000 FXUS63 KLBF 032002 AFDLBF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 303 PM CDT SUN MAY 3 2009 ...FORECAST CHALLENGE IS PRECIPITATION CHANCES IN THE NEAR TERM AND EXTENDED... .SYNOPSIS... H5 HAND ANALYSIS THIS MORNING INDICATING SPLIT FLOW ACROSS THE CONUS...WITH A NRN STREAM ACROSS THE GREAT LAKES AND NEW ENGLAND...AND THE SRN STREAM EXTENDING FROM CA INTO THE DEEP SOUTH. RIDGING EXTENDED NORTH ALONG THE ROCKIES FROM MT INTO ALASKA...WITH A DEEP CLOSED LOW AND TROUGH EXTENDING FROM HUDSON BAY SOUTH INTO THE NRN GREAT LAKES. FURTHER SOUTH...A ZONAL PATTERN WAS NOTED...WITH A SHORTWAVE TROUGH EXTENDING FROM THE OZARKS SOUTH TO THE LA COAST. A WEAK SHORTWAVE WAS NOTED OVER NERN COLORADO AND IS RESPONSIBLE FOR THE PRECIPITATION OVER SWRN AND CENTRAL NEBRASKA TDY. TEMPERATURES AT 2 PM CDT RANGED FROM 50 AT NORTH PLATTE AND OGALLALA...TO 64 AT VALENTINE. && .DISCUSSION... .NEAR TERM...TONIGHT THROUGH WEDNESDAY NIGHT. MAIN FORECASTING CHALLENGE LIES WITH PRECIPITATION CHANCES FOR THIS EVENING...MONDAY AND TUESDAY. FOR TONIGHT...BEEN FOLLOWING ONGOING PRECIPITATION THIS AFTERNOON AND THE NAM 305K ISENTROPIC SURFACE SEEMS TO MIRROR ONGOING PRECIPITATION FAIRLY WELL THIS AFTERNOON. THE BEST LIFT THROUGH 00Z THIS EVENING CONTINUES TO BE FOCUSED ALONG THE INTERSTATE 80 CORRIDOR AS WELL AS SOUTHWESTERN AREAS AND SOUTHERN PORTIONS OF CUSTER COUNTY. LOOKING AT THIS SURFACE...WEAK ISENTROPIC LIFT WILL TRANSITION EAST FROM THE SWRN SANDHILLS INTO SOUTHWESTERN AND PORTIONS OF CENTRAL NEBRASKA THROUGH 00Z...ENDING MID EVENING. WILL CONTINUE TO MENTION PRECIPITATION ALONG AND SOUTH OF A LINE FROM WESTERVILLE TO ANTIOCH. AFTER MIDNIGHT...PARTLY TO MOSTLY CLOUDY SKIES ARE EXPECTED TO DEVELOP. HOWEVER CANNOT RULE OUT SOME PATCHY FOG SOUTH OF THE PLATTE RIVER DUE TO A COMBINATION OF CLEARING SKIES...WET GROUND CONDITIONS AND LIGHT WINDS. ON MONDAY...A DECENT SHORTWAVE TROUGH WILL TRAVERSE MT AND WYOMING...EMERGING ACROSS THE WRN DAKOTAS MONDAY AFTERNOON. AS THIS FEATURE APPROACHES...A SURFACE TROUGH WILL DEEPEN ACROSS THE NEBR PANHANDLE AND WESTERN DAKOTAS. THE SURFACE TROF WILL SERVE AS THE FOCUS FOR THUNDERSTORM DEVELOPMENT MONDAY AFTERNOON AND EVENING...AIDED BY AN APPROACHING UPPER LEVEL TROUGH. SURFACE HEATING AND A WEAK CAPPED ENVIRONMENT WILL ALLOW STORMS TO INITIATE EARLY DURING THE AFTERNOON HOURS. THOUGH SHEAR IS FAVORABLE FOR SOME STRONG TO SEVERE THUNDERSTORMS...MEAGER CAPES AT OR BELOW 700J/KG...WILL KEEP THE SEVERE POTENTIAL IN CHECK. ANY THREAT FOR STRONG TO SEVERE THUNDERSTORMS WOULD FAVOR NORTHERN AREAS...AS THEY