SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Sun Feb 14 2021 Valid 141300Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF CENTRAL AND NORTHERN FLORIDA... ...SUMMARY... Damaging to severe gusts are possible within episodes of thunderstorms today over central and northern Florida, along with a slight threat for tornadoes. ...Synopsis... In mid/upper levels, broadly cyclonic flow will continue across much of the central CONUS and MX, on either side of a progressive synoptic trough. The trough was located at 12Z from western CO south-southwestward across eastern AZ and the central/northern Gulf of California. By 12Z tomorrow, this trough should extend across central KS, southwestern OK, west-central TX, and north-central to west-central MX. Downstream, a broad fetch of southwesterly flow will cover most of the eastern CONUS, Gulf of Mexico and FL. Several minor vorticity lobes/maxima will eject northeastward within that belt, across the Gulf and Southeast. The two most prominent embedded shortwave troughs were apparent in moisture-channel imagery near the FL West Coast and over the west- central Gulf. This feature will proceed northeastward to the Atlantic over the next several hours and deamplify. Meanwhile, the upstream perturbation should eject northeastward across the central/ northern Gulf as a weakening, negatively tilted perturbation, reaching southern portions of MS/AL and northwestern FL by 00Z, then accelerating northeast and essentially dissipating overnight. At the surface, somewhat wavy, quasistationary front extended east-northeast to west-southwest across north-central FL, then to a frontal-wave low over the north-central Gulf south of the Mississippi River mouth, then well offshore from BRO. Over FL, this boundary may move slightly northward as a warm front today as the surface low approaches, then once the low is past Fl by mid/late afternoon, the front should move little or just slightly southward again. This evening, ahead of the major trough aloft, a stronger frontal-wave low will form over the Gulf east of BRO, and ripple northeastward along the front to shelf waters south of ARA or HUM by 12Z. ...FL... South of the front, an outflow boundary that had been drawn across central FL near a PIE-DAB line has been diffused by convection that since has crossed FL on both sides of the boundary. Large-scale ascent ahead of the leading perturbation has been contributing to a favorable environment for showers and mostly non-severe thunderstorms all night into early this morning over FL, except for a briefly tornadic supercell near PIE around 06Z, along the southern boundary. Near-surface airmass recovery -- driven both by warm advection and muted diurnal surface heating under cloud cover -- is expected across central and parts of northern FL behind the morning convection. Associated destabilization will combine with a moisture-rich low-level profile south of the synoptic front to offset modest midlevel lapse rates, enabling deep buoyancy. Severe potential with the next round(s) of convection, from midday through afternoon, will decrease with southward extent due to weaker deep shear and low-level shear, and with northern extent past the front into unsuitably stable near-surface conditions. The corridor of most-favorable parameter spaces still appears to be across parts of central and north-central FL. Weak MLCINH and MLCAPE around 1000-1500 J/kg should develop. Patches of 150-250 J/kg effective SRH will support a few supercells and small bows embedded in an otherwise rather messy convective pattern. Activity should diminish this evening and overnight due to a combination of slow surface stabilization and lack of robust support aloft, southeast of the weakening mid/upper perturbation. ..Edwards/Smith.. 02/14/2021
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