Expires:No;;840829 FXUS63 KOAX 081117 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 617 AM CDT Wed May 8 2024 .KEY MESSAGES... - Marginal risk of severe thunderstorms today and this evening in northeast Nebraska and western Iowa - Some storms today and this evening could be strong to severe, capable of producing hail, damaging winds and funnel clouds - Forecast for Friday through early Sunday is mostly dry. Chance of showers and thunderstorms returns Sunday afternoon and lingers into early next week. - Warmer temperatures expected Sunday into Tuesday. && .DISCUSSION... Issued at 439 AM CDT Wed May 8 2024 .Today... A band of showers continues to move northeast across the forecast area this morning, associated with moist isentropic lift along the 305-310K, prompted by increasing large scale ascent in advance of H5 closed low digging southward into the central plains. Drier air below 5K AGL is limiting measurable precipitation. Better focus moves east of forecast area by mid- morning, thus expect a lull in precipitation by then. Upper level low begins to move east along the Nebraska-South Dakota border by mid-day, sharpening the large scale wind field, with bulk shear values of 40-70kt by midday. Lapse rates will increase as cold core and vort lobe from upper low moves across the area. In tandem, low level theta-e increases,which will lead to SB/MUCAPE near 1000 J/Kg northeast Nebraska and western Iowa, and about 1200 J/kg extreme southeast Nebraska. An inverted trough will be oriented from southwest Iowa, across extreme northeast Nebraska into southeast South Dakota, providing adequate surface convergence to allow for scattered thunderstorm development. Given proximity to upper low, increased stretching and low-level shear, present an environment conducive for funnels and/or possibly a tornado or two, especially storms interacting with inverted trough across extreme northeast Nebraska and northwest Iowa. Further south, across southeast Nebraska, proximity to main surface low could aid in low level convergence for storms, but tornado or funnel threat in this area is not expected. Threat of severe weather will diminish by early evening as vort lobe moves east of the area, leading to subsidence across the region. A few more showers could develop during the overnight hours as another disturbances ripples through broad cyclonic flow aloft. Temperatures today will be similar to those seen yesterday. Overnight lows will be in the 45 to 50 degree range. .Thursday... Area remains on the cyclonic shear side of broad, latitudinal trough that stretches from North Atlantic to western U.S. Mid-level isentropic convergence will help to sustain band of showers and possibly isolated thunderstorms, especially during the daytime when diabatic effects will aid in destabilization. Precipitation coverage and chances will wane Thursday evening, as upper trough axis moves south and east of the area, and increases large scale subsidence. Clouds, evaporative cooling and low level cold advection will keep temperatures about 5 to 10 degrees cooler, with highs only in the 60s. Lows will be in the 40s. .Friday through Saturday... Large scale subsidence will keep precipitation chances slim, and will allow for temperatures to rebound into the 70s for highs. Sharpening trough across the eastern U.S. pushes a backdoor cold front into the area for Saturday. In cooling associated would affect Iowa moreso than Nebraska, with downslope warming mitigated low level cool air advection. .Sunday through Tuesday... Temperatures will increase as upper level ridging builds, with high temperatures climbing into the 80s. An open H5 wave will progress from the 4-corners area across the southern plains Sunday and Monday, and bring another chance of showers and thunderstorms. The surface pattern doesn't suggest a threat of severe weather, as better mass responsive will be south of the area. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 613 AM CDT Wed May 8 2024 Light showers this morning have been producing gusts of 30 to 45 mph or more in around and just east of KOMA, with shower activity expected to decrease through the morning. VFR conditions will last through the period with westerly to northwesterly winds becoming the norm by early this evening. A few showers and storms will be possible (25% chance) near KOFK from 20-01z, but were not included in the TAF. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Fortin AVIATION...Petersen