Flash Flooding and Flood in Nebraska, May 29 to 30, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
351 PM CDT TUE MAY 29 2007

.SHORT TERM...LATEST WATER VAPOR IMAGERY ALONG WITH PAST MORNING
UPPER AIR DATA REVEALS A STRONG UPPER CYCLONE SITTING OVER THE
NORTHERN ROCKIES TO NORTHERN HIGH PLAINS.  THIS WAVE IS KEEPING A
FRONT STRETCHING FROM THE UPPER MIDWEST BACK INTO EASTERN COLORADO.
DEEP LOW TO MID LEVEL MOISTURE CAN BE SEEN AHEAD OF THIS BOUNDARY
WITH SURFACE DEWPOINTS IN THE MID 60S AND PW VALUES AROUND 150 TO
200 PERCENT OF NORMAL.  SCATTERED TO NUMEROUS CONVECTION IS ALREADY
SEEN ALONG THIS BOUNDARY ALTHOUGH LITTLE OF IT HAS BEEN SEVERE.
HOWEVER...VERY HEAVY RAINFALL HAS BEEN SEEN WITH THIS CONVECTION
WITH PORTIONS OF NORTHERN VALLEY COUNTY ALREADY SEEING OVER 4 INCHES
OF RAINFALL THIS PAST MORNING.

VERY BUSY NIGHT SHAPING UP FOR SOUTH CENTRAL NEBRASKA INTO NORTH
CENTRAL KANSAS AS THE AFOREMENTIONED UPPER WAVE KICKS OUT A LARGE
SPOKE OF ENERGY INTO THE CENTRAL PLAINS.  THIS WILL PUSH THE COLD
FRONT EAST OUT OF THE HIGH PLAINS INTO EASTERN SECTIONS OF KANSAS
AND NEBRASKA BY MID DAY ON WEDNESDAY.  GIVEN WEAK CAPPING...DEEP
MOISTURE AND PLENTY OF LARGE SCALE LIFT...WIDESPREAD CONVECTION
ALONG AND AHEAD OF THIS BOUNDARY LOOKS LIKELY.  GIVEN PW VALUES
AROUND 150 TO 200 PERCENT OF NORMAL...A MEAN STORM MOTION NEARLY
PARALLEL TO THE BOUNDARY FAVORING TRAINING OF CONVECTION AND AREAS
THAT HAVE ALREADY SEEN OVER 2 TO 4 INCHES OF RAINFALL...FLASH
FLOODING LOOKS VERY LIKELY ACROSS THE AREA.  GIVEN THIS...FLASH
FLOOD WATCH REMAINS IN EFFECT WITH SEVERAL HYDRO WARNINGS LIKELY TO
COME THROUGH THE NIGHT.  SEVERE THREAT SHOULD BE MINIMAL AS LOW AND
DEEP LAYER SHEAR ARE FAIRLY WEAK WHILE ONLY MODEST CAPE VALUES IN
THE 300-1500 J/KG RANGE EXIST.

ANTICIPATE CONVECTION TO LINGER INTO THE MORNING HOURS FOR AREAS
EAST OF HIGHWAY 281...BUT THIS SHOULD BEGIN TO SLIDE EAST OF THE
REGION BY MID AFTERNOON.  HOWEVER...PLENTY OF CLOUD COVER WILL
REMAIN ACROSS THE AREA WITH TEMPERATURES STAYING ON THE COOLER SIDE
WITH HIGHS IN THE LOWER TO MID 70S EXPECTED.  SUBSIDENCE SHOULD THEN
TAKE HOLD OF THE AREA FOR WEDNESDAY NIGHT AS THE UPPER LOW BEGINS TO
ROTATE INTO THE NORTHERN PLAINS.  THIS WILL PUSH THE COLD FRONT WELL
EAST OF THE REGION WHILE MUCH DRIER AND STABLE AIR INVADES THE AREA.

.LONG TERM...THURSDAY MORNING THROUGH TUESDAY...FORECAST CHALLENGES
WILL INCLUDE CHANCE OF PRECIPITATION ASSOCIATED WITH A SLOW MOVING
CLOSED LOW IN THE NORTHERN PLAINS.

