Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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FXUS61 KPBZ 271224

Area Forecast Discussion
National Weather Service Pittsburgh PA
724 AM EST Fri Jan 27 2023


Snow showers will taper and end this morning as high pressure
briefly visits. A clipper brings another round of light
precipitation Friday night. Overall temperatures will be above
normal this weekend then return below normal for most of next


A push of drier air has led to some cloud breakup from
Pittsburgh on west, but expect this to fill in as an eastern
Great Lakes shortwave trough swings through. Scattered to
numerous snow showers, mainly north and east of Pittsburgh at
this point, will taper off through the morning with the passage
of the shortwave. The departure of the 850mb thermal trough and
the continued introduction of drier air from the west, will
also aid in the decreasing trend. An additional half-inch of
accumulation may be seen in spots, particularly in the ridges,
before activity ceases.

A transient mid-level ridge will cross the region this afternoon,
leading to a brief dry interlude.  The drier air and mixing will
break up clouds somewhat, allowing for a bit of afternoon sunshine.
This should allow high temperatures to climb towards climatologic

The last in the current series of shortwaves in the departing mean
trough will cross the region tonight, along with a warm front.
Precipitation will remain generally light, given a very modest bump
in precipitable water and overall meager lift driven by warm
advection/weak isentropic lift.  Precipitation will begin as snow,
and then perhaps mix with rain south of I-80 overnight.
Precipitation may even taper to drizzle in spots before ending as
cloud tops warm.  Near and north of I-80, an inch or less of snow
accumulation is possible, with less elsewhere.  Low temperatures,
mostly ranging from the mid 20s to the lower 30s, will be achieved
during the evening before a slow rise overnight.


Generally dry weather is expected into Saturday evening in WSW
quasi- zonal flow aloft as a baroclinic zone sets up to our
northwest. An inversion at around 850mb will keep low-level
moisture trapped, with a mostly cloudy sky as a result.
Temperatures will climb back above normal as warm advection
starts ramping up during the afternoon.

Low pressure is then expected to track along that boundary late
Saturday night and Sunday, bringing a better shot of moisture an
isentropic lift than the shortwave tonight. Given the low track,
all rain is forecast during this period. Likely/categorical
PoPs are appropriate. Still, with precipitable water topping out
at around 0.5 inch and with a lack of strong frontogenesis/jet
support, overall light precipitation totals are again forecast.

As the front settles into the region Sunday night, precipitation
may mix with/change to snow to the north of Pittsburgh by 12Z
Monday, but little accumulation is expected as cold advection
will be fairly weak, and surface temperatures may remain
relatively warm.


Ongoing light precipitation Monday morning may taper off by
afternoon as surface high pressure ridging tries to build in. In
any case, plenty of moisture and clouds will linger, with
perhaps some lingering sprinkles/flurries through the afternoon.
Monday night may provide a brief dry period along with
seasonably cold low temperature.

Predictability starts to take a hit thereafter. The southern
stream will likely provide the next weather-maker during the
Tuesday/Wednesday period, with the EPS perhaps a bit more eager
to push precipitation northward into our region than the GEFS.
With cold air in place, precipitation could begin as snow or a
wintry mix, before potentially mixing with/changing to rain at
least across the southern counties. While some Tuesday
night/Wednesday morning snow could provide impacts to the
morning commute, NBM probabilities of 24 hour snow of 2 inches
or greater top out at around 20-30 percent north of Pittsburgh
through Wednesday evening, so chances of widespread, significant
snow accumulation remain low. Drier weather is possible by

Although precipitation remains uncertain, it seems more clear
that below-normal temperatures will make a return from Tuesday
onward, with increasing probabilities of low temperatures in the
teens, and even perhaps the single digits in spots, by the end
of the forecast period.



Morning satellite imagery shows a few holes in the overcast
ahead of a shortwave driving passing across Lake Erie. Some
brief clearing (PIT, BVI, LBE) is expected across the area this
morning as MVFR strato-cumulus temporarily breaks up. However,
this is expected to be short-lived as more extensive cloud cover
rebuilds as flow shifts off Lake Erie later this morning. Snow
showers associated with the lead wave will generally be confined
along and south of I-70, with Latrobe expected to see some brief
MVFR reduction in the 13-14Z time frame. Additional very light
snow from FKL-DUJ should diminish by mid-morning.

Otherwise the main aviation impact for today will be the wind,
which will vary from southwest to west into this evening with
occasional gusts upwards of 20 knots. A brief gust to 25 knots
may be possible where stronger subsidence (clearing) exists this

For the balance of the TAF period, MVFR stratocu cigs should
improve to VFR through the afternoon/early evening, as the low
levels briefly dry out under backing flow.

See no chance to the later period, as another shortwave trough
and warm front crosses the region tonight. MVFR/local IFR
conditions will re-evelop the area with patchy snow returning.
There could be some minor accumulations under an inch across the
northern terminals late tonight. Once again, deep mechanical
mixing, even during the nighttime hours, is expected to lead to
gusty surface winds toward the end of the period.

Cig restrictions are possible Saturday in warm, moist advection.
Restrictions are expected Saturday night and Sunday in rain and
snow with crossing low pressure, with restrictions remaining
likely through Tuesday under a broad upper trough.




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