691
FXUS61 KPBZ 250705
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
205 AM EST Mon Nov 25 2024

.SYNOPSIS...
Light rain returns after 9am today and continues into the early
Tuesday with a passing front. Confidence is high that Arctic
airmass will advance into the Ohio River Valley late this week.

&&

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

- Patchy river valley fog is expected in areas that observe
  persist clearing early this morning
- Rain chances increase late morning and continue throughout the
  day with a passing low pressure system
------------------------------------------------------------------

A low pressure system is currently positioned in western
Illinois and eastern Iowa early this morning. The center of the
low is expected to track northeast over the Great Lakes and
return rain chances late this morning in eastern Ohio; after
12pm for western Pennsylvania.

Expect low-level flow in increase from the south late this
morning. With increasing warm advection, afternoon high
temperatures will be near or a few degrees above average today.
If precip advances in quicker than a majority of Hi-Res
ensembles project, MaxTemp may trend cooler.

Probability of measurable precipitation (0.01 inches) is high
(above 90%) across the region through tonight. However, the
probability of rainfall amounts above 0.25 inch through midnight
ranges between 40% to 50%. Weak scent ahead of the cold front
is likely the reason why precip amounts will trend low.

&&

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

- Rain chances remain elevated through early Tues with a passing
  front
- Drier conditions are expected after 7am Tuesday in eastern
  Ohio, 9am in western PA
- Clouds will linger north of Pittsburgh through late Tuesday
-------------------------------------------------------------------

Rain will continue until the front completes its passage Monday
night. Scattered areas of rain and snow in cold advection behind
the front, mainly along and north of the I-80 corridor. Any
precipitation should taper off Tuesday night as high pressure
begins to build across the region.

Temperature on Monday are expected to be 5 to 10 degrees above
average ahead of the cold front, before returning to seasonable
levels after FROPA.

&&

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

- Mainly dry Wednesday
- Rain and snow chances return Wednesday night and Thanksgiving
- Much colder and unsettled pattern by late week
-------------------------------------------------------------------

Model ensembles indicate a trough will begin to advance eastward
from the central CONUS Wednesday, as low develops across the
Southern Plains. Increasing moisture and ascent in southwest
flow ahead of the trough, and on the northern side of the
developing low, will return rain and snow to the region
Wednesday night.

Operational models differ in the positioning of the low by
Thanksgiving, with some keeping it further south, and others
further north. This will affect both the amount and type of
precipitation across our region. At this time, ensemble tracks
favor a more northern positioning of the low, though plenty of
uncertainty exists in the details. Stayed close to the ensemble
blend guidance, which results in rain and snow across the region
on Thanksgiving. Snow is more probable north of PIT, with rain
to the south.

A significant pattern change is then expected, as the initial
trough deepens into a long wave trough across the Eastern CONUS
through the remainder of the long term period. Much colder
temperatures and periodic rounds of snow are expected as
individual shortwaves rotate through the trough, and some lake
and terrain enhancement occurs.

Seasonable temperatures are expected early in the forecast
period, before readings drop to between 15 and 20 degrees below
average after Thanksgiving.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
Enough dry air advection in weak southwest flow has returned
VFR to all sites this evening amid increasing patches of upper
level cirrus. Radiational cooling under a period of clear skies
during the early overnight hours may initially allow a few
pockets of fog to form, especially in the river valley areas,
and peeks of this are just starting to show up on satellite
imagery. That said, the increasing cirrus should limit the
threat as it arrives from the west. Highest probability for
periodic VIS restrictions sit at FKL/DUJ around 40-50% which
makes sense as they`ll likely remain clearest for longest, so
opted for a TEMPO group there as confidence isn`t high enough
for prevailing restrictions given aforementioned cirrus.

Ceilings are expected to lower once again Monday afternoon in
advance of a cold front. Latest guidance doesn`t show much
change with MVFR likely by/after 17z and further degradation to
IFR expected after 00z Tuesday. Light, scattered showers are
expected in the afternoon and evening, though probabilities are
initially low as saturation will take some time. Have covered
with Prob30s in the afternoon until better chances for both rain
and higher confidence restrictions arrive overnight.

Outlook...
Widespread restrictions will likely continue into Tuesday with
showers. Skies will begin to scatter Tuesday afternoon with dry
advection. Additional showers and restriction chances are
expected mid to late week with a new large-scale disturbance.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...WM/88
LONG TERM...WM
AVIATION...Rackley/MLB