Decision Support Page for New Castle County

Forecast Discussion

149
FXUS61 KPHI 191106
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
706 AM EDT Tue May 19 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...
1. Hot and more humid conditions continue, with record setting
early season heat probable, through Wednesday.

2. A cold front will bring some showers and thunderstorms to
the region Wednesday through Thursday, then much cooler
temperatures by the end of this week.

&&

.DISCUSSION...
KEY MESSAGE 1...Hot and more humid conditions continue, with
record setting early season heat probable, through Wednesday.

A strong upper-level ridge centered off the Southeast U.S. coast
will remain in place through late this evening before it starts
to flatten on its northwest side during Wednesday. This along
with surface high pressure anchored in the western Atlantic will
drive a south to southwest flow of early season (anomalous)
heat across our area into Wednesday.

Temperatures are forecast to peak into the 90s for many areas again
today and Wednesday, except cooler along the coasts and the
higher terrain. While the surface dew points will likely mix out
some during peak heating due to the drier ground and boundary
layer (low evapotranspiration), this stretch of early season
heat, with record breaking high temperatures probable, will have
potentially greater impacts. The Heat Advisory remains in place
across much of the region, including most of the area where the
heat index criteria starts at 100F (the urban I-95 corridor
criteria starts at 96F through June). While it will probably
fall a little short for some areas, the potential greater
impacts (lack of acclimation) is driving our decision. Where the
wind turns more from the south and especially southeast will
result in quite a bit of cooling due to the chilly ocean and
therefore did not include the immediate coastal zones in the
Heat Advisory. Peak heat indices will be 95 to nearing 100
degrees, with the core of the heat shifting a bit more south and
east during Wednesday as a strong cold front starts to arrive.
Based on this, portions of the Heat Advisory for areas farther
north and west of I-95 only goes through Tuesday. High
temperatures on Wednesday will depend on how quickly cloud cover
arrives along with showers and some thunderstorms. Either way,
we will have a high launching pad for temperatures to start
Wednesday and it will still be rather hot.

Temperatures at night will be quite warm by mid May standards. Lows
will only be in the mid 60s to low 70s, which will challenge daily
warmest low temperature records for May 19th.

Today will largely be dry as well thanks to the strong ridging
overhead. However, a stray shower or storm cannot be completely
ruled out this afternoon and evening with the amount of heat and
instability in the low-levels. The most likely location for any
storms would be north of I-78 where terrain would aid in
forcing for any convection. Shear will be relatively low though
(only around 25-30 kts) so little organization is expected with
anything that does form.

KEY MESSAGE 2...A cold front will bring some showers and
thunderstorms to the region Wednesday through Thursday, then
much cooler temperatures by the end of this week.

As mentioned above, a cold front will approach the area Wednesday
and bring an end to the stretch of above normal temperatures by
Thursday. Showers and thunderstorms will accompany this front
as it passes through the region. Recent guidance trends continue
to show the front moving through during the second half of Wednesday
into Wednesday night. Given this timing, there is the threat for
strong to severe thunderstorms. There remains uncertainty in the
more specific details and some timing variations remain. Regarding
the threat for strong to severe thunderstorms, the cold front will
be moving into an air mass that will feature plenty of instability.
The better shear and forcing look to be to our north, but bulk shear
values will be supportive of some storm organization along with some
supportive lapse rates. All of this said, the potential is there
for isolated strong to severe thunderstorms with the SPC
maintaining a Marginal Risk in Wednesday`s severe weather
outlook. The primary concerns with any strong to severe
thunderstorm would be damaging wind gusts and large hail.
General rainfall accumulation from this frontal passage looks
around 0.25" or less. However, given this convection and PWAT
values reaching to 1.5-2.0", localized higher amounts are
certainly possible with any heavier pockets of rain.

