Areal Flood Advisory 2, NWS North Platte, NE

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
629 PM CDT THU APR 12 2012

.UPDATE...

.AVIATION...
IFR/LIFR CONDITIONS ARE ARE EXPECTED TO IMPROVE TO VFR WITH THE
PASSAGE OF TWO UPPER LEVEL DISTURBANCES TONIGHT.

ONGOING THUNDERSTORM ACTIVITY WILL SWEEP EAST AND NORTHEAST THIS
EVENING FOLLOWED BY A SECOND DISTURBANCE CURRENTLY ACROSS THE SRN
ROCKIES. THIS SECOND DISTURBANCE IS EXPECTED TO AFFECT THE
FORECAST AREA WITH ANOTHER ROUND OF TSTMS LATER TONIGHT WHICH
SHOULD EXIT ERN PTNS OF THE FCST AREA BY 15Z FRIDAY. VFR IS
EXPECTED ALL AREAS THEREAFTER.

&&

.PREV DISCUSSION... /ISSUED 247 PM CDT THU APR 12 2012/

SYNOPSIS...

UPPER AIR ANALYSIS THIS MORNING IS INDICATING A STRONG SHORTWAVE
TROUGH CROSSING THE CENTRAL ROCKIES. WV IMAGERY HAS THIS FEATURE
CROSSING COLORADO ATTM. A NICE 50 TO 60 KT MID LEVEL JET STREAK
EXTENDING FROM SAN DIEGO CA...TO ALBUQUERQUE NM...TO SOUTH OF DENVER
CO. AT THE SURFACE...LOW PRESSURE WAS NOTED OVER MORGAN COUNTY
COLORADO. A WARM FRONT EXTENDED FROM THE LOW ESE TO AROUND BENKELMAN
NEBRASKA...THEN SE TO COLBY KANSAS. A DRY LINE EXTENDED SOUTH TO
WEST OF LAMAR COLORADO. CU FIELD HAS BEGUN TO EXPAND EAST OF THE LOW
AND SOUTH ALONG THE DRY LINE.

DISCUSSION...

NEAR TERM...TONIGHT THROUGH SUNDAY...MAIN FORECASTING CHALLENGES ARE
SEVERE POTENTIAL TONIGHT...THEN PRECIPITATION CHANCES FOR SATURDAY
NIGHT INTO SUNDAY.

FOR TONIGHT...AM EXPECTING STORMS TO BE WELL ESTABLISHED EAST OF THE
TRIPLE POINT AND EAST ALONG THE WARM FRONT AND SOUTH ALONG THE DRY
LINE. THE TORNADO THREAT ATTM...APPEARS TO BE CONFINED ALONG THE
WARM FRONT IMPACTING THE FAR SOUTHWESTERN COUNTIES...WHILE LOCATIONS
NORTH OF THE WARM FRONT...ENCOMPASSING THE INTERSTATE 80
CORRIDOR...WILL BE FAVORABLE FOR LARGE HAIL GIVEN THE STEEP MID
LEVEL LAPSE RATES AND WET BULB ZEROS OF 7 TO 9 K FT AGL. ACROSS THE
CENTRAL AND EASTERN SANDHILLS...ALONG WITH NORTH CENTRAL NEBRASKA
HEAVY RAIN IS POSSIBLE OVERNIGHT AS CONVECTION CONGEALS INTO A MCS
ROOTED ON THE LOW LEVEL JET. WENT AHEAD AND INCREASED PRECIPITATION
CHANCES TO CATEGORICAL IN THE CENTRAL AND EAST OVERNIGHT AS ALL THE
NEAR RANGE MODEL SOLUTIONS HAVE A HIGH DEGREE OF AGREEMENT AND ARE
INDICATIVE OF DECENT AMOUNTS OF QPF.

FRIDAY THROUGH SATURDAY...THE UPPER LEVEL DISTURBANCE MENTIONED IN
THE SYNOPSIS...WILL LIFT NORTH NORTHEAST INTO THE WESTERN DAKOTAS
EARLY FRIDAY FORCING A FRONTAL BOUNDARY INTO EASTERN NEBRASKA. LIGHT
LOW LEVEL WESTERLY WINDS AND DRIER AIR WILL PUSH INTO THE FORECAST
AREA DRYING CONDS OUT FOR FRIDAY. LOW AMPLITUDE RIDGING WILL BUILD
IN BEHIND THE EXITING SHORTWAVE FRIDAY...LEADING TO CLEAR SKIES AND
WARMER TEMPERATURES. THE NEXT SHOT FOR PRECIPITATION WILL ARRIVE
OVERNIGHT FRIDAY NIGHT IN THE CENTRAL AND EAST AS THE RIDGE ALOFT BREAKS
DOWN AND MID LEVEL WARM AIR ADVECTION INCREASES ACROSS CENTRAL AND
EASTERN NEBRASKA.

