PBZ issues Area Forecast Discussion (AFD) at Oct 30, 2:36 AM EDT330
FXUS61 KPBZ 300636
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
236 AM EDT Thu Oct 30 2025
.SYNOPSIS...
Periods of rain are expected into Friday morning as low pressure
approaches and crosses the region. Northwest wind may become
particularly gusty Thursday night into Friday morning. Along
with cool temperatures, a few showers may linger into the
weekend, particularly north of Pittsburgh.
&&
.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:
- Periods of rain today as low pressure approaches
- Wind gusts of 20-30 mph, especially this morning
---------------------------------------------------------------
Surface low pressure over the southern Appalachians will
continue to lift north today, reaching Pennsylvania this
afternoon. Periods of rain will continue through the overnight
hours ahead of an inverted trough associated with the mature
surface system. A bit of a dry slot may work into the region
after 12Z, potentially reducing daylight rain coverage for a
time to the east of Pittsburgh. It is here where probabilities
of an additional inch of rain after 06Z are lowest (20-40%),
while remaining a bit higher in eastern Ohio away from the dry
slot. Rain rates have not been too high to this point, generally
coming in at around 0.25"/hr or less, and this with the
expected QPF means that flooding concerns do not exist. Also,
although model soundings do show some meager elevated CAPE, the
unstable layer will have trouble extending to -10C. Thus, cloud
glaciation and lightning generation appears low probability, and
do not have a thunder mention at present.
Although a tightening surface pressure gradient has led to 15-25
MPH gusts at times in the lower elevations and to 25-35 MPH on
the ridges, it does not appear at this time that significant
easterly downslope wind gusts are likely. There are in fact
40-45 knot winds just a few thousand feet above the surface as
shown by PBZ VAD wind profiles. However, a lack of steep low-
level lapse rates, a relatively weak inversion aloft, and no
inverse shear aloft make mountain wave/downslope activity less
likely. Any ongoing wind gusts will likely slowly subside during
the daylight hours as the surface low approaches, at least
temporarily decreasing the surface pressure gradient.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Rain likely overnight into Friday morning before chances
diminish by Friday night
- Gusty northwest wind Thursday night/Friday morning, likely
requiring a Wind Advisory in eastern Tucker County
----------------------------------------------------------------
As a surface boundary crosses Thursday from near sunset into the
evening hours, cold advection and a wind shift to northwest ensue.
This should provide another shot of rain to the region this evening,
before subsidence and drier air begin to erode precipitation from
southwest to northeast. More showery precipitation is expected by
Friday morning. By Friday night, areas north of Pittsburgh,
particularly the I-80 corridor, will become more favored for ongoing
showers as northwest flow lake-effect showers should continue. With
subzero 850mb temperatures, some snow may mix in at times on the
higher northern West Virginia ridges, although there is at least
some potential that cloud tops remain warmer than -10C, which could
favor a cold drizzle at times as opposed to snow. In any case, no
snow accumulation of note is expected.
The bigger issue during this period is the potential for strong wind
gusts. With the 500mb trough taking on a negative tilt and a
tight surface pressure gradient, there is good potential for a
45-50 knot 850mb jet to mix down along the terrain as low-level
lapse rates steepen. This would be most favored during the early
morning hours of Friday. Gusts exceeding Wind Advisory criteria
remain most likely (70%-95% chance) in eastern Tucker County,
with 40%-70% chance in other areas in the northern West Virginia
ridges, as well as in portions of the Laurels. In collaboration
with surrounding offices, will hold off on Advisory issuance
for now and allow further examination by the day shift. Even
away from the terrain, surface gusts of 25-40 MPH appear likely.
Peak values will tail off later Friday afternoon and evening as
the pressure gradient slackens.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
- Periodic chances of light precipitation, especially north of
Pittsburgh
- Generally seasonable temperatures
-------------------------------------------------------------------
Ensembles generally agree that a mid-level trough will be situated
over the Upper Mississippi Valley at 12Z Saturday. However, there
are various solutions regarding the fate of this trough. There are
some that close off a 500mb low and progress it into/across the
southeast CONUS by Monday morning, while others keep a more
progressive open wave that could reach the Atlantic coast by that
time. In most cases, any impact from this disturbance would
generally remain south of our region. Meanwhile, quasi-zonal to
shallow troughing seems favored over the Upper Ohio Valley, with
shortwaves providing some periodic light precipitation chances. Even
for us, some timing/strength differences exists with these
relatively modest waves.
For now, will go with the NBM suggestions of seasonable temperatures
and fairly low PoPs, with locations north of Pittsburgh more favored
to receive a couple of light QPF events. This could change in future
forecast issuances, particularly if the evolution of the southern
CONUS shortwave/upper low differs.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Low pressure will traverse the region through the TAF period and
incite periods of light to moderate rain, alterations to wind
direction/speed, and fluctuating cig/vsby restrictions. The key
overview is that confidence is low for much of the TAF period
due to a higher-than-usual likelihood for cigs to vary from VFR
to IFR hour-by-hour, with more certainty arriving with a cold
frontal passage near to just after 00z.
Early in the TAF period, prior dry air and a downsloping east
wind are likely to slow expected cig falls relative to
deterministic GFS/NAM MOS guidance while limiting visibility
restrictions (falling in line with latest hi-res model output).
Deterioration toward MVFR/IFR is favored for most terminals but
larger spreads in outcomes through 15z remain at MGW/LBE/AGC/DUJ
due to the downslope wind effect that may dry low levels to keep
cig heights higher. As the surface low tracks over between
15z-23z, a potential warm sector may provide brief VFR periods
mixed with IFR as rain becomes more convective vs. stratiform
rain (favoring locations east of I-77 in Ohio). Surface wind
will also experience lightening while rapidly transitioning from
E/ESE to SW.
Exiting of the low after 23z will bring another band of
stratiform rain, a gusty wind shift to the W/NW, and higher
confidence in a period of IFR/LIFR (due to moisture convergence
AND cold advection). Cool advection and NW flow will see more
scattered coverage of lake enhanced showers near/after 06z as
ceilings slowly improve amid steepening lapse rates (while wind
increases in gustiness).
.OUTLOOK...
MVFR/IFR ceilings will gradually improve starting early Friday
morning and through the day amid height rises/increasing
subsidence. Look for lake enhanced showers to taper off as well.
VFR is favored by the start of Saturday but a variable pattern
thereafter creates a lot of uncertainty on timing of future
impact periods.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 30, 2:36 AM EDT---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
