re: Severe weather threat for Today/Tomorrow across the SE All severe modes possible

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Driving back to Bham from Atlanta this afternoon should be fun.

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I hope your username doesn’t come to fruition

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Area Forecast Discussion National Weather Service Birmingham AL 858 AM CST Thu Feb 16 2023 ...New MESOSCALE UPDATE... .MESOSCALE UPDATE FOR SEVERE WEATHER... Issued at 856 AM CST THU FEB 16 2023 Previous forecast remains on-track. Overnight modeling along with 06z and 12z local and regional soundings indicate stronger capping has materialized and is helping to suppress shower development across the area early this morning. The forecast area remains positioned between a broad mid-level ridge over the Bahamas and Cubs while a closed low was located over North-Central Kansas embedded within a positive tilt trough over the plains. Surface high pressure was positioned further east across the Central Atlantic while surface low pressure was positioned across the Ozark Mountains in Arkansas. A stationary front extends northeast of the low across the Ohio River Valley while a cold front extends from the surface low south into Coastal Texas. Local enhanced RAP 13 km mesoanalysis depicts a broad warm sector encompassing all of Mississippi into at least the western half of Central Alabama, characterized by temperatures already in the upper 60s to around 70 degrees. Dew points, likewise, are in the low to mid 60s across Mississippi into much of Alabama. With the more robust capping and some cloud breaks, while our forecast high temperatures have been toward the upper end of guidance, it remains potentially attainable in this scenario. More that sufficient instability will exist with uncharacteristically high numbers of buoyancy that exceeds the more typical values experienced for this time of year in our part of the country. In the shear-instability parameter space, we more typically focus on the lower CAPE-higher shear portion of the spectrum, however, setups like this resemble the more opposite end of the spectrum for our area with higher CAPE values that do not require as strong of magnitude of shear than we typically expect. Wind shear is more than sufficient for severe thunderstorms and tornadoes. The capping off the surface, as depicted on the observed soundings, are associated with a slug of drier air that composes the Elevated Mixed Layer. Some of this drier air will work downward toward the surface and can result in at least a temporary reduction in low level moisture. As we progress through later this afternoon and into the evening hours, boundary layer vertical mixing will decrease and this will allow for low-level moisture values to increase. Due to this potential, we may see slightly higher-based convection through the afternoon hours with potentially increased visibility of supercell structures with the more classic supercell storm mode preferred. As we move into the evening and overnight, the low-level moisture values will again increase and result in lower cloud bases, lower lifted condensation level heights, and will continue to support nocturnal severe weather and tornado potential. Additionally, as vertical mixing decreases into the evening, the low-level jet is expected to intensify as well, further providing sufficient wind fields for severe storms and some tornadoes. The overall event storm mode will support supercell structures with an overall general tendency to eventually attempt to congeal into a line of deep convection. It is expected for supercells to develop and move across portions of the western and into the central counties this afternoon and evening. For the later part of the evening and overnight, we could retain some supercells across the eastern counties, though some linear formation would eventually be expected. Given continued cloud breaks south, persistent low-level warm advection and a gradually eroding capping inversion that looks to give way across the area with time as shortwave impulses with some height falls later today will support all modes of severe weather. Tornadoes will be an areawide risk with best potential at least initially across portions of the west and southwest counties through early afternoon. Damaging winds will be possible, especially with any linear convective configuration that materializes later today. Large hail will be possible with the stronger storms as more intense updrafts are expected given the stronger buoyancy. Additionally, localized flooding will be possible where training of heavy convection occurs, especially over terrain and urbanized areas. Through noon, expect a few low-topped light showers will still occur from time to time through the morning hours that develop beneath the cap located around 805 mb per latest sounding. This activity will move quickly northeast over 50 mph as the low-level jet from the southwest continues to increase in the lower and mid levels. We are monitoring convection developing over Southern Mississippi that will be moving northeast toward our southwest counties towards early afternoon. The next mesoscale update will be sent by noon. 05

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