808
FXUS61 KPBZ 030503 AAC
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
103 AM EDT Thu Apr 3 2025

.SYNOPSIS...
A very active pattern over the next few days, with multiple
rounds of showers and storms. There will be flooding and severe
storm concerns through the weekend.

&&

.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:

- Another round of thunderstorms, possibly severe, overnight.
- A Flood Watch is in effect for portions of eastern Ohio.
- A second round of showers and storms returns late in the day.
-------------------------------------------------------------------

Biggest forecast headache overnight is timing of the line of
storms and how their structure will change as they move
eastward. A strong shortwave trough will move eastward
overnight. The wave will continue to support a line of showers
and storms that will cross most of the area by shortly after
dawn. Latest hires model data is weakening the activity as it
moves eastward. This is due to a lack of instability and also,
there remains ample warm air aloft which could help to limit the
vertical extent of the convection. The area currently with the
highest risk for severe storms would be over Ohio. SPC has put
all of Ohio counties, the Northern Panhandle of West Virginia
and Mercer county PA in a severe thunderstorm watch until 7am.

A shortwave trough will quickly move to the east this morning,
allowing for a break in the widespread showers and storms. The
trough will push a surface boundary southward through the region
but it will eventually stall over the area as minor upper level
height rises occur the afternoon. This stalled front will be
the focus point for more activity late in the day and into the
evening hours, as another shortwave moves northeastward across
the region in the southwest flow aloft. A second large moisture
plume will accompany the wave.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
KEY MESSAGES:

- Showers and thunderstorms continue through the rest of the
  work week as a front remains stalled over the area.
- A Flood Watch remains in effect for portions of eastern Ohio.
-------------------------------------------------------------------

The front is progged to drift south of the area tonight. However
widespread showers and storms should continue overnight as a
shortwave continues to pull a plume of deep moisture northward.
Some of the model data is showing a weak surface reflection
developing underneath the wave which will move across the area
late tonight and Friday morning. Eventually, the moisture plume
will exit the area on Friday and there should be a decrease in
shower coverage from north to south as Friday`s activity will
become more focused near the stalled surface front.

Yet another surface low is then expected to track NE out of the
Mississippi Valley region Friday night, pushing the front back north
this time as a warm front. 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.
However, if the front moves far enough north, we may see a break
in the activity late Friday night and Saturday morning as the
main moisture plume will be forced northward as well.

Amounts through the day on Saturday look to be highest from
Pittsburgh and north with forcing along the warm front and
enhanced convergence on the nose of an impinging 850 mb jet.
We`ll briefly reside in the warm sector before the cold front
comes through in the latter half of the day bringing yet another
enhancement in rain coverage along it. The severe weather
potential should be limited due to weak instability, however
with repeated rounds of heavy rain and a saturated ground,
flooding potential will increase, especially with rises on area
rivers.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
KEY MESSAGES:

- Showers/thunderstorms with potential for heavy rainfall continue
  this weekend.
- A cold front moves through Sunday finally bringing an end to the
  heavy rainfall threat.
- Colder next week with lighter rain/snow chances each day.
-------------------------------------------------------------------

Showers and thunderstorms continue Saturday night as the surface low
tracks through the area, yet is still unable to effectively move the
stalled frontal boundary. Ensembles suggest another heavier period
of rain on the nose of another low level jet Saturday night into
Sunday morning falling on a then very saturated ground. However,
ensemble clusters all agree on a deep upper trough swinging across
the eastern CONUS on Sunday into Monday which will finally shunt the
surface ridge that had been firmly planted over the southeast CONUS
coast and allow a cold front to advance through the area and off to
the east bringing an end to the heavy rain and storm potential.
There`s some discrepancy in the timing of the upper pattern and how
quickly the trough axis arrives with the cluster dominated by the
GEPS suggesting a slower cessation of the rain in the Monday morning
hours.

The upper trough is then expected to persist across the NE CONUS
early next week, resulting in temperatures dipping to below normal
values and daily rain/snow chances, albeit not nearly as intense as
what we`re experiencing this week.

&&

.AVIATION /05Z THURSDAY THROUGH MONDAY/...
Residual showers and isolated thunderstorms ahead of an 850mb
warm front are expected to decay under the influence of broader
subsidence 2-3 hours after TAF issuance. VFR with 4-8kft
ceilings are expected through 06z within the warm sector of an
incoming low pressure system; development of a strong ~50kt
llvl jet is likely to remain above the inversion (and llws
height threshold) but enough sub-inversion mixing may foster SSE
gusts between 20-30kts.

A well-developed QLCS complex of showers/thunderstorms will
weaken as the enter the region after 06z, but uncertainty is
fairly high on initial intensity as it reaches ZZV and its
ability to maintain through western PA. TAFs noted that a likely
brief wind shift out of the west will occur with the line
before southerly synoptic winds prevail; thunderstorm intensity
will dictate if higher speeds can occur (more likely at ZZV and
trending down eastward).

Stagnation of the cold front driving the convective system is
likely somewhere near/south of KPIT, which may allow for a
brief period of MVFR cigs as moisture converges on the
stationary boundary. Brief dry weather and mixing will improve
cigs 12z-18z before additional shortwave movement aloft and any
trailing sfc boundary offers lower probability showers. Timing
of these showers and a more potent upper shortwave Thursday
night creates greater variability in precipitation timing and
restriction potential.

Outlook...
The Upper Ohio River Valley will remain positioned between a
Central Plains trough and Atlantic ridge that will foster
multiple rounds of moderate to locally heavy rain through Monday
morning. Timing and shape in each wave remains variable, which
may alter the axis of highest precipitation rates and areas of
greatest restrictions. Aviation customers should anticipate
limited windows of VFR and dry conditions through the period as
the pattern favors MVFR/IFR restrictions, heavier rain showers
and occasional thunderstorms.

A deepening upper trough may overtake the region early next
week, shifting towards a colder pattern featuring periodic
rain/snow chances and continued ceiling restrictions.

&&

.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. Lesser probabilities exist further east,
though a trend up has been noted in the latest ensemble guidance
and will need to be monitored for any potential expansion of the
flood watch. The exact location of the heaviest 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 through Sunday morning for OHZ039-040-048-049-
     057>059-068-069.
WV...None.

&&

$$

SYNOPSIS...22
NEAR TERM...22
SHORT TERM...Cermak/22/MLB
LONG TERM...Cermak/MLB
AVIATION...Frazier
HYDROLOGY...