525
FXUS61 KPHI 041851
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
251 PM EDT Sat May 4 2024

.SYNOPSIS...
Stationary boundary keeping the region unsettled today lifts
northwards as a warm front tonight and Sunday. Cold front
approaches Sunday night into Monday looking to cross through
later Monday/Monday night. Cold front becomes nearly stationary
over the region for Tuesday/Wednesday/Thursday, keeping things
unsettled. Another cold front looks to come through between the
Thursday night and Friday night time frame.

&&

.NEAR TERM /THROUGH SUNDAY/...
Latest analysis depicts a backdoor cold front extending from the
Virginia capes northwestward toward western Pennsylvania and
north across the eastern Great Lakes. Another cold front moving
southeast from Canada is washing out over the eastern Great
Lakes. A third cold front is pushing southeast across the
western Great Lakes and north/central Plains. Aloft, a ridge
straddles our region north to south, but several weak shortwaves
are located over the upper Ohio Valley and southeastern US,
with more further west over the central Plains.

Weak warm advection above the cool marine layer will allow
showers to continue through Sunday, but the main mid and upper
level forcing will remain mostly to our west in central PA.
Thus, expect relatively dry conditions near the immediate coast,
with the bulk of precip near Chesapeake Bay and across western
Chester, Berks and the Poconos through Sunday afternoon. That
said, enough shortwave energy finally pushes eastward over the
region by then to allow more organized showers to cross much of
the remainder of the region, so have POPs maxing out Sunday
afternoon, but even then, still keep them below categorical from
I-95 south and east. QPF looks relatively light given the long
duration as well, with less than an inch area-wide and less than
a half inch from I-95 corridor on south and east, with almost
nothing near the coast. All that being said, it still won`t be
very nice, as the persistent easterly flow will keep skies
cloudy and temps cool, mostly 40s to near 50 at night and 50s
and 60s during the day. The warm front does try to lift
northward late on Sunday, so that gives areas from Philly south
the opportunity to approach (but not reach) normal, but it`ll
be a struggle.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
Unsettled conditions persist Sunday night as a cold front from
the west approaches. Cold front will be rather slow getting
here, still approaching our region Monday and crossing through
perhaps either later Monday or Monday night. Thereafter,
guidance suggests the cold front may stall over or close by the
region Monday night into Tuesday.

Given this synoptic situation, an unsettled short term looks to
be on the horizon. Though unsettled, the short term will not be
all that impactful, just showery in general. Precipitation will
not amount to much across the region during the term, maybe
0.25 inches at most. Our region is not currently outlooked by
the WPC for any excessive rainfall or the SPC for any severe
weather. Likely and categorical PoPs Sunday night will diminish
with time, mainly chance PoPs for the periods thereafter.

Great support from model soundings for fog/low stratus development
Sunday night; PBL should be nice and saturated, RHs 90-100%.
Some lighter and less impactful fog development is possible for
some areas Monday night, but much less support from model
soundings for this period is noted.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Once again, an unsettled and showery forecast looks to be tap for
the long term. Cold front forecast to come through the region Monday
into Tuesday is likely to stall over or close by thereafter,
becoming a stationary front. Though this boundary may lift a
little northwards some with time (resembling a warm front), the
boundary will remain stationed over the region for
Tuesday/Wednesday/Thursday, perhaps even into the Thursday
night time frame. Another cold front looks to approach
Thursday/Thursday night, but when the cold front comes through
at this point is not uncertain. Cold front could cross through
anytime between the Thursday night and Friday time frame.
Weakness in the upper-levels will be present during the long
term; this adds a great deal of uncertainty in the timing of
features and synoptic progression.

Forecast will include mainly chance PoPs through all the periods of
the term. Not really seeing anything too impactful to draw
attention to at this point (i.e., severe weather or excessive
rainfall). Temperatures look to run above average through much
of the term.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of today...VFR to MVFR with spotty showers. Best conditions
around KTTN where showers will struggle longest to reach. Winds
easterly 5-10 kts. Moderate confidence.

Tonight...dropping to IFR cigs most of the area, but not much
reduction in vsby except in showers. Showers common western
terminals, minimal if any eastern terminals, but low cigs likely
regardless. Winds remaining mostly east 5-10 kts. Moderate
confidence.

Sunday...IFR cigs most of the day, with IFR or low MVFR vsby
likely by afternoon esp where showers most common, which will be
western terminals. Winds remaining mostly east 5-10 kts.
Moderate confidence.

Outlook...

Sunday night through Thursday...Mainly sub-VFR with chances for
SHRA during most periods. A few periods may see VFR conditions
return.

&&

.MARINE...
Sub-Small Craft Advisory conditions through Sunday. Ocean waves
2-4ft with easterly winds 10-15 kts and a few gusts up to 20
kts. Intervals of reduced vsby in spotty showers.

Outlook...

Sunday night through Wednesday night...No marine headlines
anticipated. Mostly cloudy with chances for showers.

Thursday...SCA flag possible. Seas may build to 5 feet in some
locations, wind gusts increase to 20-25 kts. Chance of showers
(40-60%).

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Wunderlin
NEAR TERM...RCM
SHORT TERM...Wunderlin
LONG TERM...Wunderlin
AVIATION...RCM/Wunderlin
MARINE...RCM/Wunderlin