NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Mar 12, 6:13 AM EST, 2 hours 47 minutes earlier.
Area forecast discussion, Mar 12, 6:13 AM EST, 2 hours 47 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
613 AM EST Sat Mar 12 2022
.SYNOPSIS...
A strong low pressure system will affect the area today, bringing
rain then snow, before strong northwest flow develops later today
through Sunday. High pressure builds across the southeast states on
Sunday, then offshore Sunday night. A weak frontal boundary is
forecast to move across the area on Tuesday, before a coastal system
passes near or south of the region late Wednesday into Thursday.
&&
.NEAR TERM /THROUGH TONIGHT/...
...WINTER STORM TO AFFECT THE REGION TODAY...
Steady precipitation is overspreading the region this morning as
strengthening low pressure begins its trek up the East Coast.
Widespread low clouds and some fog are also in place thanks to
light southeasterly flow. Precipitation is falling as mainly
rain for now, though surface observations indicate the
approaching cold front has already moved into the Poconos and
will continue to progress southeast, with rapid temperature
drops and rain changing to snow occurring behind the front. The
quick moving low to our southwest will continue to strengthen as
it passes over or just east of the region today. Its
intensification will be supported by a vigorous mid- level
trough beginning to pivot to a more neutral orientation, as well
as extremely strong upper jet dynamics which will easily allow
the developing low to achieve bomb cyclone criteria by tonight.
Regarding the local forecast, the main change overnight, while not a
huge change, was a continuation of the trends from yesterday. The
track of the low continues to push a little further east, resulting
in a faster transition to snow for eastern Pennsylvania and northern
New Jersey. This has resulted in higher snow totals nudging a little
further southeast. With the eastward trend, QPF has decreased
somewhat, especially to the northwest. As a result, snow totals in
the Poconos did not increase, and the Lehigh Valley was also little
changed. However, they did increase a little more noticeably over
southeast PA and north-central NJ. The Winter Storm Warning was
extended a little further southeast in PA, and Winter Weather
Advisories were extended east of the Delaware River in southern New
Jersey, and to Kent County, MD. Considered Warnings for Morris and
Hunterdon NJ as well. Will hold off there for now but monitor trends
for possible upgrade later.
This will be an impactful event. Rain will steadily change to snow
from northwest to southeast from soon after daybreak through early
this afternoon. Snowfall rates around and locally above 1 inch per
hour are likely in the warned area, and could briefly occur in the
Advisory area also. This is supported by NBM and HREF 1 hr snow
probabilities and strong fgen forcing which will be present. As
winds increase (more on this below), blizzard-like conditions will
occur for a time late this morning and early this afternoon over
much of eastern Pennsylvania and northern New Jersey. Even along the
I-95 corridor, this could be a rather impactful event even though
snow totals will not be as high. A couple hours of snowfall rates of
0.5 to 1 inch per hour and gusty winds with blizzard-like conditions
are likely for that corridor, including Philadelphia. Furthermore,
this looks like a classic setup for a flash freeze, with
temperatures plummeting below freezing while precipitation is still
ongoing. Snowfall rates will taper off by mid afternoon, but light
snow will continue and wet surfaces will continue to freeze as
temperatures fall further, with flash freeze impacts extending
potentially all the way to the coast.
In terms of the wind, there may be a couple of main bursts. The
first will be this afternoon and early this evening with the initial
wind shift to northwest, subsequent pressure rises, and changing of
precipitation to snow. This looks like a good bet to bring 40 to 45
mph gusts, locally higher, to much of the region during the
afternoon and early evening. These winds could lead to areas of
blowing snow and contribute to continued reduced visibilities well
into the afternoon even as snowfall rates diminish.
There may be a slight lull in wind around or after sunset, though
breezy conditions will continue. From there, winds aloft increase
once again, to 50-55 kt at 850 mb, as low pressure really bombs out
to our northeast and tightens the pressure gradient. This should
yield a renewed round of advisory level wind gusts in the range of
45 mph, locally higher. Some of the BUFKIT profiles do now show a
little bit of a surface inversion overnight which didn't appear to
be present previously. So there is some potential for winds tonight
to underperform a little, but think the boundary layer will probably
end up quite well mixed given the tight pressure gradient and
turbulent flow aloft. Scattered tree and utility damage is possible
due to the winds.
Low temperatures tonight will be very cold, in the 10s and low 20s.
Did go a little on the warmer side of consensus, consistent with
above expectations of a better mixed boundary layer, and
consequently, a warmer surface temperature. But with the wind, it
will feel downright bitter especially in light of recent milder
weather. Wind chill values in the single digits are expected, with
wind chills falling below 0 in the northwestern zones.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
High pressure builds across the southeast states on Sunday, before
building offshore Sunday night with the Mid Atlantic on the northern
periphery. Sunday will remain a breezy day, although not as windy as
Saturday and Saturday night. Winds will also turn more southwest. It
will remain quite cold in the wake of the departing low, with highs
only in the 30s and colder wind chills. Late in the day into the
early evening Sunday, a weak surface trough is forecast to move
across the area while a short wave/vorticity impulse aloft moves
across the area as well. As an area of moisture moves across the
area, there may be enough lift for some snow showers to affect
portions of northeast Pennsylvania and northern New Jersey during
the afternoon, although the chances are fairly small. The rest of
the overnight is expected to be dry.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
High pressure remains offshore Monday with the Mid Atlantic
region under a steady west to southwest flow. So after a cool
weekend, a return to above normal temperatures is expected.
