PBZ issues Area Forecast Discussion (AFD) at Jun 25, 9:32 PM EDT076
FXUS61 KPBZ 260132
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
932 PM EDT Thu Jun 25 2026
.WHAT HAS CHANGED...
The Key Message for Thursday has been removed.
&&
.KEY MESSAGES...
1) A stalled boundary keeps rain chances in the forecast Friday
and Saturday, with some potential for isolated heavy rainfall
totals and instances of flooding.
2) High confidence in the development of hot and humid
conditions next week.
&&
.DISCUSSION...
KEY MESSAGE 1...
As the front loses much of its upper support and becomes
parallel to quasi-zonal mid-level flow, much of its forward
speed will be lost, and it should eventually ooze to a nearly
stationary position either in or just south of the forecast
area, where it would likely remain through at least Saturday.
Additional shortwave energy should provide support for rounds of
showers and thunderstorms, especially Friday night and
Saturday, with best coverage generally south of US-422. Severe
weather risk from this activity appears relatively low given the
daytime heating issues this pattern could provide. However,
building precipitable water south of the boundary (1.7-1.8 inch
values eventually) and the potential for training thunderstorms
supports the notion of a risk for at least isolated flooding
issues across the southern CWA into Saturday. A marginal risk of
excessive rainfall covers much of the forecast area south of
I-80 for Friday and Friday night. By Sunday, the front may more
decisively nudge to our south, bringing an end to the heavy
rain threat.
KEY MESSAGE 2...
The boundary is set to lift back north of the region Monday.
There is broad model agreement on a strong 500mb upper high on
the order of 597 dm forming over the Ohio Valley in the vicinity
of southern Indiana. The main impact of this pattern is likely
to be the season's first sustained run of heat and humidity,
with the NBM indicating 70 percent or greater chance of 90+ high
temperatures over most of the non- ridge areas Tuesday through
Thursday. Accordingly, probabilistic Heat Risk guidance shows
70% or greater chance of Major (level 3 of 4) or higher impacts
over most of the CWA. We have deterministic Heat Indices in the
lowlands of 100 to 105 both Tuesday and Wednesday which are
representative. Looking at the NBM Wednesday July 1st 21z
Apparent Temperature percentiles, the 10th and 90th range from
93F-104F at KPIT, but for Downtown Pittsburgh the values are
100-115F. Those large spreads are typical and during heat waves
the daily cloud cover and thunderstorms chances also cause
uncertainty but the main message is hot and humid next week.
Secondary to the heat will be the eventual reintroduction of
some level of severe weather risk. Most likely, given the
abundant buoyancy potential and weak flow, this would come in
the form of typical mid-summer wet downburst wind threats.
There is a lower-end potential for a suppressed ridge by the end
of the week, which could create a upper level northwest flow
setup, a pattern which has been responsible for notable severe
weather events in the past. Of course, there is plenty of time
to monitor for that potential.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Area coverage of showers and thunderstorms (currently focused
north of KPIT) will generally dissipate through 06z tonight with
loss of diurnal heating. The exception is passage of a mid-level
shortwave trough axis that could spur mostly isolated rain
showers up until 09z, but is too low for TAF mention.
VFR clouds are likely to hold through 12z where mid to high
level clouds remain thick, but areas that clear and/or areas
that saw higher rainfall accumulations may see IFR/LIFR
stratus/fog develop near 08z-12z. Thereafter, VFR resumes save
for a period of cu development plus moist advection against the
stalled surface boundary that lends to MVFR cigs between
14z-18z.
Hi-res modeling is fairly bullish on delays in the next
shortwave's arrival, so TAFs reflect a later start time for the
ensuing round's shower/thunderstorm potential.
Outlook...
The active weather pattern continues through the weekend with
multiple periods of showers/thunderstorms as well as
restrictions (mainly associated with storms).
Chances wane through the day Sunday with drier NW flow and
height rises that result in high pressure dominating the region
by Monday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
DISCUSSION...Shallenberger
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Jun 25, 9:32 PM EDT---------------
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