742
FXUS61 KPBZ 200920
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
420 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 early 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 a fairly good
morning for fog development. Despite fairly widespread low
stratus and upper level clouds streaming across the region PGH
and north, fog has developed across the region, enough so to
warrant a Dense Fog Advisory that has been issued and 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 the early
morning. 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 /09Z THURSDAY THROUGH MONDAY/...
Stout low level moisture and a lack of SFC flow allows the
forecast period begins with widespread dense fog bringing VIS
down to 1/4SM at many ports. Those not at this level are
expected to trend that way over the coming hours. Eastern ports
(DUJ/LBE) have found themselves in FZFG with temps below 32. FKL
currently sits near the edge of the expanding fog but is
expected to experience FZFG early this morning. With little
change in conditions overnight, this fog is expected to remain
locked in until at least 14z, where we may begin to see a little
mixing out starting across the region.

It is tough to imagine we make large gains in CIGs through the
morning hours and only marginal improvements are forecast
through midday. Beyond that it becomes more difficult to pin
down where our CIGs will trend. Some high-res models are rather
optimistic with a brief period of high MVFR/low VFR CIGs this
afternoon, but with how poorly they have handled the last 24
hours it is difficult to put much stock in this solution. The
more likely scenario at this time is that CIGs rise marginally
in the afternoon, returning to more widespread low MVFR before
another eventual reduction in CIGs again Thursday night.

Winds remain largely light through the TAF period with a minor
Nerly component early before a swing to the SW during the
afternoon.

Outlook... Chances of restrictions and rain increase with a
passing disturbance on Friday. The area could dry out as early
as Saturday morning, after which a gradual scattering of clouds
could be seen.

&&

.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...AK