERY AND WIND
PROFILERS SHOWED WESTERLY FLOW ALOFT AND PROMINENT LARGE VORTICES
OVER THE PACIFIC OFF THE COAST OF CALIFORNIA AND OVER THE GULF OF
CALIFORNIA.

...MODELS...
     THIS MORNINGS GLOBAL AND ETA ARE VERY CLOSE IN THEIR
RESOLUTION OF SURFACE AND UPPER LEVEL FEATURES AND, THIS MORNINGS
GLOBAL PRETTY MUCH AGREES WITH LAST NIGHTS THROUGH SATURDAY
EVENING. SO, FOR THE FIRST FOUR DAYS, I WILL USE THE ETA AND THE
AVN GLOBAL AND BLEND IT TO THE MRF GLOBAL FROM LAST NIGHT.
     I HAVE MODERATE CONFIDENCE IN 30/00Z GLOBAL SOLUTION THROUGH
AT LEAST FRIDAY. THE GLOBAL MODEL PSU ENSEMBLES FROM LAST NIGHTS RUN
SHOW LITTLE VARIABILITY THROUGH DAY5 WITH THE UPPER LEVEL HEIGHTS OR
THE MSL PRESSURES. ALSO, THE ECMWF LENDS SUPPORT TO THE 30/00Z GLOBAL
SOLUTION. BEYOND FRIDAY, THE MRF GLOBAL THE UPPER LEVEL HIGH
BUILDING UP AGAIN AT THE BEGINNING OF NEXT WEEK. SINCE THIS HAS BEEN
THE PATTERN THROUGH MOST OF THE SEASON, I HAVE NO REASON TO DISPUTE
IT NOW.

...FORECAST...
     THE ETA GRID TEMPERATURES FOR WEDNESDAY INDICATE HIGHS RANGING
FROM 96 IN THE NORTHWEST FORECAST AREA TO 108 IN THE NORTHEAST. THAT
LOOKS REASONABLE WITH THE FRONT NOT PUSHING COMPLETELY THROUGH THE
FORECAST AREA UNTIL LATE AFTERNOON. THE GRID TEMPERATURES FOR
THURSDAY AND BEYOND SEEMED TO BE TOO LOW FOR THE SEASON, THOUGH
CLOUDINESS AND PRECIPITATION WILL HOLD THEM DOWN THURSDAY AND
FRIDAY.
     THE ETA SHOWS INSTABILITY IN THE EASTERN HALF OF NEBRASKA THIS
EVENING ALONG WITH LOW LEVEL CONVERGENCE AND WARM ADVECTION. THIS
WOULD GIVE A CHANCE OF THUNDERSTORMS FROM VALENTINE AND NORTH PLATTE
AND EAST. HOWEVER, THE CONDENSATION PRESSURE DEFICITS ARE 100-200MB
WEST OF ONL-EAR AT 700MB AND 200-250MB AT 850MB. SO, CHANCES OF
MEASURABLE PRECIPITATION ARE REALLY VERY SMALL. SO, I WILL KEEP PUT
ISOLATED THUNDERSTORMS IN THE NORTHEAST FOUR COUNTIES OF OUR FORECAST
AREA AND LEAVE THE MENTION OUT OF THE REST OF THE AREA. I MAY NEED TO
MAKE SOME LAST MINUTE ADJUSTMENTS BASED ON RADAR AND SATELLITE.
     A FRONT MOVES INTO SOUTHERN NEBRASKA WEDNESDAY EVENING AND
WILL GENERATE PLENTY OF LIFT WITH LOW LEVEL CONVERGENCE AND WARM
ADVECTION AND ELEVATED 2D-FRONTOGENESIS AND 700-500MB DCVA
(DIFFERENTIAL CYCLONIC VORTICITY ADVECTION). HOWEVER, WITH
CONDENSATION DEFICITS OF 200-300MB AT 925MB AND 850MB AND 100-200MB
AT 700MB, MEASURABLE PRECIPITATION IS REALLY UNLIKELY THROUGH
THURSDAY AFTERNOON. THE FRONT BECOMES STATIONARY IN SOUTHERN
NEBRASKA AND NORTHERN KANSAS. THEN, THE MOISTURE FIELDS BECOME MORE
FAVORABLE THURSDAY NIGHT AND FRIDAY. THE MOISTURE AND FORCING SHOWS
THIS SITUATION CONTINUING INTO SATURDAY NIGHT. CONSIDERING THE
DROUGHT SITUATION, I AM A LITTLE RELUCTANT TO INTRODUCE THE CHANCES
OF THUNDERSTORMS FOR SATURDAY. AT THIS TIME IM CONSIDERING A
COMPROMISE BETWEEN THE NEW GLOBAL AND THE EXISTING FORECAST AND I
WILL NOT GO HIGHER THAN A SLIGHT CHANCE SATURDAY AND/OR SATURDAY
NIGHT. FOR SUNDAY, MONDAY, AND TUESDAY, I WILL KEEP THE FORECAST
DRY.

.LBF...NONE

SPRINGER

NEZ004>010-022>029-035>038-056>059-069>071-094-302045-

HAZARDOUS WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1106 AM CDT TUE JUL 30 2002

...STORM SPOTTER ACTIVATION MAY BE NECESSARY ACROSS PORTIONS OF
THE OUTLOOK AREA THIS AFTERNOON AND EVENING...

THERE IS A RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING
ACROSS PARTS OF NORTH CENTRAL NEBRASKA. THIS MAIN RISK IS ACROSS
BOYD...HOLT...GARFIELD AND WHEELER COUNTIES.

A WEAK FRONTAL BOUNDARY REMAINS STALLED ACROSS THE SOUTH DAKOTA AND
NEBRASKA BORDER. AN UPPER LEVEL DISTURBANCE MOVING INTO NORTH
CENTRAL NEBRASKA...WILL INTERACT WITH THE FRONT TO PRODUCE
THUNDERSTORMS LATER THIS AFTERNOON AND EVENING. DUE TO LACK OF
MOISTURE IN THE LOWER LEVELS OF THE ATMOSPHERE...STORMS WHICH DO
DEVELOP WILL BE ISOLATED AND HIGH BASED. SINCE THE THUNDERSTORMS
WILL BE ELEVATED IN NATURE...HIGH WINDS WILL BE THE MAIN SEVERE
WEATHER THREAT. DUE TO LACK OF LOW LEVEL MOISTURE...ELEVATED
THUNDERSTORMS WILL PRODUCE DRY LIGHTNING WITH LITTLE IN THE WAY OF
MEASURABLE RAINFALL. THIS WILL ELEVATE THE FIRE DANGER.

ISOLATED THUNDERSTORMS ARE POSSIBLE EAST OF A LINE EXTENDING FROM
VALENTINE TO BROKEN BOW...AND WEST OF BOYD...HOLT AND WHEELER
COUNTIES. WITH DRY LOW LEVEL AIR IN PLACE...THUNDERSTORMS WILL BE
VERY ELEVATED WITH LITTLE OR NO RAINFALL. SOME BRIEF GUSTY WINDS MAY
DEVELOP WITH THE STORMS...HOWEVER WINDS SHOULD REMAIN BELOW SEVERE
CRITERIA.