Interesting discussions from the NWS-Philly/NYC on the storm, with the NYC office noting the uncertainty in the modeling with regard to track and outcomes. Clearly, the operational models last night are showing an almost all rain event for the 95 corridor and the coast with a transition to some significant snow/sleet not too far inland N of 78 (and W of 287) and especially N of 80 (and W of 287) and up into the Poconos/western Hudson Valley before any changeover to sleet/rain, but there is still some chance of the ensembles being more correct and a snowier solution for 95. Today's models should have better data inputs, so we'll see. The one thing that I didn't mention last night as a risk is that in addition to the coastal flooding risk, there's likely going to be some high winds, especially near the coast (50-60 mph gusts possible).
Area Forecast Discussion
National Weather Service Mount Holly NJ
521 AM EST Thu Jan 13 2022
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
This system has the potential to yield multiple hazards across our
entire forecast area. The initial threat will be a period of snow
and/or sleet at the onset of precipitation, especially along and
north of the I-95 corridor. This currently appears to occur sometime
Sunday evening from south to north. Accumulating snow and/or sleet
is probable during this time, but a changeover to rain is expected
to race northwestward as strong warm air
advection ramps up. The
changeover to rain appears to reach to near or perhaps just south of
the I-78 corridor (definitely north of Philly though) in the pre-
dawn hours Monday as precipitation begins to move out of the area
(and also as a possible
dry slot moves in). More significant snow
and sleet accumulations are possible near and north of the Lehigh
Valley, but exact details on this remain to be seen at this time.
The second hazard of concern will be strong onshore winds. Within
the strong easterly pressure
gradient that develops Sunday evening,
guidance is all in fairly good agreement with onshore (easterly) 925
mb winds 50-60
kts inland to around the I-95 corridor and 60-70+
kts
over the ocean, but obviously there is a question as to how much of
this mixes to the surface. We`ve seen this kind of setup a couple
times within the past few years though. Nevertheless, this will
likely lead to a period of windy conditions, especially along the
coasts and across the coastal plain. Thinking gusts of 40-50 mph are
possible, with gusts near 60 mph possible near the coasts late
Sunday evening. We`ll have to keep a close eye on this potential of
impactful wind gusts. Went on the conservative side of guidance in
the forecast as a good amount of uncertainty remains with this.
A couple additional potential hazards to mention are fresh water and
coastal flooding. Fortunately, this system will be moving fairly
quickly, but storm total
QPF amounts of near or over one inch may be
possible. If this falls fast enough in areas where precipitation has
changed to rain, we could realize a localized excessive
rainfall
flooding threat. Lastly, our
coastal flooding forecasts are just
outside of the reach of this storm currently, but we do know that
the astronomical
tides will be running above
normal due to the full
moon on Monday. With a period of strong onshore winds, this could
result in some
coastal flooding issues, especially along the ocean
front. Again, something to keep an eye on at this point.
Area Forecast Discussion
National Weather Service New York NY
700 AM EST Thu Jan 13 2022
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A
deepening low over the Tennessee Valley Saturday night will track
along or just east of the Appalachians Sunday, taking a track to the
west of the forecast area late Sunday night into Monday. The 00Z
operational run of the
GFS,
ECMWF, and Canadian are in very good
agreement with the surface low track with about a 980
mb low
occluding just west of the area during this time. What has been odd,
is that the 00Z GEFS
mean and most of its member low tracks are
offshore, with the
mean passing near the 40N...70W
benchmark Monday
morning. About 24h ago, we saw this with both the GEFS and EPS.
However, the EPS and Canadian
ensembles are both now closely in line
with their operational counterpart.
Thus, unless we see some big change in the low track as the
Pac
energy comes onshore today, the forecast area will be on the warm
side of this system with a quick transition to rain at the coast and
a slower progression to rain for most inland locations. Locations
well north and west may be able to stay mainly snow (western half of
Orange) as the low occludes Sunday night and the area dry slots.
Coastal locations will see the
boundary layer warm quickly with a
strong E/SE
flow gusting in excess of 30 mph at coastal locations
Sunday night. The 00Z
GFS brings a 60 to 70
kt LLJ across coastal
locations during this time. In fact, Sunday morning lows will be in
the single digits for most locations, quickly rising through the day
with the
flow off the ocean.
The timing of the precipitation to begin looks to be late Sunday
afternoon/early evening at the coast and then quickly overspreading
the remainder of the area. For inland areas, there could be a quick
dump of
heavy snow, especially the farther north and west as one
goes. Strong
thermal forcing will be present as a warm, moist
conveyor belt off the Atlantic throws
moisture over a retreating
arctic airmass. Much of the global guidance is producing 1 to 1.5
inches of
rainfall through the event with
PWAT values approaching an
inch (90th percentile).
Warning level snow of 6 inches or more will
be possible from interior SW CT west across the Lower Hudson Valley.
Of course, any subtle track change will have impacts on how much
cold air is retained or eroded as the storm system approaches the
area.
