Scientific Forecaster Discussion
fxus61 kctp 012006
Area forecast discussion
National Weather Service State College PA
306 PM EST Wed Mar 1 2017
a deep storm system will track from the upper Great Lakes
to St. Lawrence River valley by early Thursday. Occasional
showers and isolated, brief thunderstorms will move across the
region into this evening.
A strong cold front will push east across the region tonight.
Winds will shift to the west-northwest with frequent gusts of 40
to 50 mph tonight through the mid morning hours Thursday and as
much colder air moves into the commonwealth.
Near term /until 6 am Thursday morning/...
primary area of high sfc dewpoint air around 60f and pwats of
1.0 inch has been shunted off to the east of the lower susq
valley, leaving the region in an area of weak low-mid level
ridging and subsidence. An associated period of neg Theta-E
advection at low-levels will bring some late day clearing and
marginal destabilization of the airmass as several deg c of
cooling aloft moves in from the west.
Cold frontal timing is early evening across the western mtns of
PA...and around 03z-04z across the east. Along with this cfropa
will come one or two narrow lines of gusty showers and perhaps a
Following the front,, increasing gradient and isallobaric wind
via a 3-hourly pressure rise of 5-6 mb will lead in gusty
westerly winds. Vertical mixing up to 3-4 kft agl overnight
will tap 45-50 kts of wind at that level and translate to sfc
gusts of 35 to 40 kts (possibly up to 43-45 kts on the ridges of
the northwest mtns and laurels).
P-type will likely not turn to snow over the wrn mtns until
05-06z, with a mix of sct rain and snow showers in the central
valleys. Any accumulations tonight will be very minor if any due
to warm/wet ground and scattered nature of the shsn.
Lows at daybreak Thursday will vary from the l20s across the northwest
mtns...to the u30s in the far southeast.
Short term /6 am Thursday morning through 6 PM Thursday/...
it will turn noticeably colder (and stay windy) Thursday
especially during the morning hours. Wind gusts of 35-40 kts
likely through 12-14z...before they slowly decrease during the
Lake enhanced/upslope snow showers will bring a light
accumulation to the northwest alleghenies and Laurel Highlands.
Elsewhere, the shallow strato cu clouds will support nothing
more than scattered flurries across the Central Ridge and valley
region of the state.
Afternoon high temps will be near 30f in the NW, around 40f
along the I-99 corridor, and the l-M 40s in the southeast.
Long term /Thursday night through Wednesday/...
guidance continues to show a clipper system with reinforcing
shot of cold air diving southeast from the upper Midwest through
the Ohio Valley across the central Appalachians Thursday night
into Friday morning. The system is expected to produce a swath
of light snow with orographic enhancement expected to raise
potential for higher amounts (2-3+ inches) in the Laurel
Highlands. Snow could spread east of the alleghenies but
thermal profiles and surface temperatures are marginal for
rain/snow and accums. Will need to monitor this as well as
potential for a few heavier snow showers into Friday afternoon
as core of coldest air aloft moves over the area. Area of high
pressure will follow Friday night into Saturday before a warm
front lifts through the area on Sunday. Temperatures are fcst to
bottom on Friday before moderating over the weekend and rising
above average into early next week. Warm advection clouds and
low pop showers possible Sunday night as a sharpening system
develops over the Midwest and moves towards US. Another strong
frontal system will impact central PA in the Tuesday-Wednesday
time period with rain/thunderstorms possible ahead of the cold
front followed by period of colder/windy conditions into the
later part of next week.
Aviation /20z Wednesday through Monday/...
main concern early today is llws, given strong winds aloft.
Not all areas mixing.
Some lower ceilings across the southeast. Most of the area has
good visibility. Some sites going back and fourth between lower
clouds and just a mid deck.
Band of showers and isolated thunderstorms just moving into the
far west. Activity is weakening for the most part, but still
watching for isolated strong gust. Airmass cooler and more
stable east of the higher ridges.
12z tafs sent.
A cold front will move west to east across the airspace
tonight. Showers and thunderstorms ahead of the front have, for
the most part, moved east of the area, though an isolated storm
or two could cause temporary reductions in visibilities and cigs
through 01/22z. A second area of pcpn developing now over
northeast Ohio will move into and produce reduced conds over
western PA later this afternoon and this evening.
Gusty northwest winds will overspread the region behind the cold
front passage tonight and persist into Thursday. Isolated to
scattered snow showers will develop over the northern mountains
and possibly The Laurels late tonight into Thursday with VFR
Late Thursday night and Fri...light snow/reduced visible possible,
mainly in the morning.
Sat-sun...no sig wx expected.
monthly summaries sent.
Warmest February for both Harrisburg and Williamsport.
Harrisburg had a mean temperature of 41.3 degrees. The old
record was 40.4 degrees in 1998. Williamsport had a mean
temperature of 37.0 degrees. The old record was 37.0 degrees in
Wind Advisory from 10 PM this evening to 9 am EST Thursday for
Wind Advisory from 8 PM this evening to 9 am EST Thursday for