PBZ issues Area Forecast Discussion (AFD) at Dec 6, 12:49 PM EST921
FXUS61 KPBZ 061749
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1249 PM EST Fri Dec 6 2024
.SYNOPSIS...
Snow showers and gusty wind will gradually diminish this
morning, with snow lingering longest north of I-80 into the
afternoon. Building high pressure will shut down the lake
effect for the weekend with drier weather and gradually warming
temperatures into next week. The next widespread chance of rain
comes Monday with low pressure.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Lake Effect Snow Warning remains in effect as snow continues
along the I-80 corridor into the afternoon.
- Gusty wind through the overnight.
-------------------------------------------------------------
A few narrow bands of light to moderate snow have persisted in
localized convergence areas this morning extending southeast
off of the lakes as far down as Greene and Fayette Counties.
Amounts thus far have overall been light, and generally 1-3
additional inches are possible for those under the bands. We
await the backing of boundary layer flow to a more westerly
component that will shift the bands out of our area and extend
along the lakeshore towards Buffalo. This is a high confidence
scenario by early this afternoon according to the HREF 925/850
mb mean flow and, when this does so, the remaining winter
headlines up north will be allowed to end.
As winds back more with upper trough departure, light snow
coverage will lessen and give way to a mostly cloudy day across
the area. Scattered, light lake effect snow may linger through
the afternoon north of I-80, but additional accumulation
probabilities for measurable snowfall in our area through
tonight is ~10%. Low level flow has weakened since yesterday as
has cold advection aloft, so wind gusts will be less today
despite efficient mixing; probabilities for >30 mph is only
30-40%.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
KEY MESSAGES:
- Dry for the weekend, with low-probability, light snow
possible north of I-80.
- Slight warming on Saturday, then above-average temperature on
Sunday
-------------------------------------------------------------------
Height rises and building sfc high pressure with drying lower
levels will maintain dry weather on Saturday and Sunday. The
exception may be a few light snow showers north of I-80 as a
shortwave crosses well to our north. These would bring at most a
light dusting to a few tenths to that area, with the
probability for accumulating snow at around 25%.
Southern portions of the region may see sunshine return Saturday
afternoon as clouds gradually erode from the south with dry
advection. Warm advection in southwesterly flow will help
rebound highs back above freezing with a 50-90% chance south and
west of Pittsburgh, highest across southeast Ohio. By Sunday,
deeper southerly flow amid scattering cloud cover and better
insolation will help boost afternoon highs above normal, with
much of the region confidently back in the mid-40s.
Gusty winds, though much diminished from Thursday, will continue
through the weekend as a tight pressure gradient remains and
25-35kt 850mb flow mixes down during the daytime hours. NBM
prob max daily gust suggests 20-30 mph.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
KEY MESSAGES:
- Above average temperatures favored for the first half of the week.
- Temperatures tumble for the latter half.
-------------------------------------------------------------------
Another upper wave digs across the northern CONUS as surface low
pressure develops across the Mississippi Valley with primary
uncertainty stemming from a question of phasing and slightly lesser
of timing in regard to the upper pattern. One solution presents the
wave phasing with the parent trough axis further to the north.
Another solution suggests no phasing, but a deeper wave. Both of
these solutions would paint a quicker onset of precipitation Sunday
evening into our eastern Ohio counties. The other camp shows a more
amplified pattern with a slower and weaker encroaching wave
which would delay precipitation onset to the overnight hours
Sunday night. The takeaway message is that the occurrence of
rain for the beginning of the week is high confidence, but the
timing of it is low confidence. The goal posts sit around an
inch on the high end and a quarter inch on the low end.
That trough will be slow to depart as all ensemble clusters suggest
it lingering through mid week at least, but with more significant
evolution differences. This suggests at least periodic rain chances
driven by subtleties in the flow and another potential, low-
confidence low pressure passage Tuesday into Wednesday.
Temperatures are favored to remain above average Monday and
Tuesday before tumbling back closer to normal by Wednesday.
Drier and cooler weather is favored by Thursday.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As expected VFR stratocu has developed in areas without higher
clouds. Stratocu is expected to clear by evening, though mid level
clouds in warm advection will quickly fill in.
Surface winds can be gusty through this afternoon, but at a lesser
clip than previous days. Most area terminals can gust between 15-20
knots.
Winds have backed to the WSW and the last of the snowfall is
fizzling and shifting to the north and east. FKL and to a lesser
degree DUJ stand a chance to see a return to MVFR restrictions in
these passing snow showers before 22z, when probabilities of
observing snow begin to rapidly decline.
Outlook...
Latest guidance shows probabilities of either FKL/DUJ
observing CIGs <3000ft between 00-12z Saturday remain very high
(>80%). Otherwise, VFR is expected through Sunday under a ridge of
high pressure. The nose of a stout low-level jet is expected to move
over the region after 00z Sunday and this could allow for some LLWS
concerns. Restrictions and rain return Sunday night through Tuesday
with crossing low pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Rackley
NEAR TERM...Rackley/MLB
SHORT TERM...Rackley/MLB
LONG TERM...Rackley/MLB
AVIATION...AK
Source:
PBZ issues Area Forecast Discussion (AFD) at Dec 6, 12:49 PM EST---------------
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