SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 AM CST Mon Nov 23 2020 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN/CENTRAL PLAINS...OZARKS...MID-SOUTH...AND LOWER MISSISSIPPI VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms may occur Tuesday into Tuesday night across portions of the southern/central Plains, Ozarks, Mid-South, and lower Mississippi Valley. Damaging winds should be the main threat, but a couple tornadoes and marginally severe hail also appear possible. ...Southern/Central Plains into the Ozarks, Mid-South, and Lower Mississippi Valley... An upper trough/low initially centered over the Four Corners region will progress eastward across the southern/central Plains by Tuesday evening, eventually reaching the lower/mid MS Valley by the end of the period. A 40-50+ kt southerly low-level jet will be present over much of the southern/central Plains Tuesday morning, with this feature forecast to likewise shift eastward through the day. Partially modified Gulf moisture will be transported northward across the southern/central Plains ahead of a developing surface low over KS and trailing cold front. A dryline should also mix eastward through the day across parts of western/central OK and north-central TX. Modestly steepened mid-level lapse rates (around 7-7.5 C/km in the 700-500 mb layer) should overspread the warm sector across the southern/central Plains as the upper trough/low moves eastward. There remains some model disagreement regarding how quickly and far north mid/upper 50s to low 60s surface dewpoints will reach by late Tuesday afternoon. The degree of low-level moisture return will have a large impact on how much surface-based instability can be realized ahead of the cold front/dryline across southern KS and central/eastern OK. Most guidance indicates that only weak instability (MLCAPE generally less than 1000 J/kg) will develop across these areas by peak afternoon heating. Still, a strong (60-70+ kt) southwesterly mid-level jet should overspread the warm sector through the day, which will support more than enough deep-layer shear for organized storms. Convection may initiate by Tuesday afternoon in close proximity to the upper low and left exit region of the mid-level jet in southwestern/south-central KS. With cold mid-level temperatures present, this activity should mainly pose an isolated threat for marginally severe hail. Modest low-level moisture and instability will probably limit a greater severe risk with northward extent in KS. Additional storms may develop by early Tuesday evening along/east of the dryline in central OK. All severe hazards appear possible with this convection, but uncertainty regarding how unstable the airmass across the warm sector will become currently precludes greater severe probabilities across central/eastern OK and vicinity. From Tuesday evening though early Wednesday morning, storms may grow upscale into a line along or just ahead of the eastward-moving cold front. Given the strength of the southwesterly low-level flow and potential for weak surface-based instability ahead of this line, isolated damaging winds may continue to be a threat through the end of the period across parts of the Ozarks, Mid-South, and lower MS Valley. An embedded tornado or two also cannot be ruled out with very strong 0-1 km SRH forecast. This isolated/marginal severe risk becomes more uncertain with northward extent into MO and the Mid-South, where very strong low-level flow will be present, but instability appears meager at best. Adjustments have been made to the eastern extent of the Marginal risk area across the Mid-South and lower MS Valley to account for the probable location of strong to locally severe storms by the end of the period. ..Gleason.. 11/23/2020
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