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668
FXUS61 KPBZ 021943
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
343 PM EDT Thu May 2 2024

.SYNOPSIS...
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Dry and warm weather gives way precipitation chances Friday
afternoon through this weekend. Cooler, but still above average
temperature prevail Saturday and Sunday. Warm and unsettled
weather continues next week.
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&&

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

- Dry with above normal temperatures continuing.

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High pressure and upper subsidence has acted to keep the area
high and dry during the day today. Despite a developing cumulus
field in higher dewpoints in northern West Virginia, the rest of
the area remains clear and will through the evening. Cumulus
fields will decay after sunset.

Flow aloft will transition southwest overnight, allowing 700mb
to 900mb temperature to remain steady and seasonably warm. This
will limit potential for sharp radiative cooling in clear
skies, with temps expected to bottom out around 10 to 15 degrees
above average.
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&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
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KEY MESSAGES:

- Thunderstorms Friday afternoon and evening.
- Rain favored for most of the area through the weekend.

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As a disturbance approaches from the west, there is high
confidence that a cirrus deck will progressively thicken
throughout the morning and early afternoon. Diurnal heating
will act to break the morning inversion and mix up into a layer
of 850mb-700mb air nearly 11C to 14C above average for this time
of year. This will allow high temperature to reach the middle
to upper 80s for most of the area. Due to increasing cloud
cover, the NBM high temperature for tomorrow was not adjusted
upward any further. Forecast highs have the potential to break
records (see climate section). Likewise, record low max
temperatures may be broken Saturday and Sunday morning with
persistent cloud cover not allowing for radiative cooling.

Rain chances have increased a bit earlier that the prior update
with models suggesting that storms pop in surface- based
instability despite dry low-levels with a fairly deep mixed
layer. A the HREF 25th and 75th percentile have between 400 and
1000 J/kg of environmental CAPE. Once parcels reach the LCL, a
they will be able to utilize this to grow into showers/storms in
the afternoon. Most guidance suggests that warm mid-levels will
suppress updrafts to below about 500mb, but a small fraction
suggest mid-level dry air may not be present (notably the NAM).
This would lend to low-probability of deep updrafts in the
afternoon.

Convection is favored to wain overnight as instability is
lost ahead of the surface trough. Nonetheless, rain will
persist. Come Saturday, there is some suggestion the trough
progression will come to a halt and allow rain to persist ahead
of it, while precipitation may be harder behind it with mid-
level dry air intruding. The positioning of the trough will have
a great influence on the weekend weather. The current forecast
favors rain in western Pennsylvania and northern West Virginia
Saturday, while there is some uncertainty in eastern Ohio.
Probabilistic CAPE in western Pennsylvania ranges from 500 J/kg
on the high end to none on the low end. Probabilities of thunder
in western PA are 20% at best, with around a 30% chance in
eastern Ohio and northern West Virginia.

There is good agreement the trough finally pulls through by at
least Sunday. An area of maximized precipitation ahead of or
just along the trough axis is favored; the susceptible is
located in western Pennsylvania and the northern WV panhandle
for now. Precipitation may be as high as 2" at any given area
(mist likely in the aforementioned favorable region), or as low
as 0.3". Right now the mean 48 hour rainfall around an inch
area- wide. This does not raise any flooding concerns for now,
but may warrant watching.
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&&

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

- Rain chances continue into early next week but more uncertainty
  lends lower confidence.
- Temperatures favored to remain above normal.
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A brief lull in the precip is favored late Sunday night into early
Monday morning as upper ridging slides through and surface high
pressure meanders on by. Uncertainty with its strength and timing
due to ensemble differences in a passing upper wave to the north and
another digging shortwave and associated low pressure moving across
the Tennessee Valley lends lower confidence to the start of the next
workweek, but regardless rain chances ramp back up later
Monday. A stronger ridge and thus less rainfall is the most
likely ensemble solution at this time, but a quicker breakdown
of it could give us another decent shot of rain through Tuesday.
Due to aforementioned ridging, above average temperatures
remain favored into next week. The amplified pattern continues
into mid- week with unsettled weather in store.
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&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR conditions and light winds will continue through the TAF
period. As upper ridging shifts east, shower and thunderstorm
chances increase later Friday afternoon and into the evening as
a warm front lifts north across the region.

.Outlook...
Restriction potential will continue through Saturday and again
early next week as multiple disturbances cross the region.

&&

.CLIMATE...
Some record high temperatures may be approached on Friday.
(* denotes current forecast temperature exceeds value)

               Record High   Year
Pittsburgh          95       1887
Wheeling            90       1942
Morgantown          88*      1965, 2012
New Philadelphia    89       2012
Zanesville          91       1938
Dubois              84       2012

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...Milcarek
SHORT TERM...Milcarek
LONG TERM...Milcarek/MLB
AVIATION...22/88
CLIMATE...MLB