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000
FXUS61 KCTP 182031
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
431 PM EDT Fri Aug 18 2017

.SYNOPSIS...
A cold front will move through late today. An upper trough will
move across the area on Saturday. Temperatures will stay above
normal but rise even higher each day through Tuesday as a ridge
builds aloft. Another cold front should trigger showers around
mid-week and the week should end on a cooler note.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Radar shows the line of showers and thunderstorms pushing across
Lancaster county. Only a few isolated showers behind the line.
GOES-16 shows another nice area of cool stable air near the NY
border behind the showers which moved across the northern tier.

Based on HRRR and radar the watch for the southeast has a
shorter shelf life than advertised. We may drop soon. Enhanced
words in zones and grids reflect the watch in the southeast.

Most areas will see steady improvement this evening to include a
lowering of the dew points! Enjoy!

Some patchy fog will develop after mid-night.
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&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...

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Minor update with new data focusing showers in the afternoon.
No other significant changes.

Previous: The high pressure moving in finally clears everyone
out in the morning. Any low clouds in the NW will dissipate
nicely with the sunshine. The trouble there is that the
lingering moisture, the passage of the upper trough and
enhancement from a potent short wave coming around the base will
meet up at peak heating. These factors and the wind field will
generate multiple showers in the NW half of the area in the
aftn. Some of these will make some good gusts - and some could
get severe. A little small hail is also possible with colder air
aloft than today. SPC does have that area in a MRGL risk for
severe wx. The showers/storms will struggle to get past the
Allegheny Front (roughly IPT-UNV- AOO line). Max temps will be
right near normals.
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&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
The mid range models are all in good agreement on the timing and
strength of the passing shortwave Saturday night. Once that
passes, the heights will rise and become quasi-zonal. This will
bring fair weather to the region Sunday through Tuesday. Dry
westerly flow will also bring warm summertime temperatures with
Tuesday continually trending warmer. A new shortwave moving
through SRN Canada will an bring an increasing chance for rain,
possibly as early as Tuesday afternoon over western sections of
the forecast area.

There are differences in timing of the rain with the ECMWF
suggesting it holds off until Tuesday night. Blended MOS POPs
show a small chance of showers moving into western sections
Tuesday afternoon, but the highest POPs are reserved for the
overnight.

Cyclonic flow aloft will then dominate the flow pattern through
Thursday. The cool air aloft will help trigger a few mainly
diurnal showers Wednesday and Thursday. The showers will tend to
favor northern and western higher elevations. Temperatures will
be significantly cooler for the second half of the week.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
Storms all over the radar scope at 19z SE of UNV-IPT-AOO. Just a
spot of showers in the N east of BFD. That spot is probably
along the real cold front as there are lower dewpoints
immediately to the west of it. Additional storms are possible
in the west and central counties late this aftn, but most
locations will remain dry and VFR.

A final push of drier air will move through this evening and
early tonight. Thus, a few shra are possible in BFD between 23z
and 02z - but the other terminals should stay dry this evening
and tonight. Fog is possible for most of the area tonight, but
more so in the SE where it has rained and had clearing, but
little time to dry. Lower clouds should form over the NW mtns
tonight, but these should stop around the old AOO-UNV-IPT line.

An upper level trough and rather strong forcing passing
directly overhead in the cooler air aloft could make sct
shra/tsra across the northern third/half of PA on Sat aftn.

Much drier air will make for a mainly-VFR Sun-Mon with only
valley fog in the AM a potential issue.

.OUTLOOK...

Mon...No sig wx.

Tue-Wed...SHRA/TSRA poss.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Grumm/Dangelo
SHORT TERM...Grumm/Dangelo
LONG TERM...La Corte/Ceru
AVIATION...Dangelo