PBZ issues Area Forecast Discussion (AFD) at May 31, 1:47 AM EDT585
FXUS61 KPBZ 310547
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
147 AM EDT Sat May 31 2025
.SYNOPSIS...
Occasional lighter rain showers and unseasonably cool
temperature is expected through early Saturday afternoon in the
wake of an exiting low pressure system. Dry weather and rapidly
rising temperature will follow through early next week, as high
temperature hits above normal readings by Tuesday.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Flooding risk is waning as the low pressure system drifts east
of the region, though areal river rises may continue into
Saturday morning.
- Additional lighter rain showers and low probability thunder
remain possible into early Saturday afternoon.
-------------------------------------------------------------------
Latest satellite imagery shows the surface low and the upper
trough axis are shifting east of the region as drier and cooler
NW flow filters in behind. A bulk of the heavier rain has ended,
but widespread 1.5 to 2.5 inch accumulations may maintain flood
conditions across northern WV into far southwest PA through the
dawn hours Saturday before subsiding. Though the threat of flash
flooding has ended (with the expiration of the Flood Watch), it
remains best to be aware of potential flooding ongoing in this
region and follow local safety guidance.
Weak shortwave movement in NW flow combined with lake
enhancement due to cold advection and the morning arrival of a
surface cold front will maintain periodic rain chances through
the early afternoon. As 850mb temperature falls toward 2 to 4
degrees celsius with shortwave movement, lapse rates will
steepen and freezing levels fall which may allow for isolated
thunderstorm generation. The deeper mixing as a result of that
cold advection will foster breezy conditions, with many
locations seeing afternoon gusts between 25 to 35 mph, before
falling around sunset.
By the evening, dry advection and subsidence will quickly
dissipate shower development and result in dry conditions by
tonight. Daytime temperature is unlikely to rise notably given
strong late season cold advection and limited insolation,
leaving readings upwards of 20 degrees below the daily average.
Though records are not likely to be broken, it is likely many
site see readings within the top 5 lowest for maximum
temperature on record.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
KEY MESSAGES:
- Drying and warming trend highly likely Sunday into Monday
- Low probability light rain can't be ruled out for NW PA Monday
afternoon
-------------------------------------------------------------------
There is high confidence in ridge building that will occur
Sunday into Monday as the trough axis shifts east and troughing
deepens across the western CONUS. Residual cold advection and
initiate of those height rises will show more modest temperature
rebounds Sunday, with highs still ~10 degrees below normal,
before area temperature reaches near seasonable levels on
Monday.
Though high pressure is likely to maintain dry weather and
sunnies sky through this period, a few models hint at upper
level warm advection that could increase cloud coverage late in
the day Monday and even squeeze out a few sprinkles. This
remains a low probability outcome and not visible in the
current forecast package but bears monitoring.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
KEY MESSAGES:
- Seasonably warm temperature expected through much of the week,
likely peaking Wednesday.
- Precipitation and severe chances dependent on strength/timing
of shortwave movement over ridge axis.
-------------------------------------------------------------------
Ensembles favor ridging shifting over the Carolinas Tuesday into
Wednesday amid broad troughing over the western CONUS. The
resultant height rises (and surface warm advection in SW flow
Wednesday) will maintain the rising temperature trend along with
dry weather for the Upper Ohio River Valley. Outside of the
higher terrain, ensembles show 70 to 90 percent probabilities of
high temperature readings exceeding 80 degrees Tuesday; they are
near 100% areawide by Wednesday. Notably, valley and urban
locations could see readings hit or exceed 90 degrees Wednesday
(40-60% chance) depending on degree of cloud coverage advecting
east from western Great Lake convection. This may create risk
for heat related impacts Wednesday afternoon if you have outdoor
plans, especially within urban environments.
Variation of outcomes increases Wednesday night through the end
of the week as a series of shortwaves attempt to
breakdown/traverse the Carolina ridge. Ensemble means suggest a
gradual breakdown through Friday that sees waves of
showers/thunderstorms that impact the northern CWA before
progressing southward, with a similar north to south downward
temperature trend. Severe threats will be monitored during this
period as this general pattern can be conducive to severe
environments depending on the degree/quickness of a ridge-
breaking shortwave.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Banded rain in the NW quadrant of the surface low will slowly
shift east of the region through 06z while additional scattered
showers move SE out of the Great Lakes with shortwave movement
aloft. Restrictions will be mainly tied to the rain and
lingering moisture along the Laurel Highlands (MGW) and northern
WV through 06z before moisture convergence ahead of an incoming
cold front foster widespread MVFR/IFR cigs around 12z.
Additional shortwave movement in NW flow plus cold advection
will foster an additional round of scattered rain showers
favoring PIT and SE through 18z before tapering off. Cold air
aloft may allow for isolated thunderstorms despite weak
instability, but confidence in coverage is too low to mention.
Frontal passage will foster gusty NW wind between 25 to 35 mph
with occasional gusts up to 40 mph in the higher terrain.
Outlook...
There is high confidence (greater than 90% probability) in VFR
by 00z Sunday under the influence of high pressure and dry
advection. These conditions are likely to persist under ridge
building to start the next week.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Frazier
NEAR TERM...Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at May 31, 1:47 AM EDT---------------
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