Area Forecast Discussion
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FXUS61 KCTP 220950
Area Forecast Discussion
National Weather Service State College PA
550 AM EDT Sat Apr 22 2017
A front stalled just to the south of the state. An upper
level cut off low will form over the Tennessee Valley late this
weekend, and could end up bringing a storm up the East Coast in
the first part of next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Radar mosaic shows a good shot of rain moving through central OH
at this time, and it is headed right for the region. The forcing
for the rain is a low level jet poking up into the OH Valley.
This feature will slide to the east and into PA this morning.
The lower atmosphere should moisten up and it should rain in
the west before sunrise and light rain will likely fall in the
central zones during the morning hours. Showers in VA are also
be headed into the southeast. Timing and intensity of the rain
for this morning is much as the NAM has been painting it for the
last 24+ hrs. The precip should have dissipated and moved
slightly to the south for the afternoon. Thus, have confined
POPs to mainly the south of the turnpike. The day in State
College will likely start cloudy and rainy (which may make you
feel Blue), but things should get brighter and dry up by lunch
time (which may turn your frown to a bright, White smile).
Any rain in the south should press to the south late in the day.
Maxes will be kept down by a good bit of cold advection through
the daylight hours, and the clouds and any showers. Temps will
only get near 50F in the higher elevations. We may touch 60F in
a few spots - with the best chance for that probably in the EC
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Rain is expected to press to the south of the state very early
this evening. It should remain dry - even in the south - for the
rest of the weekend. Temps will get pretty chilly Sunday
morning, especially in the mountains. Much of the area will be
into the U30s and L40s. However, it will probably get below
freezing in the mountains - most of the NW third to half of the
CWA. Wind will be calm or light/northerly. Much of the area will
clear out. The average date of the last spring freeze has
passed for the SE third of the area, and there could be some
frost in the ridge and valley region (between UNV and MDT). Will
hold off on any mentions of frost in the wx grids/zones for
Subsidence will lead to plentiful sunshine on Sunday. Temps
should rebound nicely with almost all of the area back into the
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
There is a better-than-normal agreement between the models on
timing and positioning of the cut-off low ref`d below. Rain will
likely spread up the coast and into the area Monday into
Tuesday, but may not make the western counties wet at all. Have
bumped POPs up 10-20pct over the eastern half for that period.
The period of Sunday to Wednesday will be dominated by the flow
around a slow moving cut-off low which eventually will pass to
our south and east. This system will bring clouds and light rain
to the parts of our region for several days. Once this system
goes by large scale retrogression will put our region on the
western edge of a relatively strong 500 hPa ridge and it will
get warm fast. It should feel like summer by next Thursday.
Sunday weak high pressure and low moisture values should provide
for a relatively nice day. We will be well north of the frontal
Monday the low to our south begins its slow journey towards
the Carolina coast. Our PW values come up and the threat of QPF
in the GEFS/SREF and CMCE show increased chance of light rain
overnight Sunday into Monday. Best chance of rain should be in
southeastern PA. The potential for rain will be higher in
southeastern PA and much lower in northwestern PA. Rainfall will
likely be very light and the best chance for measurable
rainfall will in southeastern PA. Enjoy the mostly cloudy and
relatively cool weather while it lasts.
As the 500 hPa low fills and the attendant moves to our
northeast the chance of rain should fall off Wednesday into
Wednesday evening. Our 850 hPa temperatures will rise rapidly
Wednesday and it should be noticeably warmer Wednesday relative
to Monday and Tuesday.
Thursday into Saturday the 850 hPa temperatures will be well
above normal, mainly in the 14 to 16C range and we will be on
the western edge of a rather impressive early season subtropical
ridge. The GEFS and GEFSBC show a closed 5880 m ridge along the
VA/NC/SC coast with +2 sigma height anomalies by Fri-Sat.
Thus Thursday through at least Saturday should be very warm and
humid. We should have several days with high temperatures well
into the 80s. Any precipitation after Wednesday will likely be
in a more summer-like atmosphere so added thunder in all
forecasts beyond Wednesday.
The ridge will likely continue retrograding. If the NEAFSBC and
GEFSBC are correct we could be looking at our first enduring
period of warm weather from this coming thursday into the
.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
Radar loop at 0930Z showing an area of showers moving through
central Pa associated with passage of an upper level
disturbance. These showers will affect parts of central and
southern Pa this morning and into the afternoon over the
southeast, but there should be enough dry air in the low levels
to preclude significant CIG/VIS reductions. No worse than MVFR
CIGs expected, mainly at BFD, JST and LNS this morning.
Any showers should exit southeast Pa by early evening. After
that, a drier northerly flow should ensure widespread VFR
Sun-Mon...No sig wx expected.
Tue...Rain/low CIGs possible.
Wed...AM Rain/low CIGs possible, mainly eastern Pa.