Flood in New Jersey, November 26 to 27, 2023

Area Forecast Discussion
National Weather Service Mount Holly NJ
1150 PM EST Sun Nov 26 2023

.SYNOPSIS...
Low pressure will pass by New Jersey tonight, then move into
New England early Monday morning. A dry but strong cold front
will sweep across the region late Monday, then high pressure
builds to our south for the middle of the week. A cold front
moves through late Friday, then low pressure may then arrive
next weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
Overall the forecast remains on track, with just some
adjustments mainly in timing details tonight. Coastal low
pressure tracking across New Jersey tonight will head to
interior southern New England by the predawn hours on Monday.
The rain has been as advertised for the most part, though the
progression of the system has been perhaps as much as a couple
hours ahead of schedule. The back edge of the steadier rain
passing by Delaware Bay will reach Philly by 11 PM or certainly
midnight, passing quickly northeastward out of the rest of our
area around 1 to 2 AM or so. As a rather potent, negatively-
tilting upper- trough approaches and our surface low intensifies
while tracking over NJ, deeper and more dynamic forcing has
resulted in heavier rain rates, particularly from near I-95
northwestward, with even a few rumbles of thunder in spots.
Rainfall rates locally near 1/2" per hour resulted in ponding
and some tough travel Sunday evening, but only brief minor
nuisance flooding in spots of particularly poor drainage, mainly
in urban areas.

Temps are running milder from the urban corridor southeastward,
with mid-40s to even mid-50s near the coast, while a raw, cold
rain with mid to upper 30s is found near and north of the Lehigh
Valley. By morning expect upper 30s to low 40s to filter in on
light westerly winds in the wake of the passing area of low
pressure, along with breaking and scattering cloud cover in many
areas by daybreak.

Stronger cold-air advection will commence in on Monday with the
passage of the mid and upper-level trough axis. Winds will
become gusty especially in the afternoon on Monday with gusts up
to 25-30 mph as the pressure gradient tightens as low occludes
over Ontario. Highs will struggle to get out of the 40s in most
of our area, away from the coast, with upper 30s in the Poconos.
Otherwise expect a dry day with clearing skies and quite a bit
of sunshine.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
An arctic air mass overspreads the region resulting in temperatures
well below average. A gusty wind will also add to the chill.

The arrival of a strong upper-level trough will usher in an arctic
air mass across our region. The trough axis is forecast to cross our
area during Tuesday, resulting in the core of the cold air mass to
move across the area. Following the passage of a dry but strong cold
front Monday evening, the 850 mb temperatures are forecast to tumble
to around -13C through Tuesday. This will result in surface air
temperatures falling into the 20s Monday night and with a breeze it
will feel even colder.

As mentioned above, the upper-level trough axis crosses our area
during the day Tuesday. The air mass forecast to be in place is very
cold and rather dry, with dew points dropping through the teens.
There should be some stratocumulus development though given the
extent of the cold air aloft. In addition, west to northwest flow
may pull some lake effect snow showers/streamers into parts of our
area. The main area of focus looks to be the Poconos toward
northwestern New Jersey. We therefore included slight chance to low
chance PoPs (20-30 percent) for snow showers there. It is possible a
few snow showers or flurries get at least a little farther south and
east Tuesday afternoon. The main theme will be the coldest air of
the season so far, and there will be an added wind chill as well. A
tight pressure gradient will be in place and that will drive a gusty
wind. The model forecast soundings show deep mixing occurring during
the day Tuesday as the low-level lapse rates steepen quite a bit.
Given the profiles the surface wind gusts look to peak at around 35
mph during the daytime hours, then the winds diminish during Tuesday
night as the mixing wanes and the air mass starts to moderate aloft.
The combination of temperatures struggling to climb out of the 30s
during the day Tuesday along with strong winds will drive wind chill
values down into the teens and 20s (even single digits at times in
the Poconos). Very cold Tuesday night with temperatures dropping
into the low to mid 20s (some upper teens in the Poconos).

The overall flow aloft becomes much more zonal Wednesday in the wake
of the aformentioned upper-level trough. As this occurs, surface
high pressure builds to our south with the low-level flow turning
more from the southwest. This will result in an increasing warm air
advection regime, however the lower level air mass will still be on
the cold to chilly side. Daytime temperatures should warm a bit more
compared to Tuesday and the wind will not be as strong, but still a
cold day. A passing shortwave to the north by later in the day may
result in some increase in clouds especially across the northern
areas. Low temperatures Wednesday night are forecast to be in the
mid/upper 20s to low 30s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Summary...Temperatures moderate into the weekend. Potentially
unsettled over the weekend.

Synoptic Overview...An expansive upper-level trough, centered near
Hudson Bay Canada, is forecast to remain in place through late in
the week before shifting eastward. This places our region within
mainly zonal flow aloft, although an amplifying upper-level trough
from the Plains and Midwest shifts eastward over the weekend. It is
this system that should support surface low pressure into the Great
Lakes, however secondary surface low development may take place in
the vicinity of the Mid-Atlantic region during the weekend.