As the front sinks south into Thursday morning, it then looks
to linger near or just south of the area through the remainder
of the day Thursday. This will lead to the potential for more
rain showers, particularly for our southeastern zones. An
unsettled pattern looks to continue to take shape for Friday and
into the weekend.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Mainly VFR. Southwesterly winds 5-8 knots increasing to
10-15 knots, with some afternoon gusts up to 20 knots. Can`t
rule out a stray shower/storm, most likely at KABE, but overall
chances are low (15% or less). Moderate confidence.

Tonight...VFR. Southwest winds 5-10 knots, becoming locally
light and variable. High confidence.

Outlook...

Wednesday through Thursday...Sub-VFR with rain showers and
thunderstorms Wednesday afternoon and evening. Rain showers may
continue into Thursday.

Friday through Saturday...Sub-VFR with rain showers moving
through.

&&

.MARINE...
Small Craft Advisory continues for the New Jersey Atlantic coastal
waters this afternoon and evening. Though southerly flow will
be increasing, a hot air mass will be moving over the chilly
water and the vertical mixing will be reduced. However, given
the strength of the flow, there should be a period of wind
gusts to around 25 knots and seas building to about 5 feet. It
looks to be more marginal for the Delaware Atlantic coastal
waters and therefore held off on issuing an advisory. For
Delaware Bay, the conditions should continue to remain below
Small Craft Advisory criteria through tonight.

Outlook...

Wednesday...Small Craft Advisory conditions possible. Seas
lessen by Wednesday morning but elevated winds out of the
southwest remain through the day Wednesday with gusts near 20-25
kt. Rain showers move in Wednesday afternoon into Wednesday
night. There is also the potential for isolated thunderstorms
Wednesday afternoon into early Wednesday night.

Thursday...Conditions expected to be below Small Craft Advisory
criteria but showers may linger.

Friday through Saturday...Small Craft Advisory conditions
expected as seas reach 4-6 feet. There is the chance for some
rain showers.

Rip Currents...

On Tuesday, south to southwest winds will increase to 15 to 20
mph with gusts up to 30 mph. There will be a southeast swell
with a period around 8 seconds. As a result there is a MODERATE
risk for the development of dangerous and life threatening rip
currents for the Jersey Shore and for Delaware Beaches.
Depending on the exact direction of the winds, there is the
potential for a HIGH risk for rip currents at the Jersey Shore.

On Wednesday, south to southwest winds will be a bit lighter,
and winds look to be more parallel to the shores. There will be
a southeast swell with a period around 6 seconds. As a result,
there is a MODERATE risk for the development of dangerous and
lift threatening rip currents for the Jersey Shore and a LOW
risk for Delaware Beaches.

Will continue to note that while surface temperatures inland
will be in the mid to upper 90s Tuesday and in the low to mid
90s on Wednesday, temperatures along the coasts will mainly be
in the 70s to near 80 due to ocean temperatures in the 50s.
These cold water temperatures can quickly cause hypothermia and
physical incapacitation to anyone suddenly immersed in the
water.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.CLIMATE...
Near record breaking temperatures are forecast from through
Wednesday. High temperatures Tuesday and low temperatures
Wednesday morning could challenge monthly all time records for
May. Below is a summary of the records broken on Monday, May
18th:

Record High Temperatures broken on May 18
Site Record/Year
Georgetown (GED) 91/1974 (new record 96)
Mount Pocono (MPO) 87/1962 (new record 88)
Philadelphia (PHL) 94/1962 (new record 96)
Reading (RDG) 96/1962 (tied record 96)

Record Warmest Low Temperature broken on May 18
Site Record/Year
Mount Pocono (MPO) 61/2017 (new record 63)

Records for our climate sites are listed below:

Monthly Record High Temperatures for May

Site Record/Date
Allentown (ABE) 97/May 19, 1962
AC Airport (ACY) 99/May 29, 1969
AC Marina (55N) 95/May 31, 1895 & May 23, 1925
Georgetown (GED) 98/May 28, 1991
Mount Pocono (MPO) 94/May 22, 1911
Philadelphia (PHL) 97/May 30 & 31, 1991
Reading (RDG) 97/May 20, 1996
Trenton (TTN) 99/May 23, 1911 & May 31, 1986
Wilmington (ILG) 98/May 10, 1895 & May 30, 1895

