PBZ issues Area Forecast Discussion (AFD) at Nov 20, 6:47 AM EST342
FXUS61 KPBZ 201147
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
647 AM EST Thu Nov 20 2025
.SYNOPSIS...
Dry weather continues today under high pressure. Rain chances
increase early Friday before decreasing Saturday morning. Higher
rain totals will be largely south of Pittsburgh. Seasonable
temperatures are expected through the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
- Fog, freezing fog (north of PGH), and low clouds this AM
- Dry and cloudy, with seasonable temperatures through the day
---------------------------------------------------------------
Saturated low levels and light wind along with surface high
pressure centered over the region has resulted in morning fog
development, resulting in a Dense Fog Advisory that is valid
through 9AM. Areas north of PGH are under a Freezing Fog
Advisory where temperatures <32F and visibilities <1/4mi have
been observed, and are likely to persist through 9AM as well.
As far as impacts, other than visibility under 1/4 mi in places,
areas north of PGH may see a light glaze on elevated surfaces,
bridges, and overpasses. Looking at latest METRo road
temperature forecasts the window where road surface temperatures
could be below freezing looks to be in between 4AM and 8AM this
morning.
Fog should diminish mid-morning with increased mixing, with
latest guidance showing 20% chance or less of any fog <1/4mi
lingering between 9AM and 10AM in areas with the densest
coverage, however, low stratus is likely through the day as low
level moisture remains trapped under a strong inversion. Surface
high pressure centered over the northeastern U.S. and ridging
extending southwestward across New York and into western PA will
maintain dry and cloudy conditions, with seasonable
temperatures during the day. Overnight will be largely dry, but
rain chances will begin to increase early in the morning as low
pressure approaches from the west.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
KEY MESSAGES:
- Rain returns on Friday
- Near to above seasonable temperatures
----------------------------------------------------------------
A surface low will push through the Midwest and Ohio Valley
regions on Friday, resulting in widespread rain chances during
the afternoon and evening, with the highest chances PGH and
south. Temperatures will rise to 5-10 degrees above seasonal
levels.
There is still a wide spread with model guidance regarding
exact rainfall amounts with this system, however, overall there
has been consistency signaling that the highest amounts will
fall along and south of the I-70 corridor, with lesser amounts
as you head north.
Here are the latest NBM 10th/25th/75th/90th percentiles from
(north to south)
-10th: Zero precipitation outside of a couple hundredths over
Tucker County
-25th: Zero PGH and north, up to 0.25" in WV
-75th: 0.20" north of I-80, 0.80" in northern WV
-90th: 0.75"north of I-80 to 1.25" in northern WV
Looking at LREF clusters (no GEPS), it appears there is really
just issues with the depth of the trough. A deeper and/or slower
trough would lean towards higher rainfall totals across the
region while the weaker and/or faster trough would result in
lower rainfall accumulations. There are members in each cluster
really pulling up those higher percentile amounts but the
majority are closer to the mean which is where the current
forecast is close to.
In any case, this should be stratiform, life-giving rain with
rates remaining light to occasionally moderate. Thus, there is
little concern for flash flooding at this time and most area
rivers are expected to see only minor rises, if any. Storm
drains clogged with leaves would likely be the only issues.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
KEY MESSAGES:
- Near to above seasonable temperatures continue
- Rain tapers Saturday morning, followed by dry conditions the
rest of the weekend
- Unsettled weather returns early to middle next week
-------------------------------------------------------------------
After a few possible light rain showers or sprinkles lingering
Saturday morning(best chances along the ridges), Saturday will
be largely dry, which will then continue through at least
Sunday.
By Monday, numerical guidance hints at another upper trough ejecting
eastward from the Rockies across the Great Plains, setting us up for
another low pressure system to move into the Ohio Valley region
during the early to middle part of next week. There is still too
much uncertainty to begin narrowing down any specifics regarding
precipitation types, amounts, or timing. The takeaway here is that,
at this time, the weather pattern next week appears unsettled,
and precipitation chances will increase during the day Monday
and last through the first half of the week.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
A saturated, cool air mass with stagnant flow is aiding
widespread IFR/LIFR and fog, with pockets of freezing fog at
FKL/DUJ where temperature is at/below freezing.
The combination of minimal air mass changes with current
conditions is resulting in vastly different model portrayals of
cig/vsby trends creating a low confidence forecast. TAFs steered
toward generic fog trends in a stagnant environment where
improvements are slowly seen through the afternoon. Influence of
New England high pressure may allow northern terminals
(FKL/DUJ, but maybe as far south of PIT) to see further
improvements than forecasted through 00z.
The saturated airmass remaining in place likely favors
redevelopment of MVFR to IFR cigs with a more limited fog threat
tonight into Friday morning. The biggest uncertainty in this
period is whether a subtle uptick in southerly surface flow
provides lift/clear during the overnight hours (from S to N) or
acts to reinforce the moist airmass that creates probabilities
for LIFR cigs and patchy fog.
Outlook...
Any restriction improvements seen Friday morning will be short-
lived as rain overspreads the area Friday afternoon into
Saturday morning, favoring locations around/south of Pittsburgh.
MVFR/IFR will be highly likely in areas of rain, with potential
for near VFR conditions on the northern periphery if rain
doesn't develop (FKL/DUJ).
There is high confidence of VFR under the influence of high
pressure beginning Sunday morning until the next low pressure
system arrives near Tuesday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Dense Fog Advisory until 9 AM EST this morning for PAZ020-021-
029-031-075-076.
Freezing Fog Advisory until 9 AM EST this morning for
PAZ007>009-013>016-022-073-074-077-078.
OH...Dense Fog Advisory until 9 AM EST this morning for OHZ049-050-
057>059-068-069.
WV...Dense Fog Advisory until 9 AM EST this morning for WVZ001>004-
012-021-509>514.
&&
$$
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...88
LONG TERM...Cermak/88
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Nov 20, 6:47 AM EST---------------
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