From RAH:
All of the above factors combined with bitterly cold and dry air
continuously being drawn south into the Carolinas from the Arctic
high moving east from the Great Lakes into Upstate NY are likely to
result in a moisture-laden and potentially long lasting winter storm
across central NC from Saturday into Sunday. Precipitation will move
in from the west on Saturday morning and afternoon, potentially on
the lighter side initially, with the heaviest likely on Saturday
night and early Sunday, tapering off from west to east sometime
Sunday afternoon into Sunday night. There is still uncertainty on
timing with the 12z ECMWF a bit slower compared to the GFS. GFS and
ECMWF ensemble mean QPF is generally in the 1.5 to 2 inch range, and
with very cold air firmly entrenched at the surface, all of it is
likely to be frozen across central NC, whether that be snow or ice.
The main question that has to be answered is how strong the push of
warmer air is several thousand feet above the surface, which almost
always occurs in these setups across central NC. The latest GFS is
farther south with the 850 mb front and thus depicts more snow
compared to the ECMWF, but this has been going back and forth, and
their ensemble guidance has generally been a bit warmer/less bullish
with snowfall. So an all snow event across the entire region is very
unlikely, but the most favored area for that climatologically would
be along and north of the I-85 corridor. This is where NBM
probabilities for 6+ inches of snowfall are in the 60-80% range.
Meanwhile NBM probabilities of 0.25+ inches of freezing rain are in
the 60-80% range across the southern Piedmont, Sandhills, and
central/southern Coastal Plain. Significant accumulations of sleet
will also be possible between where the highest freezing rain and
snow amounts are. In addition to major travel issues, significant
tree damage and power outages may occur especially where the highest
ice accumulations occur. While details on specific amounts are still
uncertain, confidence is increasing in a major winter storm across
central NC, and it is imperative to continue staying tuned for the
latest updates as the forecast is likely to change.
