Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 281745 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 145 PM EDT Sat Mar 28 2020 .SYNOPSIS... A warm front will slowly cross the region tonight, followed by low pressure moving from the central Great Lakes to just north of Lake Ontario Sunday through Monday. This will produce periods of rain across the region through the rest of the weekend, with a few showers lingering Monday and Tuesday as the system moves very slowly off the New England coast. A few wet snowflakes may mix in Monday night and Tuesday morning as colder air moves into the region. && .NEAR TERM /THROUGH SUNDAY NIGHT/... Radar imagery showing steady rain drifting slowly northeast across the area, with most of the rain now focusing from the Niagara Frontier eastward across the Genesee Valley to points southeast of Lake Ontario. This area of rain will continue to drift ENE and weaken through the rest of the afternoon as the initial wave of warm advection and DPVA weakens as it moves into dry air and subsidence. The steady rain will taper off to scattered light showers, and may end altogether by late afternoon across Western NY. Following the break in organized rain this evening, warm advection and moisture transport will increase ahead of a warm front moving into the eastern Great Lakes. Isentropic upglide and moisture transport will be enhanced on the nose of a 40-50 knot low level jet, with some added support from a mid level vorticity maxima. This will bring another period of fairly widespread rain to the region later tonight through Sunday morning. Elevated instability will gradually increase from southwest to northeast, and this will support a chance of a few embedded thunderstorms as well. Convection will be rooted well off the surface above a low level stable layer, which will likely keep any convective wind risk minimal. The steady, warm advection driven rain will end from southwest to northeast on Sunday as the warm front moves across the eastern Great Lakes. There will likely still be a few showers around for the rest of the day, supported by increasing large scale ascent ahead of the mid level trough and the approach of the surface cold front late in the day. Weak instability will also continue through Sunday, supporting a chance of a few more scattered thunderstorms with the warm front in the morning, and then again late in the day along or just ahead of the cold front. If there are enough breaks in the rain and dense overcast, the instability may become more surface based later in the afternoon across Western NY, which would support a low chance of a few stronger storms. It will become quite windy Sunday, from a few different mechanisms. First, a strong 50-60 knot southerly low level jet will cross the eastern Lake Ontario region during the morning and midday hours. This will produce a brief period of enhanced downslope winds along the northward facing slopes of the Tug Hill Plateau, with gusts of 40-45 mph possible. Second, southwest winds will become gusty across Western NY during the afternoon as lapse rates steepen with the approach of the surface cold front. This may also produce gusts of 40-45 mph. Both of these setups look marginal for wind advisory wind gusts for any length of time, but we will continue to monitor model trends. Temperatures will begin to rise through the 50s later tonight across Western NY, and rise through the 40s east of Lake Ontario as warm advection and southerly downslope winds increase. Temperatures will then soar on Sunday after the steady rain ends. Expect highs well into the 60s in most areas, with low 70s a possibility across Western NY away from the cooling influences of the lakes. The eastern Lake Ontario region will see highs in the 50s. The cold front will sweep east across the area during the first half of Sunday night. Showers and isolated thunderstorms along the cold front will end from west to east. Deeper wrap around moisture and forcing from the approaching mid level cutoff low will then bring an increasing chance of showers again late Sunday night, first across Western NY and then spreading east across the rest of the area during the pre-dawn hours of Monday. It will remain quite windy Sunday night, with gusts of 30-40 mph common across the region as colder air pours back into the eastern Great Lakes. && .SHORT TERM /MONDAY/... Low pressure will move very slowly east across southern Ontario, just north of Lake Ontario Monday. Abundant wrap around moisture, ascent from the mid level trough passage, and convergence east of the lakes will continue to support scattered to numerous showers. The best coverage will be found east of Lake Ontario, with an added boost of upslope flow into the Tug Hill region. It will be much cooler, with highs only in the 40s in most locations along with winds gusting up to 30 mph. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... For the long term teleconnections suggest a blocking pattern forming, not that unusual for this time of year as we head into the beginning of April. The latest North Atlantic Oscillation forecasts from the Climate Prediction Center suggest the NAO becoming negative this period...with this negative index favoring blocking patterns over the eastern half of North America. A look at the models (GFS, ECMWF, Canadian) and their ensembles also depicts an amplified, blocking pattern, though where an upper level trough will focus is still uncertain. This trough, likely to close off in a blocking pattern may lie across the Great Lakes (a wetter solution for our region), or closer to the western Atlantic (not as wet and allows for milder air to sneak into the western zones). For the forecast, chances for mainly rain showers will be through this period, with high temperatures running slightly below normal, and overnight lows near normal. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... The first batch of rain will continue to move east across the area and weaken this afternoon, with most locations then seeing a break in steady rain from late afternoon into this evening. The next round of rain will then cross the region from southwest to northeast later tonight through Sunday morning, with a chance of a few weak, embedded thunderstorms during this time as well. VSBY will drop to MVFR and brief IFR at times in the steadier and heavier rainfall this afternoon through Sunday morning. MVFR CIGS will become more widespread at lower elevations from southwest to northeast this afternoon through this evening, with IFR for higher terrain. Overnight IFR will become more widespread across the lower elevations of Western NY, including KBUF and KIAG. Widespread IFR CIGS will continue Sunday morning across Western NY, with MVFR east of Lake Ontario. The steady rain will taper off from west to east Sunday afternoon, to be replaced by a few more showers and isolated thunderstorms as a cold front crosses the region. CIGS will improve to mainly VFR at lower elevations from west to east, with some MVFR lingering across higher terrain and in any showers that develop. Finally, low level wind shear will develop Sunday as a strong 50+ knot low level jet crosses the region. Outlook... Sunday night and Monday...MVFR/IFR with showers likely. Tuesday...VFR/MVFR with a chance of showers. Wednesday and Thursday...Mainly VFR with a chance of showers. && .MARINE... Moderate ENE winds will continue to produce Small Craft Advisory conditions through tonight on the western portion of Lake Ontario. Winds will become southeast by Sunday morning and increase along the Lake Erie shore and also the eastern portions of Lake Ontario, which may require additional Small Craft Advisories. Winds will then become southwest later Sunday afternoon through Monday, producing more Small Craft Advisory conditions on Lake Erie. Winds will be somewhat lighter on Lake Ontario through this period, but still strong enough to produce choppy wave action. && .HYDROLOGY... Several rounds of rainfall will cross the eastern Great Lakes this weekend, with the heaviest and most widespread rain late tonight through Sunday morning as a warm front crosses the region. Total rainfall amounts through the weekend will reach 1.25-1.75 inches across the western Southern Tier, and 0.75-1.25 inches across the rest of the region. Locally higher amounts are possible in thunderstorms. These rainfall amounts will result in rises on area creeks and rivers, but latest RFC forecasts suggest all the larger rivers will remain within their banks. The Allegheny River and upper Genesee Rivers will see the greatest rises and will need to be monitored closely. Both of these rivers have headwaters in northern PA, which may see higher rainfall amounts. Beyond the rivers, the rain will result in minor ponding of water in low lying and poor drainage areas this weekend. Will maintain a mention in the HWO to highlight the small chance for flooding with this system. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 5 AM EDT Sunday for LOZ042. && $$ SYNOPSIS...Hitchcock NEAR TERM...Hitchcock SHORT TERM...TMA LONG TERM...EAJ/Thomas AVIATION...Hitchcock MARINE...Hitchcock HYDROLOGY...Hitchcock

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