Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 151919
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
319 PM EDT Fri Oct 15 2021

.SYNOPSIS...
Unseasonably warm weather will finish out the week with near
record highs expected today. Gusty showers and a few
thunderstorms will precede a strong cold frontal passage on
Saturday. Noticeably cooler air will return to CPA by Sunday
with temperatures trending lower/back to seasonal levels for mid
October. Fair and dry weather is expected early next week.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
150PM/1750Z: A lone severe storm moved across Clearfield County
early this afternoon exhibiting supercell characteristics with
a large hail core aloft. A local convenience  store in Grampian
confirmed hail but could not estimate the size. Reports of
trees down were received via the 911 center. The storm has
weakened some moving into northern Centre County over the RDA
as of this writing. A few additional showers have developed
across the western Alleghenies, which may be the start of
another round of severe weather given gradually improving
CAPE/shear parameter space. 18Z temps should be in the 80s
across the southeast 1/2 of the area and on track to push into
record territory. We updated the HWO based on a slight eastward
expansion in the D1 SLGT risk which now includes the State
College area.

SPC just issued MCD #1865 indicating a 40% chance of a watch
across far northwest PA just barely clipping Warren County. Some
hires guidance is bullish on some storms developing to the ENE
of State College, but general take is for activity/coverage to
remain rather isolated.

1045AM/1445Z: Cluster of showers/t-storms tracking northeast
between KBTP/KIDI not modeled very well by the HRRR. 3km NAM and
NBM are much better in the next 1-3 hours taking this batch of
convection into the NW Alleghenies by 18Z. Adjusted POPs closer
to this model/radar trend and cleaned up HWO/enhanced wording
for severe storm potential later this afternoon. No change to
the SPC D1 outlook updated at 13Z and would not anticipate much
change with the next update around 1630Z. Cloud cover was
holding temps down in a few spots, but expect nearly sunshine
over the southeast 1/2 of the CWA to send temps surging through
the 70s by early afternoon.

Previous Discussion Issued: 357 AM EDT Fri Oct 15 2021

Nearly stationary front extends from central OH to far NW PA
northward to western Lake Ontario. Bands of moderate showers
continue to traverse Lakes Erie and Ontario. Isolated showers
have moved north of the PA/NY border out of my northwest early
this morning. Increasing low level moisture and orographic lift
thickens low clouds over my northwest this morning.

Amplifying mid level troughs pushes into the Great Lakes and
Ohio Valley later today, and this combined with diurnal heating
and falling heights will result in afternoon convection.
Consensus of CAM solutions depict a cluster of convection
tracking from southwest PA across the northern and central mtns
from the mid to late afternoon hours into the early evening,
and instability and shear profiles support a marginal or greater
risk of isolated severe storms over central and west central
areas with locally strong to damaging wind gusts the primary
tstm hazard. MaxTs should make a run at daily records with fcst
highs in the mid 70s to low 80s or +15-20F above normal.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH SATURDAY NIGHT/...
2PM: No significant changes to this period which will feature a
well-defined, airmass changing frontal passage - bringing fall
conditions back to CPA after a toasty start to October. Expect
some mdt to heavy rainfall along the sharpening front sweeping
through the CWA during the day tomorrow. There could be some
convectively enhanced wind gusts along the front, but the a
severe wind threat will be limited owing to weak instability.
The most likely area for strong gusts appears to be over the
eastern part of the area.

Previous Discussion Issued: 357 AM EDT Fri Oct 15 2021

Earlier thoughts of a lull in shwr/tstm coverage after evening
diurnal activity weakens is still in play for Saturday night.
Sfc cold front sharpens in response to strengthening mid/upper
trough starting to transition from neutral to negative tilt.
This should result in a band of moderate showers/low- topped
convective line, reaching the NW zones around 06Z and the
central mountains around dawn.

Latest model guidance is also supporting an anafront structure,
with cold front surging ahead of the upper level deformation
zone. This scenario favors weaker/broader lift along the cold
front and a lower chance of severe wx. Strong post-frontal fgen
forcing beneath of dual jet streak structure should result in
the bulk of the rain falling behind the front into Saturday
morning. Ahead of the front over eastern sections, it will be
another unseasonably mild night with fcst lows +20-25F above
climo.

The front ever so slowly crosses the Central Mountains and
through the eastern half of the Commonwealth early Saturday
afternoon with slowly improving conditions from west to east
late Saturday afternoon and night, but with the season`s first
lake effect rain showers expected behind the FROPA over NW PA,
as we finally cool air of note reaching into the area late
Saturday.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Sunday will be windy, with cooler conditions, which are much more
seasonable for mid-October. As the main upper-level trough/cold
core aloft moves across the Commonwealth. With still fairly warm
water temperatures on Lake Erie, lake enhanced/upslope rain showers
are likely along the Allegheny front and over northern PA. Farther
south and east into the Susquehanna Valley, it will be generally
dry with the aid of downsloping. Sunday`s highs will be more
seasonable, ranging from the 50s over the higher terrain, to the
lower 60s in the Middle and Lower Susquehanna Valleys. Chilly
temperature readings both Sunday night and Monday night.

As heights begin to build aloft and surface ridging builds in
Monday into Tuesday and Wednesday, we should see a nice stretch
of dry weather and sunshine. Sunshine will help to moderate
temperatures Tuesday and Wednesday. Doesn`t look cold enough at
this point for frost except maybe a few isolated spots in the
northwest. By Thursday, a low pressure center moves across Lake
Erie and Ontario. An associated cold front moves east through PA
bringing a chance of showers to most of Central PA. POPs range
from low 20s Lancaster to around 40 in Bradford. Part of the
reason for not having high POPs is probably uncertainty with
timing. Also while both the GFS and the EURO take the low across
the Eastern Great Lakes, the Euro starts filling it and the GFS
begins rapidly deepening the center. This leads to a wide
spread of temperature and precipitation possibilities for Friday
as a secondary front with some colder air may move in sparking
some more scattered showers.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Scattered showers and thunderstorms are expected to increase in
coverage this afternoon into this evening. Primary areas of
concern are NW PA /BFD/ and storms that fire off of the
Allegheny Front and move east /JST, AOO, UNV, IPT/. MVFR cogs
and vis in storms, with gusty winds and hail possible.

Overnight, more widespread showers and possible storms will
result in widespread reductions to IFR cigs/vis. Storm activity
will pick up again during the day Saturday in eastern PA /MDT,
IPT, LNS/ with restrictions once again possible.

A CFROPA Saturday may result in some LLWS, along with gusty NW
flow behind the front Saturday evening.

Outlook...

Sat...Cold frontal passage likely early Sat. Widespread showers
and storms.

Sun...Low cigs NW. Isold/sct showers and gusty NW winds post
frontal passage.

Mon-Tue...VFR/no sig wx.

&&

.CLIMATE...
Thursday`s high of 80 degrees in Altoona ties the record high
set on Oct 14, 1954.

Record high temperatures for October 15:

MDT|84/1897
IPT|82/1975
AOO|83/2017
BFD|77/1989
STC|84/1897

&&

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

&&

$$
SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Watson/Jurewicz/Fitzgerald
AVIATION...Banghoff/Wagner
CLIMATE...


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