SERLY WINDS WILL INCREASE SATURDAY AS LOW PRESSURE DEEPENS ACROSS
NWRN KS/SWRN NEBRASKA. THIS FEATURE WILL TRACK EITHER NORTH OR
NORTHEAST SATURDAY AND WILL HAVE A STRONG IMPACT ON TEMPERATURES AND
LOW LEVEL MOISTURE RETURN. THE NAM SOLN KEEPS THE LOW ANCHORED OVER
SWRN NEBRASKA WITH A WARM FRONT LIFTING NORTH INTO THE CENTRAL AND
NORTHERN CWA SATURDAY. THE GFS SOLN TRACKS THE SURFACE LOW
NEWD...THEN REDEVELOPS A LOW OVER NERN COLORADO SAT EVENING.
MOISTURE RETURN TO THE WEST...AS WELL AS STRATUS FORMATION IS MUCH
MORE PRONOUNCED WITH THE NAM SOLN AS STRONG EASTERLIES DEVELOP OVER
NORTHERN NEBRASKA SATURDAY. THE GFS SOLN IS MUCH WEAKER WITH THE
EASTERLIES...LEADING TO MUCH LESS SKY COVER AND WARMER TEMPS. GIVEN
THE MODEL DISAGREEMENTS...UTILIZED A MODEL BLEND FOR TEMPS AND
PRECIPITATION CHANCES SATURDAY AND SATURDAY NIGHT.

ON SUNDAY THE MAIN UPPER LEVEL LOW WILL BEGIN TO EMERGE AND TRACK
ACROSS THE CENTRAL PLAINS. WAS CONCERNED ABOUT SNOW INITIALLY THIS
MORNING BUT UPON FURTHER EXAMINATION AT THE NAM...GFS AND ECMWF
SOLNS IS INDICATING TEMPERATURES TOO WARM FOR ACCUMULATING SNOWS
ACROSS THE NRN CWA ON SUNDAY. THE ONLY MODEL WHICH LEANS IN THIS
DIRECTION IS THE CANADIAN WHICH IS MUCH LESS PROGRESSIVE AND DRAWS
IN MUCH COLDER AIR INTO NORTHERN NEBRASKA LATE SUNDAY AND SUNDAY
NIGHT. ATTM...DECIDED TO HOLD OFF ON SNOW SUNDAY.

SUNDAY NIGHT THE STORM SYSTEM WILL BE EXITING TO THE EAST...HOWEVER
COLD TEMPERATURES AND LINGERING WRAP AROUND MOISTURE WILL BE CAPABLE
OF PRODUCING SOME SNOWFALL. BATTLE BETWEEN PRECIP ENDING AND CHANGE
OVER SHOULD RESULT IN LITTLE IF ANY ACCUMULATION EXPECTED. IF SYSTEM
SLOWS DOWN...WITH MORE PRECIP SUNDAY NIGHT...SOME ACCUMULATING
SNOWFALL WILL BE POSSIBLE. WILL CONTINUE TO MONITOR THE SPEED OF THE
SYSTEM.

AS THE SYSTEM EXITS AN UPPER LEVEL RIDGE WILL BUILD OUT WEST. THIS
WILL CREATE A NORTHWEST FLOW REGIME...WHICH CONTINUES THROUGH MUCH
OF THE WEEK. THIS WILL LEAD TO SEVERAL DISTURBANCES/CLIPPER SYSTEMS
TO CROSS THE NORTHERN PLAINS. LIMITED MOISTURE AND GOOD LIFT TO
NORTH OF THE CWA...WILL RESULT IN MAINLY DRY CONDITIONS...HOWEVER
PERIODS OF ISOLATED SHOWERS WITH EACH WAVE WILL BE POSSIBLE. BETTER
CHANCES WILL BE OVER THE EASTERN CWA...WHEN THE SYSTEMS WILL TAP
INTO MORE MOISTURE.

