GSP
.LONG TERM /SATURDAY THROUGH MONDAY/...
As of 230 AM EST Tuesday: An active extended is in store as
models come into better agreement about a potent system entering
the eastern CONUS over the weekend. Deterministic guidance is
struggling to handle the system consistently, with the last 2 runs
of the ECMWF finally converging on a strong cyclone affecting
the Carolinas, even as latest run of the GFS begins to diverge
from this solution. The CMC has consistently depicted a
solution in line with the latest ECMWF. Such a solution would
result in cyclogenesis along a stalled frontal boundary south
and east of the forecast area, in turn producing a cyclone that
shifts east too quickly to appreciably warm 850mb temps. So,
precipitation develops atop bitterly cold low-level air,
resulting in an all-snow solution throughout Friday night and
much of Saturday.
About 75% of GEFS members now depict some amount of wintry precip
occurring with this system, indicating the latest dry solution from
the deterministic run is an outlier; nonetheless, there remains
significant uncertainty with the timing and intensity of this
system, as well as what, if any, accumulations could be expected
should another winter system actual materialize.
In any case, the upper pattern becomes much less perturbed behind
this system, and cold, dry air builds in at the surface. A weak
reinforcing cold front should arrive Monday evening, but looks
too dry to warrant any PoPs.