Area Forecast Discussion
Issued by NWS Burlington, VT

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747 FXUS61 KBTV 280623 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 223 AM EDT Thu Jul 28 2016 .SYNOPSIS... A frontal boundary just north of the international border early this morning will settle slowly southward across the North Country today. Meanwhile, an upper level disturbance across the central Great Lakes will move eastward, and result in scattered showers and thunderstorm activity near the frontal zone this afternoon and evening. High temperatures will generally reach the mid to upper 80s across the region today. A few showers are possible again on Friday, mainly across south- central Vermont as the low-level frontal zone continues to shift southward into southern New England. Cooler and drier air will filter in across northern sections, with highs in the lower 80s for Friday and upper 70s to lower 80s for Saturday, with lower humidity levels. && .NEAR TERM /THROUGH TONIGHT/... As of 138 AM EDT Thursday...Mild conditions prevail across the North Country early this morning with dewpoints in the low-mid 60s and temperatures ranging from the mid 60s most sections, to the lower 70s across the St. Lawrence and Champlain Valleys. Surface analysis shows a weak frontal boundary across srn Quebec into southeastern Ontario. Winds are nearly calm south of the boundary...and light W-NW north of the trough line with dewpoints mainly in the mid-upr 50s north of the front (an air mass that will be in place across the North Country for Friday). Some mid- upper level clouds are streaming ewd across the region this morning, mainly a function of convective debris from thunderstorms earlier today across the upr MS river valley and Great Lakes region. These mid-upr clouds are limiting radiational fog formation, but can`t rule out patchy development 8-11Z in the favored valleys of central/ern VT and within the valleys of the Northern Adirondack region. Remnant 500mb vort across the central Great Lakes will shear out ewd in W-E belt of strengthening 300-200mb flow approaching 90-100kt across Lake Ontario ewd into nrn NY/VT by 18Z this afternoon. That said, low-mid level flow will remain rather light in vcnty of sfc trough/frontal zone, as it sags swd into nrn NY/VT by early to mid afternoon. Insolational heating with filtered sunshine will yield 2-m temps in the low-mid 80s, and with mid 60s dewpoints in place, will contribute to SBCAPE values of 1000-1500 J/kg and PW values of 1.5 to 1.6" this aftn. Can`t rule out a stronger thunderstorm or two, but combination of mid-level lapse rates only around 6 C/km and very weak low-level flow should limit overall robustness and organization of widely scattered convective cells this afternoon. A few stronger cores could have some small hail or gusty winds, but generally below svr limits. PoPs peak around 60-70 Percent 18-20Z across central/nrn VT, and generally 40-50 percent across s-central sections. Into the early to late evening hours, will see convective coverage and intensity gradually diminish and generally focus across s-central VT as frontal zone sags south. Effective front may be marked by convective outflows pushing swd through the evening hours. Precipitation should be generally ending by 06z, with patchy fog possible in favored valleys 06-12z, especially in areas seeing daytime/evening thunderstorm activity and residual wet ground conditions. Low temperatures tonight generally in the low- mid 60s. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... As of 345 PM EDT Wednesday...Focus for the short term period will continue to be a weak frontal boundary as it slowly sags southward through the BTV CWA Thursday night, and stalls somewhere near/over the VT/NH/MA border on Friday. Convective activity wanes going into Thursday evening/night with the loss of instability due to decreasing insolational heating. Moving on into Friday, latest trends are for additional precipitation to blossom along the stalled frontal boundary as weak shortwave energy aloft shifts east from the Ohio River Valley into the Mid Atlantic states. This places the best chances for scattered showers and isolated thunderstorm across southern Vermont, while areas north will remain largely dry. Much like on Thursday, instability and shear are rather weak, so not expecting any strong storms, but a few more robust cells that do develop will have the potential to produce brief heavy rain as PWATs remain in the 1.5-1.75" range. Br Friday evening, any precipitation will begin to dissipate while shifting eastward as high pressure begins to build in from the Great Lakes Temps remain on the mild side of normal to begin the period on Thursday night, holding in the upper 50s to low 60s, but trend back towards mid/late summer standards with highs Friday in the upper 70s to low 80s, and lows Friday night ranging through the 50s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 345 PM EDT Wednesday...Overall idea for the long term period remains intact from previous forecast thinking with surface high pressure over the eastern Great Lakes on Saturday slowly shifting east to off the New England seaboard by early next week while aloft the flow remains out of the west/northwest. This offers mainly dry conditions through the period though latest guidance indicates a weak shortwave will bring a chance for a few showers to southern areas during the Sunday afternoon through Monday timeframe as it tracks from the Ohio River Valley to Cape Cod. Overall this energy is fairly weak, so will just offer some low chance PoPs across Rutland/Windsor counties while northward keep the forecast dry. Temps through the period begin very seasonal with highs over the weekend in the upper 70s to lower 80s, and lows in the 50s. As the high shifts east of the forecast area, increasing southerly flow will allow for a return of warmer and more humid conditions with temperatures rising a couple of degrees each day, reaching into the mid 80s to near 90 by Wednesday. && .AVIATION /06Z Thursday THROUGH Monday/... Through 12z Friday...Generally VFR with SCT-BKN070-100 much of the day. Scattered shower and thunderstorm activity will become most widespread 16-20Z, and then gradually diminish in coverage during the evening hours, while generally shifting swd into srn VT. Brief periods of MVFR/IFR possible in shower and thunderstorm activity with brief heavy downpours. Winds generally light S-SW, becoming light N-NW with weak frontal passage this afternoon...and remaining light north tonight. Patchy fog possible during the 06-12Z Friday period, especially at locations seeing shower/thunderstorm activity during the aftn/evening period with residual wet ground conditions. Outlook 12z Friday through Monday...Mainly VFR. Isold -SHRA possible s-central VT/KRUT during Friday afternoon. Chance for additional showers on Sunday, with isold -TSRA possible mainly across srn sections. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Banacos is the U.S. government's official web portal to all federal, state and local government web resources and services.