Area Forecast Discussion
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FXUS61 KPBZ 221031
Area Forecast Discussion
National Weather Service Pittsburgh PA
631 AM EDT FRI JUL 22 2016
Hot and humid weather is forecast for today into early next week,
along with intervals of scattered thunderstorms.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --630 AM...A band of thunderstorms currently extends along the Lake
Erie shoreline and is heading southeast. Think that some weakening
is likely over time as the line heads into a more unfavorable
air mass with less available CAPE and 0-6km shear. Likely PoPs
are still prudent along/north of I-80 with an increase to higher
chance values south to Pittsburgh. Think that this line will
degenerate into more scattered activity by late morning...but
confidence is fairly low as hi-res models seem to be struggling
Boundary layer moisture will be on the increase today, evidenced
by dewpoints rising into the lower 70s in some of the area. While
850 mb temperatures will be a bit warmer than yesterday, cloud
cover is expected to be a bit more widespread during the day,
helping to keep temperatures from soaring well into the 90s.
Nevertheless, low 90s are a good bet for some areas, especially
southeast Ohio. Heat index values should reach the upper 90s in
this area. While a few locations will flirt with triple digit
apparent temperatures, do not think coverage will be widespread
enough to warrant heat advisories at this time.
As far as precipitation coverage, elected to keep PoPs in the
scattered range for the afternoon and evening. Some relatively
warm mid level air will help to hinder development at least
initially. Also, think that the better deep layer shear will
remain with a shortwave crossing the Great Lakes into New England.
This should keep a lid on any organized severe weather threat.
Nevertheless, decent mixing will promote inverted-V soundings
which may point to an isolated wind damage potential with any
storms that manage to develop.
A weak boundary will sink into the area tonight. Activity will
diurnally decrease this evening ahead of it, but given high
moisture, presence of the front, and lingering convective
boundaries, think at least isolated activity will remain possible
for most of the night. Otherwise, a classicly muggy July night can
be expected, with low temperatures on either side of 70.
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.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A weak boundary will stall out over the southern third of the
forecast area by Saturday morning. Models continue to activate
showers and thunderstorms along this boundary through the
afternoon, but a lack of upper- level support and dry air through
the column should limit development. Opted to continue with slight
chance/isolated shower or thunderstorms south of Pittsburgh.
Remaining mid-level moisture will clear the southern border by late
Saturday, ending the low rain chances. Near-surface moisture and
high surface dewpoints will linger, resulting in another warm and
humid night with lows well above average. Surface high pressure will
shift east Sunday as the next system moves through the southern
Canadian Plains. This will return southerly flow, and re-enforce the
warm and humid airmass. A few showers could develop across our
western zones Sunday afternoon as the weak boundary returns north as
a warm front. Heat indices Saturday and Sunday will reach into the
mid and upper 90s for a majority of our forecast area, and approach
100 for a few of our southwestern counties. An HWO mention will be
maintained for this.
Warm and humid conditions will carry into the new work week,
although an increase in clouds will limit high temperatures. A weak,
sweeping cold front will drag across the area Monday, bringing a
chance of rain for all, but the progressive nature of the system
will limit amounts.
.LONG TERM /MONDAY THROUGH THURSDAY/...
Rain chances will quickly dissipate in the wake of the cold front,
Tuesday, bringing a return to dry conditions. The upper-level flow
pattern will temporarily flatten to nearly zonal, as high pressure
builds at the surface. Temperatures will moderate under the zonal
flow aloft, but will remain a few degrees above normal. Consistent
model agreement on the digging of a trough over the cornbelt in the
latter part of next week. This will bring rain chances back to the
forecast Thursday and Friday.
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --Watching a band of thunderstorms along the Lake Erie shoreline,
which is moving slowly south. Expect some weakening with time as
they move into a more hostile environment. Still, a brief period
of IFR visibilities in heavy rain looks like a good bet at FKL and
DUJ between 12Z and 14Z, and used TEMPOs for this. To the south,
with higher uncertainty, continued to use VCTS wording. A brief
thunderstorm is possible at any terminal this afternoon in the hot
and humid environment. Confidence in timing best chances this
afternoon is low, and kept prevailing conditions VFR. Should see
a typical decrease in activity this evening, with clouds
scattering with time. MVFR visibilities in mist are possible late
tonight, especially in any area that gets rain today.
.OUTLOOK /FRIDAY NIGHT THROUGH TUESDAY/...
Restrictions will be possible late Sunday and Monday with
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