Special Weather Statement, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
926 PM EDT Fri Jul 14 2023

.SYNOPSIS...
A deep closed upper low over south-central Canada will slowly
build to the south and east through the weekend before departing
early in the new week. An upper trough will then set up over
the Northeast. Several disturbances will spin off this low and
will pass through the region during this time.

&&

.NEAR TERM /THROUGH SATURDAY/...
Thunderstorms produced localized heavy rainfall and isolated
strong wind gusts from this afternoon into this evening in the
Lehigh Valley, the Poconos and northern New Jersey. The
convection was ongoing around 9:00 PM. However, most of the
showers and thunderstorms are expected to weaken and dissipate
by midnight as conditions become less unstable. The isolated
convection in the lower Susquehanna River Valley and the middle
Chesapeake Bay Region should also weaken not affect our forecast
area.

It should be a relatively quiet overnight period. Some patchy
fog and low stratus should develop after midnight. Dewpoints
will be very close to temperatures at that point, both in the
upper 60s and low to mid 70s. It will feel quite muggy.

For Saturday, it does look pretty quiet for the most part. A
closed upper level low will begin to push southeast through
south central Canada, with a weak shortwave lifting through the
region. Convective initiation will be focused along the sea-
breeze, but any showers/thunderstorms will be on the more
scattered to isolated side. Precipitation chances are relatively
low compared to today and Sunday, around 15-30%. Temperatures
will get into the upper 80s with some spots getting into the low
90s. With dewpoints getting into the low to mid 70s, it will
feel tropical and heat indices will be getting close to triple
digits.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Upper trough with strong shortwave energy digs through the
Great Lakes and Ohio Valley Saturday night. Surface low pressure
develops over the Ohio Valley Saturday night and tracks into
western Pennsylvania and western and central New York during the
day Sunday before departing. Meanwhile, a secondary low looks
to form southwest of the Delmarva Peninsula on Sunday, and that
low tracks to the north and east across New Jersey before
departing Sunday night.

Deep south to southwest flow ahead of this system will usher a
warm and humid airmass into the region. Surface dew points will
rise well into the low to mid 70s across much of the region, and
in the upper 70s in southern Delmarva, Saturday night through
Sunday evening.

Showers will become likely with a chance for thunderstorms
Saturday night as the first low passes north of the area.
Although it will be night, there should be 500 to 1000 J/kg of
surface-based CAPE, but there will also be 35 to 45 kt of 0-6 km
Bulk Shear. A few stronger thunderstorms are possible, but the
main threat will be heavy rain as PWATs will be over 2.25
inches. With winds from 1000 to 500 mb averaging 25 to 30 kt,
storms should be moving fairly quickly, so any flooding should
be localized unless there is training of storms. Areas of fog
will develop as well.

Going into Sunday, as the secondary low passes over the area,
showers and thunderstorms will spread over the area. PWATs will
be in excess of 2.25 inches, and may approach 2.5 inches. Highs
on Sunday will top off in the mid and upper 80s, and this should
yield surface-based CAPE values as high as 1500 to 2000 J/kg
along with 25 to 30 kt of 0-6 km Bulk Shear. Stronger to severe
thunderstorms will be possible with potentially damaging winds,
but once again, the main threat will be heavy rain. Given a
swath of heavy rain Saturday night, any additional heavy
rainfall will result in flooding and flash flooding. The Weather
Prediction Center keeps most of the area in a Marginal Risk for
Excessive Rainfall, but there is a part of far northern New
Jersey that is in a Slight Risk for Excessive Rainfall on
Sunday.

Low pressure departs Sunday night and a cold front passes
through the region late. Showers and thunderstorms will taper
off from west to east. It will take some time for drier air to
filter into the region, and given abundant low level and surface
moisture from the rainfall, patchy fog will develop Sunday
night.

A ridge of weak high pressure noses in from the southwest on
Monday. Conditions should be dry, mostly sunny, and dew points
will be a bit lower, generally in the mid to upper 60s. Highs
will top off in the upper 80s to low 90s. There should even be
some mixing in the afternoon that would lower dew points during
the peak heating of the day and may result in winds gusting 20
to 25 mph.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Closed upper low will be over the southern portion of Hudson
Bay, Canada Monday evening and will lift north into the northern
Province of Quebec. An upper trough will extend down from this
low and will lie over the eastern Great Lakes and Northeast
Tuesday through Wednesday. Zonal flow sets up Thursday before
another mid-level trough approaches on Friday. Although the
weather will still be unsettled, especially on Tuesday,
conditions overall and throughout next week may not be quite as
active as they were this week.

Some weak shortwave energy passes through Monday evening, and
there will be some isolated showers and thunderstorms. Most of
the night should be quiet.

The base of the upper trough passes north of New York state,
and low pressure will develop west of the region and will pass
through the region on Tuesday. Deep south to southwest flow
ahead of this system will usher a hot and humid airmass into the
Northeast and Mid- Atlantic with highs in the upper 80s to low
90s and surface dew points in the upper 60s to low 70s. There is
a good chance for convection on Tuesday, especially in the
northern zones, as low pressure and a cold front work their way
through the region.

Showers and thunderstorms taper off Tuesday night, and then it
will be quiet into Wednesday. Some weak shortwave energy may
touch off isolated afternoon showers and thunderstorms. Cooler
and less humid on Wednesday with highs in the mid and upper 80s
and surface dew points in the low to mid 60s.

