Mesoscale Discussion 0117 NWS Storm Prediction Center Norman OK 0202 PM CST Sun Jan 22 2017 Areas affected...Portions of north FL and south GA Concerning...Tornado Watch 21... Valid 222002Z - 222100Z The severe weather threat for Tornado Watch 21 continues. SUMMARY...The onset of a dangerous tornado outbreak is ongoing. A line of potentially tornadic supercells is spreading eastward around 45-50 kt. Long-track, fast-moving, strong tornadoes will be possible. DISCUSSION...A line of discrete/semi-discrete supercells extending from far southwest GA to central/eastern portions of the FL Panhandle will continue spreading eastward around 45-50 kt. Approximate times of arrival of this line are depicted in the accompanying graphical product. Storm-relative motion from radar suggests tightening/strengthening low-level mesocyclones with this activity. This activity now lies east of a front that arcs northward to surface low pressure over central AL featuring a deepening rate of over 1 mb per hour. Preceding pressure falls of 7-9 mb per 2 hours have been noted, with open-warm-sector pressure falls of 3-6 mb per 2 hours. As a plume of high theta-e air continues to stream northward to a warm front advancing north across south GA (serving as convective inflow), and very strong low-level SRH (around 550 m2/s2 in the lowest 1 km above ground per Tallahassee VAD wind profile) continues given the strong surface cyclogenesis, the potential for significant, long-track, fast-moving tornadoes will exist. ..Cohen.. 01/22/2017 ATTN...WFO...JAX...FFC...TAE... LAT...LON 31558464 32018406 31958312 31148294 29988310 29708361 29668433 30018477 31558464