653 FXUS61 KBUF 220238 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1038 PM EDT Thu Mar 21 2024 .SYNOPSIS... Light lake effect snow showers will dwindle as high pressure moves into the region tonight. The area of high pressure will push east, giving way to an approaching area of low pressure that will cause widespread snow and/or rain across the area through Saturday morning. Drier conditions will return for the second half of the weekend into early next week. && .NEAR TERM /UNTIL 6 PM FRIDAY EVENING/... Regional radar shows light lake effect snow showers east and southeast of Lake Erie and Lake Ontario late this evening. High pressure will continue to push into the region from the west, centering over the WNY area late tonight. As the area of high pressure tracks into the area, the response off of the lakes should weaken into the evening. High pressure over the area will promote clearing skies and mostly clam winds. This should set the stage for radiational cooling tonight. As a result, low temperatures will drop down to the single digits east of Lake Ontario and to the low to upper teens for areas south of Lake Ontario. Potential for snow showers will increase late Friday morning and into the afternoon as a sfc low and shortwave trough approach the area from the Ohio Valley through the day on Friday. A swath of showers will move into the area from the west as a trough/frontal boundary pushes into the region Friday afternoon. The main batch of precip should first move into the area north of I90, and then slowly fill in to the south and from the west as the sfc low approaches from the west. Precipitation should become steadier by the early to mid-afternoon for areas north of I90 in WNY. Steadier light snow should reach the North Country by around the evening commute, with the precipitation filling in south and east to most of the Niagara Frontier by then as well. Precip should mainly start out as snow and then slowly transition to rain for some areas as warm air advection increases ahead of the approaching sfc low. Still some uncertainty with the forecast models on track of sfc low and therefore the temperatures and resulting precip type. It looks like mainly south of I90 is the best potential for the changeover to rain, but guidance does bring a changeover to rain as far north as Lake Ontario for Monroe and Wayne counties at least briefly. More shower type precip to the south toward the NY/PA line will also start out as snow, but changeover to rain showers fairly quickly with the warmer temperatures pushing north into these areas earlier. Temperatures on Friday will vary across the area with low 30s to near 40 for areas south of Lake Ontario and in the mid 20s to near 30 east of Lake Ontario. These temperatures could end up being slightly cooler or warmer depending on the track of the incoming sfc low. Friday evening, precip will continue to fill in south and east as the sfc low tracks northeast across the Western Southern Tier to Central NY area and pulls a cold front through with it. A brief period of freezing rain may be possible for portions of the Niagara Frontier and Genesee Valley as warmer air briefly pushes north Friday evening into the night, but still a bit too much uncertainty on that. Behind the passing sfc low and cold front, any areas of rain should change back over to snow through the rest of the night. The sfc low and front should pass through the Western Southern Tier during the second half of the night on Friday night and through the North Country around daybreak on Saturday morning. Widespread synoptic snow should end for most of WNY by daybreak on Saturday and continue for areas southeast and east of Lake Ontario into the morning on Saturday. Temperatures Friday night will be in the low to mid 20s east of Lake Ontario and in the upper 20s to mid 30s south of Lake Ontario. The sfc low and front should track through the area fairly quickly, but a plume of moisture from the Pacific and the GOMEX wrapping up within this system and up along the East Coast ahead of a strengthening coastal low should make QPF amounts of around a third to one inch possible, especially with what looks like pretty strong forcing along the cold front as it passes. Snowfall totals through daybreak on Saturday should be in the range of 3 to 5 inches for the Niagara Frontier from around I90 northward and to the Rochester area; a coating to 1.5 inches for the rest of the area south of Lake Ontario. East of Lake Ontario where cooler temperatures are expected, around 4 to 8 inches of snowfall is expected, with some higher amounts possible over the Tug Hill. Additional light accumulations will be possible into the morning hours on Saturday east of Lake Ontario. Snow ratios during the event will generally be in the 8:1 to 12:1 range from south to north respectively. Snow amounts in mind, a Winter Storm Watch has been issued for Lewis, Jefferson and Oswego counties from Friday afternoon through early Saturday afternoon. && .SHORT TERM /6 PM FRIDAY EVENING THROUGH SUNDAY NIGHT/... Wave of surface low pressure that brought us widespread precipitation Friday night will continue shifting east of the forecast area Saturday. The northern stream jet associated with this system will begin to phase with the southern jet as it moves towards the coast, while upstream a stout mid-level