270 FXUS63 KOAX 231119 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 619 AM CDT Mon Aug 23 2021 ...Updated for 12Z Aviation Forecast Discussion... .DISCUSSION... Issued at 400 AM CDT Mon Aug 23 2021 At 4 AM, skies were mostly cloudy over the region thanks to a thunderstorm complex along the NE/KS border that was riding the nose of the LLJ. These storms could produce some light rain south of Lincoln through around 9 AM, but in general the environment looks less favorable for storm maintenance in southeast Nebraska. Aside from that, winds were light and it was a relatively muggy morning across the Missouri River Basin (dewpoints in the mid to upper 70s). Muggy with Lingering Storm Chances Today: The synoptic pattern today will feature an upper level ridge centered over Texas and laminar flow from southwest to northeast over the Northern Plains (between 700 mb and 200 mb). There are some indicators of a weak wave around 700 mb that may lift north towards our region this afternoon. Otherwise, the main forcing mechanism for thunderstorm activity today looks to be a rather diffuse frontal boundary draped from north central Nebraska to northern Iowa. Surface dewpoints in the lower 70s and 700-500 mb lapse rates around 7.5 C/km should contribute to ample MLCAPE (~3000 j/kg) along the frontal boundary by this afternoon. Toss in diurnal mixing, and it looks like we could see increasing thunderstorm activity north of Interstate 80 between 1 PM and 4 PM today. CAMs generally support this conclusion, so forecaster confidence in storm development is moderate. Shear profiles may allow storms to be briefly supercellular, but with time any activity should become outflow dominate. With this in mind, the main threats look to be hail large enough to damage cars and winds capable of downing trees or power lines today. Another concern today will be the return of the heat, especially south of the frontal boundary where storm chances will be nil. Our going forecast suggests heat indicies of 98 to 104 degrees along and south of Interstate 80 between Noon and 6 PM. So it will feel pretty muggy out there today in the Lincoln and Omaha Metros. No Heat Advisory was issued for today as peak heat indicies look to be 1 to 3 degrees below the standard threshold of 105 degrees. Tonight and Tuesday: A second weak wave near 700 could bring a couple isolated showers or thunderstorms to the region tonight, though confidence in precipitation is low. Then we can expect another warm and muggy day Tuesday with our region in the warm sector ahead of any advancing cold front. By Tuesday afternoon the front may be approaching our region, and thunderstorm chances will return. Highest storm chances of around 20-35 percent are expected Thursday evening along the Interstate 80 Corridor. Temperatures on Tuesday should flirt with Heat Advisory criteria again, with peak heat indicies of 100 to 106 along and south of Interstate 80. Will reevaluate the need for a Heat Advisory on later shifts, but for now the chance of a Heat Advisory is around 60 percent. Midweek into the Weekend: The weather pattern over the U.S. doesn't change much during this period. Ensembles suggest the upper level ridge over Texas today will move little, just shifting towards the Southeast U.S. Meanwhile the parade of weak shortwaves through the northern tier of the U.S. looks like it will continue. A pattern like this places us on the southern edge of the best rain chances, and on the northern fringe of above average temperatures. Therefore the forecast for Wednesday through the weekend favors low precipitation chances (15-40 percent) and slightly above average temperatures (87-95 degrees) each day. Confidence in potential rainfall amounts or timing remains low. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 619 AM CDT Mon Aug 23 2021 Expect mainly VFR conditions the next 24 hours. There are some MVFR ceilings in the far northern parts of northeast NE north of KOFK and some patchy areas of fog, but we don't expect these to have much of an impact at the TAF sites. Could see some scattered storms in parts of northeast NE today and mentioned a PROB30 group at KOFK for 21z-24z. Otherwise chances at KOMA and KLNK are not zero but too low to include in TAFs. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Albright AVIATION...Miller