Area Forecast Discussion
Issued by NWS State College, PA
FXUS61 KCTP 222351
Area Forecast Discussion
National Weather Service State College PA
651 PM EST Sun Jan 22 2017
A multifaceted storm will bring drenching rain, elevation-
driven snow and gusty winds to Central Pennsylvania on Monday.
High pressure and unseasonably mild conditions will briefly
return for midweek before a pattern change brings colder
temperatures and lake effect snow to close out the month.
.NEAR TERM /UNTIL 10 PM THIS EVENING/...
Another day of wildly varying conditions across Central PA ranging
from very mild spring-like weather in the Alleghenies where
temperatures reached the upper 50s to low 60s, to cloudy, cool
and foggy conditions with readings in the 40s from the central
ridge and valley region into the lower Susquehanna Valley. The
fog has been incredibly stubborn locally.
POPS trend upward from south to north later tonight as moisture
and lift increases ahead of the strong storm system tracking
northeast across the Southern Appalachians. Latest HRRR shows
rain spreading north of the Mason-Dixon line between 02-04z.
.SHORT TERM /10 PM THIS EVENING THROUGH 6 AM MONDAY/...
Rain will increase in coverage and intensity from south to
north through daybreak Monday. A tightening pressure gradient
between deepening low pressure in the Carolinas and high
pressure in eastern Quebec will produce strong/gusty east winds
early Monday morning and continue through Monday afternoon.
Issued a wind advisory for most of the lower Susquehanna Valley
with max wind gusts 45-50mph.
.LONG TERM /MONDAY THROUGH SUNDAY/...
All model data tracking closed upper low northeast across
Virginia Monday. A steady rain will overspread Pa from north to
south as strong upper lvl divergence, anomalous easterly low
lvl jet/PWATS work into the state. Thermal profiles initially
warm enough for rain everywhere. However, dynamic cooling
associated with arrival of strongest forcing will likely result
in a changeover to wet snow over the higher terrain of central
Pa. Forecast soundings suggest the highest elevations of the
Laurels/Northern Mtns could mix with or change to wet snow
around midday. By later in the day, snow could become more than
just a higher elevation threat, with thermal profiles even as
far east as AOO/UNV cooling sufficiently for all snow. Limiting
factor in terms of accumulation will be marginal boundary layer
temps and warm ground. The threat is for several inches of heavy
wet snow, especially favoring the higher elevations, across
northern Pa. A winter storm watch has been issued for the
northern counties, where 6+ inches appears possible, mainly over
the higher terrain.
Biggest threat across the Lower Susq Valley will likely be
gusty winds, the result of tightening pressure gradient
between approaching low pressure and high north of New England.
Bufkit soundings indicate wgusts in excess of 40kts are
likely across southeast Pa, as low lvl jet swings through
Monday. Per coordination with LWX/PHI, have issued a wind
advisory for this area.
Lastly, still monitoring the potential for minor flooding.
Target area for the heaviest rain is across the south central
part of the state, where orographic forcing at nose of powerful
easterly low level jet will play a role. Mean QPF from both SREF
and GEFS max out around 1.5 inches in this region, which would
be a beneficial rainfall. However, given FFG/FFH values around
2 inches, can`t rule out some minor flooding.
The surface low will reach our latitude between about 6-12Z
Tuesday, an old rule of thumb that dictated when the steady
precip tends to taper off. Upper ridging will quickly build into
the region later Tuesday into early Wednesday, bringing a short
period of fair and mild wx.
A pattern shift is advertised for the second half of the week
as low pressure takes up residence over eastern Canada, and
despite a tenacious ridge over the northern Caribbean and
Bahamas, models carve out a long wave trough over the eastern US
with a return to seasonable cold by the end of the week into
The ridge in the west and trough in the east is also usually a
good one for winter storminess, but the deterministic ECMWF and
GFS don`t show much more than a series of clipper type systems
that promise an extended period of clouds and scattered mainly
mountain snow showers that should continue through next weekend
into the week after.
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Lowering conditions, now IFR-VLIFR across much of the central
and eastern airfields, foretell the trend for this evening. VFR
conditions still exist at KBFD/KJST, but with continuing
easterly flow, even these airfields will trend lower tonight,
with IFR conditions developing at these locations between 06z
Expect IFR to LIFR conditions across the entire region late
tonight and much of Monday, with a widespread rain event moving
into the region. Late in the period across the west and north,
conditions expected to deteriorate even more as we approach
00z...with rain mixing with and possibly changing to snow.
Additionally, strong gusty winds will impact southern airfields
beginning late tonight and Monday. KMDT/KLNS may see gusts
approaching 30-35+KT. LLWS also likely at most central and
southern airfields late tonight and Monday.
Tue...Widespread sub-VFR with some improvement by aftn. Rain/snow
ending in the morning. Gusty winds from NNW decreasing late.
Wed...Low cigs/rain possible western 1/2. Breezy late.
Thu-Fri...MVFR/IFR in rain/snow showers west. MVFR to VFR east.
Winter Storm Watch from Monday afternoon through Tuesday
morning for PAZ005-006-037-041-042.
Wind Advisory from 5 AM to 4 PM EST Monday for PAZ057-059-
LONG TERM...Fitzgerald/La Corte