737
FXUS61 KPBZ 081353
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
853 AM EST Fri Nov 8 2024

.SYNOPSIS...
Dry weather is expected through Saturday. Low pressure will
support widespread rainfall Sunday into Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:

- A weak cold front this afternoon will increase the threat for
  gusty winds.
- Elevated fire danger today.

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

River valley fog has developed across most of our area this
morning with air temperatures in the mid 30s settling over
warmer waters and light to calm wind. The 12 PIT sounding shows
copious dry air through the boundary layer, so a train of
shortwaves evident on water vapor imagery will have no effect to
sensible weather through the morning hours, and once we break
the very shallow nocturnal inversion the day will be mostly
sunny. With ample sunshine and no cold advection until late
in the day, high temperatures will be close to 10 degrees above
normal; areas south of Pittsburgh have a 40-60% shot of
breaking 65F highs while elsewhere low 60s are most favored.

Aforementioned shortwaves will push a weak cold front through
the region during the afternoon. The front will have little to
no moisture to work with, so its passage will be dry. The front
will tighten the surface pressure gradient, and with increasing
mixing heights, gusty winds are possible this afternoon. This
will again raise concerns for fire weather issues. In coordination
with state officials, have issued an SPS for most of southwestern
Pennsylvania where the best overlap of minRH values and wind
gusts is expected. Higher RH values further northwest will
preclude greater fire weather concerns.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
KEY MESSAGES:

- Temperatures will remain near to above the daily average
  Saturday.
- High confidence in widespread wetting rain Sunday.

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

Cold air advection is expected this evening and into the
overnight hours. The colder air aloft should be accompanied by a
stratocu deck which will cover a large portion of the region
into the overnight hours.

Height rises are anticipated Saturday ahead of a closed low
lifting through the Central Plains. A broad surface high will
move across southern Canada keeping the area dry. Warm air
advection, associated with the building ridge, should keep
temperatures slightly above seasonal averages.

Look for area cloud cover to increase late Saturday night as
moist advection increases ahead of the aforementioned low
pressure system.

Low pressure will lift through the northern Great Lakes Sunday.
This will promote widespread rain for the region. The
combination of stronger forcing and some fetch of tropical
moisture lends to near 100% probabilities for wetting rains
(considered greater than 0.10") with 50-60% probabilities of
total accumulations greater than 0.50". Discrepancies/spread in
total accumulations and timing of precipitation onset are due in
part to variation in depth/positioning of the upper trough
which will impact the placement of the greatest frontogenetic
forcing/lift.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
- High confidence in widespread wetting rain into Monday
  morning.
- Ensembles favor a lower amplitude pattern portending to
  smaller areal temperature swings and multi-day breaks between
  precipitation chances.
-------------------------------------------------------------------

Ensembles suggest a secondary piece of energy may quickly follow
the crossing trough as it exits Monday, but large spreads exist
on its depth/timing. Better modeling of this feature will lend
high confidence to how quickly precipitation ends and area
temperature rebounds heading into Tuesday.

There is fairly high confidence of a deepening trough across the
western U.S. Tuesday/Wednesday that will result in some ridge
amplification over the Ohio River Valley. This favors
persistence of above normal temperature with generally dry
weather, though shortwave movement over the ridge are likely to
impact the degree of warming/drying.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
VFR is expected for most airports through Friday under high
pressure. The exception will be for MGW, ZZV and FKL, where MVFR
to IFR vsby in fog is likely late tonight and early Friday
morning. Model soundings look favorable for fog formations, and
probabilities of this occurrence has increased to over 50
percent in these areas on recent short term model ensembles.

Light NW wind overnight will increase by Friday afternoon out
of the WNW with gusts to around 20kt as the pressure gradient
increases ahead of a surface trough approaching from the north.
This trough should spread VFR stratocu across the area,
especially north of PIT, toward the end of Friday.

.Outlook...
VFR is expected Saturday, before rain and restrictions
overspread the region Saturday night and Sunday with low
pressure. VFR returns Monday and Tuesday under high pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...22
NEAR TERM...22/MLB
SHORT TERM...22/Frazier
LONG TERM...Frazier
AVIATION...88