Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 171141
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
741 AM EDT Wed Oct 17 2018

.SYNOPSIS...
A cold front will move through the state today, kicking up the
wind and reinforcing the chilly air. A coating of snow is
possible on the higher elevations of the northern Alleghenies
tonight. A widespread frost is possible Friday morning. It will
be mainly dry and much cooler than normal through the end of the
week as the center of a high pressure area drifts by just to
our south.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Earlier cloud deck went east and dissipated. Cold front appears
to be on the doorstep of KDTW. West wind already making lake
effect clouds and isold SHRA over wrn NY and just recently over
the middle of the lake. All is well. Made tweaks to timing of
sky cover changes and Near-term winds.

Prev...
Pretty clear over most of the CWA right now. But a jet streak
aloft is bringing some mid clouds or even higher-based low
clouds in across LE. The cold front is still back over central
lower MI, but is already generating low clouds and very isold
SHRA. All guid keeps the SHRA to the NW of Warren thru sunrise.
After which, the wind shifts as the front passes. The lift
generated will combine with the warm lake moisture and make
sct-nmrs SHRA. Most of the NW third of the area will get wet
today, but the sct nature/coverage of the showers precludes a
solid 100 PoP for much of the region. Will however keep mentions
of showers mainly to the NW of the Allegheny Front.

The wind is the bigger story today. It will get windy as the
pressure gradient gets very tight, about 8-10mb across the
state. The well-aligned west wind thru most of the atmosphere
will allow a high efficiency of mixing down the wind from the
middle to top of the well-mixed layer. The mixing heights today
will be up to 5-6kft over the srn 2/3rds of the region, and
max out around 3-4kft in the north. This should still allow for
gusts in the 30s and lower 40s (mph) - esp in the Laurels and
south-central mountains. Gusts will likely be into the 20s and
lower 30s on the ridges this morning, even before the front
passes and the flow becomes well-aligned vertically.

Despite the strong cold advection, temps should end up following
a rather usual diurnal curve. Perhaps only the NWrn counties
will see temps max out before 18Z. Expect maxes only in the m40s
in the NW and on the ridges of the Laurels. Helped by some
downsloping and much more sunshine, the Lower Susq Valley will
probably get to 55-60F.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
The showers off the lake keep on going through much of the
night, perhaps waning toward sunrise. The temp profiles look
cold enough for some snow to mix in during the evening in the
NW, but accumulations will wait until the ground gets cold
enough later tonight. The best/most intense showers may be
during the first half of the night, with generally less
coverage thru the second part of the night. But, it should get
cold enough, esp on the higher elevations of the NW to have some
of the white stuff stick by morning.

The wind keeps up at 10-20 mph with G15-30 for the first half
of the night, then diminishes a little more to generally 5-10mph
with gusts in the teens on the ridges. This will keep us well-
mixed for much of the night. Temps will fall off to some of the
coldest readings so far this autumn. The wind and the
possibility of stratus off the lake(s) reaching deep into the
CWA will make the min temp forecast for the SErn part of the
area tricky. Places still listed in the growing season (SE half)
should only dip into the m30s. There is a chance that some
places in the east (mainly Schuylkill Co) could get to freezing.
However, the threat does not appear to be great enough across
the entire county. Thus, we have held off on a freeze
watch/warning at this point. The wind tonight will likely result
in no frost formation. Thus, we could conceivably have a freeze
without a frost. The day shift will take one more stab at the
mins tonight.

Thursday looks fair, but still a little windy. The thermal
trough lifts off to the NE early in the day, ending the sct
shsn/flurries over the NW. The clouds should be gone for most of
the area during the morning, with the nrn tier waiting until
noon or slightly later. High pressure off to our SW will start
to shove milder air in aloft later in the day and overnight
Thursday night. But, the cold, dry air at the sfc will be tough
to displace. The sky will be clear Thur night, and the wind much
lighter than tonight. Thus, a widespread frost still looks
likely, with mins a deg or two colder than tonight over the
growing-area.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Friday looks mostly sunny as the high pressure passes to our
south. Occasional rain showers are likely Friday night in the
west and across all of the area early Saturday in advance of a
sharpening cold front poised to sweep across the Appalachians
Saturday evening. A more pronounced shot of cold air will follow
in the wake of the frontal passage, likely supporting a greater
coverage of snow showers/flurries across the Alleghenies
Saturday night through Sunday. Additional snow accumulation is
probable in the favored lake effect zones and upslope/higher
terrain. Wind chills in the low 30s to mid 40s on Sunday will
make it feel more like early December than late October.
Conditions should improve into Monday as high pressure migrates
eastward from the Mid MS Valley.

Below average temperatures are strongly favored to continue
next week and likely last through the end of the month.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
12Z TAFS sent.

Some low clds again at IPT.

Had 1500 foot ceiling at JST earlier, but gone now.

Big thing at JST is the gusty winds.

Speaking of winds, took LLWS out of the 06Z TAFS, as more of
an increase in wind speeds with height, but not the direction.

Rather strong cold front across the lower lakes at 5 AM, but
no real moisture to work with.

Expect some lower clds with the front, but mainly across the
north and west, and just for a brief time further east and
south, if at all.

.Outlook...

Thu-Fri...No sig wx expected.

Sat and Sunday...AM low cigs possible W Mtns Sat. Elsewhere
Scattered showers and areas of mainly MVFR CIGS as a cold front
pushes SE across the PA airfields. Then...SHSNRA/cig reductions
possible NW Mtns after dark Sat evening and through much
Sunday.

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Steinbugl
AVIATION...Martin


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