Scientific Forecaster Discussion
fxus61 kctp 192029
Area forecast discussion
National Weather Service State College PA
329 PM EST Tue Nov 19 2019
some patchy drizzle or freezing drizzle may occur later tonight,
over the Allegheny ridges and northern mountains of the
commonwealth. Otherwise, weak high pressure will bring dry and
seasonable weather from Wednesday into early Thursday. Our next
chance of rain will come later Thursday and Thursday night,
associated with an approaching cold front.
Near term /until 6 am Wednesday morning/...
215 PM update... stubborn low cloudiness continues to slowly
erode at this time over far northern and western portions of the
commonwealth, while much of central PA has broken into sunshine.
Tonight into Wednesday, as surface low pressure slowly gains
strength well offshore and a surface ridge drops into the Ohio
Valley, a tightened pressure gradient will lead to increased
west-northwest flow in the lower levels of the atmosphere. As this occurs,
some lake enhancement off Erie is expected in northwest PA and upslope
conditions will occur along the Allegheny ridges, with the
potential for some light, spotty precipitation late at night
into the early morning Wednesday. Sounding profiles support
mainly drizzle/freezing drizzle, with insufficient saturation
depths to support ice production in the cloud layer. At this
time, uncertain development and spotty coverage precludes the
issuance of an advisory, but we will mention the potential for
patchy freezing drizzle in our hazardous weather outlook.
Elsewhere tonight, clear-partly cloudy skies this evening, will
go partly-mostly cloudy late at night, especially over the
central and south-central mountains. Lows by daybreak will range
from the upper 20s in the northern mountains to the mid 30s in
the lower Susquehanna valley.
Short term /6 am Wednesday morning through 6 PM Wednesday/...
230 PM update... outside of the northern mountains and the
Allegheny Highlands, where clouds will remain stubborn within a
northwest flow regime, early clouds should generally give way to
partly-mostly sunny skies. Afternoon highs should range in the
40s for most of central PA, with some upper 30s in the northern
mountains, and some near 50 degree readings in the lower
Long term /Wednesday night through Monday/...
surface high pressure will slide south of the area Wed night
into thurs, with a southerly flow developing. This will draw
slightly milder air into the area, with highs Thursday
approaching or topping 50 degrees for many locations south of
the Route 322 corridor. Clouds will increase through the day
ahead of a cold front approaching from the Midwest, with rain
showers developing across western PA late in the day.
The cold front will bring increasing pops across the western
half of PA Thursday night. The front will continue eastward
across the commonwealth on Friday, with a continued chance of
showers. As chillier air returns, some wet snowflakes may mix
in across northern PA.
After partial clearing and a lull in the precipitation Friday
night, moisture will return northward on Saturday as low
pressure slides northeastward from the Tennessee Valley towards
the mid-Atlantic region. The operational models have come into
better agreement over the past 24 hours, and show a secondary
area of low pressure developing over southeast Virginia or the Delmarva Sat
night, before becoming the dominant system and pulling out to
sea on Sunday.
Temperatures will be chilly, and some uncertainty remains for
precip type. For now, went with light rain or a light wintry
mix developing from south to north on Saturday before going
over to plain rain for much of the area as the day progresses.
The precip may change back to a period of snow showers Saturday
night before pulling east of the area on Sunday. After a chilly
day on Sunday, temperatures look like they will rebound heading
into early next week.
Aviation /20z Tuesday through Sunday/...
18z update... residual stratus clouds may continue restrictions
for a brief time early this afternoon at kbfd and kipt.
Otherwise, VFR/unrestricted conditions are anticipated for the
balance of the afternoon.
Tonight, as west-northwest winds begin to increase just off the deck,
lower clouds will thicken up again rather quickly at kbfd and
kjst, due mainly to upslope conditions and/or lake enhancement.
At both sites, IFR conditions appear likely after 03-05z.
Elsewhere, other than potentially a brief period of MVFR close
to daybreak, VFR should continue.
Wednesday, a gradual improvement in conditions is expected
through the morning at kjst and kbfd, as low ceiling bases
slowly lift. Otherwise, look for generally VFR to continue.
Surface winds out of the west at close to 5 kt is expected through
much of tonight, then they'll pick up out of the northwest Wednesday at
around 10 kt.
Thu...patchy am fog possible.
Fri...am low cigs/showers possible, especially west mtns.
Sat...rain/low cigs possible.
Sun...possible lower clouds for a time, again especially west mtns.