518
FXUS61 KPBZ 182259 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
659 PM EDT Wed Sep 18 2024

.SYNOPSIS...
Lingering showers and sprinkles will end this evening as drier
air moves in from the west. A warm and dry pattern starts
Thursday and continues through the weekend.

&&

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

- Light rain chances, mainly southeast of Pittsburgh, continue
  into this evening.
- Patchy overnight fog possible where skies can clear.
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Evening update...scattered showers/sprinkles continue to
dissipate due to weakening upper level support and drier air
moving in from the west. Cloud cover will be much slower to
dissipate as we still remain under the large eastern trough.
This will make fog forecasting tricky for areas that saw rain
today. Have removed all PoPs later this evening and made
adjustments to cloud cover. Rest of the forecast is in good
shape.

Previous discussion...

The stagnant pattern of the last two days will break down this
evening. 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 dwindling precipitation coverage. 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 NIGHT 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 WEDNESDAY/...
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 /00Z THURSDAY THROUGH MONDAY/...
General VFR forecast through the period. The biggest question
overnight will be the development of fog. With cloud cover
expected to hang on longer overnight this will work against fog,
especially dense fog. Have mentioned fog at sites that saw rain
today and those in river valleys. Expect decreasing cloud cover
Thursday.

.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...22/CL
NEAR TERM...22/CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...WM/22