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 231548

Area Forecast Discussion
National Weather Service Mount Holly NJ
1048 AM EST Thu Feb 23 2017

A cold front moving through the Great Lakes today will stall
just north of our region tonight into Friday, before lifting
northward as a warm front Friday night. This will be followed by
a strong cold frontal passage on Saturday evening. High
pressure will traverse the middle Atlantic Sunday into Monday. A
frontal boundary will setup near our region during the early to
middle part of next week, and several waves of low pressure are
expected move along it.


The Dense Fog Advisory has been cancelled for the entire area
just before 10 AM. Visibilities continue to improve area wide
with all ASOS/AWOS sites reporting 1/2SM or above. 15Z visible
satellite shows whats left of the stratus deck over far northern
Delmarva, southwestern and central NJ and eastern PA (south of
I-80). These low clouds will take longer to erode (possibly not
until mid afternoon in spots) given the relatively low sun
angle right now and a lack of dry air advection. Now that we see
the whites of it eyes, it has become evident where the temperature
gradient will setup due to differential heating. Max temperatures
were adjusted accordingly. The rapid refresh guidance and 12Z
NAM was blended with the previous temperature forecast since
these newest available models seem to capture the evolution of
the stratus erosion better. Forecast highs in the lower to mid
70s in eastern MD, DE and southern NJ will be near record today
(a certainty for GED). Despite the cloudy start, there is still
a shot at reaching 70F in Philadelphia today since the city is
on the southern fringe of the stratus deck and thus should thin
sooner. Farther north, the area between I-195/PA Turnpike and
I-78 will likely struggle to reach 60F until the low clouds
erode this afternoon and then may only max out in the mid 60s.
Clear skies north of I-80 will allow temperatures to quickly
warm into the 60s before stratocu arrives ahead of a cold front
this afternoon.


Our region should be more solidly in the warm air for tonight.
As a result, we may see more stratus than fog development except
near the water. Nevertheless, we will continue to mention at
least some patchy fog for late tonight.

Scattered showers may spread across parts of eastern
Pennsylvania and northern and central New Jersey. Rainfall
amounts should be light, generally a few hundredths of an inch.

The wind is forecast to be light for tonight and low
temperatures should range from the middle 40s in the Poconos and
far northern New Jersey to the lower 50s on the coastal plain.


Active pattern in the Friday thru Wednesday period. Dense fog
is possible Friday and Friday night. There is a marginal risk of
severe thunderstorms on Saturday. There is also the potential
for daily record high temperatures on Friday, especially
Delmarva. Temperatures cool to seasonal levels on Sunday.

A more zonal flow sets up in the Monday thru Wednesday time
frame with additional chances of light precip along with a
return to above average temperatures. There is a lot of
uncertainty regarding coverage and timing of precip in the early
to middle part of next week.

Friday will feature a warm front just north of the area, with
diffuse shortwave energy moving along it. This will promote the
chance for scattered rain showers, mainly north of an I-195 to
PA Turnpike line. Given the proximity of a warm front, which may
briefly backdoor to the south, we anticipate considerable
cloudiness across much of NJ and eastern PA. This is reflected
in our temperature grids, and will likely limit record high
potential across this area. Further south across Delmarva, we
have maintained warmer temperatures (mid-70s), and thus there is
a greater potential of setting records across this area. With
the nearby frontal boundary, we expect fog through mid- morning
Friday and again Friday night. The fog could be dense, and we
have continued a mention of this in the HWO.

Saturday and Sunday...A strong cold front moves through the
region Saturday evening. The synoptic pattern is favorable for a
squall/convective line to move through much of the area, and
SPC has placed our entire region within a marginal risk of
severe thunderstorms in their day 3 convective outlook. Thus, we
maintain a chance of thunder in the forecast. Some heavier
downpours are also likely, but amounts are expected to be less
than one inch. High temperatures on Saturday are expected to
fall just shy of daily records. Fair weather is expected for
Sunday, with a return to near normal temperatures, and gusty
west-northwest winds.

Looking ahead to Monday thru Wednesday, several shortwaves will
interact with a frontal boundary that sets up near our region,
offering additional chances of light precipitation. Details in
timing and coverage continues to be low, so the forecast shows a
general slight chance of showers during this period. Snow
showers are possible Monday and Tuesday nights. We expect
temperatures to return to above average levels, generally around
5 to 10 degrees above normal.


