Scientific Forecaster Discussion
fxus61 kphi 161859
Area forecast discussion
National Weather Service Mount Holly New Jersey
259 PM EDT Mon Sep 16 2019
a weakening low pressure system will move into the mid Atlantic
region today, pushing a frontal boundary to our south. High
pressure builds across the northeast states on Tuesday into
Wednesday, then shifts southward across the mid Atlantic region
Thursday. The high is forecast to shift to our south Friday,
then offshore over the weekend.
Near term /until 6am Tuesday morning/...
A cold front currently over the northern third of the forecast
area will gradually push southward through the afternoon into
the evening/overnight period. There is some modest deep layer
moisture over the area with pwats around 1.5 inches, however
most of this moisture is concentrated in the 850 to 700mb layer
(near current cloud bases) with drier air in place near the
surface. Consequently don't expect much rainfall with this
boundary due to the dry low-lvls and the mid-upper lvl dynamics
associated displaced north of the area. Nevertheless deferred
somewhat to the cam simulations and went with generally slight-
chance pops through the period, gradually shifting southward
with the boundary. Guidance does indicate a subtle shortwave
moving into Delmarva after midnight which could ignite or re-
ignite the showers, but still don't expect anything significant.
Otherwise expect mostly cloudy conditions to prevail, with
clouds gradually clearing from north to south through the
overnight (although some clouds will likely remain over Delmarva
into Tuesday morning).
Short term /Tuesday/...
High pressure builds to our north tomorrow, with a drier and
cooler northeasterly flow prevailing. It should be a relatively
pleasant day with abundant sunshine and highs in the mid to
upper 70s with fairly low humidity.
Long term /Tuesday through Sunday/...
current long range forecast looks on track with a relatively
tranquil pattern through the weekend.
High pressure is forecast to build across New England Tuesday night
into Wednesday, then shift southward across the mid Atlantic region
on Thursday. The high is then expected to build to our south on
Friday, then offshore of the southeast states over the weekend. With
high pressure and its subsidence near the East Coast for the rest of
the week into the weekend, dry conditions are currently forecast,
although there will likely be periods of cloud cover at times.
A cold front will approach the area from the west on Monday, and a
pre-frontal trough may develop ahead of the front. There is a slight
chance that showers may accompany this trough and frontal passage
Temperatures will be near or slightly below normal Wednesday and
Thursday, before rising back above normal Friday, and especially
over weekend into Monday.
Aviation /18z Monday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Today/tonight... VFR conditions expected albeit with some
ceilings likely in the 4-6k ft range. A few showers will be
possible but don't expect any operational impacts. Light and
variable winds generally becoming prevailing northeast 5-10 kts
late this afternoon into this evening.
Tuesday...VFR conditions expected with northeasterly winds
around 10 kts.
Tuesday night-Saturday...generally VFR conditions with light winds.
Winds and seas will gradually increase Tuesday, potentially
approaching Small Craft Advisory criteria by Tuesday afternoon on Atlantic
waters. Seas will generally run 4-5 ft with northeasterly winds
gusting around 20 kts.
Tuesday night-Thursday...Small Craft Advisory conditions likely as
wind gusts increase to around 25 knots and seas increase to 5-8 feet
for portions of the Atlantic coastal waters.
Thursday night-Saturday...winds lower below advisory levels,
however, seas will average 6 to 10 feet for the Atlantic coastal
A moderate risk of rip currents is anticipated for Tuesday as
northeasterly winds increase to 15-20kts and seas build to
4-5ft. An elevated risk of rip currents (e.G. Either moderate or
high) will likely persist through much of the week