Monthly Record Warmest Low Temperatures for May

Site Record/Date
Allentown (ABE) 71/May 31, 1975, May 28 & 31, 1991
AC Airport (ACY) 73/May 24, 2004 & May 19, 2017
AC Marina (55N) 73/May 30 & 31, 1987, & May 31, 1991
Georgetown (GED) 74/May 23, 1953 & May 20, 2019
Mount Pocono (MPO) 68/May 21, 1996
Philadelphia (PHL) 78/May 31, 1895
Reading (RDG) 72/May 28 & 31, 1939, & May 31, 1991
Trenton (TTN) 75/May 31, 1895
Wilmington (ILG) 75/May 30, 1895

Record High Temperatures
May 19
Site Record/Year
Allentown (ABE) 97/1962
AC Airport (ACY) 96/1962
AC Marina (55N) 92/1998
Georgetown (GED) 96/1962
Mount Pocono (MPO) 89/1962
Philadelphia (PHL) 96/1962
Reading (RDG) 96/1962
Trenton (TTN) 96/1962
Wilmington (ILG) 95/1962

Record Warmest Low Temperatures
May 19
Site Record/Year
Allentown (ABE) 65/2017
AC Airport (ACY) 73/2017
AC Marina (55N) 68/1998
Georgetown (GED) 73/2017
Mount Pocono (MPO) 60/1943
Philadelphia (PHL) 74/1877
Reading (RDG) 68/1962
Trenton (TTN) 70/2017
Wilmington (ILG) 70/2017

Record High Temperatures
May 20
Site Record/Year
Allentown (ABE) 92/1962 & 1996
AC Airport (ACY) 96/1996
AC Marina (55N) 93/1996
Georgetown (GED) 95/1962
Mount Pocono (MPO) 89/1996
Philadelphia (PHL) 94/1962 & 1996
Reading (RDG) 97/1996
Trenton (TTN) 94/1996
Wilmington (ILG) 96/1996

Record Warmest Low Temperatures
May 20
Site Record/Year
Allentown (ABE) 66/2019
AC Airport (ACY) 68/1996
AC Marina (55N) 69/1996
Georgetown (GED) 74/2019
Mount Pocono (MPO) 61/1959
Philadelphia (PHL) 71/2019
Reading (RDG) 69/1959 & 1996
Trenton (TTN) 68/1903, 1959, & 1962
Wilmington (ILG) 70/2019

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory until 8 PM EDT Wednesday for PAZ070-071-102-104-
106.
Heat Advisory until 8 PM EDT this evening for PAZ060>062-101-
103-105.
NJ...Heat Advisory until 8 PM EDT Wednesday for NJZ012-013-015-
017>020-027.
Heat Advisory until 8 PM EDT this evening for NJZ007>010.
Air Quality Alert from 11 AM this morning to 11 PM EDT this
evening for NJZ012>021-026-027.
DE...Heat Advisory until 8 PM EDT Wednesday for DEZ001.
MD...None.
MARINE...Small Craft Advisory from noon today to midnight EDT tonight
for ANZ450>453.

&&

$$

DISCUSSION...AKL/Gorse/MJL
AVIATION...AKL/MJL
MARINE...AKL/MJL

Latest Observation at Wilmington

Data at: 0000 UTC 03 Sep 2023

METAR for:	KILG (Wilmington/New Castl, DE, US)
Text:	KILG 022351Z 17009KT 10SM CLR 23/18 A3009 RMK AO2 SLP190 T02330178 10283 20233 56008
Temperature:	23.3°C ( 74°F)
Dewpoint:	17.8°C ( 64°F) [RH = 71%]
Pressure (altimeter):	30.09 inches Hg (1019.0 mb) [Sea level pressure: 1019.0 mb]
Winds:	from the S (170 degrees) at 10 MPH (9 knots; 4.6 m/s)
Visibility:	10 or more sm (16+ km)
Ceiling:	at least 12,000 feet AGL
Clouds:	sky clear below 12,000 feet AGL