Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 250808
Area Forecast Discussion
National Weather Service State College PA
408 AM EDT Sun Sep 25 2016
A large area of high pressure near James Bay Canada will drift
south and become centered over the northeastern US Sunday. Expect
fair weather with warm days and cool nights through the rest of
this weekend. A cold front will push through the region late
Monday and Monday night. Dry weather will return for the rest of
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Skies are clear and winds are light, setting the stage for a night
of efficient radiational cooling. A true taste of autumn will be
in the air tonight as temps drop off into the mid to upper 30s in
the northern mountains, and 40s elsewhere. Expect patchy frost
throughout the rural valleys of the north and normal cold spots.
With the recent prolonged period of very much above normal
temperatures, this will be quite a shock to some.
Light north winds tonight will become light and variable in the
deeper valleys. This light wind combined with clear skies and a
greater than 20 deg air/water temperature difference will likely
lead to development of fog that could become locally dense. The
cold air draining into the river valleys will then set up a battle
between the river valley fog and frost. These two phenomena are
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Sunday should be stellar with low dewpoints, spectacular
visibility, and just a few clouds after the valley fog lifts.
After the chilly start, temperatures will rebound to around
Some high clouds will slide down from the NW Sunday night. These
could have just a minor effect on temps. Guidance says that it
should be quite a bit milder in the west Sunday night vs. Sat
night. Will stay close to these numbers.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Clouds increase Monday ahead of significant cold front headed our
way. Recent guidance continues to speed up the timing of the
front. Have adjusted things accordingly and split up the wx grids.
This then puts the timing of showers during the afternoon/evening
in the west. Showers should be out ahead, however given the
instability, diurnal heating have put in thunder possible with
this timing. Certainty of rainfall for most of the area has
climbed into the 60-70pct range. This will be much needed
rainfall, with highest amounts Monday Night. Based on latest data
have increased QPF amounts, especially where thunder is possible.
The front should be through by Tuesday morning. Will linger only
chc POPs in the far SE and keep them in the far NW for lake-
effect and/or cool air aloft instability showers for mid- week.
Temps should stay very normal for the balance of the week, though
cooler. There will be another extended period of dryness.
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --Clear skies and light wind across central PA overnight as high
pressure builds into the state. Don`t expect extensive fog
development this morning given the dryness of air mass. However,
cool temps and relatively warm river/stream water should result in
some fog late tonight in the deep valleys of north central Pa.
Looks doubtful that any airfields will be affected, but can`t
rule out a brief vis reduction at KBFD or KIPT with even less
confidence at KUNV.
Sunday...High confidence in widespread VFR after 14Z, which will
continue through Sunday night.
Mon...PM showers/Tstms with reductions possible.
Tue-Thu...No sig wx expected.
-- End Changed Discussion --
Near Term...La Corte