Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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000 FXUS61 KPBZ 141749 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 149 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/... 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. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... 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). && .LONG TERM /SUNDAY THROUGH THURSDAY/... 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. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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VFR conditions are ongoing to start the TAF period. Aside from a scattered afternoon cu field that has develops over portions of southeast OH, the rest of the area is generally seeing only high clouds overspreading from the west ahead of an approaching line of showers and thunderstorms. The line of storms, currently entering western Ohio, will continue to push its way eastward through this afternoon before weakening as it enters the local area. ZZV is the most likely site to see thunder from this first wave of convection while the rest of the area may only see a brief passing shower as it dissipates. Additional showers and thunderstorms redevelop later this evening around or after 23Z over central Ohio, then pushing eastward through the local area generally between 00Z and 05Z. This will be the best chance to see thunder at most area terminals. A cold front advances through the area from northwest to southeast after 09Z tonight with IFR/LIFR restrictions becoming more widespread as it pushes through. The front and its associated rain showers finally depart mid to late Friday morning and restrictions begin to lift in their wake. .Outlook... Ceilings improve back to VFR levels Friday night but patchy fog development could maintain restrictions through early Saturday. VFR briefly returns later Saturday under high pressure, before another cold front returns increasing potential for precip and restrictions on Sunday.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...WM NEAR TERM...WM/Frazier SHORT TERM...Frazier LONG TERM...Frazier AVIATION...Cermak

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