Area Forecast Discussion Issued by NWS Pittsburgh, PA
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000
FXUS61 KPBZ 251758
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
158 PM EDT Mon Mar 25 2024
.SYNOPSIS...
Fire weather danger is expected today due to gusty conditions
and low relative humidity, a Special Weather Statement was
issued in collaboration with our partners. Downslope wind gusts
this evening into tomorrow have prompted a Wind Advisory for
areas east and southeast of Pittsburgh. Rain chances increase
after 6am Tuesday, ahead of a cold front.
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.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- A Special Weather Statement (SPS) was issued in collaboration
with our Ohio and West Virginia partners for fire danger
today. Low relative humidity and gusty conditions will result
in an increased risk of fire start and spread.
- A Wind Advisory has been issued for downslope potential late
this evening and into Tuesday.
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This 12Z PIT sounding suggests that very dry air at 1,000ft to
4,000ft will mix to the surface with diurnal heating and prompt
a second day of very low relative humidity values. MinRH values
will range from 20% to 25% for West Virginia and eastern Ohio;
30% to 35% for PA counties. Along with dry conditions, wind
gusts between 15mph to 25mph will be observed throughout the
day as a disturbance over the Plains strengthens and increases
the gradient wind field. Therefore, fire weather danger will be
a concern throughout the evening and it is advised to exercise
caution if handling open flames or equipment that creates
sparks. A Special Weather Statement was issued in collaboration
with surrounding WFOs and the State Foresters in West Virginia
and Ohio. Despite low relative humidity in Pennsylvania, the 10
hour fuel moisture was measured above the 10% threshold level of
concern. Therefore, no Special Weather Statement was issued for
western PA.
A Wind Advisory was issued along the ridges of Pennsylvania and
West Virginia after 7pm this evening due to downslope winds.
Probabilities are high that localized wind gusts over 50mph from
the southeast could create impacts: unsecured objects may blow
away, tree limbs could be blown down, and power outages may
increase early Tuesday morning.
Otherwise, dry and above normal conditions are likely today with
a building ridge over the Ohio River Valley. Temperatures will
10 to be 15 degrees above the climatological normal.
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.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
KEY MESSAGES:
- Strong wind gusts (+50mph) along the ridges of West Virginia
and Pennsylvania is expected tonight into Tuesday afternoon
due to downsloping; Wind Advisory continues into early Tuesday
afternoon.
- Rain chances return to the region Tuesday with an approaching
disturbance.
- Scattered light showers continue Wednesday with the slow
crossing of a cold front.
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Upper level ridge will remain parked over eastern PA tonight.
This will slow the eastward movement of an upper level wave
rotating northeastward on the eastern side of the massive
central US trough. This should keep the area dry tonight.
A tight surface pressure gradient, and crossing low-level jet,
will increase the risk for strong wind gusts over the ridges
tonight. Hi-Res guidance probabilities are considered high
(above 80%) over the ridges for 50mph wind gusts from the
southeast through 1pm Tuesday due to downsloping. The Wind
Advisory continues for the Laurel Highlands and West Virginia
ridges.
Still seeing some timing issues with the onset of rain on
Tuesday and how far east it will push before either stalling or
dissipating. The amplified ridge over the east coast will
begrudgingly move eastward on Tuesday. The shift will be in
response to a shortwave trough that will eject eastward from the
central US trough. Much of the energy from the shortwave may be
spent fighting the ridge. Models are showing a descent moisture
plume passing through the region on Tuesday, which will aid in
bring widespread rain to the area. It does appear that as the
rain moves eastward, it will decrease in coverage and intensity.
Probabilities for >0.25 inches for the eastern half of the
forecast area are 40% to 60% while over the western half are 60%
to 70%. Looking at probs >0.50 seeing around 15% to 45%, with
the higher numbers over Ohio. Rainfall will be generally light
with the higher QPF mainly over Ohio.
With rain and increased cloud cover, highs on Tuesday will drop
a few degrees, but still remain above normal.
With the slow eastward movement of a cold front, due to the
stubborn east coast ridge, the risk for scattered showers will
continue on Wednesday. However, a large upper level dry slot
will spread across the region ahead of the front, greatly
limiting rainfall amounts. Its not out of the question that much
of the rain directly along the front will dissipate Wednesday
afternoon.
Temperatures remain above normal on Wednesday.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
KEY MESSAGES:
- Dry conditions are favored Thursday and Friday.
- Unsettled weather returns for the weekend.
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Dry conditions are more likely with the reestablishment of high
pressure Thursday and Friday. Although an isolated shower cant
be completely ruled out over the ridges on Thursday.
Eastern CONUS ridge will try to amplify over the weekend.
However, it appears as if we will be located right at the top of
the ridge. Shortwaves, riding over the ridge, will keep in the
risk for scattered showers both Saturday and Sunday. Above
normal temperatures will remain through the weekend.
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.AVIATION /18Z MONDAY THROUGH SATURDAY/...
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VFR conditions will prevail through early Tuesday afternoon.
Scattered to broken upper level clouds will continue to slide
across the area ahead of approaching low pressure still centered
well off to our west. A tightening pressure gradient has
resulted in southeasterly wind gusting to 15-25 knots this
afternoon.
Later tonight, as a 40-50 knot low level jet moves overhead
after 00z, all sites aside from LBE will likely have decoupled
and a strong inversion will prevent gusts from mixing down
resulting in just a 10-12 knot gradient wind. However,
downsloping with southeasterly flow will increase gusts
overnight at LBE as probabilities increase to ~70% for >40
knots, primarily between 02z-06z; this will preclude a low
level wind shear threat at LBE. However, with limited gusts at
the surface at other sites and the strong low level jet overhead,
low level wind shear will develop after 06z and continue
overnight until the boundary layer begins to mix in the morning,
increasing surface gusts to 15-20 knots and ending the wind
shear threat.
Rain will arrive from the west beginning late Tuesday morning,
but will be battling a lot of surface dry air at onset. Hi res
ensemble probabilities indicate most likely precipitation onset
around 11z for ZZV, 16z for FKL to PIT to MGW, and after 18z for
LBE/DUJ, which may even be a bit aggressive given the extent of
the dry air in place. Probabilities look to remain <50% for
ceiling restrictions in rain, but MVFR visibility restrictions
are possible (~50% chance) toward the end of the TAF period.
.Outlook...
Restrictions may linger into early Wednesday with lingering
boundary layer moisture before the passage of a cold front in
the morning, but VFR then returns with high confidence for
Thursday and Friday under high pressure.-- End Changed Discussion --
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.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Wind Advisory from 7 PM this evening to 1 PM EDT Tuesday for
PAZ073>078.
OH...None.
WV...Wind Advisory from 7 PM this evening to 1 PM EDT Tuesday for
WVZ510>514.
&&
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SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...22
LONG TERM...Hefferan/22
AVIATION...MLB