346 FXUS63 KOAX 020352 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1052 PM CDT Sun Jun 1 2025 .KEY MESSAGES... - Canadian wildfire smoke will continue its presence over the region through today before clearing out by tomorrow. - Abnormally warm temperatures, with readings in the mid 80s to lower 90s, will be common across the forecast area through Monday. - Shower and thunderstorm chances increases late Monday into Tuesday with the potential for severe weather and heavy rainfall. && .DISCUSSION... Issued at 1228 PM CDT Sun Jun 1 2025 Current regional analysis reveals high pressure no dominating over the Northern Plains, translating to quiet, but rather warm conditions for the Mid-Missouri River Valley. Temperatures for Eastern Nebraska and Southwestern Iowa this afternoon will range from the middle 80s, with some locations reaching 90F, a good 5-10 degrees above normal for the beginning of June. There will still be some Canadian wildfire smoke to contend with through this afternoon and evening, but conditions relating to this will begin to improve over the next several hours. Some of our regional weather stations have reporting reduced visibilities due to haze through much of the morning, likely a reflection of the presence of this smoke at the surface. Any lingering smoke may lead to some minor health concerns and bodily irritation. The good news is that once our diurnal mixing takes place, particle concentrations at the surface should begin to defuse, improving both visibility concerns and air quality. .MONDAY AND TUESDAY... The transient ridge will still be overhead going into the start of next week, resulting in another unseasonably warm day, with readings in the upper 80s to lower 90s, with perhaps a few place flirting with around 95F. However, this period of of quiet and warm weather will quickly come to end with the approach of two separate weather systems. The first will help bring in remnant moisture from Tropical Storm Alvin (which is also causing rare early June rainfall over the deserts of Arizona and Southeast California), while the second helps bring in cooler air aloft ans an associated surface cold front. This will set the stage for what will become an active period starting as early Monday afternoon. The combined moisture (PWATs around the 99th percentile) and daytime heating will prime the atmosphere for the potential for some potent convection, with hi-res model guidance indicating SBCAPE values exceeding 2500-3000 J/kg. The broad ascent of the converging troughs and the surface lift from the cold front are the other pieces that will promote convective initiation and support. Sufficient wind shear will also aid in convective life- spans while also increasing the threat for some severe cells capable of large hail and damaging winds. Most of the moisture will be elevated, so a relatively dry sub-cloud layer will support strong downbursts capable of strong winds even sub- severe storms. The timing of everything does not indicate a prolonged severe event, with the best chances of seeing some severe reports being focused mostly over the northwestern portions of the forecast area Monday evening, where the SPC has highlighted a slight risk of severe thunderstorms. That does not exclude the remainder of Nebraska and parts of Iowa from seeing stronger convection, but once storms lose the heating of the day, the severe potential will be lower for the areas mentioned above. The tornado threat is very low at this time as low-level shear appears to be fairly weak, but an isolated spin-up cannot be completely ruled out. Another concern will be the potential for heavy rainfall that could lead to at least some isolated flooding concerns. With the ample moisture in place, any showers and storms will be efficient rain makers which could result in quick, heavy accumulations. WPC does have part of our area (mostly Northeast Nebraska) highlighted under a slight risk for flash flooding for Monday, so this will have to be something monitored as well going forward. Lingering showers and perhaps a few rumbles of thunder will be around once again on Tuesday which will add to accumulations for some areas. When all is said and done, it looks like anywhere from 1-2", with locally heavier amounts, may be the most common totals we see from this event. Temperatures will also be noticeably cooler Tuesday thanks to the cold front and associated rainfall, with readings from the middle 60s to lower 70s, a 20-25 degree day-to-day difference compared to Monday. .LONGER TERM... The overall pattern becomes more zonal in the wake of the early week active period, promoting warmer temperatures and relatively calmer conditions. Some subtle shortwaves may traverse the region throughout the week which could spark a few more instance of showers and thunderstorms, but more certainty will come into focus in regards to further precip chances in the coming days. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1049 PM CDT Sun Jun 1 2025 VFR conditions should continue through the majority of the TAF period, with southerly winds and gusts increasing around mid- morning before topping out during the mid-afternoon at around 25 kts. Storms are still on track to move through, and should arrive to KOFK at 03z, and at KOMA/KLNK during the overnight hours. Expect conditions to dip into the MVFR territory during thunderstorms and potentially some smoke being mixed down behind the incoming wind shift. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...RW AVIATION...Petersen