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000
FXUS61 KPHI 251801
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
201 PM EDT Thu Apr 25 2024

.SYNOPSIS...
High pressure arrives from the Great Lakes today before
shifting to our northeast and east on Friday. A warm front
should lift north of our area later Saturday, then a cold front
gradually approaches later Monday before moving across our area
later Tuesday.

&&

.NEAR TERM /THROUGH FRIDAY/...
A weak shortwave trough now pushing offshore this afternoon will
keep some scattered to broken mid-level clouds around through
the remainder of the daytime. The isolated morning showers
across the coastal plain have now moved offshore and weakened.
An unseasonably cool and dry airmass has settled into much of
the area as high pressure is building to our northeast. High
temperatures in the mid 50s are some 10-15 degrees below normal.
The cloud cover should gradually diminish into the evening, then
mostly clear skies are anticipated for the overnight period.

High pressure will continue building to the north overnight
with the gradient slacking off considerably after midnight or so.
With drier and cooler airmass in place, the mostly clear skies
and light and variable to calm winds should maximize
radiational cooling, particularly across interior portions of
New Jersey and Pennsylvania. Have kept the forecast leaning
heavily toward the coldest guidance and even adjusted down a
degree or two from there in the typical cold/sheltered
locations across the coastal plain and NW NJ.

The result is near to sub-freezing temperatures and widespread
frost development for much of our Pennsylvania and New Jersey
zones away from the immediate coast and outside of urban
Philadelphia. Therefore, the Freeze Watch was upgraded to a
Freeze Warning in these areas. For urban Philadelphia and points
southwest into Delmarva, temperatures are forecast to fall well
into the mid 30s away from the immediate coast. This is
expected to result in areas of frost development given the light
to calm winds and clear skies. A Frost Advisory was issued to
highlight this threat. Can`t rule out some interior portions
near the MD/DE border dropping to near freezing, but any
freezing temperatures will likely remain isolated enough to
preclude a Freeze Warning there. Inland Cape May County and
coastal Monmouth County were also included in the Frost
Advisory, as winds should become calm enough for a time
overnight to result in some frost development nearer to the
coasts there.

For Friday, the high pressure across New England will begin to
shift offshore. East to southeast winds will increase to near 10
mph across much of the area, keeping a relatively cool maritime
airmass entrenched across the region. However, we will see some
modification of the airmass compared to today, so temperatures
should warm into the low 60s across most areas away from the
coasts which will stay in the 50s. Expect mostly sunny skies and
a cool breeze much of the day.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
An upper-level trough is forecast to shift to our east to start
Friday, allowing high pressure to build across New England and
the Mid Atlantic. After a cold start Friday morning, surface
flow shifts south- southeast by the afternoon to allow some
warming to begin. With mostly clear skies, high temps in the
afternoon should reach low 60s inland. Onshore flow, however,
will help keep the coastal communities and adjacent inland
locations in the mid to upper 50s during the afternoon. Calm
winds and clear skies to start the nighttime hours will aid in
cooling, but increasing clouds overnight will help stave off
runaway radiational cooling. We will still see temperatures dip
into the mid 30s to low 40s with patchy frost possible in the
most sheltered areas.

High pressure shifts offshore Saturday with an approaching warm
front, expected to arrive around the evening timeframe. Winds
will become more southerly with return flow of our offshore high
aiding in the warm air advection we can expect as the warm
front pushes through. That said, the increased cloud coverage
will prevent us from warming up too much, with afternoon highs
expected to reach the upper 50 to low 60s, right around or just
warmer than on Friday. While a few showers cannot be ruled out
with this warm front probabilities and coverage remain rather
minimal with the only mentionable POPs north and west of I-78.
Warmer overnight with the warm front passing through and cloud
coverage preventing much radiational cooling. Lows will be in
the mid to upper 40s.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
High pressure shifts to our south, allowing southwest flow to
really crank up the warm air advection across the region. Sunday
and Monday will look to bring some of the warmest temperatures
we have seen thus far this season with mid to upper 70s on
Sunday and low to mid 80s by Monday afternoon! Mostly dry across
the region during this timeframe as well, though a few isolated
showers or a rumble of thunder cannot be ruled out mainly
across the Poconos where the aforementioned warm front may
linger nearby.

The stacked low shifting across the upper Midwest will slowly
move into central Canada Monday into Tuesday, dragging along a
cold front across the Ohio River Valley and eventually through
the Mid Atlantic. This is where our next best chance for
precipitation will come from and will be highly dependent on the
timing of this low and its associated cold front. At the
moment, some showers will be possible Monday night as the front
gradually approaches the region, but the best chance for showers
and thunderstorms will come Tuesday as the cold front, washing
out at this point, finally arrives. Temperatures remain warm
again Tuesday with upper 70s to low 80s. Not much cooler behind
this weak cold front on Wednesday, however, with a surface high
ridging in from the southeastern US to keep things on the mild
side in the 70s.

&&

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

Rest of today...VFR with SCT to BKN clouds. Easterly winds near
5-10 kts shifting southeast by 22Z. High confidence.

Tonight...VFR. Southeast to east winds 5-10 kts early
diminishing by 06Z to less than 5 kts favoring a northeast
direction. Winds may become locally calm. High confidence.

Friday...VFR. East to southeast winds increasing to near 5-10
kts. High confidence.

Outlook...

Saturday...A period of near MVFR ceilings possible, most likely
Saturday night as a warm front pushes through. Otherwise,
mainly VFR.

Sunday and Monday...VFR conditions anticipated.

&&

.MARINE...
Seas will remain elevated near 5 feet through today south of
Manasquan before gradually diminishing this evening and into the
overnight. Additionally, northeast winds have remained elevated
near 15 kts with gusts near 25 kts, although this will diminish
into the evening. The Small Craft Advisory remains in effect
until 4 AM Friday for the Atlantic zones south of Manasquan. No
additional hazards are expected through Friday with east winds
10-15 kts and seas 2-4 feet.

Outlook...

Friday night through Monday...The conditions are anticipated to
be below Small Craft Advisory criteria.

&&

.FIRE WEATHER...
RH`s across much of the region will get quite low today across
our Pennsylvania and New Jersey zones, and we`ve had little
rain now for a couple of weeks, allowing fine fuels to dry.
Minimum relative humidity values are forecast to drop into the
20-30% range. Northeast to east winds will be strongest this
morning, diminishing into the afternoon when the lowest RH
values are anticipated. Thus, there will be no special
statements issued for danger of fire spread today.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory from 2 AM to 9 AM EDT Friday for PAZ070-071.
     Freeze Warning from 2 AM to 9 AM EDT Friday for PAZ060>062-
     101>106.
NJ...Frost Advisory from 2 AM to 9 AM EDT Friday for NJZ014-023.
     Freeze Warning from 2 AM to 9 AM EDT Friday for NJZ001-007>010-
     012-013-015>022-027.
DE...Frost Advisory from 2 AM to 9 AM EDT Friday for DEZ001>003.
MD...Frost Advisory from 2 AM to 9 AM EDT Friday for MDZ012-015-019-
     020.
MARINE...Small Craft Advisory until 4 AM EDT Friday for ANZ451>455.

&&

$$

SYNOPSIS...Fitzsimmons/RCM
NEAR TERM...Staarmann
SHORT TERM...MJL
LONG TERM...MJL
AVIATION...MJL/Staarmann
MARINE...MJL/Staarmann
FIRE WEATHER...Staarmann