LOCAL WEATHER CONDITIONS AT Franklin, Venango Regional Airport Temperature 50 F / 10 C Dew Point 39.2 F / 4 C Humidity 67% Wind Speed 9.2 Wind Direction SSE 150 Degrees Visibility 10 Miles Sky Conditions few at 7500 feet scattered at 11000 feet Current Weather Barometer 29.97 Inches Issued At 10/18/2025 08:56 $$ |
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FXUS61 KPBZ 181209 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 809 AM EDT Sat Oct 18 2025 .SYNOPSIS... Dry and unseasonably warm weather expected Saturday. A strong cold front will bring showers, thunderstorms, and gusty wind on Sunday. More seasonable temperatures return next week with periodic rain chances. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - A few light showers north of Pittsburgh through dawn - Dry and unseasonably warm today and tonight --------------------------------------------------------------- A few light showers will rotate through the area tonight, primarily north of US-422, where broad, weak ascent and better mid-level moisture reside. Dry sub-cloud layer air should prevent more than a few hundredths of an inch from these returns, and most should see a dry remainder of the overnight hours. Mid-level ridging will lose its grip today as a longwave trough digs across the central CONUS. As the ridge is pushed east, deep layer southwest flow establishes and increases moisture return, especially in the latter half of the day once the surface high moves far enough east to freshen up surface flow; dew points will start off the day in the upper 30s and end the day in the upper 50s. Morning cloud coverage should actually scatter out for a brief period this afternoon as a pocket of mid-level dry air works in, and this will allow highs to reach the upper 70s with even some 80 degree readings sneaking up into southeastern Ohio where warm advection will be strongest. Overnight lows tonight will have a high floor with dews in the upper 50s, increasing cloud cover, and a stiff southerly gradient flow promoting values that will be right around our normal *high* temperature this time of year. Can't entirely rule out a shower sneaking into our eastern Ohio counties on the periphery of a weak front that will quickly strengthen and bring active weather through here on Sunday, but chances are low. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... KEY MESSAGES: - Cold front passage Sunday offers high chance of rain and windy conditions - A possible convective line on Sunday afternoon could bring damaging wind gusts and an embedded tornado threat ---------------------------------------------------------------- As the central CONUS trough deepens and progresses east, associated surface cyclogenesis occurs across the Plains and rapidly lifts northeast toward the Great Lakes riding along a pre-existing weak boundary. The low will deepen rapidly and strengthen the boundary pulling it through here as a cold front on Sunday afternoon. This system will pack quite the dynamic punch and bring a two-fold threat of severe weather and strong wind gusts with it. The pressure gradient tightens between the aforementioned surface low and and departing high pressure then centered offshore. Deep layer flow through the entire column follows suit as 925 mb flow jumps to 30+ knots and 850 mb flow to 40+ knots. Tapping into the enhanced low-level flow and working in tandem with the tight pressure gradient, wind will be quite gusty on Sunday. The latest NBM continues to suggest a very high probability (>90%) for frequent wind gusts exceeding 30 mph across our entire area. Probability for occasional gusts over 40 mph continues its incremental increase now up to 50-80%. Above that, probabilities quickly drop off, with around a 10-20% chance of >50 mph, and thoughts are that this is likely tied to potential gusts along a convective line of showers/storms. We've now gotten this event within the range of most all of the CAMs to glean a better idea of how a narrow convective line along the cold front may evolve. As has been the case for the past couple days, limited instability still presents as the main hindrance with thick cloud coverage in the morning and some pre-frontal rain depicted by most of the CAMs which acts detrimentally for destabilization. Very few are all that excited about more than 100- 300 J/kg of MLCAPE. Despite this, strong forcing both along the front and synoptically with diffluent flow and shortwave- aided ascent should be sufficient in tandem with the limited CAPE to overcome the subpar thermodynamics. Deep layer shear still remains around 50-60 knots with low level shear in the 0-3 km layer around 30-35 knots. Given this, think it's plausible that we see a narrow, low topped convective line along the cold front that will bring a damaging wind and embedded tornado threat. With such strong background flow, it won't take much convective enhancement to get to 60 mph gusts. Low level shear vectors are southwesterly, so for embedded QLCS tornado threat, will be most concerned about any segments of the line that orient northwesterly to southeasterly to best utilize the available shear. Of note, there may not be a lot of lightning associated with this as thermodynamic profiles are well- saturated through ~500 mb and modeled equilibrium levels are hovering generally below -10C and therefore unfavorable for charge separation. With the passage of the cold front Sunday afternoon/evening, winds shift to westerly and the severe threat ends. Breezy conditions are expected to continue through Sunday night. Rain chances also continue through Sunday night as low level cold advection reinforces fumes of instability and we don't work dry air in immediately behind the boundary. && .LONG TERM /TUESDAY THROUGH FRIDAY/... KEY MESSAGES: - Cooler weather returns next week - Periodic rain chances continue through the week ------------------------------------------------------------------- Lingering showers should wrap up for most of the area on Monday morning as the mid-level trough completes its passage and flow veers to the west/northwest. Upslope enhancement with this direction and still persistent near-surface moisture could continue to squeeze out some drizzle in the ridges into the afternoon hours, but do think that dry air wins out and most all of the area should return to mostly clear skies by Monday evening. High pressure then briefly slides by to our south and keeps most of Monday night dry before another low pressure system makes its entrance into the Great Lakes region early Tuesday. Seeing some uncertainty both in timing and amplitude of the parent mid-level trough, but that has decreased some in the most recent ensembles. Feeling a bit more confident that the northern half of our area sees higher rain chances arriving sometime during the daytime hours on Tuesday in closest proximity to the surface low, but the majority of the region could get in on some mostly light rain showers. Fall looks like it returns by mid-week as the low departs with more seasonable temperatures in store but still low-end rain chances hanging around. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... Confidence remains high for VFR conditions through the TAF period as strengthening southwest flow promotes warm advection. High resolution model guidance suggest minimal low-level cumulus development this afternoon given prevailing subsidence. Warm air advection aloft early Sunday morning (pre-12z) may limit surface wind gusts, which would increase the potential for LLWS (35-45kts) due to a strong vertical wind profile immediately above the surface. However, confidence in this decoupling occurring is too low to warrant inclusion of LLWS in TAFs in this cycle. It will continue to be considered in future cycles as additional guidance becomes available. .OUTLOOK... A low pressure system will move west to east across the region between 15Z and 23Z Sunday, bringing rain showers and isolated thunderstorms. Some of the heavier showers and storms could be capable of producing wind gusts exceeding 50 kts given the strong flow aloft. Even outside of convection, downward mixing will result in gusts ranging from 30 to 40 kts, with peak non- convective gusts potentially reaching as high as 45kts in some of our typically windier locations. Scattered to isolated showers and gusty westerly winds are expected in the wake of the cold front late Sunday. The likelihood of MVFR to IFR cigs increases Sunday night into early Monday with cold advection within the boundary layer. High pressure will likely restore VFR conditions after sunrise Monday, however winds may continue to be breezy through at least mid week as probabilities for gusts exceeding 25 kts remain high (>60% chance) each afternoon through Wednesday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...MLB NEAR TERM...MLB SHORT TERM...MLB LONG TERM...MLB AVIATION...Cermak |