Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 190446 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1146 PM CDT Fri Aug 18 2017 .SHORT TERM...(Tonight through Monday) Issued at 225 PM CDT Fri Aug 18 2017 Storms have developed this afternoon, in northwest MO, moving southeast away from our area. There is another ares of towering cumulus in extreme northeast NE, however Highres HRRR/Rap don`t want to develop this area at all. Thus will keep the late afternoon forecast dry. Then beautiful, typical mid summer weather tonight into Saturday with high pressure overhead. Lows tonight in the upper 50s to lower 60s. Highs Saturday in the mid 80s to lower 90s. Storms develop Saturday afternoon across the central part of NE, as a weak wave moves out of the central Rockies. The greatest chance of storms moves into especially eastern NE Saturday evening, and then across southeast NE and eventually northeast KS a convective complex slides east southeast. Sunday could see a small chance of showers/storms southeastern part of the forecast area in the morning as system departs to our southeast. Unsure of additional convective development Sunday afternoon. The Nam remains generally dry, but the GFS/EC/Canadian all hint at another very weak upper wave meandering through the mid MO valley region that could spark additional isolated afternoon storms, especially along/ south of I80. Sunday is another warm day with highs in the upper 90s to lower 90s. Dewpoints are forecast to begin nudging back into the upper 60s to lower 70s, which results in afternoon heat index values in the lower to mid 90s for a few hours in the afternoon. Eclipse Weather Outlook With a relatively weak, fast zonal flow aloft, models typically have a hard time discerning weak perturbations that move out of the Rockies. The bulk of the models are suggesting that there remains a small chance of thunderstorm development Sunday night somewhere on the Plains, which includes portions of NE/KS. However, the models remain consistently inconsistent with previous runs, with the EC showing possible development further north of I80, but other models developing spotty convection along and south. Thus, model consensus blends still give us 20-40% chance of thunderstorms Sunday night, but the threat may diminish through Monday morning. Questions remain about associated cloud cover and how much clearing will take place by eclipse totality time at 1 pm. Nam model is the most optimistic in clearing the clouds, but GFS and EC both remain pretty pessimistic for especially southeast NE. Even if the lower convective clouds clear Monday morning, there may still be quite a bit mid and high clouds streaming in from the southwest which may lead to more fuzzy than clear views unfortunately. As suggested yesterday, defining cloud coverage in a less than clean weather pattern for a 5 minute window remains a significant challenge. Have knocked down model blend max forecast temps 2-3 degrees due to cooling effects of the eclipse. We should still reach mid 80s to low 90s temps, and again, when combined with typical summer dewpoints, afternoon heat index values post eclipse reach the lower to mid 90s. .LONG TERM...(Monday night through Friday) Issued at 225 PM CDT Fri Aug 18 2017 Models bring a cold front into the region Monday night, thus have 40-70% Pops Monday night, with a lingering chance of shower/storms south of I80 Tuesday morning. Tuesday night and Wednesday look dry and pleasant. Highs Wednesday in the lower 80s. There is a weak wave moving into the area on northwest flow Wednesday night which could bring small pops to the area. Forecast confidence beyond then is somewhat low, but generally dry. && .AVIATION...
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(For the 06Z TAFS through 06Z Saturday night) Issued at 1144 PM CDT Fri Aug 18 2017 Surface high pressure over eastern Nebraska will maintain clear skies and light winds at TAF sites through Saturday morning. As the high slides east during the afternoon, southeast winds near 10kt are forecast, with increasing mid and high level clouds. There is a chance for thunderstorms Saturday night, but should hold off until after this TAF cycle.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...DeWald LONG TERM...DeWald AVIATION...Dergan

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