894
FXUS61 KPHI 161026
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
626 AM EDT Sun Jun 16 2024

.SYNOPSIS...
Surface high pressure across our area starts to shift offshore
of New England today and will lift a warm front through on
Monday. Building high pressure aloft all of next week will
result in a prolonged stretch of hot and dry conditions with
little to no rain chances.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 6:25AM...No major changes to the forecast at this time.
Conditions remain quiet across the region.

Surface high pressure will be centered just to the north of our
region this morning. With time, this surface high will migrate
eastward looking to shift just offshore for this afternoon and/or
evening. Though we will still feel the influence of the surface high
offshore through tonight, a warm front from the southwest will lift
northwards and approach with time. This warm front is posed to cross
through our region sometime Monday morning.

A dry forecast with quiet conditions is on tap for the near term.
Though the warm front will approach with time tonight, no
precipitation is expected thanks to the strength and proximity of
the surface high. Highs mainly in the upper 70s to low 80s
anticipated for most areas today. Some areas of the urban corridor
could touch the mid 80s while the coastal areas and high elevations
see the low to mid 70s. Overnight lows mainly in the 60s anticipated
for tonight, though the Poconos and higher elevations will see the
mid to upper 50s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
***Heat Advisories Issued for Tuesday***

A building 500mb ridge across the Southeast U.S. will continue to
expand north through the Mid Altantic through Monday as a surface
high pressure system nudges offshore through Tuesday. The net effect
of the high departing is that a warm front will lift through the
region Monday with warm air advection just getting started. Heat
will build through the week, with highs on Monday warming into upper
80s to low 90s with dewpoints in the low 60s. With dewpoints
forecast to not be in the muggy territory, this leads to the overall
Heat Risk to be in the Minor/Moderate categories for Monday
where individuals participating in outdoor activities without
effective cooling or hydration could be at risk of heat related
illness.

On Tuesday, the ridge builds, subsidence enhances and temps are
forecast to increase to the mid to upper 90s with slightly higher
dewpoints. This increases the Heat Risk for PA and inland NJ to
moderate with portions of the I95 corridor increasing to Major.
The concern with the heat is that the temps will be building
throughout the week and externally, this is early season with
increasing numbers of vulnerable communities/events due to
school years ending and a federal holiday in the middle of the
week. Based on current forecast max temperatures, several high
temperature records may be challenged or set. Given these
factors, a Heat Advisory has been issued for the I95 corridor
north and west. Anyone sensitive to heat should take extra
precaution during the day and unfortunately there is more below
as the potential for excessive heat continues the rest of the
week.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Summary...Excessive heat probable with little to no rain chances.

Guidance is unfortunately consistent with the idea that the
forecasted upper air pattern continues to point toward an
extended period of heat across much of the area (high
temperatures 94F+ degrees). There`s been almost no change to
the forecast of an expansive and deep ridge that will be
centered across our region with additional warming expected
through Friday. The 00z GFS this morning came in with a higher
than 600dm ridge centered over the PHI CWA at 500mb on Thursday.
That combined with well above normal 925/850 temps should see
surface temps ranging into the upper 90s for most of the rest of
the week for interior locales. At the minimum, heat advisories
will likely extend beyond Tuesday with the potential to be
upgraded to Excessive Heat Warnings due to the unprecedented
early season heat impacts and duration over the region.

With warm air advection in place during the early potion of the week
and strengthening of the 500mb high towards the end of the week, the
latter half of the week is more likely to be the hottest. The heat
dome will maintain surface high pressure to our east with the
surface flow more out of the south. The southerly flow looks to
be fairly light and the moisture advection is not much, and
therefore surface dew points should not be crazy with this heat.
In addition, many days of hot temperatures tends to lower the
dew points some during peaking and this can be enhanced some by
a dry to drying ground. There will also not be much relief at
night especially in the urban corridor with lows dropping only
into the 70s. The southerly flow however should keep the coastal
areas noticeably cooler than inland, and if the flow is light
enough especially under this ridge then a sea breeze many days
could get farther inland during the later afternoon hours. The
ridge will feature plenty of dry air aloft which tends to limit
cloud development and therefore rain especially given warm air
aloft. As a result, convective chances are little to none.

Eventually guidance starts to indicate that the ridge will push
southward some and elongates more west to east Friday into Saturday
as a trough in south-central Canada starts to flatten the northern
side of the ridge. The main concern for this event is that the multi-
day heat tends to have more impacts especially in urban centers when
combined with less relief at night creating vulnerable populations.
Heat Risk Impacts show Major impacts from Tuesday all the way
through next Sunday.

Confidence is high in widespread heat related impacts across the
region through Friday. Beyond the workweek, the ridge should be
flattening some on the north side Saturday which lowers the heights
some and also the temperatures aloft. However despite this, the heat
looks to certainly continue. There may also be some opportunity for
a few showers or thunderstorms especially for our northern zones
which will be closer to the Canadian trough. Given the presence of
the ridge though, PoPs are only in the 20-30 percent range mainly
across the northern into the central parts of the region at this
point.

&&

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

Today...VFR. Winds generally 5-10 kts will veer from the NE to SE
with time. Some sites may see periods of light and variable winds
before ~18Z today. High confidence.

Tonight...VFR. SSE/SE winds around 5-10 kts veering S with time.
High confidence.

Outlook...

Sunday night through Thursday...VFR with no significant weather
impacts anticipated.

&&

.MARINE...
No marine headlines expected through Sunday night. NE to SE winds
8-12 kts today, S/SE winds 5-10 kts tonight. Seas 2-4 feet.

Outlook...

Sunday night through Thursday...The conditions are anticipated to be
below Small Craft Advisory criteria.

Rip Currents...

With lighter winds around 10 mph and lower waves of 2-3 feet on
Sunday, there will be a LOW risk for the development of
dangerous rip currents for both the New Jersey Shore and
Delaware Beaches.

On Monday, winds will increase back to 10-15 mph but look to be
out of the south. This wind direction would result in largely
shore parallel winds except for the more south facing beaches in
Cape May and Atlantic Counties. Additionally, waves in the surf
zone are forecast to remain 2-3 feet with a short-medium period
swell. Combining all these factors together, we are forecasting
a LOW risk for the development of rip currents on Monday for
now.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory from 10 AM to 10 PM EDT Tuesday for PAZ054-055-
     060>062-070-071-101>106.
NJ...Heat Advisory from 10 AM to 10 PM EDT Tuesday for NJZ001-
     007>010-012-013-015>020-027.
DE...Heat Advisory from 10 AM to 10 PM EDT Tuesday for DEZ001.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Deal/Gorse
NEAR TERM...Wunderlin
SHORT TERM...Deal/Gorse
LONG TERM...Deal/Gorse
AVIATION...Deal/Wunderlin
MARINE...Deal/Wunderlin