691 FXUS63 KOAX 091128 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 628 AM CDT Tue Jul 9 2019 .SHORT TERM...(Today through Thursday) Issued at 331 AM CDT Tue Jul 9 2019 Rain and thunderstorms this morning, another chance this afternoon and tonight, then cooler temperatures for a couple of days, are the primary highlights of the forecast. Well-defined MCV on radar was spinning into our western CWA just after 2 AM this morning, with line of scattered thunderstorms arcing south and southwest into central Kansas. This line will continue pushing east into east central and southeast Nebraska where juicy atmosphere exists, characterized by lower 70s surface dew points. Short-range mesoscale model output suggests storms will weaken rather rapidly around 12Z, and intensity trends have been downward as of late. There is still 500-1000 J/kg of MLCAPE available for convection ahead of line, so would expect only a gradual weakening trend through sunrise. To the north of the MCV, widespread rain with a few embedded lightning strikes should continue across northeast Nebraska into west central Iowa this morning. All activity is forecast to be moving east of our western Iowa counties between 15Z and 18Z today. Behind this system, atmosphere is expected to recover during the afternoon as low level moisture remains in place despite southwesterly surface wind component. Upper level forcing and low level convergence are weak during the afternoon when MLCAPE again exceeds 2500 J/kg, and nearly all model output keeps a lid on afternoon redevelopment. However with high instability and remnant low level convergent boundaries from morning convection, would not be surprised if a few storms could get going a couple of counties either side of Interstate 80. A more likely area of afternoon storm development is in the Nebraska Panhandle or southwest South Dakota where strong mid level jet streak and shortwave will steepen lapse rates and increase forcing. Models are fairly consistent in breaking out convection there, with a southeast propagation into central Nebraska during the evening, and eventually eastern Nebraska overnight. Strong layer wind fields suggest a damaging wind threat with this activity, mainly west of our area as diurnal cooling stabilizes boundary layer this far east. Any overnight convection should move out of southeast Nebraska early Wednesday, with cooler northwesterly flow to follow as surface high pressure settles into the region. 850 temps drop 5-7C, pointing to highs only in the low to mid 80s Wednesday, and lows close to 60 Wednesday night. There is some potential for afternoon showers Wednesday in western Iowa where steep lapse rates will exist. Otherwise a dry forecast takes us into Thursday when southerly low level flow returns in the afternoon, boosting temps a degree or two higher than Wednesday. .LONG TERM...(Thursday night through Monday) Issued at 331 AM CDT Tue Jul 9 2019 Warmer and more humid weather returns to the region for the weekend as mid level ridge in the Southwest pushes closer to the Plains. However main storm track around northern periphery of ridge is expected to remain close to the South Dakota and Nebraska border region much of the weekend. Thus perturbations in the flow will likely affect at least our northern CWA from time to time. These occurrences should favor the late night periods when mid level capping weakens and low level jet strengthens. Otherwise expect high temperatures in the 90s each day, with heat indices close to 100. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 623 AM CDT Tue Jul 9 2019 Line of TSRA is pushing out of ERN NE and into WRN IA. Activity should be moving out of KOMA within an hour or so. Otherwise, VFR conditions will prevail thru the fcst pd. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Dergan LONG TERM...Dergan AVIATION...DEE