-- Discussion containing changed information from previous version are highlighted. --
144
FXUS61 KPBZ 192347
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
747 PM EDT Sun May 19 2024

.SYNOPSIS...
Mostly dry weather and a warming trend is expected through
early week, with a few near-record temperatures possible on
Tuesday. Shower and thunderstorm chances return Wednesday and
continue through late in the week, with severe weather a
possibility on Wednesday.

&&

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

- Save for an isolated shower on the ridges, dry weather and above-
  normal temperatures are expected.
  _____________________________________________________________

A mostly sunny sky will continue CWA-wide this afternoon under an
upper ridge. Model cumulus rule favors the ridges/areas east of
Pittsburgh for mainly scattered convective cloud development, and
have shaded the grids in that direction. CAMs are still advertising
isolated showers in the ridges, and this seems reasonable with
expected elevation-aided convergence. Continued with a very small
PoP to these areas. Afternoon high will climb into the low to mid
80s across much of the area this afternoon, around 10 degrees above
normal for this time of year.

The overnight period will feature a mostly clear sky with light wind
and above-normal temperature.  NBM visibility probabilities are
favoring portions of southwest PA and northern WV once again with
patchy fog overnight.  Will go along with this idea, but will keep a
patchy mention as drying this afternoon should limit fog extent
somewhat.

&&

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

- Mostly dry weather is forecast through Tuesday night.
- Temperatures continue to climb to 10-15 degrees above normal, with
  a few record high values possibly approached on Tuesday.
  _____________________________________________________________

Mostly dry weather is forecast for this period, as the upper ridge
axis slowly trudges eastward and crosses the Atlantic coast on
Tuesday. A couple of the CAMs try to develop some convection on
a Lake-Erie induced boundary on Monday afternoon and drift it to
the south. Not confident enough in such activity reaching the
CWA given the weak flow under the ridge, but it is something to
evaluate over the next couple of model runs.

Also, there is still a very weak shortwave in the model progs
that rides up the back side of the departing ridge on Tuesday.
An isolated shower or storm north of I-80/along the NW periphery
of our eastern Ohio counties cannot be ruled out, but again, a
dry outcome seems most likely.

The bigger story during this period remains the well-above
normal temperatures. Plenty of sun, a drying ground, and 850 mb
temps climbing into the 14-16C range will contribute to highs
reaching well into the 80s both Monday and Tuesday. Tuesday may
be the warmest day on an areawide basis. NBM probabilities of 90
degree or higher temperatures remain in the 30 to 50 percent
range in river valleys and metro areas on that day. The May 21st
record high at DuBois (86, from 2022) looks to be in greatest
jeopardy. However, if the warmer end of guidance proves to be
correct, other records at Pitt International (92, from 1911),
Morgantown (92, from 1934) and New Philadelphia (91, from 1962)
could at least be approached.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
KEY MESSAGES:


- Rain chances return for Wednesday and Thursday, with some potential
  for strong thunderstorms.
- Near to just above seasonable temperatures and lower rain chances
  are expected Friday and into the weekend.
  ____________________________________________________________

Overall, model guidance still favors an upper low/trough in or near
the northwestern Great Lakes by Wednesday afternoon, with a followup
shortwave trough crossing the Michigan area that night and getting
absorbed into the larger trough.  Minor strength and timing issues
remain, but overall, the pattern still favors higher PoPs with the
secondary shortwave, bridging the Wednesday night/Thursday
period, which will likely also involve a cold frontal passage at
the surface during the day on Thursday. Given the increased
shear expected with the overall system, as well as the potential
for decent instability in the warm and humid conditions ahead
of the front Wednesday, the afternoon/evening period of that day
appears to hold the best potential for severe weather. CIPS/CSU
guidance, NBM-based CWASP progs, and SPC all seem to suggest
this possibility, with areas west of Pittsburgh showing the best
potential. This will of course be given increased scrutiny as
we approach the midweek period. Temperatures will likely be
muted a bit by the approaching clouds and rain Wednesday
afternoon, especially west of Pittsburgh, but will still remain
well above normal.

It appears that the Thursday night/Friday period will be relatively
quiet with weak surface ridging indicated, along with temperatures
closer to climatology. Model details become more unclear over the
weekend, but with the possibility of weak shortwaves crossing the
Middle/Upper Ohio Valley in WSW flow aloft, some lower-end PoPs in
the 20 to 40 percent range are necessary for both Saturday and
Sunday. Temperatures may nudge up to a few degrees above normal.

 &&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
Expect clear skies overnight and given the amount of dry air
over the area, the fog threat will be limited to a few areas.
The best chance of 50% will be over DUJ and MGW with a lower
chance at FKL and LBE. Otherwise, expect VFR through the
overnight.

VFR and dry weather is expected Monday with high confidence
under the influence of high pressure. Wind will again be light
and variable.

.Outlook...
VFR and dry weather continues Tuesday under high pressure.
Precipitation chances and associated restrictions return
Wednesday with the passage of a cold front.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Shallenberger