PBZ issues Area Forecast Discussion (AFD) at Dec 10, 11:17 PM EST922
FXUS61 KPBZ 110417
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1117 PM EST Tue Dec 10 2024
.SYNOPSIS...
Precipitation chances will remain elevated through late
tonight. Rain will change to snow on Wednesday, with much colder
temperatures expected through Thursday. Seasonable temperatures
and rain chances return for the weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
KEY MESSAGES:
- Rain chances continue overnight with crossing low pressure and
a cold front
- Above average temperatures continue through tonight
-------------------------------------------------------------
Low pressure was currently across Lake Ontario, with a cold
front extending southward through western PA and WV. Expect only
a slow progression eastward with the front overnight, as another
wave of low pressure tracks NNE along it. POPs will increase
again from E-W as the next wave approaches, and as some jet
enhancement occurs late.
Previous discussion...
First round of showers is quickly moving northward through the
region. This area of rain is associated with a shortwave rushing
northeastward in the strong southwest flow aloft. Once this
wave exits this evening, the focus for additional rainfall will
turn to locations mainly south and east of Pittsburgh. Another
shortwave, caught up in the southwest flow aloft will cross the
region late tonight and spread precipitation westward as dawn
approaches.
With deep southwest flow, temperatures will continue to remain
10 to 15 degrees above average.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
KEY MESSAGES:
- Areas of rain continue tonight
- Approaching cold front will increase snow chances late Wed
morning
- Snow bands/snow squall potential increases early Thurs
- Cold wind chills and gusty wind late Wednesday and Thursday
-------------------------------------------------------------------
By early Wednesday morning, most of the region will likely
continue to remain in the warm sector under strong southwest
flow.
Rain may start to transition to snow in eastern Ohio as early
as 7am Wednesday. However, with a warm ground, low snow ratios,
and fast moving drier air, snow amount will likely create very
little impacts within the lower elevations during the Wednesday
morning commute.
Winter weather impacts could increase in the higher terrain
with stronger forcing between 18Z and 00Z Wed if snow ratios
increase above 12:1 and synoptic forcing persists. At the
moment, confidence is not high on the QPF amounts given the
quick transition from rain to snow. Therefore, the snowfall
amounts may be overdone in some areas. However, if cold air
advances quicker than projected, a Winter Weather Advisory may
need to be issued for the ridges of West Virginia for 3 inches
of snow.
Along with snow, strong wind gusts with a tight pressure
gradient may prompt headlines in the ridges of eastern Tucker
(where confidence is medium to high for Advisory criteria).
Gusts from 30-35 mph are likely in the lower elevations, with
gusts 40-50mph across the higher terrain.
There will likely be a quick period of quiet, dry weather with
lingering cold conditions early Thursday morning. However, a
number of Hi-Res guidance ensembles suggest convection snow
showers advancing into eastern Ohio/western PA between 01Z and
06Z Thurs morning. The snow squall parameter under the NAMs
peaks in intensity in portions of the area (mostly south of
I-80) and could prompt 0.5 to 1 inch snowfall rates.
Fortunately, these conditions are expected when the volume of
traffic is expected to be low across the region (12am to 4am).
The threat for convection snow showers will likely decrease
after 7am as the shortwave exits east.
Temperatures are expected to remain nearly steady through the
day, as 850 mb temperatures drop to between -16 and -18 deg C.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Temperatures return to seasonable levels Friday into Saturday
- Precip chances remain elevated Saturday evening into Sunday
-------------------------------------------------------------------
Confidence is increasing that warm weather returns Friday into
Saturday as ridging buildings over the Ohio River Valley as a
new trough digs over the Great Plains. Afternoon high temps will
range 3 to 5 degrees above average on Saturday.
Along with warm weather, expected precip chances to increase
Saturday afternoon into Saturday evening as the trough ejects
north into the Great Lakes. Precip chances decrease late Sunday
under ridging and incoming dry air.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
A frontal system will continue to move into the region this
evening and overnight. As rain develops and moves into the area,
cigs will continue to drop to below IFR conditions in most
cases. In fact, NBM probs are giving 70% to 90% chance of below
1 KFT cigs. Expect this to continue through the overnight and
into the coming day. Impacts will increase with the change over
to snow through the middle of the day as vis will drop in the
heavier snowfall. Winds are expecting to gust from the west
after frontal passage with some gusts reaching 25 knots.
Outlook...Dry air begins filtering in by Thursday and will
bring VFR conditions back to the area as clouds erode.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Hefferan
NEAR TERM...WM/Hefferan/22
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Cermak/Shallenberger
Source:
PBZ issues Area Forecast Discussion (AFD) at Dec 10, 11:17 PM EST---------------
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