Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Mon May 08 2023 15:52:00 ACUS01 KWNS 081948 SWODY1 SPC AC 081947 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0247 PM CDT Mon May 08 2023 Valid 082000Z - 091200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THE OZARKS INTO THE OHIO RIVER VALLEY AND ACROSS PORTIONS OF SOUTH TEXAS... ....SUMMARY... Scattered severe thunderstorms are most likely from the Ozark Plateau to the Lower Ohio Valley, centered on 4 to 11 PM CDT. Large hail and damaging winds should be the main severe risks. Severe thunderstorms are also possible across areas such as South Texas. ....Ozarks to Lower Ohio Valley... Convective initiation appears likely within the next 1-2 hours across south-central MO per latest trends in visible imagery. A residual outflow boundary is noted extending from the southern MO cumulus field southeastward into southern Middle TN. This may be a preferential corridor for storm clusters and/or a more organized MCS to propagate into during the late evening hours. While most CAMs appear to be too low with CI based on noted trends, several solutions hint at the idea of convection maintaining intensity into middle TN. Wind probabilities were nudged slightly southward to address this potential. See MCD #729 for more details on near-term trends. ....Texas Coastal Plains... A cluster of strong thunderstorms has initiation northwest of the Houston metro area. While radar trends suggest this convection is slow to mature, GOES IR imagery has shown persistent cloud top cooling consistent with intensifying storms. Consequently, this activity may pose an isolated severe hail/damaging wind threat through the late afternoon given favorable environmental buoyancy and modest, but perhaps adequate, deep-layer shear. A storm or two is plausible to the southwest of this activity along the TX coast, but a diminishing cumulus field under approaching cirrus suggest additional CI is unlikely in the near-term. ...Moore/Jewell.. 05/08/2023 ..PREV DISCUSSION... /ISSUED 1147 AM CDT Mon May 08 2023/ ....Ozarks to Lower Ohio Valley... A linear cluster of storms across western/central Kentucky has gradually trended downscale since early this morning but still otherwise continues to persist southeastward. To its west/northwest, the most confident scenario is for the front and lingering outflow boundary to focus later afternoon convective development from southern Missouri into southern Illinois, and eventually western Kentucky. Regional WSR-88D VWP data continues to sample a core of relatively strong, potentially rear inflow/convectively enhanced, mid-level winds in the wake of the MCS across southeast Missouri/western Kentucky/southern Illinois vicinity. Resultant 40+ kt deep-layer shear will tend to largely persist regionally and support organized updrafts, including some supercells and sustained multicells as storms redevelop later this afternoon. This should particularly be the case within the greater instability reservoir across southern portions of Missouri/Illinois. Significant severe hail will be possible with initial supercells given the rather steep mid-level lapse rates emanating east from the Great Plains. However, convection should quickly tend to grow upscale into clusters where the deep-layer shear vector is oriented more parallel to the front from the Ozark Plateau to the Lower Ohio Valley. As such, a mix of large hail and damaging wind should be the primary threats as clusters/MCSs spread east-southeastward towards the Tennessee Valley and central Appalachians tonight. ....Texas Rio Grande vicinity/Edwards Plateau/Low Rolling Plains... The dryline from the Big Country to the Edwards Plateau should support isolated thunderstorms from late afternoon to early evening. Unlike previous days, winds should be weak through much of the large buoyancy profile as stronger upper flow is displaced southeast of the dryline due to a low-amplitude upper trough. While isolated large hail/localized severe-caliber gusts are possible, the scenario suggests that convection should tend to be rather disorganized across the Low Rolling Plains into parts of the Edwards Plateau. A somewhat higher probability of severe storms (Slight Risk), nonetheless with a number of lingering uncertainties, appears to exist from the middle Rio Grande vicinity northward into southern parts of the Edwards Plateau, potentially aided by a weak mid-level disturbance currently over northern Mexico. Near-dryline convective development aside, this could also include the eastward propagation of storms across the Rio Grande this evening. The northwestward advection of a very moist air mass, as sampled by the 12z CRP sounding with 1.80 PW value and 15.4 g/kg mean mixing ratio, will support robust 4000+ J/kg MLCAPE across south-central Texas this afternoon. Very steep mid-level lapse rates (12z DRT observed sounding), ample buoyancy, and around 30 kt effective shear will support large hail/severe-caliber wind gusts where storms do develop later this afternoon into evening. ....South-Central Plains to ArkLaTex - Marginal Risk Areas... Several mechanisms for sustaining deep convection are apparent this afternoon and evening, offering a threat for generally isolated large hail and severe wind gusts. The trailing portion of the weak quasi-stationary front near the Oklahoma/Kansas border may be a focus for later evening slow-moving thunderstorm development. Additionally, a pair of MCVs, one drifting east from north-central Texas and the other drifting northeast near the Upper TX Coast should support downstream isolated to scattered thunderstorms, peaking in intensity this afternoon to early evening. Modest deep-layer shear coincident with the eastern fringe of the steep mid-level lapse rate plume should yield sporadic multicell clusters and foster a threat for lower-end intensities of severe hail/wind. ....Mid-Missouri Valley/Upper Midwest... A belt of enhanced mid-level westerlies will be maintained to the south of a low near the Minnesota/Ontario border drifting northwest into southern Manitoba. Despite an ill-defined surface pattern, robust boundary-layer heating from Kansas towards the Middle Missouri Valley should overlap with the western periphery of a lingering plume of 50s F surface dew points over Iowa. This may aid in isolated late afternoon to early evening thunderstorms. With light low-level winds, speed shear through the cloud-bearing layer will foster a moderately elongated straight-line hodograph. This will favor splitting discrete cells with mid-level rotation and potential for isolated large hail, and perhaps even a brief tornado risk across far southeast Minnesota/northeast Iowa near a residual weak boundary. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .