Area Forecast Discussion
Issued by NWS Burlington, VT

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364 FXUS61 KBTV 210559 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 159 AM EDT Thu Jul 21 2016 .SYNOPSIS... Ridge of surface high pressure will remain over the North Country through Thursday, providing the region with warm, sunny, and dry weather. Periods of showers and thunderstorms are expected Thursday night through Saturday as a frontal system moves slowly through the region. Some of the storms will have the potential to become strong or severe. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 151 AM EDT Thursday...no significant changes. Temps getting close to dew points in eastern VT which a few hours of valley fog are likely until about 8 a.m. Low temps mainly in the 50s with a few upper 40s in the normal cool spots while near Lake Champlain it will be Large ridge of surface high pressure will remain over the region right through Thursday with dry weather. Some high level cirrus clouds are possible from time to time with NW flow aloft from thunderstorms up near James Bay early this morning. Highs today will be warmer than normal with ample sunshine and warming aloft as 850 temps rise to 16 to 18C. So expecting highs 85 to 90. Winds will become south to southwest and some gusts to 20 knots in the St. Lawrence Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... As of 320 PM EDT Wednesday...An active period with several rounds of strong to severe storms possible. Thu Ngt/Early Fri Morning: A surface front in Ontario/Northern Great Lakes will be slowly approaching. Deep low-level layered moisture with with PWATS >1.5 inches advecting ahead of front...instability aloft with increasing presence of elevated mixed layer...a shortwave trough and exit region of 300mb jet approaching should have mesoscale convective complex in northern Great Lakes/Ontario moving into FA during late Thursday night/early Friday morning. Friday: As advertised...an Interesting day. SPC Day 3 (issued earlier today) is uncommon across FA. At times during the past few days models suggested that various ingredients didn`t quite come together all at the same time especially an elevated mixed layer. However...latest guidance is showing potential elevated mixed layer being present thus helps support the other parameters that have already been discussed in previous discussions. Surface instability (temperatures well into the 80s, resulting in CAPE values pushing 2000 J/kg. there still remains some questions on the low-level instability due to previous convection or debris clouds stabilizing atmosphere but feel enough dry air aloft and breaks will allow for substantial recoup of llvl instability. A shortwave skip through at some point during the day. Deep WNW shear of 35-45kts along with model soundings also indicate high equilibrium levels and semi-low wet bulb zero (10-11k ft) levels which suggest a wind and hail threat. Timing...After some recoup time from early morning activity...llvl destabilization and upper level shortwave activity in late morning/ aftn for some activity and perhaps enough drying afterwards for more late aftn/evening with surface front and another shortwave. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 320 PM EDT Wednesday...Some residual influence from departing trough on sat will yield a chance of showers...esp vt with decreasing west to east and temperatures still seasonable or above by a few degrees. Some shortwave ridging sat ngt/sun before approach of another northern stream shortwave mon. Max T on Sunday a few degrees milder than sat with more sun. Some showers move into late sunday night/early monday morning but the main focus will be on Monday. Very similar Monday to Friday`s set-up with approach of strong shortwave...strong wind dynamics...a bit more amplified and stronger surface cold front with decent cold air advection and falling heights associated with it. Strong to severe storms possible again and already some mention in SPC Day 4-8 discussion. Some differences with ECMWF/GFS about Tue/Wed forecast with ECMWF more amplified thus a bit more wet on Tues. Similar to Sat...best chance across VT..esp NE Mtns and drying trend into Wed. Temperatures near seasonable with lower humidity. && .AVIATION /06Z Thursday THROUGH Monday/... Through 06z Friday...VFR with mainly clear skies or wisps of cirrus clouds except LIFR vis in FG at KMPV from 09-12Z this morning. Marginal confidence in the FG/BR forecast as it`s been dry for a couple days and crossover temps in the mid to upper 40s and we will just touch that. Clouds will gradually thicken tonight with cirrus streaming in from the NW and may see some mid clouds arriving at KMSS before 06Z. Have showers in the vicinity at that time and there is also a low chance of thunderstorm by that time also moving SE from Canada. Light/calm winds will become light south to southwest today. KMSS could see some SW gusts to 20 knots during afternoon in tighter pressure gradient and channeling up the St. Lawrence Valley. Expecting winds to continue tonight as gradient strengthens everywhere. Outlook 06z Friday through Monday... Thu night-Sat...VFR, with scattered MVFR in showers and thunderstorms. Sun...Mainly VFR under weak high pressure. Mon...Scattered MVFR in showers and thunderstorms. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Sisson SHORT TERM...SLW LONG TERM...SLW AVIATION...Sisson

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