PBZ issues Area Forecast Discussion (AFD) at Mar 5, 12:44 PM EST316
FXUS61 KPBZ 051744
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1244 PM EST Wed Mar 5 2025
.SYNOPSIS...
Rain and strong storm potential today will dive way to snow
chances tonight and tomorrow. Totals may approach 2 to 4 inches
in higher terrain. A clipper provides additional snow chances
late Friday through Saturday morning, though impacts will be
limited. A warm up is likely into next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
KEY MESSAGES:
- Strong storm and wind potential today (highest chances from
now through 9pm) given way to gusty snow chances tonight.
-------------------------------------------------------------------
A strong low pressure system will continue to pass north of the
region, providing a number of impacts through the next 24
hours. The three main focuses will be strong storm potential
today (1), gusty wind potential today through tomorrow (2), and
snow chances tonight through tomorrow (3).
1) The first strong storm threat will materialize this
afternoon. CAMs have been consistent in storm development along
a prefrontal trough east of Pittsburgh, with the main threat
window between 1pm and 5pm. In this period, mesoanalysis suggest
a window of >500 SBCAPE and 45kt to 55kts of bulk shear to
co-locate over portions of Preston, Tucker, Fayette,
Westmoreland, Indiana, and Jefferson County (PA). This
environment would be supportive of severe weather with the main
uncertainty in development tied to the strength of the forcing,
and wither storm initialization will be able to use the
instability. Should storms initiate, the primary threat remains
damaging winds, through hail and isolated tornadoes could not be
ruled out. For severe hail, storms would need to top above
12-15kft, which may be difficult with the limited instability
and a inversion evident in that level on the 12Z sounding.
Given hat the shear is primarily boundary parallel to the flow,
we would expect convection to quickly evolve linear upon
initiation. In order to realize the already low tornado threat,
we would either need intense updraft development in the brief
discrete phase in right moving cells or notches in the
anticipated QLCS.
The second, but lower severe threat today will come along the
occluded front within the dry slot of the low around 4pm to
9pm. This would move from west to east across the area, with
chances tapering into Pennsylvania. This would bring risks of
winds and hail, through chances of occurrence are lower than
earlier in the day. Tornadoes are not expected with this wave
given the high cloud bases. Confidence is increasing that
updrafts will have a hard time materializing with this wave with
the over- prevalence of dry air up-stream. This has already
been observed in Ohio.
2) There is a chance of gusty winds into this afternoon as we
deepen the mixed layer with the dry slot moving overhead.
Observed gusts across Ohio are roughly into the 30-40mph range,
which we would expect to be the maximum observed synoptic wind
gusts into this afternoon. Gusts in the high terrain of eastern
Tucker County have already been observed up to 57mph, which is
within a wind advisory.
In the evening, gusts subside for much of the lowlands with
shallow stabilization, but this will be short lived. Overnight,
gusts increase yet again as cold advection destabilizes the near
surface environment. Once again, 30mph to 40mph gusts remain
possible with 75% confidence. This continues late tonight into
tomorrow.
3) Overnight, as temperatures cool in northwest flow and a
strong gradient, typical wrap around snow is expected to fill
in. Most of this will begin to fall after midnight in eastern
Ohio, spreading over mich of the area before sunrise. There is a
>75% chance of a dusting area-wide, though chances of >1" are
confined to mainly the high terrain with orographic lift. The
only chances of >3" are for the highest peaks of the Laurels and
in the ridges of Preston and Tucker County WV. A winter weather
advisory remains in place for the threat accordingly. Snow
showers may continue into early tomorrow, decreasing from
southwest to northeast as the low pulls away, but with the March
sun angle and warm surface temperatures, impacts are expected
to be limited.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Rain changes to snow tonight into Thursday.
- Dry weather into Friday.
- Rain and snow chances return by Friday night.
--------------------------------------------------------------------
Strong post-frontal cold advection tonight will drop 850 mb
temperatures from roughly +5C to -10C with rain showers changing
to snow showers. Typical upslope enhancement into the ridges
will result in 1-3" of snow in the Laurels, and up to 5" across
the Preston/Tucker ridges through Thursday. This is an increase
from previous forecast cycles as confidence in a bit more snow
increases. A Winter Weather Advisory was issued for eastern
Preston and eastern Tucker counties [WV] late tonight through
Thursday evening. Elsewhere, only light snow amounts are
expected. Antecedent very warm air should preclude efficient
accumulation, but the highest amounts will be in the WV ridges.
Pressure gradient remains tight on Thursday as low pressure
exits east. This will keep gusty conditions tonight through
Thursday, with 25-35 mph gusts expected across the lowlands and
Laurels, and gusts up to 55 mph possible across eastern Tucker.
This could certainly create periods of blowing snow through the
day.
High pressure is favored to build into the area Thursday night
which will shut off any lingering snow showers. This will keep
the area dry into Friday with seasonable temperatures. A weak
impulse passing through the Ohio Valley could then bring
rain/snow showers Friday night into Saturday, but marginal
temperatures at this time point toward low end accumulation
potential.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Near seasonable temperatures with warming early next week.
-------------------------------------------------------------------
Drier weather returns on Saturday. Uncertainty remains in the
evolution of a second system on Sunday, though most of the
guidance has a relatively modest trough and a potential for snow
showers. GEFS members and the deterministic GFS have
significantly backed off the more extreme solutions flagged in
previous days, moving more in line with the EPS and CMCE
guidance and keeping more robust moisture far to our south.
Strong signals continue for height rises early next week, signaling
quiet weather and warming temperatures through midweek.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
VFR conditions, mixed with some MVFR cig potential, is expected
through a large portion of today as the Ohio River Valley
resides within the warm sector of a large scale low pressure
system. Waves of rain, and perhaps thunderstorms, will likely
be the vicinity of terminals ahead of a passing cold late this
afternoon afternoon.
Potential thunderstorms may create strong to severe wind gusts
in the vicinity of terminals between 19Z to 23Z. At this time,
these storms have been included in a PROB30 group due to spatial
and timing confidence.
With a strong pressure gradient, synoptic wind gusts may range
from 20kt to 30kts today; 25kt to 35kts near LBE due to
downsloping.
Outlook... Rain transitions to snow overnight as cold advection
increase in the wake of the front; widespread MVFR cigs are
likely through 18Z Thursday. VFR potential increases between
18Z to 23Z with mid level subsidence.
Precip and restrictions can return with another disturbance on
Friday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Winter Weather Advisory from midnight tonight to 8 PM EST
Thursday for WVZ512-514.
Wind Advisory until 7 PM EST this evening for WVZ514.
&&
$$
SYNOPSIS...Milcarek
NEAR TERM...Milcarek
SHORT TERM...Rackley
LONG TERM...Rackley/MLB
AVIATION...Hefferan
Source:
PBZ issues Area Forecast Discussion (AFD) at Mar 5, 12:44 PM EST---------------
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