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000
FXUS61 KPHI 200725
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
325 AM EDT Fri Apr 20 2018

.SYNOPSIS...
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High pressure will build in from the west today and remain in the
area through the weekend before sliding offshore on Monday. Low
pressure developing over the southeastern United States will move up
the Mid Atlantic coast, affecting our area through the mid week
period.
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.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A Freeze Warning continues until 8:00 AM for the Pennsylvania
counties of Berks, upper Montgomery and Chester, and for Cecil
County in Maryland.

Low pressure was located off Nova Scotia early this morning. The low
will continue to move northeast toward Newfoundland. Meanwhile, high
pressure centered in the upper Mississippi River Valley will build
eastward. The circulation between the two systems will maintain a
northwest wind in our region for today. Sustained wind speeds of 10
to 15 mph are expected with gusts of 20 to 25 mph.

The stratocumulus that was lingering over parts of our region early
this morning should continue to erode. However, a fair amount of
cumulus is anticipated to develop during the late morning and early
afternoon due to the interaction between the strong April sunshine
and the chilly air aloft.

Highs are forecast to be in the lower and middle 50s in much of our
region, with readings not getting above the 40s in the Poconos and
in far northern New Jersey. The expected temperatures are about 12
to 16 degrees below normal for April 20.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
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The center of the surface high is forecast to slide into the eastern
Great Lakes Region and the upper Ohio River Valley tonight. We are
anticipating a mostly clear sky with perhaps an increase in cirrus
late tonight. The northwest wind is expected to diminish to less
than 10 mph.

We continue to issue frost and freeze products only for locations
from the counties of Berks, Montgomery, lower Bucks, Mercer and
Middlesex southward. We will begin frost and freeze products for
much of the remainder of our forecast area next week. Based on the
anticipated low temperatures for tonight (mostly in the 30s) and the
decreasing wind, we may need to put some areas under a Frost
Advisory. Another Freeze Warning is possible for the same locations
as the current one. We will look at the next full suite of guidance
before making a final decision during the day.
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.LONG TERM /SATURDAY THROUGH THURSDAY/...

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Saturday Through Monday...

Surface high pressure will build over the region through this period
along with an associated upper level ridge. This will bring fair
weather with sunshine and gradually warming temperatures.
Forecast models are in excellent agreement with this scenario
so a high confidence forecast for this period.

In terms of the day to day specifics, each day will feature plenty
of sunshine but there will still be a bit a NW breeze Saturday near
10 mph with highs generally in the upper 50s to low 60s (except
cooler in the southern Poconos). This is still a little cool for
this time of year. However winds will be lighter for Sunday and
Monday with temperatures warming a couple degrees each day so by
Monday, highs will be well into the 60s for much of the region. Lows
each day will be chilly due to the clear skies and light
winds...generally in the 30s with western and northern zones in the
CWA likely dipping to near or below freezing.

Tuesday through Thursday...

Overall, no major changes to this part of the forecast as general
thinking remains the same. A low pressure system will move across
the Mississippi Valley and into the southeastern United States early
next week. As the low pushes towards the coast, it starts to move
northward towards the Mid-Atlantic states. While the forecast models
agree that there is some form of a coastal low that develops and
impacts our area, there are still differences regarding timing and
evolution that lead to a relatively low confidence forecast at this
time. The system will bear watching as it will have good moisture
associated with it and the potential for some heavy rain will exist.
Strong onshore flow could also bring some coastal flooding concerns
and will also need to be monitored. Still a long way out and plenty
of time to see how the models come together on this system over the
coming week.
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.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Today...VFR with mainly scattered stratocumulus and cumulus clouds.
Northwest wind 10 to 15 knots with gusts of 20 to 25 knots.

Tonight...VFR with a mostly clear sky. Northwest wind diminishing to
less than 10 knots.

OUTLOOK...

Saturday...VFR conditions with northwest winds around 10 knots. High
confidence.

Sunday...VFR conditions with light winds. High confidence.

Monday...VFR conditions expected along with continuing light winds.
Moderate confidence.

Tuesday...Mainly VFR conditions expected. East to southeast winds
around 10 to 15 knots. Increasing cloudiness through the day.
Moderate confidence.
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.MARINE...
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The potential for gale force gusts on our southern ocean waters and
on Delaware Bay continues to diminish. As a result, we will
downgrade the Gale Warning for those locations to a Small Craft
Advisory. The Small Craft Advisory will remain in place for our
northern ocean waters.

Based on the latest guidance, we will run the Small Craft Advisory
for our entire marine area until 2:00 this afternoon.

The northwest wind is forecast to decrease gradually from late this
afternoon into tonight.

OUTLOOK...

Friday night through Monday....Sub-advisory conditions are expected
on the the area waters.

Tuesday...Winds and seas increase in advance of an approaching
coastal low with SCA conditions likely be late day.
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.FIRE WEATHER...
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We are expecting a northwest wind of 10 to 15 mph with gusts of 20
to 25 mph for today. Relative humidity values are forecast to drop
around 30 percent in much of northeastern Maryland, Delaware, New
Jersey and southeastern Pennsylvania. We are planning to coordinate
with our fire weather partners this morning regarding fuel moisture
levels to determine if any additional fire weather products need to
be issued for today.
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.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Freeze Warning until 8 AM EDT this morning for PAZ060-101>103.
NJ...None.
DE...None.
MD...Freeze Warning until 8 AM EDT this morning for MDZ008.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ430-
     431-450>455.
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$$
Synopsis...Fitzsimmons
Near Term...Iovino
Short Term...Iovino
Long Term...Fitzsimmons
Aviation...Fitzsimmons/Iovino
Marine...Fitzsimmons/Iovino
Fire Weather...Iovino