MODELS AND ENSEMBLES GENERALLY TREND SLOWER WITH THE TROUGH/CLOSED
LOW CENTERED OVER THE NORTHERN PLAINS. TRENDS OVER THE LAST FEW DAYS
SUGGESTS A STRONGER RIDGE IN THE EAST WHICH WILL PREVENT THE
EASTWARD MUCH PROGRESSION OF THE TROUGH OVER THE PLAINS. THE ECMWF
HAS BEEN TENDING TO PROGRESS THE WAVE A BIT ON THE FAST SIDE...BUT
THIS MODEL HAS EVEN SLOWED THINGS DOWN COMPARED TO PREVIOUS RUNS.
THERE IS QUITE A BIT OF UNCERTAINTY ON WHAT THIS UPPER LOW WILL
EVENTUALLY DO AFTER A FEW DAYS...SO CONFIDENCE IS NOT HIGH AFTER
FRIDAY. WITH THE LATEST TRENDS...IT WOULD NOT BE OUTSIDE OF THE
REALM OF POSSIBILITY THAT THE UPPER LOW/TROUGH WILL HANG AROUND INTO
THE WEEKEND AND WILL PROBABLY PUT SOME SMALL CHANCES OF
PRECIPITATION THROUGH THE WEEKEND. THE LOGICAL THING TO DO WILL BE
TO CONTINUE TO LOWER TEMPERATURES AND INCREASE CLOUD COVER AT LEAST
FOR THURSDAY INTO FRIDAY AND TREND TOWARD ENSEMBLE MEANS AND
CLIMATOLOGY FOR THE WEEKEND AND BEYOND FOR TEMPERATURES.

&&

.AVIATION...BIGGEST AVIATION CHALLENGE FOR THE KGRI TERMINAL WILL
ONCE AGAIN REVOLVE AROUND WHEN TO INSERT THUNDERSTORMS INTO THE
FORECAST AND HOW LOW CEILINGS WILL DROP TONIGHT. APPEARS AS THOUGH
INITIAL BAND OF THUNDERSTORMS RIDING ACROSS THE KGRI TERMINAL THIS
AFTERNOON WILL SLIDE FAR ENOUGH NORTH TO BRING A BRIEF PERIOD OF
DRY CONDITIONS LATE THIS AFTERNOON INTO EARLY THIS EVENING.
HOWEVER...THUNDERSTORMS WILL RETURN DURING THE MID TO LATE EVENING
AND ARE NOT EXPECTED TO DISAPPEAR UNTIL SUNRISE ON WEDNESDAY.
CLOUD CEILINGS WILL BE VERY DIFFICULT TO MANAGE AS HEIGHTS ARE
LIKELY TO VARY FROM 1500 FT UP TO 5000 FT THIS AFTERNOON.
ANTICIPATE CLOUD CEILINGS WILL DROP BELOW 1000 FT OVERNIGHT AS THE
HEAVIER PRECIPITATION MOVES INTO THE AREA.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH WEDNESDAY
     MORNING FOR NEZ039>041-046>049-060>064-072>077-082>087.

KS...FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH WEDNESDAY
     MORNING FOR KSZ005>007-017>019.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE HASTINGS NE
1154 AM CDT TUE MAY 29 2007

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-
301200-
PHILLIPS-SMITH-JEWELL-ROOKS-OSBORNE-MITCHELL-VALLEY-GREELEY-NANCE-
SHERMAN-HOWARD-MERRICK-POLK-DAWSON-BUFFALO-HALL-HAMILTON-YORK-
GOSPER-PHELPS-KEARNEY-ADAMS-CLAY-FILLMORE-FURNAS-HARLAN-FRANKLIN-
WEBSTER-NUCKOLLS-THAYER-
1154 AM CDT TUE MAY 29 2007

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS WILL EXPAND IN COVERAGE ACROSS THE OUTLOOK AREA
TODAY INTO TONIGHT. THESE STORMS WILL BE CAPABLE OF PRODUCING VERY
HEAVY RAINFALL OVER AN EXTENDED PERIOD OF TIME. RAINFALL AMOUNTS
OF 2 TO 4 INCHES WITH ISOLATED AREAS SEEING UP TO 6 INCHES WILL BE
POSSIBLE BY WEDNESDAY MORNING. THIS HEAVY RAINFALL MAY CAUSE AREAS
OF FLASH FLOODING...LOWLAND FLOODING AND SIGNIFICANT RISES IN
RIVERS AND STREAMS. ALTHOUGH WIDESPREAD SEVERE THUNDERSTORMS ARE
NOT EXPECTED...A FEW STORMS MAY PRODUCE WIND GUSTS TO 50 MPH ALONG
WITH PENNY SIZED HAIL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

SCATTERED THUNDERSTORMS ARE EXPECTED TO CONTINUE INTO WEDNESDAY.
SOME OF THE THUNDERSTORMS WEDNESDAY MORNING COULD PRODUCE HEAVY
RAINFALL.

IN ADDITION...AN INTERMITTENT CHANCE OF THUNDERSTORMS WILL EXIST
THURSDAY THROUGH THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED THROUGH TONIGHT. SPOTTERS ARE
ENCOURAGED TO REPORT RAINFALL AMOUNTS.

&&

MORE INFORMATION MAY BE OBTAINED AT THE FOLLOWING WEB PAGE:
   HTTP://WWW.WEATHER.GOV/HASTINGS  (ALL LOWERCASE)