Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 260220 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1020 PM EDT Tue Apr 25 2017 .SYNOPSIS...
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Low pressure will move northward along the east coast tonight with a few scattered showers gradually ending overnight. Drier weather and summer-like warmth will then spread across our area Wednesday and Thursday...with temperatures surging well into the 80s in many places on Thursday. The next chance for rain will then arrive late Thursday and Thursday night when a cold front will cross our region and produces a round of showers and thunderstorms.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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Radar imagery late this evening showing scattered showers from just east of Rochester into the eastern Lake Ontario region. These will continue overnight, and a more concentrated area of showers moving northward through Central NY will likely bring a few hours of somewhat steadier showers east of Lake Ontario through the middle of the night. Farther west, a few isolated showers and scattered sprinkles have developed near the Niagara Frontier. These may persist for a few hours before dissipating overnight. Low pressure will move slowly north along the east coast tonight and Wednesday with the bulk of the more significant impacts staying well east of our area. A weak inverted trough and deeper moisture will drift across eastern NY tonight and early Wednesday morning, with the western edge of that clipping the eastern Lake Ontario region with a few showers. Otherwise the rest of the area should remain dry from late tonight through early Wednesday, with clouds lingering along the western periphery of the circulation of the east coast low. Wednesday afternoon the coastal low will move into southern New England, with a push of drier air moving out of the Ohio Valley and into the lower Great Lakes. Any lingering light showers will end east of Lake Ontario. Farther west, expect increasing amounts of sunshine across Western NY. As far as temperatures go, it will remain mild tonight with lows in the lower 50s in most areas, and upper 40s in some of the cooler Southern Tier valleys and Tug Hill region. Ongoing warm advection and increasing sunshine will allow temperatures to rise into the mid 70s Wednesday afternoon across Western Ny, with upper 60s to around 70 for the North Country.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH SATURDAY NIGHT/... Western and Central NY will be within the warm sector of a low pressure centered over the Michigan UP on Wednesday night. A nocturnal inversion with +15C to +18C air at 850mb along with dewpoints in the 50s will hold temperatures very mild overnight making for a nice night to keep the windows open. Low temps are only expected to slip back into a range of the mid 50s to about 60. The surface low over the Michigan UP is forecast to lift north into northeastern Ontario Canada through Thursday with a trailing cold front approaching western NY late in the day. An increasing southerly flow ahead of this front will continue to advect unseasonably warm and somewhat humid air north across the eastern Great Lakes. Mixing of near +18C 850mb air will make for a summer-like day Thursday. Most areas should see max temps in the low to mid 80s with a potential for readings to reach the upper 80s across the Genesee Valley. These will threaten record high temperatures across the region...which includes the following...84 at Buffalo (1984)...86 at Rochester (1990)...and 85 at Watertown (2009). This will certainly make it feel more like July rather than the end of April. While most of the day will be dry with above normal temperatures, the approaching cold front will bring the threat of late afternoon or evening thunderstorms Thursday. The combination of the very warm and modestly humid airmass looks to support surface-based CAPE values over 1000 j/kg and possibly above 2000 j/kg per 12z GFS. This available energy will also combine with 0-6km bulk shear values of 40- 50 kts making for am environment which could support strong to severe thunderstorms along and ahead of the cold front. The key for potential severe storms Thursday will be timing of convective initiation. If storms begin to fire in the mid to late evening where instability values are still quite high then the severe risk will be higher than if storms do not arrive until near or after sunset. The front looks fairly progressive so while any thunderstorm can contain heavy downpours, its looks less likely that training cells will bring a potential for any flash flooding. Gusty to damaging winds looks more likely with the high level of shear. Have held onto will likely POPs for showers and thunderstorms Thursday night shifting quickly west to east. Temperatures will remain mild behind the cold front on Thursday night with lows only expected to dip into the lower 50s. The cold front looks to be cleared to the east of the forecast area by Friday morning while the tail end stalls out somewhere across central PA. A narrow wedge of high pressure building in behind the front will make for a pleasantly warm and dry weather day. Temperatures look to still run above normal with highs expected in the mid to upper 60s with 850mb temps only slipping back to around +6C. Friday night and Saturday, the surface ridge exits to New England while a weak surface wave