Scientific Forecaster Discussion
fxus61 kctp 222357
Area forecast discussion
National Weather Service State College PA
757 PM EDT Mon may 22 2017
a cold front will push to the east of central PA this evening.
High pressure then builds in. However, a storm moving up the
East Coast and could brush southeastern PA with a little rain
on Tuesday. It will then be rather unsettled with many chances
for rain through the rest of the week. Temperatures will be
fairly close to normals.
Near term /until 6 am Tuesday morning/...
precip has finally exited the east and winds have now gone
light. Skies will partially clear across the central mountains
while the northwest becomes mostly clear by late evening. Clouds
will hang the longest over the east/southeast...at least until
06z before much improvement. Mins will range from the lower 40s
north to the mid 50s southeast.
Short term /6 am Tuesday morning through 6 PM Tuesday/...
major trend is toward a lower chc of rain in the southeast on Tuesday.
The NAM is very dry and the wet (a few hundreths) GFS and ec
keep any precip to the S of the Turnpike. We will start to
weight the forecast toward less clouds and less chc of precip on
tues. Maxes will actually have a chance to overachieve on tues
with lots of sun in the northern and central counties. 70s
widespread with m70s in the north.
Long term /Tuesday night through Monday/...
trough for Tue night positioned further to the west (over Iowa/mo)
in latest guidance, which will delay approach of surface low
pressure area and keep trend of mainly dry conditions in
central PA for Tuesday night and Wed morning.
But unsettled weather is on the way. Potent shortwave slides
through the trough for Wed, as surface low deepens over the Ohio
Valley. With sharpening trough working eastward, low and
occluding front will lift across PA Wed night and Thursday
bringing periods of rain/showers and chance for an embedded
thunderstorm in an otherwise dreary day.
By Friday, the low lifts to our NE as trough axis lifts through.
Though the day should bring gradual improvement in the weather,
highs Fri could end up several degrees below current guidance in
cold air advection northwest flow, a thicker low-level cloud deck and potential for
light showers/drizzle - esp northwest half of County Warning Area.
Sat should bring a return of brighter skies, albeit briefly,
and may end up being the nicest day of the long weekend as weak
ridge propagates through. Clouds will already be on the
increase Sat afternoon and persist into sun and Mon as a warm
front develops over the Ohio Valley (with low pressure gradually
organizing over the midwest). Proximity of this frontal
boundary along with deepening trough over the western Great
Lakes will bring potential for showers sun and Mon. Plenty of
uncertainty in strength/placement of main weather features
across model guidance during this time however, so forecast
details remain somewhat elusive for late weekend.
Aviation /00z Tuesday through Saturday/...
a slow moving cold front, located just west of ipt and thv at
00z, is pushing through central PA this evening. West of the
front, drier air has arrived and confidence in VFR conditions
through tonight is high. East of the front, stratus with cigs
around 1kft cover much of eastern PA at 00z. Models indicate
the front will eventually clear the entire forecast area by
around midnight. However, radiational cooling, combined already
low dewpoint depressions and light wind, will likely yield areas
of late night fog across southeast PA late tonight. Near term
model data suggest ipt will likely see a strong enough push of
drier air this evening to preclude significant fog issues
overnight. However, lns appears likely to experience IFR
conditions overnight and MDT is in between with about a 50/50
pct chance of fog later tonight.
Any fog across eastern PA will burn off around or shortly after
12z, with a high confidence forecast of VFR conditions across
most of central PA for the rest of the day. The only tricky
part to the forecast is the possibility of very light rain,
perhaps not even reducing the cigs below VFR, over the southern
tier of the state. Would estimate about a 20 pct chance of late
day MVFR cigs at the southern airfields, including jst,aoo,MDT
Wed...evening rain/low cigs possible, esp jst/aoo.
Thu...rain/low cigs likely.
Fri...showers/MVFR cigs northwest. VFR southeast.
Sat...no sig wx expected.