Area Forecast Discussion
Issued by NWS State College, PA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 220630
Area Forecast Discussion
National Weather Service State College PA
230 AM EDT Sat Apr 22 2017
A stalled frontal system just to the south of the Commonwealth
will keep the region flirting with clouds and precipitation
into the weekend.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Meso anal shows northerly winds finally establishing across the
entire CWA as the surface low over the Mid Atlantic settled
The rest of the overnight should remain dry with clouds
returning from the southwest. Overnight lows in the 30s and 40s
will average near normal over the north, and some 5-10 warmer
than normal over the south.
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
Latest HRRR is very aggressive returning the rain into the
southern half of my CWA during the hours just after sunrise, and
continuing well into the afternoon hours. I adjusted POPs up a
bit to cover this, but I suspect they are still underdone. From
about I-80 south it could be a rather chilly and wet Saturday
with the driest weather indicated over the northern tier.
Highs will average in the 50s, or some 5-10 deg cooler than
normal for a change.
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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 /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --Biggest concern during the predawn hours is the possibility of
fog at LNS, where 06Z dewpoint depression stands at just 1F. A
few breaks in the overcast could result in enough radiational
cooling there to produce IFR visibilities between 07Z-09z. After
09Z, the arrival of drier air in the low levels, combined with
increasing mid level cloudiness should result in a diminishing
threat of low visibility. Elsewhere, no significant reductions
expected this morning. Radar loop at 06Z does show an area of
rain showers approaching from Ohio associated with an upper
level disturbance. These showers will affect parts of central
and southern Pa later this morning, but there should be enough
dry air in the low levels to preclude significant CIG/VIS
Any showers should exit southeast Pa by early afternoon. After
that, a drier northerly flow should ensure widespread VFR
conditions for the rest of the day through this evening.
Sun-Mon...No sig wx expected.
Tue...Rain/low CIGs possible.
Wed...AM Rain/low CIGs possible, mainly eastern Pa.
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NEAR TERM...La Corte