PBZ issues Area Forecast Discussion (AFD) at Apr 2, 8:12 AM EDT861
FXUS61 KPBZ 021212
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
812 AM EDT Wed Apr 2 2025
.SYNOPSIS...
Rain and thunderstorms return today through the end of the week.
A few storms could be strong. Multiple days of rain could lead
to local flooding issues. A Flood Watch remains in effect for
eastern Ohio.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Showers and thunderstorms return with a warm front this
afternoon and a cold front tonight.
- Locally heavy rainfall and severe storms are possible.
- A Flood Watch is in effect for portions of eastern Ohio.
-------------------------------------------------------------------
Made minor adjustments to low morning PoPs to account for
timing of initial isolated showers, which may arrive in our
eastern Ohio counties near ZZV starting around 13Z. These
initial showers (perhaps a thunderstorm) will struggle to get
rain to the ground initially with plenty of dry air below 500mb
(as confirmed by 12Z PBZ sounding), but the approaching warm
front/associated isentropic lift should moisten the column
sufficiently to support better shower/thunderstorm development
by midday. Instability still appears to be elevated overall,
although hail development still appears likely. Added hail
mention to the grids/ZFP. Will continue to monitor potential
for strong downsloping wind gusts on the western side of the
Laurels, with peaks of around 40 MPH expected.
Previous discussion...
Strong surface low pressure is expected to track across the
Plains and Upper Midwest region on Wednesday, as a warm front
extending east of the low lifts across the Upper Ohio Valley
region. A vorticity maximum in SW flow aloft will cross the
region at the same time, supporting a wave of showers and
thunderstorms across the area. Instability will be elevated,
with a strong inversion progged above the surface as 850mb
temperatures warm to above 10C. Despite meager MUCAPE (around
500 J/kg), strong shear in place will support the potential for
hail in storms during the initial wave this afternoon. With the
departure of the first wave, a mainly dry evening is expected
under weak subsidence behind the aforementioned vort max.
However, gusty non-thunderstorm winds out of the southeast will
continue, especially in areas just west of the Laurel Highlands
and northern WV ridges where downsloping enhancement could
support gusts over 40 mph. Despite even stronger winds aloft,
wind direction and inversion heights still appear suboptimal for
anything stronger reaching the surface.
Showers and thunderstorms will increase again overnight as a
cold front and shortwave trough approach. Significant shear is
progged to still be in place as the front approaches. The
potential for severe storms will increase late as the front
approaches, though the available instability could be a
limiting factor. The best chance for sufficient surface-based
instability to support severe weather will be over eastern Ohio.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Showers and thunderstorms continue through the rest of the
week as a front stalls near the local area.
- Some storms could be strong to severe on Thursday.
- A Flood Watch remains in effect for portions of eastern Ohio.
-------------------------------------------------------------------
The forward progress of the front is expected to slow on Thursday
as it becomes more parallel to the southwesterly deep-layer
flow. Uncertainty in the exact position of the front exists,
which will impact areas where heavy rain falls and also which
areas have the potential for severe storms. At this time, the
southern half of the area (and especially south of I-70) is
favored for having a more conducive environment for organized
deep convection and severe potential. This continues to be
highlighted in the Storm Prediction Center's slight risk area
(level 2 of 5) generally south of a line from Zanesville, OH to
Indiana, PA. The front is progged to drift south of the area
late Thursday or Thursday night, which will lead to a decrease
in POPs from north to south during that time as the primary
axis of showers and thunderstorms shifts south of the Mason-
Dixon. This is also the window when the strongest upper forcing
for large-scale ascent exits the region, further supporting a
brief decrease in heavy rain and thunderstorm potential
(especially north of I-70) during the day Friday.
Yet another surface low is then expected to track NE out of the
Mississippi Valley region Friday night, returning the front
northward into the local area. Showers and thunderstorms once
again increase in coverage as the front and surface low move
across the Upper Ohio Valley region Friday night into early
Saturday. The severe weather potential should be limited due to
weak instability, however locally heavy rain and subsequent
flooding potential will return.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Showers/thunderstorms with potential for heavy rainfall
continue through Saturday night.
- A Flood Watch remains in effect for portions of eastern Ohio
through Saturday night.
- A cold front moves through Sunday, bringing an end to the
heavy rain and storm threat.
- Colder next week with lighter rain/snow chances each day.
-------------------------------------------------------------------
Showers and thunderstorms continue through the day Saturday as
the surface low tracks through the area, yet is still unable to
effectively move the stalled frontal boundary. However, on
Sunday a large upper low pushing eastward across Canada is
finally able to shunt the surface ridge that had been firmly
planted over the southeast CONUS coast. This is finally able to
shift the pattern enough to allow a cold front to advance
through the area and off to the east, bringing an end to the
heavy rain and storm potential by Sunday night. An upper trough
is then expected to persist across the NE CONUS early next week,
resulting in cooler temps and daily rain/snow chances, albeit
not nearly as intense as what we're experiencing this week.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR is expected to continue this morning, wiuth increasing mid
and high level clouds ahead of an approaching warm front. This
front will lift NE across the region today, with showers,
thunderstorms, and restrictions developing. Timed these storms
with tempos for most of the taf sites, with MGW more uncertain
being on the southern fringe of the activity.
VFR should return after the warm front exits this evening.
Another line of showers and thunderstorms are expected to move
across the area overnight as a cold front approaches.
Instabililty diminishes some overnight, though enough upper
level and jet support should maintain this line through the
overnight period.
Outside of any storms, expect gusty SSE wind today and tonight,
shifting to the SSW overnight. The highest gusts are expected at
LBE, where some downsloping is expected.
Outlook...
Showers and thunderstorms will continue into Thursday as the
cold front slowly crosses the region. This front is expected to
stall Thursday night, and return north Friday and Saturday with
another wave of showers/thunderstorms. Restrictions are expected
to continue into Sunday as the front tracks east as a cold
front, and crosses the Upper Ohio Valley region.
&&
.HYDROLOGY...
The potential for heavy rainfall will exist beginning tonight
and continuing into Sunday. At this time, areas across Ohio have
the potential to see the heaviest rainfall, where a Flood Watch
has been issued. Current NBM values indicate a 60 percent
chance or greater of at least 2 inches of rain over a 72 hr
period in this region, with lesser probabilities further east.
The exact location of heavy rain will depend on the position of
a quasi stationary surface front. Precipitable water is expected
to remain elevated through Sunday, with some periodic jet
enhanced ascent. Even after the heavy rain potential ends, river
levels will likely remain elevated for a few days. Current
ensemble river forecast projections also focus the most
significant river rises across Ohio.
Will monitor further trends for any future adjustments to the
watch.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...Flood Watch from this evening through Sunday morning for
OHZ039-040-048-049-057>059-068-069.
WV...None.
&&
$$
SYNOPSIS...Cermak/Hefferan
NEAR TERM...Cermak/CL
SHORT TERM...Cermak/WM
LONG TERM...Cermak/WM
AVIATION...WM
HYDROLOGY...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Apr 2, 8:12 AM EDT---------------
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