with associated 40kt low level jet shifts from the Ohio Valley to western NY. In this process it should lift the stalled front to our south back north as a warm front, stretching across western and central NY. As the surface wave system shifts along the stalled front it will bring a chance of showers Friday night and Saturday morning with a chance of thunderstorms possible in the Southern Tier Saturday afternoon where some instability is possible south of the warm front. Saturday night, a chance of showers will linger for all areas with the front still stretched across western and central NY although the 12z GFS suggests an inverted ridge of high pressure may make for a mainly dry night ahead of our next weather system. Temperatures Friday night will again slip back to around 50 with no access to a dry continental airmass then warm into the low to mid 60s Saturday with 70 possible south of the front near the PA border. Temps are forecast a bit cooler with a light northeast flow Saturday night expected to slip back into the mid to upper 40s. && .LONG TERM /SUNDAY THROUGH TUESDAY/... Sunday will feature more widespread chances of showers and thunderstorms as forcing and instability are enhanced by a low pressure system strengthening over the heart of the country. Southerly flow ahead of this system will bump the stalled front a little further north with moisture and instability interacting with the warm front causing the chances for showers and thunderstorms Sunday. The low pressure system looks to further deepen on Monday while lifting across Wisconsin. A cold front associated with this storm will approach the western NY Monday afternoon then shifting into central NY Monday evening bringing the risk for another period of showers and thunderstorms. While still pretty far out, instability should develop in the warm sector of the low across the eastern Great Lakes. While GFS CAPE profiles are not very impressive, we will again have some decent wind shear associated with a low level jet ahead of the cold front which could bring a risk of a few strong to severe storms. The cold front is forecast to shift across central and into eastern NY Monday night with a chance of showers and storms during the overnight. Frontal timing will be key again here for zeroing in on who sees showers and storms and who should be dry behind the front. On Tuesday, the surface low is forecast to shift northwest of Buffalo toward James Bay. This is a favorable track for a risk of gusty gradient winds downwind of the lakes as a 40-50+ knot low level jet mixes down in cold advection. Otherwise, the cold advection within a plume of low level moisture circulating the low will support a chance of some scattered showers. Temperature-wise, readings through will remain well above normal with daytime highs Friday through Sunday still expected to range between the mid 60s and lower 70s. Overnight lows look to run comfortably in the upper 40s to low 50s. As mentioned in a previous discussion, while temperatures are forecast above average, the exact magnitude of these departures will be highly dependent upon the exact position of the warm front. This feature will mark the dividing line between pleasantly warm spring conditions to its north and downright midsummerlike warmth to its south. Monday may be the warmest day of the period as the warm front lifts north of our region possibly setting the stage for another run toward 80 degrees should showers and thunderstorms hold off until late in the day. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
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Scattered sprinkles and light showers will continue through the early overnight, with somewhat steadier showers east of Lake Ontario. The rain will remain light, with mainly VFR VSBY. Most of the showers will end by around midnight, except for east of Lake Ontario where a few showers will continue overnight. CIGS are mainly VFR and will remain so through this evening. Overnight low level moisture will deepen and support increasing areas of MVFR with some local IFR possible across the higher terrain of the Southern Tier. The stratus will continue into Wednesday morning before lifting and scattering out into a VFR cumulus field by early Wednesday afternoon. These clouds will steadily diminish Wednesday afternoon with VFR prevailing. Outlook... Thursday...Mainly VFR during the day...with showers/thunderstorms and attendant MVFR then becoming likely late Thursday and Thursday night. Friday...Mainly VFR. Saturday...VFR/MVFR with a chance of showers. Sunday...VFR/MVFR with a chance of showers and thunderstorms.
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&& .MARINE... Low pressure will move slowly northward along the east coast through Wednesday and support a continuation of easterly winds on the Lower Great Lakes. Choppy wave action will continue on the west half of Lake Ontario through tonight but will stay under Small Craft Advisory conditions, with winds and waves slowly diminishing Wednesday. Wednesday night and Thursday winds will turn more southerly in advance of an approaching cold front...which will then cross the region along with some showers and thunderstorms late Thursday and Thursday night. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...HITCHCOCK NEAR TERM...HITCHCOCK SHORT TERM...SMITH LONG TERM...AR/SMITH AVIATION...HITCHCOCK MARINE...HITCHCOCK

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