823 FXUS63 KOAX 081128 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 628 AM CDT Wed Jul 8 2020 ...Updated Aviation Forecast Discussion... .DISCUSSION... Issued at 336 AM CDT Wed Jul 8 2020 .Summary: Hot and humid today with heat indices approaching 100-102 in some areas. A chance for a few strong to severe storms from late afternoon through this evening. Strong to potentially severe storms will also be possible on Thursday afternoon and night, and Friday night into Saturday morning. .Today and Tonight: A weak mid-level impulse over eastern UT/western CO early this morning will continue east-northeast, reaching the central High Plains by this afternoon. In the low levels, a surface front will stretch from eastern SD through north-central NE into northeast CO later today. Ahead of the front, the combination of afternoon temperatures in the lower to mid 90s and dewpoints in the upper 60s to lower 70s will result in heat indices reaching 100-102 in some locations. Gusty south winds are also expected. By late afternoon/early evening, frontal convergence coupled with increased forcing for ascent ahead of the approaching mid-level disturbance will foster a broken band of thunderstorms to the immediate northwest of our area. While deep-layer shear will remain relatively weak (i.e. aob 25 kt), the high theta-e boundary layer surmounted by a steep-lapse-rate plume will yield MLCAPE values of 2500-3500 J/kg. As such, the incipient storms should quickly intensify and grow upscale into a forward-propagating MCS. Recent convection-allowing model simulated reflectivity forecasts suggest a south-southeast track of the MCS with the greatest risk for locally damaging winds being generally west of a Norfolk to Lincoln to Beatrice line. Locally heavy rainfall and isolated occurrences of hail are also possible. Given the anticipated MCS track, measurable precipitation chances tonight decrease with eastward extent over far eastern NE into southwest IA. .Thursday and Thursday night: Little in the way of forcing for ascent is forecast on Thursday. Additionally, the disruption of the low-level mass fields by the Wednesday night MCS, casts considerable uncertainty on the timing and location of any daytime thunderstorm development. Furthermore, the degree of air mass stability remains in question. Highs should be cooler than that on Wednesday and in the mid to upper 80s. Another weak disturbance is forecast to move into western Nebraska on Thursday evening, supporting thunderstorm development over the western part of the state. That activity is expected to move east-southeast, eventually reaching our area later Thursday night. While some severe-weather risk will exist from Thursday afternoon into Thursday night, details remain elusive due to the above- mentioned uncertainties. .Friday: Temporary mid-level height rises should translate to dry and warmer conditions with highs in the upper 80s to lower 90s. .Friday night and Saturday: Amidst a belt of 30-40 kt northwest flow at 500 mb, a shortwave trough is forecast to translate from SD through the mid-MO Valley Friday night into Saturday morning. Forcing for ascent attendant to that feature is expected to give rise to an MCS over western SD/northwest NE on Friday evening. That system would then track southeast, likely reaching our area late Friday night into Saturday morning. Details regarding the degree of instability remain unclear, especially given the time of day the system is expected to move through. Nonetheless, vertical shear should be unseasonably strong and supportive of an organized MCS, given sufficient instability. Precipitation chance should decrease by Saturday afternoon with highs mainly in the mid to upper 80s. .Sunday through Tuesday: Mid-level troughing along and east of the MS Valley on Sunday will shift east ahead of a broadening trough over western and central Canada into the northern tier of states. In the low levels, a surface high initially over the mid-MO Valley will shift east ahead of a surface front which could settle into the area by about the middle of next week. Highs will be mainly in the mid 80s to lower 90s with generally dry conditions early next week. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 621 AM CDT Wed Jul 8 2020 Deteriorating conditions are expected later this evening in association with a convective complex moving southward through eastern NE. Expect line of TSRA to form over north-central NE by late afternoon the gradually push southeast during the evening hours. By the time storms get to the terminals the primary hazard will be strong wind gusts. Storms should be clear of the area shortly after midnight. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Mead AVIATION...DEE