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Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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237 FXUS61 KBUF 142319 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 719 PM EDT Wed Aug 14 2024 .SYNOPSIS... High pressure centered over the Lower Great Lakes through Thursday will guarantee fair dry weather for much of western and north central New York. The area of high pressure will exit to our east Thursday night, opening the door for a large, slow moving storm system to impact our region later Friday through the upcoming weekend. The most unsettled conditions will be Saturday and Sunday when we can expect frequent shower activity. && .NEAR TERM /THROUGH THURSDAY NIGHT/... We can anticipate another beautiful night across the region, as a large area of surface high pressure remains positioned over the Lower Great Lakes. Thursday will feature sun filled skies under the nearly stationary surface high, but it will be a little warmer with temperatures climbing into the low to mid 80s. The area of high pressure will drift away to our east during the course of Thursday night, slowly losing its control over the weather across the area in the process. While dry weather will remain in place, expect an increase in high level clouds across far western New York. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... The longwave pattern across the CONUS will evolve to bring the forecast area a much more unsettled stretch of weather moving towards the end of the week. This will come in the form of a deep longwave trough digging south from Canada to the Ohio Valley across the Great Lakes, flanked by ridges of high pressure across the Rockies/central Plains and across the Canadian Maritimes. A cyclonically curved jet streak rounding the base of this trough will allow for a steady transport of GOMEX based moisture into the eastern Great Lakes region, causing PWATs to sharply increase from west to east Friday and remaining elevated through Sunday, generally hovering in the 1.5-1.9" range. As these features slowly shift eastward through the weekend, the trough will become nearly vertically stacked while partially closing off in the 850-700mb layer, as TC Ernesto slowly climbs north across the western Atlantic. This will serve to slow the progression of the trough, with the mid-level axis likely remaining upstream through the period. In terms of sensible weather, our stretch of mostly dry weather will come to an end Friday and Friday night as a warm front and deep synoptic moisture lifts into the eastern Great Lakes. While the day should start off dry with just increasing mid/high cloud cover, shower and thunderstorm chances will ramp up from west to east by the afternoon. Convection could be as far east as the Genesee Valley by early Friday evening, with showers and a few thunderstorms `likely` ongoing in the western Southern Tier. Mid-range guidance only indicating about 400-600J/kg of CAPE and < 30kts of bulk shear in this area during peak heating, so while severe risk looks limited, there`s a small chance in a few isolated strong wind gusts Friday afternoon especially if any deeper convection that forms upstream in the Ohio Valley (where CAPE values will be much higher) manages to move into our region. A period of widespread rain with embedded thunderstorms, some of which could be heavy given the high PWATs, is expected Friday night west of the Genesee Valley. With a lack of daytime instability this activity should diminish some in coverage and/or intensity as it moves towards the Finger Lakes and eastern Lake Ontario region overnight. While there will likely be a brief break in the precip back across WNY late in the night as a small dry slot works into the region, the next slug of deep moisture will arrive back across the western zones by Saturday morning. Thereafter, with the trough and associated surface low slowly moving into the eastern Great Lakes, expect very unsettled weather with occasional showers and thunderstorms punctuating nearly the entire period. Coverage is expected to be fairly widespread during peak heating in the afternoon hours both days, though with large scale support present convection could persist well into (or even through) Saturday night. WPC has maintained a Marginal Risk for excessive rainfall across the entire forecast area for both Saturday and Sunday. In regards to temperatures this period. Friday and Friday night will be warm and humid, with highs in the upper 70s/mid 80s and mid 60s/low 70s respectively. Thereafter, a general day-to-day cooling trend is expected through the weekend. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... A stacked low pressure system will be directly over the eastern Great Lakes moving into Sunday night. This will likely displace the greater forcing for ascent just east of the region as diurnal instability falls off by Sunday evening. While this should reduce the overall coverage and intensity of convection overnight, given the proximity of the low, scattered showers and thunderstorms will continue to be possible. The mid-level trough axis should then slowly cross the region Monday quickly followed by a period of strong cold advection, with the latest suite of guidance trending a bit faster with this pattern overall. While a few showers or thunderstorms are not yet out of the question through Tuesday, have trended PoPs downward this period as the airmass with the front looks very dry. Should this trend continue to hold, could see Monday and especially Monday night into Tuesday being even drier than NBM/continuity. Surface high pressure should then guarantee a period of areawide dry weather Tuesday night, though with the cooler airmass advecting overhead, precip chances increase some again for Wednesday. Much cooler and less humid air will arrive with the front Monday and last through Wednesday. High temperatures will range from the upper 60s across the hilltops to the mid 70s across the lower terrain, while overnight lows will fall back in the 50s to near 60 each night. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... High pressure anchored over the Lower Great Lakes will continue to supply the vast majority of the region with fair VFR weather tonight through Thursday night. The exception to this will be patchy fog late tonight that could reduce vsbys to 2-4SM at sites like KJHW and KELZ. Outlook... Friday...VFR but with scattered afternoon showers and thunderstorms over the western counties. Saturday and Sunday...MVFR to IFR with occasional showers and thunderstorms. Monday...VFR to MVFR cigs with scattered showers and possible thunderstorms. && .MARINE... High pressure across the eastern Great Lakes will maintain quiet conditions on Lake Erie and Lake Ontario through Thursday. The light flow will favor the development of afternoon lake breezes through Thursday. A southeasterly flow will develop by Thursday night and Friday as a warm front approaches the region, but speeds should remain less than 15 knots. A general south-southwest flow develops behind the warm frontal passage for the weekend period as low pressure meanders north of the lower Great Lakes. Speeds could exceed 15 knots both Saturday and Sunday afternoons, so cannot completely rule out the potential for marine headlines this weekend. The risk for thunderstorms increases on the lower Great Lakes Friday through Sunday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...EAJ/RSH NEAR TERM...EAJ/RSH SHORT TERM...PP LONG TERM...PP AVIATION...EAJ/RSH MARINE...Apffel/EAJ/TMA