NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Feb 24, 7:03 PM EST, 1 hour 57 minutes earlier.
Area forecast discussion, Feb 24, 7:03 PM EST, 1 hour 57 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
703 PM EST Thu Feb 24 2022
.SYNOPSIS...
Low pressure will slowly deepen while moving across the Middle
Atlantic area tonight and then into New England Friday. Following
the low, an area of high pressure builds in for the first part of
the weekend. A cold front will cross the region Sunday. More high
pressure moves across the area for the beginning of next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
First area of precipitation has tapered off and moved offshore.
Some light precipitation is moving through southern New Jersey
and portions of Delmarva, but that should end shortly with few,
if any, impacts.
Otherwise, the main event remains tonight and into Friday
morning. A wave of low pressure will track out of the Ohio
Valley tonight and into Pennsylvania by Friday morning, in
response to a fairly robust shortwave ejecting out of the Plains
and towards the eastern Great Lakes. As the primary low passes
just to the west, a weak secondary coastal low is likely to
form just offshore of the New Jersey coast on Friday morning.
This complex system will bring a wintry mix of precipitation to
the region.
With the primary low tracking to our west, warm air advection
aloft will occur over the area. And with a strong parent
shortwave and potent southwesterly LLJ ahead of the low, warm
advection will be quite strong. However, a strong center of high
pressure to the north will help keep colder air entrenched near
the surface. Some evaporational cooling effects will also occur
once steadier precipitation moves in. The eventual development
of the secondary low will also act to back the winds and attempt
to draw cooler air into the region north of the new low.
Trends in guidance today were generally warmer with the overall
evolution of the storm, especially aloft. The NAM has been
leading the charge in this camp, and while it may be a little
too aggressive bringing in the warmer air aloft, the other
guidance seems to be playing catch-up to it. With the strong
shortwave and good jet dynamics in play, it makes sense that the
primary low would track a little further west (more amplified)
and lead to stronger warm advection. However, there was less
change in the surface temperature forecast, as low level cold is
always very difficult to dislodge, and a prolonged period of
wintry precipitation is still expected. The end result was less
snow and more sleet in the forecast, and still several hours of
freezing rain for many areas as well.
No changes were made to the Winter Weather Advisory. While snow
amounts came down, ice amounts remained very similar or locally
ticked up slightly. It will be somewhat marginal closer to the
I-95 corridor, but by and large have good confidence in
accumulating ice and associated travel impacts for all areas
within the advisory. Greatest impacts will be from midnight
tonight through the Friday morning commute hours, though the
change to rain will occur sooner closer to the urban corridor,
and the timing of the Advisory is staggered as such. Some very
brief icing may occur south and east of the advisory area
initially, but should yield little to no impact and was not
inclined to expand the advisory further.
The system is fairly progressive and should depart the region
late Friday morning into the afternoon. Areas of low clouds or
fog are possible in the morning as the flow temporarily becomes
light while the secondary low begins to take shape. As the
system pulls away, afternoon clearing is expected with daytime
highs rising into the 40s and low 50s in most areas, helping to
melt any ice. Also, as the low departs, winds will become gusty
for a time. Most guidance indicates westerly winds of 50 to 60
kt at 850 mb Friday afternoon. As we clear out, mixing will
improve, and we'll begin to tap into some of that wind. Raised
the surface gusts into the 25 to 30 kt range, and it's possible
they could be a little higher for a time. This flow will also
start to bring in cooler air with temperatures dropping by late
afternoon or early evening.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Zonal flow aloft Fri night and Sat begins to buckle a bit for the
last part of the weekend as a trough moves across eastern Canada and
the Northeast. A cold front will cross the area Sunday ushering in
more chilly temps for early next week. Little in the way of any
precip is expected, but a couple shower across the southern Poconos
can't completely be ruled out Sun, where we have slight chc pops
attm.
