Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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027
FXUS61 KPHI 240003
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
803 PM EDT Mon Oct 23 2017

.SYNOPSIS...
High pressure located off Nova Scotia this afternoon will
continue to lose its influence over our weather. A slow moving
cold front extending from the Great Lakes to the eastern Gulf of
Mexico will progress to the east and it should pass through our
region on Tuesday night. High pressure is expected to nose up
from the southwest and south for the second half of the work
week. Another cold front from the west is anticipated to arrive
on Sunday. Low pressure may develop along the boundary after it
moves off the coast.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
The main change to the forecast overnight has been to increase
wind gusts through the night, especially for higher elevations
across portions of northeast Pennsylvania and northwest New
Jersey. We have expanded the Wind Advisory slightly eastward as
the winds associated with the low level jet ahead of the cold
front may have better potential to mix down to the surface
across these more elevated areas.

Otherwise, cloudy conditions with increasing chance of showers
through the night. A few sprinkles or light showers may occur
this evening, before showers become more widespread after
midnight. The heaviest showers and possible isolated thunder are
expected to begin closer to daybreak Tuesday as a cold front
approaches the area from the west.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
The cold front will move slowly across our area on Tuesday. An
unseasonably warm and humid airmass will continue. Heavy showers
and thunderstorms are likely throughout the day. SPC has placed
our region within a slight risk of severe thunderstorms. There
is ample shear as well as modest SB CAPE, with damaging winds
the primary. But given strong 0-1 km shear and low LCLs, cannot
rule out an isolated tornado, especially in association with any
Quasi Linear Convective System. In addition, any heavier
showers and t-storms will have the potential to tap the stronger
winds aloft and produce wind gusts up to around 40 mph. The
heaviest rainfall should be confined from the PA Turnpike east
to Ocean County and points north, with the main concern being
urban and poor drainage flooding. The severe weather and flood
threat have been included in the Hazardous Weather Outlook.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
A mid level trough is forecast to drift over the eastern states
from Tuesday night into Thursday. Ridging is expected to take
place from Thursday night into Saturday before another trough
affects the eastern states on Sunday and Monday.

A slow moving cold front is expected to extend through our
region on Tuesday evening. It should continue moving slowly
eastward and it is anticipated to be off the coast on Wednesday
morning. Rain is forecast to end gradually from west to east in
our region from Tuesday evening into Wednesday. Moderate to
heavy rain and a chance of thunder will linger in our eastern
counties on Tuesday evening.

The clouds and lingering showers associated with the front will
likely be slow to move away from our region on Wednesday. It
will take the arrival of the axis of the mid level trough on
Thursday to finally kick the system well to our east.

Surface high pressure from the southwest and south is
anticipated to build into our region for Thursday night into
Friday night, resulting in some clearing.

Another cold front approaching from the west is forecast to
bring an increase in cloud cover for Saturday. It is expected to
be another slow moving boundary, so we have mentioned a chance
of showers for Saturday night, Sunday and Sunday night.

The coldest air mass of the season to affect our region is
expected to arrive in the wake of the cold front for early next
week.

Temperatures should not be far from normal for the period from
Wednesday through Sunday, then then should begin to fall below
normal on Monday.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

VFR conditions are beginning to lower early this evening for
some areas, and everyone should be MVFR by 03z-06z as scattered
showers begin to move into the area. Conditions will continue
to deteriorate overnight as showers become heavier toward
daybreak Tuesday and continue through the day. There is also a
chance of thunderstorms during the day Tuesday, especially for
southeast Pennsylvania, New Jersey, Delaware, and Maryland.

Southeast winds will gust 20 to 30 knots at all TAF sites
tonight into Tuesday, with higher wind gusts are possible in
and around thunderstorms. Winds will gradually shift to the
south and southwest on Tuesday afternoon, with a gradual
improvement to VFR for some areas expected as the front and
rainfall move eastward.

OUTLOOK...
Tuesday night...MVFR and IFR conditions in showers for some
areas improving to VFR.

Wednesday through Saturday...Mainly VFR.

&&

.MARINE...
SCA remains in effect for the Atlantic and Delaware Bay waters
through Tuesday. South-southeast winds will gust up to around 30
knots at times. There is the potential for a short period of
gale-force gusts for a couple hours around dawn Tuesday
morning, then in and around and heavier showers and
thunderstorms Tuesday afternoon and evening. Seas will also
increase up to 9 feet on the ocean, and 5 feet at the entrance
to DE Bay on Tuesday.

OUTLOOK...
Tuesday night...A Small Craft Advisory is in effect for our
ocean waters. We are expecting a south wind around 20 knots
becoming west and diminishing around 10 knots. Gusts around 30
knots are possible on Tuesday evening on our ocean waters. Wave
heights are anticipated to be 6 to 9 feet on our ocean waters.

Wednesday...A Small Craft Advisory is in effect for our ocean
waters with wave heights expected to be 4 to 6 feet.

Wednesday night through Thursday morning...A Small Craft
Advisory may be needed on our ocean waters for wave heights
around 5 feet. Winds should be west to northwest around 10 to 15
knots.

Thursday afternoon through Saturday...No marine headlines are
anticipated.

&&

.HYDROLOGY...
Hydro: storm total rainfall Tue-Tue night, generally 1-2" with
in excess of 2 inches most favored over NJ. Leaf-clogged drains
will enhance the possibility of ponding of water on roadways.

&&

.CLIMATE...
Vulnerable record high minimums Tuesday the 24th:

Allentown     58 1975

Atlantic City 63 2001

Philadelphia  63 1900

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Wind Advisory from 1 AM to 8 AM EDT Tuesday for PAZ060>062.
     Wind Advisory until 8 AM EDT Tuesday for PAZ054-055.
NJ...Wind Advisory from 1 AM to 8 AM EDT Tuesday for NJZ001-007.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT Wednesday for ANZ450>455.
     Small Craft Advisory until 6 PM EDT Tuesday for ANZ430-431.

&&

$$
Synopsis...Iovino
Near Term...Franck/Johnson/Robertson
Short Term...Franck
Long Term...Iovino
Aviation...Franck/Iovino/Robertson
Marine...Franck/Iovino
Hydrology...Staff
Climate...Staff



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