Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 281053
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
653 AM EDT Fri Apr 28 2017

.SYNOPSIS...
A cold front will wash out as it moves to our south this
morning. A backdoor cold front will move across the area
Saturday into Saturday night. This front will remain near the
Delmarva and southern New Jersey on Sunday, then return as a
warm front on Sunday night. Another cold front is expected on
Monday night as an area of low pressure moves into the Great
Lakes region. This low will drift northeast through southeast
Canada through Thursday, with a couple of weak surface troughs
moving across the area Tuesday and Wednesday. An area of low
pressure may affect the Mid Atlantic region late next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Cold front is expected to propagate off shore rather quickly
this morning, and with it, any remaining showers should also
move out of the region. Once that happens, expect the rest of
the daytime hours to be dry across the region.

In the mid and upper levels, our region will be on the northern
periphery of a strengthening long wave ridge. In addition,
clouds are forecast to dissipate quickly behind the front,
leading to mostly sunny conditions through the day. Thus,
despite the passage of the cold front this morning, temperatures
today will likely be slightly above yesterday. We are
forecasting highs to be about 15 degrees above normal, ranging
from the lower 70s to lower 80s across the region.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
A few showers and thunderstorms may move in to portions of NJ
and SE PA as a surface trough digs south through the region as
it is filling and weakening. Once again it looks like there
should be some meager elevated instability - enough to support
some thunderstorms across the region.

Lows will likely be near the morning dew point temperatures -
generally in the upper 50s to upper 60s. However, winds are
expected to shift from south southeasterly to southwesterly
after midnight. This subtle wind shift combined with increasing
mid level clouds may be enough to inhibit any fog development
overnight.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
A backdoor cold front will move into the area on Saturday and
sink southward through Saturday night. High temperatures
Saturday could be quite warm, but will be highly dependent on
how fast the front moves through the area. If it waits until the
late afternoon or 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 Saturday through Saturday night, so
there will be a chance for isolated/scattered showers and
thunderstorms. If enough instability builds on Saturday, a few
storms could become strong with gusty winds. But there could be
a strong enough cap to prevent much activity until late in the
day or evening.

The front will likely stall across the Delmarva and southern
New Jersey during the day Sunday. With the front near the area,
this could help create some additional lift to interact with any
short wave/vorticity impulses that move across the area and
create some scattered showers. Sunday`s highs are forecast to be
markedly cooler than Saturday, about 15 degrees cooler for many
areas.

The front will not stay stalled out for 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.
Temperatures Monday will warm once again as we enter into the
warm sector ahead of the approaching cold front and return flow
sets up. There could also be some showers and thunderstorms
developing during the day Monday ahead of the approaching cold
front.

However, the best chance for showers and thunderstorms is for
Monday night as the cold front moves across the area. 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, as an area of
low pressure moves through the Great Lakes region. This low will
drift through southeast Canada through Thursday, with a couple
of weak surface troughs possibly moving across our area Tuesday
and Wednesday. There is a slight chance of showers across
northeast Pennsylvania and northern New Jersey during each day,
but chances are low at this time.

By Thursday into Friday, an area of low pressure is forecast to
move up the east coast and potentially bring a period of steady
rainfall to the area. There is some timing and placement
differences, which is typical this far out, but they do agree on
Thursday into Friday as the likely period.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Shallow ground fog has developed at some of the TAF sites
(specifically KILG, KABE, KTTN, and KPNE). Given how shallow
this fog is, do not expect it to last long, only through 12Z or
shortly thereafter. Once the fog dissipates, VFR conditions are
expected through at least 06Z. There is a chance for showers
and thunderstorms, primarily after 06Z tonight and primarily for
KTTN and KABE. MVFR conditions will be possible with any
showers or thunderstorms. Additionally, some more fog may
develop near 12Z.

Though the cold front hasn`t passed through many of the TAF
sites yet, expect winds to be mostly northwesterly by 12Z or
shortly thereafter. Wind speeds at the surface are generally
expected to be light through the TAF period. Earlier low level
wind shear has dissipated.

OUTLOOK...
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. Lower
conditions possible during the day with any showers or storms,
more likely lower conditions overnight. Gusty southwest winds
around 25 knots.

Monday night...MVFR CIGS possibly developing. Showers and
thunderstorms likely overnight Monday could briefly lead to IFR
conditions.

Tuesday...VFR conditions. Gusty southwest-west winds 25-30
knots.

&&

.MARINE...
Seas are slowly starting to drop near 5 feet. Once seas drop
further this morning, Winds and seas are expected to remain
below SCA criteria through the remainder of today and tonight.

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

&&

.CLIMATE...
**Record or number 2 warmest April on record expected**

Presuming our forecast temps these last 4 days of April are
accurate, we are assured of a top 2 warmest April on record in
much of our forecast area. Sunday is probably the critical day
for determining record or not.

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

This includes todays high and low temperatures through 4 PM.


PHL normal 54.0 POR 1874

59.4 1994
59.4 2017?  projected tied warmest ever
58.5 1921
58.4 2010
57.9 1941

ABE normal 49.9 POR 1922

56.8 projecting record
56.4 1941
54.7 1994

ACY normal 51.7 POR 1874

57.2 projecting record
56.3 2010
56.1 2011

&&

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

&&

$$
Synopsis...Robertson
Near Term...Johnson
Short Term...Johnson
Long Term...Robertson
Aviation...Johnson/Robertson
Marine...Johnson/Robertson
Climate...



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