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 Wed Apr 25 2018 .SYNOPSIS... Low pressure will move northeastward across New England overnight and into the Canadian Maritimes on Thursday. Lingering showers behind this system tonight will give way to drier weather from west to east on Thursday as high pressure and drier air builds across the Lower Great Lakes. Two more weak systems will then bring additional periods of rain showers Friday and Saturday. && .NEAR TERM /THROUGH THURSDAY/... Overnight a modest shortwave trough along the mid Atlantic coast and a much stronger shortwave/compact closed low over Southern Ontario will gradually merge and consolidate across New York State...while supporting the continued gradual deepening of an attendant surface low tracking from the mid Atlantic coastline into New England. On the backside of this system...the combination of a westerly to northwesterly cyclonic upslope flow of cooler air...increasing wraparound moisture...and lift attendant to the northern (and stronger) trough will support relatively high probabilities of additional rain showers across the bulk of our region...save perhaps for portions of far southwestern New York where activity should be much more scattered. Otherwise...moderately breezy conditions will also continue to develop across the region from west to east as the pressure gradient tightens between the aforementioned low and high pressure ridging eastward across the Upper Great Lakes...which should in turn help to largely scour out the bulk of any patchy fog that is still in place. Meanwhile...modest cool air advection will lead to overnight lows ranging from the mid to upper 30s across the Southern Tier to the lower 40s elsewhere. On Thursday the surface low will exit northeastward across the Canadian Maritimes as high pressure and much drier air builds eastward from the Ohio Valley/Upper Great Lakes into western New York. This will result in any lingering showers diminishing from west to east through the course of the day...with the activity hanging on the longest east of Lake Ontario due to the closer proximity of the low and lingering upslope flow. Following the departure of the showers...increasing subsidence and drying should lead to partly to mostly sunny skies developing across areas south of Lake Ontario during the late morning and afternoon hours...with some breaks of sun reaching the North Country by late in the day. Otherwise a lingering pressure gradient will keep breezy conditions in place...with afternoon highs expected to mostly range through the 50s. && .SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY/... A weak ridge of high pressure will build into the eastern Great Lakes on Thursday night with dry weather and clearing skies. Lows will be in the mid to upper 30s in most locations. Weak low pressure will track roughly from eastern Virginia to Southern New England on Friday. There remains some model disagreement on the exact track, with the GFS a bit further north and wetter than most other model guidance. There is at least a chance that showers will clip southern and eastern portions of the cwa on Friday. Expect highs to be in the upper 50s to lower 60s. By Friday evening a northern stream trough will approach Western NY which will result in a chance of showers for the rest of the area. Increasing cold advection will drop temperatures back into the mid to upper 30s for lows by late Friday night, with lower 40s east of Lake Ontario. This trough will usher in colder air and below normal temperatures for the weekend. Model consensus has 850mb temperatures falling to - 8C as the core of the coldest air moves across the area Saturday night. This is cold enough for some limited lake enhancement and also to support snow showers where precipitation still lingers Saturday night into Sunday. Showers will be light with little if any accumulation, but this will be perhaps one last taste of winter before the warm up next week. The forecast hedges below most MOS based guidance due to high forecast confidence in the cold airmass and the likely lake enhanced cloud cover during much of the weekend. Highs will only be in the 40s over the weekend, with overnight lows near or below freezing on Saturday night. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... The anomalously cold upper-level trough will exit the region into the Canadian Maritimes Sunday night and Monday. Meanwhile, building 500mb heights and an expansive surface high over the Tennessee Valley will become centered along the Carolinas which will initiate a strong warning trend across our region. The surface high along the Carolinas will pump up a much warmer air mass into the Ohio Valley and Great Lakes which will send high temperatures soaring some +15- 20F degrees above climo by Wednesday with mid-upper 70s, even a few 80F readings. Late in the week, latest guidance shows a potent shortwave dropping southeast out of Canada across the Great lakes while several waves ride northeast along a frontal boundary to our west. This will likely bring increasing chances for showers Thursday and Friday. Otherwise, look for relatively quite weather the first half of the week with dry conditions and more like summer. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Low pressure over New Jersey and southeastern New York will lift northeastward into New England overnight and then into the Canadian Maritimes on Thursday. In its wake...high pressure and much drier air will build eastward into the region on Thursday. Wraparound moisture behind the low will maintain some lingering showers and widespread IFR to MVFR ceilings across the region over night...with the worst conditions found immediately downwind of the lakes and also across the higher terrain. While some remnant patchy fog is still leading to some spotty IFR/MVFR visibilities this evening...the fog and any attendant reductions should continue to largely diminish overnight as surface winds turn moderately breezy and help to more effectively mix the boundary layer. On Thursday we can expect improving conditions as the high builds eastward into our region and brings an end to any showers followed by a west to east clearing trend...which will result in flight conditions improving to VFR in most areas by the end of the day. The one possible exception to this will be the higher terrain east of Lake Ontario...where some MVFR cigs may linger through sunset. Outlook... Thursday night...VFR. Friday and Saturday...Mainly VFR with a chance of showers. Sunday...Mainly VFR with a chance of rain or snow showers east of Lake Ontario. Monday...VFR. && .MARINE... Surface low pressure over New Jersey will continue to deepen overnight as it lifts into New England...with westerly winds freshening overnight into Thursday. This will lead to sufficient waves and winds on the southern and eastern shores of Lake Ontario for Small Craft Advisories into Thursday night. Lighter winds and waves are then expected through Friday...with waves perhaps building again under westerly flow on Saturday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 8 PM EDT Thursday for LOZ043. Small Craft Advisory until 5 PM EDT Thursday for LOZ042. Small Craft Advisory until 11 PM EDT Thursday for LOZ044- 045. && $$ SYNOPSIS...JJR/Smith NEAR TERM...JJR/Smith SHORT TERM...Apffel LONG TERM...AR AVIATION...JJR/Smith MARINE...JJR/Smith

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