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000
FXUS61 KPHI 251846
AFDPHI

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

.SYNOPSIS...
High pressure builds across the Middle Atlantic region tonight
then moves offshore Friday. A warm front attached to low
pressure over the Great Lakes moves by Saturday. Highs pressure
returns for Sunday and into next week. Another low and front
arrives for 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 SUNDAY/...
A transition from early springlike temperatures Friday night to
early summer readings by Sunday. An upper ridge will build across
the area thru the period and as this happens, low pressure moves
by to the north, bringing a warm front thru on Saturday. There
will be plenty of clouds around, but chances for rain are low
Saturday (slight chance) and only chance levels for Sat night.
The most favored areas for the showers are the Southern Poconos,
Lehigh Valley and north NJ.

Mild and dry weather will be around for Sunday. Following the
warm front, a deep southerly flow will arrive over the area, so
increasing warmth and humidity is expected. Highs Sunday will be
in the upper 70s/low 80s in most spots, but cooler near the
shore and up across the Poconos.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
There are not many changes for the long term with todays forecast.
Very warm temperatures for late spring will remain in place as the
upper ridge starts out across the East late this weekend. Gradually,
this ridge weakens and allows more scattered shortwave energy to
arrive across the area. For Tuesday and into Wednesday, a cold front
will approach the area and the weaken as it moves thru. So, for the
period from Sunday night thru Monday night, a dry forecast is in place.
Tuesday/Tuesday night will feature some scattered shower/tstm activity
and after that, only widely scattered showers are expected for the
midweek and into Thu.

Well above normal temps for Sunday/Monday with highs in the upper
70s/low 80s Sunday and then some 5 to 7 degrees warmer for Monday.
There will be more clouds and showers for Tue, but highs in the 80s
are still expected. Humidity levels will increase into the new week
with dew points rising to the upper 50s/low 60s for many areas.

&&

.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...

Friday night/Saturday... VFR expected.

Saturday night... VFR except in a few scattered showers mostly
KRDG/KABE/KTTN when some MVFR is possible.

Sunday and Monday...VFR conditions anticipated.

Tuesday... Mostly VFR but scattered showers with lower conditions
possible.

&&

.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 Tuesday... Winds and seas will remain below
SCA criteria through the period. Fair weather expected.

&&

.FIRE WEATHER...
RH`s across much of the region will remain quite low this afternoon
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 diminish thru the afternoon while
the lowest RH values occur.

&&

.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...OHara
NEAR TERM...Staarmann
SHORT TERM...OHara
LONG TERM...OHara
AVIATION...OHara/Staarmann
MARINE...OHara/Staarmann
FIRE WEATHER...Staff