316 FXUS61 KBUF 110821 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 421 AM EDT Thu Oct 11 2018 .SYNOPSIS... A cold front will move east across the area today with showers and a few scattered thunderstorms. Much cooler air will pour into the region tonight, with below normal temperatures setting in for an extended period of time from Friday through much of next week. There will be lake effect rain showers at times southeast of the lakes, especially Friday night and Saturday. && .NEAR TERM /THROUGH TONIGHT/... Radar imagery showing the first area of rain across the eastern Lake Ontario region early this morning. This will move east of our area before daybreak as the supporting low level jet continues eastward into eastern NY and western New England. An area of scattered showers over eastern Lake Erie will continue to overspread Western NY through daybreak. A deep mid level trough will move northeast across Ontario today, with an associated surface low moving from the eastern shores of Lake Superior this morning to the eastern shores of James Bay tonight. An associated cold front will move east across our area today, entering Western NY mid to late morning, and exiting the eastern Lake Ontario region by mid afternoon. Ahead of the cold front, a few scattered showers will continue to develop with little consequence. The latest high resolution convective allowing mesoscale model guidance suggests a likelihood of a broken line of showers and thunderstorms developing along the advancing cold front once it encounters growing diurnal instability by late morning or midday. The past few runs of the HRRR are most aggressive with this idea. Given the synoptic setup and high-res guidance, expect a line of showers to increase in coverage along the front in Western NY this morning, with scattered embedded thunderstorms developing around midday as the line moves into the Genesee Valley and encounters sufficient diurnal instability. This line will then move into Central NY and the eastern Lake Ontario region during the early to mid afternoon. PWAT values around 2 inches ahead of the front will support brief heavy downpours in any storms that develop. Linear forcing and moderate low/mid level wind fields may also support gusty winds in any heavier showers or storms that develop, primarily over the eastern half of the area where more robust convection is expected. An isolated severe storm with damaging winds cannot be ruled out. Following the cold frontal passage, showers will quickly end from west to east. Expect at least a few hours of partial clearing behind the cold front as a strong push of drying and subsidence moves into the eastern Great Lakes. Temperatures will stay in the 70s this morning ahead of the front, and may reach the upper 70s or close to 80 late this morning southeast of Lake Ontario. Following the cold frontal passage, temperatures will begin to pull back through the 70s and into the 60s later today as moderate cold advection begins. Tonight cooler air will pour into the eastern Great Lakes on WNW flow. Low level moisture will slowly deepen, allowing for lake effect clouds to become more widespread overnight. The shallow moisture will initially prevent any lake effect rain showers through the first half of tonight. By late tonight lake induced instability and moisture depth increase enough to support a few scattered rain showers southeast of the lakes, but conditions are by no means ideal for lake effect rain. Off Lake Erie, expected a few scattered showers to develop across the higher terrain of the western Southern Tier aided by upslope flow. Off Lake Ontario, expect scattered showers along the immediate south shore and extending to points southeast of Lake Ontario, aided by some upstream connection to Lake Huron. Rain amounts will be very light given the marginal setup. Temperatures will drop into the mid to upper 40s by late tonight on the lake plains, with lower 40s on the hills. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Our weather will turn noticeably colder with associated chances for rain showers Friday through Saturday. A sharp mid-level vort max will slide east from the Central Plains to the Mid-west and Great Lakes Friday progressively pivoting the longwave trough axis east across the Great Lakes and Ohio Valley to the Northeast states Friday night into Saturday. This will bring a shot of modified western Canadian air across the Great Lakes. 00z GFS/EC consensus drops 850mb temps over the eastern Great Lakes to -3C. This is cold enough to support lake effect rain showers with the 00z NAM BUFKIT profile over Lake Ontario showing lake induced equilibrium levels running around 6-7kft through Friday then rising and peaking around 15 kft Saturday morning before dropping back down to around 6kft Saturday night with surface high pressure ridging over the Great Lakes. Guidance does suggest synoptic moisture will be shallow through Friday before deepening Friday night and thinning back out through Saturday. Have made slight adjustments to the POPs based on latest RGEM and NAM wind forecasts. The thinner moisture will keep chance POPs southeast of the lakes Friday under 290-300 flow. Likely POPs are then featured southeast of both Lakes Erie and Ontario Friday night with better moisture and deeper convective plumes before leaving likely POPs only southeast of Lake Ontario Saturday as high pressure begins to ridge over western NY. The mid-level trough axis crossing our region Friday night and Saturday has allowed for widespread chance POPs for rain showers away from the lake effect showers. The remnants of Hurricane Michael will be shifting well off the Mid- Atlantic coast Friday which is of little interest to weather across upstate NY. Surface ridging with the center of high pressure passing to our south will support only some limited lingering lake effect shower east/southeast of Lake Ontario Saturday night. Temperatures will feel more like late October with highs running around 10F below normal. Look for low to mid 50s at best during the afternoon Friday and Saturday with overnight lows ranging from the mid 30s in the higher terrain to low 40s near the lakes. