Scientific Forecaster Discussion
fxus61 kctp 190322
Area forecast discussion
National Weather Service State College PA
1122 PM EDT sun Aug 18 2019
it will remain very warm and humid into early this coming week
and a meandering trough of low pressure will keep the mention of
mainly afternoon and evening showers and thunderstorms in the
forecast. Cooler and much less humid air will arrive for
Thursday through Saturday with dry conditions expected.
Near term /until 6 am Monday morning/...
scattered, pulse-type convection rapidly diminishing in coverage
and intensity late this evening, as boundary cools. Expect this
trend to continue through around 06z, then will reintroduce the
chance of late night showers and possible tsra over the northwest
counties in association with a weakening cold front approaching
from the grt lks.
It will be another muggy overnight with lows ranging from the
mid 60s over the north to around 70f southeast. A light southerly
breeze should preclude widespread fog, but still expect patchy
fog where there was rain today, especially over the southeast
half of the state, where the pressure gradient is weakest.
Short term /6 am Monday morning through 6 PM Monday/...
dying cold front will slowly cross the state Monday. Any morning
showers along the front should be isolated and confined to the
northwest counties. However, diurnal heating of moist, pre-
frontal airmass will cause convection to become more widespread
by afternoon. Model soundings indicate deep layer shear will be
weak, so organized severe weather appears unlikely. However,
model CAPES support the potential of isolated damaging wind
gusts/large hail, mainly along and east of the susq river.
A hot and humid day is on tap with heat indices peaking near
100f across the lower susq valley. Model soundings indicate
Max temps will be similar to Sunday, with highs ranging from
the low 80s along the New York border to the lower 90s in the valleys
of southern PA. The combination of heat and humidity may warrant
the issuance of a heat advisory for a few hours Monday
Long term /Monday night through Sunday/...
made some very small changes to this part of the package, given
not a lot of change on guidance and storms on the radar.
A trend toward cooler and drier weather is expected for the
later part of the week, as a cold front moves east of the area.
Perhaps a shower toward the later part of the weekend.
More detail below.
Guidance continues to show a fairly vigorous upper trough
crossing the northeast quadrant of the lower 48 this period.
Within the upper trough, there are still smaller scale detail
differences that will affect progression/speed of the leading
surface cold front and will take more time to be resolved. The
cold front will be a focus for convection as it pushes southeast
Wed-Thu. While predictability is too low and limited at this
range, severe storm risk upgrades are possible into the short
Late-Summer heat episode continues into midweek with Max temperature
anomalies +5-10f above normal on Wednesday. At this time, expect
Thursday to be the transition day with a relative cooling trend and
push of drier air throttling temps back to near/slightly below avg.
Friday into the weekend. Lower humidity will spell pleasant days and
comfortably cool nights.
Aviation /03z Monday through Friday/...
for the late evening taf update, main change was to put some
showers in late tonight for bfd and jst.
This based on a weakening line of showers and storms over
western Ohio. Temperatures still quite warm out over OH, but
cooler over our area. Thus just went with showers instead of
storms, given time of night when they get into our area.
Earlier discussion below.
00z tafs sent.
Still a few showers and storms until late evening.
Given the type of airmass in place and the rapid warm up we have
seen the last 2 mornings, expect any fog and lower clouds to
only last a short time early Monday.
With no mid level wind Max moving across the lower Great Lakes
on Monday, showers and storms less likely than what we had
yesterday or today. Thus left fcst dry for Monday.
Tue-Wed...rounds of PM showers/thunderstorms. Late night and
early morning fog/low clouds.
Thu...trending VFR northwest; chance of T-storms southeast.
Frontal passage Thursday night.
Fri...no sig wx.
record Max temperatures for August 19:
Harrisburg 97 in 1966
Williamsport 94 in 1899
Altoona 91 in 1983
Bradford 86 in 1978
State College 96 in 1899