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000
FXUS61 KPBZ 181557
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1157 AM EDT Thu Apr 18 2024

.SYNOPSIS...
Light precipitation northeast of Pittsburgh will diminish early
afternoon with increase mid-lvl dry air. Clouds may linger over
western PA with cool NW flow over Lake Erie. Precipitation
chances return early Friday with a passing front.

&&

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

-  High temperature expected to be approximately 5 to 10
   degrees above the seasonal average.
-  Overnight low temperatures will trend above average with
   linger low-lvl moisture and cloud coverage increasing with an
   approaching disturbance.

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


The progession of ridging over western Ohio into western PA
this afternoon/evenig will support dry weather today and
clearing gradually throughout the day. Above average
temperatures are expected again today with increasing warm
advection and radiation heating. Probability of >=70 degrees
ranges between 55 to 80% for areas south of I-70. The spread in
temperatures is likely due the uncertainty in the spatial
resolution of cloud coverage.

Clouds will increase overnight amid warm, moist advection ahead
of the next shortwave system set to traverse the Ohio River
Valley Friday. Limited cooling is likely as thicker cirrus
limits nocturnal radiational cooling, keeping low temperature
above normal and likely the highest reading for the upcoming
week.

&&

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

- Showers and low probability thunderstorms are expected ahead
  of a cold front Friday.
- Seasonable temperature and dry weather expected through the
  weekend.
- Potential for frost and/or freeze impacts each of Saturday and
  Sunday mornings.
----------------------------------------------------------------

A pivoting shortwave within the broad western Great Lakes trough
is expected to promote broad ascent that, combined with a
passing surface cold front, will generate showers and low
probability thunderstorms Friday morning into the early
afternoon. Subsidence and dry slotting of the upper trough will
quickly end precipitation chances behind the passing cold front,
while more notable cold advection begins to lower area readings.

Ensembles favor the trough axis transition over the Upper Ohio
River Valley to occur Saturday with quasi-zonal flow developing
into Sunday. Saturday`s axis cross will push a reinforcing shot
of cooler air during the later afternoon hours, pushing area
temperature slightly below average each day. Lack of column
moisture should preclude shower generation Saturday, though
there is some hint of potential Lake Erie enhancement that could
light rain for northwest PA.

The biggest potential impact is the development of frost/freeze
conditions during the overnight periods Saturday and Sunday as
all but Tucker County is in an active growing season. Saturday
night into Sunday is the more likely period for freezing
temperature for northwest PA (30-50% probability) as elevated
winds should prevent frost formation. Sunday night into Monday
is the more likely period for frost given lighter winds and
clearer skies.

&&

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

- Next precipitation chances are likely to be Tuesday into
  Wednesday with crossing low pressure.
- Ensembles favor dry conditions outside of that period.
-------------------------------------------------------------------

Confidence is growing that dry weather and seasonable
temperature plus plenty of insolation is likely for Monday as
ensembles push a crossing upper trough well south of the region.

This sets up Tuesday into Wednesday as the next period for
potential precipitation chances with shortwave movement within
the broad eastern CONUS trough pattern. Trough depth and axis
timing remains varied among ensemble members, but they all favor
a shower environment with limited lightning potential as
temperatures hover near seasonal averages.

Long range ensembles favor ridge building over the western Great
Lakes in response to a deepening trough over the western CONUS
for the late week period. The expectation is for area
temperature to once again rise with any passing shortwave posing
greater thunderstorm potential.

&&

.AVIATION /16Z THURSDAY THROUGH MONDAY/...
Widespread VFR with periods of MVFR stratocu is ongoing this
morning due to remnant moisture beneath the post-frontal
inversion. Height rises, diurnal mixing and dry advection all
will aid stratocu erosion through the afternoon, ensuring VFR by
21z at all terminals (most terminals should be VFR by 18z).

Winds will remain light through the period topping out at 10
knots at the most from the west-northwest. Approach of the next
cold front will bring increasing rain chances and lowering
ceilings towards the tail end of the TAF period.

.Outlook...
Restrictions and mostly light rain showers are likely Friday
morning with the approach and passage of a surface cold front.
Dry advection and subsidence will support a quick return to VFR
conditions after frontal passage by Friday night.

Surface high pressure will aid in a continuation of VFR
conditions through the weekend despite the region being
positioned under broad troughing.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan/Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Cermak