196
FXUS61 KPHI 081732
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1232 PM EST Fri Nov 8 2024

.SYNOPSIS...
A dry cold front moves through late today or this evening, then high
pressure builds in during Saturday before shifting offshore into
Sunday. A warm front lifts into or north of our area later Sunday,
then a cold front crosses our region during Monday. High pressure
builds in for Tuesday into Wednesday, followed by a warm front and
cold front approaching on Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Forecast remains on track. RH values have dropped to 30% or less
with widespread wind gusts over 20 mph early this afternoon.

Low pressure over central Canada will dive towards the Canadian
Maritimes later today, and this will drag a cold front through
the region tonight. Meanwhile, high pressure will strengthen
over the Central Plains and Midwest late tonight.

Sunny skies on tap for today along with dry conditions. Highs
will be some 7 to 10 degrees cooler today compared to Wednesday,
topping off in the upper 60s to low 70s. A brisk northwest flow
will develop, with winds this afternoon increasing to 15 to 20
mph with 25 to 30 mph gusts.

Winds diminish this evening after sunset, however, winds will
still be a bit gusty, ranging from 10 to 15 mph with gusts up to
20 mph for most of tonight. Lows tonight will range from the
30s to low 40s.

A Red Flag Warning is in effect for today. See the Fire Weather
section below.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
Temperatures near average as strong high pressure builds in from the
west and northwest.

As an upper-level trough lifts across the central to northern Plains
during Sunday, a downstream ridge builds and shifts eastward into
our area. This will support strong surface high pressure building
into our area from the west and northeast during the day Saturday
before settling right over our area Saturday night. This will
deliver a much cooler air mass and also a very dry air mass. A
lingering pressure gradient ahead of the incoming surface high will
result in a northerly breeze, however this should be most notable
during the first half of the day as the winds should diminish in the
afternoon and especially early in the evening.

As mentioned, a very dry air mass is forecast to be in place with
dew points down into the upper teens to low 20s for much of the
region during the day. Despite the cooler temperatures, dew points
this low will drive down the relative humidity. See the fire weather
section below for more on the fire danger risk.

While the wind at the surface should decouple nearly everywhere at
night as the surface high settles right over us, the flow just above
the surface while light starts to turn out of the southeast. This
will result in the surface dew points starting to recover 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, however
probably late and thin enough to get temperatures to drop into the
30s for most locations.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Summary...Temperatures closer to average, although much above
average on Monday. Some much needed rain later Sunday into
early Monday, then another chance Wednesday night and Thursday.

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 the Northeast on Monday. Some cyclonic flow is forecast to
remain in place Tuesday before some upper-level ridging arrives into
Wednesday. The next upper-level trough is forecast to approach late
Wednesday and/or Thursday. 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 into or north of our area later Sunday,
then a cold front moves through during Monday. A secondary cold
front may move through during Tuesday, then high pressure arrives
for later Tuesday into Wednesday. A warm front arrives Wednesday
night with a cold front approaching from the west during Thursday.

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 the Northeast through Monday.
Surface low pressure associated with it is forecast to track to our
north with a cold front crossing our area Monday. At least some mid
to high level moisture from Hurricane Rafael in the Gulf of Mexico
may get drawn into this system. Despite this there continues to be
increased chances for widespread shower activity later Sunday into
early Monday, which will bring much needed rain to the our region.
The amount of rain will not break the ongoing drought however 0.25-
0.50 inches of rain is certainly something and this will end the
lengthy consecutive days of no measurable rain. Some guidance is a
bit faster with the onset of showers during the day Sunday, however
initially some lingering dry low-level air should delay these at
least some. Therefore, showers look to start during the second half
of Sunday, especially at night, with the arrival of a warm front. An
upper-level jet approaching with some added forcing and with a low-
level jet at 850 mb results in a period of strengthening warm air
advection. All of this is expected to produce a period of forcing
for ascent and result in the air mass moistening and therefore
showers. The PoPs continue to 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 much closer to average Sunday given the cloud cover
and the incoming showers, 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 through Thursday...An upper-level trough is forecast to
briefly amplify across the Northeast Tuesday before lifting out.
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 and Great Lakes
during Wednesday and Thursday. An associated warm front will arrive
Thursday with a cold front then approaching later Thursday. There
are some timing differences within the guidance, with some much
slower and therefore keeping any showers well removed from our area
even through Thursday. Given the uncertainty, went with mainly the
NBM PoPs (slight chance to chance) for Wednesday night and Thursday.

