NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Feb 13, 5:35 AM EST, 25 minutes earlier.
Area forecast discussion, Feb 13, 5:35 AM EST, 25 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
535 AM EST Tue Feb 13 2024
.SYNOPSIS...
Low pressure will intensify as it moves into the Atlantic today,
providing plenty of wintry precipitation to the region this
morning. High pressure returns for Wednesday and Thursday before
an Alberta Clipper crosses the region Thursday night. Another
weak system will cross the region Friday night into Saturday.
High pressure gradually returns late in the weekend into early
next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
530 AM update... spotter reports that guidance has overestimated
the dry air on the northern extent and accumulations are
exceeding earlier expectations across our northern zones. Thus
have re-upped accumulations back into the 8-12 range. No other
adjustments at this time.
After extensive revisions to the forecast last evening,
guidance has finally come to a relative concensus regarding the
low pressure crossing the region this morning. As of 4 AM, the
rain-line is a bit south of the I-78 corridor, with snow as far
south as Reading, Perkasie and Somerville, but sleet just south
of there and rain still falling across Philly metro. Expect the
line to continue working southward over the next several hours
with snow falling across the I-95 corridor by the middle of rush
hour. This will unfortunately coincide with the arrival of the
heaviest precipitation associated with the comma-head of the low
pressure passing to our south. Thus, we could see rapid
deterioration of conditions on the Philly metro roadways just as
they are filling with traffic, a potentially very bad
combination. We urge anyone with travel plans this morning to
delay until afternoon if possible, when conditions will improve
markedly as the storm moves out.
It appears now that the rain-line will eventually sweep
southeastward all the way to Cape May County and central
Delaware before precip tapers off near or just after noon, but
significant accumulations will remain confined to areas north.
Inherited a fairly wide coverage of winter storm warnings just
north of the metro and a tier of winter weather advisories
further south across the metro itself. Think these still look
reasonable, though uncertainty remains about just how effective
snow accumulations will be this morning in areas where it is
currently still rain. Would not be shocked if parts of the
advisory area hit warning criteria while others fail to reach
advisory, but that's a tough nut to crack right now and have no
confidence in further changes at this time. Further north, the
extreme northern areas might see precip taper off a little
earlier, so we might struggle to reach warning levels in the far
northern Poconos and NW NJ. Overall, nudged totals back slightly
across the warning areas to a general 4-8 given a relatively
rapid departure of the system near midday and the heaviest
precip likely staying a bit further south.
Aside from the snow, winds will be gusty right along the
immediate coast. Not quite confident we'll see widespread 40 kt
gusts but spotty remains possible so have left wind advisory as
inherited. Looks like strongest winds are this morning. Further
inland, while winds will be less, the combination of heavy wet
snows and gusty winds may result in downed trees, so we'll need
to watch out for that as well this morning. Rainfall totals
where it is mainly rain remain in the 1-1.5 inch range, but
given its mostly in the sandy coastal plain, we continue to not
have significant flood concerns.
By mid-afternoon the storm will be long gone as it quickly hauls
east off the coast, with skies breaking for some sun and temps
likely rebounding back towards 40, so expect some decent melting
this afternoon. However, as temps will fall back below freezing
tonight, re-freeze will be a concern overnight tonight for
anything not treated. Otherwise, just a brisk and chilly night
on tap with temps not far from normal for this time of year,
mostly in the 20s. There could be a few flurries in the Poconos,
but dry otherwise.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
For Wednesday, a tight pressure gradient remains across the
area as high pressure builds to our west. This will keep gusty
winds across the area through the daytime Wednesday. But as we
go into Wednesday night, the pressure gradient begins to lessen
as the high pressure builds a little closer to the Mid Atlantic
region, although it will fully build to our south overnight.
Otherwise, skies should be mostly clear Wednesday/Wednesday
night as subsidence builds into the region with the high
pressure. Temperatures are forecast to rise into the mid-upper
30s for most locations Wednesday afternoon before falling into
the upper teens to low 20s Wednesday night.
On Thursday, the high pressure system to our south builds
offshore, before a clipper-like low pressure system moves out of
the Great Lakes region and moves to our north. This will pull a
cold front across the Mid Atlantic region Thursday evening.
This will bring a chance of precipitation to the area, and
depending on temperatures and location, there will be a chance
of rain or snow for many areas. This system will be fairly quick
moving and will exit the region by daybreak Friday. High
temperatures Thursday will mainly be in the low-mid 40s with
lows Thursday night in the upper 20s/low 30s.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
Another brief quiet period can be expected during the day
Friday as high pressure briefly builds to our south, before
another clipper- like low pressure system possibly impacts the
area Friday night into Saturday. This system will bring a quick
shot of colder air to the area as temperatures fall below
freezing Friday night then only recover into the upper 30s to
low 40s daytime Saturday. Rain and snow both appear to be
possible with this system as a result but at this time the
highest chance for meaningful accumulation appears to be limited
to higher elevation locations.
Another low looks to pass to the north of the region later
Sunday into Sunday night but with high pressure building into
the region from the southwest, the low currently looks to be
held at bay keeping the start of the new week dry. The drier
weather looks to continue into Monday as the high becomes
centered over our region. A slight warming trend is expected
with temperatures returning to near- normal Sunday night into
Monday with lows in the mid-upper 20s and highs in the mid-upper
40s.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY and surrounding areas...
Today...IFR to LIFR perhaps VLIFR with rain changing to snow
from northwest to southeast, eventually reaching all the way to
KACY. Vsby may fall down to 1/4 mile in the heaviest bursts of
snow this morning with cigs below 500 feet. Conditions
dramatically improve midday with VFR by mid-late afternoon.
