694 FXUS61 KBTV 152302 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 702 PM EDT Thu Aug 15 2019 .SYNOPSIS... High pressure centered across southern Quebec will translate eastward this evening, allowing a warm front and increasing moisture to stream northeastward from western New York and Pennsylvania. Periods of showers and a few embedded thunderstorms are expected after midnight tonight. With more humid air in place, additional chances for showers and a few thunderstorms exist for Friday and over the weekend. Valley high temperatures are generally expected in the 75 to 80 degree range for both Friday and Saturday, and then moderating well into the 80s for early next week. && .NEAR TERM /THROUGH FRIDAY/... As of 701 PM EDT Thursday...Going forecast in real good shape and no noticeable changes needed at this time. Still looking at showers and isolated storms to increase in areal coverage over the area later tonight and especially during the overnight hours. Only tweak was to slow down the cooling for tonight based on current temperatures and increasing cloud cover as the night wears on. Previous Discussion... Tranquil weather conditions through this evening as surface anticyclone across southern Quebec remains our controlling weather feature, along with low PBL dewpoints in the upper 40s to lower 50s. Conditions will begin to change overnight as developing warm front near the PA/NY line begins to shift newd as surface high departs to the north and east. Have noted scattered convective storms across the wrn half of PA this afternoon, and air mass is much more moist south of the frontal zone (sfc dewpoints in the mid-upper 60s and PW values 1.2 to 1.4" per RAP-based SPC mesoanalysis). Appears the North Country will get into better 900-800mb warm advection by midnight as 850mb sswly flow increases to around 20kts. After a mostly clear evening period, isentropic ascent leads to increasing clouds and developing showers across the northern Adirondacks by 05Z or so, and eventually overspreading central and northern VT during the pre-dawn hours Friday. The 12Z NAM forecast soundings indicate elevated CAPE values of 400-800 J/kg, and anticipate a few rumbles of thunder associated with embedded convective elements. Increased PoPs (80-90%) as well as rainfall amts...with generally 0.25-0.40" rainfall expected across the northern half of the forecast area. With best moisture and temperature advection focused north and west, lower PoPs (40-50%) and rainfall amounts for s-central VT tonight. Lastly, with developing light sely flow east of the Greens, appears we'll see some modified maritime air move into eastern VT toward daybreak. This should result in abundant low clouds continuing into Friday morning. Overnight lows generally in the upper 50s to lower 60s areawide. Best low-level WAA moves out early Friday morning, and should generally see showers ending/moving newd out of VT during the early morning hours. Will see two different air masses in place on Friday, with low-level sely flow maintaining low cloudiness longer across the eastern half of VT. From the Champlain Valley wwd, dewpoints should rise into the low-mid 60s in S-SSWLY airstream across the region. This will also lead to potential additional convective development Friday afternoon into Friday evening. Kept highest chances for thunderstorms across northern NY, with a slight chance of thunderstorms into the Champlain Valley. Deep-layer shear reaches 35-40kts Friday afternoon, but modest CAPE (500-1000 J/kg) will likely preclude any severe storms. A few stronger cells with gusty winds will be possible - mainly across nrn NY - mid to late afternoon on Friday. Appears air mass won't destabilize east of the Green Mtns with modified maritime air mass in place. Temperatures should reach the 75-80F range for afternoon highs, with moderate humidity levels. On Friday night, cyclonic mid-level wswly flow regime remains in place, and may see some additional scattered shower activity. Kept PoPs 30-40 percent across the region. Variable cloudiness and winds south 5-10 mph should keep temperatures a bit warmer as well, with overnight lows 60-65F. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 238 PM EDT Thursday...A dry pocket of air between systems will start Saturday morning before moisture will steadily increase ahead of another shortwave in the train of weak upper systems to lift across the North Country. Diurnally driven instability will likely develop as temperatures warm into the upper 70s to lower 80s with good synoptic driven support indicated by a veering wind profile with height, a semi-coupled jet streak, and a weakly negative-tilt trough. Destabilization should not be too strong though, given time of day for Northern New York, and then the slight easterly component to the low- level flow keeping a more maritime air mass in place for Vermont. Additionally, height falls will be minimal and model soundings indicate a warm layer should exist around 800-700 hPa. Thus, the threat for stronger storms will be minimal, but a few that break the unfavorable thermodynamic conditions will experience 0-6km shear of 35-40 knots, which could allow them to produce gusty winds. Convection will likely develop off terrain in the Adirondacks and propagate east into Vermont. Weak upper ridging builds in Saturday night, so precip chances should quickly end as instability decreases past sunset. Southerly flow and a pocket of very moist air advecting into the region will prevent most areas from falling below 60 for overnight lows. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 238 PM EDT Thursday...The North Country will still be aboard the shortwave express heading into next week, which means several weak systems will periodically bring increased chances for rain. We will also be looking at a substantial warm up as 925 hPa temps push upwards to 20-22 C. A few 90s will be possible on Monday. Forecast models are starting to come into something resembling agreement for next week, but consistency of finer details are a bit lacking. A shortwave passes through just about every day, but disagreements in variables like location, time of day, moisture content, and instability means the outcomes differ from model to model, but the overall picture looks similar. By Wednesday, a surface low should deepen in the vicinity of the North Country as a sharp upper trough/closed low digs southward into Quebec. Forecast models have not displayed great consistency with this feature yet. For now, a blended approach seems reasonable. A cooling trend can be expected after Wednesday at least. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Through 18z Friday...VFR conditions will persist through 03Z Friday with generally SKC-FEW050-060 across the region. Will see increasing mid-level clouds overnight, and eventually developing showers and a few embedded thunderstorms possible along a warm front, mainly 05-12Z Friday. Rain may be briefly moderate at times, especially at SLK/PBG/BTV/MPV. Anticipate periods of MVFR conditions. At MPV, may also see some lower marine stratus develop 08-13Z, and this could lead to intervals of IFR ceilings for a time early Friday morning. Should see ceilings lifting back toward VFR with rain showers diminishing in coverage during the mid-late morning hours. Light and variable winds will become light SELY overnight, and eventually south 5-10kts during the daylight hours on Friday. Outlook... Friday Night: VFR. Chance SHRA. Saturday: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance TSRA. Saturday Night: Mainly VFR, with local IFR possible. Chance SHRA. Sunday: Mainly VFR, with local IFR possible. Chance SHRA. Sunday Night: VFR. Chance SHRA. Monday: Mainly VFR, with local IFR possible. Chance SHRA, Chance TSRA. Monday Night: VFR. Chance SHRA, Slight chance TSRA. Tuesday: Mainly VFR, with local IFR possible. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos SHORT TERM...Haynes LONG TERM...Haynes AVIATION...Banacos