PBZ issues Area Forecast Discussion (AFD) at Aug 18, 12:21 AM EDT882
FXUS61 KPBZ 180421
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1221 AM EDT Sun Aug 18 2024
.SYNOPSIS...
A slow moving upper level system will promote rounds of showers
and thunderstorms through Monday, primarily during the
afternoon and evening hours. Dry and cooler weather is expected
for much of the coming week.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
KEY MESSAGES:
- Isolated showers and a few thunderstorms are possible
overnight, becoming more numerous near dawn.
-------------------------------------------------------------------
A slow-moving mid/upper-level low remains centered north of the
area and slowly shifting east, currently over Lake Huron. Waning
instability and exit of the pre-frontal trough have reduced
shower/thunderstorm coverage overnight. A few clusters of
thunderstorms do continue east of Pittsburgh, but these are
expected to exit the area in the next couple of hours. The
severe threat has ended, and storm motion is fast enough to keep
flooding at bay.
Latest cams continue to indicate some redevelopment just before
dawn as the cold front crosses and a weak shortwave trough
pivots around the base of the low. The extent of this early-
morning redevelopment is somewhat uncertain.
Moist conditions and lingering cloud cover will ensure little
movement overnight in area temperature. Morning lows will be
just above normal.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/...
KEY MESSAGES:
- More widespread convection is favored Sunday, but poses a
more limited hazard risk.
- Residual showers with cooler temperatures are likely on
Monday, diminishing Monday evening.
-------------------------------------------------------------------
By Sunday, the upper low/trough will be centered just to our
north, allowing for lower convective temps and more widespread
thunderstorm development in the afternoon. There is some
uncertainty in favored locations due to slight variations in
trough positioning that may create subsidence holes, but the
overall pattern/environment should support on and off storms
through the evening. The lack of strong instability despite 90th
percentile PWATS and some forward motion of storms should
preclude a flood threat.
The trough continues east on Monday, leaving the area under
cooler, northwest flow. Residual diurnally-driven showers are
possible through the day, eventually diminishing Monday evening.
Area temperatures will drop well below the daily average,
resulting in daily highs in the 60s and lower 70s.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
KEY MESSAGES:
- Long range trends favor dry weather and near normal
temperature.
-------------------------------------------------------------------
The region will remain under northwest flow on Tuesday, but with
dry conditions. Residual cold air advection will lead to
temperature around 10 degrees below the daily average.
Long range analysis favors a continuation of the fairly
amplified pattern of ridging over the Rockies and troughing
along the east coast. This should position the region within the
drier NW flow pattern where precipitation chances will be
heavily reliant on strong shortwave movement over the ridge.
Latest trends don't favor this and thus suggest a prolonged
period of dry weather and seasonable temperature Wednesday
through the end of the week.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
A large, stacked low pressure system over the eastern Great
Lakes will gradually fill while drifting east overnight and
Sunday. Weak troughs extending south from the low rotate through
the area tonight and again toward dawn, and rounds of showers
are likely with each. Thunder is also possible, but with less
coverage and intensity compared with this past afternoon and
evening.
An uptick in showers and thunderstorms is anticipated again in
the afternoon heating beneath the exiting system on Sunday, but
these are expected to be less organized compared with this past
afternoon and evening, even as additional surface troughs/fronts
cross.
Low stratocumulus is likely to settled in overnight and persist
into if not through Sunday morning throughout the area, and even
through much of the day across northern sites FKL and DUJ.
Light, mainly south surface flow overnight will become light
west on Sunday, but could fluctuate as surface troughs cross,
even freshen a bit with a few gusts at times. Moderate southwest
flow aloft tonight will become light southwest overnight, and
then gradually veer to light west on Sunday.
.Outlook...
Periodic restrictions and showers and thunderstorms are possible
through early Monday as low pressure slowly crosses the region.
VFR conditions return by Tuesday under high pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Rackley
NEAR TERM...Rackley/Shallenberger
SHORT TERM...Rackley/88
LONG TERM...Rackley/Frazier
AVIATION...MLB
Source:
PBZ issues Area Forecast Discussion (AFD) at Aug 18, 12:21 AM EDT---------------
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