Area Forecast Discussion
Issued by NWS Buffalo, NY

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614 FXUS61 KBUF 280815 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 415 AM EDT THU JUL 28 2016 .SYNOPSIS... A weak cold front across the region will produce a few stray showers and thunderstorms across Western NY and the Finger Lakes region today. Weak high pressure across the region Saturday should limit any shower activity to near the PA state line, while scattered shower and thunderstorm chances increase again Saturday night through Sunday night as a wave of low pressure tracks through the region. && .NEAR TERM /THROUGH TONIGHT/... A broad cyclonic flow aloft with a nearly 100 knot, 250mb jet will persist across the region today with a corresponding weak surface cold front. In the right entrance region of this jet streak, a wave of low pressure seen on WV imagery across the Ohio valley this morning will track just to our south and east by later this afternoon and overnight tonight. Mid-level lapse rates under the upper-level broad trough will be enough to support a few spotty showers and thunderstorms inland from the lakes with diurnal heating today. However, forcing across our forecast area will remain very weak, and thus convection will be tied to enhanced low-level convergence from orographic and lake breeze influences. Thus have chance PoPs for the interior Southern Tier and northern Finger Lakes. The low chance for afternoon convection will also linger over the Saint Lawrence Valley closer to the broad upper trough over Quebec. With all of this, today will be, by and large, a dry day across the region, with 850 mb temps +16/+17C supporting high temperatures in the mid to upper 80s and increasing cloud cover through the day. Winds will also remain fairly light and mainly driven by local lake breezes. By tonight, the aforementioned wave will track through central PA and into central and eastern NY, largely skipping the forecast area to the south and east. However, cannot rule out a few isolated to scattered showers and thunderstorms mainly limited to the interior Southern Tier. Temperatures will remain in the upper 60s in the lake plains with low 60s across the higher terrain and North Country. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... On Friday a southern stream shortwave and associated surface low will move from the northern Mid Atlantic states into southern New England. This system will produce significant rainfall along its path, but unfortunately for drought stricken western NY this rainfall will remain well to our southeast. Our region will be left with a modest increase in deep layer moisture Friday well to the north of the surface low. A very weak northern stream surface cold front will sag slowly south across the area on Friday and may provide a focus for isolated to widely scattered showers and thunderstorms. A multi-model consensus places the best chances for these scattered showers across the Southern Tier where better moisture and instability will be found, with lesser chances extending northward to the Niagara Frontier and Greater Rochester areas. High pressure over Quebec will likely keep the Saint Lawrence valley dry. Any showers that form on Friday will end from northwest to southeast Friday evening as the surface low moves east into the North Atlantic, with the northern stream cold front moving south into PA. Drier air will advect into the region overnight on low level north to northeast flow with clearing skies and lowering dewpoints. Model guidance begins to diverge as early as Saturday with the track and timing details of the next wave. In a general sense, another wave of low pressure is forecast to move through the Ohio Valley and towards the northeast states. A fair number of operational and ensemble models take this second wave a little farther north than the first, giving some hope for rainfall across our region. The GFS is closest to previous forecast continuity, with a weak wave moving through PA later Saturday night and Sunday with showers crossing western and central NY. The new 00Z ECMWF has trended faster with this system, with most of the rain arriving Saturday and Saturday night. The Canadian GEM has slower timing like the GFS, but is much stronger and farther northwest with the surface wave. Given the model differences, the best option at this time is to stick close to previous continuity, with a mainly dry Saturday followed by increasing rain chances Saturday night and Sunday, with the greatest chances across the southern portion of the area. Temperatures will be a little cooler than recent weeks and very close to mid summer averages, with highs in the lower 80s across lower elevations and upper 70s higher terrain Friday through Sunday. Lows Friday night and Saturday night will be in the low to mid 60s in most locations, with mid to upper 50s in the cooler Southern Tier valleys and east of Lake Ontario. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... A progressive low amplitude pattern will remain in place along the Canadian border through early next week with dominant ridging remaining in place from the central Plains to the southeast states. The wave of low pressure passing near the region over the weekend will move to the east coast Sunday night with any showers and scattered thunderstorms ending from west to east. High pressure will then build into the Great Lakes region Monday and Tuesday with a return to dry weather. The surface high will drift to the east coast by Wednesday and still remain close enough to keep the next system and deeper moisture at bay, with a continuation of dry weather. Temperatures will start next week not far from average with highs in the lower 80s on Monday. The heat will build again by midweek as the surface high moves to the east coast and deep southwesterly return flow develops. This will boost high temps into the upper 80s by Wednesday. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Expect mainly VFR conditions today. The exception is at JHW where patchy fog is possible through the early morning, resulting in variable vsby through daybreak. This should average around 2SM, but could range wildly. A front will gradually drop south across the area today, and this combined with lake breeze boundaries may result in scattered showers and possibly a thunderstorm Thursday afternoon. Coverage should be quite spotty, and largely avoiding TAF sites. Outlook... Tonight...Mainly VFR with a chance of showers and thunderstorms. Friday through Sunday...VFR/MVFR with a chance of showers and thunderstorms. Monday...VFR. && .MARINE... Weak flow today will keep mainly lake breeze dominated winds and minimal waves on the lakes through this evening. Then, a wave of low pressure will track from central PA to east central NY supporting a freshening northeasterly wind, especially on Lake Ontario where waves may approach small craft criteria toward Friday morning. Otherwise high pressure will build in across the lower Great Lakes later Friday and into Saturday resulting in diminishing winds and waves. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...CHURCH NEAR TERM...CHURCH SHORT TERM...HITCHCOCK LONG TERM...HITCHCOCK AVIATION...CHURCH MARINE...CHURCH is the U.S. government's official web portal to all federal, state and local government web resources and services.