WLNG Weather

.KEY MESSAGES...
1.) Confidence increasing in a winter storm Sunday into Monday.

2.) Other than briefly moderate temperatures late today into
Thursday, a prolonged period of frigid temperatures is expected
through much of the forecast period. This will be the coldest
airmass of the season thus far.

.KEY MESSAGE 1...
The model guidance over the last day has begun coming into
better agreement on a potential winter storm impacting the area
Sunday into next Monday. The agreement amongst the
deterministic models and AI models is quite good for this time
frame as the event is still about 5 or so days out. The models
have all begun showing a northern stream shortwave phasing with
southern stream energy ejecting out of the southwest US this
weekend. Differences remain on the evolution of this
interaction, but deep subtropical moisture will overrun an
arctic air mass over the northern two thirds of the country. The
interaction of the two streams helps amplify the upper jet and
height field along the east coast to allow the low pressure
developing off the Middle Atlantic on Sunday closer to our
region. Guidance does diverge more heading into Monday on how
quickly the system departs and how close the low will get to the
coast into Monday.

While confidence in the storm system occurring continues to
increase, specific details on amounts are still a bit uncertain.
The latest NBM probability for greater than 6 inches of snow
ranges from about 50 percent inland to about 70 percent over
the NYC metro and coast. These probabilities have increased over
the last several cycles. The potential exists for the snow to
be drier and powdery based on the arctic air mass in place, but
these details will be worked out as the event draws closer.

The 00z ECMWF, EC-AIFS, UKMET, and to some degree the CMC have
shown even more amplification of the trough and bring the low
pressure off the Middle Atlantic much closer to Long Island.
This could potentially introduce some warming aloft as the
precip tapers off sometime Sunday night or Monday morning. This
would change the snow to a wintry mix. These details are to far
out to say with any confidence, but something to watch over the
coming days.

The bottom line here is that an impactful winter storm is
possible Sunday into Monday. The storm track, timing, and snow
amount details will begin coming into focus over the next few
days.

.KEY MESSAGE 2...
High pressure over the area today will shift east allowing for a
southerly flow to advect more moderate air over the area as a
weak warm front moves through. This will allow temperatures
today to increase a bit into the 30s late today into tonight.
There will also be a chance of rain or snow showers with this
warm front as it passes through late afternoon into the evening.

Temperatures continue to increase under SW flow Thursday with
highs climbing into the 40s across the CWA. A cold front moves
through Thursday night advecting colder and drier air into the
area. Highs Friday will be around freezing along the coast and
upper 20s inland. Behind another cold front Friday night, an
arctic high pressure advects frigid temperatures into the area
through the rest of the forecast period. Minimum wind chills
Friday night are expected to be from 0 to -15 degrees which may
warrant cold weather headlines.

The frigid airmass allows for sub-freezing temperatures through
at least the middle of next week with high temperatures this
weekend not climbing out of the teens for the entire CWA. Lows
at night Friday night through at least Wednesday night will be
in the single digits or low teens for the entire area.

.MARINE...

Sub-SCA conditions will persist on all waters through this
afternoon. Increasing winds will bring SCA conditions on the
ocean, Great South Bay, and Eastern LIS with gusts around 25 kt
this afternoon and through much of the night. SCA conditions may
spread over the non-ocean waters on Thursday with marginal
small craft conditions likely remain for the ocean through
Thursday night.

An Arctic cold frontal passage Friday afternoon should then bring
SCA conditions to all waters Friday afternoon/night, with W-NW flow
gusting to 25-30 kt and occasional gusts to 35 kt on the ocean, and
seas 5-7 ft.

There may be lull in SCA conditions on the waters late Saturday
through Sunday morning before gusts pick back up to SCA
thresholds on the ocean Sunday afternoon through the night.