577
FXUS61 KPBZ 192042
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
342 PM EST Sun Jan 19 2025

.SYNOPSIS...
Heavy banded snow across the Laurel Highlands will shift east of
the area this afternoon, with scattered mostly light snow
showers continuing through Monday morning. Dry weather and
extreme cold will grip the region through Wednesday before
temperature moderates at the end of the week.

&&

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

- Peak snowfall rates will diminish over the Laurel Highlands
  through 4pm.
- Transition to scattered snow showers expected late this
  afternoon into early Monday morning.
- Combination of cold air and gusty wind will create negative
  wind chills Monday.
--------------------------------------------------------------------

As noted in the prior discussion, day advection has undercut the
synoptic snow shield, with the heaviest frontogenetical
synoptic banding clearing the area to the east. Based on a 17Z
ACARS sounding, we are beginning to see low-level
destabilization in cold advection with a saturated adiabatic
layer around 850mb. We expect the depth of the unstable layer to
increase through the arctic frontal passage this evening and
overnight. This will result in bands of convective snow showers,
but flow is expected to be progressive enough to result in
minimal totals. Around 1" to 2" of additional snow may be
possible on the highest end for areas hit multiple time with
dry, fluffy, high-ratio convective snow. On radar, coverage
continues to increase off of Lake Erie, and the most potent of
the snow bands along the arctic front itself has observed
visibilities below 1/2 mile and is expected to arrive in the
forecast area this evening before departing early tomorrow
morning.

Probabilities of low-visibility snow with additional
accumulations remain highest in the I-80 corridor, but low
visibility showers remain possible anywhere within the region.
With temperatures dropping into the 10s, snow will easily be
able to stick to roads and water may refreeze, making travel
slick on untreated and treated roads. Motorists should be
prepared for changeable visibility and road conditions if
traveling through this evening. Changes in visibility and slick
roads with snow showers may lead to accidents.

.. Previous Discussion ..

Moderate to heavy snow within frontogenetic banding across the
Laurel Highlands will continue to shift east through 5pm in
conjunction with the upper trough axis/surface low movement.
Until it exits, 1-2"/hr rates that have been reported will make
travel difficult through the higher terrain of southwest PA and
northeast WV. Dry advection is being noted to the west that is
undercutting the synoptic snow shield, causing a reduction in
snowfall rates generally west of the Winter Storm Warning areas.
There is a potential for a lull in accumulations (with the peak
past) as amid the environment transition.

The transition will be characterized by increasing northwest
flow behind the upper trough axis that is burnished by strong
cold advection. Steepening lapse rates and enough open lake
waters (with fetches from both Lake Michigan and Lake Erie) is
expected to create scattered snow showers this evening through
early Monday morning. Hi-res model guidance shows large
variations in lake enhanced bands and the influence of vort
advection within NW flow aloft, making it difficult to pinpoint
additional snow accumulations. On average, lowland areas should
see less than 1" (90% probability) of additional accumulation
despite ~20:1 SLRs due to the transient nature of the showers
and a fairly rapid backing of boundary layer winds to the west.
Orographic lift is expected to aid slightly higher accumulations
for the Warned terrain locations, but snowfall may be spotty
with rates generally less 0.5"/hr.

The aforementioned cold advection will also combine with breezy
wind from deeper mixing to create negative wind chills by the
Monday morning commute. Though increasing subsidence and dry
advection will clear clouds and end snow by Monday afternoon,
little diurnal heating will keep daytime air temperature near or
below 10 degrees and negative wind chills.

&&

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

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

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

     EXTREME COLD MONDAY NIGHT THROUGH WEDNESDAY MORNING...

Dangerously cold temperatures are expected throughout the short term
period as an anomalously deep trough over eastern North America
opens the door for arctic air to make its way from northern Canada
into the eastern CONUS. Locally, temperatures will hover 20 to 25
degrees below normal for this time of year, with Tuesday morning
starting out near or slightly below zero, increasing to the upper
single digits to low teens Tuesday afternoon, and then plummeting to
around -10 degrees Tuesday night. Extreme Cold Warnings are in
effect for the ridges of southwest PA and northern WV where wind
chills will periodically dip to -20 to -25 degrees. A Cold Weather
Advisory is in effect for the rest of the area with wind chills in
the -10 to -20 degree range. However, we will need to monitor trends
for low temperatures and wind chills Tuesday night into early
Wednesday morning when some lowland areas could exceed Extreme Cold
Warning criteria (-20 degrees south of I-80, -25 degrees north of
the interstate) and upgrades may be needed. Flurries will be
possible during the day Tuesday if there is enough low-level
moisture, though with little to no accumulation.

We recommend beginning to prepare for these 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. Check in routinely with vulnerable friends
and family. Bring movable plants indoors. Extreme care is encouraged
for the protection of pets and animals. Rescheduling any events,
especially those taking place outdoors, is also encouraged.

&&

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

- There will be some warming by the end of the week but
  temperatures remain below normal through at least Saturday.
- Precipitation chances may increase Friday into the weekend as
  another upper trough approaches from the west.

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

Very cold temperatures hang on through Wednesday night, with
highs Wednesday afternoon in the upper single digits to low
teens and nighttime lows in the lower single digits to near
zero (wind chills near or slightly below zero). Gradual warming
is expected thereafter to close the week as global ensembles
are in fair agreement that the eastern CONUS trough departs and
we see weak height rises in response to another upstream trough
digging into the central CONUS. Temperatures rebound into the
20s Friday and 30s next weekend. Depending on the eventual
progression of the upstream trough, this warming could also be
accompanied by a round of increasing precip chances.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
IFR/LIFR conditions continue generally along and SE of a LBE-HLG
line as a shortwave trough crosses the area, and as an area of
frontogenesis set up across that region. Snowfall rates of 1
inch per hour have been reported as well. This area of
frontogenesis should shift eastward through mid afternoon, with
slowly improving conditions and diminishing snowfall rates.

To the north of this area, mainly MVFR conditions are expected
with light snow and/or cigs. The steady snow will transition to
scattered snow showers this evening as the initial trough axis
exits, and NW flow develops. A few heavier snow showers are
possible this evening, and included a TEMPO mention at the
airports most likely to be affected, including PIT.

Snow showers should gradually diminish overnight and early
Monday as the boundary layer flow backs to the WSW, and
moisture in the dendritic growth zone decreases. MVFR cigs are
expected to continue with moisture below a temperature
inversion. W wind is expected to become gusty on Monday, with
gusts around 20kt.

Outlook...
VFR is expected to return Monday evening as high pressure builds
in. A reinforcing trough returns MVFR cig restriction potential
Tuesday, before VFR returns Wednesday under high pressure. Snow
shower and restriction potential returns with a Friday cold
front.

&&

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