


Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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301 FXUS61 KPBZ 172118 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 518 PM EDT Fri Oct 17 2025 .SYNOPSIS... Dry weather is expected for most of the area through Saturday, though a weak warm front will bring a chance for light rain or drizzle north of Pittsburgh late tonight. A strong cold front will bring showers, thunderstorms, and gusty winds on Sunday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... KEY MESSAGES: - A few showers/sprinkles late tonight, mainly north of Pittsburgh --------------------------------------------------------------- As mentioned earlier today, there are some weak returns on radar to the north of the area, which may allot a brief sprinkle overnight as ascent aloft moves overhead. For the most part, dry air will limit most people seeing any rainfall. The onset of warm advection aloft and occasional clouds will preclude any chances of frost or freeze tonight. The forecast remains on track. .. Previous Discussion .. Clouds will increase this evening into tonight from northwest to southeast as mid and upper level moisture rides around the northern periphery of the ridge. There is a small chance that a few light showers or sprinkles fall out of these late tonight into early Saturday morning, mainly along/north of I-80. A significant dry layer is still expected to be in place below 700mb, leading to sub-cloud evaporation that will limit any rainfall accumulation to a couple hundredths of an inch at best. Farther south, the near- surface environment is expected to remain too dry for anything more than a passing sprinkle. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... KEY MESSAGES: - Well above normal temperatures this weekend - A cold front passage Sunday offers higher rain chances and windy conditions - A few storms Sunday afternoon could be strong/severe, with damaging wind gusts and possibly a brief tornado being the main threats ---------------------------------------------------------------- The upper ridge that has provided us with dry weather in recent days finally pushes off to our east on Saturday as a trough deepens upstream over the central CONUS. This shift establishes southwesterly deep-layer flow across the Ohio Valley, resulting in gradual moisture return and warm advection which will help temperatures on Saturday climb well above seasonal levels (in some cases as much as 15+ degrees above normal). Meanwhile, a rather potent shortwave trough ejects from the southern Rockies, traversing the southern Plains (OK/TX) before phasing with the broader central CONUS trough and lifting quickly northeastward towards the middle Mississippi Valley and Midwestern states Saturday night. As this occurs, it triggers a surface low to deepen in the vicinity of IL/WI/IA which then quickly lifts - along with the parent shortwave - northeastward over the Great Lakes and into southern Ontario. A cold front associated with this low surges eastward into the Ohio Valley and lower Great Lakes regions on Sunday. The pressure gradient tightens between the Great Lakes surface low and an area of high pressure over the western Atlantic, causing winds across the local area to rapidly strengthen ahead of the cold front. The latest NBM continues to suggest a very high probability (>90%) for frequent wind gusts exceeding 30mph across our entire area during the day Sunday. There are also increasing probabilities (60-80% areawide) for occasional gusts over 40mph. Above that, probabilities quickly drop off, with only a 10-20% chance for gusts over 50mph. Showers and thunderstorms are expected to develop along and ahead of the cold front as it approaches the area late Saturday night and moves through from west to east during the day Sunday. Instability will most likely be weak (MLCAPE on the order of 100-300 J/kg), but with such a potent shortwave and associated surface low, there should be enough forcing from the dynamics of this system to help overcome the instability deficiency. Therefore, a few heavier/stronger showers and storms could develop along the cold front itself, primarily during the Noon to 8pm timeframe. Given how strong the background flow is expected to be outside of convection (see wind discussion in previous paragraph), it`s reasonable to say that any stronger cells could produce locally higher wind gusts that reach or exceed 60mph. Additionally, ample low-level wind shear along the cold front may support transient mesocyclonic structures embedded within whatever squall line ends up forming, and thus a low-end threat for a brief tornado or two will also exist. With the passage of the cold front Sunday afternoon/evening, winds shift to westerly and the severe threat ends. Winds will diminish slightly behind the front, but breezy conditions are expected to continue through Sunday night. Rain chances also continue through Sunday night as a new surface low starts to deepen over the mid-Atlantic coast and the wrap-around precipitation on its western periphery lingers over the area. && .LONG TERM /MONDAY THROUGH FRIDAY/... KEY MESSAGES: - Cooler weather returns next week - Periodic rain chances through the middle of next week ------------------------------------------------------------------- The upper trough begins to exit eastward Monday allowing height rises as a short wave ridge slides across the region. Drier conditions and clearing skies are anticipated Monday. High temperatures are expected to fall back towards normal on Monday behind our cold front and remain near to slightly below normal through the remainder of the forecast period. Ensembles are in rather strong agreement that another digging long wave trough quickly chases ridging out by Tuesday. This trough brings with it another chance for rain and possibly storms with machine learning models even hinting at low end severe probabilities. After this the long wave pattern becomes a little more muddled as ensembles diverge on where the long wave trough stalls. However, most ensembles are in agreement that several short waves round the base of the trough as it lingers across the eastern Great Lakes through next week. This activity is expected to keep rain chances up as we move late into next week. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... VFR conditions are expected to prevail across the region with light winds. Mid to high- level clouds begin to increase from the west this evening as a trough approaches the Great Lakes region. There is a chance for light rain/drizzle to pass north of Pittsburgh between 03Z and 12Z Saturday, though ceilings will remain VFR given the presence of sufficient dry air in the low levels. PROB30s for light rain and slight reductions in VFR ceilings were included at FKL/DUJ to reflect this potential. .OUTLOOK... A low pressure system will move across the region Sunday, bringing widespread precipitation and associated reductions in cigs and vis. A strong gradient wind field accompanying this system will likely result in increasing sfc winds after sunrise Sunday. By mid-afternoon, thunderstorm chances will rise ahead of the approaching cold front, and depending on environmental conditions, some storms could reach severe criteria. In the wake of the front, periods of rain showers, lower cigs, and gusty winds may persist into Monday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Cermak NEAR TERM...Cermak/Milcarek SHORT TERM...Cermak LONG TERM...AK AVIATION...Cermak/Hefferan