Hail in Nebraska, April 18, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
ISSUED BY NATIONAL WEATHER SERVICE RAPID CITY SD
240 PM CDT MON APR 18 2005

.DISCUSSION...
THE MAIN FORECAST CONCERNS ARE THUNDERSTORMS THE NEXT SEVERAL
DAYS...ALONG WITH RELATIVELY HIGH CHANCES OF PRECIPITATION. ALL OF
THIS WILL BE KEYED UPON THE LARGE UPPER LOW OVER THE ROCKIES...AS
WELL AS THE ASSOCIATED SURFACE FRONT WHICH WILL MEANDER ACROSS THE
FORECAST AREA. LATEST OBSERVATIONS INDICATE THE SMALL/COMPACT UPPER
LEVEL SYSTEM CONTINUES TO MOVE ACROSS EASTERN NEBRASKA. THIS HAS
KEPT SHOWERS AND CLOUDS OVER THE FAR EASTERN FORECAST AREA MUCH OF
THE DAY. DUE TO THE SLOW MOVEMENT OF THIS SYSTEM...WILL KEEP POPS
UNTIL 06Z FOR THIS AREA. AN ADDITIONAL CONCERN TONIGHT IS LOW CLOUD/
FOG DEVELOPMENT OVER PARTS OF CENTRAL NEBRASKA. WITH RELATIVELY
LIGHT SOUTHEAST WINDS AND INCREASING LOW-LEVEL MOISTURE...WOULD NOT
BE SURPRISED TO SEE AREAS/PATCHY FOG AFTER 06Z. FINALLY...THERE IS
SOME POTENTIAL FOR THUNDERSTORMS OVER THE FAR NWRN FORECAST AREA AS
A WEAK WAVE MOVES ACROSS THE NORTHERN PLAINS. LOW-LEVEL MOISTURE
WILL BE RETURNING TO THIS AREA...AND A CUMULUS FIELD HAD ALSO
DEVELOPED ACROSS SOUTHEASTERN WYOMING AND FAR WESTERN NEBRASKA.
MLCAPE WAS < 250 J/KG...AND MLCIN WAS > 100 J/KG...SO IT WILL TAKE
SOME DECENT FORCING TO GET THINGS GOING. A SURFACE LOW PRESSURE NEAR
CHEYENNE IS PROGGED TO MOVE SLOWLY SOUTHEAST TONIGHT...WHILE A
SURFACE FRONT (WHICH HAS RECENTLY ENTERED THE FAR NORTHWESTERN
FORECAST AREA) MOVES INTO CENTRAL NEBRASKA. THIS MAY HELP A FEW
STORMS FIRE LATER THIS EVENING OVER THE FAR NORTHWESTERN FORECAST
AREA...BUT AGAIN...THE BEST SYNOPTIC FORCING WILL REMAIN TO OUR
NORTHWEST.

ON TUESDAY...THE ATMOSPHERE MAY SETUP FOR A DECENT SEVERE WEATHER
EVENT...ESPECIALLY ACROSS THE CENTRAL/NORTHERN FORECAST AREA. THE
SURFACE FRONTAL BOUNDARY WILL DROP SOUTH INTO THE NORTH PLATTE
AREA...WITH MOIST EASTERLY FLOW TO THE NORTH OF THIS FRONT. SBCAPE
VALUES WILL BE FROM 1000-3000 J/KG ALONG/NEAR THIS FRONT. ASSUMING
CONVECTIVE INITIATION (WHICH IS REASONABLE GIVEN THE ANTICIPATED
FORCING AND REDUCED MLCIN)...DEEP-LAYER SHEAR SHOULD BE MORE THAN
SUPPORTIVE FOR SUPERCELLS. FORECAST HODOGRAPHS SUGGEST RIGHT-MOVERS
WILL MOVE SLOWLY EAST ALONG THE BOUNDARY...WHILE LEFT-MOVERS TRAVEL
NORTH INTO THE INCREASINGLY STABLE AIR (PERHAPS BECOMING ELEVATED
HAILERS). THE POTENTIAL ALSO EXISTS FOR A FEW TORNADOES WITH ANY
SUPERCELLS NEAR THE WARM FRONT. LASTLY...EXPECT A FAIRLY STRONG
TEMPERATURE CONTRAST ACROSS CENTRAL NEBRASKA TUESDAY DUE TO THE
FRONTAL BOUNDARY.

