LWX AFD
Dramatic shifts in guidance over the past 12 hours for a
potential snowstorm tonight through midday Monday for the
southern half of our CWA, bisecting very close to the major
metropolitan areas.
Digging H5 trough over the southern plains will amplify today,
cut-off an upper low tonight over the Carolinas, then go
negative tilt as it crosses the mid-Atlantic coast Monday
morning. The reflection at the surface will be the development
of low pressure, rapidly deepening and tightening tonight over
the southeast US to a position over Cape Hatteras by daybreak
Monday. At the same time, cold Canadian air will quickly filter
in aloft, bringing H85 temps well below 0C for much of the
entire CWA by 12Z Monday.
00Z GFS, ECMWF, NAM all have at least advisory level snowfall
accumulations essentially south of I-66/US-50. 05Z NBM, which
was followed closely in development of snowfall accumulations
this morning, dampens the largest snowfall contributor -- the
GFS, and splits the difference between that model and the
lesser accumulating NAM. Because of the large variations and
the dramatic shift in guidance, advisories have been issued west
of I-95 where the precipitation onset will start shortly after
midnight tonight, and watches issued along and E of I-95. There
will be a tight gradient of snowfall accumulation north of the
Nation's Capital, and potential warnings and advisories will
most certainly be modified as guidance hopefully converges with
a solution over the next 12 hours.
The most likely snowfall forecast should be used with caution,
with probabilities of higher amounts, towards the 90th
percentile, should strongly be considered for planning
purposes. Please continue to check back as we modify this
forecast in the coming hours.