CTP has a strongly worded forecast discussion this morning:
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.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
*Significant winter storm potential with heavy snow and minor
ice accumulation possible Sunday afternoon through Monday
afternoon
Coldest minT will be Saturday night with lows in the negative to
positive single digits from north to south. Light winds under
sfc high should cap wind chills at -5 to -10F over the northern
mtns or above advisory criteria.
A closed mid-level low pivoting across the Gulf Coast early
Sunday morning will begin to lift northeast and take on a
negative tilt across the southern Appalachians Sunday afternoon
and then race northeast to be over NJ by 12Z Monday. This will
be accompanied by an increasingly coupled jet structure
downstream of the pivoting trough, with intense ascent through
diffluence aiding in the development and then strengthening of a
low pressure system moving north to a nearly stacked position by
the end of D3. The guidance has come into much better
agreement with the placement of this low lifting roughly along
the I-95 corridor. As this low initially develops, mid-level
confluence over the Mid-Atlantic will help reinforce a wedge of
high pressure down the east side of the Appalachians in a
typical Cold Air Damming (CAD) setup.
As the low strengthens, moisture will surge northwestward
behind robust isentropic lift and likely produce a period of
moderate to heavy snow (WAA thump) early Sunday night (00-06Z
Mon). Mixed thermal profiles and possible dry slot are in play
into early Monday morning to the southeast of I-99/80 which
could transition snow to ice over the southeast part of the CWA.
While there are still some details to resolve, there is a
strong enough model signal to issue a well-collaborated winter
storm watch for most of the CWA from 18Z Sunday to 18Z Monday.
The multi-model/blended QPF and SLRs indicate potential for 6"
or more of snow with a minor ice glaze also possible across the
southeast 1/3 of the area.
Deformation snow appears to linger over the northern part of CPA
through Monday morning. The expected snowfall btwn 12-18Z
Monday was not included in the storm total with this cycle
given that it is beyond the set time window. Expect cold/gusty
NW flow to take over Monday night with deformation snow
transition to lake effect/upslope snow showers into Tuesday
morning.