Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 200119

Area Forecast Discussion
National Weather Service Mount Holly NJ
919 PM EDT Thu Apr 19 2018

Low pressure will move further offshore and into the Canadian
Maritimes tonight. High pressure will build in from the west through
Friday 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.


Low pressure will continue to move into the Canadian Maritimes
tonight, while high pressure moves into the Great Lakes region. This
will keep our are under a tight pressure gradient and steady
northwest flow overnight.

A steady NW cyclonic flow continues around the departing upper
low. Clouds are breaking up across SE PA and parts of NJ this
evening. The clouds will hang on the longest N/W where some
showers (rain or snow) will continue into the early overnight.
Few changes were made to the pop/weather grids, since things
appear to be working out fairly well. Some minor adjustments to
temperatures and winds were made however.

Temperatures fall well below normal again tonight. Portions of
eastern Pennsylvania and northeastern Maryland where the growing
season has started have the potential for overnight/Friday morning
lows to fall to freezing or lower. Therefore we have issued a Freeze
Warning for these areas. Elsewhere across other portions where the
growing season has started, we do not expect temperatures to fall to
freezing or lower at this time except a few isolated spots; such as
some sheltered areas in the Pine Barrens. Farther north across
northeast Pennsylvania and northern New Jersey, temperatures are
expected to fall to freezing or lower, but their growing season was
pushed back a couple of more days.

We do not expect much frost to develop overnight, although temperatures
will likely be low enough that it would form on other days. However,
we expect there to remain a breeze overnight around 5- 10 mph and
it may be too dry for frost to form. So no Frost Advisory was issued
at this time.

We are expecting a steady NW winds overnight with some gustiness
at times, perhaps up to 20 mph.


Low pressure will continue to linger near the Canadian Maritimes on
Friday, while high pressure over the Great Lakes tries to build
eastward. The high will not make it into the area through the
daytime hours, so this will keep a steady northwest flow across the
area through the day. While there could be some cloud cover develop
during the day Friday, we do not expect any precipitation as there
will be dry air in place as evident from PW values near a quarter to
a third of an inch. Winds will continue to be gusty out of the
northwest with gusts 20 to 25 mph, with occasional gusts up to 30
mph at times possible.


Friday night through Monday...High pressure will be building into
the region Friday night and overspreading the area through the
weekend. The high remains across the region through Sunday before
sliding offshore Monday afternoon/evening.

Friday night will be the start of a nice weekend across the region.
Skies will clear and winds will become light which will promote good
radiational cooling. Temperatures are expected to drop down into the
30s across much of the region, falling below freezing across the
Lehigh Valley, southern Poconos, and northwest New Jersey. Some near
freezing temperatures will be possible in parts of Berks, Chester,
upper Montgomery, and upper Bucks counties, as well as parts of
north central New Jersey.

With the high in control, we should see some nice weather across the
region, lasting through the weekend. Dry and warming conditions are
expected. Winds will be fairly light through this period and we
should see plenty of sunshine. Highs on Saturday will be in the
upper 40s across the higher elevations of the southern Poconos and
northwest New Jersey and into the mid to upper 50s across the rest
of the region. Areas along the coast will remain slightly cooler and
in the low to mid 50s. Sunday will be fairly similar to Saturday but
the air mass will modify a bit and we should maximum temperatures a
few degrees warmer than on Saturday.

Tuesday through Thursday...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 models agree
that there is some form of a coastal low develops and impacts our
area, there are marked timing and phasing differences that lead to a
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.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...VFR most areas, few lower CIGS/VSBYS in snow showers
near KMPO. Clouds diminishing over most areas overnight. NW
winds with gusts could remain through the night for many
locations, although the speeds will diminish some.

Friday...VFR conditions are expected on Friday, with scattered
clouds possibly developing around 4,000-5,000 feet during the day.
Winds will remain gusty out of the northwest, with gusts reaching 20-
25 knots.


Friday night...VFR conditions expected. Northwest winds around 5 to
20 knots...gradually decreasing overnight. High confidence.

Saturday...VFR conditions expected. Northwest winds around 10 knots.
High confidence.

Sunday...VFR conditions expected. Light winds. High confidence.

Monday...VFR conditions expected. Light winds becoming northeast to
east around 5 to 10 knots...becoming southeast by Monday
afternoon/evening. Moderate confidence.

Tuesday...Mainly VFR conditions expected. East to southeast winds
around 10 to 15 knots. Increasing cloudiness through the day.
Moderate confidence.


Gale Warning remains in effect for the Delaware Bay and the southern
New Jersey and Delaware Atlantic coastal waters for the overnight
hours. Wind guts around 35 knots are occurring this evening and
will remain into the overnight. A Small Craft Advisory remain
in effect for the northern and central New Jersey coastal
waters. Once the Gale Warning ends Friday morning, it will
likely need to be replaced with a Small Craft Advisory. Winds
will likely diminish during the afternoon hours Friday, so the
expiration time was left at noon.


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

Tuesday...Seas will increase through Tuesday in advance of an
approaching coastal low pressure system. Winds will increase later
Tuesday. A Small Craft Advisory will likely be needed towards
Tuesday afternoon/evening.


Minimum RH values on Friday are forecast to be in the low 30s, with
most places 35-40 percent. With the rainfall and clouds today, fuels
likely did not dry out much. Even though it will be quite windy
Friday, with the relatively moderate RH values and non critical
fuels expected, we do not anticipate enhanced fire weather
concerns Friday. If the RH values drop, we may coordinate with
our state partners to discuss the need for any enhanced


PA...Freeze Warning from 2 AM to 8 AM EDT Friday for PAZ060-101>103.
MD...Freeze Warning from 2 AM to 8 AM EDT Friday for MDZ008.
MARINE...Small Craft Advisory until noon EDT Friday for ANZ450>452.
     Gale Warning until 8 AM EDT Friday for ANZ430-431-453>455.


Near Term...Robertson/PO
Short Term...Robertson
Long Term...Meola
Fire Weather...Robertson is the U.S. government's official web portal to all federal, state and local government web resources and services.