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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 141529
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1129 AM EDT Sun Apr 14 2024

.SYNOPSIS...
Thunderstorm chances increase again on Sunday with a cold
front, some potentially strong to severe. A brief bout of dry
weather expected Monday before rain chances return on Tuesday
with moderating temperatures into next week.

&&

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

- Thunderstorm chances return today with potential for strong to
  severe with a large portion of the area outlined in an
  Enhanced Risk (3/5).
-----------------------------------------------------------------

A passing shortwave trough axis just to our north in western New
York has been sparking off some showers and thunderstorms, but
that activity will remain off to our north with just a few
clouds clipping the I-80 corridor.

Heading into later today, strong southerly flow will allow for
decent warm air advection and keep temperatures well above
normal. To boot, with the passage of the warm front this
morning, only looking at some mid and high level cloud cover
overhead. As daytime heating gets underway and convective
temperatures are reached, will begin to see cu development by
midday. Any shower or thunderstorm development should hold off
until after 19-20z when latest CAMs initiate convection north of
I-80 and intensify as they track south across PA and OH and
eventually WV during the overnight period. The latest hi-res
models suggest the best instability setting up across western PA
and into eastern OH with NBM and HREF probs similarly showing
around a 70-90% chance of SBCAPE >1000 J/kg here, with only
30%-40% chance toward the higher elevations. Getting into shear,
most deterministic feature indicate roughly 30 to 40 knots of
0-6 km bulk shear. The probs of surpassing 40 knots stems around
30% to 40% according to the HREF. Its also worth mentioning
that according to the CWASP parameter (derived parameter of
severe environmental favorability), the most favorable
environment will be across eastern OH into western PA. As model
soundings indicate right curved hodographs, expect to see all
hazards today as the convection begins to materialize. All
models continue to show an initial development of a broken line
of discrete cells as the line dives south into the forecast
area. There is a chance that the line further organizes under
the better shear into a more squall line situation as SPC did
continue with their 30% wind in the outlook. As the line tracks
south, it is possible that a tornado could occur with the line
or with a broken discrete cell. There are some indications that
the line could hang up a bit given the line of storms will be
parallel to the predominant flow aloft. This could lead to a few
hampering flood issues again but further analysis will be need
on that threat. A marginal risk (1/5) of excessive rainfall is
on tap issued by WPC.

The convection should begin to wane as it reaches the PA/WV
border and further slides south-southeast. Into Sunday night,
some lingering showers/storms are likely but the severe threat
should be over by 04Z if not earlier. Lows on Sunday night will
be a bit warmer as the cold front struggles to push south with
mid 50s likely. Clearing out and drying is likely by 12Z Monday.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Dry weather returns Monday with moderating temperatures.
-------------------------------------------------------------------

With the only minimal uncertainty being driven by the
progression of the upper trough into Monday, confidence is high
that the cold front will clear the area by Monday morning and,
aside from some low probability shower chances south of I-70,
the day should be dry. Ensembles aren`t very bullish on
intrusion of cooler air in the wake of the front as an 850 mb
ridge quickly builds in its wake and temperatures take a slight
dip but still remain well above normal. Temperatures will then
rebound nicely for Tuesday with warm southerly flow and highs
reaching the mid 70s. There is a possibility of a fire weather
issue but this depends on rainfall on Sunday.

&&

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

- Temperatures climbing well above average.
- Rain chances return Tuesday night and linger into mid-week.
-------------------------------------------------------------------

Brief upper ridging slides overhead by Tuesday night before
breaking down into Wednesday as an upper trough digs across the
Midwest. Primary ensemble uncertainty stems from the progression
of the trough and surface low, but consensus tracks it through
the Great Lakes to our north and returns rain to our region by
Tuesday as a leading shortwave passes through. Rain chances
continue into Wednesday as the warm front approaches with the
cold front following behind as early as Wednesday night or as
late as early Thursday morning, again owing to uncertainty with
the progression of the upper wave. Ensembles push a secondary
reinforcing cold front through by late week which may tumble
temperatures back down towards normal to close out the week.

Otherwise, above normal temperatures will be the theme into mid-week
as southerly return flow promotes warm advection kicking
temperatures well above average with ensemble probability for >70F
in excess of 70% through Thursday.

The Friday and Saturday timeframe with highlight another wave
forming on the trailing cold front of the previous exiting low.
A lot of uncertainty here so will just mention low chance pops
for Friday and Saturday.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
An advancing cold front will result in a broken line of
thunderstorms by late afternoon and into the evening. Some
storms may be severe. Outside of vis restrictions in TSRA, VFR
can be expected through the period.

A wind shift the W/WNW is expected after FROPA, with VFR cigs
continuing.

.Outlook...
VFR is expected under high pressure Monday and most of Tuesday.
Restriction potential returns late Tuesday and Wednesday with
approaching low pressure. Restrictions are possible into
Thursday under a subsequent upper trough.
-- End Changed Discussion --

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...Shallenberger
NEAR TERM...MLB/Shallenberger
SHORT TERM...MLB/Shallenberger
LONG TERM...MLB/Shallenberger
AVIATION...88