Storm Prediction Center Day 4-8 Severe Weather Outlook Page (2024)

SPC on Facebook

@NWSSPC

NCEP Quarterly Newsletter

 ZCZC SPCSWOD48 ALL ACUS48 KWNS 170858 SPC AC 170858 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Fri May 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... ...Day 4/Mon-Day 5/Tue -- Central/Southern Plains to the Midwest... Increasing southwesterly deep-layer flow will overspread much of the southern/central Plains by Monday afternoon/evening ahead of a deepening upper trough across the western U.S. Subtle lead shortwave impulses will eject across the KS/NE vicinity after 21-00z Monday night as a surface front drops southeast across the northern Plains. Rich boundary-layer moisture will spread northward across OK/KS as at least weak surface cyclogenesis occurs over the central High Plains. This overall pattern will support some severe potential somewhere from NE/KS/OK to the Lower MO Valley into early Tuesday. However, uncertainty remains given the subtle nature of ejecting shortwave impulses and the potential for ongoing convection Monday morning, leaving some questions over smaller-scale details. Nevertheless, enough consistency exists to introduce a 15 percent severe probability for Monday evening/overnight ahead of the surface front across portions of the central Plains vicinity. Given uncertainty, this area may shift in the coming days. On Tuesday, the upper trough is expected to eject east/northeast across the Plains to the Mid/Upper MS Valley. A deepening surface cyclone will lift northeast from KS to the Upper Midwest as the trough ejects over the region, and a cold front will push east/southeast. A very moist/unstable and favorably sheared environment will exist from eastern KS/OK to the upper Great Lakes ahead of the surface low and upper trough. Organized convection is expected across a broad area. This area likely will change some in coming days given mesoscale uncertainties tied to likely convection in the Day 4/Mon time frame continuing into Day 5/Tue. ...Day 6/Wed -- Ohio Valley to the Mid-South... By Wednesday the upper trough is forecast to lift northeast from the Mid/Upper MS Valley to Ontario/Quebec. Large-scale ascent will quickly shunt north of the international border. The surface cold front is expected to become more diffuse as the surface cyclone also shift north into Canada. Still, moderate deep-layer southwesterly flow will overspread a moist boundary layer across the Ohio Valley, and some severe potential may persist. Confidence is too low to include probabilities at this time, but may be needed in subsequent outlooks. With southward extent into the Mid-South vicinity, some severe potential could also persist given an expected moist/unstable airmass and potentially ongoing morning MCS. However, upper-level support will not be as favorable heading into the afternoon hours, and confidence is too low for severe probabilities at this time. ...Days 7-8/Thu-Fri... Forecast guidance is not in as good agreement by the end of the forecast period. The overall pattern may become less amplified and more quasi-zonal. However, some guidance does indicate at least some weak shortwave impulses migrating through westerly flow, particularly across the southern Plains vicinity. Trends will be monitored as a potential area of interest could develop across portions of the southern Plains around Day 7/Thu. ..Leitman.. 05/17/2024 CLICK TO GET WUUS48 PTSD48 PRODUCT