FXUS61 KPHI 211455

Area Forecast Discussion
National Weather Service Mount Holly NJ
955 AM EST Wed Feb 21 2018

Unseasonable Bermuda High pressure off the East Coast will
provide one more day of record-breaking warmth over the mid-
Atlantic region. A cold front will push south across the area
tonight and then stall to our south. Several waves of low
pressure will move northeast along this roughly stationary
frontal zone, resulting in periods of rain from Thursday through
Sunday. Another cold front will cross the area late on Sunday
followed by high pressure building in for the first part of next


Deep layer southwest flow continues to transport an anomalously
warm and increasingly moist air mass into the region. Both low
clouds and fog were dissipating as of 9 AM, particularly over
portions of eastern PA and Delmarva, as the diurnal boundary
layer becomes established. Mixing up to around 950 hPa and
increasing sunshine will yield high temperatures into the 70s
outside the southern Poconos, generally 20-25 degrees above
seasonal norms! A list of records is available in the climate
section at the end of this product. With Dew Points rising into
the 60s along the coastal plain, the humidity will be palpable.
Based on the latest guidance and trends, showers associated with
a cold front time into the southern Poconos and Lehigh Valley
in the 3-5PM time frame, so we have maintained chance PoPs here.
While we cannot rule out a rumble of thunder, the greatest
chance is just west of our area, in agreement with SPC.


The cold front will make its way into and across our area this
evening and into the overnight hours. As it does so, a line of
showers will be making their way across our area as some
enhanced moisture and lift associated with the front move across
the area. The front will continue to sink south of the area
through the overnight, and the showers associated with the front
itself will slide southward as well. However, there will
continue to be a chance of rain later in the night as an
approaching short wave brings additional enhanced moisture and
lift to the area. One concern will be how cold the temperatures
for the northern areas across the Poconos and northwest New
Jersey can get. If they drop below freezing overnight, some
freezing rain may develop. Everywhere else, temperatures will be
well above freezing.


A somewhat unsettled weather pattern will remain in place for
the first few days of the extended period, Thursday through
Saturday. Southwest flow aloft will carry moisture over the
area as several weak disturbances move quickly along the
residual frontal zone. It is difficult to say if any period will
be rain free, but a general rain looks more likely during the
days on Thursday and Friday and again Saturday night.

Colder air will continue to filter in behind the cold front on
Thursday, with high temps 25 to 30 deg colder than today. With
rain overspreading the area, temps may be cold enough for
freezing rain in far northwest NJ and adjacent PA Poconos,
especially late in the day and into the night. There is forecast
to be a persistent layer of above freezing air aloft so no snow
is expected. Surface flow is forecast to become more southerly
on Friday with rising temps and precip should become all rain by
about midday.

Saturday and Sunday should feature somewhat above normal temps
but continued periods of rain with a frontal boundary still in
the mid-Atlantic area. A pronounced upper trof and associated
deepening surface low are forest to lift northeast from the
southern Rockies to the Great Lakes during this period. The
attendant cold front should move through our area Sunday
afternoon, preceded by widespread rain or showers.

For Monday and Tuesday, high pressure is then forecast to build
eastward from the Ohio Valley into the mid-Atlantic, resulting
in fair weather. The airmass behind Sunday's front does not look
especially cold and temperatures look to be near or slightly
above normal.


Today...IFR conditions will persist through the mid morning
hours, then the low clouds and fog will lift and burn off;
similarly to Tuesday morning. Once the low clouds and fog burn
off, VFR conditions will remain for the remainder of the day.
There is a small chance for showers late this afternoon, but
more likely this evening as a cold front moves across the area
tonight. Winds will be mostly south to southwest today, and
could gust 15-25 knots by the late morning into the afternoon
hours after the sun comes out and stronger mixing occurs.

Tonight...VFR conditions are expected this evening and overnight
across the area. There is a chance for showers this evening and
overnight as a cold front moves across the area. Winds will start
out southwest ahead of the front, then once the front moves through,
winds will switch to the north to northwest and could gust 15-20


Thursday...Sub-VFR conditions possible in rain. NE winds 10-15
kt. Confidence: Average.

Thursday night...Sub-VFR conditions possible in scattered
showers. Mixed frozen precip in rain and sleet possible at
KRDG and KABE late. Confidence: Below average.

Friday through Sunday...Sub-VFR conditions in periods of rain.
Confidence: Average.


Based on trends as of mid-morning and guidance, issued a Small
Craft Advisory for all of Delaware Bay through this evening for
southwest wind gusts up to around 25 knots. Elsewhere across the
Atlantic waters of NJ and DE, conditions are expected to remain
below advisory levels through today and tonight, with southwest
winds gusting to around 20 knots and seas 3-4 feet. Winds will
veer to the north to northwest tonight as a cold front moves
across the waters.

The Dense Fog Advisory for all the waters will be allowed to
expire at 15Z, as visibilities are expected to be predominantly
over 1 NM by that time. Further localized restrictions are
possible, especially across the Atlantic Waters of Southern NJ
and Delaware. A Marine Weather Statement will be issued for the
Atlantic waters of NJ and DE to highlight patchy fog, with 1-3
NM visibilities though this evening, as well as cold sea-surface
temperatures given anomalously warm air temperatures and boating


Wednesday night...Sub-SCA conditions expected. SW winds turning NW

Thursday through Friday...SCA conditions possible on the ocean

Saturday...Sub-SCA conditions anticipated.

Sunday...SCA conditions possible.


More high temperature records are likely today. Here are the
records for Wednesday, February 21:

Atlantic City...74 in 1930
Philadelphia....72 in 1930
Wilmington......70 in 1953
Allentown.......67 in 1953
Trenton.........70 in 1930
Georgetown......71 in 2014
Mount Pocono....60 in 1930
Reading.........71 in 1930

The following are the record warm minimum temperatures for
Wednesday, all which should be exceeded.

ABE 46-1981
ACY 49-1954
PHL 49-2002
ILG 47-2002
RDG 48-1930
TTN 48-2002

The all time February max temps may be approached on Wednesday
at ILG, TTN, GED RDG MPO. All the all time monthly max's are
listed below:

ACY 77 2/25/30
PHL 79 2/25/30
ILG 78 2/24/85
ABE 77 2/24/17
TTN 76 2/25/30
GED 77 2/25/17
RDG 77 2/24/17
MPO 70 2/25/30

Our expectation is that ACY will exceed the previous all time
record rainfall for February, by the end of the weekend. The
record is 6.50 inches in 2010. #2 is 1958 with 5.98 inches.

And...adding only half an inch to PHL and ILG will put both
locations in the top 9 ranking for Feb rainfall.

Have rechecked the monthly projection at PHL and the avg temp
continues at 41.0 or 5.3F above avg which is 8th warmest on
record, if it holds. Add or subtract a degree to the
average/departure and the ranking changes from 3rd to 11th. The
forecast 5.3F departure is ~2f warmer than the current
departure. I'd expect similar for the rest of our area...a bit
less in the north which will have better chances for colder air,
and a bit more warming in the south where the positive
departure as of yesterday was already 5F above normal, heading
for 7+. So all in all it appears we're heading for a top 10
warmest February. Last year was the warmest on record, a
whopping 3+F degrees warmer than our current projection.


MARINE...Dense Fog Advisory until 10 AM EST this morning for ANZ430-431-
Small Craft Advisory until 6 PM EST this evening for ANZ430-


Near Term...Franck/Robertson
Short Term...Robertson
Long Term...AMC
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