SPC AC 071249 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Sun May 07 2023 Valid 071300Z - 081200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PARTS OF THE MID-MO/MS VALLEYS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEST TX TO A PART OF THE RED RIVER VALLEY... ...SUMMARY... Scattered severe thunderstorms are most likely across parts of the central Great Plains to the Mid-Mississippi Valley from late this afternoon through tonight. Very large hail, destructive wind gusts, and a few tornadoes will be possible. ...Central Great Plains to the Mid-MS Valley... Extreme spread exists between the 06Z NAM and the 09Z RAP with the amplitude of warm/moist-sector buoyancy at peak heating in the wake of convective overturning across the southern Great Plains last night and a substantial residual dry pocket across much of OK and KS. The RAP maintains this dry pocket across the Lower MO Valley through the late afternoon versus the NAM showing near complete recovery. A plume of 65-70 F surface dew points is still present ahead of this dry pocket and should be maintained across the Mid-MS Valley, curling westward along a quasi-stationary front. The western extent of recovery from the TX Big Country should eventually reach eastern KS by this evening ahead of the dryline which will intersect the front near the southeast NE/northeast KS border. A small area of elevated convection is ongoing near the northeast NE/northwest IA border, well north of the surface front, and may persist east across portions of northern IA this morning with an isolated severe hail threat. How this activity evolves downstream this afternoon is unclear. Convective development appears most likely across the central High Plains within a weak low-level upslope flow regime downstream of a minor shortwave impulse approaching from UT. Additional storms will be possible farther east along and generally north of the quasi-stationary front into IA, but will become more probable towards evening as ascent increases with a strengthening low-level jet over eastern KS into MO. Some of these storms may remain elevated with a threat for large hail, but a slow-moving supercell or two immediately along the front should pose a tornado threat as well. The High Plains storms will likely intensify as they impinge on increasingly larger buoyancy with eastern extent, potentially including a long-tracked supercell or two capable of significant severe hail and wind. This activity will expand in coverage and/or merge with downstream supercells towards the MO Valley as ascent becomes maximized this evening. This should include evolution into an MCS which could contain bowing segments spreading towards southern IA/far northern MO vicinity tonight. Overall MCS intensity should gradually wane overnight as it moves into the Mid-MS Valley. ...TX vicinity... Convergence along the dryline is a bit nebulous to the northwest of a southern-stream mid-level impulse moving northeast across south TX to the Sabine Valley today. A cluster of severe thunderstorms will probably still develop along the west TX portion of the dryline during the late afternoon. With 500-mb west-southwesterlies only around 20-25 kts, supercell evolution should be erratic and outflow-dominant given the steep lapse rate environment. But the presence of low 70s surface dew points this morning across the Edwards Plateau will foster rather large buoyancy and threats for very large hail and significant severe wind gusts. A separate cluster of isolated severe thunderstorms may also develop ahead of the aforementioned southern-stream impulse. Its ascent is already aiding in ongoing elevated convection over south-central TX and this activity may produce isolated large hail this morning, while developing towards the Ark-La-Tex vicinity this afternoon. Despite hodographs having weaknesses in the 700-500 mb layer, a moderate combination of deep shear and instability could favor a few storms producing large hail and damaging winds during the afternoon. ...Mid-South/Lower OH Valley to Southern Appalachians... A ragged, south-southeast moving QLCS is ongoing across southeast IL to the central OH Valley, within a predominately west/east-orientation. This MCS will likely persist towards the southern Appalachians through this afternoon as low-level warm theta-e advection from the west continues. Western portions of the line may attempt to backbuild towards the instability plume across the Mid-MS Valley while the eastern portion may accelerate south-southeast amid weak instability. Occasional strong to locally severe wind gusts will be possible. Farther west, an MCV over northwest AR should track towards the MS/OH River confluence by this afternoon. Ample instability downstream of this MCV could foster an uptick in multicell clusters spreading east from the Mid-South, potentially merging with the western portion of outflow from the southward-moving MCS. Isolated to scattered damaging winds should be the main threat. ..Grams/Kerr.. 05/07/2023 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z CURRENT UTC TIME: 1407Z (10:07AM), RELOAD THIS PAGE TO UPDATE THE TIME
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