Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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000 FXUS61 KPBZ 141709 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 109 PM EDT Thu Mar 14 2024 .SYNOPSIS... Mainly dry weather is expected early today as high pressure moves east of the area. Shower and thunderstorm chances will increase later today as a cold front approaches. A few storms could be severe, mainly across Ohio. The front will slowly cross the region tonight and Friday, with more widespread showers and a few thunderstorms. Dry weather returns Saturday before another cold front brings showers Saturday night. && .NEAR TERM /THROUGH TONIGHT/...
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KEY MESSAGES: - Shower and thunderstorm chances increase from west to east today - A few severe storms are possible mainly across eastern Ohio. ------------------------------------------------------------------- 1pm Update... Though weakening is still expected, expanded shower mention across northwest PA as weak, elevated convection persists amidst a narrow region of enhanced moisture and shortwave activity around 700mb. Timing for likely QLCS passage through eastern OH also updated based on latest forward-speed timing and Hi-Res model analysis. Further discussion below. Rest of discussion... There is growing consensus of an initial QLCS currently traversing eastern IN along a quasi-warm front to maintain much of its structure as it reaches eastern OH. Driven by 40-50kts shear and an impinging 50kt 700mb jet, the question of impact will be focused on storm maintenance and realized environmental instability. Latest analysis suggests upwards of 1000 J/KG SBCAPE may develop across western OH with a notable gradient to the stable ridge-axis airmass in western PA. Though instability wanes eastward, it appears increasingly likely that some form of the current line will hold through at least of portion of eastern OH. Damaging wind would be the primary threat given storm mode, with low-end probability for embedded QLCS tornadoes if any line segment surges, and low-end hail (given shorter residence time with fast forward storm motion). Current timing for far eastern OH (think Zanesville) as between 3pm-4pm, reaching the OH/WV border between 5pm-6pm. The degradation of the line is expected as it reaches WV/PA, but enough may remain to still see showers/thunderstorms and a low-probability wind threat. A lull behind the initial convective line will be replaced by increased storm development along and just ahead of the sagging stationary boundary in conjunction with increased shortwave movement aloft and strong jet ascent. If these storms are able to develop cohesion along the boundary and tap into ~500 J/KG MUCAPE, they may pose an additional wave of low-probability severe thunderstorms favoring a damaging wind threat. Also of note is that convection motion and upper flow will begin to be more parallel, a setup that can favor training storms. At this time, the threat for flooding appears low as there likely is not enough instability for storm regeneration over the same areas as storms dive SE on available instability ahead of the actual surface boundary.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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KEY MESSAGES: - Showers and a few thunderstorms Friday, with low probability flood threat. - Dry and cooler Saturday - Shower chances return with a Saturday night cold front ------------------------------------------------------------------- Showers and embedded thunderstorms will remain likely south of the sagging cold front Friday, but dry advection from the north and the eventual passage of the shortwave trough axis will push remaining storms south and east of the region by Friday evening. Cooler air filtering in behind the front will drop area temperature but remain 10 degrees above the daily average. Any threat from the remaining thunderstorms will be tied to flooding due to multiple rounds of moderate to heavy rain; however, probabilities for high rainfall rates (given limited instability) and excessive rain (less than 10% chance of 24 hr QPF values exceeding 1") are too low for any strong mention of flood potential. The Upper Ohio River Valley will experience dry weather under the influence of high pressure as it sits between shortwave activity to the north and south. Slight warm advection combined with insolation will support area temperature approximately 10 degrees above the daily average. The northern stream shortwave will drop southeast overnight Saturday, but with a more meager moisture profile, will generated showers mostly confined to northwest/western PA (with lower probabilities into OH and northern WV).
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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KEY MESSAGES: - An active and colder pattern the first half of the week - Snow shower chances return Monday and Tuesday ---------------------------------------------------------------- Ensemble models favor an active weather pattern through early next week as a series of shortwave troughs cross the region amid broad Great Lakes troughing. Expect slight swings in temperature between systems, oscillating between near to below normal, as well as periodic precipitation chances. There is high confidence that enough cold advection will occur with a Monday/Tuesday system to foster a primarily all-snow precipitation-type event; this, like others, system may be more limited in available moisture which would limit the potential for any impact. By mid week, height rises as flow aloft becomes more zonal is expected, which would foster a return to near/above normal temperature and at least a brief period of dry weather.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/... Confidence remains high that VFR conditions will continue into the early afternoon time period under high pressure. Adjusted wind gusts for the early afternoon, sufficient diurnal heating should help mixed elevated wind gusts to the surface. Probabilities are higher west of PIT after 16Z for 20kt gusts as a disturbance builds over the Midwest. Clouds will start to thicken during the late morning and afternoon with a flux of warm, moist conditions under strong southerly flow. However, confidence is still remains high that ceilings will stay above 5000 feet. Remnant convection developing in the Midwest this afternoon may track into the Ohio River Valley late this evening. A few storms may be severe west of PIT; PROB30 for -TSRA has been added to cover the uncertainty of unorganized convection. A descending cold front from Lake Erie to northern PA will likely keep precipitation in the region into early Fri morning. MVFR to IFR conditions will likely follow in the wake of the front (between 06Z to 12Z Friday). .Outlook... Restrictions remain possible through early Saturday, either from cigs and/or areas of fog. VFR briefly returns later Saturday under high pressure, before another cold front returns a restriction potential Sunday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...WM NEAR TERM...WM/Frazier SHORT TERM...Frazier LONG TERM...Frazier AVIATION...Hefferan/CL

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