324
FXUS61 KCTP 061452
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1052 AM EDT Sun Oct 6 2024

.SYNOPSIS...
* Today will be another warm day for early October.
* A strong cold front will be accompanied by a broken line of
  showers and possible severe thunderstorms late this afternoon
  into the early evening for western and parts of northern PA.
* A secondary cold front Monday night will usher in an extended
  period of cooler than average temperatures, with areas of
  frost possible by mid-week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Fog is finally mixing out of the valleys in Central PA as of
10AM with a mostly sunny day on tap. High clouds are beginning
to stream in from the northwest associated with our next
weather maker. Southerly flow will develop by midday as deeper
mixing gets underway. Warm advection will help temperatures rise
into the 70s across most of the area. The exception will be some
of the valleys in Central and NE PA where fog held on the
longest.

Dry weather and a lack of low and mid-level clouds will
continue well into the afternoon with high pressure still in
control. THe main feature we`ll be tracking is a strong cold
front that currently extends from KSTL northeastward through
KTOL and into Quebec. The front is moisture-deprived at this
point with little to no cloud cover along it in the Ohio Valley.
Once the cold front crosses Lake Erie, we expect the front to
generate a band of showers and embedded thunderstorms with
convective initiation anticipated in northeast Ohio and
northwest PA between 4 and 5PM. The line will move southeastward
and get to western Warren county between 5 and 6PM before
moving through the rest of the forecast area into the evening.

A sufficiency of instability (500-1000 J/kg), in the presence
of strong vertical shear (effective shear of 30-50 kt), should
support the threat of locally strong-severe late day and early
evening storms across northwestern PA. Presumed increasingly
linear storm modes with time favors damaging straight-line winds
as the primary storm threat. A Slight Risk (level 2 out of 5)
remains in place for Warren and most of McKean/Elk County where
the best overlap of shear/instability exists. A Marginal Risk
extends almost all the way to US-15, highlighting the threat for
an isolated strong storm along the line. Instability will drop
off considerably with eastern extent, as should the severity of
the line of storms.

After midnight, showers should further weaken with southeastward
extent, as the best mid-level vorticity advection becomes more
separated from surface frontal convergence. Rainfall totals
could approach 0.75" in northwest PA while parts of southeast PA
could end up with no measurable precipitation if the storms fall
apart before they get there. Flooding is not a threat given the
short duration of rainfall and progressive storm motions.

Lows by daybreak should range from mid-upper 40s over the
northern mountains, to the upper 50s in the Lower Susquehanna
Valley. Northwest winds will ramp up with in an hour or two
after the front moves through, so the threat for fog should be
much lower tonight than in recent nights.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
From Monday-Wednesday, the large-scale pattern will be
dominated by a deep upper low over Ontario and Quebec, with a
cyclonic W-NW flow across the Commonwealth. This will generally
bring dry and cooler weather for the region, although a few
showers from time-time can`t be ruled out over the northern
mountains, particularly on Monday, when a vorticity lobe rotates
through.

The best chance of frost/freeze conditions across northern PA
will be on Tuesday and Wednesday nights, depending on the exact
degrees of night-time clearing and radiational cooling.

We generally expect daytime highs to range from the mid 50s over
the northern mountains, to the upper 60s in the Lower
Susquehanna Valley. Overnight lows look to range from the mid
30s-mid 40s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
The extended period should feature fairly dry weather. An
upper-level low over Quebec and the northeastern United States
will gradually pull east and be replaced by upper-level ridging
for late week into the weekend. Clouds and isolated showers will
be possible across northern PA through midweek given the
proximity of this upper low, but moisture looks limited.
Depending on clearing and how quickly Canadian high pressure
builds overhead during the second half of the week, frost will
be possible. Temperatures may begin to moderate as we head into
next weekend with the surface high beginning to pull to our
east.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
VFR will prevail much of the day across the central PA
terminals, with S-SW surface winds increasing by this afternoon
and turning locally gusty (up to around 20 kt).

A band of showers and thunderstorms should impact western and
central PA early this evening. At this point, the most likely
timing at KBFD is 22-00z, then KJST, KAOO, KUNV, and KIPT from
about 00z to 03z. We`re thinking any restrictive conditions
(mostly likely fuel alternate-MVFR) will be brief at any one
site (moderate confidence on this 40-60%).

As the night wears on, a cold front will slice across the state,
with surface winds shifting to NW. Lower clouds should move into
KBFD after 06-08z (70-80% confident), with plenty of uncertainty
on potential fog development just behind any showers (20-40%) at
KUNV, KIPT, and KAOO before northwest winds kick up and mix out
and remaining fog/restrictions.

Outlook...

Mon...Potential ceiling restrictions at KBFD and KJST, with
primarily VFR expected elsewhere.

Tue-Thu...VFR, no sig wx.

&&

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

&&

$$

SYNOPSIS...Banghoff
NEAR TERM...Banghoff
SHORT TERM...Jurewicz
LONG TERM...Guseman/Evanego
AVIATION...Jurewicz/Gartner/Bauco