Scientific Forecaster Discussion
fxus61 kphi 192238
Area forecast discussion
National Weather Service Mount Holly New Jersey
638 PM EDT Fri Jul 19 2019
Bermuda high pressure will remain in control of the weather much of
the weekend. A few weak system will move north of the area tonight
and Saturday. A strong cold front will approach Monday and cross the
area by Tuesday. Cooler and drier air will follow this front and
remain into the middle of next week. High pressure will settle
across the area from the Great Lakes region.
Near term /until 6 am Saturday morning/...
630 PM update: monitoring storms in southern New York and
northern Pennsylvania early this evening. Not too impressed with
the hi-res simulations of this convection thus far. However, the
storms appear to be strongly tied to diurnal heating. Suspect a
general weakening trend will be in the cards during the evening
hours, though a couple of the storms may reach far northern
portions of the County Warning Area between 8 PM and midnight (before suspected
complete dissipation). Current forecast looks reasonable, and no
significant changes were made at this time.
Main story in this near term period is the building mid-level
ridge and the excessive heat. Latest 2 PM observations show
dewpoints in the middle to upper 70s and heat indices in excess
of 105. In the most urban environments overnight tonight,
temperatures may not drop below 80 degrees. And that's the
issue...lows around 80 will offer very little recovery before
temperatures climb once again after daybreak Saturday.
Elsewhere, low temperatures will be in the 70s, this includes
the Poconos and northwest New Jersey.
It appears the majority of the region will remain lightly capped
into this evening. This will help to prevent convection. But there
are some showers and thunderstorms developing out ahead of the mesoscale convective vortex
well to our west. These showers and thunderstorms may clip our zones
tonight north of I-78.
Skies will be partly cloudy north to mostly clear south overnight.
Winds will be light from the southwest. Some light fog is possible
Short term /6 am Saturday morning through 6 PM Saturday/...
excessive heat warning remains in effect for the entire area.
Saturday will be the hottest day of the year thus far (sunday could
top saturday). Actual air temperatures will be in the 90s. The most
urban areas will approach 100. Dewpoints will be similar to today,
in the mid to upper 70s. So with the added heat, apparent
temperatures will exceed today and climb into the 110 to 115 range.
Winds will be out of the west/southwest 10 mph or less. There will be
little breeze to offset the heat. The exception will be the beaches,
close to the water and where a seabreeze should develop. With the
westerly flow, the seabreeze will not penetrate far inland.
With all the heat, soundings show a capped environment most of the
day tomorrow. There may be a little window of opportunity for
convection to develop across terrain or the surface trof. No more
that slight chance pops have been added across our western zones.
Most will remain dry.
Long term /Saturday night through Friday/...
excessive heat warning remains in effect through Sunday.
A transition from heat wave back to below normal temperatures
during the long term. As usual, a round of tstms will occur
during the transition. The extremely humid air mass will cause
the tstms to be accompanied by heavy rains and possible flooding.
Sat night...mostly fair but a few showers/tstms possible across the
southern Poconos. Hazy. Hot and humid. Lows in the upper 70s to low
Sunday...continued hot and humid, but tstm chances higher then Sat
with an approaching cold front northwest. Highs again upper 90s with some
100's in some areas. Excessive heat warnings will continue.
Sunday night thru Monday night...a cold front slowly crosses the
area. Occasional tstms with severe weather and flooding possible.
Highs Monday about 10 degrees cooler than Sunday (mostly low 90s),
but humidity still high.
Tuesday and Wednesday...a few showers early across Delmarva,
but overall fair and much more comfortable. Highs will be a
little below normal with readings Tue/Wed in the low/mid 80s.
Thu/Fri...much uncertainty. Temperatures back near normal.
Mostly fair, can't rule out a few afternoon showers both days.
Aviation /00z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...mainly VFR. There could be some MVFR visibilities across
the climatologically favored terminals toward daybreak. Variable
wind 5 kt or less.
Saturday...generally VFR. MVFR is possible due to visibility
restrictions in haze...mainly in the morning. West-southwest wind 5
to 10 kt.
Saturday night...hazy. MVFR vsbys possible.
Sunday thru Tuesday...sct tstms with low visibilities and ceilings possible.
MVFR haze outside of the showers/tstms. Best chc for tstms Monday.
Wed...VFR. Fair weather.
tonight...sub-sca conditions expected. There could be some wind
gusts from the southwest in excess of 20 kt this evening, but they
will subside into the 10 to 15 kt range overnight. Seas will be in
the 3 to 4 foot range.
Saturday...sub-sca conditions expected. Winds less than 10 kt with
seas 2 to 3 feet.
Winds will remain well below Small Craft Advisory criteria Saturday night and early
Sunday. After that, winds and seas will increase, but probably still
remain sub-Small Craft Advisory as a cold front approaches the waters. Thunderstorms
with strong winds gusts are possible Monday into Tuesday.
Breaking waves around 2 to 3 feet are expected along with a medium
period south to southeast swell. As a result, there should be a
low risk for the development of dangerous rip currents for the
rest of today.
Conditions are forecast to be similar on Saturday, with the low
risk expected to continue.
record maximum high and low temperatures for:
site high/year low/year
Abe 99/1930 74/2013
Acy 98/1963 79/2013
phl 100/1930 81/2013
ilg 100/1999 81/2013
ridge 100/1930 78/1952
ttn 98/2011 79/2013
mpo 92/1991 70/2013
Ged 101/1953 77/2013
site high/year low/year
Abe 101/1980 76/1942
Acy 97/1991 79/2015
phl 99/1930 81/2015
ilg 100/1895 79/2015
ridge 100/1980 77/1942
ttn 99/1980 78/2015
mpo 93/1980 69/1988
Ged 100/1977 81/2013
site high/year low/year
Abe 101/1980 75/1980
Acy 99/1981 77/1991
phl 103/1930 79/2017
ilg 102/1957 77/1972
ridge 102/2011 77/2011
ttn 101/1930 78/1980
mpo 94/2011 72/2011
Ged 101/1957 79/2017
PA...excessive heat warning until 10 PM EDT Sunday for paz054-055-
New Jersey...excessive heat warning until 10 PM EDT Sunday for njz001-
Delaware...excessive heat warning until 10 PM EDT Sunday for dez001>004.
Maryland...excessive heat warning until 10 PM EDT Sunday for mdz008-012-