PBZ issues Area Forecast Discussion (AFD) at Nov 22, 3:02 AM EST156
FXUS61 KPBZ 220802
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
302 AM EST Fri Nov 22 2024
.SYNOPSIS...
Low pressure just east of the region will maintain areas of
snow and rain today. The low will slowly exit the region
Saturday, with dry weather returning Sunday. Rain chances return
with a Monday cold front. A series of disturbances will bring unsettled
weather for much of the rest of next week.
&&
.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:
- Snow this morning, changing to rain outside of the higher
terrain
- Significant snowfall expected across the higher terrain areas
------------------------------------------------------------------
A large upper low was centered across southern PA and MD, while
a surface low was centered over southern New England. The
surface low will rotate around the upper low, and will be
located across eastern PA this afternoon and evening. A surface
trough extending west of the low was across southern Lake Erie,
and will be moving southward this morning.
Snow is expected to overspread the region from north to south
this morning as the surface trough moves south,and additional
moisture and ascent rotate around the upper low. A strengthening
low level jet should enhance this ascent through the day.
Critical thicknesses, 850mb temperatures, and model soundings
indicate the snow will mix with and change to rain from north to
south later this morning and afternoon. The exception will be
across the higher terrain areas, where the precipitation will
remain all snow.
A quick accumulation of snow is expected this morning as the
initial area of precip moves across the region. There should be
a relatively short window for accumulation, as temperatures
begin to rise and the snow mixes with and changes to rain.
A period of heavy snow is expected across the Laurel Highlands
and the higher terrain areas of WV. Maintained the Winter Storm
Warning in these locations through tonight/Saturday, with
advisories through early this afternoon just outside of the
higher terrain where lesser snow amounts are expected. Snowfall
rates of around 1 inch per hour are likely to develop across the
ridges, with wind gusts also increasing to between 40 and 50
mph. The increasing wind, and saturation in the dendritic growth
region, should lead to these efficient snowfall rates. One
limiting factor could be the warm advection aloft limiting lapse
rates, though the orographic lift component could cancel out
this effect.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
KEY MESSAGES:
- Winter storm in the ridges ends Saturday
- Rain/snow chances end by Sunday
-------------------------------------------------------------------
The low is progged to become vertically stacked tonight across
eastern PA. Rain will continue for much of the area as
additional moisture and jet supported ascent rotate around the
low. The ridges will remain all snow, and some snow could mix
back in with the rain near and east of a FKL-IDI line. Snowfall
rates across the ridges should begin to diminish this evening as
the depth of the moisture decreases, wnd saturation in the
dendritic layer lessens. Gusty wind will continue, especially
across the ridges, with the low level jet in place.
Rain and snow should gradually end Saturday as the low exits off
of the East Coast. Wind should also gradually diminish through
this period as the surface pressure gradient begins to relax.
There could be a period of freezing drizzle across the highest
terrain areas of Tucker county WV as the dendritic growth region
dries, but low level moisture remains.
Saturday night and Sunday should be dry with seasonable
temperatures as a ridge of high pressure builds in.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
KEY MESSAGES:
- Dry on Sunday
- Cold front returns Monday and Monday night
- Unsettled again, especially with a mid to late week low
-------------------------------------------------------------------
Model ensembles indicate flat ridging will be across the region
early Monday, ahead of an approaching Central CONUS trough.
Developing surface low pressure ahead of the trough is expected
to track from the Midwest to the Lower Great Lakes region later
Monday and Monday night, pulling a cold front across the area.
Rain chances will increase through the day, peaking Monday
evening/night with FROPA.
The upper trough axis will follow on Tuesday, with continued
rain and snow chances mainly north of PIT, where better lift and
moisture is progged. Ensembles then indicate a trough will
track across the Central CONUS on Wednesday, as a surface low
begins to develop across the TN/lower OH valley region.
Increasing moisture and lift in SW flow ahead of the trough will
return rain and snow chances to the area late Wednesday and
Wednesday night. Precipitation is likely by Thanksgiving as the
trough approaches, and the surface low tracks across the
TN/lower OH valley, and toward the Mid Atlantic coast. Rain and
snow are both possible, depending on the track of the surface
low, and amount of warm advection across the Upper Ohio Valley
region. With increased uncertainty in the exact scenario by
late week, stayed close to the ensemble blends for the forecast.
&&
.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
A large-scale low pressure system will continue to impact
terminals over the next 24 hours. At the moment, there is a lull
in precip activity, isolated snow bands south of PIT may create
IFR vis briefly.
The next wave of widespread precipitation will be between 10Z
to 13Z as the center of the low over New York tracks west.
Although precipitation will start as snow initially, a
change over to rain will occur from north to south Friday
morning as warm air wraps around this mature system. Ceilings
will drop through MVFR to IFR around 12Z with high confidence
(HREF probs of 70-100% at all TAF sites). Visibility will
likewise drop to IFR in most cases (with possible occasional
drops to LIFR) with the rain/snow mix, with lingering mist
during precipitation lulls. Although flight conditions will
remain largely IFR through the afternoon, visibility may begin
to slowly improve as the rain changeover occurs, although ridge
areas are more likely to remain snow longer.
Wind gusts will also pick up Friday morning with the tightening
pressure gradient and improved mixing; 20 to 30 knot westerly gusts
are likely at most terminals through the day.
Outlook...
Restrictions are expected into Saturday as a series of low
pressure systems spin across the NE CONUS, bringing periods of
rain and snow showers to the area. VFR should return Sunday as
high pressure builds in.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 1 PM EST this afternoon for
PAZ009-016-073-075-077-078.
Winter Storm Warning until 7 AM EST Saturday for PAZ074-076.
OH...None.
WV...Winter Weather Advisory until 1 PM EST this afternoon for
WVZ021-509.
Winter Storm Warning until 7 AM EST Saturday for WVZ510>513.
Winter Storm Warning until 7 PM EST Saturday for WVZ514.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...WM
LONG TERM...WM
AVIATION...Hefferan
Source:
PBZ issues Area Forecast Discussion (AFD) at Nov 22, 3:02 AM EST---------------
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