Elmora, Pennsylvania Weather Forecast Discussion

527
FXUS61 KCTP 162320
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
720 PM EDT Tue Sep 16 2025
.SYNOPSIS...
* Cloud cover will gradually increase and lower from east to
  west across the Southern Poconos, Susquehanna Valley and
  eventually the Southern and Central Mountains later tonight
  and Wednesday, while a potential for valley fog will be found
  across the northern tier early today.
* Periods of rain, mainly light, will develop across
  southeastern Pennsylvania Today through Wednesday.
* Dry conditions return areawide on Thursday and will continue
  through the first half of the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Well defined sfc low pressure with some deep convection
occupying its NW quadrant, was located just east of Cape
Hatteras, NC and drifting slowly north-northwest.
A deepening and slightly veering ENE to Easterly LLVL flow will
develop across the Lower Susq Valley and Adj SE PA throughout
the day today. A few sprinkles could reach the ground across
our far SE counties this afternoon, followed by the NW edge of a
shield of light to MDT rain entering the Lower Susq Valley
early tonight.
To the NW of this advancing, layered cloud shield will be mainly
clear skies and light wind, leading to valley fog across
northern PA through 13Z today.
On the balance today, sunshine will be mixed initially with
mainly thin, high clouds across the Central and Northern Mtns
today before some thickening mid clouds spiral in from the
east/southeast late this afternoon/evening.
High temps today will be mainly in the upper 70s...to low 80s
across the Mid Susq Valley. Maxes could be capped off between
73-75F across portions of York and Lancaster counties where
cloud cover thickens up first under the developing cold air
damming setup.
&&
.SHORT TERM /WEDNESDAY NIGHT/...
As a result of the thicker, overcast layer of stratus (topped
by one or more layers of mid to high clouds) temps were trimmed
a bit across the SE third to half of the CWA for Wednesday.
Readings may climb no higher than the mid to upper 60s
Wednesday, along and to the SE of Interstate 81.
NBM has a difficult time achieving 100 percent cloud cover with
this fairly obvious, cold air damming setup under deepening
easterly flow. a thick overcast layer of stratus is likely
across the Lower and Mid Susq Valley by later tonight through
Wednesday with the Southern and Central Mtns likely seeing the
main surge of cloud cover after dusk this evening and seeing it
stick around through much of Wed.
Previous Disc...
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 TUESDAY/...
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 /00Z WEDNESDAY THROUGH SUNDAY/...
Current satellite/radar as of 2320Z outlines a fair area of
high-level clouds general at or above 25,000 ft with rain across
mainly southeastern Pennsylvania (MDT/LNS). Dew point
depressions remain relatively high with low-level dry air
limiting the amount of precipitation outside of the heaviest
bands this evening, which are generally expected to stay out of
the airfields. Despite this, have continue a PROB30 over the
next 1-2 hrs at LNS due to some continued development across the
region with the bulk of precipitation south of MDT.
Most recent HREF/RAP/GLAMP guidance indicates a brief period of
dry conditions at the airfields overnight; however, scattered
showers are progged by model guidance in this timeframe. Thus,
confidence remains low with respect to the precipitation
forecast overnight at MDT/LNS as showers will have some
potential to go over the airfield between 00Z-12Z Wed. Better
signals for precipitation come throughout the morning hours on
Wednesday and continuing into expand slowly north/westward with
the closest approach of the coastal low. Model guidance
indicated MDT/LNS share respectable (40-50%) chances for
rainfall with scattered coverage limiting chances at IPT/UNV/AOO
closer to the 10-30% range, thus have limited mentions for the
00Z TAF package. Some instability will be present; however,
lower confidence given easterly flow and coverage of TSRA at
MDT/LNS, thus no mentions this cycle.
Given the aforementioned easterly flow, lower ceilings are also
expected across the southern tier of Pennsylvania. Recent model
guidance has tanked MDT/LNS further down, which is plausible
given increasing low-level moisture from the Atlantic. Recent
HREF guidance indicated anywhere between 40-60% of IFR
restrictions or below throughout the afternoon/evening hours at
MDT/LNS, thus have began mentions of IFR thresholds in the 00Z
TAF. Elsewhere, MVFR will be possible (30-40%) for brief
periods at AOO/IPT; however, less convincing signals for IFR
mentions based on model guidance at this time.
Outlook...
Thu...Generally VFR.
Fri-Sun...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...Lambert/NPB
NEAR TERM...Lambert/Gartner
SHORT TERM...Lambert/Gartner/NPB
LONG TERM...NPB
AVIATION...NPB
CLIMATE...Steinbugl

NWS CTP Office Area Forecast Discussion