Mt Holly morning AFD:
As we go through Thursday night and Friday, the southeastward
progression of the arctic front occurs and this will be key in
the timing of the initial shallow cold air seeping eastward. A
sharp temperature gradient will exist with this front, and at
least a couple ripples of low pressure will be tracking along
it. Along and north of the wave and west of the front,
temperatures will drop rapidly supporting rain changing to
freezing/frozen precipitation. The temperature drop could also
start resulting in a rapid freeze-up across our western zones
especially during the day. The model forecast soundings indicate
the low levels quickly cool with a deep warm layer aloft
gradually cooling with time. This points to a period of freezing
rain then to sleet then to snow before ending. The guidance is
trending faster with the colder air arriving, although the GFS
still looks to be the coldest. We went ahead and sped up the
colder air arriving and therefore a quicker changeover
occurring. Some fog may occur for a time as the warmer air along
with higher dew points move over especially lingering
snowcover, although this may be limited due to the presence of a
strong low- level jet.
It looks like the guidance is coming into some better
agreement, however there remains uncertainty regarding how
quickly the low- level cold spreads southeastward during Friday.
The greatest chance for a more prolonged period of
freezing/frozen precipitation will be from the I-78 corridor
northward. As are result, some accumulating ice is expected
across these areas. Some snow/sleet accumulation is expected
although the snow amounts look to be limited. This however will
depend on how quickly the warm layer aloft erodes and how much
moisture remains before ending. We continue to think this looks
like an advisory level event for parts of our area, however
amounts will depend on the cooling of the column and amount of
precipitation falling after colder air arrives. There is an
increasing chance now that the rain changes to some freezing
rain, sleet and/or snow into the I-95 corridor and possibly to
the coast before ending.