Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 271641

Area Forecast Discussion
National Weather Service Mount Holly NJ
Issued by National Weather Service BALTIMORE MD/WASHINGTON DC
1241 PM EDT Thu Apr 27 2017

A cold front will move across the area tonight into Friday
morning. A backdoor cold front will move across the area
Saturday into Saturday night. This front will remain to our
south on Sunday, then return as a warm front on Sunday night.
Another cold front is expected on Monday night, with a secondary
front or surface trough Tuesday. Another cold front is possible


Clearing of the low clouds continues slowly from southwest to
northeast, with the exception of low marine stratus along the
immediate southern NJ coastline. Forecast for today remains on

Previous discussion from 950am:
Low continues to spin away from the region this morning, with
mid/upper level ridging moving overhead ahead of the next system
ejecting through the Great Lakes that will affect the region
tonight. Lingering low level moisture and low level
southeasterly flow has led to the continuation of low clouds
from the Philadelphia metro area northeastward and along the
shorelines. There is also still some lingering fog in the
Poconos this morning. Gradual improvement is expected through
the morning hours and into the afternoon, especially across SE
PA, central and southern NJ, and DE, with mostly sunny skies
already being observed SW of the Philly metro as of 930 am. NE
PA and Northern NJ will be the toughest to get sunshine. Highs
today in the 70s for most locations, within a few degrees
plus/minus of 80F for Philly SW-ward, and stuck in the 60s along
the immediate shoreline with continued SE flow.


The main story tonight will be the cold front expected to move
through the region. With the center of the associated surface
low (in Central Canada) slowly propagating north, the front is
not expected to progress east very quickly. Expect that most
precipitation ahead of and with the front will be showers.
However, model soundings do show elevated instability, thus have
kept mention of thunderstorms overnight.

Given persistent cloud cover overnight, and a late arrival of
the cold front, do not expect temperatures to drop off much
overnight, with lows generally in the upper 50s and lower 60s.


The cold front that affects the area Thursday moves offshore
Friday morning and any showers will dissipate and/or move
offshore through the morning as well. The remainder of Friday
will remain dry as weak high pressure briefly affects the area.

By Friday night, another frontal boundary is forecast to begin
approaching the area from the north as it crosses Pennsylvania
and New York. The front is not expected to move into the area
until later Saturday, then sink to our south Saturday night.
Saturday`s high temperatures will be highly dependent on how
fast the front moves through the area. If it waits until the
late afternoon/evening, temperatures will be able to warm quite
significantly. However, if the front moves through quicker, high
temperatures may not be as high as currently forecast. This
would be more likely across portions of northeast Pennsylvania
and northern New Jersey where the front may cross sooner. A
couple of short wave/vorticity impulses are forecast to move
across the area Friday night through Saturday night, so there
will be a chance for isolated/scattered showers.

The front will stall to our south during the day Sunday, which
should allow Sunday to be mostly dry, but an isolated shower can
not be ruled out. Being the front is a back-door front coming
from the north, it will bring cooler conditions on Sunday.
Sunday`s highs are forecast to be markedly cooler than Saturday.
15 degrees cooler for many areas.

The front will not stay to our south very long as it is
expected to lift back northward as a warm front Sunday
night/Monday morning. As the front lifts across the area, there
will be a chance of showers Sunday night into Monday morning.
There could also be some showers and thunderstorms developing
during the day Monday ahead of an approaching cold front.

However, the best chance for showers and thunderstorms Monday
night as a cold front approaches from the west. Being we should
enter into the warm sector during the day, we should warm quite
nicely, and in turn some instability should build ahead of the
front. Therefore there will be a chance of thunderstorms Monday
afternoon and Monday night.

The front will move offshore by Tuesday morning, but a
secondary surface trough may move across the area during the day
Tuesday. With a short wave/vorticity moving across the area
during the day, there could be some isolated showers across
northeastern Pennsylvania and northern New Jersey.

Another front may move across the are Wednesday of next week
which could bring another chance of showers. The GFS and
Canadian continue developing an area of low pressure along the
front to our southeast which could move across our area later in
the week. However, the ECMWF no longer has this feature. This
is still pretty far out, but there will be a chance of showers
in the forecast for the end of next week.


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

The Sterling office will be updating TAFS after 1230Z today
since the Mount Holly office will be off line for a computer
upgrade into this afternoon.

Today...Conditions improving early this afternoon with MVFR
conditions giving way to VFR as low clouds erode. Winds mainly
southeast to south and may gust 15-20 kt at times during mid

Tonight...After 03Z, low clouds may move back in over the region.
In addition, showers and isolated thunderstorms may approach
from the west. There is low confidence though on if individual
TAF sites will be affected and the timing. Southerly winds
tonight shift west late after frontal passage.


Friday...VFR conditions expected.

Friday night...VFR early. Patchy fog and low CIGS may develop

Saturday...Becoming VFR during the morning, then a chance of
showers during the afternoon. Conditions may temporarily be
reduced with any showers. Gusty westerly winds 15-20 knots.

Saturday night-Sunday night...Low clouds and fog may develop
overnight Saturday and continue into Sunday night leading to
reduced conditions. Small chance of showers and thunderstorms.
Conditions may temporarily be reduced with any showers.

Monday...Low conditions in the morning, becoming VFR during the
day. A chance of showers thunderstorms during the day, with
more likely showers and thunderstorms overnight. Lower
conditions possible during the day with any showers or storms,
more likely lower conditions overnight. Gusty southwest winds
around 25 knots.


Elevated seas are expected to continue today and tonight on the
Atlantic Coastal waters, generally ranging from 5 to 6 feet. A
few gusts near or above 20 kt are possible this evening.


Friday...Winds expected to remain below advisory levels, but
seas may remain elevated to advisory levels.

Friday night-Sunday night...Seas may approach 5 feet at times,
and winds may gust near 20 knots, but conditions expected to
remain below advisory levels.

Monday...Winds likely to gust 25-30 knots, and seas likely to
exceed 5 feet as well leading to Small Craft Advisory


Though some of the guidance is depicting minor coastal flooding
with the evening high tides today and tomorrow, we are not
expecting any coastal flooding as astronomical tides will start
to decrease, and by tonight, winds will be shifting to off


Presuming our forecast temps these last 5 days of April are
accurate, we are assured of a top 3 warmest April on record in
much of our forecast area. Sunday is the critical day for
determining record or not. (will recheck this projection around
430 PM)

Below: April projected within the top April avg temps, the
normal for April and the period of record (POR).

PHL normal 54.0 POR 1874

59.4 1994
59.2 2017?
58.5 1921
58.4 2010
57.9 1941

ABE normal 49.9 POR 1922

56.6 projecting record
56.4 1941
54.7 1994

ACY normal 51.7 POR 1874

57.2 projecting record
56.3 2010
56.1 2011


MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Friday
     for ANZ450>455.


Near Term...Muccilli
Short Term...Johnson
Long Term...Robertson
Aviation...Muccilli/Drag/Johnson/Robertson 803
Tides/Coastal Flooding...PHI
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