Timberline Ski Resort Snow Report

425 FXUS61 KPBZ 180002 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 802 PM EDT Fri Jul 17 2026 .WHAT HAS CHANGED... Increasing confidence in severe thunderstorms on Saturday with upgrade to an Enhanced Risk for parts of our area. && .KEY MESSAGES... 1) Smoke begins to clear tonight/Saturday morning. 2) More widespread thunderstorm chances, along with severe and flooding risks, return on Saturday. 3) Return to seasonable temperatures next week with more storms possible on Tuesday. && .DISCUSSION... KEY MESSAGE 1... Ground-level wildfire smoke will wane overnight and Saturday morning as a result of a lifting warm front and rain washout. Additional smoke may return early next week, but should be noticeably less impactful. KEY MESSAGE 2... Friday into Saturday, the mid-level ridge axis will break down as a potent shortwave enters the Great Lakes region quickly diving southeast. Meanwhile, surface low pressure gradually deepens as it follows a similar track. Locally, the pressure gradient will tighten a bit in response ramping up southwesterly flow and pulling in moisture to offset mixing some with afternoon dew points likely in the low 70s and highs topping out in the mid 80s. As cooler mid-level air arrives with the wave, we`ll be primed with a moist and unstable environment awaiting the lift from the shortwave as well as a surface boundary which will be responsible for two rounds of thunderstorms, both with severe potential. The first round will be driven by more broad ascent from the shortwave and loose upper jet entrance region dynamics. Expect to see scattered development fire off after noontime in an environment with mean SBCAPE values from the REFS around 2500 J/kg and deep layer shear values around 20-30 knots. Directional shear may be a limiting factor to otherwise favorable supercellular mode with the initial round, though some enhancement with locally backed surface flow could elongate hodographs enough that a right moving storm could become supercellular with all hazards on the table, though hail likely is the least probable given rich deep layer moisture with PWATs nearing 2". By evening time, a surface front dives south across Lake Erie and into our northwestern PA counties likely just a bit before sunset. Ensembles suggest that there`s sufficient recovery in the wake of any scattered afternoon thunderstorms to support maintenance and intensification of storms along the boundary, and likely our prime window for more widespread coverage and impacts. Despite timing being after peak heating, mesoscale processes should allow for the line to keep its strength as it moves through most of our area. Deep layer column flow at this point will be unidirectionally westerly which points toward rapid upscale growth of storms along the boundary bringing a damaging wind threat. Despite 0-3 km shear values nearing 30 knots, the line-parallel orientation suggests that QLCS tornado potential should be rather low unless a surge occurs to the east or localized cell mergers encourage localized supercellular structures able to utilize environmental shear best. Heavy rain will be a threat as well with high PWAT values and a generally tall, thinner CAPE profile. However, with the progressive nature of the storms along the front, a flash flooding threat would likely be confined to urban areas and/or areas that receive several rounds of rain both from the initial round and then as the boundary moves through. Both HREF and REFS maximum one hour QPF peaks around 1.75" representing a worst case scenario hourly rainfall rate. This does exceed one hour flash flood guidance in urban areas, so will need to monitor this threat. WPC has maintained the Marginal Risk of excessive rainfall. SPC has upgraded the northern half of our area (roughly from PHD to PIT to IDI on north) to an Enhanced Risk and leaving the rest of the area in a Slight Risk. KEY MESSAGE 3... Mid-level northwest flow remains into early next week as West Coast ridging stays amplified. Sunday and Monday will be dry with lack of mid-level impulses and forcing, and temperatures dip back to normal. Another shortwave arrives on Tuesday and could bring with it a renewed severe weather threat. SPC has our area outlined in the day 5 outlook, though uncertainty remains both with timing and amplitude of the mid-level wave as well as a surface cold front. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Dry conditions prevail for most through 04Z, save ZZV, with IFR smoke remaining in place for most ports. As winds shift out of the south overnight, much of the near-surface smoke will be allowed to exit the region, with overall improvements expected between 03Z and 13Z for most (fastest recoveries for southern ports). Overnight, weak mid level lift may be enough to generate isolated precip chances along a shortwave, but confidence remains low. Some models allude to overnight storm potential, but most of the smoke-forced ones squash this for now, tending more towards widely scattered showers. Ports will primarily remain VFR. Into tomorrow morning, models then allude to a low-cloud deck advecting in as dew point recover in most southwest flow. The most likely scenario is an early day MVFR deck, which again, there is a low chance of shower or storm development, most likely north of PIT. Storms may bring gusty, erratic winds should they occur. This deck is expected to scatter and lift mid-day with mixing, before thunderstorms chances again, overspread the area in the later afternoon into evening hours as a cold front comes down from the north, with the highest chance of organized convection, erratic winds, and cig/vis restrictions overspreading the area from 20Z to 02Z from north to south. Outlook... Temporary visibility restrictions are possible Sunday morning before VFR returns Sunday and Monday under high pressure. Restrictions return in showers and thunderstorms on Tuesday with a cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Air Quality Alert until midnight EDT tonight for PAZ007>009- 013>016-020>022-029-031-073>078. OH...Air Quality Alert until midnight EDT tonight for OHZ039>041- 048>050-057>059-068-069. WV...Air Quality Alert until midnight EDT Saturday night for WVZ001>004-012-021-509>514. && $$ DISCUSSION...Rackley/MLB AVIATION...Milcarek