Monday and Monday night are expected to be dry as there will be
limited moisture available.
On Tuesday, a cold front is forecast to move across the east
coast, although there will be limited moisture and lift
associated with the front and weak short wave/vorticity impulse
aloft. So while there will be a chance of showers during the
day, chances are not extremely high at this time. Temperatures
should be warm enough to keep precipitation all rain.
High pressure briefly builds across the northeast states
Tuesday night into Wednesday, nosing its way into the Mid
Atlantic region. Dry conditions are expected to return for
Tuesday night into most of Wednesday.
A coastal low pressure system is forecast to move northward
along the east coast Wednesday night through Thursday and
Thursday night. Differences remain with the timing and track of
the storm, but the closer to the coast, the more precipitation
will affect areas inland. All precipitation is expected to be
all rain with temperatures being above freezing.
Friday is expected to be dry behind the departing storm system
as weak ridging briefly builds across the area ahead of the next
storm system over next weekend.
&&
.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
.Today... IFR/LIFR has arrived across the terminals. Little
improvement is foreseen as rain and then slows will overspread the
area this morning and continue into the afternoon. South to
southeast winds will switch around to Northwest across the terminals
this morning and strong gusts will then develop. Gusts 30 to 35 kts
expected much of the late morning thru the afternoon. Rains will
change to snow with local SN+ at times. A period of ice pellets is
probable and a tempo group has been included with a best estimate of
timing. A rapid return to MVFR then VFR following the end of the
snow later this afternoon. Probably VFR by sunset at most terminals.
.Tonight... Mostly VFR. Sky cover decreasing most areas. Gusty
W to NW winds 20 to 30 kts continue.
Outlook...
Sunday-Sunday night...Mostly VFR conditions expected, although
ceilings may lower to near MVFR for ABE and RDG. West to
southwest winds 10-15 knots, with gusts 20-25 knots during the
day. Gusts drop off by Sunday evening and winds diminish to 5-10
knots or less overnight. Moderate to high confidence.
Monday-Monday night...Mostly VFR conditions expected, although
ceilings may lower to near MVFR for ABE and RDG. Southwest winds
5- 10 knots, with gusts 15-20 knots during the day. Gusts drop
off by Monday evening and winds diminish to 5-10 knots or less
overnight. Moderate to high confidence.
Tuesday...VFR conditions likely to start the day, before
lowering to MVFR with a chance of showers during the day. West
to southwest winds 5-10 knots, shifting to northwest behind a
cold front. Moderate confidence.
Tuesday night...VFR conditions expected. Winds become light and
variable overnight. High confidence.
Wednesday...VFR conditions expected during the day. Winds shift
to southeast 5-10 knots. Moderate confidence.
&&
.MARINE...
Through about 10AM... Sub-SCA conditions expected. South or
southeast winds 10 to 15 kt. Seas 2 to 4 ft. Rain likely.
Rest of today and tonight... A wind shift to northwest and rapid
increase in wind speeds is expected late this morning or early this
afternoon. Sustained winds of 25 to 35 kt with gusts up to 45 kt are
expected. A Gale Warning remains in effect. A couple of sporadic
storm force gusts are likely, but prevailing conditions should
remain high end gales. Seas building to 6 to 8 ft. Rain through this
afternoon, possibly ending as brief snow this evening. Light
freezing spray possible later tonight with the gusty winds and
plunging temperatures.
Outlook...
Sunday-Sunday night...Winds diminishing below gale levels early
Sunday morning. Small Craft Advisory conditions expected during
the day Sunday into Sunday evening, before lowering overnight.
Monday-Wednesday...Conditions are expected to remain below
advisory levels, although winds will gust around 20 knots at
times through the period and seas remain 3-4 feet through the
period.
Thursday... SCA conditions possible due to building seas associated
with a coastal low to our south.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 7 PM EST this evening for PAZ070-
071-102-104-106.
Wind Advisory from 10 AM this morning to 1 AM EST Sunday for
PAZ054-055-060>062-070-071-101>106.
Winter Storm Warning until 7 PM EST this evening for PAZ054-
055-060>062-101-103-105.
NJ...Winter Weather Advisory until 7 PM EST this evening for
NJZ008>010-012-015.
Wind Advisory from 10 AM this morning to 1 AM EST Sunday for
NJZ001-007>010-012>027.
Winter Storm Warning until 7 PM EST this evening for NJZ001-
007.
Winter Weather Advisory from 10 AM this morning to 7 PM EST
this evening for NJZ016>019.
DE...Winter Weather Advisory until 7 PM EST this evening for DEZ001.
Wind Advisory from 10 AM this morning to 1 AM EST Sunday for
DEZ001>004.
MD...Wind Advisory from 10 AM this morning to 1 AM EST Sunday for
MDZ012-015-019-020.
Winter Weather Advisory from 10 AM this morning to 7 PM EST
this evening for MDZ012.
MARINE...Gale Warning until 10 AM EDT Sunday for ANZ430-431-450>455.
&&
Synopsis...MPS/O'Brien
Near Term...O'Brien
Short Term...Iovino/O'Brien
Long Term...Iovino
Aviation...Iovino/O'Hara
Marine...Iovino/O'Brien