Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Tue Aug 29 2023 17:22:00 ACUS01 KWNS 291953 SWODY1 SPC AC 291951 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Tue Aug 29 2023 Valid 292000Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF FLORIDA IN ASSOCIATION WITH HURRICANE IDALIA...AND CENTERED OVER THE BITTERROOTS... ....SUMMARY... A few tornadoes will be possible late this afternoon through tonight, mainly from the west central Florida Peninsula into the Big Bend area, within the northeast quadrant of strengthening Hurricane Idalia. Occasional damaging wind gusts will be possible across the northern Rockies. ....20Z Update... Little change was made to the existing severe probabilities at 20Z, except for a minor eastward shift for a low wind threat into central MT where minimal instability will develop due to steepening lapse rates. For the Southeast, the threat for a few tornadoes will increase tonight, primarily after 03Z as stronger shear associated with Hurricane Idalia overspreads parts of the western FL Peninsula, and eventually into parts of the Big Bend. ...Jewell.. 08/29/2023 ..PREV DISCUSSION... /ISSUED 1128 AM CDT Tue Aug 29 2023/ ....FL Gulf coast through tonight... Hurricane Idalia is strengthening as of midday over the southeast Gulf of Mexico and is forecast to make landfall Wednesday morning near the FL Big Bend as a major hurricane (please see latest NHC advisories for additional information). Storm motion will be largely parallel to the FL west coast into early tonight, so eastward expansion of the stronger wind field and more favorable low-level hodograph structures will be a gradual process (per the trends in the VWPs from Key West and Tampa). Surface observations show 77-80 F dewpoints across almost all of central/south FL, which will help maintain surface-based buoyancy into this evening and overnight. Thus, the primary increase in supercell/tornado threat is expected late this afternoon into tonight from near Tampa northward along the coast with the more cellular convection within the outer eastern/northeastern bands. ....Northern Rockies this afternoon/evening... A midlevel shortwave trough now over far northern CA and OR will progress east-northeastward toward the northern Rockies by this evening. Though low-level moisture is rather limited, strong surface heating/deep mixing will result in inverted-V profiles with weak buoyancy in advance of the midlevel trough and an associated cold front. Thunderstorm development is expected this afternoon through early tonight in the zone of ascent preceding the midlevel trough (and along the front). The highest confidence in storm development coincident with the steep low-level lapse rates and some enhancement to midlevel flow will be later this afternoon over the Bitterroots, where a few damaging outflow gusts of 60-70 mph will be possible. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .