Area Forecast Discussion
Issued by NWS Buffalo, NY

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350 FXUS61 KBUF 301501 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1101 AM EDT TUE AUG 30 2016 .SYNOPSIS... An area of high pressure will cross the region this morning, settling over the mid-Atlantic coastline tonight. Expect fair weather with comfortable levels of humidity to continue through the day today. A cold front will then cross the region on Wednesday with some scattered showers and thunderstorms...to be followed by an area of high pressure that will spell fair weather into the holiday weekend. && .NEAR TERM /THROUGH TONIGHT/... A peek at satellite imagery this morning shows that early morning fog has cleared across the Southern Tier, with sunny skies prevailing across virtually all of the forecast area, thanks to a broad dome of surface high pressure transiting overhead the region. For today mostly sunny skies will prevail as this surface high slides to the coastline. A light southerly wind on the back side of this area of high pressure will bring warmth, and a touch bit more of humidity northward, with afternoon highs in the low to mid 80s. A few clouds will begin to increase, especially northward as this cold front upstream works its way eastward through the day. A stable southwest wind off Lake Ontario, and through the SLV, may be enough delay showers and thunderstorms with the upstream cold front until the evening hours. Tonight this cold front will drop across southern Canada and to near the Eastern Great Lakes Wednesday morning. Moisture pooling ahead of the front within a marginally unstable atmosphere may bring a few showers through the overnight, with activity spreading from Southern Canada and the SLV southward overnight. Towards the NYS/PA line the overnight period will likely remain dry...being to far away from the front. Lows overnight will be a bit warmer with the southerly flow, increased moisture and clouds. Overnight lows will range from the mid 50s across the Southern Tier to low to mid 60s farther northward. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... For Wednesday, chances of showers and storms will increase somewhat as large scale support increases as an upper trough drops across eastern Ontario. This should induce a stronger downstream frontogentic response across the area. Western and north central New York also should become more favorably positioned in right entrance region of an associated 60-80 knot upper jet streak. Not expecting severe weather at this time with better shear profiles post-frontal. Afternoon temperatures should average within a couple degrees of 80. The focus for precipitation shifts southeast of the area Wednesday night, but the big story will be period of much cooler and less humid conditions behind the associated cold front. It should be noted that while it will be chilly enough aloft to support instability over the lakes...the short fetch and limited environmental moisture will greatly reduce any lake response. On Thursday, a large area of Canadian high pressure will extend southward across the Upper Great Lakes to the Southern Plains. This will generate a relatively deep northerly flow of much cooler air over our forecast area with 850 mb temperatures forecast to drop to 8-10C. While this will keep instability in place over the Lower Great Lakes, the overall regime will be relatively dry. Will keep some clouds in place across the Finger Lakes to account for the continued northerly upslope flow, otherwise it will be a partly sunny and cool day with high temperatures generally within a few degrees of 70. It will become relatively cool for parts of our forecast area Thursday night as the center of the expansive surface high will make its way across the Upper Great Lakes. Favorable radiational cooling within a fresh Canadian airmass will allow the mercury to drop well into the 50s away from the lakes, with parts of the Southern Tier likely experiencing lows in the 40s. && .LONG TERM /FRIDAY THROUGH MONDAY/... While the start of this period will feature cool comfortable weather...it will be more noteworthy to point out the significant day to day warming trend that will carry us into next week. The ultimate factor leading to the return to above normal temperatures will be the development of a strong jet across the Northern Pacific. This jet will kick out persistent troughiness that will be in place over British Columbia...a trough that we have not seen in a couple months and at least partly responsible for the spell of cool weather at the onset of this period. In any case...the +120kt H25 jet will help to deamplify and broaden the west coast trough...which in turn will lead to substantial height rises downstream across the eastern half of the country. Meanwhile...expansive high pressure will guarantee rain free weather through the period. The details... On Friday...a progressive upper-level trough with high-latitude Canadian sourced air will pivot across New England. A dry...shallow cool airmass will build across the region in its wake while a sprawling surface high will move from the upper Great Lakes Friday morning to over the forecast area Friday night into Saturday morning. Despite 850 mb temperatures returning to around +10C Friday afternoon...the shallow cool airmass will keep a low-level inversion in place and thus high temperatures will remain in the lower 70s. We will see much more sunshine however on Friday though...as even drier air will advect across the region. Friday night will be the chillest period of the forecast package as optimal radiational (minus the fresh snowpack) will encourage our Canadian airmass to support mins in the low to mid 40s across the majority of the Southern Tier as well as in Lewis County. The mercury will flirt with the 40s elsewhere away from the lakes. Temperatures will then recover Saturday into Sunday as the sprawling high pressure system slides off the New England coast and allows the airmass to moderate with 850s back into the mid teens C. This will bring temperatures back into the upper 70s Saturday and low 80s Sunday and possibly mid 80s by Labor Day. With high pressure remaining in control this should remain a dry period with fair weather. Looking further down the road at the remainder of next week...the presence of a strong jet across the North Pacific should keep a low amplitude trough in place over the western conus. This will favor a downstream ridge over the eastern seaboard with a persistent southerly flow over the Lower Great Lakes. The strong zonal Pacific flow will also help to block any attempt by chilly Canadian air from making its way south of the border. The result will be a continuation of above normal temperatures through the week. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... Morning valley fog in the Southern Tier has cleared this morning, leaving widespread VFR conditions across the forecast area. These VFR conditions will prevail through today as high pressure slides across the region. A gentle south-southwest breeze with winds around 10-12 knots or less will prevail, though a few gusts around 15-18 knots will be possible off the lakes and across the KBUF and KART airfields. As this area of high pressure slides eastward today, a cold front will approach from the Upper Lakes region. This front will bring a few clouds later today, with the main increase in clouds the last 12 hours of the TAF cycle. Clouds should remain above 3k feet, though a few showers are possible along the front, especially in the vicinity and east of Lake Ontario. Will carry a VCSH for now for the KART TAF. Outlook... Wednesday...Mainly VFR with a chance of showers and thunderstorms. Thursday through Saturday...VFR. && .MARINE... An area of high pressure over the Eastern Great Lakes this morning is providing for light winds and near flat wave action on the lakes. This area of high pressure will slide by to our east today, and will allow for a light southerly wind to develop, though with speeds still well below small craft criteria. A cold front will cross the lakes Wednesday and Wednesday night and this will kick up the winds and waves a bit Wednesday night and into Thursday on the lakes...though conditions may remain just below small craft advisory criteria. A cool northerly wind will develop Thursday night and this will likely bring waves above SCA on the Eastern Great Lakes Thursday night and into Friday. After this, a broad area of high pressure will anchor over the Great Lakes region during the holiday weekend, bringing fine boating conditions. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...THOMAS NEAR TERM...THOMAS/WOOD SHORT TERM...TMA LONG TERM...RSH AVIATION...THOMAS/WOOD MARINE...THOMAS

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