Scientific Forecaster Discussion
fxus61 kphi 221954
Area forecast discussion
National Weather Service Mount Holly New Jersey
354 PM EDT Thu Aug 22 2019
a slow moving cold front will track through the forecast area
tonight into Friday. The front will settle well to our south through
early next week as high pressure builds to our north. The high will
retreat northward on Wednesday as low pressure lifts northward off
the eastern Seaboard and a cold front approaches the region from the
west. The cold front is then forecast to move into the mid-Atlantic
region late next week.
Near term /until 6 am Friday morning/...
a cold front extended southwestward from northern New England,
across northern and western Pennsylvania, to the middle Mississippi
River valley at mid afternoon. The boundary will continue to sink to
the south and through much of our region overnight.
An initial batch of showers associated with a mid level impulse was
passing across far northern New Jersey around 3:30 PM. It will move
through the lower Hudson River valley and into southern New England.
Meanwhile, a line of showers and thunderstorms was developing along
the cold front in north central and western Pennsylvania. It is not
expected to reach Berks County, the Poconos and the Lehigh Valley
until around sunset.
We continue to expect locally heavy rain and gusty winds with the
showers and thunderstorms this evening. They are forecast to
progress slowly to the southeast, reaching the Interstate 95
corridor late this evening.
Once we get close to and past midnight, the showers and
thunderstorms are expected to weaken as conditions stabilize a bit.
The precipitation is not anticipated to reach southern Delaware and
far southern New Jersey until after midnight. By that time, much of
the lightning activity should have dissipated.
A southwest to west wind around 5 to 10 miles per hour is expected to become
light and variable around the time of the frontal passage before
settling into the northwest and north around 5 to 10 miles per hour in its
wake. Tonight's low temperatures are forecast to range from the
upper 50s in the Poconos to around 70 on the coastal plain of the
upper Delmarva and southern New Jersey.
Short term /6 am Friday morning through 6 PM Friday/...
the cold front is forecast to extend across far southern New Jersey,
central Delaware and adjacent areas of northeastern Maryland around
daybreak on Friday. It expected expected to drift southward,
reaching the Virginia CAPES late in the day. The slow movement of
the boundary will translate into a very gradual improving trend from
north to south in our region on Friday.
We will keep a chance of showers from the Philadelphia metropolitan
area and southern New Jersey southward for Friday morning. We will
limit the mention of showers to areas from about Dover Delaware and Ocean
City New Jersey southward for the afternoon. It appears as though any
substantial instability will have drifted to our south by Friday
morning, so we will not include any thunder.
It should remain mostly cloudy across northeastern Maryland,
Delaware and southern New Jersey through the day. However, some
clearing from the northwest and north is anticipated for eastern
Pennsylvania, and for northern and central New Jersey.
The wind is expected to be from the northwest and north around 10
miles per hour. Temperatures will be considerably cooler than those of recent
days with highs mostly in the 80 degree neighborhood. Readings will
likely not get above the lower and middle 70s in the elevated
terrain on the Poconos and far northern New Jersey.
Long term /Friday night through Thursday/...
the long term forecast will begin with below normal
temperatures and more comfortable dewpoints and end with normal
to above normal temperatures and greater chances of convectively
For Friday night, lingering showers and thunderstorms could remain
across southern New Jersey, and southern Delaware and Maryland. Precipitable water
values remain near 2.0 inches, so some locally heavy rain is
Saturday could end up the better of weekend days as high pressure
builds well to our north across eastern Canada and winds just start
to turn onshore. Temperatures will be below normal.
The period between Sunday and Tuesday, could see more cloud cover
and light precipitation. This is due to a persistent onshore flow.
Guidance, for a couple of days now, is showing precipitation for
this period. However onshore flow can manifest itself in a number
ways...low clouds, fog, drizzle or light rain. At a minimum, expect
some cloud cover along the coastal plain.
As we move into Wednesday and Thursday, unsettled weather should
return to the area. An area of low pressure is forecast to be
lifting northward offshore of the East Coast, while a cold front
approaches from the west. Showers and thunderstorms are likely to
develop as the cold front nears the forecast area.
Aviation /20z Thursday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...mainly VFR. However, conditions will lower to MVFR and IFR
in showers and scattered thunderstorms. The thunderstorms may bring
locally heavy rain and isolated strong wind gusts. West to southwest
wind around 10 knots becoming northwest to north 5 to 10 knots.
Friday...mainly VFR. A chance of showers, mainly from the kphl area
southward. Northwest to north wind 5 to 10 knots.
Friday night...VFR except MVFR possible across southern NJ, southern
de, and the Eastern Shore of Maryland due to showers and thunderstorms. North
to NE winds mainly 5 to 10 kts.
Saturday-Saturday night...mainly VFR conditions expected. MVFR
conditions possible at kacy and kmiv Saturday night as an onshore
flow generates some clouds. Winds generally NE 5-10 knots.
Sunday...mainly VFR conditions expected. MVFR conditions possible at
kacy and kmiv as an onshore flow generates some clouds/drizzle/light
rain. NE winds 5-10 kts with gusts up to 20 knots possible.
Sunday night-Tuesday...more widespread MVFR conditions developing
with the persistent onshore flow. East to NE winds 5-10 kts with gusts
up to 20 kts possible.
a south to southwest wind 10 to 15 knots this evening, becoming
northwest to north around 10 knots overnight. North wind around 10
knots on Friday, becoming variable 10 knots or less late in the day.
Waves on our ocean waters are forecast to be around 2 to 3 feet.
Waves on Delaware Bay are expected to be 2 feet or less.
Friday night-Saturday...sub-sca conditions expected much of the
period. Low end Small Craft Advisory conditions possible late Saturday.
Saturday night...low end Small Craft Advisory conditions possible due to long fetch east
to NE winds developing.
Sunday-Tuesday...a prolonged low end Small Craft Advisory may be needed through the
period as long fetch east to NE winds persist.
A south to southwest wind 10 to 15 miles per hour is forecast into this
evening. Breaking waves around 3 feet are anticipated along with a
medium period southerly swell. There is a low risk for the
development of dangerous rip currents.
A northerly wind around 10 miles per hour is expected for Friday. Breaking
waves around 2 to 3 feet are likely along with a medium period
southerly swell. Again, a low risk is forecast.
A long duration northeast to east wind is expected for the weekend
and into the early part of the new week. As a result, we are
anticipating a prolonged period with an enhanced risk for the
development of dangerous rip currents from Saturday through at