SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Fri Aug 11 2023 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE OH VALLEY AND NORTHEAST STATES...AND THE SOUTHERN/CENTRAL HIGH PLAINS... ...SUMMARY... Severe thunderstorms are possible across portions Ohio Valley and Northeast States, and southern/central High Plains on Saturday. ...Synopsis... A low-amplitude shortwave trough will likely begin the period over the Upper Great Lakes, within a belt of stronger mid-level flow extending from the northern High Plains through the Upper Great Lakes and OH Valley into the Northeast. This shortwave is forecast to continue eastward into eastern Ontario and throughout the day as several vorticity maxima progress through its base. Another shortwave trough is expected to drop through the northern High Plains early Sunday morning. At the surface, a low associated with the Great Lakes shortwave trough is expected to move eastward across eastern Ontario and far southern Quebec, with an attendant cold front pushing eastward across PA and NY throughout the day. Elsewhere, upper ridging will persist across the southern Plains and Southeast, and an upper low will drift slowly eastward towards central/southern CA. ...Northeast... A moderately moist airmass is expected to be in place ahead of the approaching shortwave trough and attendant cold front. Early day warm-air advection showers are expected, with at least some potential for these storms to become surface based as the downstream airmass destabilizes during the late morning/early afternoon. Additional thunderstorm development is possible along and within the warm sector ahead of the front. Strengthening mid-level flow will contribute to moderate vertical shear, increasing the potential for organized storms. A mix of discrete storms and bowing line segments appears likely, with at least some potential for a coherent convective line along the front. All severe hazards are possible, with damaging gusts as the main threat within any bowing segments. More discrete storms could produce large hail and perhaps even a tornado. ...OH Valley... A large amount of the guidance has trended towards the development of an organized convective line late Friday, which then moves into the Lower OH and TN Valleys early Saturday morning, posing a low-end wind threat. Cloud cover associated with this system could limit destabilization across the Lower/Mid OH Valley until later in the afternoon. With the primary forcing farther north, only modest ascent is anticipated across this area. This limited forcing combined with tempered destabilization should keep storm coverage isolated across IL and IN. Greatest storm coverage is expected across OH and PA where the large-scale forcing is forecast to be a bit stronger. Moderate vertical shear will be in place areawide, and a few organized storms capable of hail and/or damaging gusts are possible. Veered low-level flow should limit the tornado risk, but there is low-probability threat, particularly with any storms that interact with previous outflow or lake-induced boundaries. ...Southern High Plains into the Central Plains... Post-frontal easterly flow is expected to strengthen throughout the day across from southwest KS into northeast NM and southeast CO, with resulting low-level moisture advection helping to offset mixing. Afternoon thunderstorm development is anticipated across the Raton Mesa vicinity, with high cloud bases and steep low-level lapse rates favoring outflow-dominant storm structures. These storms then moving eastward into the region where 60s dewpoints and moderate buoyancy are expected to be in place. Vertically veering wind profiles will also contribute to moderate deep-layer shear over the region. Expectation is for these storms to undergo upscale growth/cold pool amalgamation as they move into southwest KS and the OK/northern TX Panhandle, with an attendant threat for damaging gusts. ...SD/NE... A strengthening low-level jet and associated warm-air advection are expected ahead an approaching shortwave trough and attendant surface low/cold front across NE and SD late Saturday evening. This warm-air advection will likely support thunderstorm development amid westerly flow strong enough for updraft organization. Some isolated large hail is possible with initial development, with a trend toward outflow-dominant storm structures and occasional damaging gusts thereafter. ..Mosier.. 08/11/2023
