Area Forecast Discussion Issued by NWS Pittsburgh, PA
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000
FXUS61 KPBZ 171959
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
359 PM EDT Sun Mar 17 2024
.SYNOPSIS...
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A cold upper trough will create unsettled weather through
Tuesday morning with snow showers expected. Mid to late week
will feature near normal temperatures and mainly dry weather.-- End Changed Discussion --
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.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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KEY MESSAGES:
- Lake enhanced showers to continue mainly along and north of
I-80
- Turning colder overnight especially over the southern half of
forecast area
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Deep and cold trough over the Great Lakes will gradually move south
overnight. 500 mb heights will fall another 70 meters or so as
a result. The column will continue to cool and especially the
boundary layer, with 850 mb temps falling from about -4C this
evening to -11C in the PIT area by 12z Monday.
Latest ACARS sounding from KPIT shows adiabatic lapse rates and
deep boundary layer up to about 750 mb, indicating cloud tops
just touching the bottom of the (Dendrite Growth Zone) DGZ
around -12C. Closer to Lake Erie the convection is deeper and
quite vigorous, with rain and snow showers. The heavier
precipitation is likely changing over to snow or graupel. This
activity is likely to weaken with loss of diurnal heating so
expect coverage to be maximized between now and about 6 pm.
The coverage of snow showers will become a bit more sparse
overnight. However, with loss of sunlight and cooling
temperatures there could be light accumulations overnight
especially along and north of I-80.-- End Changed Discussion --
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.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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KEY MESSAGES:
- Cold and unstable under upper trough with showers of snow and
graupel.
- Potential for light snow accumulation, mainly north of I 80
and in the higher terrain
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Upper trough will start the day over northwest Ohio and Lake
Erie, moving to western PA and WV by the late afternoon.
Strongest height falls of 150 meters will be over VA.
A very cold and unstable airmass is expected given we have mid
March sun angle. 850 mb temps will be around -10C, 700 mb -18C,
and 500 mb dropping to around -35C. RAP soundings show moist and
unstable situation with diurnal heating under trough with
increasing moisture and even 100-300 j/kg of CAPE. Cloud tops
will be in the -20 to -25C range, so vigorous convective snow
showers are expected which certainly could produce brief heavy
snow bursts and graupel. Accumulations outside of ridges will be
limited by March sun angle. However, with convection continuing
into the evening, there is certainly the potential for
accumulations north of I-80 and over the ridges Monday night.
CIPS analogs indicate that the WV ridges have a 30-50% chance of
4" or more in patterns like this. At this point expect 2-3" in
those areas so expect a sub-advisory event especially during the
daylight hours.-- End Changed Discussion --
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.LONG TERM /TUESDAY THROUGH SUNDAY/...
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KEY MESSAGES:
- Near normal temperatures expected Tuesday through Friday
- Mainly dry weekend with moderating temperatures
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As heights gradually rise and flow turns from northwest
towesterly aloft, a low pressure area over the Great Lakes will
skirt mainly north of the forecast area as it heads toward
Ontario/Quebec/New England Tuesday into Wednesday. Certainly
could be snow in the northern half, especially Tuesday morning,
but the system will have limited moisture so the precipitation
shield is more likely to impact New York and far northern PA.
Flow gradually tilts from westerly to southwesterly as the week
progresses with gradually rising heights and moderating
temperatures. While near normal readings are expected most of
the week, moderation begins over the weekend with highs in the
50s Saturday and Sunday.-- End Changed Discussion --
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.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
ACARS sounding from KPIT shows steep lapse rates up to 750 mb
and a mean wind of about 25 knots in that layer, which would
suggest surface gusts to about 25 knots and that is what
observations are showing across the area. Closer to Lake Erie
the boundary layer appears a bit deeper and there are convective
rain showers north of I-80 which are mixing with snow and
graupel when the precipitation is heavier. Although VFR is
expected for the most part through this evening, brief MVFR
conditions are possible at KFKL and KDUJ.
RAP soundings under cold upper trough on Monday suggest it could
be quite convective with cloud tops colder than -20C and perhaps
200-300 j/kg of CAPE. Locally heavy snow showers would result
along with graupel and even small hail during the afternoon and
evening. Conditions should be VFR outside of the heavier snow
showers but could be briefly IFR especially over the northern
half of the area closer to Lake Erie.
.Outlook...
VFR returns Wednesday and Thursday as a ridge of high pressure
builds in
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.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
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SYNOPSIS...Craven
NEAR TERM...Craven
SHORT TERM...Craven
LONG TERM...Craven
AVIATION...Craven