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2/6-7: Clipper Pack Refresher


bncho
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Afternoon AFD from LWX 

KEY MESSAGE 2...A potent winter storm with multiple hazards is
likely to impact the region Friday into the weekend.

A potent upper trough and Arctic cold front are set to track across
the region Friday into the weekend.

Ahead of the front, a leading shortwave trough quickly traverses our
area during the day Friday, which could bring a burst of snow east
of the Alleghenies. Accumulating snow along/east of I-81 will have
to contend with more marginal temperatures in the low to mid 30s.
However, the strong cold air advection and substantial lift in the
DGZ could possibly overcome any marginal temps at the surface. Stay
tuned to the forecast in the coming days for any possible impacts
from snow on Friday.

For the mountains, a steady period of moderate to possibly heavy
snow is possible, with several inches of accumulating snow being
noted in much of the model guidance. Additionally, the increasing
winds will lead to blowing snow and reduced visibility issues. Snow
squalls are possible Friday evening into Friday night as the base of
the upper trough slams into the Alleghenies. This is a very
favorable synoptic setup for upslope snow, though it is going to
be short-lived as forcing quickly departs, and moisture is more
limited due to abundant ice cover on Lake Erie and Lake Huron.

As the upper trough digs right over our area Friday night, it
is likely to induce a sudden onset of windy conditions,
especially in the wind-favored climo areas (mountains &
along/north of I-66). The 500mb height fields in the ECMWF and
GFS show intense ripples within a very sharp gradient over the
Appalachians - a signal that usually leads to mixing of stronger
winds aloft with northwesterly downslope winds. Most of the
guidance has wind gusts of 35-45 mph across the area, with 45-55
mph in the mountains. Higher gusts are noted in the ensemble
guidance, thus Wind Advisories and High Wind Warnings may
eventually be needed for parts of the area.

Frigid temperatures return to the area for this weekend, with highs
in the teens to 20s each day (maybe getting to around freezing in
parts of central VA). Lows Saturday morning drop to the teens, then
likely see single digits to low teens areawide for Sunday morning.
Wind chills are going to be in the low single digits to -5F or lower
each night, with -10F to -20F in the mountains.

Interestingly, the GFS has a progressive clipper passing
through on Sunday that could bring additional light snow, but
confidence in that is very low given model uncertainty.
Otherwise, dry and cold conditions prevail this weekend into the
start of next week.
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Mount Holly Snippet-

KEY MESSAGE 3...An arctic cold front will bring a shot of snow (and potential snow squalls) on Friday Night, with strong winds expected in the wake of the front on Saturday. A clipper system will slide by to the north on Friday Night, dragging a cold front through our area. This front looks to pack a bit of a punch as it moves through. Medium range guidance continues to show a shot of snow as it moves through. Global deterministic guidance is not the best at depicting snow squalls, however from a pattern recognition standpoint, it would be not be a surprise for some snow squalls to develop as the arctic front moves through. Better confidence for the snow-squall potential will come once we get in range of the CAMs, but a quick inch or two of snowfall is certainly possible on Friday evening/Friday Night along with the usual impacts from snow squalls (gusty winds, reduced visibility, brief heavy snow).

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1 hour ago, CAPE said:

Mount Holly Snippet-

KEY MESSAGE 3...An arctic cold front will bring a shot of snow (and potential snow squalls) on Friday Night, with strong winds expected in the wake of the front on Saturday. A clipper system will slide by to the north on Friday Night, dragging a cold front through our area. This front looks to pack a bit of a punch as it moves through. Medium range guidance continues to show a shot of snow as it moves through. Global deterministic guidance is not the best at depicting snow squalls, however from a pattern recognition standpoint, it would be not be a surprise for some snow squalls to develop as the arctic front moves through. Better confidence for the snow-squall potential will come once we get in range of the CAMs, but a quick inch or two of snowfall is certainly possible on Friday evening/Friday Night along with the usual impacts from snow squalls (gusty winds, reduced visibility, brief heavy snow).

Didn't an event similar to what might be coming up happen during the winter of 14 15 or 13 14. A very robust cold front went through with a period of snow squalls  that left about an inch or two of snow in a  extremely short period of time.

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2 hours ago, yoda said:

Afternoon AFD from LWX 

KEY MESSAGE 2...A potent winter storm with multiple hazards is
likely to impact the region Friday into the weekend.

A potent upper trough and Arctic cold front are set to track across
the region Friday into the weekend.

Ahead of the front, a leading shortwave trough quickly traverses our
area during the day Friday, which could bring a burst of snow east
of the Alleghenies. Accumulating snow along/east of I-81 will have
to contend with more marginal temperatures in the low to mid 30s.
However, the strong cold air advection and substantial lift in the
DGZ could possibly overcome any marginal temps at the surface. Stay
tuned to the forecast in the coming days for any possible impacts
from snow on Friday.

For the mountains, a steady period of moderate to possibly heavy
snow is possible, with several inches of accumulating snow being
noted in much of the model guidance. Additionally, the increasing
winds will lead to blowing snow and reduced visibility issues. Snow
squalls are possible Friday evening into Friday night as the base of
the upper trough slams into the Alleghenies. This is a very
favorable synoptic setup for upslope snow, though it is going to
be short-lived as forcing quickly departs, and moisture is more
limited due to abundant ice cover on Lake Erie and Lake Huron.

As the upper trough digs right over our area Friday night, it
is likely to induce a sudden onset of windy conditions,
especially in the wind-favored climo areas (mountains &
along/north of I-66). The 500mb height fields in the ECMWF and
GFS show intense ripples within a very sharp gradient over the
Appalachians - a signal that usually leads to mixing of stronger
winds aloft with northwesterly downslope winds. Most of the
guidance has wind gusts of 35-45 mph across the area, with 45-55
mph in the mountains. Higher gusts are noted in the ensemble
guidance, thus Wind Advisories and High Wind Warnings may
eventually be needed for parts of the area.

Frigid temperatures return to the area for this weekend, with highs
in the teens to 20s each day (maybe getting to around freezing in
parts of central VA). Lows Saturday morning drop to the teens, then
likely see single digits to low teens areawide for Sunday morning.
Wind chills are going to be in the low single digits to -5F or lower
each night, with -10F to -20F in the mountains.

Interestingly, the GFS has a progressive clipper passing
through on Sunday that could bring additional light snow, but
confidence in that is very low given model uncertainty.
Otherwise, dry and cold conditions prevail this weekend into the
start of next week.

Isn’t it just gonna cold with some snow showers? Where is the potent winter storm?

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