SPC May 9, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Sun May 09 2021 Valid 092000Z - 101200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM NORTHEAST TX INTO PARTS OF THE MID-SOUTH... ...SUMMARY... Scattered severe thunderstorms are expected from parts of central/east Texas into the lower Mississippi Valley and Mid-South. Large hail, damaging wind gusts, and a couple of tornadoes all appear possible. Other more isolated strong/severe storms may occur across the southern High Plains. ...

20Z Update... ...Central TX to middle TN through early tonight... Forecast outlined in the previous discussion (appended below) remains valid. Only change to the outlook was to adjust the western edge of the probabilities from the Arklatex into the Lower OH Valley based on the current position of the front. Widespread thunderstorms are still expected to develop along the front as it progresses southeastward into the unstable air mass extending from central TX into the TN Valley. Large hail (some potentially great than 2" in diameter), damaging wind gusts, and a tornado or two are all possible with these storms. Severe thunderstorm threat should last into the evening. ...

Northeast NM and vicinity this afternoon/evening... As mentioned in MCD 569...thunderstorms developing across northeast New Mexico and far southeast Colorado over the next few hours will pose a threat for damaging winds and perhaps isolated hail. ..Mosier.. 05/09/2021 .PREV DISCUSSION... /ISSUED 1121 AM CDT Sun May 09 2021/ ...

Central TX to middle TN through early tonight... A strong late season cold front is moving southeastward across OK/north TX, while outflow from overnight convection is sagging southward across northern AR. A plume of steep midlevel lapse rates is in place atop upper 60s to lower 70s boundary-layer dewpoints from TX into AR/LA ahead of the cold front, and this environment will spread some toward the Mid-South today. Surface-based thunderstorm development is anticipated by early afternoon along the front and remnant outflow from western TN across northwestern MS into southern AR, and storms will develop west-southwestward into TX along the cold front through mid-late afternoon as surface heating and low-level ascent along the boundary weaken convective inhibition. MLCAPE of 2000-2500 J/kg is expected ahead of the cold front to the west of the MS River this afternoon. Deep-layer shear will be sufficient for supercells and organized storm clusters capable of producing isolated very large hail and damaging winds, though weakening low-level shear through the day will tend to limit the tornado threat with westward extent. Farther east toward northwest MS and TN, low-level shear and warm advection will remain stronger later into the afternoon, within the southwestern extent of the low-level jet related to the surface cyclone and midlevel trough crossing the Mid MS/OH Valleys. Clouds and outflow with early convection will modulate the northeast extent of the primary severe threat into western/middle TN and northwestern MS. ...

Northeast NM and vicinity this afternoon/evening... Isolated thunderstorm development will be possible along the east edge of the higher terrain by mid afternoon in a post-frontal, upslope flow regime. Low-level moisture will be limited, but surface heating of the post-frontal air mass, in combination with sufficiently cool midlevel temperatures, will result in weak surface-based buoyancy. There will be sufficient buoyancy and vertical shear for a couple of high-based, low-topped storms with some supercell structure, and an attendant threat for isolated strong/damaging gusts and marginally severe hail (closer to the higher terrain). Read more LIVE: spc.noaa.gov

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