Jonestwn, Pennsylvania Weather Forecast Discussion

789
FXUS61 KCTP 160209
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
1009 PM EDT Mon Sep 15 2025
.SYNOPSIS...
* Cloud coverage gradually increases overnight with valley fog
  potential across the northern tier tonight.
* Light rain possible across southeastern Pennsylvania Tuesday
  through Wednesday.
* Dry conditions prevail on Thursday and through the first half
  of the weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
High clouds emanating from a neat-looking low pressure system
off the coast of the Outer Banks tonight continue to drift north
into Pennsylvania this evening. Despite the high clouds, high
pressure will produce light/calm winds and another night with
ideal radiational cooling and valley fog potential across the
northern tier. Low temperatures overnight into Tuesday morning
are expected to be above climatological averages, ranging from
the upper 40s across NW PA to the upper 50s across SE PA.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Low pressure will lift slowly northward from the Outer Banks
and VA Tidewater off the Mid-Atlantic coast through the middle
of the week. Latest model guidance continues to indicate the
best chance for rain over the southeast zones (southeast of
I-81/78) where a moist/upslope easterly low-level flow will
bring better moisture returns. Further north/west, precipitation
is less likely; however, aforementioned easterly flow will
allow for more expansive cloud coverage and cooler temperatures
for much of the forecast area. Most recent QPF has tapered back
ever so slightly, keeping the southern reaches of Adams/York and
much of Lancaster County above 0.10" rainfall over a fairly
tight gradient. Precipitation Wednesday night is expected to
gradually move east of the area as the coastal low begins to
push further offshore.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
A brief spell of dry conditions is once again expected in the
wake of the coastal low, with moderate-to-high confidence in dry
conditions beginning on Thursday and continuing through Saturday.
Recent model guidance has slightly slowed down with respect to
the low pressure system in the Midwest with a fair amount of
uncertainty between deterministic model guidance. Given these
changes, have decided to roll with NBM through Monday, with the
best chances of precipitation coming after sunrise on Sunday and
into the end of the long-term period.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Widespread VFR conditions expected into this evening and
overnight. Light winds and a lack of low clouds will allow for
valley fog formation again early Tuesday morning. The fog
footprint will look similar to this morning, with the best
chance of IFR conditions at BFD and IPT. Will lean on
persistence for the timing of restrictions at BFD and GLAMP for
IPT. Also included MVFR conditions toward daybreak at LNS
leaning on persistence, but high clouds could keep VFR
conditions in place throughout the TAF period. A few showers
may try to enter southeastern PA towards sunrise, but the better
chance looks to be after 12Z.
Outlook...
Tue...VFR with AM valley fog. Isolated SHRA possible late for
SE PA.
Wed-Thu...Generally VFR, some SHRA possible (20-40%) SE PA.
Fri-Sat...VFR with AM valley fog.
&&
.CLIMATE...
Astronomical fall officially begins with the autumnal equinox
on Monday, September 22, 2025 @ 2:19 p.m. EDT. The Autumn 2025
season will last 89 days, 20 hours, and 43 minutes. Daylight
saving time will end just after Halloween with clocks falling
back at 2 a.m. Sunday, November 2, 2025.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...NPB
NEAR TERM...NPB/Banghoff
SHORT TERM...NPB
LONG TERM...NPB
AVIATION...Banghoff/Bauco
CLIMATE...Steinbugl

NWS CTP Office Area Forecast Discussion