PBZ issues Area Forecast Discussion (AFD) at Jul 20, 10:56 PM EDT742
FXUS61 KPBZ 210256
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1056 PM EDT Sat Jul 20 2024
.SYNOPSIS...
Quiet, dry weather is expected for a large portion of the
region under high pressure through Sunday. Precipitation
chances increase Monday into Tuesday with an approaching trough
from the west.
&&
.NEAR TERM /THROUGH SUNDAY/...
KEY MESSAGES:
- Dry for much of the area under high pressure
________________________________________________________________
11PM Update: No major changes to this forecast period. Adjusted
temperatures, dew points, and cloud cover to reflect current
observations.
Previous Discussion:
Expect dry weather with diminishing cloud cover for the rest of
the region as it remains under the influence of western Great
Lakes high pressure.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
KEY MESSAGES:
- Seasonable temperature with increasing cloud cover expected
through Monday
- Thunderstorm chances increase Monday afternoon but favor
locales south and east of Pittsburgh
_________________________________________________________________
Shortwave ridging traversing the Atlantic high will support dry
weather Sunday while moist southwest flow behind it will lead
to increase cloud cover late in the day into Monday. Expect area
high temperature to run about 5 degrees above the daily average.
Ensemble models favor increased shower and thunderstorm chances
starting Monday morning in association with a weak trough
lifting from the eastern TN River Valley. Jet aided ascent and
moisture convergence lends to the higher probability of
occurrence along the Laurel Highlands and WV high terrain.
However, trends are bearish for the rest of the region as
probability of measurable rain is less than 50% (over a 24-hour
period) and likely that high as a result of model resolution
issues near the terrain feature. Combined with HREF mean CAPE
values being near zero, expect limited afternoon storm coverage
with many locations remaining dry. More abundant cloud cover due
to the shortwave will limit insolation and keep area temperature
near the daily average.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
KEY MESSAGES:
- Periodic shower and thunderstorm chances increase through the
week
- Above average temperatures expected
________________________________________________________________
The sagging central CONUS trough is anticipated to slowly lift
ENE through the Ohio River Valley Tuesday through Thursday while
deepening as it phases with another lobe of energy dropping out
of Canada. Ensembles favor periodic shower and thunderstorm
chances while temperature hovers near the daily average. Severe
weather appears unlikely as mean SBCAPE values hover around 500
J/kg (likely a result of residual warm air aloft and weak sfc
heating).
Tuesday may start out with shortwave ridging while awaiting
another shortwave to lift out of the TN River Valley. If forcing
remains delayed and farther W/S, then afternoon storm chances
may be more isolated and favored natural convergence zones (Erie
lake breeze, WV higher terrain). Similar sort of uncertainties
may develop for Wednesday as well that lends to lower
probability, more isolated convection than currently depicted by
ensemble model means. Confidence in widespread convection is
highest Thursday due to higher likelihood of surface cold front
plus upper trough axis passage that day/evening.
Depending on how quickly the upper trough axis exits and high
pressure builds in will influence whether lingering
showers/thunderstorms are possible Friday and the degree of
temperature rise.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
VFR is largely expected through the TAF period with light to
variable winds and streams of broken to overcast cirrus.
.Outlook...
VFR is expected through the Monday under the influence of high
pressure, though probabilities increase for isolated to
scattered afternoon storms Monday mainly along the WV higher
terrain and Laurel Highlands.
Scattered shower and thunderstorm chances are expected Tuesday
through Thursday with the slow approach of an upper level trough
from the west. Current probabilities favor afternoon to evening
storm timing, with lower risks during the overnight to morning
hours.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...22/Frazier/Milcarek
Source:
PBZ issues Area Forecast Discussion (AFD) at Jul 20, 10:56 PM EDT---------------
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