623
FXUS61 KCTP 121937
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
337 PM EDT Thu Sep 12 2024

.SYNOPSIS...
* The stretch of pleasant and dry weather will continue through
  the upcoming weekend with above normal average temperatures
  for mid September
* No impacts are expected from Francine that will meander slowly
  north across the Lower Miss and Tennessee Valleys over the
  next few days.
* The chance of rain will increase by the middle of next week

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1026 MB sfc high pressure just east of the new England Coast
will have its ridge extending SWWD across our CWA later this
afternoon and tonight. This dominant weather feature will
will provide abundant sunshine with just scattered, flat,
high-based cu across the Central Ridge and Valley Region of the
state with SKC elsewhere. Some thin cirrus will brush the
southern tier counties of PA late today and tonight.

Mid afternoon temps ranging from the mid and upper 70s across
the higher terrain of Northern and Western PA to the low and
mid 80s in the Central and Southern Valleys were several deg F
above normal in the valley, to nearly 10 deg F above normal
above normal over the NW Mtns.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Maintained persistence with respect to the increase in sky
cover in the S for tonight as low clouds may get up in there,
more so than this Thurs AM. Also mentioned areas of Dense Valley
F throughout the W Branch Valleys of the Susq and some of its
tribs (mainly in the 10-13Z Friday period). Lighter valley fog
AOA 1/2SM should occur in most other valleys of of Central and
Northern PA for a short few hour window during the mid morning
hours Friday.

Maybe a little less of a chc for fog in the S as we start to
have high/cirrus blow in from Francine.

Lows early Friday will dip to around 50F in the perennial cold
spots across the Northern Mtns and range through the low to mid
50s elsewhere.

The HRRR Smoke model also continues to show an increase in
vertically integrated smoke, which will make skies look more
hazy/milky by Friday.

Almost a carbon copy of today w/respect to high temps Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Medium range guidance supports a high confidence of warm and dry
weather this weekend into early next week associated with
persistent upper ridging. Abundant sunshine and ensemble mean
850mb temps in the 14-15C range support highs in the upper 70s
to mid 80s. However, surface ridging and associated dry air
should result in decent radiational cooling each night, with min
temps near seasonal levels. Although the air will be dry, patchy
river valley fog remains possible each morning.

As the remnants of Francine over the Mississippi Valley run into
building high pressure over the Northeast US late Sat into Sun,
its forward motion will slow significantly. Maybe a little less
of a chc for fog in the S as we start to have high/cirrus blow
in from Francine. range guidance shows the associated midlevel
low opening into a trough extending from the Mississippi Valley
to the waters off the Southeast US. Subsequently, a developing
coastal low off the South Carolina coastline becomes the
dominant feature later Sunday into Monday. Although the coastal
low will start off non- tropical, the NHC gives it a 30 pct
chance of becoming tropical or subtropical early next week. As
the high over the Northeast US pushes east late Tue into Wed,
this will ultimately allow the coastal low to drift westward and
northward, with the potential for a period of unsettled weather
in central PA from Tue PM / Wednesday through the end of the
week. The range of uncertainty remains large regarding rainfall
amounts, between some solutions missing central PA, and others
bringing over an inch of rain.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR conditions (100 percent confidence) will continue through
at least 06Z Friday with sustained light S/SE`ly winds topping
out near 5KTS this afternoon.

After 06Z Friday, valley fog potential will once again become
the main concern aviation-wise into early Friday morning with
lower cloud decks potentially bringing some concerns across the
southern tier. At this time, have mentions of a SCT deck 2-4kft
AGL across the southern airfields (LNS/MDT/AOO/JST) after 10Z
Friday although slightly lower confidence (~40%) on timing of
lower clouds working their way into the airfields.

The 18Z TAF package also makes mention of some lowered
visibilities at airfields with higher confidence (30-40%) on
valley fog restrictions (BFD/UNV) although exact timing and
magnitude of restrictions are less certain at this time.

The fog will likely become dense in the West Branch Valleys of
the Susquehanna and its larger tribs between 10-13Z (confidence
around 70 percent).

Afterward, its back to VFR in all areas after 14Z Friday.

Outlook...

Fri-Mon...AM valley fog north & central; otherwise, no sig wx.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Lambert/Steinbugl
NEAR TERM...Lambert/Dangelo
SHORT TERM...Lambert/Dangelo
LONG TERM...Fitzgerald/Colbert
AVIATION...Lambert/NPB