Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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679 FXUS61 KBUF 031902 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 302 PM EDT Wed Jul 3 2024 .SYNOPSIS... Our stretch of rain free weather will come to an end later this afternoon and evening when a weak cold front will generate some showers and drenching thunderstorms. While most areas will then be rainfree for the Fourth of July, there will only be minimal relief from the heat and humidity. The next round of widespread showers and a few thunderstorms will then arrive Friday night. && .NEAR TERM /THROUGH THURSDAY NIGHT/... A broad longwave trough and attendant surface low over northern Ontario Province this afternoon will shift northeast into Quebec across Hudson Bay later tonight. Additional shortwave energy well to the south of this low is moving across southern Ontario in tandem, with its associated cold front currently across Michigan and the central Great Lakes. Deep SSW flow and moisture advection within the warm sector of this system is causing a rather sultry afternoon to unfold with much more heat and humidity compared to the last couple of days. Temperatures have climbed well into the 80s in most spots with corresponding Tds in the upper 60s to near 70. While so far it has remained dry today, a prefrontal trough will slowly work its way through the eastern Great Lakes from west to east later this afternoon and through this evening. A 40kt LLJ moving into the region along this feature will allow convection to blossom across the region, with showers and a few thunderstorms first expected to first develop across the Southern Tier where instability is greatest. More widespread convection will spread into areas north and northeast as the prefrontal wave/LLJ move eastward, though these showers/storms may lose some steam as the jet weakens in strength. On the flip side, there is some uncertainty in how quickly the deeper moisture pulls away behind the trough, which could allow additional showers/thunderstorms to develop late tonight as additional weak forcing arrives ahead of the primary cold front. In any case, PWATs nearing 2" within the soupy airmass ahead of these boundaries will support a few torrential downpours in the heavier showers/storms. Despite bulk shear values increasing to near 40kts with the arrival of the LLJ, the somewhat unfavorable timing of the prefrontal trough and poor mid level lapse rates should inhibit the severe potential. Otherwise...It will be a rather muggy night with lows in the upper 60s to low 70s and plenty of residual humidity. Shower coverage will taper off late tonight into early Thursday morning as the frontal boundary moves south and stalls across Pennsylvania. Mainly dry weather will then persist through Independence Day as the better moisture and forcing for precipitation remains well to our south, but an isolated shower or thunderstorm can`t be ruled out across the Southern Tier and southern Finer Lakes region. With very little of an airmass change on the `cooler` side of the boundary, expect another warm and humid day, though not quite as oppressive. Highs will range in the low to mid 80s with dewpoints still well into the 60s. Mainly dry weather for Thursday night as weak surface high pressure remains over the region. Light winds at the surface and aloft will make any firework smoke slow to clear. Lows will again be warm, ranging in the mid to upper 60s. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... Potent southeasterly flow will encompass the area on Friday. This flow will strengthen through the afternoon and evening hours, eventually turning more southerly. Off the deck, consensus 850 hPa temperatures surge toward +18 to +19C and momentum mixes through the boundary layer below that level. This combined with southeasterly flow, which relegates the lake influence to almost nil across the majority of the area, should all for temperatures to skyrocket on Friday. Highs should jump toward 90F, especially along the Lake Erie shoreline, Buffalo area, and the Genesee Valley. Friday`s warmth will be short-lived as the brisk southerly flow comes in advance of a southwesterly low-level jet nose that nudges into the area by Friday evening. This combined with a right entrance of an upper jet streak and solid DPVA should work on the remaining instability from the hot day on Friday to trigger widespread showers and thunderstorms Friday evening in WNY that spread eastward overnight. Organized ascent slowly translates across the area into Saturday, when the North Country should be the shower focus for the early half of the day at least. The remainder of the area looks to largely move into the mid-level dry slot of the system that will be occluding by that juncture over the northern Lake Huron region. Thus, deep layer dry advection and modest cold advection should at least temporarily cut off rain chances from west to east as the afternoon ensues on Saturday. Likewise, temperatures will be falling back in cold air advection to a bit below normal across at least the western half of the area. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Surface ridging and drier air moving in behind the cold frontal passage gives fairly high confidence that the area will see dry weather through Monday. Showers and thunderstorms return to the forecast for the Tuesday through Wednesday period as a mid level trough enters the region and a wave of low pressure tracks to our north bringing a cold front through the region. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... VFR fair weather early this afternoon will begin to deteriorate early this evening ahead of a pair of frontal boundaries approaching from the northwest. Showers and thunderstorms will likely develop and move into the region from west to east ahead of these boundaries, mainly after 21z. Cigs will begin to lower across the region tonight as showers begin to taper off in coverage with the passage of the second frontal boundary, mainly after 06z. While cigs are expected remain VFR at KBUF/KIAG/KROC, for areas south and east a mix of MVFR to IFR cigs are expected. Across the hilltops of the Southern Tier, localized LIFR cigs are possible (including at KJHW) A return to areawide VFR conditions expected after daybreak Thursday as the lower cloud cover begins to lift. No showers or thunderstorms expected at any of the TAF sites through the day, but an isolated shower/storm can`t be ruled out in the Southern Tier or Finger Lakes region. Outlook... Friday...Mainly VFR with increasing chances for showers and thunderstorms. Friday night...MVFR with showers and thunderstorms likely. Saturday...Mainly VFR with decreasing chances for showers. Sunday and Monday...VFR. && .MARINE... A cold front will approach the region this evening with an increasing risk for thunderstorms. A stiff southwest breeze will persist ahead of this front, with a moderate chop on the eastern nearshore waters through early tonight. In the wake of the cold front...fair weather will return to the region later tonight with subsiding southwest breezes. Looking ahead to the Fourth of July...gentle to moderate winds will be in place throughout the region. These winds will be from the southwest on Lake Erie and primarily from the west on Lake Ontario. Winds will then shift out of the east Friday, becoming southwesterly again by Saturday when the another round of SCAs appears likely. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...PP/RSH NEAR TERM...PP SHORT TERM...Fries LONG TERM...TMA AVIATION...PP MARINE...PP/RSH