As another upper trough digs down into the Great Lakes, more
shortwaves will rotate around the base of the trough and will
pass through the region for the end of the week. These will once
again bring chances for showers and thunderstorms Thursday and
Friday. Highs will generally be in the upper 80s with dew points
in the upper 60s.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 04Z...Mainly VFR. Scattered showers and thunderstorms
in the KABE vicinity will continue to move away to the
northeast. Wind favoring the south at less than 10 knots.
Medium to high confidence.

Overnight (04Z to 10Z)...Initially VFR, with areas of MVFR/IFR
ceiling and visibility restrictions developing after 06Z.
Variable wind 5 knots or less. Medium confidence.

Saturday...Some lingering MVFR/IFR ceiling and visibility
restrictions through about 14Z, then mainly VFR. A slight chance
of showers and thunderstorms in the afternoon. Variable wind 5
knots or less, becoming southerly near 10 knots. Medium
confidence.

Outlook...

Saturday night...Sub-VFR conditions in SHRA/TSRA and fog. S
winds 5 to 10 kt. Moderate confidence.

Sunday through Sunday night...Sub-VFR conditions in
SHRA/TSRA/fog. Rain may be heavy at times. SHRA/TSRA taper off
Sunday night, but restrictions may continue in fog. S winds 10
to 15 kt with gusts up to 20 kt, becoming LGT/VRB at night.
Moderate confidence.

Monday through Monday night...VFR. Isolated SHRA/TSRA possible
at night. W winds 5 to 10 kt, becoming S at night. Moderate
confidence.

Tuesday through Tuesday night...Primarily VFR. Afternoon SHRA
and TSRA will result in sub-VFR conditions and gusty winds.
Conditions improve Tuesday night. SW winds 10 to 15 kt with
gusts up to 20 kt, becoming W to NW 5 to 10 kt at night.
Moderate confidence.

Wednesday...VFR. W winds 5 to 10 kt. Moderate confidence.

&&

.MARINE...
No marine headlines anticipated through Saturday. Southerly
winds around 10-15 kt with gusts up to 20 kt. Seas 3 to 4 feet.

Outlook...

Saturday night...Sub-SCA conditions. S winds 10 to 15 kt with
gusts up to 20 kt. Seas 2 to 4 ft. VSBY restrictions in showers
and thunderstorms with heavy rain.

Sunday through Sunday night...Marginal SCA conditions. S winds
15 to 20 kt with occasional gusts to 25 kt, becoming W to NW 5
to 10 kt Sunday night. Seas 3 to 4 ft. Showers and thunderstorms
with heavy rain and gusty winds. Showers and thunderstorms
taper off Sunday night, then VSBY restrictions in fog Sunday
night.

Monday through Monday night...Sub-SCA conditions. S winds 10 to
15 kt. Seas 2 to 4 ft.

Tuesday through Tuesday night...Sub-SCA conditions. S winds 10
to 15 kt with gusts up to 20 kt, becoming W 10 to 15 kt at
night. Seas 2 to 4 ft.

Wednesday...Sub-SCA conditions. S winds 10 to 15 kt. Seas 2 to
4 ft.

Rip Currents...

A southerly wind increasing to around 10 MPH is expected for
Saturday. Breaking waves should be 1 to 2 feet with a medium
period southeasterly swell. We will carry a MODERATE risk for
the development of dangerous rip currents for the southeast
facing shoreline of Ocean, Atlantic and Cape May Counties. Both
Monmouth County in New Jersey and Sussex County in Delaware are
forecast to be LOW risk with the southerly wind being parallel
to their coastlines.

A southerly wind around 15 MPH is anticipated for Sunday with
breaking waves around 2 to 3 feet and a medium period easterly
swell. The increasing wind speeds and waves heights will likely
result in a MODERATE risk of rip currents for the entire
coastline of Delaware and New Jersey at that time.

&&

.TIDES/COASTAL FLOODING...
Will continue to keep an eye on the potential for some
localized coastal flooding overnight along Barnegat Bay once
again. That area saw some minor flooding in spots on Thursday
night, so with little change in conditions, the possibility
remains. Although, with astronomical tides lowering slightly,
the risk of flooding should also decrease a bit.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

SYNOPSIS...MPS
NEAR TERM...Hoeflich/Iovino
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...Iovino/MPS
MARINE...Hoeflich/MPS
TIDES/COASTAL FLOODING...Staff

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Special Weather Statement
National Weather Service Mount Holly NJ
951 PM EDT Fri Jul 14 2023

NJZ008>010-150215-
Hunterdon NJ-Morris NJ-Somerset NJ-
951 PM EDT Fri Jul 14 2023

...Strong thunderstorms will impact portions of east central
Hunterdon, southeastern Morris and northern Somerset Counties through
1015 PM EDT...

At 951 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Mendham to near Peapack And Gladstone.
Movement was east at 10 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Morristown, Somerville, Bridgewater, Madison, Florham Park, East
Hanover, Bound Brook, Manville, Chatham, Morris Plains, Mendham,
Peapack And Gladstone, Lebanon, Far Hills, Parsippany, Martinsville,
Millington, White House Station, Basking Ridge and Bernardsville.

This includes the following highways...
 Interstate 78 in New Jersey between mile markers 22 and 41.
 Interstate 80 in New Jersey near mile marker 46.
 Interstate 287 in New Jersey between mile markers 13 and 41.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4082 7434 4079 7437 4076 7438 4075 7436
      4074 7437 4068 7445 4067 7446 4065 7444
      4052 7458 4063 7484 4086 7459 4086 7432
TIME...MOT...LOC 0151Z 275DEG 7KT 4080 7456 4067 7471

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

Staarmann