Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 PM CST Sat Jan 21 2017 Valid 220100Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN ARKANSAS TO NORTHERN LOUISIANA INTO WESTERN MISSISSIPPI... ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST MISSISSIPPI INTO SOUTHERN AND SOUTH CENTRAL ALABAMA AND SOUTHWEST GEORGIA... ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE LOWER MISSISSIPPI VALLEY INTO MUCH OF THE GULF COASTAL STATES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER MISSISSIPPI VALLEY INTO MUCH OF THE SOUTHEAST STATES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE LOWER AND MIDDLE MISSISSIPPI VALLEY INTO MOST OF THE SOUTHEAST STATES... ...SUMMARY... Severe storms are will persist this evening and into the overnight from parts of the lower Mississippi Valley into the Gulf Coast states. Some of the storms will be capable of producing significant severe weather including a strong tornadoes and very large hail. ...Lower Mississippi Valley through the Gulf Coast states... Early this evening a warm front extends from the Gulf Coast through LA, southwest AR and OK. This boundary will continue to advance north into the Gulf Coast states and serve as a focus for severe storms tonight. Severe thunderstorms including a few supercells are underway from northern LA into southern AR and are developing in association with ascent attending a progressive vorticity maximum located in the exit region of a strong upper jet. These storms are embedded within 45-50 kt effective bulk shear, and 0-1 km hodographs are sufficient for low-level mesocyclones. The CAPE/Shear parameter space will continue to support the risk for very large hail and tornadoes this evening. The atmosphere has destabilized in vicinity of the warm front with steep lapse rates and a corridor of MLCAPE from 1000-1500 J/kg from the lower MS Valley into the Gulf coastal area. Additional storms are developing along and just north of the warm front from the central Gulf Coast into southern LA. The low-level jet should undergo a significant increase over the Gulf Coast states tonight in response to mass adjustments within exit region of approaching upper jet. This process will promote additional thunderstorm development along and just north of the warm front with theta-e advection beneath steep mid-level lapse rate plume contributing to moderate instability. The coupled jet structure will result in very favorable vertical wind profiles for supercells with low-level mesocyclones. Mixed modes with both discrete cells and clusters are likely. Given the shear/instability parameter space, some supercells will become capable of producing strong tornadoes in addition to large hail and damaging wind. ..Dial.. 01/22/2017Read more
from SPC Forecast Products http://ift.tt/rxAC6Z
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