PBZ issues Area Forecast Discussion (AFD) at Aug 25, 9:48 PM EDT
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FXUS61 KPBZ 260148
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
948 PM EDT Sun Aug 25 2024
.SYNOPSIS...
Surface high pressure will maintain mostly dry conditions and
well above normal temperatures this week. Showers and
thunderstorms will be possible at times, mainly later in the
afternoon into the evening.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
KEY MESSAGES:
- Mainly dry conditions continue with some showers north and
east of PIT toward dawn.
- More mild night than Saturday night.
-------------------------------------------------------------------
Remaining showers have diminished with sunset and will give way
to a quiet period for most of the overnight hours. Increasing
moisture, cloud cover, and rising heights will keep overnight
low about 5 degrees above the norm tonight, with area
temperatures falling into the mid 60s for much of the area.
Another subtle shortwave will cross late tonight/early Monday
morning. This may support another round of isolated to widely
scattered showers across eastern OH into western PA. Hi res
ensemble reflectivity paintballs indicate highest coverage north
and east of Pittsburgh in closer proximity to the passing wave.
Forecast soundings still keep some marginal elevated instability
(500-600 J/kg), so a few rumbles of thunder will remain
possible.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
KEY MESSAGES:
- Mainly dry weather continues, though isolated thunderstorms
and a Marginal Risk for severe are possible Monday afternoon
and evening.
- Continued well above normal temperature.
-------------------------------------------------------------------
While probabilities remain low, strong diurnal heating Monday
afternoon in conjunction with increasing surface dewpoints and
weak shortwave movement could lead to isolated shower/thunderstorm
development. Low-end probabilities exist for an isolated
strong-to-severe storm during the afternoon. SPC has maintained
a Marginal Risk for portions of the area, which is reasonable
given increased shear, greater instability, and steeper mid-
level lapse rates. The primary threat with any storm will be
strong winds.
Upper ridging will slowly shift east and begin to flatten on
Tuesday as Midwest troughing lifts and fills. Rising heights and
southwesterly low-level flow will boost area temperatures in to
the 90s outside of the I-80 corridor and higher terrain.
Increasing humidity will likely push heat index values into the
upper 90s and possibly triple digits Tuesday afternoon. The
HeatRisk map shows a level 3 of 4 "Major" risk for much of the
area. Overnight temperatures will stay above 70F for most.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
KEY MESSAGES:
- Temperatures remain well above normal with apparent
temperatures nearing 100F.
- Mainly dry conditions continue, with low-end precip chances
through mid-week.
-------------------------------------------------------------------
Upper ridging will continue to flatten into Wednesday as fairly
zonal upper flow develops through Thursday. Shortwaves in this
flow will allow additional showers Wed afternoon/evening as a
weak cold front passes. For now, have maintained only a slight
chance with PoPs generally 20% or less, but this may need to be
increased as confidence improves.
With the ridge axis progged to be centered more over the
eastern CONUS, area high temperatures will likely be pushing
low-to-mid 90s for much of the area on Wednesday(outside
I-80/ridges). NBM MaxT probabilities of 90F+ have increased to
around 70-80% for the metro and eastern Ohio... near 90% for
downtown Pittsburgh and the river valleys. Dew points near 70
will push heat index values near or above 100F on Wednesday
afternoon. Will continue to monitor this for possible issuance
of a Heat Advisory.
Ensembles indicate amplifying central-CONUS ridging by late
week, renewing northwest flow over the area and bringing some
relief from the heat. A more potent cold front is progged early
weekend, which may return more widespread rain chances to the
area.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Stray showers are having a difficult time surpassing mid-level
dry air. The potential for thunder with isolated convection will
remain low for several hours.
A new weak disturbance ejecting off of Lake Erie after 06Z
Monday morning may provide another opportunity for isolated
showers. CAMs are a touch more bullish with this one, so elected
to keep the ongoing VCSH mention from 09Z to 14Z. Again, any
impact will be brief, and VFR will mostly prevail. Cannot rule
out valley fog near FKL/DUJ with any clear patches, and made TAF
mention there.
After 12Z Monday, any linger fog will dissolve, and another
round of high- based cumulus will develop by midday.
Improved instability and a weak shortwave may allow for
slightly better chances of afternoon isolated showers and
storms, most of which will be after 18Z. PROB30 was used at PIT
for that 30-hour TAF.
.Outlook...
VFR will remain favored through much of the week, with
convection closely tied to weak shortwave movement along the
northern periphery of the central CONUS ridge.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Rackley/88
NEAR TERM...Rackley/MLB
SHORT TERM...Rackley
LONG TERM...Rackley
AVIATION...Hefferan/CL
Source: PBZ issues Area Forecast Discussion (AFD) at Aug 25, 9:48 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202408260148-KPBZ-FXUS61-AFDPBZ)
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