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

At 1030 AM...Visibilities continue to improve everywhere with
the fog lifting. However, stratus deck has kept CIGs at LIFR or
IFR north and west of MIV/ACY. Expect these low clouds to
slowly erode generally between 16-19Z: first at ILG, then
PHL/RDG/ABE and last at PNE/TTN. IFR or low-end MVFR CIGs will
persist until then.

VFR conditions are anticipated from mid afternoon and into this
evening for most locations. However, convective showers and
perhaps an isolated thunderstorm may organize ahead of a cold
front this afternoon, possibly reaching RDG-ABE during the late
evening or overnight. Then a return of low clouds and fog is
expected late tonight.

A light southwest and south around 5 kt this morning will
increase to 10 kt this afternoon. Gusts at or slightly above 15
kt are likely for the southern (PHL south) mid to late afternoon.
The wind is anticipated to become light and variable again for


Friday through Saturday...There is the potential for MVFR/IFR
at times, especially Friday night, and again on Saturday with
showers and potential thunderstorms ahead of a cold front. Winds
out of the south on Saturday could gust up to around 20 knots.

Saturday night and Sunday...Becoming VFR Saturday night with
gusty west-northwest winds anticipated into Sunday, 25 to 30
knots at times.


The Dense Fog Advisory continues for the NJ coastal waters north
of Great Egg Inlet through noon. This may need to be extended
into this afternoon if the fog bank that is seen on visible
satellite is slower to drift farther offshore than our coastal
water extends out to (i.e., 20 nm out).

A southwest to south flow will continue on the coastal waters
of Delaware and New Jersey for today and tonight. Sustained wind
speeds should remain less than 15 knots with no gusts in excess
of 20 knots. Wave heights on our ocean waters should range from
2 to 4 feet. Waves on Delaware Bay will likely be 2 feet or

Another round of dense fog may occur over the waters as early
as late tonight or early Friday morning. We will consider
issuing a marine dense fog advisory sometime this afternoon.


Dense fog on Friday could potential persist into Saturday across
a portion of the waters as anomalously moist air (characterized
by dewpoints in the 50s) ahead of a cold front moves atop the
colder waters (SSTs still in the low to mid 40s).

Sub-SCA conditions are forecast Friday. SCA possible Friday
night thru Monday, with period of gales possible on Sunday. Sub-
SCA conditions are forecast Tuesday.


For reference, here are the high temperature records for
Thursday, Friday and Saturday.

Location    Thursday 2/23   Friday 2/24   Saturday 2/25

ACY         72-1985         75-1985       77-1930

PHL         75-1874         74-1985       79-1930

ILG         72-1985         78-1985       78-1930

ABE         71-1985         76-1985       74-1930

TTN         74-1874         74-1985       76-1930

GED         67-1985/1990    72-1961       76-1975

RDG         72/1932/1922    77-1985       77-1930

MPO         60-1977         60-1984       70-1930

The following monthly and seasonal expectations were
recalculated with todays max/min and then the official 330 PM
Mount Holly forecast.

It is virtually certain that the numbers below will stand and
that our forecast area is experiencing a record warm, or at
least a 2nd warmest February on record and a top 10 warmest

Records date back to the late 19th century. Details below.
These values are probably on the lower side of the solutions.


PHL 43.3. #1      Normal 35.7   Record 42.2-1925     POR 1874
ABE 37.6  #2      Normal 30.7   Record 38.6-1998     POR 1922
ACY 42.2  #1      Normal 35.3   Record 41.6-1890     POR 1874
ILG 42.3  #1 tie  Normal 35.1   Record 42.3-1903     POR 1895

Note for ABE: There is a pretty good chance ABE will end up
warmer and possibly very close to their monthly temp record.

Winter (DJF)

PHL 40.1 #7

ABE 35.4 #5

ACY 39.6 #10

ILG 39.1 #6 tie

Past two years of monthly average temperatures through February
2017, a summary of above normal months listed below:

For ABE: 23 consecutive months of above normal temps!

FOR PHL: 22 of the past 23 months have been above normal.

For ACY: 19 of the past 23 months have been above normal. For ILG:
17 of the past 23 months have been above normal.

(Jan Feb March 2015 was the last time we had significant and
persistent below normal monthly temps.)


Atlantic City should/could end up tied for 5th least snowiest
February on record.


MARINE...Dense Fog Advisory until noon EST today for ANZ450>452.


Near Term...Klein
Short Term...Iovino
Long Term...Franck
Climate...Drag/Klein is the U.S. government's official web portal to all federal, state and local government web resources and services.