Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 200920

Area Forecast Discussion
National Weather Service Mount Holly NJ
420 AM EST Tue Feb 20 2018

High pressure off the East Coast will provide southwesterly
winds and unseasonably mild weather today and Wednesday. A cold
front is forecast to cross the area Wednesday night. This
frontal system is expected to remain across the mid- Atlantic
region through the latter part of this week and into the
weekend, with a chance for rain each day. Temperatures should
remain near or somewhat above normal through this period.


A stationary/warm front extended from central New Jersey,
southward across the Delmarva, and southward across the east
coast, before looping back across the western Appalachians and
northward across western Pennsylvania. Areas south and east of
the front remain mostly fog free, while the areas north and west
of the front are socked in with low clouds and dense fog. This
front may push back eastward through daybreak, allowing for the
fog to spread toward the coast. So we will keep the Dense Fog
Advisory in place. We expect the front to lift north of the area
as a warm front during the daytime today. Once the front lifts
north of the area, we expect some clearing, and the fog and low
clouds to dissipate. However, this will likely be a slow trend
for many areas. This will make the forecast for the day tricky.
If the low clouds and fog do not burn off quick enough, daytime
temperatures will not have enough time to warm up. The current
expectation is that the clouds and fog will begin to dissipate
and lift by late morning or early afternoon, which will allow
for some warming. So we leaned closer to the warmer guidance
since we expect some clearing. Outside of some drizzle this
morning, we expect the area to remain preciptation free for
today as there are not any short waves/vorticity impulses


Any clearing this afternoon is expected to be short lived as
clouds and fog/drizzle are expected to develop again tonight.
While the warm front is expected to have lifted north of the
area during the day today, our area will remain withing a
warm/moist southwest flow as high pressure remains off the east
coast. This warm/moist air will allow the low levels to saturate
again, and in turn allowing for the low clouds and fog/drizzle
to form. It is very possible that another night of dense fog is
in store for the area, and another Dense Fog Advisory may be
possible tonight. Outside of any drizzle overnight, we expect
the area to remain precipitaiton free overnight.


The long-term period begins with a continuation of unseasonably
mild weather, aided by southwesterly flow around and unusually
strong mid-/upper-level ridge along the East Coast. At least
some partial sunshine is expected to help temperatures reach the
low to mid 70s in most areas. A number of max temperature
records are likely to be broken; see the climate secction below.

Later on Wednesday the upper ridge begins to be suppressed and a
cold front is forecast to push south across the forecast area
Wednesday night. There does not seem to be much forcing for UVV
with the front so we have included only a slight chance of
showers for most areas with the frontal passage. The front will
result in a return to more normal temps for late February.

This front is expected to stall somewhat south of Delaware.
However the cool air looks rather shallow and low level warm
advection develops above it by Thursday and and continues into
Friday/Saturday. This WAA plus some apparent weak impluses in
the continuing SW flow aloft should result in periods of rain
for the latter part of the week and into the weekend. Confidence
in the timing however is below average. Daytime highs should
gradually increased above normal.

By Sunday a stronger shortwave trof is forecast to approach from
the west, with the associated surface frontal system to cross
the mid-Atlantic region late in the day. More widespread rain is
expect ahead of the is system on Saturday night and Sunday,
followed by clearing on Monday.


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

Today-tonight...Low clouds and fog/drizzle will persist across the
TAF sites through at least the mid-late morning hours as our area
remain no the northern side of a frontal boundary to our south.
While ACY and MIV do not have the LIFR conditions the rest of the
TAF sites do, we expect them to lower through daybreak. As the
frontal boundary to our south lifts north of the area today, we
expect an improvement to the conditions for a period this afternoon.
However, this improvement is expected to be temporary as low clouds
and fog/drizzle are once again expected to develop after sunset and
likely persist through the night. IFR conditions are expected again
tonight through Wednesday morning.

Winds this morning will be light and varialbe for many locations,
although some areas will continue with southwest winds around 5-10
knots. All areas are expected to have their winds increase to 5-10
knots out of the southwest today. Some areas will even see some
gusts around 15-20 knots, especially where the clouds break up and
dissipate. The southwest winds will continue into tonight, with some
areas becoming light and variable.


Wednesday...Fog and stratus dissipate in the morning, giving way
to VFR conditions. SW winds 10-15 kt with gusts to 20 kt.
Confidence: Above average.

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

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

Thursday night...Sub-VFR conditions possible in scattered
showers. Confidence: Below average.

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


The Dense Fog Advisory remains across the waters through this
morning. It is possible that the fog may continue through the
day, and into tonight. Even if there is some clearing during the
day today, the fog will likely redevelop this evening and
overnight. So the Dense Fog Advisory may need to be extended
later this morning, or another may need to be reissued for later

Winds and seas are expected to remain below advisory levels for
today and tonight. However, winds may gust around 20 knots at times
and seas will be around 3-4 feet.


Wednesday...SCA conditions possible on the ocean with gusty SW

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

Thursday...SCA conditions possible on the ocean waters.

Friday through Saturday...Sub-SCA conditions anticipated.


Record high temperatures are possible today and Wednesday.

Tuesday, February 20:

Atlantic City...70 in 1930
Philadelphia....70 in 1939
Wilmington......71 in 1930
Allentown.......68 in 1930
Trenton.........70 in 1930
Georgetown......68 in 2002
Mount Pocono....59 in 1930
Reading.........72 in 1930

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

A record warm minimum temperature may be set for Atlantic City
on Tuesday. The current record is 44 in 1949.

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.


PA...Dense Fog Advisory until 10 AM EST this morning for PAZ054-055-
NJ...Dense Fog Advisory until 10 AM EST this morning for NJZ001-
DE...Dense Fog Advisory until 10 AM EST this morning for DEZ001>004.
MD...Dense Fog Advisory until 10 AM EST this morning for MDZ008-012-
MARINE...Dense Fog Advisory until 10 AM EST this morning for ANZ430-431-


Near Term...Robertson
Short Term...Robertson
Long Term...AMC
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