Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kctp 230542 
afdctp

Area forecast discussion
National Weather Service State College PA
142 am EDT Tue may 23 2017

Synopsis...
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 this morning/...
weak high pressure overspreading western and central PA late
this evening with partial clearing over central and western
areas. Clouds still slow to clear over the east...and earlier
thinking of 06z or afterwards still looks good for partial
clearing. Winds will be light as 1016 mb sfc high overspreads
the area...and mins will range from the lower 40s north to the
mid 50s southeast.

&&

Short term /6 am this morning through 6 PM Wednesday/...
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 /Wednesday 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 /06z Tuesday through Saturday/...
06z tafs sent.

A slow-moving cold front, located from just east of ipt to
around MDT at 03z, is dying out as it pushes into eastern PA
late this evening. West of the front, drier air has arrived and
confidence in VFR conditions through tonight is high. East of
the front, clearing skies, low dewpoint depressions and light
winds will result in areas of fog and low ceilings overnight across
eastern PA.

Any fog across eastern PA will burn off just after sunrise.
Most of the day will feature just some high clouds. Perhaps
some light rain late, but mainly south of the taf sites, based
on the airmass in place and guidance keeping most of the area
dry.

Wed morning may feature more fog and low clouds, given that
fcst lows are at or below fcst dewpoints, cross over
temperatures. Still time to look this over, as it would be
mainly after 06z. Another factor will be that the high clouds
could cut down on the cooling late Tuesday and early Wed.

Outlook...

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.

&&

Ctp watches/warnings/advisories...
none.

&&

$$

National Weather Service Glossary of Abbreviations