TEMPERATURES NEXT WEEK WILL START OFF CHILLY ON MONDAY...DUE TO THE
INFLUENCE OF THE DEPARTING LOW. HIGHS WILL BE IN THE 40S AND LOWER
50S. THEN A WARM UP CAN BE EXPECTED THROUGH THE WEEK. HIGHS BY
THURSDAY WILL APPROACH THE UPPER 60S TO LOWER 70S.

AVIATION...

COMPLEX WEATHER TONIGHT AS LARGE LOW PRESSURE SYSTEM MOVES ACROSS
THE PLAINS. WIDESPREAD MVFR/IFR STRATUS AND FOG HAS DEVELOPED AND
WILL CONTINUE THIS EVENING. MEANWHILE NUMEROUS THUNDERSTORMS WILL
FIRE OVER NE COLORADO/NW KANSAS AND LIFT INTO THE REGION. IMPACT OF
STRONG THUNDERSTORMS EXPECTED AT KLBF...WITH LESS CONFIDENCE AND
STRENGTH FOR KVTN.

LATE TONIGHT INTO TOMORROW MORNING THE SYSTEM WILL EXIT WITH VFR
CONDITIONS SPREADING ACROSS THE AREA AND CONTINUING FOR FRIDAY.

&&

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

SHORT TERM/EXTENDED...CDC
AVIATION...CDC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
300 PM CDT THU APR 12 2012

NEZ004>010-022>029-035>038-056>059-069>071-094-132000-
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-
300 PM CDT THU APR 12 2012 /200 PM MDT THU APR 12 2012/

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

.DAY ONE...TONIGHT.

THIS EVENING...ISOLATED STRONG OR SEVERE THUNDERSTORMS ARE
POSSIBLE ACROSS THE SOUTHEAST PANHANDLE INTO WEST CENTRAL AND
SOUTHWEST NEBRASKA. THE PRIMARY AREA OF CONCERN WILL BE ALONG AND
SOUTH OF A LINE FROM OSHKOSH IN GARDEN COUNTY THROUGH BROKEN BOW
IN CUSTER COUNTY. LARGE HAIL IS THE PRIMARY CONCERN AT THIS TIME.
HOWEVER...A WARM FRONT STRETCHING ACROSS FAR SOUTHWEST NEBRASKA
WILL ACT AS A FOCUS FOR ADDITIONAL ISOLATED SEVERE STORM
DEVELOPMENT. STORMS THAT DEVELOP IN THIS AREA COULD SEE AN
ADDITIONAL THREAT FOR WIND DAMAGE OR ISOLATED TORNADO
DEVELOPMENT...GENERALLY SOUTHWEST OF A OGALLALA TO HAYES CENTER
LINE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

AN ACTIVE WEATHER PATTERN WILL SETUP BEGINNING FRIDAY NIGHT AND
LASTING INTO EARLY MONDAY. AS A STRONG UPPER LEVEL SYSTEM DIGS
INTO THE FOUR CORNERS REGION SATURDAY...THERE WILL BE A CHANCE
FOR THUNDERSTORMS LATE FRIDAY NIGHT INTO SATURDAY NIGHT. THEN ON
SUNDAY INTO EARLY MONDAY...THE SYSTEM WILL LIFT NORTHEAST ACROSS
NEBRASKA. AS COLD AIR IS DRAWN INTO THE SYSTEM...THE POTENTIAL FOR
SNOWFALL IS POSSIBLE ACROSS THE NORTHWESTERN HALF OF THE OUTLOOK
LATE SUNDAY INTO SUNDAY NIGHT. IN ADDITION...STRONG NORTHERLY
WINDS ARE POSSIBLE. THERE REMAIN SOME UNCERTAINTY ON THE TRACK AND
INTENSITY OF THE SYSTEM. LISTEN FOR THE LATEST FORECASTS REGARDING
THE POTENTIAL FOR WINTRY WEATHER DEVELOPMENT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING...FOR AREAS
GENERALLY SOUTHWEST OF AN OGALLALA TO HAYES CENTER LINE.

&&

THIS PRODUCT IS NOW AVAILABLE...ALONG WITH OTHER WEATHER...
HYDROLOGICAL AND CLIMATOLOGICAL INFORMATION...AT
HTTP://WWW.WEATHER.GOV/NORTHPLATTE

MASEK

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