Winds NE becoming NW with gusts up around 30 kts, possibly 40
kts at KACY. High confidence overall, but low confidence on
exact timing.
Tonight...VFR. Winds NW around 10 kts. High confidence.
Outlook...
Wednesday...VFR conditions expected. Northwest winds 10-15
knots, with gusts 20-30 knots. Winds decrease to 5-10 knots
overnight. High confidence.
Thursday...VFR conditions early, possibly lowering to sub-VFR
conditions later in the day as rain and snow move into the area.
Winds around 5-10 knots, initially west-southwesterly then
gradually become southerly. Moderate confidence.
Thursday night...Sub-VFR conditions possible early, improving
overnight. South-southwesterly winds 10-15 knots early, shifting
to west then northwest overnight with gusts 20-30 knots
possible. Moderate confidence.
Friday...VFR conditions. Northwest winds 15-20 knots with gusts
20- 30 knots. Moderate confidence.
Friday night...Sub-VFR conditions possible with chance (20-30%)
for rain/snow. Southwesterly winds 10-15 knots. Moderate
confidence.
Saturday...Improving back to VFR conditions. Winds becoming
northwesterly 10-15 knots with gusts 20-30 knots.
&&
.MARINE...
Low pressure pushing east into the ocean and strengthening will
bring gales to all coastal waters today. Strongest winds look to
be this morning into midday. Winds diminish to SCA levels
tonight. Seas 5-8 ft today diminishing a bit tonight.
Outlook...
Wednesday...Small Craft Advisory conditions expected through
the period, before diminishing later Wednesday night. Winds may
gust near Gale force on Wednesday.
Thursday...Conditions begin below advisory levels early on
Thursday, before increasing to advisory level winds later on
Thursday.
Thursday night-Friday...At least Small Craft Advisory level
conditions, with the potential for Gale force winds.
Friday night-Saturday...Small Craft Advisory level conditions
continue across the area.
&&
.TIDES/COASTAL FLOODING...
Minor to moderate coastal flooding is forecast to occur with
the high tides tonight along Atlantic coastal New Jersey and
Delaware, Delaware Bay, and the tidal Delaware River. The
astronomical tides are lessening with time as we get farther
away from the New Moon, which occurred on Friday.
A strong coastal system pushing offshore early Tuesday is
forecast to result in increasing surge values upwards of 2-3
feet above the astronomical tides, which will result in
widespread and impactful coastal flooding issues with the high
tides today. The peak of the surge appears to coincide with the
high tide along much of the Atlantic coast of New Jersey and
Delaware this morning. This is forecast to result in moderate
coastal flooding impacts for much of Atlantic coastal New Jersey
and Delaware. A Coastal Flood Warning was issued for the
daytime high tide today for all of the Atlantic Coast of New
Jersey as well as for Sussex County, Delaware.
Elsewhere along the Delaware Bay and the tidal Delaware River,
widespread minor flooding is currently forecast to occur with
each high tide cycle through tonight/early Wednesday morning.
The greatest impacts and inundation will occur with the daytime
high tide today as the aforementioned strong coastal system
moves offshore. A Coastal Flood Advisory was issued for these
areas through tonight/early Wednesday morning as a result.
Additionally, the widespread rainfall of near 1" will lead to
increased fresh water runoff today. This may lead to elevated
water levels, especially along tidal tributaries of the tidal
Delaware River. Thus, there is a possibility of localized
moderate coastal flooding impacts in some areas along the tidal
Delaware River with the afternoon high tide today as well.
For sake of simplicity, the Coastal Flood Warnings and
Advisories were issued with a longer than usual duration to
cover all of the impacted high tides through tonight. The
greatest impacts will be experienced with the daytime high tide
today as the coastal system moves offshore.
No coastal flooding is currently forecast for our eastern shore
of Maryland portions of the northern Chesapeake Bay through
Wednesday.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 3 PM EST this afternoon for
PAZ070-071.
Winter Storm Warning until 3 PM EST this afternoon for PAZ054-
055-060>062-101>106.
Coastal Flood Advisory until 10 AM EST Wednesday for PAZ070-
071-106.
NJ...Coastal Flood Advisory until 4 PM EST this afternoon for
NJZ016.
Winter Weather Advisory until 3 PM EST this afternoon for
NJZ014-016>020.
Coastal Flood Advisory until 3 AM EST Wednesday for NJZ021.
Coastal Flood Warning until 3 AM EST Wednesday for NJZ012>014-
020-022>027.
Wind Advisory until 5 PM EST this afternoon for NJZ014-024>026.
Winter Storm Warning until 3 PM EST this afternoon for NJZ001-
007>010-012-013-015.
Coastal Flood Advisory until 10 AM EST Wednesday for
NJZ017>019.
DE...Coastal Flood Advisory until 4 PM EST this afternoon for
DEZ001.
Winter Weather Advisory until 3 PM EST this afternoon for
DEZ001.
Coastal Flood Advisory until 3 AM EST Wednesday for DEZ002.
Coastal Flood Warning until 3 AM EST Wednesday for DEZ003-004.
Wind Advisory until 5 PM EST this afternoon for DEZ004.
MD...None.
MARINE...Gale Warning until 6 PM EST this evening for ANZ430-431-
450>455.
&&
SYNOPSIS...RCM
NEAR TERM...RCM
SHORT TERM...AKL/Robertson
LONG TERM...AKL/Robertson
AVIATION...AKL/RCM
MARINE...AKL/RCM
TIDES/COASTAL FLOODING...