Valid 261200Z – 271200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
The risk of severe thunderstorms appears negligible across the U.S.,
today through tonight.
Mid-level flow appears likely to remain broadly cyclonic across the
Mississippi Valley into the western Atlantic through this period.
Within this regime, a closed low, initially over the lower Great
Lakes/upper Ohio Valley vicinity at 12Z this morning, likely will
remain the most prominent feature. As a significant short wave
perturbation pivots around its southern and eastern periphery, it
appears likely to redevelop east-northeastward across northern New
England by the end of the period. As it does, a surface low
initially migrating northeastward near coastal Maine is forecast to
continue to deepen and become the primary associated surface
cyclone, with a trailing cold front continuing to advance away from
the Atlantic Seaboard, while stalling across or just south of the
southern Florida Peninsula into the northern Gulf of Mexico.
Models suggest that one or two smaller-scale perturbations emerging
from the southern Plains and lower Rio Grande Valley may contribute
to weak wave development along the front over the northern Gulf of
Mexico. With the progression of the mid-level features, the ongoing
inland moisture return off the northwestern Gulf of Mexico appears
likely to become cut-off/shunted southward into the Gulf. However,
before it does, destabilization (based above a stable layer near the
surface) may become sufficient for scattered weak thunderstorm
activity near north central Gulf coastal areas today into tonight.
Meanwhile, farther west, larger-scale troughing approaching the
Pacific coast early today is forecast to become increasingly
fragmented while progressing inland and across the Cascades and
Sierra Nevada, downstream of ridging building into the Pacific coast
by 12Z Monday. While relatively cold mid-level air will contribute
to potential for diurnal destabilization across the higher terrain
into the Intermountain West, relatively cool and/or dry conditions
in lower levels are forecast to allow for the development of only
pockets of very weak instability. While some convection capable of
producing lightning might not be out of the question over a fairly
broad area of the West, thunderstorm probabilities appear generally
less than 10 percent.