Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Feb 08 2023 20:01:13 ACUS01 KWNS 082001 SWODY1 SPC AC 081959 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0159 PM CST Wed Feb 08 2023 Valid 082000Z - 091200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PORTIONS OF NORTHEAST LOUISIANA...SOUTHEAST ARKANSAS...AND MUCH OF WESTERN AND CENTRAL MISSISSIPPI... ....SUMMARY... Severe thunderstorms are expected this afternoon into tonight, mainly across parts of the lower into middle Mississippi Valley. Some of these will be accompanied by a risk for tornadoes, a couple of which could become strong this evening across parts of eastern Louisiana and southeastern Arkansas into western and central Mississippi. A significant uptick in convection has been observed in the last hour along the cold front in eastern Texas, within the moisture plume moving off the Gulf of Mexico, and within the uncapped warm/moist airmass across Louisiana and southern Mississippi. However, these storms are relatively unorganized thus far, owing to the weak shear (~20-25 knots per area VWPs). However, as the trough approaches and shear strengthens this evening, expect more storm organization, including supercells capable of tornadoes. A few tornadoes could be strong as the low-level jet strengthens to around 55 knots, elongating the low-level hodograph and doubling the 0-500m shear (per RAP forecast soundings). Farther north, the forecast remains on track. Low 60s dewpoints are now into western Tennessee, which will advect northward rapidly this evening and overnight as low-level flow strengthens. ...Bentley.. 02/08/2023 ..PREV DISCUSSION... /ISSUED 1027 AM CST Wed Feb 08 2023/ ....Synopsis... The more prominent belt of split mid-latitude westerlies is undergoing considerable amplification across the eastern Pacific into western North America. This will continue through this period, with mid-level ridging building inland of the Canadian and U.S. Pacific coast by late tonight. As this occurs, a vigorous downstream short wave trough is forecast to dig sharply along the Rockies, with mid-level flow ahead of it trending southwesterly and strengthening across the southern Great Plains through the Ohio Valley. A significant mid-level trough/elongating low is already beginning to pivot east of the southern Rockies as it begins to interact with a belt of westerlies emanating from the subtropical eastern Pacific. The trough axis is likely to gradually take on an increasingly negative tilt across Oklahoma and Texas during the day today, before accelerating north-northeastward through the middle Mississippi/lower Ohio Valley vicinity by 12Z Thursday. Models continue to indicate that associated forcing for ascent will contribute to significant surface cyclogenesis from near/northwest of the Ark-La-Tex by late this afternoon into areas north-northeast of the St. Louis area by the end of the period. In the wake of a couple of significant recent cold intrusions, boundary modification over the northwestern Gulf of Mexico is still underway. Mid/upper 60s surface dew points have advected inland within at least a shallow pre-cold frontal plume across Texas coastal areas into portions of the Piney Woods. A somewhat more substantive influx of Gulf moisture is forecast to overspread the Louisiana coast through much of the lower Mississippi Valley later today through tonight. Near the northwestern periphery of mid-level subtropical ridging, centered and becoming a bit more prominent across the Bahamas, mid/upper-levels are relatively warm, and lapse rates might not become particularly steep. However, the development of weak to moderate boundary-layer CAPE still appears probable within the evolving warm sector, in the presence of strengthening deep-layer shear which is expected to become sufficient for organized convection, including supercells. ....Southeastern Great Plains into Mississippi Valley... The primary mid-level trough may be preceded to its south and southeast by one or two subtropical perturbations, and the influence of associated forcing for ascent on thunderstorm development within the plume of returning moisture, while the boundary-layer attempts to destabilize inland of coastal areas, remains unclear. At the present time, the low-level moisture return associated with the stronger low-level flow (still around 40-50 kt around 850 mb) is tending to be undercut by the eastward advancing cold front, to the south of the developing surface low over northeast Texas. Meanwhile, convection allowing models generally indicate that a considerable amount of convection may commence in the destabilizing warm sector, well ahead of the cold front, across portions of Louisiana into Mississippi this afternoon. This would likely be prior to substantive strengthening of the low-level wind fields and associated hodographs, though the environment could be supportive of at least weak updraft rotation. Depending on the impact of earlier convective development, forcing along and just ahead of the eastward advancing cold front likely will become the focus for increasing vigorous thunderstorm development late this afternoon and evening. This probably will including one or two evolving lines, with supercells embedded within and perhaps preceding it. Coupled with strengthening southerly 850 mb flow along a corridor near/east of the Mississippi River, as surface cyclogenesis proceeds, a window of opportunity may develop this evening for one or two sustained, long tracked supercells capable of producing strong tornadoes. The possible lingering influence of at least a shallow residual stable surface-based layer results in more uncertainty concerning severe weather potential closer to the track of the surface cyclone. However, mid/upper forcing for ascent and deep-layer mean wind fields/shear will be stronger across this region, and could contribute to potential for damaging surface gusts and perhaps tornadoes. $$ = = = 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) .