PBZ issues Area Forecast Discussion (AFD) at Dec 1, 8:36 AM EST695
FXUS61 KPBZ 011336
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
836 AM EST Sun Dec 1 2024
.SYNOPSIS...
The cold is here to stay. Periodic snow showers are possible
through most of next week. The best chance for widespread snow
will arrive midweek. Below normal temperatures into next
weekend.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Well below normal temperatures.
- Wind chills in the teens.
- Light snow possible in the WV ridges.
-------------------------------------------------------------------
Update...
Updated to increase cloud cover some this afternoon, as a
shortwave trough crosses, and convective temperatures are
reached. Expect scattered to broken stratocu to develop by mid
to late afternoon.
Previous discussion...
A shortwave trough will swing through the region this
afternoon. This trough will reinforce the cold air over the area
and increase low cloud cover across the north. Temperatures
remain well below normal.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
KEY MESSAGES:
- Well below normal temperatures with daily chances of snow
showers, mostly north and east of Pittsburgh.
-------------------------------------------------------------------
NW flow will increase tonight. This will drag low cloud cover
southward from northern PA and spread it across much of the
region by Monday morning. The NW flow will also increase the
risk for snow showers late tonight, with the best chance over
the I-80 corridor. The resultant snow looks to be light with
probs > 1 inch of 20-30% across the northern border of the
forecast area.
NW flow will continue throughout the day on Monday. This will
keep in the risk for lake enhanced snow showers with the best
chance over the I-80 corridor. Probabilities > 1 inch of snow
(40-60%)remain north of I-80. Probs > 0.1 inches (20 to 40%)
shift further south but remain north of PIT.
Temperatures Monday will be 10 to 15 degrees below normal.
The main trough axis will shift to the east on Tuesday. The
persistent NW flow will slowly back to the west. With this
change in wind direction, the threat for snow showers should
become confined to the I-80 corridor. At the surface, high
pressure will build into the Tennessee Valley. This increase in
subsidence and the loss of NW flow, should allow for some
sunshine on Tuesday. Temperatures will still remain well below
normal.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
KEY MESSAGES:
- Another disturbance arrives mid-week, with additional snow
chances, though forecast confidence still remains medium to
low.
-------------------------------------------------------------------
There is increasing confidence that a stacked low and reinforcing
cold shot arrives late week. Surface low positioning remains quite
uncertain with EPS, GEPS, and GEFS members; placement is centered in
between Lake Huron and the Hudson Bay by Thursday morning, with a
larger cluster of members favoring the southerly solution. A more
southern track would mean more forcing for snowfall, but exact
totals could be governed more by shortwave timing, which again, has
low predictability this far out.
At this time, the greatest probability of accumulation with the
system occurs Wednesday into Wednesday night. Chances of >3" of snow
are generally .50% northeast of the Pittsburgh metro and into the
ridges. There is a 30% chance of >6" in Jefferson (PA), Indiana,
Forest, and Clarion Counties. Additionally, the arctic front
may warrant watching for snow squall concerns.
Uncertainty increases drastically after this wave passes through as
some clustered ensemble attempt to reestablish ridging late
week and through the weekend, while other continue to allow
eastern troughing. The difference between these scenarios will
drastically affect the forecast. While both clusters favor below
average temperatures through the weekend, the key difference
will be wind direction. In ridging, winds back more westerly,
removing lake influence and with lower precipitation chances.
Should troughing continue, northwest flow could mean continued
lake enhanced snow, in the event that boundary layer flow
orients 320 to 330 degrees, snow banding is possible off of an
optimal Huron/Erie fetch, which is indicated by a sub-sect of
long range guidance.
&&
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR is expected for most of the day, though stratocu will
continue to develop as convective temperatures are reached, and
as a shortwave trough approaches the Upper Ohio Valley region.
MVFR cigs will continue this morning for HLG and MGW, where an
initial shortwave was resulting in low level moisture and light
snow/flurries. These cigs should increase to VFR by mid to late
morning as the initial shortwave exits, and mixing lifts cig
heights.
VFR stratocu is expected tonight as the wave crosses. MVFR is
expected at FKL and DUJ as some lake enhancement and low level
convergence develops as the wind veers more westerly for a brief
time north of I 80.
Outlook...
Lake Effect snow showers are possible north of I-80 on Monday,
especially for KFKL and KDUJ where restrictions are possible.
General VFR is expected for most of the area Tuesday, though a
westerly boundary layer flow could result in restrictions and a
few snow showers at FKL and DUJ.
Snow and gusty winds are expected Wednesday afternoon and
Thursday with the approach and passage of a cold front, and
subsequent cold advection and upper troughing.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...22
NEAR TERM...WM/22
SHORT TERM...22
LONG TERM...Milcarek
AVIATION...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Dec 1, 8:36 AM EST---------------
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