900 FXUS63 KOAX 172031 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 331 PM CDT Thu Jun 17 2021 ...Updated Forecast Discussion Tonight through Thursday... .DISCUSSION... Issued at 327 PM CDT Thu Jun 17 2021 Forecast Summary: A more unsettled weather pattern is setting up for the next couple of weeks, so we'll see off-and-on rain chances through the end of June at least. In the shorter term, hot temperatures remain in the forecast through the weekend (but not as hot as today), before a drastic swing to below-normal temperatures to start next week. A gradual rebound in temperatures will follow. Tonight through Sunday: Extremely hot temperatures developed this afternoon under mid level height and temperature ridge. Many locations had hit 100 degrees before 3 PM, with heat indices near 105. A weak frontal boundary in northeast Nebraska separated upper 80s temps to the north and the hot air to the south. South to southwest low level winds were adding compressional warming component south of front as well, so we should see some potential 105 readings before daytime heating ends. A few showers and thunderstorms tracked across far northeast Nebraska, tied to shortwave riding east into southern Minnesota. Those have moved east, leaving surface convergence along frontal zone behind. Satellite loops were not impressive in regards to further development this afternoon, showing few clouds in the area under very warm temperatures aloft. Thus will maintain only a small chance for thunderstorms in our far north into the evening, but main show looks to come later tonight. Another weak shortwave inducing isentropic upglide into western and north central Nebraska overnight will tap elevated instability to produce storms there late this evening. Storms will move east near and north of frontal zone into northeast Nebraska after midnight. Given warm mid level temperatures, large hail will be tough to get, but damaging downdraft winds will be possible. Convection should push frontal boundary southward during the day, reaching southeast Nebraska in the afternoon. Chance for thunderstorms will accompany the front, but severe threat should wane during the morning before uptick again late afternoon and evening. Pooling moisture along front will contribute to high SBCAPE over 3000 J/kg, with 40kt of bulk shear helping potential for severe. Best estimate now says storms will fire along or just north of the Iowa/Missouri border and develop westward into southeast Nebraska during the evening. Again, damaging downdraft winds are possible. After this activity diminishes or pushes east late Friday night, most of Saturday looks dry. Then another shortwave is scheduled into the region, dragging frontal boundary northward again as strong theta-e advection develops in eastern Nebraska. More elevated convection should result Saturday night with this advancing warm front. Then trailing cold front during the day Sunday will be a focus for thunderstorms then. Exact timing and thus potential for severe on Sunday will have to be worked out in future updates. But with temperatures in the 90s and returning low level moisture, there will certainly be a risk of severe. Monday through Thursday: Much cooler air will follow Sunday's system as mid level flow becomes northwesterly and 850 temps drop some 15C from the weekend into Monday night. Thus highs only in the 70s are likely Monday before a gradual increase through the week with rising heights regime. A few chances for thunderstorms will accompany severe shortwaves dropping through the flow, but model differences in timing are too great to nail down best rain chances. So our forecast will show slight chances for thunderstorms for at least Monday into Tuesday, and then again Thursday. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1223 PM CDT Thu Jun 17 2021 Gusty south to southwest winds will continue through the afternoon ahead of a cold front currently draped across northeast Nebraska. As the front slides south later this afternoon and evening, a few showers and perhaps some thunderstorms could erupt along it. Strong capping will likely inhibit coverage and intensity of any storms that manage to form, but KOFK could be affected through 00Z. Otherwise chances for convection are low for this TAF cycle. Winds will die down to near or below 12kt this evening, then turn northwest to northeast later this evening and continue through Friday morning. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory until 8 PM CDT this evening for NEZ015-030>034- 042>045-050>053-065>068-078-088>093. IA...Heat Advisory until 8 PM CDT this evening for IAZ043-055-056-069- 079-080-090-091. && $$ DISCUSSION...Dergan AVIATION...Dergan