ridge and surface high pressure builds over the Great Lakes. Snow with some rain mixing in across the lower terrain areas will taper off from west to east through the day as a result. Far western NY should be mainly dry by mid to late morning Saturday, with the North Country to follow later in the afternoon. Guidance is hinting at some additional light NNW flow upslope snow showers developing across the higher terrain areas east of Lake Erie and across the western Finger Lakes in the wake of the system and as the broad upper trough axis swings through. Have held onto Chc PoPs in these areas for a few additional hours Sat morning though BUFKIT soundings indicate significant drying above 900mb thereafter, so expecting little more than just extra clouds lingering through Saturday night onwards. Cold air advection with 850H temps sinking back to around -8C will continue to hold sfc temperatures 5-10 degrees below normal Saturday and Saturday night. This will translate to highs in the 30s and lows in the teens and low 20s respectively. Surface high pressure over Quebec will extend across the eastern Great Lakes Sunday and Sunday night, ensuring a stretch of quiet weather for the back half of the weekend. Not much airmass modification across the region Sunday so expecting temps to remain on the chilly side, though there should at least be more in the way of sunshine. As the axis of the surface ridge slides east Sunday night, winds will veer southeasterly as warm air advection aloft begins. This should allow sfc temps to moderate somewhat overnight, though lows will still be in the 20s with teens across the North Country. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... Strong upper level ridging across the eastern CONUS will shrink and move off the coast through early next week. Warm, dry air will begin to surge across the eastern Great Lakes with a stiff east- southeasterly breeze on the backside of this high pressure. This will cause the pattern to abruptly flip from the winter-like below normal pattern to above normal by Monday with highs well into the 50s south of the Lake Ontario shoreline, though still only 40s close to the shore and across the North Country. This will change by Tuesday as highs in the 50s become much more common across the entire forecast area. Next system with renewed chances for precipitation will take aim at the forecast area Tuesday night into Wednesday. A strong southern jet will transport a steady stream of GOMEX based moisture into the eastern Great Lakes, with surface cyclogenesis under the left-exit quadrant of the jet causing low pressure to climb from the Upper Midwest to Ontario Province across the Great Lakes. The track of this low suggests that winds could become quite breezy with this system though there remains a lot of uncertainty in the strength of the sfc low and associated LLJ. Otherwise, have undercut the NBM on PoPs as operational guidance continues to suggest Tuesday will remain mostly dry across our region, though confidence is high enough at this point for low-end lkly PoPs Tuesday night as large scale height falls and moisture advection will bring some widespread precip to the region. Temps well into the 40s should support an all rain forecast. The area should begin to dry out behind the system Wednesday night, though will hang onto low-end PoPs through Thursday as the primary trough axis will lag far behind to the west and may support some additional light QPF late next week. Temps are expected to cool to near normal behind the system as well, though remain much warmer than those seen this past week. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... VFR conditions will continue as light lake effect snow showers dwindle across the region late this evening. Surface high pressure will move across the region later tonight with calm and clear conditions. Light snow will move into the region Friday afternoon ahead of an area of low pressure. Rain will likely change to a wintry mix across the Southern Tier (KJHW) by Friday evening. Sub- VFR conditions will spread from west to east across the region with MVFR/IFR conditions likely Friday night. Outlook... Friday night through Saturday...IFR/MVFR with snow and rain. Rain/snow line close to KBUF/KIAG and KROC. LLWS possible near KJHW Friday night. Sunday through Tuesday...mainly VFR. && .MARINE... As surface high pressure builds towards the Lower Lakes tonight west to northwest winds and waves will subside through the night. These winds will shift to southeasterly Friday behind the surface high with a gentle breeze through much of the day. The winds become easterly and increase on Lake Ontario through Friday afternoon. The stronger east flow tomorrow and tomorrow night will build waves to small craft thresholds by Friday evening on the west end of Lake Ontario. Behind a storm system, winds will become northwesterly, with choppy waters becoming along the southern Lake Ontario shoreline later Friday night and Saturday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Winter Storm Watch from Friday afternoon through Saturday afternoon for NYZ006>008. MARINE...Small Craft Advisory until 2 AM EDT Friday for LOZ042. Small Craft Advisory until 5 AM EDT Friday for LOZ043>045. && $$ SYNOPSIS...SW NEAR TERM...HSK/SW SHORT TERM...PP LONG TERM...PP AVIATION...HSK MARINE...Thomas