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Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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559 FXUS61 KBUF 161516 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1116 AM EDT Tue Jul 16 2024 .SYNOPSIS... Another cluster of strong to severe thunderstorms will cross the region from west to east today, with localized torrential rainfall and damaging winds possible. A few more showers and isolated thunderstorms will continue tonight through Wednesday as a cold front slowly crosses the eastern Great Lakes. High pressure will build into the Great Lakes Thursday and remain through next weekend, with an extended period of dry and less humid weather. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... ...LOCALIZED SEVERE THUNDERSTORMS LIKELY AGAIN TODAY... Our focus once again today is on severe weather potential. A large and well defined MCV is emerging from a decaying MCS over southeast lower Michigan late this morning is forecast by all guidance to cross the eastern Great Lakes today. Overall, the setup is very similar to yesterday, with the most notable difference being the timing of the feature, roughly 3 hours earlier in the diurnal cycle than the MCV yesterday. The MCV will move across Western NY through early afternoon, possibly too early to allow for sufficient destabilization to support robust severe weather potential. The arrival time from the Genesee Valley east into Central NY and the eastern Lake Ontario region will be late enough to allow for a window of sufficient destabilization to support a better chance of severe weather. Update nudged back timing slightly but otherwise a severe weather potential remains. SPC has issued a Severe Thunderstorm Watch for most of the area, and has also upgraded Central NY to an enhanced risk for severe weather. Severe Weather Potential... The strong MCV crossing the region today will again locally enhance the severe weather potential, with the mesoscale circulation providing more favorable low/mid level shear and convergence, particularly in the southeastern quadrant of the MCV. The early arrival of clouds and convection will limit destabilization in Western NY, with SBCAPE of up to 1000 J/kg by mid to late morning. Greater instability will develop from the Genesee Valley eastward with a few extra hours of diurnal heating before convection, with SBCAPE of 1500 J/kg or better. 0-6 km deep layer shear will be on the order of 30-40 knots based on the latest HREF mean, although locally higher values are possible as the MCV augments the low/mid level wind fields. Expect thunderstorms to expand rapidly across Western NY through early afternoon. The initial lack of strong instability may keep these storms sub- severe at first, although gusty winds and locally heavy rainfall is certainly possible. The instability and shear parameters along with organized mesoscale forcing from the MCV suggest the initial development across Western NY will grow upscale by midday to early afternoon, with high-res CAMS guidance suggesting storm mode evolving into short bowing segments with localized damaging wind risk from the Genesee Valley into Central NY and the eastern Lake Ontario region. Damaging winds will be the primary risk, with a secondary risk for large hail, and a low but non-zero risk of an isolated tornado given the influence of the MCV on the low level shear environment. The severe weather risk will end by early afternoon in Western NY, mid afternoon in the Genesee Valley, and late afternoon or early evening east of Lake Ontario. Heavy Rain Potential... PWAT values will remain in the 1.75"-2.0" range today. The very moist environment and relatively deep warm cloud depth will continue to support torrential downpours with any strong convection. The MCV if moving quite fast, and should allow the storms to maintain enough forward speed to keep the risk of flash flooding low. Nonetheless, any training may support a localized minor flood risk. A few more scattered showers and thunderstorms may develop later in the afternoon and evening along the southern edge of the Lake Erie breeze, mainly from the western Southern Tier into the Finger Lakes. These will gradually taper off through the evening. Overnight, the mid level trough and associated cold front will approach slowly from the northwest. Increasing large scale ascent and low level convergence ahead of these features will support an increasing chance of showers and a few isolated thunderstorms again late tonight, but with less coverage and intensity than today. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... A cold front will start this period on our western counties doorstep, with the front slicing across the region through the morning and early afternoon hours. A few showers, and later thunderstorms will remain possible along and ahead of this front. Greatest possibilities for thunder will be the Finger Lakes and east of Lake Ontario where greater daytime insolation and developing CAPE (MUCAPE of 500 J/KG) will be realized. A longwave trough will enter into our region Wednesday night with showers ending across eastern zones, and clouds thinning. Some patches of fog will be possible with still a fair amount of humidity to start the night. A much drier airmass will build across our region later Wednesday night and Thursday on a light northerly flow behind the passage of the upper level trough. This will promote fair weather for Thursday and Thursday night. Though temperatures will only be a few degrees cooler Thursday than Wednesday, the dewpoints at least 10 degrees cooler will be more noticeable. && .LONG TERM /FRIDAY THROUGH TUESDAY/... This will be a spectacular stretch of weather, with a broad ridge of high pressure expanding across the region. A weak cold front will drop southward across the region Sunday, but its passage should largely be rain-free with possibly an isolated shower east of Lake Ontario. Otherwise, there`s good model agreement providing high confidence in rain-free weather. Temperatures will be near normal with daytime highs averaging in the mid 70s to lower 80s and nighttime lows mainly in the mid 50s to lower 60s. A few colder spots early Friday morning, and again early Saturday morning could drop into the upper 40s east of both Lakes. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... An area of showers and thunderstorms associated with an upper level disturbance will arrive in Western NY by late morning, then move east across the rest of the area, reaching the eastern Lake Ontario region by mid afternoon. This will bring a likelihood of thunder and brief VSBY/CIG reductions across much of the area, including all the terminals. Some storms may be strong with localized high wind gusts. Mainly VFR conditions will follow later today behind this round of showers and thunderstorms. A few more storms may develop late afternoon through evening from the Southern Tier into the Finger Lakes, mainly east of KJHW and south of KROC. Tonight, the evening showers and thunderstorms across the Southern Tier and Finger Lakes will taper off. Overnight, an approaching cold front and mid level trough may produce a few more showers and thunderstorms with uneven coverage. Areas of MVFR/IFR CIGS will develop later tonight through Wednesday morning. Outlook... Wednesday...VFR/MVFR with a chance of showers and thunderstorms. Thursday through Saturday...VFR. && .MARINE... A period of moderate southwesterlies will develop on Lake Erie today, with Small Craft Advisory conditions this afternoon. Winds will be somewhat lower on Lake Ontario, but still enough to produce a moderate chop this afternoon and evening. Another cluster of thunderstorms will cross the eastern Great Lakes today, with locally higher winds and waves. The timing is earlier than yesterday, with the greatest chance of storms this morning through early afternoon on Lake Erie and western Lake Ontario, and midday through late afternoon for the eastern end of Lake Ontario. A cold front will cross the eastern Great Lakes Wednesday. West to northwest winds up to 15 knots will produce moderate chop at times Wednesday through Thursday on Lake Ontario, but winds and waves are generally expected to remain below Small Craft Advisory criteria. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Beach Hazards Statement until 8 PM EDT this evening for NYZ010- 019-085. MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ020. Small Craft Advisory until 11 PM EDT this evening for LEZ040-041. && $$ SYNOPSIS...Hitchcock NEAR TERM...Apffel/Hitchcock SHORT TERM...Thomas LONG TERM...Apffel/Thomas AVIATION...Apffel/Hitchcock MARINE...Apffel/Hitchcock