Administrators NorthGeorgiaWX Posted December 22, 2023 Administrators Share Posted December 22, 2023 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0653 AM CST Fri Dec 22 2023 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHERN ARIZONA... ...SUMMARY... Isolated large hail and strong-severe gusts are possible from midday into evening across parts of southern Arizona. ...Synopsis... A closed, mid/upper-level cyclone was apparent in moisture-channel imagery offshore from southern CA and northern Baja -- centered about 200-225 nm west-southwest of SAN. Separately, a strong, northern-stream shortwave trough was evident just offshore from the Pacific Northwest. The northern-stream trough will move inland by around 18Z today, then reach the northern Rockies by the end of the period. It will be increasingly phased with the increasingly progressive, southern-stream cyclone/trough, whose circulation center should cross northernmost Baja around 00Z, then shift northeastward toward the Grand Canyon/FLG region by 12Z tomorrow. ...Southern AZ... Isolated severe hail and/or gusts are possible today over portions of southern AZ. Ahead of the mid/upper cyclone, a baroclinic-leaf pattern apparent in satellite imagery -- with precip and embedded thunderstorms that should remain elevated and nonsevere for several more hours -- will continue to spread eastward to northeastward over the region through the day. Meanwhile, at the surface, and in low levels, warm advection and moisture transport are forecast to increase today over much of the Desert Southwest, beneath a zone of strong difluence aloft preceding the mid upper-level cyclone. So will large-scale DCVA-related lift closer to the cold-core region. predominantly separate areas of strong/isolated severe-thunderstorm potential will develop in each regime from midday into early evening, but with some spatial overlap in the outlook area due to the progressive nature of the system as a whole. Diurnal destabilization should be gradual, given the presence of cloud cover to limit the pace and strength of diabatic surface heating. However, in combination with boundary-layer theta-e advection and cooling aloft, low/middle-level lapse rates should steepen, with that and increasing low-level moisture contributing to lessening MLCINH through the afternoon. Activity developing in MX, or near the international border, near or off the southern rim of the early cloud/precip shield, will move into an increasingly buoyant environment, with each regime yielding peak MLCAPE in the 300-800 J/kg range. Strengthening deep shear should aid in storm organization, though potentially messy mode and lack of greater instability may be counterbalancing factors. Forecast soundings suggest strong deep/speed shear, with long but not especially large hodographs by the time surface-based effective-inflow parcels are common. 45-55-kt effective-shear magnitudes are expected area-wide. Decreasing instability should diminish severe potential with time overnight. ..Edwards/Broyles.. 12/22/2023 Read more View the full article Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.