PBZ issues Area Forecast Discussion (AFD) at Jan 24, 11:10 PM EST
785
FXUS61 KPBZ 250410
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1110 PM EST Fri Jan 24 2025
.SYNOPSIS...
Dry and cold weather is expected tonight under high pressure.
Temperatures moderate this weekend, but a fairly weak impulse
with another round of snow Saturday afternoon into Sunday may
produce an inch or two of accumulation north of US-422.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
KEY MESSAGES:
- Mainly clear overnight with a return to single-digit lows.
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A ridge of high pressure will maintain dry weather overnight.
Most of the stratocu has eroded under the high, and with backing
flow aloft.
A return to single-digit low temperatures tonight is likely for
most of the area. Overall light wind will keep wind chills
largely in check, but a puff on the ridges may drop minimum
apparent temperatures into the -5 to -10 range late tonight.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
KEY MESSAGES:
- Light snow mainly north of Pittsburgh Saturday afternoon into
Sunday.
- Temperatures moderate into Sunday before briefly dropping off
again Sunday night.
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The surface ridging should keep conditions largely dry Saturday
morning. Warm advection ahead of a weak warm front, slated to
arrive during the afternoon mainly north of Pittsburgh, should
push 850mb temperatures into the -6C to -9C range. A slight push
towards more seasonable daytime highs is expected, with the
freezing level possibly breached near and south of I-70 both
Saturday and Sunday.
Along with the front, weak, flat 500mb troughing with embedded
vorticity lobes should increase snow shower chances mainly north
of Pittsburgh Saturday afternoon into Sunday. There does not
appear to be much of a convective element to this snow.
Model/ensemble soundings show little potential for steep low-
level lapse rates or CAPE and the snow squall parameter is
essentially zero. However, in the more favored northern
counties, there do appear to be periods of sufficient moisture
in the dendritic growth zone, along with fairly modest lift.
Snow ratios, although dropping a bit into the 15:1 range with
time, still may combine with .05 to .15 inch of liquid
equivalent QPF to produce 1 to 2 inches of snow north of US-422
from Saturday afternoon through Sunday morning. This is more or
less in line with mean HREF expectations through the period.
Again, with the lack of convective elements, think that the
higher-end HREF totals of over 3 inches in spots do not appear
attainable at this time. From Pittsburgh south, more isolated
activity may create a dusting, perhaps up to an inch on the
ridges with a modest upslope component.
A weak cold frontal passage on Sunday should bring a brief shot
of cold advection, dropping temperatures back below normal
Sunday night as snow showers end and surface ridging returns.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
KEY MESSAGES:
- Near-normal temperatures early next week are likely to sink
below normal by the mid to late week period.
- Rounds of weak disturbances may produce scattered snow
chances.
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The next shortwave is forecast to dip across the Great Lakes Monday
night into Tuesday, reinforcing the larger trough over the northeast
CONUS and possibly continuing snow shower chances into Wednesday.
Ensemble clusters remain fairly evenly split on amplification, with
some 15-20 dam variance in area 500mb heights between them. The
deeper solutions, with better forcing, are tending to show higher
QPF solutions. That said, even the deeper solutions do not appear to
threaten more than borderline advisory-criteria snow at this
time. Such headlines would likely be limited to north of I-80
and/or the ridges. Currently, 40-60% NBM 48-hour chances of one
inch accumulation are still generally limited to these
locations. These may ultimately prove to be a bit low, but a bit
better model consolidation would help to increase confidence in
snow totals. There is decent confidence in another temperature
moderation after the brief Sunday night cooldown, with values
reaching close to normal.
Variance between model cluster continues to increase
thereafter. It appears that additional shortwave energy will
attempt to sharpen the larger trough during the Wednesday night
to Friday period. However, fairly large differences in shortwave
timing and strength lend little confidence to the overall
pattern. For now, the higher- confidence call is for a return to
below-normal temperatures during the second half of next week,
with less confidence in the potential for widespread snow shower
activity. NBM means will be followed for now until a more
coherent solution emerges.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
Much of the stratocumulus has passed through the area and only a
lingering strip of it remains over northern PA. Thus will
expect improving conditions through the overnight as cigs
slowly lift and VFR conditions prevail. The NBM gives some 50%
to 60% probs of improving conditions overnight.
By tomorrow morning in the 14Z to 20Z timeframe, winds will
increase from the southwest with some gusts reaching 20 knots.
This will be in advance of the next shortwave trough. With this
will be some scattered snow showers that will have the potential
to drop vis down to IFR at times, especially in the northern
terminals. Expect MVFR/IFR conditions to begin at some sites by
20Z and end the TAF period. The activity will be largely to the
north and MGW could remain VFR through the period.
Outlook...
Snow showers are expected to continue on Sunday with some
restrictions possible due to lingering stratocumulus. VFR
conditions are expected to return by Monday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...WM/CL
NEAR TERM...WM/Rackley/CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Shallenberger
Source: PBZ issues Area Forecast Discussion (AFD) at Jan 24, 11:10 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501250410-KPBZ-FXUS61-AFDPBZ)
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