Forecast Discussion From Mount Holly
004
FXUS61 KPHI 090745
AFDPHI
Area Forecast Discussion
National Weather Service Mount Holly NJ
345 AM EDT Fri May 9 2025
.SYNOPSIS...
An upper level system will arrives today with surface low
pressure also crossing our area. This exits the region Saturday
with high pressure building in during the weekend. A weak cold
front however may settle across our area Saturday night into
Sunday. High pressure shifts offshore Monday into Tuesday, then
low pressure looks to arrive from the southwest Wednesday into
Thursday.
&&
.NEAR TERM /THROUGH TONIGHT/...
An upper trough moving towards western Pennsylvania this morning is
expected to close off as it moves towards the Delaware Valley later
today. While this happens, a surface low deepens on the front which
extends from Delmarva and across south NJ. This low and associated
front will bring clouds and rains to the area much of today. Some
residual CAPE across Delaware and ern MD will help produce scattered
tstms across those ares today. Highs will be much below normal with
readings only topping out in the upper 50s to low 60s most areas
with some higher temps for southern Delaware and low/mid 50s for the
far NW areas. Winds will be Northeast to North at 5 to 10 mph. The
winds will switch around to NW later today and speeds will increase
to 10 to 15 mph with gusts 20 to 25 mph developing.
The upper low will be directly across the lower Delaware Valley this
evening while the surface low will be up closer to NYC. Both systems
slowly depart to the NE overnight. This will lead to the rains (from
today) diminishing and clouds decreasing overnight. Winds will
increase overnight with Northwest winds around 10 to 15 mph with
gusts to 20 mph at times. Temperatures will dip into the low 40s
across the N/W areas while readings bottom out in the upper 40s
around Delmarva, south NJ and metro Philadelphia.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Turning warmer with drying conditions through the weekend.
The closed low moves farther away from our area during
Saturday. High pressure is forecast to build into the Ohio
Valley by Saturday night. This combined with the departing low
will result in a tight pressure gradient across our area
Saturday. As deeper mixing develops during the day Saturday,
the west-northwest breeze will increase in strength. The depth
of the mixed layer looks to support wind gusts to around 30 mph
during the daytime, although this should start to
weaken/diminish fairly quickly late in the afternoon and
especially Saturday evening.
As we go through Sunday, some cyclonic flow looks to remain in place
into our area however surface high pressure is forecast to build
across our area. This will result in much less wind and also warmer
temperatures. There should be plenty of sunshine given the drier air
mass in place, although cannot rule out a touch of high level clouds
streaming in from the west and south late with a southern storm
system. Given the lighter flow and warmer temperatures on land, sea
and bay breeze circulations should develop Sunday afternoon which
will offer some cooling closer to the coasts.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Summary...Dry to start, then an increasing chance for showers.
Synoptic Overview...A mid level ridge is forecast to be across our
area as a trough departs the Canadian Maritimes. Meanwhile, a closed
low sliding across the Gulf coast states to the Tennessee Valley is
forecast to gradually move to the northeast and arrive in our region
Wednesday into Thursday. This feature is forecast weaken some as it
arrives. At the surface, high pressure shifts offshore as the mid
level ridge does as well. Low pressure across the Gulf coast states
will lift northeastward and arrive into our region Wednesday into
Thursday. After a dry start, it looks to turn unsettled for the
middle of the week.
For Monday and Tuesday...A southeast to northwest orientated mid
level ridge over our area Monday will gradually shift eastward. This
will continue to shift the center of high pressure farther offshore
during Monday. A southeasterly wind will therefore develop and start
to bring in an increase in the moisture from the south. Meanwhile, a
closed low across the Gulf coast states to the Tennessee Valley is
forecast to slowly lift northeastward through Tuesday. As this
occurs, low-level warm air advection and deeper moisture advection
will strengthen across the Mid-Atlantic. Most if not all of Monday
looks to be dry given the ridge aloft overhead, although some
increase in high clouds should develop. The forecast challenge is
how quick the forcing for ascent starts to arrive into our area.
Some guidance brings this into at least our southern zones by
daybreak Tuesday, then this shifts northward doing Tuesday. As a
result, showers are forecast to be on the increase Tuesday from the
south and some thunder cannot be ruled out if enough instability
develops. While showers are currently in the forecast, it is
possible that a more steady rain could develop. Depending on the
timing, the showers/rain may start to end from south to north later
Tuesday night. While there is a closed low involved, some of the
guidance may be to fast with the forward progression although it may
tend to weaken some as it shifts northeastward.
For Wednesday and Thursday...This time frame will be driven by the
weakening trough across the Northeast and Mid-Atlantic regions. A
surface low will accompany this with it tracking near or over our
area late Wednesday into Thursday. It looks overall to be unsettled
at times however given that at least some heating should occur and
with the trough aloft weakening, high temperatures should be
warming. The chance/extent and intensity of any thunderstorms will
depend on the magnitude of any instability.
&&
.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Today...Poor conditions with widespread IFR and low end MVFR
developing early and persisting into the afternoon. Improvement
beginning late SW and spreading E/NE across the other terminals
into the evening. NE winds 10 to 20 kts shifting to NW this
afternoon. Low/medium confid overall.
Tonight...Improving conditions with decreasing clouds and
improving CIGS from SW to NE this evening then VFR expected
overnight. Gusty NW winds 10 to 15 kts with gusts around 20 kts
at times. Medium confid.
Outlook...
Saturday...VFR. West-northwest winds 15-20 knots with gusts to
around 25 knots, diminishing in the evening.
Sunday and Monday...VFR.
Tuesday...Sub-VFR conditions and showers possible.
&&
.MARINE...
Poor conditions across the waters today and into the evening with
widespread rains and a few tstms as well. Winds and seas will remain
below SCA levels until early tonight when winds will become NW and
gusts will increase to around 25 knots at times. Rains diminish this
evening with fair weather overnight.
Outlook...
Saturday...Small Craft Advisory conditions expected with wind
gusts up to 30 knots across all coastal waters, including the
Delaware Bay, as well as seas up to 5 feet along the ocean
coastal waters. Conditions begin to improve during the afternoon.
Saturday night through Tuesday...The conditions are anticipated
to be below Small Craft Advisory criteria.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 10 PM this evening to 1 PM EDT
Saturday for ANZ430-431.
Small Craft Advisory from 10 PM this evening to 3 PM EDT
Saturday for ANZ450>455.
&&
$$
SYNOPSIS...AKL/Gorse
NEAR TERM...OHara
SHORT TERM...AKL/Gorse
LONG TERM...AKL/Gorse
AVIATION...AKL/OHara
MARINE...AKL/OHara
NWS PHI Office Area Forecast Discussion
