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000
FXUS63 KLBF 240251
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
951 PM CDT THU MAY 23 2013

.UPDATE...
ISSUED AT 950 PM CDT THU MAY 23 2013

JUST UPDATED THE FORECAST TO ADDRESS CLOUD COVER IN THE WEST AND
ITS EXPECTED ONSET IN THE CENTRAL CWA OVERNIGHT. THE LATEST NAM
SOLN THIS EVENING HAS SLOWED THE PROGRESSION OF STRATUS TO THE
EAST AND HAVE ADJUSTED THE FORECAST ACCORDINGLY. ATTM NOT
EXPECTING ANY FOG POTENTIAL OVERNIGHT...AS SERLY WINDS CONTINUE TO
BE BREEZY AND WILL ONLY DIMINISH SOMEWHAT OVERNIGHT. LOWS IN THE
LOWER TO MID 50S REMAIN ON TRACK WITH THE DECENT MIXING AND THE
ARRIVAL OF LOW LEVEL MOISTURE. ISOLATED SHOWERS WILL BE POSSIBLE
TOWARD MORNING AS MID LEVEL WARM AIR ADVECTION INCREASES
OVERNIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 303 PM CDT THU MAY 23 2013

FOR TONIGHT...SURFACE HIGH PRESSURE WILL PUSH OFF TO OUR SOUTHEAST AS
LOW LEVEL WINDS VEER TOWARD THE SOUTHEAST. A SUBSTANTIAL AMOUNTS OF
LOW LEVEL MOISTURE WILL BE ADVECTED NORTHWEST TONIGHT FROM WESTERN
KANSAS ANS EASTERN COLORADO INTO WESTERN NEBRASKA. SKIES TO BECOME
OVERCAST MOST AREAS BY DAYBREAK. REGARDING RAIN CHANCES...DELAYED
ONSET OF SHOWERS/ISOLATED TSTMS UNTIL AFTER 06Z FOR AREAS WEST OF
VTN THROUGH BBW. STEEP MID LEVEL LAPSE RATES WITH THE APPROACH OF A
DISTURBANCE FROM COLORADO WILL INCREASE SHOWER CHANCES. LOW
TEMPERATURES WILL RANGE FROM THE UPPER 40S TO MID 50S.

ON FRIDAY...PASSING DISTURBANCE TO BRING CHANCE POPS TO MUCH OF
FORECAST AREA IN THE MORNING WITH THE HIGHEST POPS 40-50 PERCENT
EAST OF HWY 83. BY EARLY AFTERNOON...ONLY SLIGHT CHANCE IN THE WEST.
GFS AND NAM INDICATED A MOSTLY SATURATED LAYER FROM SFC THROUGH
800MB. HAVE LOWERED TEMPERATURES AS MUCH AS 5 DEGREES TOWARD THE
COOLEST MET GUIDANCE FOR CENTRAL AND SOUTHEAST ZONES WITH HIGHS FROM
66 TO 69. FAR WEST TIER OF COUNTIES FCST TO REACH THE LOWER/MID 70S
AS CEILINGS LIFT AND PARTIAL LATE AFTERNOON CLEARING. ANOTHER MAIN
FORECAST CONCERN WILL BE POTENTIAL FOR STORM INITIATION ALONG STRONG
DIFFERENTIAL HEATING BOUNDARY NEAR A LINE FROM KBFF-KSNY-KITR. AREAS
75 MILES EAST AND WEST OF THIS LINE ARE AT RISK FOR SEVERE STORMS BY
LATE FRIDAY AFTERNOON/EARLY EVENING. THIS INCLUDES THE SOUTHEAST
PANHANDLE AND MUCH OF SWRN NEBR. RICH THETA-E ADVECTION INDICATED BY
NAM AND GFS INTO THIS REGION ALONG WITH SFC DEWPOINTS REACHING THE
MID/UPPER 50S W/BACKED LOW LEVEL WINDS SUSTAINED NEAR 20KTS. THIS
FAVORABLE FOR DISCRETE ROTATING STORMS.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 303 PM CDT THU MAY 23 2013

THE END OF THE WEEK IS DOMINATED BY TWO UPPER LEVEL LOW PRESSURE
SYSTEMS IN PLACE ALONG THE EASTERN AND WESTERN COASTS...WITH AN
AMPLIFIED RIDGE AXIS IN THE PLAINS REGION. THE RIDGE AXIS WILL
SLOWLY SHIFT EAST...PUTTING WESTERN NEBRASKA IN SOUTHWEST FLOW ALOFT
AND A RATHER UNSETTLED WEATHER PATTERN. THIS PATTERN WILL ALSO KEEP
TEMPERATURES WARM AND SOMEWHAT HUMID CONDITIONS AROUND THROUGH MOST
OF THE FORECAST PERIOD.

