374
FXUS61 KPHI 070807
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
307 AM EST Thu Nov 7 2024

.SYNOPSIS...
A weakening cold front settles across our region today and then
dissipates just to our south. Another weak and dry cold front moves
through during Friday. A warm front lifts north of our area later
Sunday, then a cold front crosses our area during Monday. High
pressure then builds in for Tuesday into Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure remains over the Mid-Atlantic ahead of an approaching
cold front. The high moves out to sea with the passage of the cold
front later this morning. Some sprinkles, or perhaps a few light
rain showers are possible with its passage, mainly south of
Philadelphia. Any showers that do develop will result in minimal, at
best, QPF.

Behind the front, northwest winds increase to around 15 mph with 20
to 25 mph gusts. Cold air advection will not develop until late
tonight, so another warm day is on tap for the area. Highs will top
off in the low 70s north and west of the Fall Line, and in the mid
and upper 70s south and east of the Fall Line. A few high
temperature records may be set today, but not nearly as many that
were set on Wednesday.

Although cold air advection will not develop until tonight, a drier
airmass will spread into the region this afternoon with dew points
falling into the upper 40s and low 50s, except dew points remain in
the upper 50s to around 60 for Delmarva and extreme southeast New
Jersey.

Winds diminish fairly quickly after sunset with loss of diurnal
heating. With winds becoming nearly calm and with skies clearing
out, temperatures should drop into the 40s to low 50s prior to
midnight, and then overnight lows will be in the upper 30s to low
40s, except for Philadelphia, Delmarva, and along the coasts where
lows will be in the mid and upper 40s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
The warmth continues Friday followed by cooling to start the
weekend. Dry conditions also continue, with the core of the very dry
air occurring on Saturday.

An upper-level trough is forecast to amplify Friday across the
Northeast, taking surface low pressure north of northern New
England. An associated weak cold front looks to cross our area later
in the day Friday, although the forcing is to our north and moisture
is lacking and therefore a dry frontal passage is expected. There
will be a notable tightening of the pressure gradient associated
with this system, and with a warming boundary layer the vertical
mixing will deepen during the daytime hours. As a result, a breezy
day is expected with wind gusts in the 20-30 mph range. The air mass
will dry out more during the course of the day as dew points lower
through the 40s and 30s, with even drier air arriving at night. A
cooler air mass then settles in Friday night as the winds gradually
diminish.

As we go through Saturday, a ridge aloft crests over our region
Saturday night and sprawling surface high pressure initially over
our area then shifts offshore by Sunday morning. While a much cooler
air mass will accompany the surface high, temperatures should be at
or just above average. A very dry air mass is forecast to be in
place with dew points down into the 20s for much of the region
during the day. As the low-level flow (light) starts to turn out of
the southeast at night, the surface dew points should start to
increase some especially across the coastal plain. The main arrival
of increasing low-level moisture however looks delayed until during
Sunday. Mostly some high level clouds will start to increase at
night.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Summary...Above average temperatures are forecast; Some much needed
rain is probable later Sunday into Monday.

Synoptic Overview...The axis of an upper-level ridge is forecast to
slide offshore of the East Coast to start Sunday. As this is occurs,
an upper-level trough or even a closed low is forecast to lift
across the Plains to the Midwest through Sunday and then slide
across New England and vicinity on Monday. The flow aloft goes more
zonal later Monday into Tuesday, however a trough amplifies across
the Northeast Tuesday before upper-level ridging arrives Wednesday.
At the surface, high pressure is forecast to be centered offshore
Sunday and this assists in more of a return flow. A warm front lifts
north across our area later Sunday, then a cold front moves through
during Monday. High pressure then arrives for Tuesday into Wednesday.

For Sunday and Monday...An upper-level trough or closed low tracks
from the Central Plains to the Midwest through Sunday then it
continues to lift northeastward across New England and vicinity
through Monday. Surface low pressure associated with it is forecast
to track to our north with a cold front crossing our area Monday.
Some of the guidance that had a weaker and farther north track of
the upper-level trough/closed low have trended stronger and farther
east with it now. The more eastward and stronger guidance provides
more forcing for ascent across our area with much more shower
activity. At least some mid to high level moisture from Hurricane
Rafael in the Gulf of Mexico may get drawn into this system, however
these details are less certain given split guidance on where the
hurricane actually tracks. There continues to be an increasing
chance for widespread shower activity later Sunday into Monday,
which would bring much needed rain to the our region. As of now,
0.25-0.50 inches of rain for the area. Showers look to start during
mostly the second half of Sunday, especially at night, with the
arrival of a warm front, an upper-level jet approaching with some
forcing and with a low-level jet aiding in stronger warm air
advection (PoPs increase to the 70-80 percent range). Instability
looks very minimal as the air mass will be recovering from the
initially rather dry low to mid level environment and therefore no
thunder included in the forecast. Temperatures are forecast to be at
or above average ahead of this cold front Sunday, then well above
average Monday with a lag in the cold air advection. Some clearing
should take place from northwest to southeast Monday as drier air
starts to overspread the area in the wake of the cold front.

