Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 182317
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
717 PM EDT Wed Oct 18 2017

.SYNOPSIS...
For the most part our weather will be dominated by a surface
high and an upper-level ridge through late Sunday. A weak
short-wave comes over the ridge on Thursday without significant
moisture. Our first real chance of rain will be early next week
when a trough moves our way. By mid-week we could see some below
normal temperatures with a deep trough just to our west.

&&

.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
Temps now down to about normal maxes for today. Little change to
the grids with little weather to speak of. Mins may near frosty
levels in the Mid Susq and THV, but it will again be too spotty
to warrant an advisory.

Prev...
High pressure over us is weakening due to a wave in the northern
stream. But the dry air is still in place so it is an
outstanding day. Though I appear to be indoors.

Used the blends which in some locations are a tad low for highs.

Overnight another nice night the winds may increase above the
PBL as the high retreats due to the wave. This will limit fog a
bit more than early this AM. And there was not a lot of fog this
AM. Nice overnight lows mainly 40s except for a few colder
spots in rural areas to the south. Less wind south as high
retreats.

&&

.SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Warm air, with maximum temperatures 5 to 10 degrees above
normal, will continue through the weekend. A weak wave will
push a front into our region. However the very weak front will
be dry as the moisture starved system is coming into a dry air
mass. Expect a bit more wind than today with the weak frontal
surge. Rain chances through the weekend are near zero. The high
pressure that will dominate the pattern through the weekend will
finally shift off early next week. This will be a two pronged
system with precipitation chances Monday through Wednesday. The
best influx of moisture will be Tuesday as the long range
guidance has the trough deepening over the Great Lakes region.
Precipitation should continue into Wednesday. Cold air behind
the low will finally filter down into the region through the
latter half of next week with 850 mb temps around 0C Wednesday
night. So expect temperatures to be back to around and slightly
below normal for this time of year next week.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A strong upper level ridge of high pressure will support above
average temperatures through the weekend. This will further add
to the anomalous October warmth which should help to secure a
spot in the top-10 warmest Octobers - if not top 5 or even #1.
Both GFS and ECMWF ensemble systems continue to indicate a
pattern flip by the middle of next week with a period of colder
(near/below normal) temperatures starting around October 25th.
The depth and longevity of the emerging upper trough and
subsequent cooler pattern remains in question - so we will have
to wait and see how much of a dent it can put in the strongly
positive month-to-date departures from climatology.

On the precipitation side, the prolonged dry spell ends early
next week as a cold front moves across the Appalachians. Stream
separation differences/closed low development in some of the
deterministic models leads to increasing spread and thus
uncertainty in the forecast details such as timing. The GOM will
be open for moisture inflow northward ahead of the front. So
will keep continuity and favor max POPs in the Monday night-
early Tuesday timeframe.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
No big changes to 21Z TAFS.

Nice fall afternoon outside with no clouds.

Comms failure at AOO just occurred.

Earlier discussion below.

The overall period from this afternoon through Sunday looks like
nearly ideal flying weather.

High pressure weakens as a wave comes by Thursday. Then high
pressure builds back in Friday-Sunday. So light winds most of
the time and few clouds to talk about.

As the high builds in this weekend we could see an uptick in
valley fog and fog over rivers and streams.

Looks like the rain should hold off until early next week.

Fly on!

Outlook...

Wed-Thu...No sig wx expected.

Fri-Sun...Mainly VFR, with just some patchy AM valley fog.

&&

.CLIMATE...
Month-to-date, October 2017 is the warmest October on record at
Harrisburg and Williamsport.

&&

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

&&

$$
SYNOPSIS...Grumm
NEAR TERM...Grumm/Dangelo
SHORT TERM...Grumm
LONG TERM...Ceru/Steinbugl
AVIATION...Grumm/Martin
CLIMATE...


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