PBZ issues Area Forecast Discussion (AFD) at Jun 30, 3:42 AM EDT629
FXUS61 KPBZ 300742
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
342 AM EDT Sun Jun 30 2024
.SYNOPSIS...
Renewed showers and storms develop early this morning. A cold
front moves across the region late this morning through this
afternoon, with high pressure building in its wake.
&&
.NEAR TERM /TODAY AND TONIGHT/...
KEY MESSAGES:
- Scattered showers and thunderstorms possible along and ahead
of a passing cold front this morning/afternoon.
- A few storms could become strong, with damaging winds the
primary threat.
- Cooler and drier weather expected tonight behind the front.
-------------------------------------------------------------------
Most locations are still hovering in the mid to upper 70 per
latest obs and little additional cooling is expected before
sunrise. This, combined with dewpoints in the low to mid 70s,
has allowed marginal instability to linger through the night,
supporting some isolated shower and thunderstorm activity
predominantly over northeastern West Virginia and portions of
central/eastern Ohio. Expect shower and thunderstorm activity
to increase over the rest of the area after sunrise with the
onset of daytime heating. Flow aloft has weakened and as a
result deep-layer bulk shear has decreased to around 30 knots,
which is still enough to carry a low-end threat for damaging
winds in any stronger thunderstorms that develop. The Storm
Prediction Center has maintained a Marginal Risk (Level 1 out of
5) for this severe threat primarily southeast of the Pittsburgh
metro, across the high terrain of SW PA and much of northern WV.
Convective activity promptly ends with the passage of the cold
front, which doesn't look to occur until late morning through
afternoon hours as it is still located over the Michigan LP as
of writing this discussion. Behind the front, cooler and drier
air advects into the region, 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 /06Z 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.
Coverage of storms, or even showers, appears lack-luster save
the area around MGW, this morning. A slight uptick in coverage
is expected immediately ahead of the crossing cold front.
Current thoughts are that coverage will remain to isolated to
denote at any port for now save some temporary showers in FKL
and DUJ with more saturated low levels. VCSH notes the low-
confidence, and the timing is noted in the TAF group.
As the front slowly crosses, development might get slightly
more robust towards LBE and MGW utilizing some heating in the
late morning and early afternoon, but again, too low confidence
to pin down.
VFR with 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...Cermak
NEAR TERM...Cermak
SHORT TERM...Cermak
LONG TERM...Cermak
AVIATION...Milcarek
Source:
PBZ issues Area Forecast Discussion (AFD) at Jun 30, 3:42 AM EDT---------------
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