Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
111 ACUS48 KWNS 200835 SWOD48 SPC AC 200834 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0334 AM CDT Mon May 20 2024 Valid 231200Z - 281200Z ...DISCUSSION... ...Day 4/Thu - Great Plains... A weak upper shortwave trough is expected to spread east from the southern Rockies to the Mid-South on Thursday. As this occurs, a band of enhanced southwesterly flow will overspread parts of OK and the ArkLaTex vicinity. A very moist airmass will be in place as southerly low-level flow maintains upper 60s to low 70s F dewpoints. This will aid in strong to extreme instability across portions of the southern Plains/ArkLaTex. While convective evolution is a bit uncertain, the overall pattern will support severe-thunderstorm potential. A potent shortwave upper trough will move across the northern Rockies to the northern Plains. As this occurs, a surface low will deepen and move from the northern High Plains eastward across the Dakotas. Some severe potential may accompany this system. However, boundary-layer moisture will likely be poor given a prior cold frontal passage and better-quality moisture return only making it as far north as KS or southeast NE. Low-end severe probabilities may be needed in future outlooks, but potential appears too low for a 15 percent delineation at this time. ...Days 5-8/Fri-Mon... Spread among forecast guidance increases Day 5/Fri and beyond. However, a general pattern where subtle upper shortwave troughs emanate from the Rockies into the Plains and central U.S. will likely continue. Forecast guidance varies in timing and location of these features, but at least some severe-thunderstorm potential will be possible from portions of the Plains into the Midwest/Mid-South vicinity through the weekend. Given uncertainty, confidence is too low to introduce 15 percent probabilities for any given area at this time. ..Leitman.. 05/20/2024