555 FXUS61 KBTV 180243 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1043 PM EDT Fri Jul 17 2020 .SYNOPSIS... Clouds will taper off from west to east through the remainder of this afternoon with mostly clear skies expected as the sun sets this evening. Patchy fog is expected overnight tonight in response to the recent rainfall but will lift early in the morning on Saturday. A noticeable warming trend will be observed Saturday and again on Sunday as highs climb into the upper 80s to mid 90s on Sunday. Heat indices between 95 and 100 will be common Sunday afternoon. A cold front will move through the North Country Sunday night into Monday morning which will bring some rainfall to the region while allowing temperatures to return to near normal temperatures for much of next week. && .NEAR TERM /THROUGH SATURDAY NIGHT/... As of 1043 PM EDT Friday...As expected, areas of fog are beginning to develop in portions of Vermont due to wet surface conditions and little in the way of wind. Dense fog has been observed at the Caledonia County Airport, and satellite imagery does suggest areas of fog across much of the Northeast Kingdom as well as spreading southward along the Connecticut River Valley. The general idea of increasing coverage of this patchy fog is handled well by the current forecast. With this update, mainly adjusted winds, including lowering wind speeds to under 5 mph at most locations for the remainder of the nighttime hours. Otherwise, no other changes were needed at this time. Have a great night! Previous discussion...A weak warm frontal boundary/surface trough has made it to the Vermont and New York state line this afternoon. Skies are beginning to clear behind this weak boundary and we are also seeing dewpoints creeping into the upper 60s across northern New York. Much of Vermont remains socked in with cloud cover but that too will change as the boundary continues to work eastward. In the mean time, we will see some gusty winds continue into the late afternoon hours but by this evening winds should diminish to 10 knots or less as the pressure gradient relaxes and the low level flow shifts from the south to the southwest. A few showers will be possible across Vermont through the remainder of the afternoon hours but given the lack of heating today under the abundance cloud cover, the chances for thunderstorm activity look be very unlikely. As we head into the overnight hours, we will see skies continue to clear from west to east. Light winds accompanying these clearing skies should set the stage for some pretty widespread fog tonight from recent rainfall and dewpoints hovering in the lower to mid 60s. The best chances for fog formation will be across northern New York where they will be clear already heading into this evening and should reach their crossover temperatures by 03Z or so. In Vermont, the thinking is we will generally see some fog in the protected valleys east of the Green Mountains and along the Connecticut river but some patchy fog will be possible elsewhere. All fog is expected to lift by 9 AM with just a few high clouds transiting the region throughout the day. Temperatures will warm in response to the plentiful sunshine into the lower to upper 80s while dewpoints hover in the lower 60s. Increasing moisture will be in store during the overnight hours Saturday which will yield some warmer overnight lows with dewpoints creeping into the mid to possibly upper 60s as we approach daybreak on Sunday. && .SHORT TERM /SUNDAY THROUGH MONDAY/... As of 311 PM EDT Friday...Near record breaking temperatures in the lower to mid 90s expected on Sunday, along with dangerous heat index values approaching 100 degrees in the urban valley cities/towns. Little change has been made to expected temps or heat index values for Sunday with this forecast. NAM/GFS both indicate progged 925mb temps btwn 26-27C at 18z Sunday, which adding 10C gives us highs in the 96-97F degree range for CPV/BTV and lower CT River Valley, with 92-95F SLV/MSS and upper 80s to lower 90s many of the mountain towns. Soundings support good mixing, which may act to lower sfc dwpts into the upper 50s mtns to mid 60s on Sunday aftn, especially given the developing gradient. This generally supports heat index values in the mid/upper 90s most locations, except upper 80s to lower 90s mountain towns. Next item to watch will be convective potential late Sunday into Sunday night, as NAM/GFS and NAMNEST are showing potential for a broken line of stronger storms approaching the SLV by 00z. Multiple rounds of upstream convection is progged by CAMs this weekend and timing of these leftover convective vorts and interaction with llvl instability will be critical in determining the svr potential. Latest indications are an axis of 1200 to 1800 j/kg of cape will develop over northern NY, especially SLV with 0 to 6 km shear of 25 to 45 knots, supported by progged 850mb to 700mb jet of 40 to 45 knots. These parameters, along with approaching boundary/near record heat and weak embedded short wave wl have to be watched for svr potential late Sunday. Expect sfc boundary to swing acrs our cwa on Sunday Night into Monday morning with a broken line of showers with embedded rumbles of thunder, similar to this morning. Some localized heavier downpours are possible, given pws near 2.0 ahead of boundary. Temps with southerly winds hold in the mid 60s to l/m 70s overnight. Monday is cooler with any lingering showers ending by midday, as axis of higher pws shifts into southern New England, along with better instability. Highs generally in the lower 80s to near 90, warmest valleys, which is still 5 to 8 degrees above normal, but humidity values should decrease during the aftn hours. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 311 PM EDT Friday...Large scale synoptic pattern supports generally westerly flow aloft acrs our fa with embedded vorts every 12 to 18 hours. This will result in unsettled wx from time to time, but timing of energy and interaction with available moisture/instability becomes increasingly more difficult toward the middle of next week. Have chc pops (30 to 40%) in the fcst for late Tues thru Weds, with best moisture and sfc convergence from boundary located just to our south. Additional energy passes to our north on Thurs, along with weak sfc low pres and associated cold front. Have mention low chc pops for Thurs too, but areal coverage of precip looks minimal attm. High pres eventually builds into our fa by late week with much drier pws values in the 0.75 to 1.0 range and slightly cooler 925mb to 850mb thermal profiles. Progged 925mb temps are in the 19c-21c range for most of the week, supporting highs upper 70s to mid 80s, with lows in the mid 50s to mid 60s. These high and low temp values are 3 to 5 degrees above normal for this time of year. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Through 00Z Sunday...Clouds have eroded across much of the forecast area this evening, with a few lingering clouds over the higher terrain. Skies will remain mostly clear through the period, with few-sct clouds AOA 4000 ft developing after 15z Saturday. The main concern for tonight will be patchy dense fog, likely affecting the usual prone spots of KSLK and KMPV 06z-13z tonight. Ceilings will be below 500 ft and visibility below 1 mile during that time frame at those terminals. Winds will remain light, generally out of the south to southwest overnight, turning a bit more to the west Saturday and increasing to 7-10 kt. Outlook... Saturday Night: VFR. NO SIG WX. Sunday: VFR. NO SIG WX. Sunday Night: VFR. Chance SHRA, Chance TSRA. Monday: VFR. Chance SHRA, Slight chance TSRA. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Slight chance SHRA. Tuesday Night: VFR. Chance SHRA. Wednesday: VFR. Chance SHRA, Slight chance TSRA. && .CLIMATE... Near record to record high temperatures are possible on Sunday, July 19th. Here are the current records for July 19th: Max Temp Records Date KBTV KMPV SJBV1 KMSS KPBG KSLK 07-19 98|2013 92|1991 95|1991 93|1991 95|2013 92|1946 && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Clay NEAR TERM...Clay/Kutikoff SHORT TERM...Taber LONG TERM...Taber AVIATION...Clay/Hastings CLIMATE...Banacos