Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 211149 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 649 AM EST Thu Feb 21 2019 .SYNOPSIS... Low pressure will pass to our north, with a cold front moving east into New England today. High pressure will return for the rest of the work week before a much stronger system arrives this weekend. Rain will arrive Saturday night, then a very strong cold front will bring strong and possibly damaging winds on Sunday. && .NEAR TERM /THROUGH TONIGHT/... Low pressure centered across southern Ontario this morning will track into Quebec province during the day. Meanwhile, a cold/occluded front associated with this system will move east of the forecast area shortly after daybreak. Radar shows both drizzle along with some steadier showers east of Lake Ontario. Temperatures have risen above freezing in some locations, but mesonet shows that many areas still remain below freezing this morning. Because of this, the Winter Weather Advisory was extended for areas east of Lake Ontario. Otherwise, cooler air will build into the region behind the front with nearly steady temperatures in the mid to upper 30s today since cold air advection will offset daytime heating. The post- frontal air mass is not all that cold, with 850mb temperatures only dropping to around -11C. This is not cold enough for lake effect snow, but lingering moisture and upsloping may result in some light snow showers east of Lake Ontario today. It also will be quite breezy today, with wind gusts of 35 to 40 mph across the lake plains, and to 30 mph further inland. High pressure will expand across the Great Lakes region tonight, with any lingering upslope snow showers ending as winds diminish. Considerable cloud cover will hinder radiational cooling with low temperatures in the 20s. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Surface high pressure will cross the region Friday-Friday night with fair weather. Zonal flow that will begin to amplify Friday night in response to a deep trough across the southern Plains will promote temperatures a few degrees above normal. Saturday easterly flow will begin to increase through the day as the surface high pressure exits out to sea off the New England coastline. Much of the day will be dry, with clouds increasing ahead of a deepening storm system across the mid Mississippi Valley. A few rain showers are possible late in the day across the So. Tier, but it will be until Saturday night that much of the region receives rain. The amplified pattern, with southeasterly flow forcing milder air northward will spell plain rain for the region Saturday night. Deep moisture ahead of the mid-Mississippi trough will be transported across the Great Lakes region Saturday night feeding these areas of rain. Rain ahead of a warm front will spread across the region Saturday night, though greater duration and forecasted rainfall will be to the west and east of our region where isentropic lift will be greater. Overall rainfall Saturday night will range from a tenth to a quarter of an inch on average basin wide. Under strong warm air advection through the night temperatures will begin to rise in the evening (and just past midnight east of Lake Ontario). By the closure of Saturday night into Sunday morning much of WNY will likely be around 50F. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... ...WIDESPREAD DAMAGING WINDS LIKELY SUNDAY... The 00Z models continue to track a deepening, and anomalously deep low across Lake Michigan and near the SOO Saturday night and Sunday, with a 70 to 75 knot LLJ passing across the region Sunday and Sunday night. This deep low coupled with strong cold air advection (850 hPa temperatures dropping 12 to 16 degrees Celsius through the day), forcing from a passing isallobaric couplet and passing 1.5 PV tail (down to near 500 hPa) across the region will transport very strong winds down to the surface through the day Sunday, beginning in the late morning hours and continuing through the overnight period. As the 1.5 PV tail crosses the region Sunday afternoon behind a strong cold front, and potential for 60 knots of wind flow dipping below 1K feet, wind gusts at the surface could approach 70 mph downwind of Lake Erie and across the Lake Plain. Sunday morning will begin very warm with temperatures in the morning hours peaking well into the 50s across WNY. This warming may bring brief hydro concerns as any lingering ice jams across WNY could become dislodged. Fortunately there will not be a lot of run off from rain, with higher terrain melting snow causing stream flow increase. Additional rainfall Sunday will be on the order of a tenth or two. As the cold front crosses the region Sunday wind gusts will quickly strengthen from west to east, with damaging west-southwest gusts howling across the region. The strongest winds are expected Sunday afternoon through Sunday night. What will also make this wind event concerning will be the prolonged period of damaging winds...with gusts over 60 mph possible for a 12 to 18 hour period. This lengthy period of winds battering the region could increase the severity of the wind event. Regardless of when the peak wind gusts occur...the Sunday through Sunday night period will bear watching for a prolonged period of strong, damaging wind gusts across the entire region. Please keep in mind though that at this point...it is ONLY a forecast...albeit one with increasing confidence. It will be important to stay tuned to updated forecasts and possible statements/headlines as we progress through the rest of the week. Winds will remain strong into Monday morning as the 6hr pressure change between the exiting strong low pressure to the north and the approaching high pressure is on the order of 10-12 mb. Gusts of 40- 50 mph will likely continue into Monday. Cold air will also being moving into the region at this time and snow showers are expected with lake enhancement south-southeast of both Lakes. Minor accumulations are expected at this time to areas southeast of the Lakes. Colder air behind the Sunday storm system will bring below normal temperatures to close out the forecast period. There becomes a great deal of uncertainty Tuesday and into Wednesday with the evolution of the upper air pattern. While Tuesday may be dry, a passing upper level shortwave Wednesday may bring additional light snow to the region. There is still a good deal of timing, and strength of this next shortwave at this time. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... A cold front was moving from west to east and was just about to KART to start the 12Z TAF cycle. This will result in a few hours of IFR conditions there, but conditions should improve 1-2 hours after the frontal passage. Elsewhere, there will be mainly MVFR conditions today, with a persist stratus cloud deck expected. Drier air will build in during the day with a brisk southwesterly flow. This will help raise ceilings with sites improving to MVFR, and eventually VFR heading into the evening hours. Outlook... Friday and Saturday...VFR. Sunday...MVFR or IFR with rain, then snow. Strong winds. Monday...VFR/MVFR with scattered snow showers. && .MARINE... Low pressure will pass to our north, with a cold front moving east of Lake Ontario by late this morning. Southwesterly winds have increased behind the front, supporting small craft headlines across most of the area. A powerful storm system will cut through the Central Great Lakes Sunday and Sunday night. As this system rapidly deepens it will produce at least gale force winds on the Lakes, with storm force wind gusts likely. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Winter Weather Advisory until 10 AM EST this morning for NYZ006>008. MARINE...Small Craft Advisory until 4 PM EST this afternoon for LEZ020. Small Craft Advisory until 10 PM EST this evening for LEZ040-041. Small Craft Advisory until 4 PM EST this afternoon for LOZ030. Small Craft Advisory until 7 AM EST Friday for LOZ042>044. Small Craft Advisory until 4 AM EST Friday for LOZ045. && $$ SYNOPSIS...Apffel NEAR TERM...Apffel SHORT TERM...Thomas LONG TERM...HSK/Thomas AVIATION...Apffel MARINE...Apffel

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