SPC Day 3 Outlook (For Friday)

 This is for Friday night for North Alabama/Southern Middle Tennessee. 

The hatching shows where storms are more likely to be in the form of supercells. This risk is from Friday night through about 7 AM Saturday morning. Onset time is probably about 9-10 PM Friday night for far Northwest AL. 

 SPC AC 120730

   Day 3 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   0230 AM CDT Wed Mar 12 2025

   Valid 141200Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS

   OF THE MIDDLE MISSISSIPPI VALLEY TO THE TENNESSEE VALLEY...

   ...SUMMARY...

   A regional outbreak of severe storms is expected across much of the

   Mississippi Valley, eastward to the Lower Ohio and Tennessee Valleys

   late Friday afternoon into early Saturday morning. All severe

   hazards are possible, including swaths of intense winds and

   tornadoes.

   ...MS/Lower OH/TN Valleys...

   A large cyclone will rapidly intensify as it lifts northeast across

   the central Plains to the Upper Midwest on Friday. A 100+ kt

   southwesterly jet streak at 500 mb will overspread portions of the

   Ozarks/Mid-MS Valley, while a 60-70 kt low-level jet overspreads

   much the Mid-South and Mid-MS/Lower OH Valleys during the late

   afternoon into the overnight hours. Northward extent of deeper Gulf

   moisture (60s F dewpoints) will likely remain south of southeast

   MO/southern IL/western KY, with more modest 50s F dewpoints

   expanding northward into southeast MN/southern WI and eastward

   toward the Lower OH Valley. Despite the more modest moisture across

   the northern half of the outlook area, cold temperatures aloft will

   support steep midlevel lapse rates and at least weak instability. 

   A strongly forced QLCS is expected to develop along a surface

   dryline as the mid/upper jet impinges on the Ozarks vicinity by late

   afternoon or early evening. Intense forcing and deep-layer wind

   fields will maintain an organized QLCS into the nighttime hours.

   Strong daytime heating and mixing of the boundary layer ahead of the

   QLCS will further promote swaths of severe/damaging gusts, some of

   which may be greater than 65 kt. While moisture will be somewhat of

   a limiting factor, QLCS tornadoes also will be possible.

   Convection may develop later across AR into the TN Valley/Deep

   South. However, deeper Gulf moisture will be in place across this

   region (possible mid/upper 60s F). This will support stronger

   instability amid supercell wind profiles. Large-scale ascent will be

   more subtle across this area, but sharpening of the dryline across

   AR and low-level confluence should support convective development

   during the evening. Initial supercells may grow upscale into a line

   moving across portions of AR/TN/northern MS/AL. An attendant risk of

   strong tornadoes and swaths of damaging/potentially significant wind

   gusts is expected across the Mid-South with this activity.

   A more conditional risk for overnight supercells exists across parts

   northern/central MS/AL. The environment could support intense

   supercells capable of producing large hail and strong tornadoes this

   far south, but forcing mechanisms will be weak. Trends will be

   monitored and future outlook adjustments may be needed.

   ..Leitman.. 03/12/2025