PBZ issues Area Forecast Discussion (AFD) at Sep 5, 7:50 AM EDT704
FXUS61 KPBZ 051150
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
750 AM EDT Fri Sep 5 2025
.SYNOPSIS...
After areas of fog dissipate this morning, another round of
showers and low probability thunderstorms will overspread most
of the region tonight into Saturday and result in well below
average temperature. Dry weather with slowly rising temperature
is favored Sunday through early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Areas of fog will dissipate after sunrise
- Showers and low probability thunderstorms return late this
evening, with a non-zero damaging wind threat
---------------------------------------------------------------
735 am update...
Stratus and fog have redeveloped in areas that initially
improved early this morning. The latest data from the 12Z PIT
sounding shows a strong surface inversion, which should maintain
this fog and stratus early this morning. Will continue the Dense
Fog Advisory as is, and it expect it continue through 9am.
520am update...
Satellite and surface observations indicate an uptick in
southerly flow within the boundary layer has eroded dense fog
for most locations around and south of Pittsburgh, prompting a
cancellation of the Dense Fog Advisory.
Rest of Discussion...
The combination of light wind and abundant near surface moisture
has aided in areas of fog developing for much of the forecast
area with locally dense conditions being observed. A Dense Fog
Advisory was issued to highlight northwest PA where more
widespread dense fog conditions are likely to persist. The only
reservation is hi-res model guidance suggesting some visibility
improvements with increased southerly flow that may end dense
fog concerns quicker.
After diurnal heating and increased mixing erodes area fog, the
region will experience dry conditions with more seasonable
temperature for most of the daylight hours. These conditions are
likely to be short-lived as a deep upper level shortwave enters
the lower Ohio River Valley and its associated strong mid-level
jet lifts NE towards the area. Jet-induced ascent will be strong
enough to induce showers and low probability thunderstorms
generally after 6pm ahead of the next surface cold front. The
main questions are whether convective initiation can be early
enough to tap into some surface based buoyancy AND if there is
enough surface heating to overcome warm mid-level air to
increase buoyancy so that any storm updraft isn't immediately
sheared. At this time, the joint probability of generating
around 1000 J/kg CAPE along with the 40kts 0-6km shear is low
(10-15%), but the conditional threat that could portend damaging
wind/hail/tornado threats remains fair to highlight. Hazardous
conditions are likely to ease by midnight, but waves of shower
activity will persist as embedded shortwaves continue to lift NE
through the strong SW flow aloft.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
KEY MESSAGES:
- Rounds of rain possible, though trends shift the precipitation
axis east for Saturday
- Well below average temperature Saturday will trend closer to
normal Sunday
--------------------------------------------------------------
The Upper Ohio River Valley will continue to sit east of the
main upper trough axis that is expected to see additional
shortwave movement Saturday. These waves will help push a
nominal cold front SE through the region during the very early
morning hours Saturday as well as promote periods of generally
light to occasionally moderate rain showers through the evening.
Ensemble model trends suggest the slightest shift east of the
axis of precipitation expected to occur in response to eastward
edging of the upper dry slot (and ultimately the trough axis).
This shift may allow for the far northwest forecast locations
(located in NE OH) to more quickly see rain chances end and a
return of some sunshine to boost afternoon temperature; other
areas in rain will struggle to see warming. The result is all
locations will be well below normal, with the degree of
afternoon temperature rising correlated with the persistence of
rain through the day.
There is high confidence in dry weather developing Saturday
night into Sunday morning just prior to the upper trough axis
passage. These dry conditions are likely to continue into Sunday
with dry westerly (shifting eventually northwesterly flow) and
increasing high pressure. However, lift associated with the
trough axis and cold temperatures aloft may be enough to develop
lake enhanced showers north of Pittsburgh Sunday afternoon;
latest guidance suggests 850mb flow will be westerly enough that
most shower development should remain along/north of I-80.
Temperature will remain well below normal as most cities
struggle to reach 70 degrees for a high (average temperature is
78 degrees in Pittsburgh Sunday, for reference).
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
KEY MESSAGES:
- Rising temperature through midweek with dry weather
- Next rain chances not until late next week.
-------------------------------------------------------------------
Ensemble models are highly confident that the combination of
surface high pressure and gradual height rises aloft will
promote dry weather, temperature returning to seasonal averages
by Wednesday.
The next weather system may not occur until the late week period
and will be dependent on depth/timing of trough movement as a
Western CONUS trough, Central CONUS ridge, and Eastern CONUS
trough type pattern develops.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
Low level moisture in place under a strong temperature inversion
will maintain IFR fog and stratus early this morning. Mixing
will begin by mid morning, dissipating the fog and stratus. The
CU rule and model soundings indicate a scattered diurnal cumulus
layer should persist through much of the rest of the day. Mixing
should result in gusty SW wind from mid morning through late
afternoon.
A shortwave trough and surface cold front will approach the
region this evening. Convergence in the vicinity of the front,
along with elevated instability, could result in a few showers
and thunderstorms developing overnight. Maintained a prob30 for
most airports, as development of this convection is uncertain. A
wave of low pressure is then progged to track NE along the front
late tonight into Saturday, with MVFR restrictions and showers
expected. The potential for thunderstorms will end as the
instability diminishes.
.OUTLOOK....
Restrictions are possible into Saturday evening as the cold front
exits the region. A crossing upper trough could result in cig
restrictions and isolated showers N of PIT on Sunday, otherwise
VFR is then expected (other than erly morning vly fg) through
Tuesday as high pressure builds in.
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Dense Fog Advisory until 9 AM EDT this morning for PAZ008-009-
013>016-022-077-078.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Frazier
NEAR TERM...WM/Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Sep 5, 7:50 AM EDT---------------
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