12AM Day 2 Convective Outlook for Sunday, July 13. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM VIRGINIA INTO NEW YORK AND EASTERN OKLAHOMA INTO SOUTHERN MISSOURI
SUMMARY
Marginally severe thunderstorms producing strong wind gusts will be possible across the eastern U.S. from the mid-Atlantic region northward into upstate New York. Additional isolated strong storms may occur from eastern Oklahoma into southern Missouri.
Discussion
Broad cyclonic flow aloft will envelop the northern Plains to the Northeast as an upper shortwave trough meanders east while de-amplifying on Sunday. Over the southern Plains, a weak upper low may stall over the region.
A seasonally very moist boundary layer will extend across much of the southern Plains to the Midwest and into the Eastern Seaboard, providing areas of moderate instability. However, stronger vertical shear will remain displaced to the north, near the international border, limiting overlap of instability with wind profiles sufficient of organized severe convection. Furthermore, heavy rain across parts of the southern Plains is forecast for Saturday/Day 1. This may dampen stronger heating and result in poor lapse rates, limiting overall severe potential. While some gusty winds are possible across the broad moist warm sector from the southern Rockies into the Mid-MS/Lower OH Valley vicinity, weak deep-layer flow and a lack of any discernible mechanisms to focus/organize thunderstorm activity should limit overall severe potential and the Marginal risk (level 1 of 5) has been removed for much of the region. The exception is across portions of OK into southern MO on the eastern periphery of the weak upper low and a possible MCV from convection in the Day 1/Saturday period. This feature may provide some local focus/enhancement to shear and a couple of strong to severe storms producing gusty winds will be possible.
Some greater potential for strong wind gusts still appears possible across parts of the VA into NY. Stronger heating will support steepened low-level lapse rates within the very moist and unstable airmass, and sporadic wet microbursts may occur. Some modestly enhanced westerly flow across PA/NY may aid in development of propagating clusters/outflows as well, and the Marginal risk (level 1 of 5) remains largely unchanged from the prior Day 3 outlook.