Mount Lebanon, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

316
FXUS61 KPBZ 180226 CCA
AFDPBZ

Area Forecast Discussion...CORRECTED
National Weather Service Pittsburgh PA
926 PM EST Fri Jan 17 2025

.SYNOPSIS...
Rain and snow returns late tonight and Saturday. Impactful snow
possible for the higher terrain of West Virginia this Sunday
and Sunday night, followed by an extreme cold outbreak next
Monday through Wednesday. A warming trend is expected by at
least Thursday of next week.

&&

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

- Rain and snow chances increase overnight
- Slight chance of freezing rain in the morning
- Rain continues Saturday, with a mix of snow and rain north of
  PIT
--------------------------------------------------------------------

Dry weather is expected through the rest of the evening under
shortwave ridging. Clouds will begin to increase overnight in
warm advection ahead of the next approaching shortwave. This
warm advection should also result in temperatures slowly rising
overnight as well.

Moisture and ascent will increase late tonight as an initial
shortwave trough tracks northeastward from the Midwest. A low
level jet should also provide additional ascent as it crosses
the region late tonight and early Saturday morning. Model
soundings, 850mb temperatures, and critical thicknesses indicate
the precipitation will be mainly rain roughly south of Rt 422 at
the onset of the precip, with mainly snow to the north and in
the ridges. Evaporative cooling could also result in some snow
or a rain/snow mix south of Rt 422, especially early.

While road temperatures warmed today with highs in the 30s and
40s, recent sensor data indicates some of these areas were back
below freezing. Added at least a slight chance of freezing rain
early Saturday morning, though this will be dependent on
road/surface temps, as air temperatures should be in the mid
30s. Any mix should change to rain south of RT 422 by mid
morning, with snow mixed with rain to the north. Snow
accumulation to the north should be limited to less than an inch
with temperatures above freezing. A surface cold front will then
approach and cross the region late Saturday afternoon,
continuing the precip chances.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
KEY MESSAGES:

- Slow cold front passage with another disturbance riding along
  the high terrain.

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

As the front dips across the area, temperatures are expected to
very gradually decrease across the area through the period. This
will mean that all snow will be the predominant precipitation
type for Saturday night and Sunday.

There has been increasing confidence in an impactful winter
system for the West Virginia ridges as another cyclone develops
and moves up the front, shoveling moisture back into the cold
sector of the low for the high terrain.

For now, most of this snow is expected to start Saturday night
with the highest rates Sunday morning, followed by orographic
enhancement in northwest flow Sunday into Sunday night. The
highest QPF will likely fall in a deformation zone. Confidence
in there this sets up is quite low, with some guidance pushing
into the lowlands a but, and some well east of the forecast area.
Because models poorly capture this, totals may be overdone
outside of the zone, and underdone within the zone. For
awareness, a watch was hoisted for the WV ridges where
orographic influence is the highest, and the highest
probabilities (30% to 50%) of heavy snow are forecast. From
start to end, snowfall ratios will go from almost 10:1 to 20:1
as temperatures cool, becoming as low as the single digits
Monday morning. More on the extreme cold is included in the long
term. For the worst- case scenario (90th percentile), 6"+ is
possible for the ridges and 3"+ for the lowlands. On the low
side, low end advisories or even less than 3" are possible for
the ridges, depending on storm track.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
KEY MESSAGES:

- Snow showers continue on Sunday and Monday in northwest flow.
- Arctic outbreak with dangerously cold temperatures and wind
  chills likely next week.

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

     EXTREME COLD MONDAY THROUGH WEDNESDAY...

Confidence has increased enough on dangerous cold with
significant impacts to issue an Extreme Cold Watch. 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
beginning Sunday night.

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. Long-range guidance (NAEFS) has 850mb and 700mb
temperatures early next week near the 1st percentile
(temperatures this time of year are warmer than this 99% of the
time).

Confidence has increased that the coldest daytime high of the
period may be Monday (middle single digits) with the initial
intrusion or arctic air, but clear skies and the potential for
decoupling and cold air drainage overnight mean that the coldest
morning may be Tuesday and Wednesday morning. 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 -25F for the lowlands
and -30F for the ridges.

Forecast confidence decreases Wednesday, with GEFS dominated
ensembles showing a brief bout of shortwave rejoining bringing
temperatures up to the high 10s, while the Euro ensembles hold
colder with continued highs in the single digits. Under the
surface high, efficient radiative cooling is still expected to
drop wind chill temperatures close to advisory criteria Thursday
morning. Even with the bimodal solution, the watch extends
through 15Z to account for one mode and also the cumulative
impacts of the extreme cold to this point.

The time to begin preparing is 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.

By the end of next 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 /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected to continue for the bulk of the
night, although clouds will thicken and lower with time as
moisture aloft increases on southwest flow. A 40 knot low-level
jet above a surface-based inversion will introduce low-level
shear concerns between roughly 03Z and 12Z.

Precipitation returns in eastern Ohio by 09Z and will overspread
the region by mid-morning ahead of an advancing cold front. HREF
probabilities show high confidence in areawide MVFR conditions
by 13Z, and then IFR at most terminals by 16-17Z. MGW may be a
holdout for a bit with low-level southeast downslope flow, but
even that airport is likely to sink to the IFR threshold during
the afternoon. Precip type may begin briefly as snow or a
rain/snow mix north of PIT, but all rain is expected by midday
with moderate confidence.

The cold front sweeps across the region after 18Z, with some
reduction in precipitation coverage, but mainly IFR ceilings are
expected to linger through sunset. Lingering precipitation is
expected to change back to snow from west to east after 21Z or
so.

Wind will veer with time through the TAF period, from S/SE
initially, to SW during the Saturday daylight hours, and finally
to W and NW behind the front.

Outlook...
Restrictions are possible in snow through Sunday. A strong
arctic front will bring bitter cold temperatures near or below
zero Monday morning through Wednesday night.

&&

.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...Extreme Cold Watch from late Sunday night through Thursday
     morning for PAZ007>009-013>016-020>022-029-031-073>078.
OH...Extreme Cold Watch from late Sunday night through Thursday
     morning for OHZ039>041-048>050-057>059-068-069.
WV...Extreme Cold Watch from late Sunday night through Thursday
     morning for WVZ001>004-012-021-509>514.
     Winter Storm Watch from late Saturday night through Monday
     morning for WVZ512>514.

&&

$$

SYNOPSIS...WM/Milcarek
NEAR TERM...WM
SHORT TERM...Milcarek
LONG TERM...Milcarek
AVIATION...Cermak/CL
CLIMATE...Milcarek