Temperatures will be cool Fri night/Sat then go back close to normal
for Sun before the front passes thru. More cold temps for Sun
night/Mon morning with teens across the north and 20s elsewhere.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Not much eventful weather in the long term. The upper trough across
Canada and the Eastern U.S. persists and even strengthens a bit
towards midweek. This trough weakens and moves away Thu/Fri so
after a mostly below normal week for temperatures, milder
conditions could arrive for the first weekend of March.
Precipitation will be scarce next week with sfc high pressure in
control much of the time. A weak low and front could arrive
(around) Wed and perhaps bring some precip (mainly) to the
northern parts of the region. Little confid in this, attm so no
mentionable pops in the fcst/grids attm. Better chcs for pcpn
next weekend.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight...VFR initially, then lowering to IFR, with most of the
area IFR by 06z or soon after. A mixed bag of precipitation is
expected. South of PHL, it should be mainly rain. PHL itself
could have a short period (1 to 3 hours) of freezing rain or
sleet before a change to all rain. North of PHL and especially
towards RDG and ABE, a longer period of sleet and freezing rain
is expected before the change to rain. Sleet and freezing rain
will likely fall for much of the night in those areas. CIGs and
VSBYs could decrease further late in the night especially from
PHL southward as fog may develop. Areas of LIFR conditions are
likely. Winds mainly east-northeast at 5 to 10 kt but may become
light and variable late in the night especially near and south
of PHL. Moderate confidence.
Friday...Initially, IFR to LIFR in lingering rain, low clouds,
and fog. Precipitation should gradually end through the morning.
Clouds will begin to break in earnest towards midday and early
afternoon, and VFR conditions should return for much of the
afternoon. Light winds in the morning, mainly from the east-
northeast. Winds shifting to southwest then west-northwest
through the day. Gusty west-northwest winds possible by
afternoon with speeds of 15 to 20 kt and gusts to 30 kt. Some
LLWS possible in the morning mainly near MIV and ACY, but not
yet enough confidence to include in the TAF. Moderate confidence
overall.
Outlook...
Fri night thru Sat night...Mostly VFR.
Sunday...VFR. A few showers possible far N/W.
Sun night thru Tue...VFR expected.
&&
.MARINE...
Through tonight... Mainly sub-SCA conditions expected. East-
northeast winds around 15 kt with gusts to 20 kt. Isolated gusts to
25 kt are possible by late tonight especially for the waters of
northern New Jersey. Seas 3 to 4 ft. Rain likely.
Friday... SCA conditions are expected to develop. A shift in winds
from east to southwest to west-northwest is expected as the day
progresses. As winds become more westerly, speeds will increase.
Winds of 15 to 25 kt with gusts to 30 kt are expected. There is a
chance for some 35 kt gusts especially for the Atlantic coastal
waters of New Jersey. Not enough confidence in it to upgrade to a
Gale Warning at this stage, but we will monitor trends in the wind
forecast. Rain likely in the morning. Seas 3 to 5 ft.
Outlook...
Fri night...Winds and seas decreasing back below SCA overnight.
Fair.
Sat/Sat night...sub-SCA expected. Fair.
Sun/Sun night...low-end SCA probable. Fair.
Mon thru Tue...sub-SCA. Fair.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 1 PM EST Friday for PAZ054-055-
060>062-105.
Winter Weather Advisory until 4 AM EST Friday for PAZ070-071.
Winter Weather Advisory until 10 AM EST Friday for PAZ101>104-
106.
NJ...Winter Weather Advisory until 1 PM EST Friday for NJZ001-
007>010.
Winter Weather Advisory until 10 AM EST Friday for NJZ012-015.
DE...Winter Weather Advisory until 4 AM EST Friday for DEZ001.
MD...None.
MARINE...Small Craft Advisory from 10 AM Friday to 6 AM EST Saturday
for ANZ450>455.
Small Craft Advisory until 10 PM EST this evening for ANZ454-
455.
Small Craft Advisory from 10 AM Friday to 1 AM EST Saturday
for ANZ430-431.
&&
Synopsis...O'Hara
Near Term...MPS/O'Brien
Short Term...O'Hara
Long Term...O'Hara
Aviation...MPS/O'Brien/O'Hara
Marine...O'Brien/O'Hara