Royersford, Pennsylvania Weather Forecast Discussion

186
FXUS61 KPHI 271049
AFDPHI
Area Forecast Discussion
National Weather Service Mount Holly NJ
649 AM EDT Sat Sep 27 2025
.SYNOPSIS...
A front will settle south of the area, where it will remain
into the weekend and early next week. A few waves of low
pressure will move along it creating unsettled weather at times.
Another cold front will pass through the area mid-week,
followed by strong high pressure building southward in its wake.
&&
.NEAR TERM /THROUGH TONIGHT/...
Weak high pressure over the area slides offshore later today.
Meanwhile, a stationary boundary lies over the Mid-Atlantic and
that will lift north as a warm front tonight as developing low
pressure over the Southeast lifts to the north tonight. This
system will move into the Mid-Atlantic late tonight, and then
will pass east of Delmarva and southern New Jersey by daybreak
Sunday.
Patchy fog will develop prior to daybreak, and any patchy fog
will lift and dissipate shortly after sunrise. Clouds will
increase and thicken over the area as that boundary begins to
lift to the north. Relatively warm and humid today, at least by
late September standards, with highs in the upper 70s to around
80 and dewpoints in the mid 60s.
Some showers may lift into Delmarva and extreme southern New
Jersey by this afternoon, but rainfall will be light. Showers
will continue to lift from south to north this evening and
through the overnight. Cannot rule out a rumble of thunder or
two, but not expecting widespread or organized convection. Lows
tonight will generally be in the low to mid 60s. Rainfall
amounts will generally be less than 1/4 inch north and west of
the Fall Line, and 1/2 inch to 1 inch along and south and east
of the I-95 corridor with the highest amounts in Delmarva and
southern New Jersey. Cannot rule out locally higher amounts up
to 2 inches of rain if there is any training of thunderstorms.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Weak low pressure pulls away on Sunday and it should be a
mainly dry day, however the upper level trough doesn`t move out
until late in the day, keeping partly to mostly cloudy skies
south and east of the I-95 corridor, with clearing skies north
and west. Cannot rule out a few lingering showers near the coast
either, especially in the first half of the day. Temperatures
get into the low 80s where the sun comes out (the Philly metro
and points north and west) with mid to upper 70s within the
coastal plain. High pressure begins to usher in from the
northwest on Sunday night, though cannot rule out some patchy
fog on Sunday Night.
Confidence is increasing in a large and expansive area of high
pressure slowly building in for the early part of the week, and
keeping any tropical systems from inching northward toward our
area. The result will be a relatively nice start to the week,
with the only impacts looking to be marine or coastal related in
regard to the systems to the south. Only a slight chance of
showers for areas south of Philadelphia through Monday through
Tuesday and temperatures in the mid to upper 70s to even low
80s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Canadian high pressure moves in for the middle and end of next
week, resulting in a stretch of dry weather and below normal
temperatures. Highs look to struggle to even reach 70 with
overnight lows in the 40s. Any tropical system to our south
looks to stay that way or even go out to sea with the high
dominating over our region.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...
Today...Any fog will lift and dissipate by 13Z or so, then VFR.
E winds 5 to 10 kt, turning SE this afternoon. High confidence.
Tonight...Sub-VFR in SHRA. NE winds around 5 kt. Low
confidence.
Outlook...
Sunday...Primarily VFR though some lingering IFR/MVFR
restrictions possible (30-50%)
Sunday Night...Primarily VFR, though some patchy fog possible
(40- 50%)
Monday through Wednesday...VFR. No significant weather.
&&
.MARINE...
Sub-Small Craft Advisory conditions today and tonight. East to
northeast winds 10 to 15 kt. Seas 2 to 3 feet.
Visibility restrictions in showers starting late this afternoon
over southern ocean waters, but the bulk of the activity will
occur tonight. An embedded thunderstorm or two are possible.
Outlook...
Sunday through Monday Night...No marine headlines expected.
Tuesday through Wednesday...Winds and seas both increase with
distant tropical systems offshore. Wave heights of 7 to 11 feet
expected with at least SCA winds expected and gales possible
(mainly on Wednesday).
Rip Currents...
For today...Northeasterly wind 5-10 mph becoming easterly in
the afternoon. Breaking wave heights generally 1-2 feet. Swell
from offshore storms remains insignificant in height and period.
Given these factors, have opted to maintain a LOW risk for the
development of dangerous rip currents at all beaches.
For Sunday...Mainly northeasterly wind at 5-10 mph. Breaking
wave heights generally 1-2 feet. A southeasterly swell from
offshore storms starts to increase late in the afternoon.
Initially, our period is 6-8 seconds but does start to increase
later in the afternoon with the potential for a longer period
swell developing at a period of around 10 seconds. Given these
factors, have opted to maintain a LOW risk for the development
of dangerous rip currents at all beaches at this time.
For specific beach forecasts, visit weather.gov/beach/phi
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.
&&
$$
SYNOPSIS...Cooper/Hoeflich/Staarmann
NEAR TERM...MPS
SHORT TERM...Hoeflich
LONG TERM...Hoeflich
AVIATION...Hoeflich/MPS
MARINE...Hoeflich/MPS

NWS PHI Office Area Forecast Discussion