Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 230742
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
342 AM EDT MON MAY 23 2016

.SYNOPSIS...
A surface low pressure system offshore and also over the upper
atmosphere will influence our weather today through Tuesday. High
pressure will ridge across the area Tuesday night and Wednesday. A
weak cold front will move towards the area Wednesday night. A few
weak disturbances will keep unsettled summer like conditions for
Friday and into the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Another unsettled day is expected across our region, however a
warmer day for most is also expected. This unsettled weather is
courtesy of a large upper-level trough in the east, with a closed
low centered to our south that pivots offshore during the course of
the day. This closed low will drive another surface low east of the
North Carolina coast. This surface low will help keep the winds out
of the northeast overall. The forecast challenges today is the
extent of the warming and the coverage/timing of showers and thunder.

The day will start with fog in some areas as the clouds have thinned
in combination of light/calm winds and a moist low-level
environment. This fog is expected to dissipate quickly this morning
and not be widespread dense, however locally dense fog has been
reported in a few places. Some light showers will occur early this
morning mainly across our southeastern zones.

Our attention then turns to the presence of the upper-level trough.
There continues to be plenty of short wave energy revolving around
it, however there appears to be a convergence area aloft on the west
side of a thermal trough. This promotes lift with even the hint of a
surface trough reflection this afternoon. The model guidance,
including soundings, shows MLCAPE increasing to about 200-500 J/KG
this afternoon. Given the colder air aloft with decent boundary
layer heating, some low-topped thunderstorms should develop. This
looks more likely across the interior and away from the cooler ocean
influence. If the amount of instability is sufficient enough, then
small hail cannot be ruled out with a few stronger cells. The
showers/storms will tend to move from northeast to southwest given
the steering flow. These may be slower moving as well and get some
assistance from terrain circulations. We placed the highest pops
(likely) from about I-95 on westward.

As for the high temperatures, we used a GFS/NAM blend then made some
local tweaks. We are expecting many areas to get into the 70s prior
to the showers developing, although it will be cooler along the
coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
The center of the closed low is forecast to be slowly shifting to
the northeast off of our coast. This will continue to take a surface
low out to sea. The model guidance indicates that forcing may hang
on for awhile tonight. This would result in showers and some
thunderstorms to start the evening gradually weakening from west to
east. An enhanced area of lift to the northwest side of the closed
mid level center may result in an organizing area of showers across
the eastern area for awhile tonight. As a result, the pops were
increased to likely for a time. Any thunder should be confined to
early in the evening as boundary layer cooling sets in which may be
enhanced by rain-cooled air.

Given the more potential for a period of enhanced lift across
portions of our area in combination of convective cloud debris,
there should be a decent amount of clouds around through the night.
This would limit any fog formation and also slow the cooling trend.
As a result, we used a MOS blend for the low temperatures but then
adjusted them upward a little bit for most places.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
The last of the influences of the recent upper low across the Middle
Atlantic region and northeast will be affecting our area during
Tuesday. Pops were not changed much from earlier...in the chc range
n/e and slgt chc range s/w. There will still be enough cold air
aloft and sfc moisture to trigger a few showers or perhaps a
isolated tstm across the area. Temperatures will be near normal with
low/mid 70s in most areas.

A period of drier weather and much milder temperatures is slated for
Tuesday night into Wednesday Night. High pressure, rather weak, will
move across the area. Afternoon maximum temperatures Wednesday will
be in the 80s in most areas, except right along the shore and the
highest elevations of the srn Poconos.

A weakening cold front will try to push down from NY/NE later
Thursday, and this could trigger a shower/tstm across the nrn/wrn
parts of our region. Pops will be in the chc range for this
feature.It`s possible that it could wash out and leave us with a
drier day up north. This will be something to monitor over the
next few days. Temperatures again summer-like in the low and mid
80s.Humidity levels Thu-Thu night will begin to increase and  muggy
conditions will be the result.

Our area will remain just near enough to the storm track over the
weekend to keep conditions rather unsettled. We will continue with
slgt chc/small chc pops for mostly the nrn/wrn areas. Conditions
will be summer-like with shower activity not lasting long, but in
tstms they could yield some decent qpf.


&&

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

Today...MVFR/IFR (localized LIFR) visibility due to fog early for
some terminals, otherwise VFR. Showers are expected to develop
mainly from about midday on, with the greatest chance from KTTN-
KPNE/KPHL-KILG on westward. A few thunderstorms are anticipated as
well. Given low coverage of thunderstorms, it was not included in
the TAF`s, however a TEMPO group is carried for showers. Light and
variable winds to start, becoming mostly northeast 4-8 knots then
possibly becoming southeast toward evening.

Tonight...Local restrictions due to showers or a thunderstorm in the
evening, however the showers should be diminishing west to east
through the night. Otherwise, mainly VFR. Light southerly winds
overall, and if enough clearing takes place overnight then local fog
should develop.

outlook...
tue...mostly vfr but sct showers with lower cigs/vsbys psbl.
tue night thru wed night...vfr. patchy fog psbl both nights.
thu thru fri...mostly vfr. sct tstms mostly afternoon and early
   evening with restrictions psbl.

&&

.MARINE...
The conditions early this morning are rather marginal for a Small
Craft Advisory, as seas are in the 3-5 foot range on the Atlantic
coastal waters. Low pressure offshore should increase the winds some
today especially across the southern waters and this should build
the seas some through the day. Overall the winds should remain below
25 knots, however will just keep the generic Small Craft Advisory
going (extended to 15z up north to 04z southward). The conditions
are expected to remain below advisory criteria on Delaware Bay.

outlook...
sub sca conditions expected thru the period.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ452>455.
     Small Craft Advisory until 11 AM EDT this morning for ANZ450-
     451.

&&

$$
Synopsis...O`Hara
Near Term...Gorse
Short Term...Gorse
Long Term...O`Hara
Aviation...Gorse/O`Hara
Marine...Gorse/O`Hara



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