Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 201017
Area Forecast Discussion
National Weather Service Mount Holly NJ
617 AM EDT SAT AUG 20 2016
Weak high pressure is forecast to influence our weather for today
and tonight. A strong cold front is expected to approach from the
west on Sunday and it should pass through eastern Pennsylvania,
northeastern Maryland, Delaware and New Jersey on Sunday evening.
High pressure is anticipated to follow and it should build across
our region during the period from Monday through Thursday. Another
cold front is forecast to approach from the northwest on Friday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Our region will between a backdoor cold front to our northwest
and a trough of low pressure along a forming front to the south. A
warm and moist southeasterly flow will be in place behind a
departing low pressure system and a cold front to our west which
will approach the region later in the weekend.
Any fog should burn off quickly after sunrise as winds from the
southeast pick up a little in the morning hours. A hot and humid
afternoon is expected with modeled boundary layer temperatures
yielding highs around 90 for most of the region, cooler NW.
Overall the MET/MAV may be 1-2F to cool for today. Humidity may
also be a touch on the higher side than what model guidance is
indicating for today but the heat index values should stay well
below advisory levels. Some time in the shade or bringing a bottle
of water with you may still not be a bad idea if outdoors.
The backdoor cold front looks to give the region the best chance
for a pop-up shower or thunderstorm this afternoon. Right now
prefer the direction the HRRR and ECMWF(00z) are going. They form
a few spotty brief showers/thunderstorms from Morris southeast
into Ocean county. The higher terrain may provide enough lift as
well to form an isolated shower or storm as well in northern NJ,
the Lehigh Valley and the Poconos. Any rain should not last long
and it is not likely to impact today`s outdoor plans for an
extended time. Given the spotty nature of this activity only have
slight to low chance pops with little qpf.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
Tonight, the backdoor cold front will likely decay with the
frontal system to the south lifting north as a warm front. Our
region will still see a direct southeast flow into the region
channeling in plenty of moisture. Temperatures will be slow to
fall for most of us with a few more clouds around. Still lows
should fall below 70 in most spots, low 70`s for PHL. For now, the
forecast remains precipitation free despite a warm airmass in
place as any triggers for showers and thunderstorms are still
south and west of the region.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Sunday continues to appear as though it will be an active weather
day in our region. We will mention clouds and a chance of showers
during the morning hours as warm moist air continues to advect
into our region.
A strong cold front will approach from the west on Sunday
afternoon. The lift ahead of the system along with increasing
instability will result in showers and thunderstorms. The forecast
wind profiles ahead of the front suggest the potential for some
organized storms. The winds aloft should begin to veer during the
afternoon and speeds will likely be on the increase. The Storm
Prediction Center has placed much of our forecast area under a
marginal risk for severe weather.
Also, a narrow band of precipitable water values in the 2.3 to
2.4 inch range is expected to be drawn northward and into our
region ahead of the front. The developing convection should be
able to tap into the abundant moisture and there is the potential
for heavy rain along with flooding on small streams and in areas
of poor drainage.
The most significant of the weather is anticipated to move from
west to east across our forecast area ahead of the cold front,
between about 4:00 PM and 10:00 PM. The actual front is expected
to arrive in eastern Pennsylvania during the early evening and it
should pass off the coast before midnight.
High temperatures on Sunday should be mainly in the 80s with dew
point readings favoring the lower 70s.
Once the cold front passes, there will be a noticeable change in
air mass. High pressure is expected to build from the Ohio River
Valley on Monday to our region on Tuesday. The center of the high
is anticipated to pass off the coast on Wednesday.
Maximum temperatures during the period from Monday through
Wednesday are forecast to favor the lower and middle 80s in our
region, with locations in the north not getting out of the 70s,
especially on Monday and Tuesday. Dew point readings should drop
into the 50s. Overnight lows will be in the 50s and 60s.
We are expecting to be in the return flow on the back side of the
high for Thursday and Friday. As a result, there should be a
gradual increase in heat and humidity at that time. We will
mention a chance of showers and thunderstorms on Friday with a
cold front anticipated to approach from the northwest.
.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Some patchy fog is ongoing at KMIV and KACY with occasional MVFR
VSBYS. Any fog should burn off by 13z.
Winds will stay under 10 knots from the southeast throughout much
of the day. A brief isolated shower or thunderstorm can not be
ruled out, but given the small chance of impact at a TAF site, no
inclusion in the 06z TAFS. VFR conditions for the afternoon and
evening hours today.
Sunday and Sunday evening...Deteriorating conditions are expected
as a strong cold front approaches from the west. Showers and
thunderstorms with heavy rain and gusty winds are anticipated
during the afternoon and evening hours.
Sunday night...Conditions improving overnight as showers and
thunderstorms pass off the coast and move out to sea.
Monday through Wednesday...Mainly VFR.
Wave heights are expected to continue to be around one foot for
most of today likely increasing closer to two feet tonight. Winds
will continue to be from the east and southeast around 10 knots
through tonight. No SCA headlines.
Sunday and Sunday night...No marine headlines are anticipated.
Monday and Monday night...Northwest wind gusts may approach 25
Tuesday through Wednesday...No marine headlines are anticipated.
The rip current risk is expected to be low today. However, if
southeast winds this afternoon increase a bit more than expected
at the shore then some beaches could see conditions that match the
moderate risk category.
The probable risk for the development of dangerous rip currents
on Sunday is low approaching moderate.