PBZ issues Area Forecast Discussion (AFD) at Apr 13, 1:35 PM EDT479
FXUS61 KPBZ 131735
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
135 PM EDT Sun Apr 13 2025
.SYNOPSIS...
High pressure will keep dry conditions in place for Sunday. A
stout cold front will arrive on Monday with the potential for
strong to severe storms possible Monday afternoon and evening.
Strong winds and showers are possible on Tuesday before some
snow shower chances Tuesday night.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Light showers possible overnight with a passing warm front.
-------------------------------------------------------------------
Lots of sunshine continues this afternoon before clouds return
this evening ahead of an approaching mid-level shortwave trough
and associated warm front. Weak forcing from the trough may
allow enough lift in a progressively saturating mid-layer to
support a few light rain showers, roughly after 8pm in eastern
Ohio and closer to midnight or later in western Pennsylvania.
The warm front will approach from the southwest towards Monday
morning, with overriding air further forcing a bit of lift north
of the surface front and potentially squeezing out some light
rain or drizzle during pre-dawn hours. Any accumulation from
these two rounds will be light (a couple hundredths of an inch
at best) as showers will need to overcome sub-cloud evaporation
in a dry near-surface layer. In fact, chances of seeing any
accumulations from this only maximize around 30% due to the
mitigating factors.
Temperatures will remain mild overnight due to the increasing
cloud cover and onset of warm air advection in the wake of the
warm front. Lows remain in the low 40s up near I-80 and mid to
upper 40s farther south, roughly 5 to 8 degrees above normal for
this time of year.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
KEY MESSAGES:
- Severe storms possible Monday afternoon and evening, with the
best chances south of I-80 and especially south of I-70.
- A cold front brings below normal temperatures back to the area
Monday night.
-------------------------------------------------------------------
Into Monday, the region will be pushed into the warm sector of a
potent low traversing across the upper Great Lakes, and
adjacent triple- point low over the lower Great Lakes. The
strength of warm air advection in the boundary layer will
determine the amount of instability the area is able to muster.
Latest ensemble guidance shows a 30-50% chance of 500 J/kg
SBCAPE across the local area, with higher probabilities
remaining farther south in central West Virginia. One thing
that is certain is shear, however, with up to 50kts of storm
average flow and vertical wind profiles supportive of supercells
should any discrete thunderstorms form in the area.
Analogs have been consistent with showing a hail threat, though
winds remain just as concerning with an expected storm motion of
40-50 mph. Despite the presence of up to 30kts of shear in the
0-1km layer, tornadoes remain a secondary threat due to a lack
of low-level hodograph curvature and uncertainty regarding low-
level instability and storm mode (squall line vs. discrete
supercells). That said, the tornado threat is certainly not
zero, with the best chances residing along and south of the
I-70 corridor. Flooding concerns remain low with fast storm
motion and low training potential.
There is still some timing uncertainty with the storms, but
most of that is encompassed within a late afternoon/evening
timeframe. With the amount of shear available, it will not take
a lot of instability to create significant impacts. Even
minimal clearing during the day Monday might be all that is
needed to get the necessary daytime heating to support a larger
severe threat, so pay close attention to the forecast over the
next 24-36 hours for possible changes. Severe chances quickly
end behind the cold front, which pushes through late Monday
night.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
KEY MESSAGES:
- Gusty winds on Wednesday as well.
- Wet conditions to end the forecast period.
-------------------------------------------------------------------
Low level cold advection, will tend toward forcing near-
saturation and destabilize the low-levels aloft. All the while,
surface heating into Wednesday afternoon will destabilize
profiles from the surface. This will enhance mixing into a
850mb jet of up to 40kts to 60kts, bringing widespread gusts of
up to 35mph to 45mph Tuesday afternoon and evening during peak
mixing. Gusts may be as high as 50mph to 60mph in the highest
terrain of Pennsylvania and West Virginia. Secondarily, moist
unstable conditions, combined with a mid-level shortwave
passage, will allow for widespread shower development with rain
and even some small graupel/hail development with freezing
levels of just 4kft to 6kft and vertical development up to 12kft
possible. Overnight, meager instability will be maintained with
cooling temperatures which may lead to snow development. Most
ensembles maintain at least a light coating in the I-80 corridor
north of Pittsburgh and high terrain Tuesday night into
Wednesday morning. As a worst chase scenario, an inch or two is
possible in eastern Tucker and north of I-80, which may allow
for a few slick spots for the Wednesday morning commute.
For Wednesday, surface high pressure will be centered over the
lower MS River Valley with the ridge axis extending north into
the Upper OH Valley region. The gradient still in place will
make for gusty winds once again over the ridges but mainly over
eastern Tucker County.
High pressure will continue to keep the region dry for
Thursday. Temperatures will be around normal for this time of
year as highs are expected to cross 60 degrees across much of
the area. This day will also have the potential of low RH during
the afternoon. Uncertainty is maintained in the forecast beyond
Thursday with two clusters (65% of ensemble membership) tending
toward quasi- zonal flow, and another two clusters showing more
pronounced eastern troughing with embedded shortwaves, which
would tend a bit wetter and cooler (35% of ensemble membership).
&&
.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
High pressure centered just north of the region will result in
light winds and plenty of sunshine through the remainder of the
afternoon. Mid and high clouds will overspread the region
this evening into tonight, associated with an approaching warm
front. Light rain showers are possible, with the first round
moving across the area from west to east in the 00z-06z
timeframe and the second round in the 07z-13z timeframe.
Ceilings and visibilities likely remain at VFR through roughly
12z tomorrow, after which MVFR ceilings build in from west to
east through the end of the TAF period. The the passage of the
warm front Monday morning, winds shift to southwesterly by
15z-18z and increase to around 7-10 knots with gusts to 15-20
knots.
Outlook...
Restrictions possible Monday evening with showers and
thunderstorms along a crossing cold front. Restrictions and
precipitation chances continue into Tuesday as an upper trough
settles in overhead. Snow could mix in with rain north of I-80
during the day and then elsewhere overnight into early Wednesday.
Winds may become gusty behind the cold front as well, with
peaks potentially reaching the 30 to 40 knot range Tuesday and
the 20-30 knot range on Wednesday. Dry weather returns Wednesday
and Thursday with building high pressure before another round
of showers and storms (and restrictions) on Friday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Cermak/Milcarek/Shallenberger
NEAR TERM...Cermak/Shallenberger
SHORT TERM...Cermak/Milcarek/Shallenberger
LONG TERM...Milcarek/Shallenberger
AVIATION...Cermak/88
Source:
PBZ issues Area Forecast Discussion (AFD) at Apr 13, 1:35 PM EDT---------------
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