055
FXUS61 KCTP 111817
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
217 PM EDT Sat May 11 2024

.SYNOPSIS...
Upper level troughing will remain over Pennsylvania this
weekend with a potent shortwave tracking over the state tonight
into early Sunday. 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 6 PM THIS EVENING/...
Shortwave ridging over central PA this morning is bringing a
several hour period of fair weather with some breaks in the
recent overcast conditions. However, an upstream trough digging
southeastward from the central GLAKS will bring a return to
showers this afternoon and evening as the upper low tracks to
southern Ontario by 00z Sun.

Strong large scale forcing, in combination with some minimal
model cape, supports high POPs with a tsra possible in spots.
Highest POPs should accompany the passage of the southerly low
level jet and plume of best pwats. Convection- allowing models,
which should perform well with this strongly forced system,
indicate the most concentrated band of showers/tsra should
arrive over the Alleghenies around 18Z, reach peak intensity
over the Central Mtns at peak heating around 20Z, then push into
the Susq Valley this evening. Although a brief, heavy downpour
will occur in many locations, modest PWAT values indicate that
rainfall should generally not be very heavy. Ensemble mean qpf
of 0.2 to 0.4 inches represents the most likely rainfall by late
this evening.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
The upper trough is progged to cut off and track along the
PA/NY border tonight into Sunday morning. Low level instability
associated with this feature should result in plenty of cloud
cover and at least scattered showers lasting into Sunday
afternoon, especially over the eastern half of the forecast
area. Brightening skies and diminishing showers look likely by
late 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.

The upper trough is progged to lift out early next week, with max
temps rebounding +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 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 builds in Wednesday night into Thursday. This will
support the longest period of dry and sunny weather we have seen
in awhile. 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.
Such a pattern supports changeable weather with temperatures
oscillating around average for this time of year. 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 /18Z SATURDAY THROUGH THURSDAY/...
VFR conditions will prevail until another round of rain showers
arrives from the west this afternoon evening. The main batch of
showers will last for a couple hours at each airfield with
limited thunderstorm activity. After the initial batch of
showers moves through, scattered showers and a few thunderstorms
will move across the region and will generally weaken with
eastward extent. Have not mentioned thunder in any TAFs at this
time, but may need to amend as observations warrant.

Ceilings will lower to MVFR across much of the area tonight as
winds shift to come out of the southwest and then west. IFR
reductions are most likely at IPT (70%) and MDT/BFD (50%) after
midnight. Scattered showers will continue overnight with
occasional visibility reductions possible. Clouds may scatter
out across the south central mountains, which would allow for
the potential of valley fog development. AOO is the most likely
airfield to be affect by fog at this point, but not enough
confidence to include mention in the TAFs.

As westerly winds develop on Sunday and occasionally gust to
20 kts, overcast skies will overspread the region with
widespread MVFR conditions continuing through midday. Gradual
improvement is likely during the afternoon, but scattered
showers will remain possible until daytime heating tapers off
later in the evening.

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.

Thu...Trending drier with more breaks in the cloud cover.

&&

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

&&

$$

SYNOPSIS...DeVoir/Fitzgerald
NEAR TERM...DeVoir/Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Banghoff/Evanego
AVIATION...Banghoff/Bowen