788
FXUS61 KPBZ 191440
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
940 AM EST Sun Jan 19 2025

.SYNOPSIS...
Impactful snow possible for northern West Virginia and the ridges
of southwest Pennsylvania through the coming day, followed by
an extreme cold outbreak Monday through Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Snow expected through tonight, with the heaviest
  accumulations expected in the ridges and areas south and east
  of Pittsburgh.
- Winter Storm Warnings and Winter Weather Advisories are in
  effect through Monday.
- Temperatures continue to fall, with wind chills eventually
  dropping below zero tonight.
--------------------------------------------------------------------

930am update...
Latest radar imagery shows initial snow banding developing just
south of the Pittsburgh metro, with a general axis from far
southeast Ohio through the Laurel Highlands. Based on this
positioning and analysis of latest hi-res model data, the Winter
Storm Warning was expanded slightly north to include the higher
elevation locations of Fayette and Westmoreland (PA) counties;
additionally, the Winter Weather Advisory was expanded to
include Wetzel (WV) and Greene (PA) counties as well as the rest
of Westmoreland (PA) county.

These latest headlines and snowfall forecast follow the
slightest northward trend of the heavier snow band while also
attempting to narrow its width of impact. This shift should
slightly increase totals for the previously advised/warned areas
by 1 to 2 inches, with more minor fluctuations for non-
highlighted zones to the northwest.

Rest of the Discussion....

A deep mid-level trough will shift from the Mississippi River
Valley towards the Mid-Atlantic today and promote cyclogenesis
of a surface low southeast of the region. The combination of jet
dynamics and frontogenetic forcing will result in a fairly
narrow band of moderate to heavy snowfall now through late this
afternoon for areas mainly south of east of Pittsburgh. Ideal
moisture depth, upward motion and thermal profiles will favor
0.5" to 1"/hr snowfall rates in this band through the afternoon.
Please see section above for further details on placement of
Winter Storm Warnings and Winter Weather Advisories.

As the surface low kicks out to the Atlantic Ocean and the upper
trough axis moves overhead late this afternoon, banded snowfall
is expected to leave the area and gradually be replaced by
scattered snow showers. Though lake waters are limited due to
some ice coverage, enough open water remains to enhance the
moisture content while lapse rates steepen amid strong cold
advection with northwest flow in the post-frontal environment.
Though accumulations will become more isolated, lowland areas
may see an additional 0.5-1" of snowfall while enhanced
orographic lift will favor 2-4" more accumulations in the higher
terrain. Overall, event totals will be around 1" for northwest
zones and gradually increase to 6-9" (with locally higher
amounts possible) in the higher terrain SE of Pittsburgh.

While snow showers will become more scattered to isolated
overnight, strong cold advection and gustier wind is expected to
drop area temperature into the single digits with likely -10
degree wind chills (or lower). As a result, a Cold Weather
Advisory and Extreme Cold Warning are in effect to account for
this significantly cold air.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
KEY MESSAGES:

- Arctic outbreak with dangerously cold temperatures and wind
  chills likely coming through midweek.
- Extreme Cold Warning for ridges and Advisory for lowlands
  issued.

--------------------------------------------------------------------

EXTREME COLD MONDAY THROUGH WEDNESDAY MORNING...

Confidence has increased enough on dangerous cold with significant
impacts to go ahead and upgrade the ridges to an Extreme Cold
Warning and the rest of the area to an Advisory. Extremely low
temperatures and wind chill temperatures are expected to impact
the region Monday through Wednesday. Arctic air will dip down
out of far northern Canada across the eastern United States
starting tomorrow morning. The cold impacts through at least
Wednesday morning remain high confidence. There is high
agreement among ensemble clusters of the 500mb height and
temperature trends of deep troughing across the eastern CONUS,
dipping temperatures as low as 35 degrees below normal.

Confidence has changed that the coldest/lowest wind chill
may be Wednesday morning with the initial intrusion of arctic
air with the clear skies. Still Monday and Tuesday will feature
the initial push of the cold air with the only locations having
high confidence of warning criteria being the ridges. Thus, the
warning was issued for the ridges with an advisory everywhere
else and through the entire period through 18Z Wednesday. The
northern counties (Mercer, Venango, and Forest) need -25
wind chill to verify a warning, everywhere else needs -20. Thus
will need to upgrade some of the Advisory areas when Tuesday
night comes around.

Given the complex terrain and micro-meteorological cold air drainage
processes, low temperatures will likely be variable across the area
with the coldest pockets in sheltered valleys. Exposed ridge tops
may be a bit warmer, but also exposed to the wind. All in all, low
temperatures in the high negative single digits and low negative
teens with wind chills as low as -15F for the lowlands and -20F
for the ridges at least through Tuesday morning. Much colder
temps/wind chills is likely by Wednesday morning. It is also
worth mentioning that the Arctic air mass in place will
certainly take advantage of any residual moisture in the region
and flurries are likely intermittently through the 3 day period.

We recommend beginning to prepare for this cold conditions now.
Unprotected pipes can freeze and burst. Prolonged exposure to the
cold may lead to hypothermia. Frostbite can occur in as little as 30
minutes for exposed skin. It is encouraged to bring movable plants
indoors. Extreme care is encouraged for the protection of pets and
animals. Rescheduling any events, especially outdoor events, is
encouraged.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
KEY MESSAGES:

- There will be some warming by the end of the week.

--------------------------------------------------------------------

The potential for the cold wanes during the day on Wednesday.
The GEFS dominated ensembles showing a brief bout of shortwave
rejoining bringing temperatures up to the high 10s, while the
Euro and Canadian ensembles hold on to the cold with continued
highs in the single digits. On Thursday morning under the
surface high, efficient radiative cooling with light wind is
expected to drop wind chill temperatures close to advisory
criteria, however, cloud cover will prevent those temperatures
from getting too cold. With the bimodal solution, the potential
is there for a need of an advisory but will address it as the
time approaches.

