Areal Flood Warning 34, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
704 AM EDT Sun Jul 16 2023

.SYNOPSIS...
A large low pressure system over Canada will send a few waves
of low pressure across our region into early next week. Among
those, a weak cold front is expected to cross our region Sunday
into Sunday evening, with widespread precipitation expected
ahead of the front. Broad, weak high pressure will build in mid
week, before a trough approaches our region at the end of next
week.

&&

.NEAR TERM /THROUGH MONDAY/...
After a brief lull around midnight, in between a seemingly
never- ending stream of shortwaves passing by our region, a more
potent wave is quickly approaching with showers and embedded
thunderstorms with heavy downpours expanding across much of our
region early this morning. This is accompanied by stronger and
larger scale forcing, as well as a slug of deep sub- tropical
moisture. HREF probability- matched mean 6-hour QPF showed many
areas near and west of I-95 seeing 1 to 1.5 inches of rain
through 8 AM, with locally near 3 inches possible where any
storms persist. Areas near and north of I-78 and particularly
I-80 looked to be most at risk, not just due to where the heavy
rain is projected, but because these areas have recently seen
heavy rainfall, with saturated soils making the region primed
for flooding. Sure enough, flooding rains have focused on areas
from the northern Lehigh Valley north and northeastward, but
have lifted out to the northeast, with only some lingering
showers early this morning.

Continuing during the day on Sunday, model guidance suggests the
most persistent thunderstorm activity will shift eastward across
Delaware and New Jersey, with similar HREF PMM amounts as was
mentioned above. That projected shift to the east may be
occurring quicker than earlier expected, so that at least some
portions of our area, especially across eastern PA, may have a
lull for awhile this morning. However additional scattered
showers and thunderstorms will likely develop even back to the
west across eastern PA as a cold front approaches. Those may be
more scattered in nature with perhaps less potential for
training compared to what have been seeing this morning, but
given eastern PA into northwest NJ has been particularly hard
hit the last few days with very saturated soil conditions, it
will not take much more rain to cause flooding issues. We will
continue the Flood Watch everywhere through midnight, and have
now added all of Delaware and eastern MD to the watch, given the
heavy rain already this morning, and hi-res models showing
continued rain focusing on that area. Activity will likely
diminish with the loss of daytime heating and a cold front
pushing through early this evening, with possible just isolated
showers and thunderstorms after 6 PM dissipating completely
after 9 PM or so.

Aside from the flooding threat, isolated severe thunderstorms
will be possible through this afternoon, especially if we see
any partial sunshine and breaks from this mornings more
persistent downpours. CAPE and DCAPE look more minimal compared
to the last couple of days, but there will be enough shear so
that if any storms are able to become more discrete, some
stronger updrafts may develop. The main threat will be locally
gusty winds. However, SPC has a 5% tornado area and a slight
risk near northeast NJ, mainly just out of our area. Thinking
the threat is very low in most of our region with not too much
in the way of low-level veering winds...however, given that we
have already issued a tornado warning for a cell with strong
rotation that tracked across Hunterdon County NJ, we will need
to keep an eye on things. That storm probably took advantage of
an outflow boundary that resulted in very localized higher low-
level shear.

Today will be a very humid, muggy day otherwise, with dewpoints
into the mid-70s, even upper-70s in some spots, along with highs
well into the 80s. Even this morning low temperatures have
struggled to drop below 80 in some spots. Tonight into Monday we
will see a 'break' in the humidity, with dewpoints dropping back
into the 60s, but the increased mixing and still warm airmass
with westerly flow will actually support temperatures rising
into the low 90s Monday afternoon. It will be a dry day with a
fair amount of sunshine. Some areas of fog may develop tonight
though, and that may last into early morning Monday.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
The next in the series of short wave troughs associated with the
larger mid and upper level low over the Hudson Bay region will
approach our region on Tuesday. Consequently, have a significant
chance for showers and storms across the region especially
during the day on Tuesday as mid an upper level forcing may be
coincident with peak day time heating. PWATs will again get
near 2 inches as steady south/southwesterly flow sets up, with
dewpoints expected to get into the 70s yet again.

At the surface, another weak cold front is expected to approach
and cross through the region on Tuesday night. It is uncertain
how much of an impact this will have on the evolution of showers
and storms across the region as it will be getting weaker as it
approaches the region and may not arrive until late Tuesday
night.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Updated the long term portion of the forecast early tonight as
to focus on the storm threat after midnight. The main concern
through this period is the timing of any short wave troughs
associated with the larger Hudson Bay low which could dig south
far enough to bring precipitation chances to our region. At this
point, the favored period is Thursday into Friday. Not only
is guidance continuing to depict a mid level short wave trough,
but a stronger cold front is possible on Friday. Otherwise, a
series of weak high pressures will largely be in place for the
middle part of the week. However, the subsidence associated with
these high pressures likely won't be quite strong enough to
completely suppress diurnal shower activity. Therefore, PoPs
remain in the 20 to 40 percent range for much of the area
throughout the long term.

Temperature wise, We should be near or slightly above normal
through much of the week, but there is increasing confidence
that the cold front depicted on Friday will bring a
significantly cooler air mass than we have seen lately. If this
trend continues, then temperatures slightly below normal are
possible by the end of the week.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Today...Numerous showers and thunderstorms expanding across our
region, with periods of heavy rain and IFR to even briefly LIFR
VSBY possible particularly around the I-95 corridor this
morning. That will tend to shift east across NJ this afternoon,
but scattered thunderstorms will still be possible back to the
west until activity diminishes and shifts offshore this evening.
Ceilings are generally around 010-020, with localized. Some
periods of improvement to VFR will be possible after 15Z or so,
at least outside of shower and thunderstorm activity, but
widespread and sustained improvement to VFR should not be
expected until this evening. Low confidence in the details of
timing thunderstorms and IFR/LIFR conditions.

