372
FXUS61 KPHI 260813
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
413 AM EDT Wed Jun 26 2024

.SYNOPSIS...
A weak ridge of high pressure shifts offshore this morning. A low
pressure system and its associated front will move towards eastern
Pennsylvania later Wednesday and then move offshore by Thursday
morning. More high pressure moves in for the last past of the week.
Another disturbance will be across the area for the weekend before a
more tranquil pattern returns to start off the month of July.

&&

.NEAR TERM /THROUGH TONIGHT/...
345 AM...As of early this morning, high pressure was centered well
off to our south and east over the Atlantic with low pressure over
far northern Quebec. A trailing cold front associated with this
system extended back to the west and southwest through northern
Ontario into the Great Lakes region. Farther south, convection
continues across portions of the midwestern states.

The setup described above will help lead to a return of hot, humid
conditions across much of the area for today as southwest return
flow will lead to increasing temperatures and dewpoints. No changes
were made to the Heat Advisory as we still expect areas near and
south of the urban corridor (except the immediate coast) to see
maximum heat indices reaching around or over 100.

In addition to the heat and humidity, we are still looking at a
threat for severe weather by late day into this evening. There will
be plenty of instability across the area with ML CAPE values likely
reaching 1000-2000 J/kg, deep layer shear values increasing to 30-
40+ knots, and fairly steep mid level lapse rates around 6.5 to 7.5
C/km. Also noted in the progged soundings and hodographs is strong
low level shear and helicity values. We remain in a SLIGHT risk for
severe weather from the SPC, with damaging winds being the main
threat due to DCAPE values in the 1000+ J/kg range although there
will be a chance for large hail, and an isolated tornado or two.
Heavy rainfall will also be possible with any thunderstorms as PW
values approach 2 inches, but they should be progressive enough to
preclude a widespread flash flood threat. Locally though there could
be some flooding or flash flooding in and around urban and/or low
lying areas. In terms of timing, expect an area of widespread
showers and storms to be working across western into central PA by
the late afternoon time frame. This will be driven in part by a
fairly strong upper level short wave. Ahead of this main area of
storms, storms may start to fire across eastern PA into NJ and
northern Delmarva by around the 21z time frame along a surface
trough setting up over the area. CAMs still struggling to resolve
these details with some notable differences between individual
models regarding specific details of convection initiation over the
area around this time. Some of the guidance holds off most of the
convection over our area until later in the evening when the main
area comes through from the west. The upshot of all this is that
some areas could see multiple rounds of storms during the 5 PM to
midnight time frame. In terms of convective mode, initial cells
ahead of the main area of storms could be more discrete in nature
but with the potential for fairly quick upscale growth to lines
and/or line segments due to merging cold pools. However given the
strong low level and deep layer shear, supercells or supercells
embedded within lines/clusters will certainly be possible.

Expect widespread showers/storms in the evening to diminish from
west to east during the overnight hours as a cold front moves
through. Clouds will remain most of the night most areas. Lows will
drop into the low 60s across the far NW areas where cold air
advection will begin before Thu. morning. Other areas will remain
mild/humid with lows mostly mid/upper 60s to around 70. Winds will
turn W/NW overnight and remain around 10 mph with some gusts 20-25
mph early.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Thursday morning could start off with some lingering showers and
storms across the southern Delmarva and Jersey Shore as the frontal
boundary continues to push offshore, but high pressure will build in
quickly in its wake. Fair weather is expected for the rest of
Thursday and into Friday as high pressure arrives from the Midwest
Thu and crests over the area Fri. Dry weather with seasonable
temperatures are expected. Highs will favor the mid/upper 80s for
both days. Humidity levels will be comfortable by in large with dew
points in the 60s Thu and 50s for Fri. For Thursday night, mostly
skies and a calm north wind could pave the way for one of the
coolest nights we`ve seen in some time with lows in the upper 50s to
mid 60s across much of the region with low to mid 50s for the high
elevations. Greater cloud coverage Friday night will prevent
efficient radiational cooling with lows only expected to drop into
the low 60s to around 70.&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The final days of June will be warmer with seasonable temperatures
Saturday and above climo temperatures Sunday. Humidity will increase
as well, rising dew points back into the 70s. Our last day of the
month (Sunday) could bring back heat indicies over 100 in many areas
as a result. While the heat builds there will also be opportunities
for showers and a few tstms too as shortwave energy and a few
surface front move towards the area from the Great Lakes area.
Scattered showers and storms can be expected Saturday with a better
chance of storm coverage arriving Sunday with a stronger front
pushing through the region to break the heat.

