Scientific Forecaster Discussion
fxus61 kphi 201954
Area forecast discussion
National Weather Service Mount Holly New Jersey
354 PM EDT Thu Jul 20 2017
a cold front will approach the area tonight and cross through by
Friday morning. Weak high pressure will then prevail through
Saturday. Another front and associated low pressure will be across
the area Saturday night through Monday. High pressure will then move
in next Tuesday and remain into the middle of next week.
Near term /until 6 am Friday morning/...
the spotty showers that have been developing over the lower
Susquehanna River valley and parts of Maryland, Delaware and
southern New Jersey this afternoon have not been getting much
traction. A capping inversion aloft has been limiting the vertical
development of the cells.
Our main concern is the convective complex that was moving across
parts of central New York and northern Pennsylvania this afternoon.
It is expected to impact our northern counties this evening. We will
carry the likelihood of thunderstorms in the Poconos, the Lehigh
Valley and northern New Jersey. Scattered convection may affect
Berks County, the northern suburban counties of Philadelphia and
central New Jersey, as well. We will mention the potential for gusty
winds and downpours with some of the thunderstorms. Our northern
counties remain under the storm prediction center's designation for
a marginal or slight risk of severe weather.
As the convective complex moves off the coast overnight, the
potential for showers will come to an end and the sky over our
region should become clear to partly cloudy. A surface trough
trailing the convective complex is expected to pass through our
forecast area late tonight.
The wind is anticipated to become light and variable overnight. Low
temperatures should be mostly in the 70s.
Short term /6 am Friday morning through 6 PM Friday/...
maximum temperatures on Friday will be similar to those of today.
However, the humidity is forecast to be slightly lower. We will
leave the excessive heat warning in place for the urban corridor.
However, other areas should fall a bit short of their criteria for a
The sky is expected to be mostly sunny on Friday. We will not
mention any precipitation due to the lack of any significant
triggering mechanism along with the continued existence of a capping
The wind should favor the west and southwest on Friday around 5 to
10 miles per hour.
Long term /Friday night through Thursday/...
the heat wave will continue on into the weekend, but it will gradually
weaken with temperatures more in line with normal after Monday. A
few recent model runs are showing than high temperatures around 90
degrees readings are possible Monday, something which has
changed since yesterday, but for now we will continue with upper
80s across the Philadelphia Metro area and for Delmarva too.
Dew point temperatures will be lower over the area Saturday, but
then climb back to steamy values Sunday and early Monday. A
front will cross the area Monday and drier and cooler air will
arrive behind that for the middle of next week.
Shower and tstm chances will be rather low Friday night and into
Saturday morning, but then increase from W to E through the afternoon
as the the front and humid air return to the area. High chance
to low likely pops will be over the area Sunday into Monday as
the system passes the region. Lower pops will be over the area
Tuesday and Wednesday with high pressure settling over the
Aviation /20z Thursday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
VFR conditions are expected through much of the taf period with one
A complex of thunderstorms is forecast to pass across parts of
eastern Pennsylvania and northern and central New Jersey this
evening. While the storms should remain to the north of kpne, kphl,
kilg, kmiv and kacy, they are expected to impact the areas around
krdg, kabe and kttn between about 2200z and 0200z. The thunderstorms
may bring localized wind gusts of 30 to 35 knots from the northwest.
Also, patchy visibility restrictions are possible during the late
night and early morning hours especially in areas where rain falls
We are not anticipating any showers or thunderstorms on Friday.
A light southwest wind this evening is expected to become light and
variable tonight. A light northwest wind is anticipated for Friday
morning, then it should become west and southwest as the day
Fri night thru Saturday morning...VFR expected.
Saturday afternoon thru Monday...mostly VFR. Sct showers and
tstms with lower conditions possible. Tue...mostly VFR.
high pressure over the Atlantic will continue to influence the
coastal waters of Delaware and New Jersey for tonight. A weak
frontal boundary from the northwest is forecast to arrive early on
Friday. The wind should favor the south and southwest at less than
15 knots tonight, becoming west to southwest on Friday. Wave heights
on our ocean waters will remain around 2 to 4 feet and waves on
Delaware Bay should be 1 to 2 feet.
sub-Small Craft Advisory conditions overall. The main hazard will be sct tstms
mainly between Saturday afternoon and Monday. Locally higher
winds and seas with tstms. Bring your National oceanic and atmospheric administration weather radio along
to get alerts.
The underlying 10 to 14 second southeasterly swell is forecast to
persist into Friday. As a result, we will continue the moderate risk
for the development of dangerous rip currents through that time.
the kdov dew point readings are unrepresentative of the area
and should not be used when diagnosing humidity/heat indices.
PA...heat advisory until 7 PM EDT this evening for paz060>062-101-
Excessive heat warning until 8 PM EDT Friday for paz070-071-
New Jersey...heat advisory until 7 PM EDT this evening for njz009-010-012-
Excessive heat warning until 8 PM EDT Friday for njz015-
Delaware...heat advisory until 7 PM EDT this evening for dez002-003.
Excessive heat warning until 8 PM EDT Friday for dez001.
Maryland...heat advisory until 7 PM EDT this evening for mdz008-012-015-