Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 211420 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1020 AM EDT Sun Apr 21 2019 .SYNOPSIS... A slow moving cutoff low will drift from the central Appalachians today to the Mid Atlantic coast Monday. Clouds and a few scattered showers will linger today for much of the region before mainly dry weather returns Monday as the system moves away from our area. Dry weather will last through much of Tuesday before a cold front brings another round of showers late Tuesday and Tuesday night. && .NEAR TERM /THROUGH TONIGHT/... Today and tonight a cutoff low will drift ever so slowly from the central Appalachians to the Mid Atlantic, with an old associated inverted trough surface and aloft extending up into the eastern Great Lakes. The cutoff low is steadily filling, leaving just weak forcing for ascent across our region. Much of the focus for showers today into this evening will be driven diurnally and by terrain and differential heating boundaries. The latest high-res and global guidance is in fairly good agreement in suggesting the best chance of scattered showers will be this afternoon from the interior Southern Tier through the Finger Lakes to the Tug Hill region. If enough sunshine develops there could be a few slow moving convective downpours, but this seems more likely to the south and east of our area. The diurnally driven showers will mostly end by early evening. The one exception may be across portions of Lewis and Oswego counties, where a weakly convergent surface boundary will keep a chance of showers going tonight, and even into early Monday morning. Otherwise most of tonight will be dry. As the cutoff low slowly weakens, there will be little to no flow today and tonight through the lowest 15K feet of the column. This will keep much of the low level moisture in place, and may result in low stratus and fog becoming prevalent again later tonight into early Monday morning. Similar to the past few days, there will be a large range in temperatures across the region today. Western NY will likely keep low clouds much of the day, and will subsequently remain quite cool with many areas only seeing highs in the upper 40s, and even low to mid 40s right along the lakeshores. Meanwhile across Central NY into Lewis County, there will be much less in the way of low cloud cover. This will allow for temperatures to climb into the low to mid 60s. Lows tonight will be in the low to mid 40s in most areas, with some upper 30s possible in the cooler Southern Tier valleys. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... The cutoff low along the Mid-Atlantic coast will ever so slowly pull further off shore and then lift NNE while an upper level ridge wedges in across the lower lakes on Monday. While this occurs, lingering moisture on the outer fringes of this slow departing low will continue to hamper interior sections across the North Country with a chance of a few showers. Meanwhile, with the ridge building in aloft and high pressure at the surface expect mainly dry conditions across Western NY with partly sunny skies developing over the course of the day. With increasing sunshine and a warming air mass aloft, H850T bumping up +8C to +10C, it`s expected to become very pleasant across the forecast area with highs in the mid to upper 60s for most locations. Although, it will be notably cooler along the lake shores and just inland from the lakes. Monday night, shortwave energy and a strengthening surface reflection will track out of the Midwest towards the SOO of Michigan. While this features tracks NE southerly flow will develop and pick up across the lower lakes overnight. This will temper temperatures overnight with fairly mild conditions expected with lows only falling back into the upper 40s to lower 50s. Tuesday, the deepening low pressure system will continue to steam ENE across Lake Huron and then on to Ontario/Quebec Canada by late in the day. As the low tracks into Canada it will send its trailing cold front towards the Lower Lakes. Associated height falls with the arrival of the pre-frontal trough and daytime insolation will likely lead to showers and thunderstorms developing out ahead of the cold front. With that said, forcing along the front will again likely lead to a second round storms forming as the front crosses the eastern Great Lakes Tuesday evening. Otherwise, it will be a warm and somewhat of a muggy day ahead of the front as high temperatures climb into the low/mid 70s. Tuesday night, the low pressure to our north will continue to trek slowly east with its trailing cold front exiting the region. Showers and thunderstorms will come to an end from west to east, although a few showers may linger into Wednesday across the St Lawrence valley as the low passes by to the north. With some clearing taking place, lows overnight will fall back into the 40s for most locations by sunrise. Wednesday, under NW`erly cyclonic flow a drier and cooler air mass will advect into the lower lakes along with surface high pressure building southeast into the region. With a cooler airmass in place (H850T 0C to -3C), look for high temperatures to top out in the 50s to lower 60s across the forecast area. Wednesday night with mostly clear skies and surface high pressure moving overhead temperatures will drop back into the low 40s across Western NY with some readings in the 30s east of lake Ontario. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... While a progressive split flow will still be in place at the start of this forecast period...a phasing of the branches over the eastern third of the country is suggested by the bulk of medium range ensemble members. Fortunately there is not enough amplitude in the pattern to make this phasing very significant. This should render the occasion as fairly benign with nothing more than a complex frontal passage Friday. The weekend looks dry after the frontal passage with strong ridging building east across the eastern Great Lakes. Otherwise...our region will really have little weather to deal with while temperatures will average close to...or just a bit above late April norms. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... Widespread IFR and LIFR CIGS will continue through this morning across much of the area. The low stratus is developing on the cold side of a sharp frontal zone, where a steep low level frontal inversion is trapping abundant low level moisture. Areas of fog will be confined to the southern tier of New York through 16z, and will not impact any TAF sites. The low stratus will slowly improve this afternoon, with most locations returning to MVFR CIGS by mid afternoon. There is little to no push to remove low level moisture today and tonight with slack flow through the lowest 15K feet of the atmosphere, which will allow much of the low level moisture to remain. As a result, low stratus and fog may make a comeback tonight with IFR conditions becoming more widespread once again after about 04Z Monday. Outlook... Monday...Early morning IFR in fog/stratus, otherwise VFR. Tuesday through Thursday...Mainly VFR with a chance of showers. && .MARINE... Winds will remain very light today through Tuesday morning with little in the way of wave action. The next period of stronger winds will arrive later Tuesday through Wednesday as a cold front crosses the region. Winds and waves may approach Small Craft Advisory levels during this time frame. && .EQUIPMENT... The KBUF WSR-88D radar will be down most of this week for a scheduled upgrade. The radar will be down beginning Monday morning April 22, with a planned outage lasting 5 days until Friday April 26. During the upgrade, the transmitter will be refurbished including the installation of new fuses and cables. Some of the components being replaced are original to the radar, which is now over 20 years old. The transmitter refurbishment is the second major project of the NEXRAD Service Life Extension Program, a series of upgrades and replacements that will keep our nation`s radars viable into the 2030`s. This is the second project in the NEXRAD Service Life Extension Program. The first was the installation of a new signal processor. The last two phases of the project are the refurbishment of the pedestal, and refurbishment of equipment shelters. All phases are expected to be complete in 2022. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Hitchcock/TMA NEAR TERM...Hitchcock/TMA SHORT TERM...AR LONG TERM...AR/RSH AVIATION...Hitchcock/TMA MARINE...Hitchcock/TMA EQUIPMENT...Hitchcock

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