030
FXUS61 KCTP 110323
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1123 PM EDT Fri May 10 2024

.SYNOPSIS...
Upper level troughing will remain over Pennsylvania this
weekend. A strong shortwave moving through the broader flow will
generate numerous rain showers and a couple of thunderstorms on
Saturday afternoon and night.

The upper trough will lift out early next week, then a cold
front will likely push through Tuesday. A wave of low pressure
is likely to track south of Pennsylvania next Wednesday.

&&

.NEAR TERM /UNTIL 8 AM SATURDAY MORNING/...
Per the latest nighttime microphysics imagery/loop, fog has
been forming rapidly and expanding throughout the valleys of the
NW and Laurels where it has tried to clear out. The hill tops
may offer some visibility of the sky/Aurora for a short time
before any fog gets there. BFD had a brief time in VFR before
crashing to VLIFR (100` vertical visibility) and 3/4SM
horizontal visibility. There may be a window to see the lights,
but it may close quickly in many places.

Prev...
Our focus has been on the sky cover forecast. No one likes to
throw the wet blanket (of fog or low clouds/drizzle) on a
party, but...

The best chance of seeing the Aurora Borealis in PA since 2003,
due to the ongoing historic (G5) geomagnetic storm, may be a
dud for most of Central PA. The wind is almost gone. The rain
of earlier and the low clouds/drizzle over the central counties
have put lots of moisture on the ground and in the near sfc air.

The clouds which are due to the shortwave which powered the
rain of earlier today (Fri) are sliding eastward. However, this
is just about the perfect setup for fog. It is a very low
probability that even a small part of the CWA can clear out and
stay clear as the fog is expected to fill in behind clearing. If
the low clouds don`t get us (that is, stay in place), the fog
will - restricting the visibility and obscure the sky. However,
people in Huntingdon Co have already seen a reddish glow to the
sky through some thin spots in the clouds. Then again, fog can
be shallow, and may allow for some colors to be seen.

&&

.SHORT TERM /8 AM SATURDAY MORNING THROUGH MONDAY NIGHT/...
After the break from the rain tonight into early Saturday,
expect a return of showers Saturday PM associated with height
falls ahead of a potent upper level shortwave diving across the
Grt Lks. Strong large scale forcing, in combination with some
minimal model cape, supports high POPs with a tsra possible in
spots during the afternoon. Moderate PWAT values indicate that
rainfall Sat PM should not be significant, generally between
0.1 and 0.2 inches based on ensemble mean qpf.

The upper trough is progged to cut off and track along the
PA/NY border Sat night into Sunday morning. Low level
instability associated with this feature should result in
plenty of cloud cover and at least scattered showers lasting
into early Sunday. Brightening skies and diminishing showers
look likely by Sunday afternoon, as the upper trough exits the
state and surface surface ridging builds in from the west.
Mixing down progged 850mb temps of around 4C translates to
expected highs in the low to mid 60s over much of the forecast
area, with upper 50s over the higher terrain of Eastern PA.

Closed 500mb low moves across PA/NY border early Sunday followed
by rising heights into early next week. This will translate into
a seasonably cool and showery Mother`s Day followed by a warmer
and mainly dry start to next week. QPF will remain light given
lack of deep moisture. Forecast daytime high temps on Sunday in
the 55-65F range are 5-10F below early May climo. Max temps
should rebound +10-20F on Monday aided by a milder SW flow.

A cold front trailing low pressure in eastern Canada is fcst to
stall out over the lower Great Lakes Monday and could trigger a
shower or t-storm over the far NW mtns. Most of CPA should start
the week rain-free.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
A wave of low pressure will approach from the Ohio Valley
Tuesday before crossing the area Tuesday night. This system
will be accompanied by a renewed chance of rain and perhaps
some thunder.

Lingering unsettled weather is possible into Wednesday, before
a ridge build this system Wed night into Thurs. The overall
upper level pattern heading into next weekend looks rather
blocky - which is typical for this time of year - but also
results in much lower confidence/predictability. Some data
suggest a cut- off low pressure system could bring a slight risk
of heavy rainfall on 5/18 per the latest CPC 8-14 day hazards
outlook.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Light rain has largely tapered off across central PA, although
patchy drizzle lingers. As the low clouds pull out of the
western highlands, the nighttime microphysics satellite channel
reveals fog quickly forming.

Diminishing winds and ample low-level moisture will likely
result in widespread fog and/or very low clouds developing
overnight across much of central PA, with IFR/LIFR conds
possible at all airfields outside of perhaps the Lower Susq
Valley.

Cigs and vsbys should improve to VFR areawide by midday on
Saturday, before another round of rain showers pushes from west
to east across the area Saturday aftn/eve.

Outlook...

Sun...AM low cigs possible W Mtns. Sct afternoon showers/brief
reductions possible.

Mon...AM dry and mainly VFR. Showers return across the north by
aftn.

Tue...Showers/tstms and reductions developing.

Wed...Showery weather and reductions continue.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Lambert/Steinbugl
LONG TERM...Steinbugl/Evanego
AVIATION...Evanego