619
FXUS61 KPBZ 210901
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
401 AM EST Fri Nov 21 2025

.SYNOPSIS...
Foggy conditions this morning. Probability of rain increases
late this evening and continues into early Saturday. Mild
conditions are likely this weekend and into early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
- Localized dense fog expected through 9am
- Probability of rain increases after sunset

---------------------------------------------------------------

With weak advection in place early this morning, the risk of fog
remains elevated. A Dense Fog Advisory continues for locations
east of Pittsburgh, including the Laurel Highlands, where
visibilities have fluctuated between one-quarter and one-half
mile over the past few hours. Areas in eastern Ohio and near the
Pennsylvania- West Virginia border will be monitored for a
possible expansion of the Advisory.

The threat for fog will likely rapidly decrease between 9am and
10am with diurnal heating promotes boundary mixing.

A weak trough passing near Lake Erie may produce a brief period
of light rain or drizzle north of Pittsburgh near dawn. A more
persistent rain is expected later tonight as a low pressure
system approaches from the southwest. Overall rainfall totals
should remain light, ranging from a trace to 0.3 inches through
midnight.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
KEY MESSAGES:

- Drier conditions expected Saturday with seasonable
  temperatures
----------------------------------------------------------------

Rain will likely persist past midnight early Saturday as the
previously mentioned disturbance moves through the region.
However, precipitation chances quickly diminish from west to
east between 4am and 6am as a cold front sweeps across Lake
Erie.

Increasing subsidence in the low and mid levels associated with
building high pressure should thin cloud cover by Saturday
afternoon. Still, extended periods of sunshine may be limited at
times due to ongoing cold advection over the Great Lakes.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
KEY MESSAGES:

- Dry and mild Sunday into Monday
- Precipitation chances return Tuesday into Wednesday
- Cooler pattern expected Thanksgiving
-------------------------------------------------------------------

Long-range models over the last 24 hours continue to show ridge
development over the Great Lakes from Sunday into Monday. This
pattern support mild, dry conditions during the afternoon hours.
However, with the potential of overnight clearing and lingering
dry air near the surface, temperatures are expected to fall back
toward climatological average--hovering near or just above
freezing during the early morning hours of Sunday and Monday.

Precipitation chances increase Tuesday into Wednesday as a
trough shifts form the Midwest and into the Great Lakes, drawing
warm, moist air northward from the southwest into the Ohio River
Valley. Rainfall totals may be limited, especially if a dry
slot pushes into the region early Wednesday. The probability of
receiving a half inch of rain within 24 hours remains below 10%.

More than half of the long-range models indicate a pattern shift
developing late Wednesday into Thursday, as broad ridging over
Alaska and the West Coast reinforces a large-scale trough across
the Great Lakes. This setup favors a return to below-average
temperatures and an increased potential for lake-enhanced snow.


&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Largely widespread IFR is how the TAF period begins. Many ports are
sporting low stratus, this and a thicker mid-level cloud deck has
limited explosive fog growth that was observed last night. However,
the stagnant air mass remains in place and there is minimal flow at
the SFC with ample moisture available.

Models have struggled in this pattern but paint a reasonable outcome
over the coming hours with fog slowly spreading across the region as
low stratus lowers through the night. At this time, fog has favored
our eastern ports, but an expansion in this coverage seems favored
before 12z at this time fog with VIS as low as 1/2SM has been
included in tempos for most ports between 08-12z. FKL lies near the
edge of low stratus at this time and any clearing there will likely
help them bottom out more quickly than ports underneath the stratus
deck. The final extent and coverage may not be as wholesale as last
night. Fog is expected to begin to slowly mix and lift by 14-16z but
progress will likely be slow.

Approaching low pressure encourages some lift and CIG improvement
from SW to NE later on Friday but the upper limit of this may still
be high end IFR/low end MVFR with overrunning associated with the
warm front. Rain chances look more likely to hold off until after
00z but isolated sprinkles are possible through the afternoon and
evening.

Outlook... Rain is favored to overspread the area Friday evening
into Saturday morning with the greatest restrictions/rainfall
accumulations occurring 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 PAZ016-074-
     076>078.
OH...None.
WV...None.

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...AK