The forecast remains on track this afternoon, with moisture continuing to stream northward ahead of the dryline. The Storm Prediction Center has indicated that a tornado watch will be issued by 4-5PM for Texoma and portions of North Texas. Thunderstorm initiation is probable by 5-6PM near the Red River. This development will explosively intensify and become severe quickly. Storms will move off to the east/northeast. By early evening, additional isolated thunderstorm development may occur further south on the dryline, which will be located just west of the DFW Metroplex. The highest chance of a storm will be along and north of Highway 380, but cannot be ruled out north of Interstate 20. Any storm that develops has a good chance of being severe with a risk of very large hail up to the size of baseballs, damaging wind gusts over 70 MPH, and potentially a few tornadoes. The threat for tornadoes will increase after 7 PM as low level winds become more favorable. The severe weather threat could continue into the late evening hours.
Mesoscale Discussion 0335 NWS Storm Prediction Center Norman OK 0249 PM CDT Sun Mar 26 2017 Areas affected...Central/Northeast OK...North-Central TX Concerning...Severe potential...Tornado Watch likely Valid 261949Z - 262115Z Probability of Watch Issuance...95 percent SUMMARY...Supercell thunderstorms capable of all severe hazards, including tornadoes and very large hail, are expected across portions of central OK and north-central TX this afternoon and evening. A tornado watch will likely be needed by 21Z. DISCUSSION...Recent surface analysis shows a low centered just northwest of GAG with a dryline arcing southeastward to just west of CSM and then southwestward through FDR (in southwest OK) and ABI (in the low rolling plains of TX). A warm front also extends from this low eastward/southeastward from GAG to END to CUH and on into southeast OK. Low-level moisture continues to advect northward in the warm sector between the dryline and warm front, with 60 degree F dewpoints as far north as Love, Carter, and Marshall counties in far south-central OK. Mid-50 degree F dewpoints extend as far north as Caddo, Grady, and McClain counties. Given the filtered sun across the region, some modest mixing is possible but dewpoints are still expected to range from the mid-50s to low 60s from central OK southward into north-central TX. This low-level moisture coupled with steep mid-level lapse rates will result in moderate instability (i.e. MLCAPE from 1500 to 2000 J/kg) by 21Z ahead of the approaching dryline. Visible satellite imagery continues to show agitated cumulus beneath the mid/high-level cloud band with some towering cumulus also noted near the western edge of the cloud band, close to current position of the dryline. The western edge of the cloud band also likely represents the leading edge of strong forcing for ascent associated with the approaching shortwave trough. As such, the current thinking is that convective initiation will occur as the dryline and stronger forcing for ascent interacts with the destabilizing airmass across central OK around 21Z. Favorable kinematic profiles characterized by 0-6 km bulk shear near 50 kt will support quick storm organization, resulting in supercells capable of all severe hazards including tornadoes. Additionally, low-level jet increase around 00Z will lengthen hodographs in the presence of ongoing storms, resulting in a locally higher threat for tornadoes from south-central OK into northern portions of north-central TX. Somewhat different scenario will lead to the chance of a few tornadoes farther north within the marginally moist environment across north-central OK and possibly into far south-central KS. Here, some severe threat, including tornadoes, is possible as storms interact with the warm front draped across the region. ..Mosier/Guyer.. 03/26/2017