PBZ issues Area Forecast Discussion (AFD) at Oct 13, 1:45 PM EDT674
FXUS61 KPBZ 131745
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
145 PM EDT Tue Oct 13 2026
.WHAT HAS CHANGED...
Updated aviation section for 18z TAF package. Probability for
Wind Advisory criteria on Friday and sub-freezing temperatures
Friday night and especially Saturday night has increased a bit.
&&
.KEY MESSAGES...
1) Dry and unseasonably warm on Tuesday.
2) First of two cold fronts this week sweeps through on Wednesday.
3) Much stronger late-week cold front returns showers, gusty
wind, and high temperatures more like that of mid-November for
Friday and Saturday.
&&
.DISCUSSION...
KEY MESSAGE 1...
If you're a summer lover, enjoy today before we jump ahead a full
season by Friday and Saturday. Locally, we'll remain in the broad
warm sector of a low pressure center off to our north. A tightening
pressure gradient ahead of the attendant surface cold front passage
expected on Wednesday will increase warm, moist advection in
southwest flow. The 850 mb temperature off of our 12z sounding came
in at 17C which is a daily record and would support highs in the mid
80s beneath mostly clear skies. The wrinkle to that will be the
aforementioned southwest flow increasing dew points through the day
despite drier air within the mixed layer as even the dry-biased HRRR
doesn't mix out. All that said, think that we'll probably top out in
the low 80s across most of the area (70s in the elevation).
Nocturnal cooling will be hard to come by tonight with elevated
wind, high dew points, and increasing cloud cover holding overnight
lows in the low to mid 60s. Some area record highs on Tuesday may be
approached, but record warm lows on Wednesday are less likely with
cooler temperatures Wednesday night. More detail in the Climate
section below.
KEY MESSAGE 2...
A slow moving cold front finally gets a kick and moves through our
area north to south on Wednesday returning showers and a few storms.
Some storms could get a bit on the stronger side, but the primary
limiting factor to that will be a displaced instability axis
from the highest shear. The belt of strongest mid-level flow,
and thus deep layer shear, will be to our north. The best
opportunity for heating and better instability will be off to
our south in the thinner cloud cover out ahead of the front.
REFS joint probability for >500 J/kg of SBCAPE and >30 knots of
shear peaks south of I-70 into northern WV around 60-90% with a
sharp cutoff north owing to much less destabilization. So, the
area to watch for storms to get more feisty and bring a low-end
damaging wind threat would be to the south, confident with
SPC's Marginal Risk. Can't entirely rule out some localized
higher rainfall totals in northern WV where REFS prob for
>1"/hour reaches around 40%, but this will be highly dependent
on training with east-west motion and any impacts would only be
in the urban areas.
KEY MESSAGE 3...
The most impactful system arrives on Friday ushering in strong wind
gusts, well below normal temperatures, and showers. While some
uncertainty remains among ensembles primarily owing to timing and,
to a lesser extent, depth of the mid-level trough, confidence in all
three impacts remains high. Deep surface low pressure will pull a
cold front through the area on Friday with a tight pressure
gradient, 10+ dam 500 mb height falls in 12 hours, and strong low-
level cold advection.
For the wind threat, the combination of the tight gradient and
mixing into a 40-45 knot low level jet should result in widespread
gusts of 35-45 mph. They'll be stronger across our higher elevation
where probability for Wind Advisory criteria gusts >46 mph reaches
up to ~60%. Eastern Tucker County runs an elevated probability for
High Wind Warning criteria gusts >58 mph also up to around 60%.
Current NBM probability for Advisory criteria gusts in the lower
elevation is around 30-40%, so certainly can't be ruled out, but
headlines look most likely in the ridges.
Strong cold advection in post-frontal northwest flow will bottom out
ensemble mean 850 mb temperatures to around -2 to -4C. An
unseasonably cold air mass will settle in for the first half of
the weekend providing the potential for two nights of frost and
freeze. Friday night, probabilities are a bit less bullish
outside of our I-80 counties where 30-40% sneaks in for <32F,
but frost concerns could be higher with probability for <36F
reaching 70-80% north of Pittsburgh and down the ridges.
Saturday daytime highs will feel more like those of mid to late
November only warming to near 50 degrees with 40s in the
elevation. The gradient will relax some Sunday night allowing
wind to slacken and skies will clear. This could point toward
Saturday night being the coldest areawide with better
radiational cooling conditions amid a dry, cold airmass. The dew
point could be the floor for lows with optimal radiation, and
this suggests widespread low to mid 30s and upper 20s. A
widespread frost is likely. Probability for a freeze ranges from
40-80% in eastern OH, northern WV, and western PA, with the
highest values away from urban areas and in the higher
elevation. Expect that we'll be looking at some combination of
frost/freeze headlines on top of wind headlines in the next
couple days.
Two rounds of precip are possible both along the front itself and
then in the wrap around cold advection across the lakes on Saturday.
Strong flow amid the dynamic system could drive some "power showers"
accompanying FROPA on Friday bringing enhanced gusts with them
provided they're able to get tall enough to tap into the 40-50 knots
a few thousand feet off the ground. We'll have to see what the
thermodynamic profile looks like as the CAMs come into play in the
next 24-36 hours, but the current RRFS does show enough fumes of
SBCAPE. Then, continued cold advection in northwest flow likely
results in some lake effect and upslope precip late Friday into
early Saturday. For most, this will be a cool, windy scattered
rain/graupel shower setup. For some, the first novelty snowflakes of
the season aren't out of the question. Ground temperatures will be
too warm to see it stick, and there's some question to the remaining
depth of the moisture and whether or not it's deep enough to
generate snowflakes or sits in the favored supercooled liquid
region. Either way, the only areas that may see some white stuff
falling should be the highest elevations of PA and WV and the far
reaches of our northern tier of counties.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Surface low tracking across New York this evening will gradually
push a slow moving front south into the area. Wind gusts to 20
knots should drop off late this afternoon with loss of heating
and weakening pressure gradient near front. After sunset with
boundary layer stability and decoupling, a few hours of LLWS is
expected at HLG BVI PIT AGC LBE DUJ from about 01 to 05z.
Outlook...
Restrictions (most likely MVFR) in showers and possible thunderstorms
return Wednesday with a slow moving cold front. This front is
expected to return north as a warm front Thursday, with additional
shower and restriction chances.
A strong cold front is expected to cross the region Friday morning,
with showers and widespread gusty wind.
Probability of KPIT Gusts Friday:
35+ Knots 90%
40+ knots 60%
45+ knots 30%
50+ knots <10%
Subsequent upper troughing should maintain restriction potential,
along with scattered rain/snow showers into early Saturday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
DISCUSSION...MLB
AVIATION...Craven
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 13, 1:45 PM EDT---------------
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