Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
705 ACUS02 KWNS 051711 SWODY2 SPC AC 051709 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Fri Jul 05 2024 Valid 061200Z - 071200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL PLAINS... ...SUMMARY... Severe thunderstorms are possible from southern South Dakota into the southern High Plains on Saturday, with the highest coverage expected in parts of Nebraska and Kansas. Large hail (some greater than 2 inches) and severe winds are the expected hazards. ...Central Plains into eastern NM... Modest height falls are forecast across the region as a broad upper trough persists across much of the central U.S. Several shortwave impulses are forecast to rotate through northwesterly flow aloft and will support areas of convection through the period. At the surface, a weak surface low may develop over western NE/KS, while generally surface troughing extending into southeast CO/northeast NM. Boundary-layer moisture will be modest across much of the region given prior cold frontal passages in the past few days. However, south/southeasterly low-level flow will allow for upper 50s to low 60s F dewpoints expanding northward across the southern High Plains into portions of KS/NE. Cool temperatures aloft and a plume of steep midlevel lapse rates spreading into KS/NE will support a corridor of moderate instability from the Raton Mesa vicinity north/northeast into western KS/central NE by mid-afternoon. Some forecast guidance suggests convection may be ongoing across parts of SD/NE. This introduces uncertainty in convective evolution/timing, as this activity may slowly increase in intensity through the day. Or, convection may dissipate and leave an outflow boundary across central NE. Confidence is higher that convection will develop further south into western KS and the southern High Plains in the vicinity of the surface through during the afternoon. Vertical shear will support initial high-based supercells. Steep low-level lapse rates and high temperature-dewpoint spreads amid mostly weak low-level flow will support strong/severe outflow winds. This may allow for storm consolidation into an east/southeast propagating MCS during the evening. If this occurs, damaging wind potential will increase. In the absence of a strong low-level jet during the evening, eastward extent of the severe risk should diminish into central KS with time. Initial supercell storms also will pose a risk for large hail, with some hail up to baseball size possible. With southward extent, vertical shear and large-scale ascent will weaken, and organized thunderstorm coverage should be somewhat lower into eastern NM and the TX Panhandle. ...Northeast and Mid-Atlantic... Showers may be ongoing Saturday morning across parts of NY and New England in a warm advection regime ahead of a cold front. This may limit heating and low-level destabilization into the afternoon. As a result, severe potential may be limited despite 35+ kt effective shear magnitudes and a very moist low-level airmass. A few strong gusts are possible, but confidence is too low to add unconditional severe probabilities at this time. Thunderstorms are expected with southward extent into eastern VA and the Carolinas ahead of the surface cold front. While stronger destabilization is expected with southward extent, vertical shear will be very weak. However, steep low-level lapse rates and high PW values may support a couple of strong wet microbursts in otherwise disorganized storm clusters. ..Leitman.. 07/05/2024 $$