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SPC - No watches are valid as of Mon Apr 12 12:45:02 UTC 2021
No watches are valid as of Mon Apr 12 12:45:02 UTC 2021.
SPC - No MDs are in effect as of Mon Apr 12 12:45:02 UTC 2021
No Mesoscale Discussions are in effect as of Mon Apr 12 12:45:02 UTC 2021.
SPC Apr 12, 2021 1300 UTC Day 1 Convective Outlook
SPC 1300Z Day 1 OutlookDay 1 Convective Outlook NWS Storm Prediction Center Norman OK 0740 AM CDT Mon Apr 12 2021 Valid 121300Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF SOUTHWEST...CENTRAL AND NORTH TEXAS... ...SUMMARY... At least a few afternoon and evening thunderstorms will produce large hail -- including destructive hailstones 2+ inches across -- as well as locally damaging winds, in parts of southwest, central and north Texas. ...Synopsis... While a mid/upper cyclone meanders eastward over the Upper Midwest, a strong shortwave trough will dig southward and intensify from southeastern BC across the Pacific Northwest. Largely zonal to southwesterly flow will be maintained to their south across the Southwest and southern Plains, while a separate northern-stream low now over OH accelerates southeastward past Chesapeake Bay. In the southern stream, a perturbation is apparent in moisture-channel imagery over northwestern MX, which will move northeastward over much of the main body of TX through this evening. At the surface, 11Z analysis showed a primary low over northwestern WI, with cold front southward/southwestward over southern WI, western IL, the MO Ozarks, southeastern OK, to a low near ABI, then westward to near CNM. The northern low will continue to become more deeply occluded and meander around the western Lake Superior/ northern MN region through the period. The cold front should reach northeastern AR, southeastern OK, north-central TX, the Edwards Plateau, and the lowest segment of the Pecos Valley by 00Z. By 12Z, the front should extend from central/southern AR across portions of south-central/southwest TX. As moisture returns to its east, a dryline should sharpen today from northern Coahuila to its afternoon frontal intersection -- roughly between SJT-MAF. ...Southwest TX to southeastern OK... Isolated to widely scattered thunderstorms are expected to form mid/late afternoon along the front, dryline and/or Serranias del Burro in MX. The latter activity may remain southwest of the Rio Grande or barely cross, except for left-moving storms, which forecast hodographs favor across much of the outlook area. A few supercells are possible, offering severe to very large hail (some significant, over 2 inches in diameter), and localized damaging wind. Morning RAOBs and near-term model soundings across the region depict a substantial EML, which will require combined lift from sustained diurnal heating (through some cloud cover preceding the southern- stream perturbation) and the boundaries/mountains to overcome. Large-scale ascent -- increasing ahead of the ejecting shortwave trough -- also will help to maintain a favorable environment aloft. Development will be somewhat high-based, atop increasing low-level moisture and a well-mixed subcloud layer, and amidst steep (7.5-8.5 deg C/km) midlevel lapse rates. This will contribute to peak preconvective MLCAPE ranging from 2000-3000 J/kg, weakening northeastward past the DFW Metroplex and into southeastern OK where moisture recovery will be less mature. Though low-level wind speeds will be modest, favorable directional shear and favorable winds aloft (45-70 kt in the 500-250-mb layer) will contribute to supercell-favoring effective-shear magnitudes in the 45-55-kt range over the 15%/"Slight" area. Remaining convection should weaken late this evening as nocturnal diabatic stabilization proceeds. ...South FL and Keys... An extensive cold pool from yesterday's severe MCS covers South FL and surrounding waters across the Straits, to parts of the Bahamas and coastal northern Cuba. This is being reinforced by another complex of thunderstorms now moving southeastward across the eastern Gulf and western Straits, west through south of the Dry Tortugas and lower Keys. Still, elevated instability atop the cold pool will continue to support the development of widely scattered thunderstorms through the remainder of the morning, before supportive ascent weakens. MUCAPE in the 500-1000 J/kg range, coupled with 50-60-kt effective-shear magnitudes, suggest isolated hail near severe limits cannot be ruled out. However, the threat appears too isolated and uncertain to introduce an unconditional severe risk. ..Edwards/Broyles.. 04/12/2021Read more
SPC Apr 12, 2021 Day 4-8 Severe Weather Outlook
Day 4-8 OutlookDay 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0343 AM CDT Mon Apr 12 2021 Valid 151200Z - 201200Z ...DISCUSSION... Severe potential appears limited during the Day 4-8 period. A series of surface cold fronts is forecast to push southeast into the Gulf of Mexico as the western upper low/trough weakens and ejects eastward across the Plains and Midwest through the end of the week. This will keep Gulf moisture limited to south Texas and the FL Peninsula, with only weak elevated instability forecast across portions of the southern Plains into the southeastern states. Southwesterly low level flow will maintain warm advection across parts of the southern Plains and central Gulf Coast vicinity, but limited instability, along with stronger upper forcing remaining well north of the region, should preclude any substantial severe threat through Days 5-6/Fri-Sat. Surface high pressure will build behind the cold front during the weekend/early next week, leaving a dearth of moisture across the U.S. east of the Rockies and severe potential will be low.Read more