ARE IN THE CLOSEST PROXIMITY TO THE UPPER LEVEL TROUGH AND HIGHEST CAPES. LATER IN THE EVENING...THE SURFACE TROUGH WILL STALL ACROSS THE WESTERN FORECAST AREA...SERVING AS THE FOCUS FOR THUNDERSTORM DEVELOPMENT TUESDAY AFTERNOON. TUESDAY AND WEDNESDAY...TUESDAY AFTERNOON...THUNDERSTORMS WILL FIRE ONCE AGAIN ALONG THE BEFORE MENTIONED SURFACE TROUGH. SEVERE POTENTIAL IS BETTER ON TUESDAY IN COMPARISON TO MONDAY...AS CAPES ALONG THE SURFACE TROUGH TOP 1000 J/KG AND DEEP LAYER SHEAR IS ON THE ORDER OF 40-50 KTS. CONTINUE TO AGREE WITH SPCS ASSESSMENT FOR SEVERE TSRAS WELL SOUTH OF THE AREA IN OK AND TX...WHERE CAPES TOP THE 3000J/KG MARK. THE SURFACE TROUGH WILL CLEAR THE CWA BY 12Z WEDNESDAY...ALLOWING ABUNDANT SUN AND DRY CONDS TO DEVELOP ACROSS THE AREA. WIDESPREAD 70S ARE EXPECTED. .LONG TERM...THURSDAY THROUGH THROUGH SUNDAY. LOW AMPLITUDE UPPER LEVEL FLOW WILL CONTINUE THROUGH THE END OF THE WORK WEEK AND INTO THE FIRST HALF OF THE WEEKEND...MAKING FOR A VERY DIFFICULT PRECIPITATION FORECAST. PRECIPITATION CHANCES WILL BE HIGHLY DEPENDENT ON THE TIMING AND LOCATION OF SHORTWAVES WITHIN THE MEAN FLOW...WHICH IS VERY DIFFICULT WITH THIS TYPE OF FLOW REGIME. USUALLY WOULD FAVOR A DRY FCST IN THIS SCENARIO...BUT A COLD FRONTAL PASSAGE LATE THURSDAY INTO THURSDAY NIGHT...AT LEAST WARRANTS SLIGHT CHANCE POPS FOR THESE PERIODS. INTO THE WEEKEND...BOTH THE GFS AND EURO SOLUTIONS ARE INDICATING A LOW AMPLITUDE RIDGE BUILDING ACROSS THE CENTRAL CONUS SATURDAY...WITH A TROUGH ON ITS HEELS SATURDAY NIGHT/SUNDAY. HAVE INTRODUCED POPS ACROSS THE CENTRAL AND NORTHERN AREAS FOR SATURDAY NIGHT AND SUNDAY BASED ON THE DEGREE OF MID LEVEL WARM AIR ADVECTION AND THE PRESENCE OF A DECENT MID LEVEL CLOSED SYSTEM LIFTING ACROSS THE DAKOTAS. HAVE CHOSEN TO FOLLOW NATIONAL GUIDANCE FAVORING THE SLOWER EURO SOLUTION...AND UNDERCUT POPS 5 TO 10 PERCENT BASED ON THE TIMING DISAGREEMENTS BETWEEN SOLUTIONS. && .AVIATION... SHOWERS CONTINUE TO IMPACT SW NEB LATE THIS AFTN AND INTO THE EVENING AS THE UPPER LEVEL WAVE CRAWLS ACROSS THE AREA. SHOWERS ARE EXPECTED TO END THIS EVENING AS WAVE SLIDES TO THE EAST...HOWEVER RESIDUAL MOISTURE TO AID IN DEVELOPING OF FOG AND LOW CIGS EARLY IN THE MORNING AS TEMP COOLS. FURTHER N AND AWAY FROM THE SHOWERS...SITE KVTN...VFR WITH HIGH CLOUDS CAN BE EXPECTED. TOMORROW MORNING SOUTH WINDS SLOWLY INCREASE AHEAD OF NEXT TROF...TO 10 TO 20 KTS. THIS WILL HELP MIX OUT ANY IFR AND MVFR CONDITIONS THAT DEVELOP. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE $$ .SHORT AND LONG TERM...BUTTLER .AVIATION...MASEK