921 FXUS63 KLBF 281727 AAA AFDLBF Area Forecast Discussion...UPDATED National Weather Service North Platte NE 1227 PM CDT Wed Jun 28 2017 .SHORT TERM...(Today and tonight) Issued at 412 AM CDT Wed Jun 28 2017 The main forecast concerns revolve around storm potential again this evening and overnight. There is potential for strong to severe thunderstorms, mainly after 6 PM CDT. SPC Day 1 Outlook has the majority of the local forecast area in a MRGL risk area with a SLGT risk area south of a line roughly from Big Springs to North Platte. Latest IR satellite imagery shows skies clearing across much of western NEB with ongoing convection leaving eastern NEB. Latest water vapor imagery shows the main impulse/shortwave trough over western NEB tracking eastward, otherwise an upper level trough extends southwest into northern CA with the closed low located over central Alberta and western Saskatchewan. The upper level trough will continue to revolve eastward and move into the Northern Rockies today with the closed low moving more into Saskatchewan while zonal flow prevails in the mid-levels aloft overhead. A weak cold front has advanced through much of the local forecast area associated with a surface low in the eastern Dakotas that has a central pressure near 998 mb. The front will clear the remainder of local forecast area during the early morning and is expected to lie south and east of the forecast area in the afternoon from west central KS to eastern NEB. Surface dew points will range from the upper 40s in far western NEB to mid 50s towards central NEB this afternoon. Thermodynamic profiles should be conducive for instability ranging from weak (MLCAPE less than 1000 J/kg) to moderate instability (MLCAPE exceeding 1000 J/kg) in portions of southwest NEB to north central NEB. Less instability elsewhere in the local forecast area. NAM in comparison with the GFS and RAP is the most bullish in the quantity and distribution of moisture, and current thinking is the latter are too low. Otherwise, lapse rates are supportive with 700-500 and 850-500 exceeding 8 C/km in much of the High Plains and southwest NEB. Current thinking is main threats will be hail and damaging wind with a lower threat for tornadoes in comparison to yesterday. Current thinking is convection will initiate across the High Plains and move into and across western NEB this evening into the small hours. .LONG TERM...(Thursday through Tuesday) Issued at 412 AM CDT Wed Jun 28 2017 As a shortwave trough progresses east across the Dakotas and Nebraska Thursday, it will drive a cold front southeast across the region. The front should be mostly southeast of our area by peak heating, and this would be where the higher potential for stronger storms would be. The front has slowed a bit from the previous forecast and will have to watch and see if front slows anymore. SPC has shifted the Thursday, Day 2, severe threat a bit farther west into the eastern portions of our area. This is likely to account for a possible slower frontal passage and will continue to monitor. There is some MUCAPE (elevated) post frontal which lingers into Thursday evening, so a strong storm or two is possible even behind the front due to good wind shear aloft and lift associated with the shortwave disturbance. Flow turns northwest aloft Friday through Saturday, with drier mild air filtering into the area behind Thursday's cold front. Gusty northwest winds are expected Friday with good mixing as H850mb winds of 20 to 25 kts mix to the surface. A pleasant first half of the weekend with highs in the upper 70s to mid 80s Saturday with light winds. The next shortwave will dive southeast across the area Saturday night and Sunday. This will strengthen a leeward trough Saturday night with a south to southeast wind developing. This will rapidly draw warm moist air back north into the area Sunday, resulting in possible strong storms and an MCS late Sunday afternoon and Sunday night. Upper level ridging begins to expand north and east across the area first of next week. As of now looks mainly dry and on the warmer side with highs in the mid 80s to lower 90s. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1227 PM CDT Wed Jun 28 2017 The on-going jet streak across Nrn Colo and daytime heating appear to be the genesis for front range thunderstorm development this afternoon which should move east this evening and affect Swrn Neb overnight. Isolated thunderstorms are possible Thursday along and south of I-80. There is also a disturbance moving across the Tetons which should spark storms off the Big Horns this afternoon. This appears to grow weakly upscale this evening across Wrn SD which could affect Nrn Neb overnight. Lastly, some level of storm development is expected on the Laramie Range which could also move east and affect the Sandhills overnight. Thunderstorms chances Thursday are in place, mainly north of Interstate 80, with the best chance across Ncntl Neb east of KVTN. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...ET LONG TERM...Taylor AVIATION...CDC