PBZ issues Area Forecast Discussion (AFD) at Oct 2, 6:45 PM EDT142
FXUS61 KPBZ 022245
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
645 PM EDT Wed Oct 2 2024
.SYNOPSIS...
Dry weather settles in for the remainder of the week and into
the weekend with high temperatures still above normal. Rain and
thunderstorm chances return late Sunday.
&&
.NEAR TERM /THROUGH THURSDAY/...
KEY MESSAGES:
- Fog possible late tonight especially in the river valleys.
-------------------------------------------------------------------
Evening update...forecast in great shape. Skies clearing as much
drier air overspreads the region. Made some minor adjustments to
evening cloud cover and refreshed overnight lows with the latest
hires data.
Previous discussion...
For tonight, skies become mostly clear with light to calm
surface wind under a strong nocturnal inversion and increasing
subsidence. Combined with remnant low level moisture, the setup
is favorable for fog in the river valleys as cold air moves
over the warmer waters. Hi res ensemble probabilities also
increase for areas of fog south of Pittsburgh with a 40-70%
chance, but if wind remains slightly elevated, these chances are
probably a bit overdone.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Dry with highs above average but cooler low temperatures.
- Cold front passes Friday night with no precip expected.
-------------------------------------------------------------------
Not much of an impact to high temperatures will be felt in the
post-frontal airmass as southwest flow aloft reestablishes on
the northern periphery of a building ridge. Ensemble mean 850
mb temperatures increase to 13-14C and abundant sunshine with
mixing into a dry boundary layer will allow highs to rebound
nicely to the mid 70s areawide (which is 5-8 degrees above
climatology). Overnight lows will be cooler than in recent days,
but actually closer to normal values, in the 40s and 50s.
Ensembles slide a shortwave through mid-level westerlies on Friday
with very slight differences in depth that likely won't have much
impact locally. Indications are for a mostly dry frontal
passage Friday night given little meridional component to the
deep layer flow and thus insufficient moisture return; most
likely outcome is just an increase in clouds as ensembles have
mostly come into agreement on a dry passage. Sightly further
modification of the airmass on Friday favors it to be the
warmest of the week with mid to upper 70s likely for most, but
probabilities jump to as high as 60% for >80F in far southeast
Ohio and northern West Virginia, especially in the river
valleys.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
KEY MESSAGES:
- Cold front passage late Sunday brings thunderstorm chances.
- Drying out into next week with high pressure returning.
-------------------------------------------------------------------
Another dry day returns on Saturday under high pressure which
will be quickly pushed off to the east by another approaching
trough and surface front for Sunday. This overall setup is
looking perhaps a bit more impactful than with Friday's
front/pre-frontal trough featuring a potential low end severe
weather threat with a more amplified upper trough in northwest
flow aloft; this is supported by the latest machine learning
guidance which has introduced a broad area of low end
probabilities along the boundary. Ensembles continue to exhibit
trough amplitude and frontal timing differences and what impacts
we see locally will be tied to these features. For better
thunderstorm and rain chances overall, a more amplified trough
and thus stronger moisture advection would be preferred. In
terms of timing, a slower passage, which some members are
pushing back into the early overnight hours, likely results in
lower severe chances with unfavorable diurnal timing. An earlier
passage, which other members are advertising in the early
evening, would favor a better severe threat. While it's too
early to dig into specifics, these are the aspects to monitor.
Behind the front, temperatures favor a return closer to seasonal
norms toward the end of the period as high pressure returns. How
quickly it arrives and we kick rain chances out of here will be
dependent on the progression of Sunday's trough, but confidence in
the overall pattern evolution is high.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Clear skies and calm winds are expected tonight as high pressure
begins to build across the Upper Ohio Valley region. Dew points
have dropped into the 40s for much of the area, though areas
from LBE to MGW remain in the 50s as clearing occurred last in
these areas. This should limit fog to the river valleys,
affecting FKL, HLG, DUJ and AGC where MVFR to IFR vsbys are
expected early Thursday morning. Areas from LBE to MGW should
see more fog even outside of the valleys, where dew points
remain higher.
After any morning fog mixes out, VFR is expected with a light
south wind as the surface high moves east.
.Outlook...
Outside of any localized early morning river valley fog, VFR is
expected through Thursday under high pressure. A dry cold front
will cross the region Friday, with an increase in clouds though
VFR continuing. High pressure maintains VFR Saturday until
shower and thunderstorm chances return Sunday with a crossing
cold front.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...MLB
NEAR TERM...22/MLB
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 2, 6:45 PM EDT---------------
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