Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 190013 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 813 PM EDT Thu Oct 18 2018 .SYNOPSIS... Surface high pressure will move from the Ohio Valley east across Pennsylvania and off the Mid Atlantic coast by Friday. This will allow a brief respite from the recent cool weather. However, another shot of cold air will move in by Saturday along with more showers. This will be followed by more lake effect rain and snow showers southeast of the lakes Saturday night and early Sunday. && .NEAR TERM /THROUGH FRIDAY/... Lake effect cloud coverage over Western and North Central NY this evening will slowly erode through the evening and overnight hours. Though areas downwind of the lakes will continue to experience some continued cloud cover through the overnight into Friday. Current temperatures in the mid 30s over the higher terrain to the mid 40s closer to the lakes will cool some through the early overnight before warming begins from west to east with warm air advection. An expansive area of high pressure currently over the Ohio Valley will shift east to the Mid-Atlantic coast by late Friday morning. Lake effect cloud cover should continue to decrease in coverage tonight as increasing subsidence over the area will help lower equilibrium levels over and downwind of the lakes. Increasing 850Ts through the night tonight and warm air advection will also help with lowering these heights. Friday will start off with mostly sunny skies across much of the area and warmer temperatures compared to what has been experienced the past few days. With a southwesterly flow, temperatures across the area should warm to the upper 50s to around 60 across Western and North Central NY. The area will be on the northern fringe of an area of high pressure that will shift off to the east. A deamplifying mid and upper level ridge will shift east and give way to increasing cloud coverage Friday afternoon into Friday night. Cloud coverage will increase in advance of the next cold front that will move through the area on Saturday morning. This approaching cold front is associated with an area of low pressure that will move across Northern Ontario and James Bay on Friday. As this area of low pressure moves across Northern Ontario it will deepen and result in a stronger pressure gradient between itself and the high pressure shifting toward and off the Mid-Atlantic coast on Friday. With this increasing pressure gradient the area will experience increasing southwest winds for Friday into Friday night. Winds on Friday will range from 15 to 25 MPH with gusts to around 35 MPH, especially near the lake shores. With increasing vorticity advection this area of low pressure is expected to continue to strengthen as we get into the weekend. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... Rain shower chances will increase Friday night and Saturday as a cold front and associated mid level shortwave cross the area. Precipitation should come in two waves, first with the cold front late Friday night and into Saturday and then with the shortwave late in the day Saturday. Although there will be measurable precipitation at most locations, amounts should generally be light on the order of a quarter inch or less. It will be warm enough for all rain showers through Saturday afternoon. Expect high temperatures in the 50s early in the day with falling temperatures behind the front. It will also be breezy both ahead of and behind the front, with gusts of 30 to 40 mph. An amplified upper-level trough will dig across the bulk of the eastern U.S. Saturday night into Sunday behind the cold front and will aid in bringing below normal temperatures as 850 mb reach -8C by Sunday morning. Cold air streaming across the warmer Great Lakes waters will bring support widespread northwest flow lake effect showers. Model soundings keep low level vertical temperatures profiles warm enough for mainly rain early Saturday night, before profiles cool sufficiently for a mix and then change over to snow, especially for higher elevations. This will perhaps lead to a minor accumulation in any steadier or more persistent snow showers. Lake effect showers will linger through Sunday afternoon before starting to taper back late in the day. High temperatures on Sunday will only be in the upper 30s to lower 40s. Sunday night winds at the surface will back in response to a shortwave tracking across the Northern Great Lakes. This will lift any lingering lake effect activity northward (primarily off Lake Ontario) Sunday night. && .LONG TERM /MONDAY THROUGH THURSDAY/... A shortwave and associated moisture diving across the Eastern Great Lakes Monday will bring some enhancement to the lake effect precipitation, mainly east of Lake Ontario where westerly flow over the longer lake axis will bring greater chances for lake development. P-Type will mainly be rain across lower elevations...but on the Tug Hill a change to snow is possible, especially early and late in the day. Northwest flow behind the clipper low Tuesday will again set the stage for lake effect off both Lakes. As lake induced equilibrium levels rise through the day bands of showers/snow showers will be possible to the south and southeast of the Lakes. High pressure will nose towards our region Wednesday, bringing drier air across the Eastern Great lakes Wednesday that will end lake effect precipitation. This area of high pressure will settle across the Eastern Great Lakes Thursday, and likely bring a seasonably comfortable day with sunshine and temperatures in the 50s. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... VFR conditions are expected through Friday with surface high slowly moving east across PA during this period. Lake effect clouds near 3000-5000` will move east this evening, but otherwise expect minimal CIGS. Increasing high clouds will move in late Friday. Outlook... Friday Night...MVFR to VFR with showers. Saturday...MVFR to VFR with rain showers likely. Sunday...Mainly VFR but MVFR/IFR in lake effect rain and snow showers southeast of Lakes Erie and Ontario. Monday and Tuesday...VFR a chance of rain showers. && .MARINE... Winds will slowly back from WNW to W and then SW overnight and pickup again on Friday. Waters may drop a little below Small Craft Advisory conditions overnight, but will quickly ramp up again Friday with SW sustained winds in the 15-25kt range along with corresponding wind driven waves. A cold front will move through during the weekend with continued SCAs in a NW flow. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 6 PM EDT Friday for LEZ040-041. Small Craft Advisory until 6 PM EDT Friday for LOZ042>045. && $$ SYNOPSIS...Zaff NEAR TERM...SW SHORT TERM...Apffel LONG TERM...Thomas AVIATION...SW/Zaff MARINE...Zaff

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