SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Oct 10 2021 Valid 101200Z - 111200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM SOUTHWEST THROUGH CENTRAL AND EASTERN OKLAHOMA... ...SUMMARY... A potentially significant severe weather event is forecast across a portion of Oklahoma into north Texas late this afternoon into the overnight. Severe storms capable of large to very large hail, a few strong tornadoes and damaging wind are expected. ...Southern Plains area... A vigorous shortwave trough situated near the Four Corners region will advance east through the southern Plains this afternoon and evening before reaching the lower to mid-MS Valley late tonight. In advance of this feature, a cold front now over the central Plains will move slowly south. By late afternoon this front will extend from a weak surface low in the southeast TX Panhandle or northwest TX, northeast through north central OK, southeast KS and northwest MO. This boundary will move slowly south into the evening. A dryline will extend southward from the surface low through west TX, but will eventually be overtaken by a Pacific cold front accompanying the progressive shortwave trough. Richer low-level moisture return is already underway with mid 60s F dewpoints approaching central TX. As temperatures warm through the 80s F along with modest mid-level lapse rates, up to 1500-2000 J/kg MLCAPE is likely by late afternoon. Initial storms should initiate over southwest OK or northwest TX along intersection of the dryline and the southwest-northeast oriented cold front. Given strength of effective bulk shear with 50+ kt associated with the approaching mid-upper jet, this activity should quickly become supercellular. Hodograph size should undergo a substantial increase as the low-level jet strengthens during the early evening with 0-1 km storm-relative helicity likely exceeding 250 m2/s2 by 00Z. Given the favorable kinematic and thermodynamic parameter space, potential exists for a couple of long track supercells to evolve and track east northeast through OK along and just south of the front. These storms will be capable of producing very large hail and strong tornadoes. Additional storms will likely develop farther northeast along this front as well farther south into TX as the Pacific front intercepts greater low-level moisture. These storms will also likely become supercells capable of all hazards. Eventually, storms may evolve into lines and clusters during the evening and into the overnight, but with a continued severe threat toward the lower and middle MS Valley regions. ...Upper Mississippi Valley and Great Lakes regions... A northern-stream shortwave trough will advance slowly northeast through northern MN during the day. Storms may increase over northeast MN just northeast of the vorticity maximum during the afternoon where wind profiles and modest instability will be sufficient for supercells. Primary threat with this activity will be hail and possibly a couple of brief tornadoes. Farther southeast across WI within the dry slot region, the extent of thunderstorm initiation during the day remains uncertain, but a conditionally favorable environment for supercells will exist. If confidence increases that robust updrafts can develop in this environment, then a categorical risk upgrade may be needed in later day 1 updates. ..Dial/Marsh.. 10/10/2021 Read more LIVE: spc.noaa.gov
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