Severe Threat Continues South of I-59; Much Cooler & Stable Air Moving In Behind the Storms

As of 10:15 am this morning, the main line of stronger thunderstorms has now pushed south and east of the I-59 corridor, which will now give an all-clear from the severe weather threat for locations north and west of I-59. However, the severe threat continues along and ahead of the line of storms, where there is a risk of damaging thunderstorm wind gusts up to 60 mph and a very small risk of a brief spin-up tornado. SPC just released its latest Mesoscale Discussion and still believes that a severe weather watch is not needed at this time.

Here is the latest Mesoscale Discussion from the SPC:

SUMMARY… Thunderstorm activity will continue to develop along and ahead of a southward advancing cold front through 1-2 PM CST, posing a risk for a few potentially damaging wind gusts and, perhaps, an isolated tornado or two. While the damaging wind/tornado risk appears low enough that a severe weather watch may not be needed, trends will continue to be monitored.

DISCUSSION… A mid-level speed maximum (50-60+ kt around 500 mb) might have contributed to organization of an evolving cluster of storms that is currently overspreading central Alabama. By 18-19Z, this jet streak is forecast to rapidly propagate east-northeastward, into and through the Georgia and South Carolina piedmont, where weak lower/mid-tropospheric lapse rates and slow/limited modification of generally stable boundary-layer conditions appear likely to preclude an appreciable risk for severe weather.

Models indicate that seasonably moist boundary-layer air will remain confined to along and ahead of the southward advancing cold front, across and east-northeast of the lower Mississippi Valley. Even here, weak lapse rates are limiting CAPE to 500-1000 J/kg or less. Given the lack of stronger potential instability, deep-layer wind fields and shear appear only marginally supportive of continuing organized strong thunderstorm development with the potential to produce a few damaging wind gusts and/or, perhaps, an isolated tornado. This is expected to remain generally focused within a corridor of stronger forcing immediately ahead of the front, advancing south of the Interstate 20 corridor through early afternoon, where low-level shear (beneath a 30-40 kt 850 jet axis) is also strongest.

Category: Alabama's Weather, ALL POSTS, Severe Weather