336
FXUS61 KPBZ 220051
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
851 PM EDT Sat Sep 21 2024

.SYNOPSIS...
Very warm weather is expected through the weekend. Fog is
possible overnight and early Sunday morning.  A wetter pattern
is becoming increasingly likely next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
KEY MESSAGES:

- Thunderstorms ending this evening
- Clearing skies late with areas of fog overnight.
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Update...
Additional thunderstorms have developed across Forest, Clarion,
and Jefferson counties where a surface boundary was located, and
as an upper trough was crossing NW and north central PA. Colder
air aloft was enhancing ascent in this region as well. This
activity should diminish and exit the region over the next one
to two hours as the trough shifts ewd, and diurnal instability
wanes.

Very dry air has mixed down behind the surface boundary, with
dew points in the 40s to the lower 50s. This should limit fog
formation across Ohio and far western PA., though areas
generally east of I 79 should see fog development overnight,
especially where rain fell earlier today.

Gridded LAMP guidance had the best handle on the wide range of
temperatures and dew points across the area this evening. Nudged
the forecast closer to these values overnight.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
KEY MESSAGES:

- Dry with above average temperatures on Sunday.
- Rain chances (yes, rain chances) increase starting Monday.
-------------------------------------------------------------------

A shortwave ridge axis will slide overhead in the wake of the
departing disturbance from Saturday with height rises and warm
advection supporting temperatures again into the 80s, warmest in
eastern Ohio, with 90 not out of the question there. High clouds
will increase in the evening from the west ahead of approaching low
pressure.

The main takeaway headed into the next workweek is that we are
finally seeing appreciable chances for beneficial rain. The upper
ridge axis will quickly be shunted east by an approaching trough,
and a shift to southwest flow aloft on its backside will open the
door for better moisture to work its way into the region. Clustered
ensembles exhibit pretty good agreement through Tuesday night with
just some strength and timing differences of the progression of the
responsible upper trough. Rain chances will increase Monday morning
as surface low pressure progged to be across Michigan pulls a trough
through the area. Ensemble probability for >0.5" of rain through
Tuesday night is still high (up to 80%) and a 50-70% chance of >1".

&&

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

- Rain chances increase Monday and Tuesday with a widespread,
  beneficial rainfall possible.
- Rain chances continue for the latter half of the week but
  confidence in amounts is low.
- Temperatures closer to average through the week.
-------------------------------------------------------------------

Uncertainty then increases significantly with ensembles
becoming much more spread on how the upper pattern evolves. The
majority consensus is that the Ohio Valley remains in a
troughing setup with significant differences on placement and
amplitude of the trough, but even one solution is attempting to
establish a ridging pattern. For continued beneficial rain, we
would want the solution(s) that sets up a trough deeper and off
to our west. Long story short, scenarios exist where additional
beneficial rain sticks around for the latter half of the week,
and scenarios exist for a drier period.

Despite this uncertainty, at least continued low precipitation
chances are appropriate through the end of the work week. 72 hour
precip totals have seen a slight eastward nudge in the past several
ensemble runs with probability for another >0.5" from Wednesday
through Saturday morning at 40-50% east of Pittsburgh and 20-40%
further west. A few high end, low probability scenarios exist
pending tropical influence. All told, the wetter pattern next week
holds some promise to at least somewhat mitigate the ongoing
drought. Temperatures moderating to seasonable levels (for daytime
highs at least) will help as well.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Skies have mostly cleared across the region this evening behind
the departing cold front. Overnight fog is likely at terminals
that received rain this afternoon... which include all sites
other than BVI and ZZV. However, IFR fog restrictions are less
likely at PIT, AGC, and HLG, while IFR to LIFR is more likely at
DUJ, LBE, and MGW. Fog will lift by 14Z, with VFR conditions
for the remainder of Sunday under building high pressure.

.Outlook...
Rain and restriction chance increase late Sunday night into
Monday with another crossing cold front. Unsettled weather is
then possible through mid-week.

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...WM
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Rackley