Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 300551
Area Forecast Discussion
National Weather Service State College PA
151 AM EDT Thu Mar 30 2017
High pressure will provide dry weather tonight and early
Thursday. A storm system will approach the region from the Ohio
Valley on Thursday, bringing showery conditions Thursday night
through Saturday. A warm up is then in store over the weekend.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Adjusted sky grids for current sateliite trends. Stratocu
streets in NE PA is diminishing with the sun setting. Otherwise
just a few cirrus patches moving across. High clouds are
expected to increase overnight from the west. Lower Susq should
remain mostly clear tonight with clouds getting in there
Thursday morning. NW mountains may see some lower clouds toward
sunrise and an isolated light shower is possible. Temperatures
this evening are nicely hanging in there in the 50s and upper
40s. Made adjustments to the hourly grids. Speed of clouds
rolling in will effect the morning mins. Wind should die down
tonight. High clouds will slowly increase tonight.
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
Clouds lower and thicken through the morning. While a few
sprinkles are possible in the morning in the west, it is dry
under the clouds.
Evaporational/dynamic cooling of the airmass *may* help 925-850
mb temps dip to near 0C right as the precip starts across the
area Thursday afternoon/evening and Friday. The QPF is really
minimal during that brief time, so I will not mention it in the
wx grids for now. However, I do expect a pellet or two of sleet
or a flake of snow at the beginning of the warm advective
precip. Temps will be well above freezing during that time, and
column temp profile then rise to entirely above freezing. At the
worst a very thin coating of frozen stuff may occur on the
grass in the far NE miles of the CWA. Ground/road temps very
warm, now. Not expecting any problems.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Model consensus is also for a quasi Miller-B type of low track
heading just north of the Ohio River during the day Friday, then
a pressure jump and slight intensification of the sfc low (to
996 mb) off the southern NJ and New England Coast Saturday.
Under normally colder winter-time circumstances, this low track
would be pretty favorable for a significant snowfall across
much of central and northern PA. However, a quite warm boundary
layer (and 850 mb temps) to begin with, coupled with the lack
of a stronger anchoring high over southeast Canada and New
England will mean a widespread/soaking rain evening with 24-36
hour rainfall at the majority of places here in Central PA
coming in between 0.75-1.00 inch.
This rainfall will add a healthy spike to the flow and levels on
smaller streams and creeks across the region with broader mdt
rises on rivers, but no significant threat for flooding as
headwater flash flood guidance is averaging 2-2.5 inches for a
12 and 24 hour period respectively.
Periods of light rain, drizzle, and ridge shrouding dense fog
will persist Friday night into Saturday as slightly colder air
wraps around behind the storm. Some breaks in the cloud cover
should occur Saturday afternoon, esp across the Lower Susq
Valley where drying downslope flow will be enhanced. Forecast
temps Friday may be a bit warm considering the aforementioned
storm track just to our south, and amount of rain expected.
Max temps Saturday will near to a few deg F above normal in
High pressure building over the region (coupled with the
offsetting effect of abundant sunshine and GEFS mean 850 mb
temps cooling by 3-4 deg C imply max temps close to what we`ll
see Saturday, which is upper 40s to lower 50s across the nrn
mtns...and mid to upper 50s elsewhere. Dry and slightly milder
conditions are in the forecast for Monday as the ridge of high
pressure slides just to our east and ens mean 850 mb temps
rebound by a few to svrl deg C (atop a light serly sfc flow).
The next, rather potent and moisture laden southern stream wave
heads our way for Mon night and Tuesday, bringing a likelihood
of a widespread rain. Next Wednesday looks dry in the wake of
the early weak system with temps rising above normal.
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
06Z TAFS sent.
Some mid level clouds moving toward the northwest as of
Earlier discussion below.
VFR conditions will continue overnight and most of today, with
increasing high-to-mid level clouds/cigs. In the far west,
showers become likely KBFD / possible (JST) by noon, and the
cigs do lower rapidly during the day in much of the rest of the
area. Expect one wave of warm advection rainfall in the
afternoon and evening rolling through from SW-NE - and impacting
mainly the NW half of CWA. There may even be a few sleet
pellets or snow flakes mix in right at the very beginning of the
precip in the north. Temps will be much too warm to have this
make any kind of trouble on the ground.
Wind will be light/variable overnight, and increase over the
west later in the morning as the high pressure overhead
currently slides to the E/NE and S/SW flow increases.
Conditions go downhill Thursday evening and sub-VFR conditions
in rain showers and lowered cigs then persist into Friday
Sat: Sub-VFR restrictions early; then gradually improving
conditions into Sat night.
Sun-Mon: VFR/No sig wx.