Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS61 KPHI 210249

Area Forecast Discussion
National Weather Service Mount Holly NJ
949 PM EST Tue Feb 20 2018

Bermuda high pressure slowly drifts to the south and east
tonight through Wednesday. A cold front will then approach late
Wednesday and pass through the region Wednesday night, then
becomes nearly stationary over the Mid-Atlantic region. Several
waves of low pressure will pass along this boundary through the
weekend. High pressure returns for the start of the new work


A nice night out there tonight as clouds have cleared and we are
radiating fairly well. Some shallow ground (radiation) fog is
starting to develop in the river valleys and will continue to
develop across the region overnight. Some drizzle may be present
along with the fog. Fog is present on satellite images but
looks to be mainly confined to the immediate coast. As the
winds drop off tonight, fog is expected to advect inland,
dropping visibilities.

Not as confident on how dense fog cover will be tonight and will
hold off on any advisories at this time.

Lows tonight, very mild, with upper 40s across the north and
low/mid 50s elsewhere. Light winds overnight.


Wednesday will likely start much the same way as did Tuesday.
That is, plenty of low clouds, fog and some drizzle across the
region. Slow improvement though the morning and then a return to
partly/mostly sunny skies during the afternoon. An approaching
cold front may trigger a few showers N/W in the afternoon. We
will only have some chc pops for this with the fcst with the
dynamics not looking too strong with it. Temperatures, once
again, in record territory with highs in the low/mid 70s in most
areas with some 60s across the far north. Colder right along
the shore however.


Although the record setting warmth will depart Wednesday night,
there will still be a prolonged period of above normal
temperatures for the Long Term.

Cold front works its way south through the region Wednesday
night and becomes nearly stationary along the Mid-Atlantic by
Thursday morning. The region then becomes situated between cold
high pressure to the north and warm high pressure to the south.
Temperatures should rise and fall with each passing low, but the
areas mainly impacted by the cold should be generally north of
I-78 through the end of the work week. Showers taper off in the
evening, and then return late Wednesday night as weak low
pressure forms over the Gulf Coast states and lifts to the north
and east. Behind the front, temperatures drop into the 30s
north and west of the Fall Line, and lows will be in the 40s
across the Coastal Plain of NJ, southeast PA, and into the
Delmarva. As precipitation develops with the next system,
temperatures should be cold enough in the Poconos and far
northwest NJ to allow for a period of mixed frozen precip,
mainly rain, freezing rain, and sleet, late Wednesday night and
into Thursday morning. For the rest of the region, precip should
mainly stay as rain, as surface temperatures should stay above

By Thursday afternoon, precip should be all rain throughout,
and then tapers off by Thursday evening.

The next low develops Thursday night and approaches on Friday.
A good period of mixed frozen precip looks to develop across
northern areas north and west of the Fall Line Thursday night
and eventually changes to plain rain by Friday afternoon.

Upper trough then approaches for the west this weekend, and
stronger low pressure will impact the region with more
widespread rain through Sunday.

Conditions dry out on Monday as high pressure builds in from
the west.

Temperatures will generally be above normal levels during this
time, but it looks as if it will be quite warm, though wet, over
the weekend.


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

Tonight...Another challenging fcst with regards to what time
the lower conditions will arrive. Guidance has slowed the onset
of IFR/LIFR conditions and we have pushed the timing back for a
few hours overnight. Conditions will deteriorate, especially
after 06Z at the terminals. Drizzle and fog will develop again
overnight. Winds will be light mostly SW or S.

Wednesday...IFR/LIFR with fog and drizzle during the morning...
then improvement in the 14Z thru 18Z time frame. Low confid on
the timing of improvement.

Confidence: Average.


Wednesday night...Scattered showers and patchy fog possible
with sub-VFR conditions. Winds shift from SW to N. Confidence:

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/KABE/KTTN/KPNE late. Confidence: Below average.

Friday through Saturday...Sub-VFR conditions in periods of
rain. Confidence: Below average.


The main hazard tonight and into Wednesday morning will
continue to be fog. A Marine Dense Fog Advisory remains in
effect into Wednesday. Winds tonight and Wednesday will be
south to southwest at 5 to 10 knots for the most part. Water
temperatures 40 to 45 degrees. Winds and seas are expected to
stay below small craft advisory criteria tonight and tomorrow.


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.


The following high temperature records were set today:

Atlantic City...73
Mount Pocono...66

A record warm minimum temperature may be set for Atlantic City
today. The current record is 44 in 1949. We will have to wait
and see how low the temperature gets through the evening hours.
The low so far today has been 52 degrees.

Additional high temperature records are likely on Wednesday.
Here are the records for February 21.

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 Wednesday for ANZ430-431-


Near Term...Meola/O`Hara
Short Term...O`Hara
Long Term...MPS
Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.