Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 220114
Area Forecast Discussion
National Weather Service Mount Holly NJ
914 PM EDT THU JUL 21 2016
High pressure remains south and east of the area tonight. A weak
cold front is expected to move across the region Friday night into
early Saturday. Strong high pressure will then build in before
another cold front moves through early next week. High pressure
should then briefly build back into the area Wednesday.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
High pressure located off the coast will maintain a light south
to southwest flow in our region overnight and dew point readings
will creep upward.
Cirrus debris clouds from dissipating convection over the eastern
Great Lakes should continue to drift overhead during the night.
Minimum temperatures are forecast to favor the 60s. However, some
urban locations and some areas along the coast may not fall below
the lower 70s.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Mostly sunny, hot and humid with a southwest wind gusting 15-20
mph during the afternoon. Should reach 95-96F in Philadelphia
Friday afternoon (4C warmer at 850 mb) and dewpoints around 5F
warmer during the afternoon as compared to the upcoming upper 50s
values of this afternoon. The result will be a max HI around
98-99F, possibly 100F for an hour. We may eventually need to issue
an advisory for Friday afternoon, prior to the higher impact
anticipated need for a Excessive Heat Warning this weekend.
Thunderstorm risk?: It appears a 700mb Temperatures cap of 10C
develops during the afternoon so while we cant rule out tstms...
it appears if any occur...they should be confined near or N of
I-78...roughly KPTW- KMJX northward and late afternoon, if then.
It may be that they develop and move rapidly sewd near 00z/23?
Will add gusty winds to the thunder fcst for late Fri. PWAT 1.7"
so if it thunders, rain will be briefly heavy with usual poor
drainage street flooding. Its conditional on tstms developing
which is the uncertainty.
Forecast basis was generally a 50 50 blend of the 12z/21 GFS/NAM
mos guidance, favoring the warmer GFS with support from the 2m
temps of the 12z/21 NAM and ECMWF.
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Hot wx is expected for the extendd pd. A wk cdfnt will be working
its way thru the area Fri night and will bring some shwrs/tstms
with it. The best chcs are up north and gusty wind and hail look
to be the main threats. Precip chcs shud be mainly erly.
Once this front crosses the area, high pres will build in. Sat
looks to be very hot and humid, with heat index values between 100
and 105 degrees.
Sunday and Monday, there looks to be some disagreement in the
mdls. It still looks hot, but the GFS has backed off a bit now on
Sun. The ECMWF is a bit warmer with temps on Sun, but dew points
are still lower. Mon dew points differ by 4 to 5 degrees and temps
do as well and that can make a big difference. Based on the
uncertainty, have opted to leave the excessive heat watch up for
Another cdfnt will cross the area later Mon bringing shwrs and
tstms. Then it will be slightly cooler and less humid behind the
front for the remainder of the week. However, it is very likely
that from tomorrow thru at least Wednesday of next week we will
have temperatures above 90 degrees and we could have several days
with temps in the mid and even upper 90s.
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Mainly VFR conditions are expected through the TAF period. The
only exception is the possibility of some MVFR visibility
restrictions late tonight around our more climatologically
susceptible TAF sites of KRDG and KMIV.
There is a chance that showers and thunderstorms may drop down
from the northwest and into the KRDG and KABE areas late on
Friday. However, our forecast confidence is not high enough to
include their mention in the TAFs at this time.
A light south to southwest flow is expected overnight. The wind
should settle into the southwest for Friday at speeds around 10
knots with gusts into the upper teens.
Fri night...Generally VFR. A chance of shra/tsra which may
briefly lead to MVFR/IFR. Gusty southwest winds 15-20 knots.
Moderate to high confidence, below average on mvfr/ifr.
Saturday-Sunday...VFR. High Confidence.
Monday-Monday night...Generally VFR. A chance of showers and
thunderstorms which may briefly lead to lower conditions. Gusty
southwest winds 15-20 knots.
Southerly winds will gust just above 20 kt this evening along the
northern NJ coastal waters, but are expected to remain mostly
below SCA criteria. Seas should generally be 3 ft or less.
Friday...a south-southwest wind gusty to 20 to possibly kt during
the afternoon. No SCA attm since confidence on wind above 22 kt is
below average at this time (attm). capped late Fri gusts at 24 kt
for the time being.
Fri night...SCA conditions psbl with increasing winds ahead of an
approaching cdfnt. However, confidence is low due to very warm air
over cooler waters, so nothing issued attm.
Sat-Tue...Sub-Small Craft Advisory conditions expected.
RIP CURRENTS...The risk for the formation of dangerous rip
currents Friday is moderate along the NJ shore from Atlantic
County northward and low for the Delaware Beaches and Cape May
county. Confidence on how much southerly component is a little
below average so the moderate risk may end up low enhanced.
Looking further ahead, with the Atlantic Basin still devoid of
tropical storms, the risk for the formation of dangerous rip
currents should be Low.
Next Monday the 25th, we might have enough wave height to around
4 feet and water buildup due to southerly winds, to have a more
widespread low enhanced or even moderate risk but confidence on
seas building that high is below average.
Water temperatures have rebounded after the massive upwelling
event associated with the squall line passage late Monday. Water
temps today were in the low to mid 70s, above normal for this time
of year and quite a rebound from the lower 60s of Tuesday. Colder
upwelling might develop again late Friday or Saturday.
Near record (within 2f) or record warmth is anticipated for many
sites on 1 or 2 days of the following listed.
23rd 24th 25th 26th
PHL 101-2011 98-2011 96-1899 101-1892
ABE 99-1955 95-1999 95-1999 98-1940
ACY 105-2011 100-2011 99-2010 96-2011, 1963
ILG 100-2011 98-2011 96-1987 99-1894
TTN 104-2011 98-1910 97-1999 99-1892
GED 104-2011 99-2011 99-2010 97-2012
RDG 100-2011 96-2010 96-1999 99-1940
MPO 91-1955 91-1914 90-1999 89-1949
PA...Excessive Heat Watch from Saturday morning through Sunday
afternoon for PAZ060>062-070-071-101>106.
NJ...Excessive Heat Watch from Saturday morning through Sunday
afternoon for NJZ007>010-012>027.
DE...Excessive Heat Watch from Saturday morning through Sunday
afternoon for DEZ001>004.
MD...Excessive Heat Watch from Saturday morning through Sunday
afternoon for MDZ008-012-015-019-020.