746
FXUS61 KCTP 272021
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
321 PM EST Thu Nov 27 2025

.SYNOPSIS...
* Lake effect snow will result in significant Thanksgiving
  holiday travel disruptions across northwest Pennsylvania
* Scattered snow showers and a few squalls will impact the
  weather across the Central Mtns, Laurel Highlands and possibly
  the Middle Susquehanna Valley Thanksgiving Day into Friday
* A few periods of snow (Northern PA) and snow/or a wintry mix
  (Southern PA) late Saturday Night and Sunday
* A more significant/widespread winter storm possible Tuesday
  and Tuesday night

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Seems like the vertical/speed shear and, to a lesser extent, the
very meager daytime mixing is keeping the influx of moisture
from becoming more streamers/bands. It is cellular or fragmented
bands at best. Thus far, only BFD has been down below 1SM and
that was only briefly for a couple of times. Tough to get the
snow to pile up when it`s light and windy at the same time.

The persistence of the flow across the lakes, some connections
to upstream lakes and upslope into the Allegheny Plateau should
still generate brief times of heavy snow overnight. The mean
9H-7H wind flow will gradually, but only slightly, veer this
evening. That will bring the best bands down into the central
mtns/I-80 corridor and upslope with a LM connection will help a
little snow stick on the Laurel Highlands, too. Have not
adjusted the snow amounts much at all, but the addition of 0.10"
or so to the far nrn counties has prompted adding another 1-2"
to the storm total snowfall for Potter and Tioga Counties. The
snow should last longer in Potter County than Tioga. Potter`s
closer proximity to the lakes and slightly higher elevations
should nudge them into totals ranging from 3-8" while Tioga
will probably not see any point amounts of 6", and much of the
county could see <2". But, the averages warrant an advy. This
configuration also lines up with the neighbors` WWAs.

Wind gusts have not been as strong as expected, even on top of
the Laurels, so we canx the wind advy early. But, we`ll still
have gusts in the 25-33KT range through the next 30 hrs with
little change in pressure gradient/magnitude.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Multi-lake fetch on Friday and early Friday night will continue
generating snow bands, with some being heavy at times. Details
will, of course, be very difficult to come by. The bands will
likely have reached their southward extent in the morning. They
should waggle slowly northward through the day. That should
improve conditions over the Laurels in the  early aftn, and
central mtns late in the day or at least by midnight. Again,
the heaviest snow will be falling from the longest bands with
the best upstream connections. Most guidance keeps the
longest/best band just north of the CWA, but the certainty of
this is low/medium. Highest chc of 1+"/hr rates out of the HRRR
guidance is over McKean and Potter Cos late tonight and Friday
morning. As mentioned earlier, there is enough support from the
NBM and WPC guidance to level up the advy in Potter to a
warning, and add Tioga to the stripe of advy. We may need to
extend the higher PoPs later in time for the N, at least. The
flow doesn`t look like it should quite take things all the way N
of the CWA until well after midnight/closer to sunrise on Sat.
Both GFS and NAM paint some QPF N of rte 6 between 06-09Z.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
The lake effect snow pattern comes to an end Saturday morning
as low-level flow backs and high pressure begins to build in,
resulting in a lowering subsidence inversion. There is still
some uncertainty with speed/timing, but overall guidance agrees
in bringing another round of precipitation for the area on
Sunday. Thermal profiles appear to be cold enough to initially
support snow, then perhaps mixing with or changing to rain for
the last day of November. Unsettled weather will continue into
early next week as cold air in the middle of the country sets up
a strong baroclinic zone over the eastern US. Will be watching a
system for Tuesday as current long range models indiocate a low
pressure system along the southeast coast but differ somewhat in
timing and track.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
A westerly-flow lake effect scenario has set up for the area
with the main concerns being flight category changes at KBFD in
SHSN and the gusty winds everywhere else.

Lake effect snow is making its way across northern PA with
intermittent flight category changes at KBFD from MVFR to IFR to
LIFR and back. Instead of a long narrow snow band, the area is
seeing more of a cellular cluster of heavier snow bursts as mid
and upper level winds break the snow bands apart as they move
farther from the lake shore. This will keep the ceilings and
visibility bouncing up and down at KBFD for the remainder of
the forecast period.

Elsewhere, gusty west winds will also continue through the
period. Winds will increase somewhat later today with some gusts
approaching 30KTS at times. Given the gusty nature, have left
out LLWS wording as these gusts would imply wind shear. Several
PIREPs indicate such across the area.

Winds at 700mb and 850mb begin to diminish Friday morning so
expect the lake snow coverage to decrease as well. However,
enough moisture remains to leave the entire area with a
StratoCu MVFR ceiling through the end of the period.

Outlook...

Sat...Improving conds; diminishing winds with lingering snow
showers ending.

Sun...Light rain/wintry mix developing from west to east;
restrictions possible. Precip may turn to rain across the south
during the day.

Mon...Mixed/wintry precip likely. MVFR likely. IFR poss.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Lake Effect Snow Warning until 1 AM EST Saturday for
PAZ004>006.
Winter Weather Advisory until 1 AM EST Saturday for PAZ010-011-
037.

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Tyburski
AVIATION...Tyburski