Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 220535
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1235 AM EST Sun Jan 22 2017

.SYNOPSIS...
Unseasonably mild weather will continue through the weekend.
A complex and dynamic storm system will bring the potential for
heavy rain, accumulating snow and strong winds to portions of
Central PA on Monday. The mild conditions will last into the
middle of next week before a pattern change brings colder air
and more seasonable temperatures to close out the month.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Areas of dense fog are not budging despite mid and high cloud
shield and upper trough swinging ENE across central PA late
this evening. Extended existing Dense fog Advisory for the
overnight hours east of the Allegheny Plateau, where areas of
dense fog are fairly widespread. Unseasonably mild overnight
conditions will be felt throughout with mins some 20 to 30
degress above normal for late January.

Some patchy drizzle or sprinkles may fall from the stratus but
kept POPs below 20 percent as per previous forecast.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Closed mid-level low tracks from the ARKLATEX to western VA/NC
by 23/12z. Moisture and inflow will increase ahead of the mid-
level system and should support rainfall pivoting northward into
southern areas by the end of the period. Model QPFs indicate
the main rain axis stays to the south of the PA/MD line although
placement highly anomalous easterly flow of high PW air into e-w
frontal zone has me a bit concerned. One thing of note is an
increase in winds over the Lower Susq. valley with gusts over 40
mph possible by daybreak Monday. Temperatures stay very mild
and well-above normal for this time of year.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
All model data tracking closed upper low northeast across
Virginia Monday. Continue to maintain 100 pct POPs across the
entire region, given the strong upper lvl divergence, anomalous
easterly low lvl jet and associated PWATS. Latest GEFS/SREF
also both support the 100 POP forecast. Initially, model temp
profiles are warm enough everywhere for rain, but dynamic
cooling associated with the strongest forcing will likely
support a change to snow, at least temporarily, over the higher
terrain of central Pa. GEFS/SREF ptypes still strongly favor
rain, but based on operational model soundings and colder 12Z
ECMWF will maintain mention of snow over the central counties.
Best chance of accumulating snow based on soundings is across
the northern Mtns, where a few inches of accum appear probable
by Mon evening. Uncertainty too high to mention accums further
south, but the potential for a few inches of wet snow remains
from the Laurel Highlands into the Central Mtns.

Another area of concern is the potential for 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
lvl jet will play a role. Mean QPF from both SREF and GEFS max
out around 1.5 inches in this region, while FFG/FFH is around 2
inches. However, locally higher amounts seem probable and are
hinted at by the higher resolution NAM, so will mention the
possibility of minor flooding in the HWO for this area late
Monday.

Lastly, Bufkit soundings indicate wgusts in excess of 40kts are
possible across southeast Pa, as low lvl jet swings through
Monday. Per coordination with LWX/PHI, will hold off on an
advisory pending increased confidence from later models.

Precip will lift out of the region Monday night, as sfc low
passes off the NJ coast. Upper ridging will build into the
region later Tuesday into early Wed, bringing fair and mild wx.
A shortwave passing across the eastern Grt Lks will push a cold
front thru Pa late Wednesday, accompanied by sct showers, then a
shift toward colder wx is progged by all med range guidance for
the Thu-Sat time frame, as a deepening upper lvl trough forms
over eastern North America. Best chance of precip will be in the
form of lake effect snow showers across the NW Mtns during this
time, with dry weather likely elsewhere.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Some showers on the radar at midnight. Main issue is low clouds
and areas of dense fog.

06Z TAFS sent.

More detail below.

Widespread IFR-LIFR continue over much of central and eastern
airfields early this evening. Areas in the western mountains
have mixed into the warm air, and continue to experience VFR
conditions. Expect IFR-LIFR conditions to persist over the
region overnight. In those areas that are clear and VFR, also
expecting fog to redevelop overnight with moist surface
conditions and light winds.

Approaching shortwave and associated light showers may bring a
slight improvement to conditions after 03z...but generally a low
cig/vsby night in store for most of the region.

Outlook...

Sun...IFR-LIFR early, some slight improvement to MVFR/IFR during
the day. Rain spreads from south-north Sunday afternoon and
evening.

Mon...Rain/low CIGs likely.

Tue...AM rain/snow and low CIGs possible.

Wed...Reduced CIGs/showers possible NW.

Thu...MVFR/IFR in rain/snow showers mainly west.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 7 AM EST this morning for PAZ012-018-
019-025>028-034>037-041-042-045-046-049>053-056>059-063>066.

&&

$$
SYNOPSIS...Steinbugl
NEAR TERM...DeVoir/Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Fitzgerald
AVIATION...Jung/Martin



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