THE MAIN FORECAST CHALLENGE WILL BE THE POSSIBILITY FOR SEVERE
WEATHER...MAINLY FRIDAY NIGHT AND SATURDAY NIGHT. THE SOUTHWEST FLOW
WILL SETUP LEE SIDE TROUGHING IN EASTERN CO AND THE NE PANHANDLE.
SHORTWAVES EMBEDDED IN THE SOUTHWEST FLOW WILL MOVE OVER THE
PLAINS...HOWEVER THE PRIMARY AREA OF LIFT ASSOCIATED WITH MOST OF
THESE WAVES WILL BE CENTERED OVER THE ROCKIES. THE MAIN LIFTING
MECHANISM FOR THUNDERSTORM ACTIVITY IN THE HIGH PLAINS LOOKS TO BE
INSTABILITY BUILT UP BY DIURNAL HEATING.

THUNDERSTORMS...SOME SEVERE...MAY BE ONGOING AT THE BEGINNING OF THE
PERIOD ACROSS SOUTHWEST AND WESTERN NEBRASKA FRIDAY EVENING. THE
PRESENCE OF A 30-40KT LLJ WILL HELP MAINTAIN THIS ACTIVITY OVERNIGHT
AS IT VEERS OFF TO THE EAST. STEEP MID LEVEL LAPSE RATES AND AMPLE
MOISTURE WILL KEEP THUNDERSTORMS POSSIBLE...HOWEVER THE SEVERE
THREAT OVERNIGHT WILL BE LOW.

ATTENTION THEN TURNS TO SATURDAY AS SKIES BEGIN TO CLEAR OUT FROM
WEST TO EAST DURING THE MORNING AND AFTERNOON HOURS. THIS WILL BE
FAVORABLE FOR STRONG HEATING...WITH HIGHS PUSHING THE UPPER 80S FOR
MOST OF THE AREA BUT STILL COOLER IN OUR NORTHEAST ZONES. THE
HEATING WILL MAKE THE BOUNDARY LAYER VERY UNSTABLE WITH MLCAPE
VALUES EXCEEDING 2K J/KG...AND COUPLED WITH 30-40 KTS OF DEEP LAYER
SHEAR WILL PROMOTE AN ENVIRONMENT CONDUCIVE FOR SEVERE STORMS
BEGINNING LATE IN THE AFTERNOON. PRIMARY THREATS AT THIS TIME
LOOK TO BE LARGE HAIL AND DAMAGING WINDS. AGAIN...LLJ WILL
STRENGTHEN AFTER DARK AND HELP MAINTAIN THE THUNDERSTORM ACTIVITY AS
IT MOVES EAST.

STORM CHANCES WILL CONTINUE THROUGH THE EXTENDED PERIOD AS THE HIGH
PLAINS REMAINS IN A SOUTHWEST FLOW PATTERN. MODELS BEGIN TO DIVERGE
ON THEIR HANDLING OF THE LONGWAVE PATTERN TOWARD THE END OF THE
EXTENDED PERIOD WITH THE GFS EJECTING A TROUGH INTO THE NORTHERN
PLAINS...WITH THE 12Z EC DIGGING A TROUGH INTO THE RIO GRANDE
VALLEY. THIS WILL HAVE A BIG IMPACT ON PRECIP CHANCES FOR THE MIDDLE
OF NEXT WEEK GOING FORWARD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 613 PM CDT THU MAY 23 2013

A SURFACE TROUGH OF LOW PRESSURE WILL DEEPEN ACROSS THE NEBRASKA
PANHANDLE TONIGHT AND FRIDAY...LEADING TO STRONG SOUTHERLY WINDS
ACROSS WESTERN AND NORTH CENTRAL NEBRASKA. WIND SPEEDS TONIGHT
WILL RANGE FROM 10 TO 20 KTS TONIGHT...AND FROM 20 TO 30 KTS ON FRIDAY.
MOSTLY CLEAR SKIES EARLY THIS EVENING WILL BECOME OVERCAST
OVERNIGHT WITH BROKEN CLOUDINESS EXPECTED FRIDAY AFTERNOON. LIGHT
RAIN SHOWERS ARE POSSIBLE ACROSS SOUTHWESTERN NEBRASKA OVERNIGHT
TONIGHT AND MAY IMPACT THE KLBF TERMINAL AFTER 08Z. CIGS AT TEH
KLBF TERMINAL WILL RANGE FROM 1000 TO 4000 FT AGL WITH THE LOWEST
CIGS BETWEEN 08Z AND 15Z FRIDAY. FOR THE KVTN TERMINAL...CIGS WILL
RANGE FROM 1500 TO 3000 AGL OVER THE NEXT 24 HOURS.


&&

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

$$

UPDATE...CLB
SHORT TERM...ROBERG
LONG TERM...MARTIN
AVIATION...CLB