Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 281134
Area Forecast Discussion
National Weather Service State College PA
634 AM EST Tue Feb 28 2017
Southerly wind today and Wednesday will continue to bring
milder air and a bit more moisture into the region. Low
pressure will move across the Upper Great Lakes and track north
of Pennsylvania on Wednesday. Severe weather is possible on
Wednesday in advance of a potent cold front slated to pass
through late Wednesday. Much colder air is in store for late
week, with sub-normal temperatures likely over the weekend.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Clouds thinning across the entire area, especially in the south.
Expect some decent heating today before the short wave trough
resulting from current convection in the lower OH valley moves
overhead or just to the south. Temps should get into the 60s
today in the SE half and m-u50s elsewhere. Best chance for
showers later today is in the southern half of the area,
especially south of the Turnpike. Will mention a slight chance
of thunder there, but am not convinced it will produce thunder
with dewpoints pretty low. The dewpoints may rise into the
upper 40s in the far SE by sunset, so they will have the best
chance for a rumble. QPF is still expected to be rather light
and any rain/showers will be spotty in the north.
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Showers associated with the first wave will slide to the east
this evening, and a more significant wave will roll into the NW
later in the night. POPs high as many folks will get wet late
tonight and through the morning on Wed. Dewpoints will still be
rather low, especially in the NW, so thunder overnight and in
the morning is not a certainty. Will include it as a slight
chance for that time frame.
The interesting and most-challenging part of the forecast comes
in the second half of the day and evening on Wed. As has been
advertised well over the last few days, the set-up will be
highly similar to last Saturday wwith a strong cold front moving
in from the west late in the day. SPC has upgraded to place the
entire area into a slight risk for severe weather on Wed
aftn/evening. Strong llvl winds and good height falls/cooling
aloft are certainly in store. However, the wild card is the
amount of sunshine which will occur and therefore how much
heating/instability develops. The showers in the morning can do
one of two things - either moisten things up, sufficiently
raising the dewpoints and lowering stability and LCLs, or they
may make low clouds linger long enough to keep it too cool for
widespread severe parameters to be met. Most likely there will
be lots of convection, but just how deep and how widespread the
severe threat will be is in question. Have taken a small step to
mention gusty winds with the categorical POPs drawn in the
afternoon (and lasting into the evening in the SE).
The cold front timing is pretty solid with a significant veering
to the west and temp drop occurring about or slightly before
sunset in the very late aftn W and evening E. The leading edge
of the main surge of cold air may wait until a few hours after
that. So the p-type will likely not turn to snow in the W until
midnight-ish. Any accumulations Wed night will be very minor if
any due to warm/wet ground and scattered nature of the shsn.
Gusty west wind will occur as and after the front passes. values
are up close to advy level on the ridges, but will keep them
just below for the time being.
.LONG TERM /THURSDAY THROUGH MONDAY/...
It will be turning noticeably colder Thursday as strong westerly
post-frontal flow directs cold air into the area.
A broad trough remaining over the Northeast U.S. on Friday will
push off the coast by the beginning of the weekend. A clipper
system associated with the final piece of shortwave energy
embedded in the trough may bring a mix of snow and rain Thursday
night into Friday with a light accumulation possible. The mean
500mb flow is fcst to flatten out a bit over the weekend with
temperatures moderating nicely to above average after bottoming
out on Friday. Overall, the pattern looks fairly quiet over the
weekend and into early next week with another strong frontal
system possible by March 7-8.
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --Low clouds gone from BFD, seem related to area of returns
on the radar that have lifted to the north and east.
Some fog now, mainly at BFD, as lack of clouds has allowed
some fog to form. Still some mid level clouds across the
12Z TAFS sent.
Earlier discussion below.
Most of the day will feature dry weather and VFR conditions.
Some showers and thunderstorms toward late afternoon will
be possible across the west, as the warm front lifts northward
across the area. Some restrictions in ceilings and visibilities
will be possible late (after 20z) for the western airfields.
Poor conditions for aviation will spread eastward this evening.
Warm front will move north of the area by Wednesday morning.
Winds will shift to the southwest on Wednesday. Strong to even
severe storms will be possible, as a cold front moves eastward
across the area during the afternoon and early evening hours.
Wed...Rain showers/Sub-VFR reductions. Breezy. LLWS likely.
Chance of thunderstorms.
Wed Night...Strong FROPA early with gusty winds/tstms.
Thu-Fri...Sub-VFR likely west in sct snow showers. NW winds. VFR
Sat...No sig wx.
-- End Changed Discussion --
With only one more day left in meteorological winter
(Dec+Jan+Feb), it seems that we are currently running as the
4th-warmest winter at both Harrisburg (tie) and Williamsport.
Today should be another above-normal day, which may push
Harrisburg up to 3rd place, and Williamsport may get nudged up
to a tie for or even an outright 3rd place.