PBZ issues Area Forecast Discussion (AFD) at Mar 24, 8:27 PM EDT108
FXUS61 KPBZ 250027 AAA
AFDPBZ
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
827 PM EDT Mon Mar 24 2025
.SYNOPSIS...
Passing disturbances will support periodic precipitation chances
through the week but most will remain largely dry. Temperatures
will fall some into mid-week before rising to above normal by
next weekend. An unsettled pattern looks to setup next weekend
bringing rounds of rain chances.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
KEY MESSAGES:
- Wind diminishing tonight
- Dry weather for most of the area
-------------------------------------------------------------------
Evening update...
A surface trough was across central and southern PA, and will
continue to exit the region this evening. Removed POPs for areas
south of I 80 as the trough exits. A few rain or snow showers
are possible N of I 80 through part of tonight under broad upper
troughing, though coverage should be minimal. Wind will also
continue to diminish through the evening as mixing subsides.
Previous discussion...
Flow will veer more westerly tonight as weak shortwave energy acts
on some shallow moisture north of I-80 in marginally freezing
surface temperatures. It's up that way that soundings increase
moisture deep enough to allow for some scattered rain and snow
showers, though they will still have to battle the dry air in
the low levels after dew points mixed out this afternoon despite
the southwest flow. Limited moisture penetration into the DGZ
and falling inversion heights along with warm ground
temperatures will keep snow growth and accumulation to a minimum
with perhaps a couple tenths of an inch at most on cold
elevated surfaces.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:
- Some rain/snow showers south of Pittsburgh Tuesday into early
Wednesday.
- Seasonable temperatures Tuesday turning cooler Wednesday.
-------------------------------------------------------------------
A lead shortwave will slide through the longwave eastern CONUS
troughing on Tuesday locally increasing cloud cover again and
introducing precip chances south of the Mason Dixon line in the
afternoon hours. Some slight deviation in the track of a weak
surface low will dictate how far north this round of precip
reaches. HREF probabilities are highest across northern WV, but
expanding the neighborhood probabilities out (to better capture
spatial uncertainty) does note a potential slight shift north
from the point probabilities. Highs will be a few degrees cooler
than Monday with lingering troughing and neutral temperature
advection in westerly flow. HREF soundings again suggest another
day of deep diurnal mixing, but with a lesser pressure gradient
and less wind aloft to tap into, gusts won't be quite as high
as Monday with peaks around 30 mph.
A second shortwave overnight Tuesday night will pull precip chances
further north, but still most likely confined from Pittsburgh south.
Guidance still exhibits some latitudinal spread in the area of
precip with the NAM3km being the noted outlier further north.
The HREF suggests that a line roughly from Coshocton to
Pittsburgh to Latrobe could be the cutoff for the northward
extent, and expanding the neighborhood probabilities out (to
better capture spatial uncertainty) doesn't deviate far from the
point probabilities, so confidence is increasing that the best
chances will remain to the south coinciding with the best
moisture and overlap of mid-level frontogenesis. Given the
overnight timeframe, thermal profiles suggest a mix of rain and
snow with a period of all snow possible in the highest
elevations. Given antecedent warm ground temperatures and light
rates with low SLRs, some minor accumulation is possible in the
ridges with around a 30-40% chance of 1 inch. Low temperatures
Wednesday night will dip below normal with values ranging form
the mid 20s to near 30.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
KEY MESSAGES:
- Dry Thursday.
- Unsettled weather returns on Friday through the weekend.
- Warmup into the weekend with above-average temperatures.
-------------------------------------------------------------------
The axis of the longwave trough will exit to the east on Thursday
downstream of central CONUS ridging. Slight timing differences
amongst the ensembles suggest some variation to how quickly heights
begin to rise, but current differences are mostly subtle enough to
result in negligible temperature differences. Surface high pressure
now off to our south will maintain dry conditions.
Anticyclonic southwesterly flow behind the departing high will
result in day one of increasing moisture and temperatures on Friday.
Mid-level height rises are forecast as surface low pressure develops
across the Plains and an elongated warm front lifts through. Warm
advection driven precip chances will ramp up on Friday afternoon or
evening, dependent on the progression of the downstream high and
attendant low with more zonal mid-level flow encouraging quicker
arrival of precip. Ensembles then meander said boundary around the
area locally into the weekend with continued rain shower chances. Of
note by Sunday is part of our eastern Ohio counties outlooked in the
Day 7 severe threat by SPC. Machine learning and CIPS analogs match
up with this potential as a trough cuts through the warm, moist
airmass, but exact details remain far from certain.
It's likely that temperatures rise above normal again for the
weekend, but exactly how high is quite uncertain; the latest NBM
continues with the spread of ~17 degrees between the 10th/90th
percentiles at Pittsburgh with the potential for mid 60s or low 80s.
Until more ensemble pattern resolution, will continue with NBM mean,
but recognizing that a lean in one way or the other and not a
middle split is probably the more likely outcome.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
High winds are starting to decrease this evening with decoupling
after sunset. However, there could still be some periods overnight
wind gusts as a shortwave entering the region from the north.
Once mixing redevelops after dawn on Tuesday, wind gusts will
once again increase (15kts to 25 knots) from the west.
VFR conditions remain the play, with less afternoon cumulus and
middle and high clouds dominant.
Outlook... VFR is largely expected through mid week as the
region generally sits within the dry slot of a fairly stagnant
upper trough and some influence of surface high pressure to the
southwest. Embedded shortwaves within the upper trough pattern
may initiate low probability precipitation/restriction chances
that favor FKL/DUJ and the higher terrain, but model variability
remains high on these features.
A late week/weekend pattern shift to eastern CONUS ridging may
come with a transition period featuring increasing precipitation
and restriction chances.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...MLB
NEAR TERM...WM/MLB
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Hefferan/CL
Source:
PBZ issues Area Forecast Discussion (AFD) at Mar 24, 8:27 PM EDT---------------
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