By the end of the coming week (Thursday, Friday, Saturday),
there is still high confidence that ridging builds in and warms
high temperatures into the low 30s and upper 20s with lows in
the low 20s to upper 10s, which is still a hare below average.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
The next shortwave and surface low will approach from the
southwest this morning and slowly spread snow into the region
through 18z. Variance in positioning of the heaviest snow bands
remains large, which will impact snowfall rates/intensity as
well as degree of restrictions. Initially on the wetter side,
the heaviest snow (with rates that could approach 1"/hr) is
favored SE of KPIT with a general axis from KMGW to KLBE (and
areas SE of that line). This area also has higher confidence in
prolonged 1-2 mile visibility with periods of 1/2 mile or less
visibility. By late Sunday afternoon a trend towards more
showery snow will be seen, with lake enhancement and upslope
flow being the driving factors.

Snow will diminish Sunday night as wind backs more westerly,
though localized lake-enhanced snow showers may persist. General
improvement is expected by Monday morning.

Outlook...
Arctic temperatures arrive Sunday night and remain in place
through Wednesday behind this exiting system. Expect a return of
VFR conditions, but periods of gusty wind and prolonged sub-
freezing temperature that includes many hours with negative wind
chills. There is a low probability for a weak system to pass
Tuesday evening that may foster areas of light snow and cig/vis
restrictions.

&&

.CLIMATE...
A period of anomalously cold weather is expected to pass Monday
through Wednesday that will challenge many standing January
temperature records. Attached below are the standing
climatology for local sites. Pittsburgh has a full record,
while other sites are partial records and may not be fully
reflective of historical temperatures:

January 20th:         High Minimum       Low Minimum
Pittsburgh, PA         1F  (1985)        -18F (1985)
Wheeling, WV           13F (1940)        -1F  (1940)
Morgantown, WV         3F  (1985)        -17F (1985)
New Philadelphia, OH  -3F  (1994)        -22F (1994)
Zanesville, OH        -2F  (1985)        -17F (1985)
DuBois, PA            -2F  (1985)        -19F (1985)

January 21st:         High Minimum       Low Minimum
Pittsburgh, PA         5F  (1984)        -18F (1985)
Wheeling, WV           12F (2000)        -2F  (1924)
Morgantown, WV         2F  (1985)        -18F (1985)
New Philadelphia, OH  -8F  (1985)        -19F (1985)
Zanesville, OH         7F  (1985)        -22F (1984)
DuBois, PA             0F  (1985)        -22F (1985)

January 22nd:         High Minimum       Low Minimum
Pittsburgh, PA         10F (1961)        -14F (1936)
Wheeling, WV           11F (2014)        -4F  (2014)
Morgantown, WV         11F (2014)        -5F  (1984)
New Philadelphia, OH   5F  (1984)        -15F (1994)
Zanesville, OH         13F (2014)        -11F (2011)
DuBois, PA             8F  (2013)        -11F (1984)

Below is the lowest daily high and daily low temperatures of the
21st century. This encompasses all days of all months running
from January 2000 to present:

                      High Minimum       Low Minimum
Pittsburgh, PA         4F  (01/07/2014)  -10F (01/17/2009)
                                              (02/20/2015)

Wheeling, WV           5F  (01/07/2014)  -10F (01/07/2014)

Morgantown, WV         7F  (01/07/2014)  -9F  (01/28/2014)
                           (01/28/2014)       (01/29/2014)

New Philadelphia, OH   6F  (01/16/2009)  -18F (01/28/2014)
                           (01/28/2014)
                           (02/15/2015)

Zanesville, OH         6F  (01/28/2014)  -20F (01/29/2014)

DuBois, PA             0F  (01/07/2014)  -17F (02/16/2015)

In addition, Pittsburgh has not seen a daytime high below 4F
since January of 1994. Pittsburgh has also has not seen 2
consecutive days of high temperatures less than 10F since
January of 1997. If you extend this statistic to 3 days, you
would have to go back to February 1899.

The last time Pittsburgh`s minimum temperature was less than or
equal to -5F was December 2022. Last time it was below or equal
to -10F was February 2015. For 2 consecutive days of lows less
than or equal -10F, you would have to go back to January of
1994.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Cold Weather Advisory from 1 AM Monday to 1 PM EST Wednesday
     for PAZ007>009-013>016-020>022-029-031-073-075-077.
     Winter Weather Advisory until 9 AM EST Monday for PAZ031-073-
     075-078.
     Winter Storm Warning until 9 AM EST Monday for PAZ074-076.
     Extreme Cold Warning from 1 AM Monday to 1 PM EST Wednesday
     for PAZ074-076-078.
OH...Cold Weather Advisory from 1 AM Monday to 1 PM EST Wednesday
     for OHZ039>041-048>050-057>059-068-069.
WV...Cold Weather Advisory from 1 AM Monday to 1 PM EST Wednesday
     for WVZ001>004-012-021-509>511.
     Winter Weather Advisory until 9 AM EST Monday for WVZ012-021-
     509.
     Winter Storm Warning until 9 AM EST Monday for WVZ510>514.
     Extreme Cold Warning from 1 AM Monday to 1 PM EST Wednesday
     for WVZ512>514.

&&

$$

SYNOPSIS...WM
NEAR TERM...Frazier
SHORT TERM...Shallenberger
LONG TERM...Shallenberger/Lupo
AVIATION...Frazier
CLIMATE...