Flash Flooding in Nebraska, May 28 to 30, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
249 PM CDT MON MAY 28 2007

.DISCUSSION...
THE GFS HAS BEEN LEADING THE WAY. THE GFS...NAM12 AND ECMWF ALL NOW
INDICATE A LARGE CUT OFF LOW WILL FORM ACROSS THE DAKOTAS AND
TRIGGER A SERIES OF MCSS ACROSS THE CNTL PLAINS THROUGH THURSDAY. THE
OFFICIAL FCST USES A BLEND OF THE HPC...NAM12 AND GFS DATA. POPS HAVE
BEEN RAISED TO THE LIKELY CATEGORY TUESDAY IN KEEPING WITH THE SLOWER
GFS SOLN.

FOR TONIGHT...CONVECTIVE INITIATION IS EXPECTED IN THE PANHANDLE
WITH A MCS FORMING. ACTIVITY IS EXPECTED TO SPREAD SLOWLY EAST
OVERNIGHT. INSTABILITY THIS AFTN IS GREATEST ACROSS SWRN NEB. SHEAR
IS WEAK BUT INSTABILITY AND MOISTURE ARE HIGH SO SOME SORT OF
MULTICELL SYSTEM IS EXPECTED TO FORM. PARAMETERS ARE IN PLACE FOR
VERY DEEP CONVECTION WITH SEVERE HAIL AND PERHAPS WIND DAMAGE.

A SECOND MORE LINEAR MCS IS EXPECTED TO FORM ACROSS CNTL AND ERN
ZONES TUESDAY AFTERNOON AND OVERNIGHT. THERE ARE SIGNIFICANT
DIFFERENCES IN THE LOCATION BUT SOMEWHERE BETWEEN KIML AND KONL
LOOK TO BE FAVORED.

A THIRD SYSTEM COULD FORM WEDNESDAY OFF THE BLACK HILLS AND SPREAD
SOUTHEAST OVERNIGHT AND INTO THURSDAY AFFECTING MAINLY THE NCNTL
ZONES. THE LATEST SOLNS INDICATE 1 TO 3 INCHES OF RAINFALL
LIKELY TONIGHT THROUGH THURSDAY AFTN.

FRIDAY THROUGH MONDAY...THE FCST FOLLOWS THE HPC GRIDS WHICH
SUGGEST A GENERALLY DRY...COOL AND STABLE PATTERN WILL DEVELOP.
HEIGHT RISES IN THE WRN U.S. AND A PERSISTENT TROF IN THE ERN U.S.
WILL KEEP THE FCST AREA IN A NW FLOW ALOFT WITH COOL HIGH PRESSURE
BUILDING SOUTH KEEPING THINGS STABLE AT THE SFC. THE FCST IS
GENERALLY DRY DURING THIS PERIOD.

&&

.AVIATION...
MODERATE INSTABILITY IS IN PLACE ACROSS THE LBF CWA HELPED IN PART
BY THE STRONG RETURN OF MOISTURE. THIS IS LEADING TO OCNL MVFR
CEILING MAINLY ALONG AND EAST OF HIGHWAY 83. THESE LOWER CLOUD DECKS
MAY TEMPORARILY LIFT TO VFR CONDTIONS THROUGH THE LATE AFTERNOON AND
EVENING...BUT ARE EXPECTED BACK BY THE EARLY MORNING HOURS AND WILL
MOST LIKELY SPREAD BACK TO THE WEST. A FOCUSING MECHANISM IN THE THE
FORM OF A TROF WILL HELP CONVECTION TO SPREAD OUT OF THE PANHANDLE
INTO THE SOUTWHEST AND WEST CENTRAL NEBRASKA THIS EVENING...WITH
SHOWERS AND THUNDERSTORM BECOMING MORE WIDESPREAD ALONG AND BEHIND A
COLD FRONT MOVING THROUGH DURING TUESDAY MORNING. MVFR TO OCCASIONAL
IFR CONDITIONS MAY EXIST IN THE STRONGER CELLS WITH VSBY DROPPING TO
NEAR A MILE WITH HEAVY RAIN...SMALL HAIL...AND DANGEROUS WIND GUSTS
TO SMALL AIRCRAFT. VFR CONDITIONS DO NOT LOOK TO PREVAIL AT LEAST
UNTIL TUESDAY AFTERNOON...BUT A LARGE UPPER LOW SPINNING INTO THE
AREA WILL KEEP UNSETTLED WEATHER IN PLACE THROUGH MID WEEK.
&&

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

&&

CDC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
318 PM CDT MON MAY 28 2007

NEZ004>010-022>029-035>038-056>059-069>071-094-291200-
SHERIDAN-EASTERN CHERRY-KEYA PAHA-BOYD-BROWN-ROCK-HOLT-GARDEN-
GRANT-HOOKER-THOMAS-BLAINE-LOUP-GARFIELD-WHEELER-ARTHUR-MCPHERSON-
LOGAN-CUSTER-DEUEL-KEITH-PERKINS-LINCOLN-CHASE-HAYES-FRONTIER-
WESTERN CHERRY-
318 PM CDT MON MAY 28 2007 /218 PM MDT MON MAY 28 2007/

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

.DAY ONE...TONIGHT.

THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE OVER ALL OF WESTERN AND
NORTH CENTRAL NEBRASKA TONIGHT. THE THREAT OF SEVERE WEATHER
DEVELOPMENT WILL BE MAINLY THROUGH MIDNIGHT ACROSS PORTIONS OF
SOUTHWEST NEBRASKA INTO THE SANDHILLS AND PANHANDLE REGIONS. THE
GREATEST RISK AREA WILL BE ALONG AND WEST OF A BROKEN BOW TO
VALENTINE LINE WHERE LARGE HAIL WILL BE THE MAIN THREAT. A FEW
STORMS MAY ALSO CONTAIN WIND GUSTS OVER 60 MPH THIS EVENING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

INSTABILITY IN THE WAKE OF THE FRONT WILL HELP GENERATE ISOLATED
THUNDERSTORMS AGAIN TUESDAY AFTERNOON AND EVENING. THE THREAT FOR
THUNDERSTORMS IS LIKELY TO DECREASE SIGNIFICANTLY AFTER THE
MAXIMUM DAYTIME HEATING. SEVERE THUNDERSTORM DEVELOPMENT DOES NOT
LOOK LIKELY AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED ACROSS PORTIONS OF SOUTHWEST
NEBRASKA INTO THE SANDHILLS AND THE EASTERN PANHANDLE THROUGH THE
MID EVENING HOURS.

&&

THIS PRODUCT IS NOW AVAILABLE...ALONG WITH OTHER WEATHER...
HYDROLOGICAL AND CLIMATE INFORMATION...AT
HTTP://WWW.CRH.NOAA.GOV/LBF(ALL LOWERCASE)

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