Tonight...Showers and thunderstorms dissipating or shifting
offshore around 22-02Z, with VFR conditions likely at least
initially. However, areas of fog may develop, especially outside
of the urban corridor, but would not rule out some there as well
particularly toward 12Z. Very light westerly winds. Low
confidence in fog formation.

Monday...VFR. W to SW winds 4 to 8 kt. High confidence.

Outlook...

Tuesday...VFR in the morning, with sub-VFR conditions possible
in the afternoon with showers and thunderstorms developing.
Southerly winds around 10 kt. Moderate confidence.

Wednesday...Mainly VFR. A few evening showers and thunderstorms
possible. Winds 5 to 10 kts. Moderate confidence.

Thursday...Mainly VFR. Restrictions possible with scattered
afternoon and evening showers and thunderstorms. Southwest winds
around 5 to 10 kts. Moderate confidence.

&&

.MARINE...
While winds and waves will remain below Small Craft Advisory
levels through Monday, scattered tstms will have localized
higher seas and winds this morning through the early evening
hours. We have already issued a special marine warning for
Delaware Bay overnight, and more of those may be needed.
Southerly winds may briefly be above 15 kt this morning
particularly north of Barnegat light. Winds will ease and turn
westerly behind a cold front tonight. Seas mostly 3 to 4 ft for
the ocean and around 2 to 3 ft for Delaware Bay.

On Monday, light NW winds early will become S around 10 kt or so
in the afternoon. Seas remaining around 3 to 4 ft.

Outlook...

Tuesday through Thursday...Winds and seas should stay below SCA
criteria.

Rip Currents...

A southerly wind 10 to 15 MPH is anticipated for Sunday with
breaking waves around 2 to 3 feet and a medium period east to
southeast swell. The expected conditions will likely result in a
MODERATE risk of dangerous rip currents along the coasts of
Delaware and New Jersey at that time.

A northwest to west wind 5 to 10 MPH on Monday morning is
forecast to become southerly in the afternoon. Breaking waves
should be 2 to 3 feet with a medium period east to southeast
swell. However, the guidance also indicates the arrival of an
underlying long period swell from the east and southeast which
could enhance the rip current risk. As a result, we will again
carry a MODERATE risk for Monday.

&&

.HYDROLOGY...
A Flood Watch is in effect for all of our PA and NJ counties,
with New Castle County, DE included as well. A widespread 1 to 2
inches of rain is expected for most of the region, with some
locations in northern NJ and eastern PA expected to see 2 to 2.5
inches of rain. Locally higher amounts between 3 to 5 inches
are possible. Taking into account antecedent conditions, it will
not take much for flash flooding to occur, especially in
northern NJ and eastern PA. There remains potential for main-
steam river flooding to occur due to excessive runoff,
particularly later today and tonight. Some rivers, primarily in
northern NJ, are already running high.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch through this evening for PAZ054-055-060>062-070-
     071-101>106.
NJ...Flood Watch through this evening for NJZ001-007>010-012>027.
DE...Flood Watch through this evening for DEZ001.
     Flood Watch until 4 PM EDT this afternoon for DEZ002>004.
MD...Flood Watch until 4 PM EDT this afternoon for MDZ012-015-019-
     020.
MARINE...None.

&&

SYNOPSIS...Johnson
NEAR TERM...Dodd
SHORT TERM...Johnson
LONG TERM...AKL/Johnson
AVIATION...Dodd/Johnson
MARINE...Dodd/Johnson
HYDROLOGY...

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
729 AM EDT Sun Jul 16 2023

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

0600 AM     Flash Flood      4 NNE Belvidere         40.88N 75.05W
07/16/2023                   Warren             NJ   Dept of Highways

            Report of landslide on Route 46, with lanes
            in both directions closed. Time estimated.

&&

Hoeflich

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
736 AM EDT Sun Jul 16 2023

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

0540 AM     Tstm Wnd Dmg     1 WNW Mendham           40.78N 74.62W
07/16/2023                   Morris             NJ   Public

            Report of trees down on Mountainside Road in
            Mendham. Time estimated via radar.

&&

Hoeflich

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
741 AM EDT Sun Jul 16 2023

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

0700 AM     Rain             Wantage Twp             41.24N 74.62W
07/16/2023  M3.65 inch       Sussex             NJ   Trained Spotter

            3.65 inch rain report since midnight.

&&

Hoeflich

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
746 AM EDT Sun Jul 16 2023

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

0700 AM     Flash Flood      2 NW Oxford             40.83N 75.03W
07/16/2023                   Warren             NJ   Public

            Picture of rushing water over the
            roadway-Route 519. Time estimated.

&&

Hoeflich

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
901 AM EDT Sun Jul 16 2023

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

0524 AM     Tstm Wnd Dmg     Long Valley             40.78N 74.77W
07/16/2023                   Morris             NJ   911 Call Center

            Trees down in Long Valley Township, PA. Time
            estimated from radar.

&&

Hoeflich

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
944 AM EDT Sun Jul 16 2023

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

0900 AM     Rain             Forks Twp               40.73N 75.19W
07/16/2023  M4.23 inch       Northampton        PA   Trained Spotter

            Trained Spotter reported 4.23 inches of rain
            in Forks Township, PA.

&&

Hoeflich