National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
495
FXUS61 KCTP 111549
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1049 AM EST Tue Dec 11 2018

.SYNOPSIS...
Seasonably cold temperatures will continue through midweek. A
fresh coating of snow is likely tonight over the northwest
snowbelt and Allegheny ridgetops. A more widespread light snow
is likely Wednesday night into Thursday morning. Milder air
will return to central PA for late in the week followed by rain
to start the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Latest GOES-16 IR shows low stratus and stratocu clouds have
eroded and drifted slightly northward late this morning as the
mean llvl wind has freshened by a few-svrl kts and backed by
about 20 degrees - more to the southwest with vertical mixing
stretching to 1.5-2.0 kft agl helping to penetrating the cloud
layer and entrain drier air aloft.

Expect some continued improvement to the clearing this afternoon
across all of the CWA except for the NW mtns where the Stratocu
deck should be bkn-ovc and fairly persistent.

It will be another seasonably cold day with max temps 5 to 10
degrees below average.

Shortwave trough moving through the interior Northeast will
bring a colder northwest flow aloft tonight. Hires models show
lake and orographically enhanced snow showers bringing a fresh
coating of snow to the northwest snowbelt and Allegheny/Laurel
ridgetops by Wednesday morning.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Narrow ridge of high pressure briefly visits the area early
Wednesday, bringing an end to any lingering snow showers or
flurries by midday. Another seasonably cold and mainly dry
period during the day Wednesday with max temps 30s still about
5 degrees below average.

A compact/closed H5 low is projected to weaken as it tracks
eastward from the Great Lakes/Ohio Valley into the northern Mid
Atlantic Wednesday night into Thursday. A consensus of model
QPFs suggest a shot of WAA light snow is probable especially
over parts of the northwest Alleghenies/higher elevations and
could result in a larger coverage of light snow accums (coating
up to 1 inch). This may be just enough for some slippery travel
Thursday morning. Confidence (and precip probs) have increased
from the previous fcst but still not a slam dunk given weakening
system and diffs in the [very light] model QPFs. Light snow may
linger into Thursday afternoon before diminishing/shifting
southeast Thursday night.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Storm system over the southern U.S. will spread milder air and
rain into the area by the start of the weekend. Model trends
indicate a slower arrival to rain with the most likely wettest
period Friday night into early Saturday. There is the potential
for heavy rain with a strong southerly LLJ and above normal PWs.
Confidence remains low concerning rainfall amounts and flooding
risk - something to monitor in the coming days. Also need to
watch the thermal profiles at the onset for possible mixed pcpn
although it looks like mostly a rain event at this point.

There are some big model differences (GFS/EC) in how the system
evolves heading into next week, which would have significant
implications on the fcst. This appears to be due to phasing
issues with the GFS merging the northern+southern stream
energy. The 00Z is does not show this which results in a more
suppressed system with low scooting off the NC coast and overall
warmer solution in the wake of the system. Very low confidence
at by the Sun-Mon timeframe given the wide model spread and
growing uncertainty.

&&

.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
Mixing of drier air aloft is expected to increase through this
afternoon, causing breaking clouds/rising cigs, and eventually
SKC-SCT020-030 conditions across the Central Mtns and Laurel
Highlands, while VFR persists in the Susq Valley and SE PA.

However, mvfr (to tempo IFR) cigs should hold tough through
this afternoon and tonightacross the northwest mountains
(KBFD).

In the wake of a Cfropa early tonight, a gusty west to NW wind
will develop across at least the Central, NW MTNS and Laurels.
Prevailing wind speeds should average 10-15kts with gusts into
the mid and upper 20s. Gusts of 30-32KT possible INVOF KJST and
KAOO.

.Outlook...

Wed...Early AM low cigs possible W Mtns. Evening light snow
possible western half of Pa.

Thu...Low cigs possible, mainly central mountains.

Fri...Rain/low cigs possible, especially late.

Sat...Rain/low cigs possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Lambert/Steinbugl
NEAR TERM...Lambert
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...Lambert/Gartner