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Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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350 FXUS61 KBUF 182002 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 402 PM EDT Sun Aug 18 2024 .SYNOPSIS... A slow moving area of low pressure will continue to bring unsettled and eventually cooler weather through Monday, with several more rounds of showers and scattered thunderstorms. A few storms may contain localized heavy downpours and gusty winds, mainly through this evening from the Genesee Valley into Central NY and the eastern Lake Ontario region. Cool and drier weather will return Tuesday, with expansive high pressure then bringing dry weather and a day to day warming trend later in the week. && .NEAR TERM /THROUGH MONDAY/... Vertically stacked low pressure across the Eastern Great Lakes will gradually open up and shift into New England through Monday. Some breaks of sunshine late this afternoon has allowed for CAPEs to build to 1000 to 1500 J/Kg, with a generally weak flow aloft. The combination of instability and approaching trough has sparked some convection, with radar showing scattered to numerous showers early this afternoon. The exception is northeast of Lake Erie in the Buffalo area where the southwest flow is helping shadow the area. For the remainder of this afternoon and early evening there`s a risk of locally heavy rainfall. Consensus of latest mesoscale guidance suggests the greatest risk is east of Lake Ontario, but locally heavy downpours cannot be ruled out elsewhere due to the slow storm motion. Not much wind shear, but ample instability to support a few strong to severe storms with gusty winds from the Genesee River valley east. Here is where the most of limited wind shear is in place, with 700 mb winds about 30 knots. Tonight, the diurnally driven storms along the pre-frontal trough will continue to move east and weaken during the evening. Meanwhile, showers and scattered thunderstorms may also develop this evening as the cold front moves into Western NY and then across the area. An axis of deformation and frontogenesis on the cold side of the boundary will move from southern Ontario southeastward across the eastern Great Lakes overnight, supporting additional rounds of showers and possibly some embedded thunder. Low stratus will expand across the region overnight, and some of this may begin to intersect the higher terrain with areas of fog developing across higher terrain. Showers will linger Monday as the upper low slowly lifts out. Expect it to be a cloudy day, with the cool air aloft resulting in lake induced stratus which tends to linger. Hedge forecast on the cloudy and cool side of model blends given the synoptic set up. Monday will be much cooler with daytime highs only topping out in the lower to mid 60s. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... An upper level low will linger near our region this period, with its associated cool pool granting a fallish feel to our airmass. Highs Tuesday will be 10 to 15 degrees below normal, and Wednesday will fair just slightly warmer. Both days will feature a wealth of clouds. Synoptic showers will end early Monday night with deeper moisture shifting eastward, but a lobe of moisture rotating around this cool upper level low will lend to the formation of lake clouds and even a few showers/sprinkles Tuesday night and Wednesday south of Lake Ontario. A few upslope showers are possible east of Lake Ontario as well. Some clearing Wednesday night, but still enough moisture lingering in close proximity to this upper level low that we probably will not completely clear out. This will make for a tricky forecast for overnight lows both Tuesday night and Wednesday night as if we clear, or get enough of a clearing break temperatures could plummet down into the mid 40s inland/mid 50s closer to the lakes. However if clouds remain thick then the forecasted lows may end up too cold. && .LONG TERM /THURSDAY THROUGH SUNDAY/... The nearly vertically stacked low will begrudgingly drifts northeast across New England on Thursday. Lingering effects from this trough `may` induce a few shower, specifically focused across the North Country. Even so...this is low end chances (< 20%) with most locales seeing dry weather across the forecast area. After that...the stubborn trough exits and high pressure will `likely` take over the remainder of week. We will also see a day to day warming trend with overall spectacular weather. The next chance of any precipitation `may` potentially come over the weekend. That said...guidance is all over the board and have low confidence at this point to carry no more than slight chance PoPs (< 20%). Overall...a return to near normal temperatures will occur to a little above in some spots over the weekend. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... There`s a risk of showers and thunderstorms through 00Z, especially from KROC to KART which has a stronger flow ahead of the approaching closed low. Smaller risk at KBUF/KIAG until very late this afternoon into the evening due to lake shadowing, but showers and storms will move across these sites with the cold front around 00Z. Outside of showers and storms, mainly VFR flight conditions. Tonight a cold front will move across the area, and this will bring showers and much lower CIGS. Moderate to high confidence that this will drop CIGS to IFR at TAF sites tonight, with lower confidence in VSBY due to a risk of IFR or lower VSBY if clouds drop all the way to the surface, especially across the hilltops. Slowly improving conditions on Monday, with mainly IFR CIGS during the morning likely to lift to MVFR across lower terrain during the afternoon. Showers taper off from west to east during the afternoon. Outlook... Monday night...Areas of MVFR or lower. A chance of showers early, and lingering stratus. Tuesday...Improvement to VFR. Wednesday through Friday...VFR. River valley fog with local IFR across the Southern Tier each late night and early morning. && .MARINE... Issued small craft headlines for Lake Erie, due to the increase in southwest winds early this afternoon. Marginal, but winds should stay elevated 3 to 5 hours which will be just enough to build waves to 4 or 5 feet. A cold front will move southeast across the lower Great Lakes tonight. Winds will become north and increase behind the cold front late tonight and Monday. This will support a round of solid Small Craft Advisory conditions on Lake Ontario, with a chance of lower end Small Craft Advisory conditions on Lake Erie as well. The elevated north winds will continue through Monday night and Tuesday morning before gradually diminishing through midweek. There will also be a risk for waterspouts through Monday morning. There were multiple waterspouts on central Lake Erie this morning, so there`s a risk for more - especially on any boundaries which move across the Lake during this time. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ040- 041. && $$ SYNOPSIS...Apffel/Hitchcock NEAR TERM...Apffel/Hitchcock SHORT TERM...Thomas LONG TERM...AR AVIATION...Apffel MARINE...Apffel