Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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229
FXUS61 KPHI 231346
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
946 AM EDT THU JUN 23 2016

.SYNOPSIS...
Low pressure in western Pennsylvania will move southeastward and
off the Atlantic coast later today. High pressure will then build
in from the north for Friday into early next week. A slow moving
cold front is forecast to approach from the northwest on Tuesday
and move through the region on Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Adjustments to sky/pops grids with the round of showers/isolated
thunder passing across the Delmarva and srn NJ. More sct activity
across central NJ ern PA will be covered with chc pops for the
next few hours.

There remain some degree of uncertainty in the forecast which revolves
around how much will the atmosphere be able to rebound/destabilize
this afternoon in wake of this morning`s clouds/MCS. Based on the
latest guidance, there will likely be scattered convection
developing during peak heating across eastern PA and
central/northwest NJ along the residual outflow boundary and/or
differential heating boundary to the north of where MCS tracked
earlier. Majority of the model forecast soundings show the
atmosphere capped, which would hinder convective updrafts and our
thunderstorm potential. Still kept a slight chance of thunder in
the weather grids for the mid to late afternoon.

High temperatures should generally in the in the upper 70s and lower
80s. The warmest conditions are expected across the northern half of
the CWA as well as the lower Delmarva, where the greatest potential
to see extended breaks in the clouds reside.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
Some of the hires convective-allowing model guidance advertises a
second MCS developing along or just south of the Ohio River. If it
develops, it should track mainly to our southwest tonight given
the distant position of the frontal boundary to our south and with
weak high pressure building in from the north. Kept low chance
PoPs in the forecast for our Delmarva/Delaware Bay zones tonight
to account for the possibility of the northern periphery that
these showers and storms clip us. There is still a limited risk
that a storm or two becomes strong to severe this evening mainly
across the Delmarva. The threat would transition from winds to
hail late in the evening as convection becomes increasingly
elevated.

Patchy fog may also develop late this evening and especially
overnight. There greatest potential will reside across the southern
portion of the area, where the ground remains wet after today`s
precip. However, convective debris clouds may linger across the
lower Delmarva, which should inhibit the formation of radiational fog.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
High pressure will be the dominant wx feature for the extendd
period. The high will build down from Canada on Fri and influence
our wx into early next week. THe current fcst is for dry and
pleasant wx durg this time.

There is one potential fly in the ointment though. A mid level
trof is fcst to knock back the ridge a bit on Fri. The majority of
the guid keeps any precip assocd with this trof to our w and s.
However, the ecmwf is more robust and brings precip acrs our area
and then develops a sfc low which moves out to sea on Sat. For
now, will maintain a dry fcst, since the ecmwf is the outlier and
go with the majority of the mdls and wpc.

By Mon, an area of low pres will be movg acrs ern Canada. Its
assocd cdfnt will approach from the w late Mon and cross the area
on Tue, with a secondary fropa Tue night into erly Wed. Both cfp
will bring the chc of shwrs/tstms. High pressure will then build in
for the remainder of Wed.

Temps look to be near seasonal values with comfortable dew points.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

By-in-large VFR conditions even in the remnants showers which are
passing thru KMIV/KACY. KMIV was at 5SM in the most recent ob.
Clouds upstream are thinning. Daytime CU will develop this
afternoon. These may further develop into CIGS later. Winds will
be mostly light and somewhat variable today.

More scattered showers could develop after 18Z before ending
around 02Z. Added a 2-3 hour prob30 group for most of the
terminals for late in the day. While an isolated thunderstorm is
not out of the question this afternoon, confidence too low to
include in TAFs.

Patchy fog could develop late this evening and overnight.

Winds will be light (under 10 kt) and variable thru the period.

OUTLOOK...

Friday through Monday...VFR under high pres. Mdt confidence
Friday. High COnfidence for the rest of the period.

&&

.MARINE...
Winds and seas below SCA today and tonight. A sly swell around 2-4
ft will continue in our coastal Atlantic waters thru the period.

One potential impact on our southern waters could be locally gusty
winds in thunderstorms his evening. Coverage of storms will be
low.

OUTLOOK...
Friday through Monday...No marine headlines are anticipated.

&&

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

&&

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



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