350
FXUS61 KPBZ 301453
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1053 AM EDT Sun Jun 30 2024

.SYNOPSIS...
Isolated showers and storms will continue to move ahead and
along a cold front early this morning into early afternoon.
Building high pressure will return comfortable dry weather.

&&

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

- Isolated showers and thunderstorms are possible along and
  ahead of a passing cold front this morning/afternoon.
- A few storms could become strong, sub-severe wind gusts with
  heavy downpours.
- Cooler and drier weather expected tonight behind the front.
-------------------------------------------------------------------

Latest observations and satellite imagery place a southeastward
advancing cold front now south of I-80 in an environment in
which instability is plentiful with up to 1500 J/kg MLCAPE,
EBWD of 30-40 knots, and DCAPE up to 1100 J/kg. However,
updrafts are struggling with vertical extent as low and mid
level lapse rates are poor, and storms are really only growing
closer to the higher terrain where orographic influences may be
providing an extra nudge. A good amount of mid-level dry air has
started to work in in as noted on the 12 PIT sounding, so
updrafts may be entraining dry air. With warm rain processes
still dominant, any shower or storm will produce a quick burst
of heavy rainfall with it (earlier storms had 3-4"/hr rainfall
rates). Our window for development will continue over the next
couple hours until the front clears the area, and the highest
threat for any strong storms still appears to be south and east
of Pittsburgh.

Convection promptly ends with the passage of the front. Cooler
and drier air advects into the region (noted on BUF`s 12Z
sounding) providing relief from the heat and humidity that has
plagued us since Friday night and allowing temperatures to dip
into the 50s overnight.

&&

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

- Drier air builds in with cooler temperatures.
-------------------------------------------------------------------

Dry weather and below normal temperatures prevail with high
confidence Monday and Monday night as heights begin to rise and
high pressure builds east. In fact, latest HREF probabilities
show most locations having a <30% chance of reaching 75 degrees,
with the exception being urban areas (e.g., Pittsburgh metro)
and portions of eastern OH south of I-70 where the probabilities
for reaching 75 degrees are closer to 50%. Low temperatures
Monday night dip into the low to mid 50s, roughly 7-10 degrees
below normal for this time of year.

&&

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

- Dry weather continues Tuesday with warming temperatures.
- Showers and thunderstorms expected Wednesday through the end
  of the work week with the return of a more active pattern.
-------------------------------------------------------------------

Good agreement amongst the various ensemble clusters supports dry
weather on Tuesday as ECONUS ridging builds. Temperatures begin to
rebound as flow becomes more south of east and pushes highs back
toward or a couple degrees above normal.

By mid-week, ensembles break the ridge down and shunt it
southward over the Southeast CONUS and Gulf Coast, leaving
zonal flow over the Ohio Valley and lower Great Lakes while
lower heights settle in upstream over the upper Great Lakes and
Midwest. This patten is certainly more active than the first
half of the week, promoting surface low pressure over southern
Ontario that quickly tracks northeastward and leaves a trailing
cold front sagging southward into our area late Wednesday into
Thursday. There is some minor concern at this time that the
zonal flow overtop what appears to be a slowing and
weakening/diffusing cold front could lead to a setup where
multiple rounds of showers and storms develop along said east-
west oriented boundary in a moisture-rich environment (ensemble
mean PWATs surpassing 1.75 inches), leading to training of
thunderstorms and flooding rain potential. It`s too far out to
say any of this with certainty, but I would like to see the
pattern become a bit more progressive to prevent the front from
slowing or stalling over the local area and put these concerns
at ease. Additionally, machine learning continues to highlight
some severe potential with this pattern as the front will
initially be moving into a warm and moist airmass, though weak
flow aloft resulting in limited bulk shear is helping to keep
the overall threat low at this time. Still, this too will bare
watching over coming days.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Ports are beginning their morning falls from VFR to MVFR in low
clouds, with temporary IFR possible at FKL and DUJ. This is
related to some cooling in a deep saturated near-surface layer.
This is expected to persist through the morning before
scattering and lifting to VFR is expected for the day with
mixing.

As the front slowly crosses, convection may development towards
LBE and MGW, utilizing some heating in the late morning and
early afternoon. However, confidence is still low that the
terminals will be directly impacted.

Hi-Res guidance suggest that VFR cigs will likely build between
16Z to 18Z with diurnal heating. Daytime gusts into 20-25kt
range is possible with post- frontal mixing into an increasing
pressure gradient. Stratocumulus decks may try to fill in
tomorrow night in northwest flow; MVFR after 06Z was noted for
now.

.Outlook...
VFR is expected until a slow moving front sets up across the
region Wednesday and Thursday.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Cermak/Hefferan/MLB
SHORT TERM...Cermak/MLB
LONG TERM...Cermak/MLB
AVIATION...Hefferan/Milcarek