Penn Hills, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

721
FXUS61 KPBZ 040636
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
136 AM EST Wed Dec 4 2024

.SYNOPSIS...
Widespread snowfall is expected Wednesday evening into Friday,
with greater than six inches likely along and north of the I 80
corridor. Strong wind gusts are also expected Wednesday night
through Thursday. Blowing snow along the ridges may reduce
visibility and make travel hazardous.

&&

.NEAR TERM /UNTIL NOON TODAY/...
KEY MESSAGES:

- Dry weather continues through this morning with below average
  temperatures
-------------------------------------------------------------

Boundary layer flow from the southwest and brief ridging have
eroded the stratocu layer for much of the region. Clouds hang on
(but are slowly eroding) east of Pittsburgh and along the
ridges where some moisture remains under a thermal inversion.
This, too, should largely erode through the overnight. Clearing
will be short-lived, however, as mid and high level clouds
increase through the overnight with warm advection aloft ahead
of the next shortwave across the Upper Midwest. Building cloud
cover and meager warm advection should help stall temperature
drops through sunrise.

Brief high pressure will keep dry weather in the forecast
through this morning ahead of our next snow-making system. More
robust warm advection through the daytime will help boost
temperatures west and south of Pittsburgh 5 to 10 degrees above
Tuesday.

&&

.SHORT TERM /NOON TODAY THROUGH THURSDAY NIGHT/...
KEY MESSAGES:

- Winter Storm Watch for the Allegheny Mountains and I-80
  corridor
- Winter weather impacts increase late Wed evening into Thu
  morning with a strong cold front
- Intense snow bands/squalls are possible Thursday morning
- Gusty winds are expected with the front Wed night and Thurs
- Lake effect/lake enhanced snow showers continue into Fri
- Wind chill values will be below zero in the higher terrain
  early Fri morning

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

A deep trough will dig across the Upper Midwest and into the
Great Lakes region on Wednesday as a strong surface low crosses
Ontario. Warm advection into the afternoon will boost daily
highs into the mid/upper 30s (though still below average).

As low pressure passes to the north, a cold front will cross the
region late Wednesday evening and into overnight time period.
There may be a brief period of wintry mix south of Pittsburgh
before Arctic air overtakes the region. Widespread snow showers
and dropping temperatures (by 10 to 15 degrees) are expected
between 7pm to 11pm Wednesday. Snow ratios will rapidly increase
from 8:1 to 16:1 in 6 hours. Therefore snow character will
start as wet and transition into a powder consistency.

With enhanced instability ahead of the front, 25J/kg to 50J/kg,
snow bands could be could considered "intense" and take on snow
squall characteristics. Based on the NAM, the snow squall
parameter is maximized between 06Z to 09Z across eastern
OH/western PA based on steep low-level lapse rates, strong wind
gusts, available instability, and enhanced low-level moisture
(70 to 90%) within 0-3km. Short-fused products (i.e. Snow Squall
Warnings) may be needed for drivers before or during the
morning rush hour.

Winter Storm Watches have been issued to cover the areas where
confidence is higher in lake effect bands, higher snowfall
totals from upsloping, and blowing snow.

Given a strong pressure gradient with a potentially closed
upper-level low, gusty winds are expected to start Wednesday
evening into Thursday with a passing LLJ (50-60kt). The
potential peak wind gusts are expected 5pm Wed through 4am
Thurs. However, lingering gusts may continue in the higher
terrain due to mountain wave activity. Areas that don`t get
upgraded into a Winter Storm Warning may need a Wind Advisory to
cover the threat of strong wind gusts (46+mph)

As the center of the low drifts north of New England, and
northwest flow increases, lake enhanced/lake effect snow showers
will likely continue late Thursday into Friday. Therefore, during
this entire event, snowfall amounts near I-80 could be close to
a foot in isolated areas under lingering bands.

&&

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

- Brief break later Friday before snow chances return for the
  weekend
-------------------------------------------------------------------

Snow showers are expected to taper off Friday and Friday night
as the trough exits and flow backs to the SW.

There is much higher uncertainty for the weekend, with high
pressure to our south. There is the possibility for another
wave to bring additional precipitation Saturday into Sunday,
but still little agreement on this. However, there is higher
confidence in a more robust system early next week. Regardless,
temperatures will remain below average through the period.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
As surface high pressure continues to build into the region,
all terminals are expected to achieve VFR by dawn across the
forecast area, although patches of VFR stratocumulus may
linger. Some terminals may hold onto MVFR conditions through 10Z
but should improve shortly thereafter.

VFR will continue into the mid-afternoon hours, although clouds
will begin to thicken and lower in advance of the next weather
system. Snow showers will begin to show up once again after 18Z,
perhaps mixing with rain at the onset before changing to all
snow by evening. Ceilings will drop into the MVFR category
across much of the region by the end of the TAF period; the HREF
has 70 to 100 percent of such by 00Z at all terminals save MGW
and LBE.

A tightening pressure gradient will allow for gusty conditions to
develop Wednesday morning. Most area terminals can see gusts
between 20-25 knots on Wednesday. The nose of a low-level jet
will press into the region by Wednesday evening and can bring
LLWS concerns for terminals largely Pittsburgh on south
beginning near 00z Thursday.

Outlook...
Widespread restrictions, snow showers and gusty winds are then
expected after 00z Thursday with a cold front and subsequent
upper troughing and lake enhancement.

Improvement to VFR is expected from S-N Friday as the wave exits and
wind backs to the SW. Restriction and snow potential returns
Saturday with a warm front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Storm Watch from this afternoon through late Thursday
     night for PAZ007>009-015-016.
     Winter Storm Watch from this evening through Thursday
     afternoon for PAZ074-076-078.
OH...None.
WV...Winter Storm Watch from this evening through Thursday
     afternoon for WVZ511>513.
     Winter Storm Watch from this evening through Thursday
     afternoon for WVZ514.

&&

$$

SYNOPSIS...Rackley
NEAR TERM...WM
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Shallenberger