As July arrives, cooler and drier air drops down from the N/W areas
and brings more temperate conditions. Highs Mon/Tue will be in the
low/mid 80s most areas with comfortable humidity levels too. Not
much in the way of disturbances for the new week, so pops will be
low and skies should be mostly sunny both Mon/Tue.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through today... Mostly VFR conditions expected. Chance of showers
and thunderstorms in the afternoon (mainly after 20z) which may lead
to lower conditions. Southwest to west winds 5-10 knots, occasional
gusts 15-20 knots in the afternoon. Stronger winds in thunderstorms.

Tonight... Showers and tstms with lower CIGS/VSBYS will be moving
through during this period...mainly before 6z. MVFR or possible IFR
conditions with the rains/storms. Conditions improve late from west
to east. Southwest winds 5 to 10 knots in the evening shifting to
northwest late at night. Higher wind gusts possible in any
storms...potentially even exceeding 35 knots.

Outlook...

Thu thru Friday... Mostly VFR expected.

Sat/Sunday... VFR most of the time, but scattered showers/tstms with
lower conditions at times. Most likely times for sub-VFR and storms
are Sat evening/night and again Sun evening/night.

&&

.MARINE...
Marginal Small Craft Advisory conditions continuing today into
tonight over the ocean waters. Showers/storms also expected over the
waters this evening into the overnight and these could contain wind
gusts exceeding 40 knots.

Outlook...

Thu thru Fri night...Sub-SCA expected. Fair weather.

Sat/Sat night/Sunday... Scattered showers tstms Sat becoming more
numerous Sunday. Low-end SCA winds and seas developing Sat afternoon
and lasting into early Sunday.

Rip Currents...

Wednesday...South to southwest winds increasing to 15-20 mph,
with breaking waves building to 3 to 5 feet along the NJ shore
and 2 to 3 feet along the DE beaches. With winds parallel to
slightly onshore, have upgraded to to a HIGH risk of rip
currents for the Jersey Shore but kept a MODERATE risk for the
Delaware beaches.

Thursday...West to northwest winds of 10 to 15 mph in the
morning become variable in the afternoon. Breaking waves will
decline from 2-4 feet early to 1-2 feet late, with lowest along
the DE coast. Thus, went with a MODERATE risk along the Jersey
shore and a LOW risk along the Delaware beaches.

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

&&

.CLIMATE...
Record high temperatures for today.

Location               Record High (6/26)
Philadelphia, PA.......100/1952
Allentown, PA..........99/1952
Reading, PA............102/1952
Mount Pocono, PA.......92/1952
Trenton, NJ............100/1952
AC Airport, NJ.........98/1952
AC Marina, NJ..........99/1952
Wilmington, DE.........99/1952
Georgetown, DE.........99/1952

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory from 9 AM this morning to 9 PM EDT this evening
     for PAZ070-071-102-104-106.
NJ...Heat Advisory from 9 AM this morning to 9 PM EDT this evening
     for NJZ010-012-013-015-017>020-027.
     High Risk for Rip Currents from 8 AM EDT this morning through this
     evening for NJZ014-024>026.
DE...Heat Advisory from 9 AM this morning to 9 PM EDT this evening
     for DEZ001.
MD...Air Quality Alert until midnight EDT tonight for MDZ012-015.
MARINE...Small Craft Advisory until 6 AM EDT Thursday for ANZ450>453.
     Small Craft Advisory until 11 PM EDT this evening for ANZ454-
     455.

&&

$$

SYNOPSIS...MJL
NEAR TERM...Fitzsimmons
SHORT TERM...MJL/OHara
LONG TERM...MJL/OHara
AVIATION...Fitzsimmons/MJL
MARINE...Fitzsimmons/MJL
CLIMATE...