&&

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

Rest of today (through 00Z)...VFR/SKC-SCT250. W-NW winds 10 to
15 kt with 20 to 25 kt gusts. High confidence.

Tonight...VFR/SKC. NW winds 10 to 15 kt with gusts up to 20 kt,
diminishing to around 10 kt after 06Z. High confidence.

Saturday...VFR. Northerly winds around 10 knots. Terminals
around I-95 could gust to 15kts in the morning before
diminishing later in the afternoon and especially at night. High
confidence.

Outlook...

Saturday...VFR. Northerly winds 8-12 knots, diminishing later in the
afternoon and especially at night.

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

Tuesday...VFR.

&&

.MARINE...
NW winds around 10 kt will ramp up to 10 to 15 kt with gusts up to
20 kt this afternoon. Tonight, winds increase to 15 to 20 kt with
gusts up to 30 kt. Seas on the ocean will build to around 5 feet. A
Small Craft Advisory remains in effect for all waters tonight.

Outlook...

Saturday...Small Craft Advisory conditions mostly on the ocean
zones, mainly due to wind gusts to 25-30 knots in the morning.

Sunday and Monday...A period of Small Craft Advisory conditions
possible, especially wind gusts, Sunday night into Monday.

Tuesday...The conditions should be mostly below Small Craft Advisory
criteria.

&&

.FIRE WEATHER...
Sunny and dry today with a gusty west to northwest flow
developing. MinRH values will range from 25 to 35 percent during
the day along with west to northwest winds increasing to 15 to
20 mph with 25 to 30 mph gusts. With a lack of rain over the
last month or so, very dry fuels are in place. The combination
of these dry fuels, along with the gusty winds and low humidity
values result in a Red Flag Warning in place for the whole
forecast area.

For Saturday, a very dry air mass will be in place with dew
points down into the upper teens to lower 20s. Daytime minimum
relative humidity values are forecast to be in the 20-30 percent
range. Northerly winds 10-15 mph should diminish some during
the afternoon. Although the winds are lighter compared to
Friday, the conditions continue to be very dry and thus an
elevated risk for fire spread remains.

Showers are forecast to result in a wetting rain (0.25-0.50
inches currently forecast) later Sunday, especially at night,
into Monday morning.

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

&&

.CLIMATE...
Record stretch (consecutive days) without measurable
precipitation:

                                            CURRENT
SITE                 RECORD  RECORD DATES  THRU 11/7
AC Airport (ACY)    34 days  Aug-Sep 1995   36 days
AC Marina (55N)     39 days  Aug-Sep 1995   37 days
Georgetown (GED)    34 days  Oct-Nov 2001   41 days
Philadelphia (PHL)  29 days  Oct-Nov 1874   40 days
Trenton (TTN)       38 days  Apr-May 1903   40 days
Wilmington (ILG)    34 days  Jan-Feb 1909   40 days

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Red Flag Warning until 6 PM EST this evening for PAZ054-055-
     060>062-070-071-101>106.
NJ...Red Flag Warning until 6 PM EST this evening for NJZ001-
     007>010-012>027.
DE...Red Flag Warning until 6 PM EST this evening for DEZ001>004.
MD...Red Flag Warning until 6 PM EST this evening for MDZ012-015-
     019-020.
MARINE...Small Craft Advisory from 6 PM this evening to 7 AM EST
     Saturday for ANZ430-431.
     Small Craft Advisory from 6 PM this evening to 9 AM EST
     Saturday for ANZ450>455.

&&

$$

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