Scientific Forecaster Discussion
fxus61 kctp 162003
Area forecast discussion
National Weather Service State College PA
403 PM EDT Mon Sep 16 2019
a weak area of low pressure and cold frontal boundary will move
south of the commonwealth early tonight. High pressure will
build in from the north and bring a very long stretch of dry
Near term /until 6 am Tuesday morning/...
low pressure over ncent PA at 18z has a quasi-stationary
extending east-southeast to the Lehigh Valley with a trailing cfront across
the Laurel Highlands and greater Pittsburgh area.
Limited llvl moisture and weak convergence and a few-svrl deg c
of mid level warm advection from the west was keeping any
showers to a minimum across the region, and that should change
little through this evening.
Have trimmed pops back to mainly the isolated-sctd categories
with quantitative precipitation forecast a few hundredths of an inch at most.
Cooler llvl air advecting in from the northwest then north-northeast overnight will
maintain bkn strato cu for at least the first half of the
night, then some clearing later on.
Any clearing up north, combine with light wind and much cooler
temps, will lead to locally dense fog in the deeper valleys
containing rivers and larger streams.
The front should be south of the state around sunset, but
isolated light showers could linger for much of the night over
the south. The clearing expected across the north will lead to
temps getting down into the 40s and the requisite fog in the
valleys of the north.
Mins will be mainly in the 50s elsewhere, though some locations
along the PA/Maryland border may north dip below 60f considering the
amount of clouds (bkn-ovc, high-based strato cu and altocu)
Short term /6 am Tuesday morning through 6 PM Tuesday/...
the fog could linger into the middle of the morning in the
deeper valleys of northern PA. Overall, though, it will be a
dry, mostly sunny to sunny day. Dewpoints will be in the 40s and
lower 50s. Maxes in the u60s- m70s will be spot on normal.
The next weather system will be a large upper level trough
that will move through southern Canada and drag a front across
the Great Lakes and through the mid Atlantic region early next
week. Timing still varies on this system and the long range
models diverge on a solution. So have left broad pops up through
Monday and Tuesday. That system as of now looks to be the next
best chance for precipitation.
Long term /Tuesday night through Monday/...
A large upper level ridge will build over the Great Lakes which
will dominate the weather pattern through the week. This should
keep central PA dry through the week, perhaps until Sunday.
Temperatures near normal at first should rise well above normal
as the ridge pumps up and slides eastward a little.
Aviation /20z Monday through Saturday/...
a weak area of low pressure and associated frontal system will
support bkn-ovc, mid-level cloudiness (vfr) across much of
central PA for the rest of today through early tonight.
Isolated, to at most scattered light rain showers will drift
from northwest to southeast across the southern airfields of PA
through 03z Tuesday.
Post-frontal, low level moisture combined with orographic lift
is likely to result in MVFR cigs during the late afternoon and
early nighttime hours across the northern mountains.
Tue-Fri...am valley fog possible central/northern PA, otherwise
no significant weather expected.