FOR TUESDAY NIGHT...THE MODELS SUGGEST AN MCS WILL MOVE ACROSS THE
NORTHERN/CENTRAL FORECAST AREA AS STRONG ISENTROPIC LIFT AND THETA-E
ADVECTION PERSIST ALONG THE EAST-WEST BOUNDARY. HAVE THUS INCREASED
THE POPS FROM PREVIOUS FORECAST OVER THIS AREA. WEDNESDAY MAY BRING
A RELATIVE MINIMUM IN SHOWER/THUNDERSTORM ACTIVITY AS SHORT-WAVE
RIDGING OCCURS IN THE WAKE OF THE ANTICIPATED MCS. HOWEVER...SOME
LINGERING SHOWERS/STORMS ARE EXPECTED OVER THE EASTERN FORECAST
AREA...AND ANOTHER ROUND OF SHOWERS/STORMS IS EXPECTED TO DEVELOP
LATE IN THE DAY OVER THE FAR WESTERN FORECAST AREA. A SEVERE THREAT
WILL ONCE AGAIN EXIST...BUT THIS TIME OVER THE FAR SOUTHERN FORECAST
AREA AS THE SURFACE FRONT CONTINUES ITS SOUTHWARD PUSH. ON WEDNESDAY
NIGHT AND THURSDAY...MODELS CONTINUE IN DECENT AGREEMENT ON EJECTING
A STRONG WAVE ACROSS THE NORTHERN PLAINS. THIS SHOULD BRING ANOTHER
ROUND OF FAIRLY WIDESPREAD SHOWERS AND THUNDERSTORMS.

NOT MUCH TO SAY ABOUT THE EXTENDED FORECAST PERIOD...EXCEPT A DRYING
TREND IS ANTICIPATED FRIDAY THROUGH SUNDAY AS UPPER-LEVEL RIDGING
DEVELOPS.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...NONE.

&&

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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
ISSUED BY NATIONAL WEATHER SERVICE RAPID CITY
330 PM CDT MON APR 18 2005

NEZ004>010-022>029-035>038-056>059-069>071-094-191030-
ARTHUR-BLAINE-BOYD-BROWN-CHASE-CUSTER-DEUEL-EASTERN CHERRY-FRONTIER-
GARDEN-GARFIELD-GRANT-HAYES-HOLT-HOOKER-KEITH-KEYA PAHA-LINCOLN-
LOGAN-LOUP-MCPHERSON-PERKINS-ROCK-SHERIDAN-THOMAS-WESTERN CHERRY-
WHEELER-
330 PM CDT MON APR 18 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND NORTH CENTRAL
NEBRASKA.

.DAY ONE...TONIGHT

AS A SURFACE FRONT AND UPPER LEVEL STORM APPROACH THE PANHANDLE...
ISOLATED THUNDERSTORMS ARE EXPECTED ACROSS NORTHWESTERN PORTIONS OF
THE OUTLOOK AREA. WITH DRY AIR IN THE LOW LEVELS OF THE
ATMOSPHERE...THUNDERSTORMS WHICH DO DEVELOP MAY PRODUCE GUSTY WINDS.
HOWEVER...AT THIS TIME...WINDS SHOULD REMAIN BELOW SEVERE LIMITS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

AN ACTIVE WEATHER PATTERN WILL BEGIN ON TUESDAY...CONTINUING INTO THE
REMAINDER OF THE WORK WEEK. ON TUESDAY...A SLIGHT RISK FOR SEVERE
THUNDERSTORMS EXISTS FOR THE ENTIRE OUTLOOK AREA. A SURFACE FRONTAL
BOUNDARY WILL MOVE ACROSS CENTRAL PORTIONS OF THE OUTLOOK AREA...
BEFORE STALLING TUESDAY AFTERNOON. ABUNDANT LOW LEVEL MOISTURE WILL
MOVE WEST INTO THE OUTLOOK AREA FROM EASTERN NEBRASKA. THESE SURFACE
FEATURES WILL COMBINE WITH AN UPPER LEVEL STORM MOVING INTO
WESTERN NEBRASKA LATE IN THE DAY...RESULTING IN THUNDERSTORMS. AT
THIS TIME...THE GREATEST SEVERE WEATHER THREAT WILL BE FROM LARGE
HAIL AND DAMAGING WINDS.

ON WEDNESDAY...ANOTHER ROUND OF SEVERE WEATHER IS POSSIBLE ACROSS
SOUTHERN AND EASTERN PORTIONS OF THE OUTLOOK AREA. AREAS EAST OF A
LINE FROM IMPERIAL...TO PAXTON...TO BREWSTER...TO CHAMBERS...STAND
THE BEST CHANCE OF SEVERE WEATHER...WITH THE MAIN THREAT FROM LARGE
HAIL AND DAMAGING WINDS. A SURFACE FRONT WILL STALL ACROSS SOUTHERN
AND CENTRAL NEBRASKA ON WEDNESDAY. ABUNDANT LOW LEVEL MOISTURE...
COUPLED WITH A SERIES OF UPPER LEVEL STORMS...WILL TRIGGER
THUNDERSTORM DEVELOPMENT ACROSS THE ENTIRE OUTLOOK AREA.

THUNDERSTORMS ARE POSSIBLE AGAIN ON FRIDAY...MAINLY EAST OF A LINE
FROM VALENTINE TO NORTH PLATTE. AT THIS TIME...NO SEVERE WEATHER IS
ANTICIPATED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED ACROSS THE ENTIRE OUTLOOK AREA ON
TUESDAY...AND EAST OF A LINE FROM IMPERIAL...TO PAXTON...TO
BREWSTER...TO CHAMBERS ON WEDNESDAY.

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