578
FXUS61 KPBZ 181757
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
157 PM EDT Wed Sep 18 2024

.SYNOPSIS...
Mostly light rain to the east of Pittsburgh will largely end by
this evening as coastal low pressure pulls away. A warm and dry
pattern starts Thursday and continues through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Light rain chances, mainly southeast of Pittsburgh, continue
  into this evening.
- Patchy overnight fog possible where skies can clear.
-------------------------------------------------------------------

An elongated, east-to-west trough axis has slowly shifted northward
today from the Mid-Atlantic to New England. Easterly flow between
this trough and upper level low pressure over western North Carolina
continues, pushing moisture from the coast across the Appalachians.
Most of the generally light rain is focused on central into
southwest PA, where low-level convergence is highest. East-facing
slopes have been the luckiest with rain given the favorable terrain
influence, with 0.1 to 0.2 inch of rain over the past 24 hours, with
parts of eastern Tucker County getting close to 0.50 inch.  However,
the downslope influence has greatly hindered rain to the west, with
amounts spottier and remaining below 0.1 inch as a rule. The current
radar loop continues to show rain struggling to move east of
Indiana/Westmoreland/Fayette Counties as the flow`s drying influence
saps rainfall coverage. Some cumulus are forming along a
differential heating zone near the PA/OH border, and these may
generate some sprinkles or isolated showers. Otherwise, only
clouds are the main impact in southwest PA west of the ridges,
while eastern Ohio continues to enjoy a mostly sunny and warm
day.

This setup begins to break down as we head towards the evening
hours.  The upper low to our south will drift east and become
absorbed into a trough along the Atlantic Seaboard. This will
eventually weaken the moisture flow and low-level convergence,
leading to falling precipitation coverage even along the ridges.
Clouds will be a bit slower to clear tonight however.  Where they
do, lingering dewpoints in the upper 50s/lower 60s and light wind
may lead to at least patchy fog development. This seems most likely
in eastern Ohio, where cloud cover will likely be the lowest. Low
temperatures will run roughly 5 to 8 degrees above normal.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
KEY MESSAGES:

- Mostly dry weather expected for Thursday and Friday.
- Slowly warming above-normal temperatures are expected.
-------------------------------------------------------------------

Any patchy fog will lift by mid-morning, and the remainder of
Thursday will be characterized mainly by decreasing cloud cover and
warmer temperatures as the coastal trough slowly pulls away. This
process will be slowest in the ridges southeast of Pittsburgh, and a
lingering shower or two cannot be ruled out in Preston/Tucker
Counties into the afternoon. Quiet weather is then anticipated
areawide Thursday night as surface high pressure becomes a bit more
established.  Elevated dew points at nighttime will keep lows a tad
warmer than normal, and a round of nighttime fog is possible once
again.

Friday will feature continued dry weather as 500mb ridging
builds from the lower Mississippi Valley into the Ohio Valley.
The increasing heights point to a further warmup, with most
locations reaching into the 80s for afternoon highs.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Dry and warm weather through the weekend.
- Low chances of light rain arrive early next week.
- Above average temperatures continue, with some moderation by
  Wednesday.
-------------------------------------------------------------------

The ridge to our west builds slowly eastward with time this weekend
in most model scenarios, suggesting that mostly dry weather and
above-normal temperatures are the most likely outcome.  A few less-
likely outcomes suggest that shortwave energy trying to top the
ridge comes in stronger and quicker than the consensus, leading to a
bit better chance of rain ahead of an approaching warm front.  For
now, will run with the warm and dry forecast, and watch future runs
to see if this minority trend has legs.

Uncertainty increases from there for Monday through Wednesday, as
more pronounced Upper Midwest troughing starts to interact with the
ridge.  Cluster analysis shows differing scenarios regarding how
quickly the ridge gets knocked down and shunted off to the east,
with implications for rain chances and temperatures.  A trend
towards lowish, increasing PoPs and lower, but still above-normal
temperatures looks best for the current forecast, with a more
pronounced change possible in future forecast updates.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
With an upper-level low drifting lingering across the region
today, moisture and weak ascent will continue the chances of
drizzle/light rain for areas east and south of PIT. Expect a
MVFR to IFR conditions for LBE/MGW; AGC/DUJ may bounce between
MVFR to VFR into the evening. However, confidence in prevailing
MVFR for DUJ/AGC is considered low.

Hi-Res model guidance suggests restrictions returning early
Thursday morning for a number of sites with lingering low-level
boundary moisture. Foggy conditions for ZZV, HLG, and BVI may
develop with clearing. MVFR to IFR stratus may also redevelop
near the ridges and impact MGW/LBE/DUJ.

.Outlook...

There is the potential for some early morning fog again Friday
morning.

VFR is then expected through Sunday as high pressure builds in.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...WM/Hefferan