489 FXUS64 KTSA 160158 AFDTSA Area Forecast Discussion National Weather Service Tulsa OK 858 PM CDT Thu Jul 15 2021 ...UPDATE... .DISCUSSION... Isolated storms that popped up within a pocket of instability north of Fort Smith are slowly running out of instability and should continue to weaken and dissipate. Storms are becoming more numerous along the outflow boundary across southern KS and should get additional upper level support through the remainder of the evening into the early morning hours as a shortwave over central KS continues to dig southeast. The latest CAM guidance continues to support the idea of the outflow boundary drifting south with additional storms developing westward across north-central OK and eventually moving east into our northern tier counties. Gridded data was updated earlier to reflect a slightly later onset of convection and hold POPs higher west of I-44 through sunrise then shift them south and east through late Friday morning. Deep moisture continues to be pooled along the outflow boundary and ahead of the stationary front from northwest OK into northern KS with strong 850-700 moisture transport across much of central and northeast Oklahoma. As a result storms should remain very efficient in producing very heavy rainfall rates in excess of 2"/hour. With marginal deep layer shear also in place and flow generally parallel to the sagging outflow boundary, localized flash flooding will remain a concern overnight. Sufficient cold pool strength should be achieved by daybreak to help push the outflow south as convection begins to increase across northwest AR and east-central OK. Will need to watch for redevelopment in the wake of the morning round of storms but with uncertainty in that and the eventual outflow location do not anticipate expanding the Flash Flood watch at this time. && .PREV DISCUSSION... /Issued 627 PM CDT Thu Jul 15 2021/ AVIATION... CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG. Current VFR conditions will likely give way to MVFR to IFR conditions later tonight across northeast Oklahoma and far northwest Arkansas as showers and storms roll into the area. MVFR to VFR conditions are expected Friday at most sites with showers and storms still affecting area sites at least through the morning hours. PREV DISCUSSION... /Issued 206 PM CDT Thu Jul 15 2021/ DISCUSSION... Persistent pre-frontal convection across northern OK into southeast KS is expected to expand in coverage and eventually sag into portions of northeast OK this evening. Instability (SBCAPES around 3000 J/KG) will be sufficient for some strong/marginally severe storms, although overall weak shear should prevent more significant severe activity from occurring. With PWATS running around 2", expect very efficient rainfall rates, with some locally heavy rainfall likely. Used the HREF mean QPF which focuses the heaviest rainfall from southeast KS into northeast OK, although there remains some uncertainty as to where the heaviest rain may occur. That said, went ahead with a Flash Flood Watch overnight for parts of northeast OK. Bulk of the CAMs shift the showers/storms farther southeast on Friday. There is some concern for additional development closer to the frontal boundary by Friday night as suggested by the NAM/ECMWF, so will need to monitor for the threat of additional heavy rainfall. Rain chances will continue into the weekend, with an uptick in activity possible by early next week as another wave and associated front dip into the region. The better chances of rain are expected to shift farther south Tuesday into Wednesday as the boundary sags south. Temperatures will remain below normal through the period, with highs generally in the 80s for early/mid week. Expected a gradual warming trend late in the week as drier conditions prevail. && .TSA WATCHES/WARNINGS/ADVISORIES... OK...Flash Flood Watch through Friday morning for OKZ054>059-061>063. AR...None. && $$ SHORT TERM...24