NWS Storm Prediction Center Norman OK 0952 AM CDT Mon Mar 19 2018 Areas affected...north-central and northern AL...northwest GA...far southern middle TN Concerning...Outlook upgrade Valid 191452Z - 191615Z SUMMARY...An upgrade to a Moderate Risk categorical outlook (driven by a 15% significant tornado risk) is planned for the 1630Z outlook (10:30am CT). DISCUSSION...It appears increasingly probable the risk for several tornadic supercells will traverse across northern portions of AL late this afternoon and through the early evening. Thunderstorm activity will be largely void across a large part of this area (north-central AL) prior to peak heating and a moderately unstable airmass is expected to develop by mid afternoon. The arrival of a speed max in the mid-levels will correspondingly lead to a marked strengthening in low-level flow and increasing hodograph size, which will be more favorable for supercells and low-level mesocyclones. Given these factors, confidence has increased such that a 15% significant tornado risk and the potential for longer lived supercells and damaging tornadoes will focus across north-central and northern AL, far southern middle TN beginning during the late afternoon/early evening, then moving east into northeast AL and far northwest GA later this evening.
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