934
FXUS63 KLBF 122012
AFDLBF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
312 PM CDT MON MAY 12 2008
DISCUSSION
THE NAM12 CORRECTLY PREDICTED A TRIPLE PT FORMING ACROSS SWRN NEB
THIS AFTN. LAPS SFC INSTABILITY PARAMETERS ARE APPROACHING SVR LIMITS
WITH 1800 CAPE AND -6 LI AT 19Z. PROFILER WINDS HOWEVER SHOW MODEST
TO WEAK SHEAR SO THE PROGNOSIS FOR AN ISOLATED SVR STORM REMAINS
UNCERTAIN. THE NAM12 HAS BACKED OFF ON THE AMOUNT OF MOISTURE POOLING
BEHIND THE FRONT WHICH IS FCST TO MOVE QUICKLY EAST VS EARLIER RUNS.
THE BLENDED SOLNS OF THE GFS AND NAM12 INDICATED SCATTERED SHOWERS
AND THUNDERSTORMS TONIGHT WITH SHOWERS CONTINUING THROUGH TUESDAY
AFTERNOON. SPC CONTINUED THE 5 PERCENT OUTLOOK THIS EVENING FOR MOST
OF WESTERN AND NORTH CENTRAL NEBRASKA. THE COLD FRONT IS FORECAST BY
THE RUC TO DRIFT SLOWLY EAST THIS EVENING WITH LITTLE OR NO
CONVECTION FORMING ALONG OR AHEAD OF THE FRONT AND ALL THE RAIN
FALLING BEHIND THE FRONT. THE GFS AND NAM MODELS POINT TO
CONVECTION FORMING BEHIND THE FRONT ALSO.
FOR TUESDAY...AN H7 OPEN WAVE EXITS NEBRASKA AROUND 00Z. SKIES
SHOULD BEGIN TO CLEAR WEST TO EAST DURING THE AFTERNOON WITH ALL
AREAS MOSTLY CLEAR TUESDAY NIGHT. TEMPERATURE GUIDANCE INDICATES
SCATTERED FROST ALONG AND WEST OF HIGHWAY 83 EXCLUDING THE SRN
TIER COUNTIES IN SWRN NEB. ALSO MIN TEMPS MAY FLIRT WITH FROST IN
CUSTER COUNTY. THUS A FROST ADVISORY MAY BE NECESSARY LATE TUESDAY
NIGHT AND EARLY WEDNESDAY MORNING. WINDS REMAIN BREEZY TUESDAY
BEHIND THE FRONT AT LEAST THROUGH THE MORNING HOURS. NONE OF THE
GUIDANCE SUGGESTED WIND SPEEDS APPROACHING ADZY SPEEDS. THE BLENDED
GUIDANCE AND NAM12 2M MAX TEMPS PRODUCED HIGHS IN THE UPPER 50S.
THIS IS CONSISTENT WITH SCATTERED FROST BY WEDNESDAY MORNING. ALSO...
THE DRY AIR MOVING IN TUESDAY NIGHT IS NOT PARTICULARLY DRY WITH
PRECIPITABLE WATER FALLING TO 0.40 INCHES VERSUS 0.20 SUNDAY
MORNING WITH THE HARD FREEZE. RADIATION CONDITIONS ARE LESS THAN
IDEAL.
WEDNESDAY AND THURSDAY...TEMPERATURES SHOULD REBOUND IN THE UPPER
60S WEDNESDAY. CLOUDS WILL BE INCREASING THROUGHOUT THE DAY AND
SHOWERS MAY DEVELOP IN THE NORTHWEST DURING THE AFTN. THIS
DISTURBANCE WILL MOVE SOUTH THROUGH AN INCREASINGLY AMPLIFIED UPPER
LEVEL FLOW. THE BLENDED SOLNS OF THE GFS AND NAM12 SUGGEST THE SHOWER
ACTIVITY WILL CONTINUE THROUGH THURSDAY AFTN AS AN UPPER LEVEL LOW
DROPS NEARLY DUE SOUTH THROUGH THE UPPER MIDWEST AND H5 TEMPERATURES
FALL TO NEARLY -25C THURSDAY AFTN IN NEBRASKA. THE NAM12 SUGGESTED
NEGATIVE LIS THURSDAY AFTERNOON SO ISOLATED THUNDERSTORMS HAVE BEEN
ADDED TO THE FCST THURSDAY AFTERNOON. THE SHOWER ACTIVITY SHOULD
DIMINISH THURSDAY EVENING AND THE HPC GRIDS SUGGESTED CLEARING SKIES
BY FRIDAY MORNING. MEANWHILE...THE 2M NAM12 TEMPERATURES SUGGESTED
HIGHS IN THE LOWER 60S THURSDAY WITH UPPER 50S IN THE PANHANDLE. THUS
LATER FCSTS WILL HAVE TO MONITOR MIN TEMPS FRIDAY MORNING AS THE
CURRENT GUIDANCE INDICATES LOWER 40S FOR LOWS BUT IF SKIES CLEAR OUT
SCATTERED FROST COULD DEVELOP.
FRIDAY THROUGH MONDAY...A GRADUAL WARMING TREND DEVELOPS. A MASSIVE
RIDGE WILL FORM ACROSS THE WRN U.S. CENTERED ROUGHLY OVER NRN CA
WHERE A RECORD HEAT WAVE IS EXPECTED TO DEVELOP. THIS WARM AIR
WILL ATTEMPT TO SPREAD EAST BUT A DEEPENING TROUGH IN THE UPPER
MIDWEST WILL SET UP A SHARP EAST WEST TEMPERATURE GRADIENT ACROSS THE
WRN HIGH PLAINS. THE FCST IS DRY AND TEMPERATURES ARE A MIDDLE GROUND
AS THE GUIDANCE HAS BEEN WOBBLING WARM AND COOL WITH THE MODELS
WOBBLING THE DEEP TROF WEST AND THEN EAST.
AVIATION
VFR CONDITIONS WILL CONTINUE THROUGH 03Z. THEN AS TOP DOWN
MOISTENING OCCURS AND SHOWERS DEVELOP SOUTHEAST ACROSS WESTERN
NEBRASKA WITH MVFR CONDITIONS TO DEVELOP BEYOND 06Z. MORE EXTENSIVE
LOW CEILINGS WILL OCCUR ACROSS THE SOUTHWEST THROUGH 15Z TO INCLUDE
THE KLBF TERMINAL AND MORE LOCALIZED AT KVTN BETWEEN 10Z AND 14Z.
ISOLATED THUNDERSTORMS WILL BE POSSIBLE INTO THE EVENING WHERE THE
HIGH BASED STORMS COULD GENERATE STRONG WINDS GUSTS WHILE MOVING
EAST SOUTHEAST. AFTER 15Z TUESDAY VFR CONDITIONS WILL RETURN.
LBF WATCHES/WARNINGS/ADVISORIES
NONE.
CDC/TLK
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