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000
FXUS61 KPHI 210127
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
927 PM EDT Mon May 20 2019

.SYNOPSIS...
A cold front moves across the waters tonight, and then high
pressure will bring dry and pleasant weather Tuesday and
Wednesday. A warm frontal passage is likely Wednesday night,
followed by a cold front Thursday night. High pressure will again
be nearby Friday and into Saturday. By the weekend, another
frontal system will be approaching. A cold front will likely cross
the region late Saturday and potentially stall to our south on
Sunday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A cluster of thunderstorms fired up over southern New Jersey out
ahead of the approaching cold front, but have moved offshore.
There may be a few lingering showers, and perhaps a
thunderstorm, over Delmarva and along the New Jersey coast, but
any lingering activity will taper off in the next hour or so.

Cold front will be through the region by midnight or so, and
cooler and dryer air will filter into the region through
daybreak Tuesday. Lows tonight generally in the 40s up north,
and otherwise in the 50s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
An upper-level trough across the Northeast will keep some
cyclonic flow in place, while a ridge begins to build into the
central Great Lakes. Surface high pressure centered near the
central Great Lakes will build or extend toward our area through
the day Tuesday. The combination of some cold air advection, a
pressure gradient present and deeper mixing will result in a
breezy day. The airmass looks rather dry, therefore while plenty
of sunshine is expected there may be some boundary layer
heating driven stratocumulus.

High temperatures are a MOS/continuity blend, however some of
the model guidance 2-meter temperatures are a few degrees
colder. Given the stronger offshore flow, a sea breeze is not
expected and therefore not much difference in temperatures from
the coast to just inland.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Overview...

A rather stagnant big picture pattern remains in place for the
duration of this week and into the holiday weekend. It is the
familiar beat of "trough in the West, ridge in the Southeast", and
the mid-Atlantic sitting near the edge of the ridge. This pattern
will continue to favor periodic storm systems lifting out of the
Plains and Midwest, with occasional shower and storm chances in our
area as these lows lift off to the northeast. Timing the
disturbances is tricky given the vast amount of upstream convection
which tends to play havoc with the guidance. Tuesday night through
Wednesday look to be reliably dry with high pressure in control.
Thursday evening stands out as a more likely opportunity for showers
and storms, with probably another chance towards Saturday. The
Thursday system should be watched, as the environment late in the
day Thursday looks rather conducive to severe weather. Shower and
storm chances for the weekend currently look more garden variety as
the next low center likely passes further away from us, reducing
forcing.

The other issue will be our temperatures. The expansive Southeast
ridge will favor intense, sustained summer heat to our south, but it
is less clear cut as to how firm a grasp the warmth will have over
us. With multiple frontal passages and a frequently varying wind
direction, there are likely to be some ups and downs and some local
variations, such as on Saturday when onshore flow will likely keep
the coast cooler. Overall, however, we are likely to be above normal
for temperatures most of this period.

Dailies...

Tuesday night-Wednesday... This portion of the forecast is
straightforward, as high pressure moves across the area and ensures
dry and seasonable weather.

Wednesday night-Thursday night... A warm front should move through
Wednesday night, setting up what could be a rather active 24 hours
of weather. High uncertainty as to how it all plays out, as there
will be precipitation risks with both the Wednesday night warm front
and the cold front that will approach by Thursday night. For
Wednesday night into Thursday morning, looks like scattered showers
with possibly some elevated thunderstorms. We should dry out
Thursday afternoon, with temperatures getting into the 70s to near
80. Rain chances then go up again for the evening and overnight. Low
pressure, with a trailing cold front, will track eastward through
the Great Lakes then turn southeasterly as it rides along the top of
the ridge. Concern is that if enough instability is present, we
could have strong to severe storms given wind fields really
intensify as the low pressure makes its turn to southeasterly.
An evening or overnight MCS event appears possible. Given it`s
still a few days away, will hold off on more detail for now.

Friday... Most indications are that this should be a dry day in
between systems as we are on the periphery of high pressure.
Temperatures near to above normal, except cooler at the coast with
an onshore component developing in the wind.

Saturday... The daytime period on Saturday looks dry, as retreating
high pressure should still lend us protection for most of the day. A
cold front will be approaching from the west by late day and evening
as another low moving out of the Plains tracks up into Ontario. This
may bring a shower and storm risk towards the evening, especially to
the west. Not overly concerned about strong storms here, as flow
will be onshore Saturday, keeping things stable. This will also keep
temperatures Saturday a little cooler than the upper air charts
would suggest, especially at the coast, though it should be plenty
comfortable with 70s and low 80s. The shower risk will likely
increase into the overnight.

Sunday-Monday... Saturday`s "cold front" will in fact act to warm
temperatures on Sunday by kicking out the onshore flow and turning
winds westerly. This westerly wind should also keep the dew points
in check, especially if the wind ends up a little north of west.
Because of this, Sunday could be quite warm, with strong sensible
heating likely in the post-frontal air mass. Widespread 80s look
likely with 90s potentially in play as well, though did not go that
extreme yet. A caveat, however, is that if the front stalls near or
just south of us, a more humid day with afternoon showers and storms
would be possible. Went on the drier side for now. Very low
confidence by next Monday as another cold front may approach. Could
be another warm day if the front is slow enough, but just leaned
towards a consensus blend for now.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. Any showers and thunderstorms ending early.
West-southwest winds 8-12 knots, becoming northwest.

Tuesday...VFR. Northwest winds 12-15 knots with gusts to 20-25
knots.

Outlook...

Tuesday night-Wednesday night... Mainly VFR. Light north to
northwest wind becoming light and variable Wednesday night. Some
showers and locally MVFR conditions possible Wednesday night.

Thursday-Thursday night... Most of the daytime Thursday should be
VFR with a light southwest wind. Showers and thunderstorms possible
Thursday evening and night with winds gradually shifting to
northwest.

Friday-Saturday... VFR expected. Northerly wind initially on Friday
will become northeasterly during the afternoon, easterly to
southeasterly Friday night, and southerly by Saturday.

&&

.MARINE...
South to southwest flow will continue this evening, however, a
wind shift to the west and northwest occurs tonight as a cold
front moves through. Northwesterly flow continues Tuesday with
some gusts to about 20 knots and seas on the ocean will be up to
4 feet. Therefore, the conditions are anticipated to remain
below Small Craft Advisory criteria through Tuesday. Some
showers and thunderstorms move through early this evening, some
of which could produce locally gusty winds.

Outlook...

Tuesday night-Friday... Winds and seas are expected to remain below
SCA criteria.

Rip Currents...

A northwest wind with no sea breeze expected should result in a
low risk.

&&

.EQUIPMENT...
The KDIX radar is back online. However, it will be in a test phase
through early Tuesday afternoon. Intermittent outages are
possible.

&&

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

&&

$$
Synopsis...O`Brien
Near Term...Gorse/MPS
Short Term...Gorse
Long Term...O`Brien
Aviation...Gorse/MPS/O`Brien
Marine...Gorse/MPS/O`Brien
Equipment...