For Tuesday and Wednesday...The flow aloft may try to go more zonal
for a time however a trough may amplify some across the Northeast
Tuesday. Some ridging aloft then arrives from the west into
Wednesday. This will drive surface high pressure into our area
during this time, although its center may become more shifted to our
north into Wednesday. The next upper-level trough across the Plains
and Midwest will drive surface low pressure across the Midwest to
north of the upper Great Lakes during Wednesday and Wednesday night.
An associated warm front and then cold front are forecast to be
approaching our area later Wednesday night. While some cooling takes
place, temperatures are still forecast to be above average.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Early this morning...VFR. CIGs 050-080. LGT/VRB winds. Some
sprinkles are possible, mainly at KPHL/KPNE/KILG, but restrictions
not expected. High confidence.

Today...VFR, with skies becoming SKC-SCT250 after 18Z. NW winds 5 to
10 kt in the morning, increasing to around 15 kt with 20 to 25 kt
gusts in the afternoon. High confidence.

Tonight...VFR/SKC. NW winds 5 kt or less. High confidence.

Outlook...

Friday and Saturday...VFR. Westerly winds 10-15 knots with gusts 20-
25 knots Friday diminishing at night, then northerly and lighter on
Saturday.

Sunday and Monday...A period of sub-VFR conditions probable along
with some showers, mainly later Sunday into Monday morning.

&&

.MARINE...
Sub-Small Craft Advisory conditions on tap for today and tonight. A
cold front will move across the waters late this morning. SW winds 5
to 10 kt ahead of the front, becoming NW 10 to 15 kt with gusts up
to 20 kt this afternoon. Winds become N tonight. Seas around 3
ft.

Outlook...

Friday and Saturday...Small Craft Advisory conditions, mainly wind
gusts, are forecast Friday night into Saturday morning.

Sunday and Monday...A mainly brief period of near Small Craft
Advisory wind gusts are possible later Sunday into Monday.

&&

.FIRE WEATHER...
A cold front will move through the region later this morning, and a
drier airmass will spread into the region this afternoon. Surface
dew points drop from the upper 50s to low 60s early this morning to
the 40s to low 50s for most of the area this afternoon, except for
Delmarva, where it will take some time for the drier air to arrive.
It will still be warm with highs in the 70s to near 80. This results
in MinRH values generally 35 to 45 percent. Northwest winds will
increase this afternoon to 10 to 15 mph with 20 to 25 mph gusts.
Winds diminish fairly quickly after sunset this evening.

For Friday and Saturday, daytime minimum relative humidity values
are forecast to range from 25 to 35 percent. Westerly winds increase
to 10-20 mph with gusts 25-30 mph during the day Friday, then
gradually diminish Friday night. A lighter northerly wind is
forecast for Saturday. Given the continued very dry conditions and
increased winds, there is an increased risk for rapid fire spread on
Friday.

Showers are forecast to result in a wetting rain later Sunday into
Monday.

Continue to follow burn restrictions and check with your state
and local fire officials for more information

&&

.CLIMATE...
Temperatures may near record territory today in some spots.

Record High Temperatures for November 7th:

SITE                 RECORD / YEAR
Allentown (ABE)..........74 / 1938
AC Airport (ACY).........81 / 2022
AC Marina (55N)..........80 / 2022
Georgetown (GED..........83 / 2022
Mount Pocono (MPO).......71 / 2020
Philadelphia (PHL).......79 / 2022
Reading (RDG)............76 / 2022
Trenton (TTN)............76 / 2022
Wilmington (ILG).........80 / 2022

Record stretch (consecutive days) without measurable
precipitation:

                                            CURRENT
SITE                 RECORD  RECORD DATES  THRU 11/6
AC Airport (ACY)    34 days  Aug-Sep 1995   35 days
AC Marina (55N)     39 days  Aug-Sep 1995   36 days
Georgetown (GED)    34 days  Oct-Nov 2001   40 days
Philadelphia (PHL)  29 days  Oct-Nov 1874   39 days
Trenton (TTN)       38 days  Apr-May 1903   39 days
Wilmington (ILG)    34 days  Jan-Feb 1909   39 days

&&

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

&&

$$

SYNOPSIS...Gorse
NEAR TERM...MPS
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Gorse/MPS
MARINE...Gorse/MPS
FIRE WEATHER...Gorse/MPS
CLIMATE...PHI