Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Nov 04 2022 12:52:44 ACUS01 KWNS 041252 SWODY1 SPC AC 041251 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Fri Nov 04 2022 Valid 041300Z - 051200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF CENTRAL...NORTH-CENTRAL...EAST AND NORTHEAST TEXAS...SOUTHEASTERN OKLAHOMA...WESTERN/SOUTHERN ARKANSAS...AND NORTHERN LOUISIANA... ....SUMMARY... A threat for tornadoes, severe gusts and large hail exists today and tonight over parts of central, north and east Texas, southeastern Oklahoma, southern/western Arkansas, and northern Louisiana. ....Synopsis... Mid/upper-level height falls are expected to shift eastward across the Plains to the Mississippi Valley through the period, as a synoptic-scale trough progresses across the northern Plains and eastward out of the southern Rockies. The main convective influence aloft will be a strong, basal perturbation now apparent in moisture- channel imagery from central CO to eastern Sonora, with embedded vorticity max and intermittently closed 500-mb low over northern NM. This trough will shift east-northeastward to near an axis from DDC- LBB to far west TX by 00Z. By 12Z tomorrow, this trough should extend from southwest IA to near STJ, TUL, ADM, and SJT. At the surface, 11Z analysis showed a well-defined cold front from northern/western Lake Superior across eastern IA, to between STJ- MCI, to south-central KS, northwestern OK, the southeastern TX Panhandle, to southern NM. A weak low along the front -- initially between PVW-CDS -- should ripple northeastward along the boundary as the front moves southeastward. By 00Z, the low should be located near the southeastern corner of KS, with front northeastward across southeastern WI and southwestward near a MLC-ACT-LRD line. By 12Z, the front should extend from a strengthening version of the same low, then near DBQ, southward over western IL, southeastern MO and parts of the Mid-South, to south-central LA, offshore from the mid/upper TX Coast, to near BRO. ....Southern Plains to lower Mississippi Valley... Scattered to numerous thunderstorms are expected this afternoon and tonight across the region, with the potential for tornadoes, strong to severe gusts, and sporadic severe hail. A few of the tornadoes may be significant (EF2+ damage capable) and fast-moving. Surface dewpoints near 70 F are approaching I-20 southeast of the DFW Metroplex at this time, with mid-60s dewpoints already noted in parts of southeastern OK. In the preconvective moist sector, continued spread of richer boundary-layer moisture will occur northward across parts of TX, eastern OK and the Arklatex region through tonight, resulting in a deeply moist boundary layer with low LCL. Widespread low clouds will temper insolation, but a combination of steady/muted heating and theta-e advection will contribute to peak/preconvective MLCAPE ranging from around 1000 J/kg over eastern OK to 2500 J/kg in central/southeast TX. Given the lack of a substantial EML, two boundaries in particular should support convective development from midday through this evening: 1. The surface cold front as it crosses parts of OK and north/ central TX, and to its east, 2. A warm-sector confluence/convergence band and related wind shift, east of which relatively backed surface winds will underlie a strengthening LLJ to yield large, quite favorable SRH/hodographs. Additional thunderstorms may develop in the weakly inhibited warm sector east of the prefrontal wind-shift line as well. Any such activity that persists will have the potential to evolve into fast-moving (40-45 kt translational speed), discrete to clustered supercells with the greatest potential for strong, relatively long-lived tornadoes. Hodographs along and east of the wind shift may attain 100-250 J/kg of 1/2-km SRH, and 300-450 J/kg effective SRH. Though not as large, hodographs between there and the front still will be long, amidst favorable deep shear (50-65-kt effective-shear magnitudes), favorable for supercells as long as convection is at least semi-discrete. The main uncertainties still involve convective coverage in the free warm sector, and given a strongly parallel component of the deep- shear vectors with both the front and the prefrontal boundary, the potential for fairly quick upscale evolution to quasi-linear mode after initiation. Either way, even a quickly growing prefrontal QLCS will offer potential for tornadoes as it impinges on the LLJ-boosted large hodographs to its east. By about 06Z, a dominant squall line should evolve from the earlier convective bands and move eastward across AR/LA and southeast TX, ultimately into the Mid-South and parts of MS through sunrise tomorrow. The severe threat will diminish gradually with eastward extent as the line encounters progressively more-stable boundary- layer trajectories emanating from the prior/southeastern U.S. postfrontal anticyclone, with weaker marine airmass modification. In essence, the convection will outrun the most favorable destabilization, but especially in southern parts, still will be capable of isolated severe gusts and perhaps a tornado as it moves through the Delta region late overnight. ....Central Plains/Missouri... Widely scattered thunderstorms are ongoing along and behind the front from northwest TX to northwestern OK, northeastern KS, and northwestern MO. Convective coverage is expected to increase in this slowly eastward-shifting regime through the remainder of the morning and into midafternoon, as the front impinges on progressively greater boundary-layer theta-e. A threat for isolated severe wind, hail and perhaps a tornado may develop, with the wind and tornado potential along/ahead of the front, and hail on either side. A narrow corridor of MLCAPE around 1000 J/kg will develop along/ahead of the front as boundary-layer moisture advection/ transport continue, and midlevel cooling occurs ahead of the ejecting 500-mb low/vorticity max. Increasing and largely boundary-parallel deep shear suggest predominantly linear mode. The resulting convection should cross much of northern and perhaps central OK, central/eastern KS, and western MO into this evening, northwest of the prefrontal regime discussed above. ...Edwards/Smith.. 11/04/2022 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .