Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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319 FXUS61 KBUF 081923 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 323 PM EDT Mon Jul 8 2024 .SYNOPSIS... An axis of high pressure stretching across the region this evening will slowly push east across New england overnight and Tuesday. While this will guarantee fair dry weather for the vast majority of the region...we will experience an increase in high and mid level clouds along with a shift back to more humid conditions. The remnants of Beryl will then move into the region late Tuesday night into Wednesday night when a soaking rainfall can be expected. Most areas can expect one to two inches of rain...although higher amounts will be possible across the Southern Tier and Eastern Lake Ontario region. && .NEAR TERM /THROUGH TUESDAY NIGHT/... Fair dry weather will persist throughout the region tonight...as an axis of high pressure will slowly exit across New England. High and mid level clouds will start to stream into the region on the backside of the high pressure...while a deepening southerly flow will allow more humid air to return. As a result...tonight will be a warmer night with mins generally in the mid 60s to as high as 70. Warm and increasingly humid conditions are then anticipated for Tuesday...as a weak cold front approaching from the north will basically dissolve over our region during the afternoon and evening. While fair weather will generally be the rule on Tuesday...we should have a fair amount of mid level (alto-cu) cloud cover. This will help to hold temps down a few degrees from where they would otherwise be...but despite this highs will range from 85 to 90. Given afternoon Td`s within a few degrees of 70...this could support apparent temps in the low to mid 90s for the usual corridor from IAG county to the Finger Lakes region. In regards to pcpn...slight and low chc pops will remain in place for mainly orographically initiated convection within a destabilizing synoptic environment. This would mainly be for the swath stretching from the western Southern Tier and Finger Lakes region to the southern slopes of the Tug (incl srn Lewis co). A tropically enhanced warm front extending eastward from the sfc remains of Beryl will approach our region Tuesday night. PWAT values that will already be in the vcnty of 1.75" Tuesday evening will surge to over 2" by daybreak...as tropical moisture associated with Beryl will pour across our forecast area from the Ohio valley. This deep feed of moisture will ride up across the aforementioned warm front and result in increasingly widespread showers during the course of the overnight. The rain could become heavy over the far western counties. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... ...Significant Rains from the Remnants of Beryl Likely Wednesday... Model guidance continues to come into better agreement on the track of the remnants of Beryl...with an eastward-translating mid level trough capturing and lifting these northeastward across the Ohio Valley and Lower Great Lakes Tuesday through Wednesday night. During this portion of the forecast period...the corresponding surface reflection looks to slowly deepen as it tracks from Indiana at the start of Wednesday to Lake Erie by Wednesday evening...then gradually fill as it drifts across the Lower Great Lakes Wednesday night...then across southern Ontario/Quebec Thursday. The remnants of Beryl will be accompanied by a pronounced swath of tropical moisture (precipitable water values of 2.0 to 2.5 inches) Wednesday and Wednesday night...with the latter supporting a risk for heavy rainfall. This rich moisture field will be initially lifted by a diffluent flow aloft and a northward-advancing warm front during the day Wednesday...followed by the system`s trailing cold front late Wednesday and Wednesday night. This will bring about a near certainty of periods of rain and some embedded thunderstorms Wednesday and Wednesday night...with the aforementioned frontal boundaries potentially also serving as foci for training storms and corridors of enhanced rainfall/resultant flooding risk. Current multimodel consensus supports the potential for a fairly widespread 1.5-2 inches of rain across the area...with the potential for more localized amounts of up to 3 inches within any corridors of training/enhanced rainfall that might develop. Given these expected totals...the relatively dry conditions of the past week...the 18 to 24-hour nature of the expected rainfall and current 6-hourly FFG values of 2 to 2.5 inches...still feel that we should be able to handle the bulk of this without issues...and as such will continue to hold off on the issuance of any Flood Watches for the time being. In addition to the rainfall...there is also a secondary concern for the potential for some stronger to potentially severe storms across our southernmost two tiers of counties later Wednesday afternoon into Wednesday evening. Some guidance (most notably the NAM and GFS) continues to suggest the potential for the system`s warm front to push across or even north of these areas Wednesday afternoon...which if realized could allow for the development of moderate amounts of instability. Given the presence of fairly strong deep-layer shear (0- 6 km bulk shear values of 40-50 knots) and veering wind profiles aloft...this could result in an environment possibly supportive of some multicell/supercell storms in the above areas...with damaging wind gusts being the primary severe weather threat. With this in mind have opted to add a mention of gusty winds to the forecast for the Southern Tier and interior of the Finger Lakes Wednesday afternoon and evening...which lines up well with the Marginal Risk area depicted in SPC`s Day 3 Convective Outlook. As for high temperatures Wednesday...these will be highly dependent upon the northward progress of the system`s warm front. To its north...a general ENE flow and more widespread/persistent pcpn will likely keep readings confined to the 70s...while to its south temps could easily surge well into the 80s. What is more certain are the humidity levels...as the burgeoning tropical airmass will likely send surface dewpoints surging into the oppressive lower to mid 70s in many areas. The widespread tropical rains will wind down from west to east during the course of Wednesday night and early Thursday as the system`s center and trailing cold front pass through our longitude. In their wake...there will be a lingering chance of much more scattered/weaker showers and a few more isolated storms on Thursday...before high pressure and drier air build in Thursday night and usher in a return to quieter and drier weather to close out this period. Otherwise...we can expect temperatures to average out a bit above normal...along with continued muggy conditions (though humidity levels will likely not be quite as oppressive as what we`ll see during Wednesday). && .LONG TERM /FRIDAY THROUGH MONDAY/... A trough over the central Great Lakes will track toward and across the forecast area through the first half of the weekend, weakening in the process. This will result in the potential for some showers across the area, especially the eastern portions of the area where increased Atlantic moisture is expected. For the period through the first half of the weekend, there is still plenty of model uncertainty among all the guidance, especially on the timing of the trough crossing the region. Some guidance brings the trough through quicker before moisture increases to the east, resulting in less shower potential. Some other guidance is slower with the trough, allowing the moisture to expand north and west, resulting in increased shower potential for north central NY. Shower potential will increase later Sunday into the new work week as a few shortwave troughs track across the area within a mainly zonal flow over the region. A cold front tracking southeast across the Great Lakes and into the forecast area Monday afternoon into Tuesday morning will increase the potential for showers during this timeframe. Again though, there is plenty of uncertainty among guidance for timing and shower coverage. Daytime temperatures during the long term period will be 5 to 10 degrees above normal for the entire area. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... Widespread fair/dry/VFR conditions will continue through early Tuesday afternoon...along with generally light winds. Scattered diurnal cumulus inland from the lakes this afternoon will fade with the loss of heating this evening...then high and mid clouds will be on a gradual increase from west to east overnight and Tuesday as mid and upper level moisture begins streaming across our area well out ahead of the remnants of Beryl. A few widely scattered diurnally- driven showers and storms will then become possible inland from the lakes Tuesday afternoon. Outlook... Wednesday...MVFR/IFR with tropical rains and a chance of thunderstorms. Thursday...MVFR/VFR with a chance of showers and a few isolated thunderstorms...with the showers possibly a bit more numerous east of Lake Ontario. Friday...Mainly VFR with a low chance of showers and thunderstorms inland from the lakes. Saturday...Mainly VFR with a low chance of showers and thunderstorms well inland from the lakes. && .MARINE... Light to gentle southeasterlies will become southerly overnight...while negligible wave action will persist. Gentle to occasionally moderate breezes and minimal waves on Tuesday will remain favorable for recreational boating. While conditions will stay below small craft advisory criteria Tuesday night...there will be an increasing risk for thunderstorms...especially on Lake Erie. Wednesday will be quite unsettled...as the remnants of Beryl will move through with times of heavy rain and possibly some gusty thunderstorms. The active weather will be accompanied by moderate to occasionally fresh northeasterlies. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...RSH NEAR TERM...RSH SHORT TERM...JJR LONG TERM...SW AVIATION...JJR MARINE...RSH