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Cool temperatures will persist into the middle of next week with several chances for rain showers. Brief mid-level ridging/zonal flow at 500mb is forecast over the eastern Great Lakes Sunday followed by a mid level wave and its attendant surface reflection passing by to our north across Central Ontario and Quebec Sunday night...with its trailing cold front passing through our region late Sunday night into Monday morning. Out ahead of the front...Sunday should be dry with a modest shot of warm air advection out ahead of the front also helping to push high temps back up into the mid 50s. Sunday night shower chances should at least increase somewhat as the front passes through our region...though the exact coverage of these still remain in question as the 00z EC keeps our region dry through most of the night. The medium range guidance continues to show differences in the speed of the cold front and trailing narrow surface ridging. The 00z GFS is about 12 hours faster than the EC. Have left chance range POPs with the run-to-run and model-to-model variance. This incoming surface ridging looks to potentially lead in another shot of colder air late Monday night or Tuesday which may triggers chances for some scattered showers with embedded nuisance-type lake effect rain showers becoming possible downwind of the lakes. Temperatures will fall back to below normal levels for both Monday and Tuesday...with highs both days only expected to range from the upper 40s across the higher terrain to the lower 50s across the lower elevations. After that it looks like a case of lather...rinse...and repeat for Tuesday night and Wednesday as another mid/upper level trough axis passes across the Great Lakes and Northeast...with its attendant surface low passing by to our north across Ontario/Quebec and pushing another cold front through our region. This next system should also be accompanied by a round of at least scattered showers as it passes through our area...with its attendant cooler temps aloft possibly also supporting some areas of lake enhancement. Otherwise temperatures will remain below normal...with highs on Wednesday again mainly in the upper 40s to lower 50s. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... A cold front will cross the region today. The first batch of rain east of Lake Ontario will exit before daybreak. The low level airmass is initially unsaturated with this, so expect mainly VFR CIGS and VSBY. Farther west, areas of MVFR CIGS at lower elevations and IFR for higher terrain will expand through the early morning hours as the low levels saturate. A few scattered showers will overspread Western NY early this morning as the cold front approaches, and these showers will likely increase in coverage as the cold front crosses Western NY through the mid to late morning. The cold front will encounter increasing instability to the southeast and east of Lake Ontario during the midday and early afternoon hours, with a better chance of a line of showers and thunderstorms developing. Some of these storms may contain gusty winds briefly. Behind the cold front expect MVFR CIGS to linger for an hour or two, and then scatter out to VFR as much drier air sweeps into the region. Low level moisture will move back into the area this evening as lake effect clouds begin to develop. This will produce areas of MVFR CIGS overnight. A few scattered lake effect rain showers will develop late tonight southeast of Lakes Erie and Ontario with spotty/brief MVFR VSBY. Outlook... Friday...Areas of MVFR southeast of the lakes in scattered lake effect rain showers, VFR elsewhere. Friday night and Saturday...Lake effect rain showers and MVFR/IFR southeast of the lakes, otherwise VFR. Sunday and Monday...VFR/MVFR with a chance of rain showers. && .MARINE... A strong cold front will move east across Lakes Erie and Ontario today. Winds will become westerly behind the cold front and quickly increase, producing solid Small Craft Advisory conditions on Lakes Erie and Ontario. Moderate to strong westerlies will then continue tonight through Friday night with an extended period of Small Craft Advisory conditions. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory from 8 AM this morning to 2 PM EDT Friday for LEZ040-041. Small Craft Advisory from 10 AM this morning to 8 PM EDT this evening for LEZ020. Small Craft Advisory from 2 PM this afternoon to 5 AM EDT Saturday for LOZ043>045. Small Craft Advisory from 11 AM this morning to 2 AM EDT Saturday for LOZ042. && $$ SYNOPSIS...Hitchcock NEAR TERM...Hitchcock SHORT TERM...Smith LONG TERM...JJR/Smith AVIATION...Hitchcock MARINE...Hitchcock