For Thursday and Friday...The center of an upper-level trough or
closed low is forecast to be near Hudson Bay Canada before it then
gradually shifts eastward. This places our area in a more zonal flow
aloft regime with surface high pressure centered to our south. The
surface high then shifts more into the western Atlantic into Friday.
This flow regime favors disturbances tracking to our west and north,
and currently low pressure tied to the closed low has a warm front
to our north Thursday as a cold front is draped back into the
Midwest. Some southern stream energy may result in low pressure
across the central Plains. An initial cold front should settle
across our area sometime on Friday. The chances for precipitation
with the passage of this front will generally depend on the timing
of an impulse tracking northeastward along the front. Although there
is some uncertainty with this, there is enough of a model consensus
to carry chance PoPs (30-50 percent) for now. After a chilly start
Thursday, temperatures will be moderating thanks to a more west to
southwest flow ahead of the aforementioned cold front and low-level
warm air advection.

For Saturday and Sunday...Our sensible weather during the weekend
will depend on the timing and track of a possible low pressure
system. This will be tied to an upper-level trough moving across the
Plains and Midwest Saturday which then shifts eastward. A cold front
should be offshore Saturday, however it extends back into the
Tennessee Valley where low pressure should organize associated with
the aforementioned trough shifting eastward. The timing and
amplitude of this trough varies at least some among the guidance,
thus PoPs were kept at chance or less. Some guidance does show
strong Canadian high pressure building to our north and potentially
setting up some cold air damming (also drier low-level air settling
southward) ahead of the surface low. The associated air mass does
not look all that cold at this point, but something to watch
regarding precipitation types for parts of the area within a
potentially strengthening overrunning setup.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...Rain with VSBY 1 to 3 SM and CIGs mainly LIFR, but
tending MVFR near the NJ shore this evening. From 04-07Z, expect
quickly improving conditions from southwest to northeast as the
rain lifts out and low ceilings lift and scatter. Winds shifting
to SW-W around 5-10 kt through 02-05Z as low pressure passes
by. There may be a period where winds are quite variable as the
low passes. Some 025-050 CIGs may linger after the rain ends
after 06Z. Moderate confidence in general progression, but
precise timing of details will be tough to capture in TAFs.

Monday...VFR with scattered clouds. W-NW winds around 10-15 kt with
gusts up to 20-25 kt possible in the afternoon. High confidence.

Outlook...

Monday night and Tuesday...VFR. West-northwest winds around 10 knots
increasing to 15-20 knots Tuesday with gusts up to 30 knots. The
winds then diminish some Tuesday night. Moderate confidence.

Wednesday and Thursday...VFR. West to southwest winds around 10
knots. Moderate confidence.

Friday...MVFR ceilings may develop along with a chance of showers.
Southerly winds 5-10 knots. Low confidence.

&&

.MARINE...
A Small Craft Advisory is in effect through Monday for all ocean
zones, and that expands to Delaware Bay after midnight.

East-southeasterly winds 15-25 kt with gusts up to 30 kt
expected as a low tracks along the Delaware and New Jersey
coasts this evening. After midnight as the low lifts north of
NJ, winds will quickly become SW-W around 20-25 kt with gusts
up to 30 kt as well. For Monday, winds will ease up a bit in the
morning with gusts 20 kt or less most places near shore and over
the Bay, but W-NW increase through the afternoon with gusts up
to 30 kt. Seas of 4-6 feet expected tonight and Monday.

Outlook...

Monday night...Small Craft Advisory in effect.

Tuesday...Gale Watch issued for all zones as wind gusts of 35-40
knots are probable, especially in the afternoon and evening.

Wednesday...Small Craft Advisory conditions possible, mainly due
to wind gusts to 25 knots.

Thursday and Friday...Wind gusts to near 25 knots possible to start
Thursday, otherwise the conditions should be below Small Craft
Advisory criteria.

&&

.TIDES/COASTAL FLOODING...
Higher astronomical tides are expected for Monday morning's high
tide with the November 27th Full Moon. A Coastal Flood Advisory
has been issued for Monmouth and Ocean County where widespread
minor tidal flooding is expected. Elsewhere, a west wind
direction has been prevailing for a longer period of time,
allowing water to drain more efficiently compared to the
northern NJ coast. Spotty minor tidal flooding is anticipated
for the rest of the Atlantic coast and parts of the lower
Delaware Bay. Tidal flooding is not expected within the upper
Delaware Bay, tidal Delaware River, or within the Chesapeake
Basin.

Following the morning high tide on Monday, coastal flooding is
not expected with the waning moon phase and strong
west/northwest wind direction, which allows water to drain from
the back bays and tributaries.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory from 6 AM to noon EST Monday for NJZ013-
     014-020-026.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 AM EST Tuesday for ANZ430-431.
     Gale Watch from Tuesday morning through Tuesday evening for
     ANZ430-431-450>455.
     Small Craft Advisory until 6 AM EST Tuesday for ANZ450>455.

&&

SYNOPSIS...Gorse
NEAR TERM...Dodd/DeSilva
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Dodd/DeSilva/Gorse
MARINE...Dodd/DeSilva/Gorse
TIDES/COASTAL FLOODING...Hoeflich

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Preliminary Local Storm Report
National Weather Service Mount Holly NJ
1131 PM EST Sun Nov 26 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1025 PM     Rain             Germansville            40.70N 75.71W
11/26/2023  M1.06 inch       Lehigh             PA   Trained Spotter

            Trained spotter reported 1.06 inches of
            rain. Time given in report.

&&

Hoeflich