Area Forecast Discussion Issued by NWS Pittsburgh, PA
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000
FXUS61 KPBZ 282132
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
532 PM EDT Thu Mar 28 2024
.SYNOPSIS...
High pressure building over the Upper Ohio River Valley will
bring seasonable temperatures and mainly dry weather through
Friday. A series of low pressure systems are expected to bring
several rounds of showers and thunderstorms Saturday through
Wednesday; hazardous weather may develop.
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.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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KEY MESSAGES:
- Cooler conditions are expected today in the wake a cold front.
- Dry weather and clearing skies with building high pressure.
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Made some minor updates to sky cover into the evening hours, but
otherwise no changes were made as the forecast remains on track
at 530 PM.
Previous discussion...
A series of vigorous shortwaves will traverse the western edge
of the upper trough as the axis crosses the region this evening
and overnight. The second of these waves may spawn a few light
showers or sprinkles late tonight into Friday morning. Any
precipitation that does fall will remain generally south of
Pittsburgh and focused along the ridges with upslope flow. Given
thermal profiles and limited moisture mostly below the DGZ,
precipitation should mainly fall as light rain, through a few
flakes and flurries are possible in the higher terrain.
Accumulation (rain or snow) will be minimal and end Friday
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.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
KEY MESSAGES:
- Dry Friday save for the WV ridges with early wintry mix possible.
- Wind Advisory in effect for eastern Tucker County Friday.
- Widespread rain showers return Saturday.
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Shortwave troughing exits Friday morning as heights rise, albeit
briefly, and dry weather returns to close the week save for the West
Virginia ridges where upslope flow acting on a moist, conditionally
unstable boundary layer will likely support low clouds and some
light precipitation into the late morning. Ensemble probabilities
lean toward snow as the primarily precip type for the morning
hours, though wouldn`t entirely rule out a brief mix with some
rain or freezing rain depending on surface temperatures as
forecast soundings show the depth of the moisture cutting off
below -10C. Spread in ensemble temperature is small, but
hovering right around the freezing mark. Any impacts would most
likely be confined to elevated surfaces, bridges/overpasses
given warm antecedent conditions. Most likely end time of precip
is around 10-11am as dry air finally wins out.
The other note for the West Virginia ridges will be the
potential for high wind gusts in eastern Tucker County on Friday.
As flow turns more westerly, models continue to show a 55-60 kt
mountain wave at 850 mb just east of Tucker County Friday
morning into the evening. NBM probabilities for Advisory
criteria (>46 mph gusts) continue to sit around 75-95% in
eastern Tucker. Strongest gusts should remain downstream given
that this is a northwesterly flow event, but expect the ridges
to get quite windy with 45 to 55 mph gusts likely at the Dolly
Sods Mesonet site. For these reasons, have issued a Wind
Advisory for eastern Tucker County from 4am-8pm Friday.
Otherwise, it will be a seasonable day with plenty of sun under
transient high pressure and warm advection driving high temperatures
into the mid 50s (60-70% chance southeast Ohio tops 60 degrees).
The upper ridge quickly flattens on Saturday as the first in a
series of shortwaves slide in from the west. A warm front lifts
through on Saturday and resultant warm advection drive rain showers
will arrive early in the morning continuing through the day as the
cold front follows quickly behind it and sinks through Saturday
night. Rainfall amounts for this batch look to be contained to half
an inch or less, though a deeper trough could push them closer to
0.6-0.7".
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.LONG TERM /SUNDAY THROUGH THURSDAY/...
KEY MESSAGES:
- A series of weak low pressure systems will keep showers and
thunderstorms in the forecast for much of the period.
- Probabilities increasing for rainfall totals Saturday to Wednesday
greater than 2", highest from Morgantown to Tucker County WV.
- Above-average temperatures are expected.
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The aforementioned cold front then stalls just to our south and
keeps low chance precipitation primarily south of I-70 into early
Sunday morning. Uncertainty remains on how far south it stalls with
some ensemble solutions still holding rain chances up to Pittsburgh,
so will maintain slight chance mention further north until better
agreement comes in.
The front then lifts back north again Sunday night as warm advection
in southerly flow renews. Widespread rain again returns as low and
mid level flow will parallel the east-west oriented boundary as it
sits across our area into Monday. Rich moisture arrives with PWAT
values nearing 1.1" pushing the daily max climatological value.
Another deeper upper wave ejects out of the Plains late Monday as
low pressure forms and plagues the area through mid-week.
Uncertainty comes into play with the timing and strength of the
trough and the track of the surface low with most ensembles
holding downstream ridging strong, but a lower probability
chance exists that a more zonal and progressive pattern unfolds.
In terms of rainfall totals, WPC has placed our CWA in a Marginal
(1/5) risk for excessive rainfall on Monday. Ensemble probabilities
for >2" are increasing (40-70%), especially across West Virginia,
with high end amounts of 3-4" not out of the question. In addition,
machine learning shows increasing severe weather risk Monday and
Tuesday across the Ohio Valley. This will largely be a question of
how much instability can materialize as overall dynamic parameters
are sufficient to support the potential for severe weather. At this
time, analogs hold the threat just to our southwest, but uncertainty
as mentioned above could shift the threat further into our area.
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.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected across the region day until a mostly
clear sky as high pressure builds from the west. Winds will
prevail from the northwest/west into the evening as a shortwave
lifts out of the Great Lakes.
Stratocu cigs are expected to increase tonight as a weak
shortwave crosses the region. A few light rain or snow showers
are possible south of PIT, where slightly more favorable
moisture is expected with the wave. A brief period of MVFR is
possible at MGW, though the latest model probabilities of
occurrence are less than 50 percent.
.Outlook...
VFR is expected through Friday night under high pressure.
Widespread restrictions and showers return Saturday with
crossing low pressure. VFR briefly returns Sunday under high
pressure, before restrictions in showers/possible tstms return
Sunday night and Monday with a warm front.
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.HYDROLOGY...
Widespread round of rainfall are expected beginning Saturday and
continuing into the middle part of next week. Ensemble
probabilities for >2" of total rainfall are increasing
(40-70%) areawide, but especially across West Virginia, with
high end amounts of 3-4" not out of the question there. This may
result in areas of flooding or flash flooding, especially on
Monday, when our area has been placed in a Marginal Risk (1/5)
for excessive rainfall.
Rises on area rivers from prolonged excessive rainfall are also
looking increasingly possible as ensemble probabilities
continue to trend higher by the beginning of next week.
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.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Wind Advisory from 4 AM to 8 PM EDT Friday for WVZ514.
&&
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SYNOPSIS...Hefferan/Rackley
NEAR TERM...Hefferan/Rackley
SHORT TERM...Rackley/MLB
LONG TERM...MLB
AVIATION...WM/Hefferan
HYDROLOGY...