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.
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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 ------------------------------------------------------------------- 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.
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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 ------------------------------------------------------------------- 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.
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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 ---------------------------------------------------------------- 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.
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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 && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Craven NEAR TERM...Craven SHORT TERM...Craven LONG TERM...Craven AVIATION...Craven

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