Area Forecast Discussion Issued by NWS Pittsburgh, PA
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000
FXUS61 KPBZ 141709
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
109 PM EDT Thu Mar 14 2024
.SYNOPSIS...
Mainly dry weather is expected early today as high pressure
moves east of the area. Shower and thunderstorm chances will
increase later today as a cold front approaches. A few storms
could be severe, mainly across Ohio. The front will slowly cross
the region tonight and Friday, with more widespread showers and
a few thunderstorms. Dry weather returns Saturday before another
cold front brings showers Saturday night.
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.NEAR TERM /THROUGH TONIGHT/...
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KEY MESSAGES:
- Shower and thunderstorm chances increase from west to east
today
- A few severe storms are possible mainly across eastern Ohio.
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1pm Update...
Though weakening is still expected, expanded shower mention
across northwest PA as weak, elevated convection persists amidst
a narrow region of enhanced moisture and shortwave activity
around 700mb.
Timing for likely QLCS passage through eastern OH also updated
based on latest forward-speed timing and Hi-Res model analysis.
Further discussion below.
Rest of discussion...
There is growing consensus of an initial QLCS currently
traversing eastern IN along a quasi-warm front to maintain much
of its structure as it reaches eastern OH. Driven by 40-50kts
shear and an impinging 50kt 700mb jet, the question of impact
will be focused on storm maintenance and realized environmental
instability. Latest analysis suggests upwards of 1000 J/KG
SBCAPE may develop across western OH with a notable gradient to
the stable ridge-axis airmass in western PA. Though instability
wanes eastward, it appears increasingly likely that some form of
the current line will hold through at least of portion of
eastern OH. Damaging wind would be the primary threat given
storm mode, with low-end probability for embedded QLCS tornadoes
if any line segment surges, and low-end hail (given shorter
residence time with fast forward storm motion). Current timing
for far eastern OH (think Zanesville) as between 3pm-4pm,
reaching the OH/WV border between 5pm-6pm. The degradation of
the line is expected as it reaches WV/PA, but enough may remain
to still see showers/thunderstorms and a low-probability wind
threat.
A lull behind the initial convective line will be replaced by
increased storm development along and just ahead of the sagging
stationary boundary in conjunction with increased shortwave
movement aloft and strong jet ascent. If these storms are able
to develop cohesion along the boundary and tap into ~500 J/KG
MUCAPE, they may pose an additional wave of low-probability
severe thunderstorms favoring a damaging wind threat. Also of
note is that convection motion and upper flow will begin to be
more parallel, a setup that can favor training storms. At this
time, the threat for flooding appears low as there likely is not
enough instability for storm regeneration over the same areas
as storms dive SE on available instability ahead of the actual
surface boundary.-- End Changed Discussion --
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.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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KEY MESSAGES:
- Showers and a few thunderstorms Friday, with low probability
flood threat.
- Dry and cooler Saturday
- Shower chances return with a Saturday night cold front
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Showers and embedded thunderstorms will remain likely south of
the sagging cold front Friday, but dry advection from the north
and the eventual passage of the shortwave trough axis will push
remaining storms south and east of the region by Friday evening.
Cooler air filtering in behind the front will drop area
temperature but remain 10 degrees above the daily average. Any
threat from the remaining thunderstorms will be tied to flooding
due to multiple rounds of moderate to heavy rain; however,
probabilities for high rainfall rates (given limited
instability) and excessive rain (less than 10% chance of 24 hr
QPF values exceeding 1") are too low for any strong mention of
flood potential.
The Upper Ohio River Valley will experience dry weather under
the influence of high pressure as it sits between shortwave
activity to the north and south. Slight warm advection combined
with insolation will support area temperature approximately 10
degrees above the daily average. The northern stream shortwave
will drop southeast overnight Saturday, but with a more meager
moisture profile, will generated showers mostly confined to
northwest/western PA (with lower probabilities into OH and
northern WV).-- End Changed Discussion --
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.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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KEY MESSAGES:
- An active and colder pattern the first half of the week
- Snow shower chances return Monday and Tuesday
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Ensemble models favor an active weather pattern through early
next week as a series of shortwave troughs cross the region amid
broad Great Lakes troughing. Expect slight swings in temperature
between systems, oscillating between near to below normal, as
well as periodic precipitation chances. There is high confidence
that enough cold advection will occur with a Monday/Tuesday
system to foster a primarily all-snow precipitation-type event;
this, like others, system may be more limited in available
moisture which would limit the potential for any impact.
By mid week, height rises as flow aloft becomes more zonal is
expected, which would foster a return to near/above normal
temperature and at least a brief period of dry weather.-- End Changed Discussion --
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Confidence remains high that VFR conditions will continue into
the early afternoon time period under high pressure. Adjusted
wind gusts for the early afternoon, sufficient diurnal heating
should help mixed elevated wind gusts to the surface. Probabilities
are higher west of PIT after 16Z for 20kt gusts as a disturbance
builds over the Midwest.
Clouds will start to thicken during the late morning and
afternoon with a flux of warm, moist conditions under strong
southerly flow. However, confidence is still remains high that
ceilings will stay above 5000 feet. Remnant convection
developing in the Midwest this afternoon may track into the Ohio
River Valley late this evening. A few storms may be severe west
of PIT; PROB30 for -TSRA has been added to cover the uncertainty
of unorganized convection.
A descending cold front from Lake Erie to northern PA will
likely keep precipitation in the region into early Fri morning.
MVFR to IFR conditions will likely follow in the wake of the front
(between 06Z to 12Z Friday).
.Outlook...
Restrictions remain possible through early Saturday, either from
cigs and/or areas of fog.
VFR briefly returns later Saturday under high pressure, before
another cold front returns a restriction potential Sunday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM/Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Hefferan/CL