Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 231926 CCA AFDBTV Area Forecast Discussion...CORRECTED National Weather Service Burlington VT 326 PM EDT Tue May 23 2017 .SYNOPSIS... Weak high pressure across the northeastern United States brings tranquil weather conditions across the North Country through tonight. A weak upper level disturbance may bring isolated rain showers or a thunderstorm Wednesday afternoon, mainly across the higher terrain areas. Temperatures will continue to moderate Wednesday, with afternoon highs into the mid 70s in most sections. A more significant low pressure system evolving across the Ohio Valley and mid-Atlantic region will bring potential for a more widespread rainfall to the North Country Thursday afternoon through Friday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 138 PM EDT Tuesday...Forecast remains on track with warmer temperatures and partly sunny/filtered sunshine through the remainder of the daylight hrs. Winds have eased as surface high pressure builds across the forecast area. Winds generally 10 mph or less, and seeing evidence of a lake breeze with SE winds at PBG. The 500 mb ridge shifts east during the near term period as the low to the west deepens. Great Lakes 500 mb low gets kicked out and moves across southern Quebec in the northern stream today, bringing a few clouds along the border during the afternoon hours. Weak westerly flow and filtered sunshine will allow temperatures to warm into the upper 60s to low 70s in most locations. PoPs NIL. Ridging continues tonight, and low level moisture trapped under inversion, wet ground from recent rainfall and light winds will contribute to valley fog formation east of the Greens mtns and perhaps within the nrn Adirondack region. A 500 mb shortwave trough moves out of the base of the mean trough to our west, and up the Atlantic coast. A surface low spins up along the coast, and the main precip area with this feature will brush southern New England tonight, with no precip over Vermont/northern NY. Lows tonight in the 40s to low 50s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... As of 340 AM EDT Tuesday...For Wednesday the northeast is under the influence of a weakening surface ridge, while a weak mid level vort max lifts northeast. Combination of a little bit of lift from this feature and some differential heating over the mountains break out slight to low chance pops during the day in the northern Adirondacks and part of the Green Mountains. Warming trend continues into Wednesday with highs generally in the 70s, and lows Wednesday night in the 50s. Changes start on Thursday as the low to the west begins its move to the east. Surface and upper low remain further to south/southwest with diffluent flow aloft. 300 mb southerly jet noses into New York/Vermont during the day Thursday, while 850 mb easterly flow brings Atlantic moisture into the area. Pops begin to increase far western St. Lawrence County before sunrise, then continue to increase west to east during the day. Temperatures Thursday 5-10 degrees cooler than Wednesday with rain, clouds, and cool flow off the Atlantic. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 259 AM EDT Tuesday...New 00z guidance showing some disagreement with evolution of closed mid/upper level trof and associated surface low pres. GFS shows a track further east with limited qpf Thursday Night into Friday...while ECMWF shows a negatively tilted and vertically stacked system moving from the Mid Atlantic into Southern New England during this time period. Both agree on precip across our cwa...but exact details on placement of heaviest precip axis and associated pops still has some disagreement. Will continue to mention high likely to low cat pops for Thursday Night into Friday (65 to 80%)...with highest values central/eastern cwa. Expecting a similar type scenario for nose of easterly 925mb to 700mb jet is angled toward our eastern zones...helping to enhance moisture advection off the Atlantic. Speaking of Atlantic...expecting a chilly maritime airmass over our cwa during this time period and have cut superblend temps by 2 to 4 degrees...especially eastern/central cwa. The combination of cooler easterly flow...lots of clouds/precip...and progged 925mb temps btwn 6-8c support highs mid 50s to mid 60s. Warmest temps will be western dacks/SLV. For the weekend...weak 1013mb high pres builds into the North Country for Saturday...with still some embedded short wave energy and moisture with westerly flow aloft impacting our northern zones. The combination of lingering moisture...upslope flow...and weak energy aloft...cannot rule out a few midday showers...especially central/northern cwa on Saturday. 925mb to 850mb thermal profiles support highs very close to normal with mid 60s to mid 70s depending upon elevation and cloud coverage. For Sunday...still some uncertainty on placement of weak backdoor cold front or developing warm front lifting from southwest to northeast across our region. This weak convergence with embedded energy aloft may provide enough lift to support a few afternoon showers. Instability is limited and displaced to our not anticipating any thunder threat. Have continued to mention slight chance to chance pops...with threat increasing during the afternoon hours. In addition to precip uncertainty...still some question on max temps for Sunday...with a wide range in thermal profiles. We will stick close to superblend values...which is consistent with previous couple of forecasts. Highs mainly in the upper 60s to mid 70s...with 74 expected at BTV. Even more uncertainty as we head into early next week...associated with additional energy aloft and timing of another surface cold front. Latest ECMWF shows several boundaries lifting across our region with numerous embedded vorts in the flow aloft...along with ribbons of enhanced mid level moisture. Initially instability is limited...but increases some on Tuesday to support a chance of thunder. Will continue to mention chance pops with near normal we have plenty of time to work out the details in the upcoming days. Bottom line not expecting any long windows without the chance for rain and no significant heat in days 4 thru 7. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Through 18Z Wednesday...Generally VFR conditions with light winds expected throughout the TAF period. Weak sfc high across the mid-Atlantic coast will remain in control thru the overnight hrs, brining very light winds and just SCT-BKN080-120. May see enough breaks in the clouds to allow localized fog formation at SLK/MPV 06-11Z. Did include some BR mention at these locations only, with a chance of IFR conditions for a time during the pre- dawn hrs. Wednesday daylight hrs, surface low pressure develops east of NJ, with mid-level trough lifting nnewd across the North Country by early afternoon. Weak instability develops across the nrn mountains during the daylight hours Wednesday as well. As a result, will likely see building cumulus clouds by late morning/early aftn with isold -SHRA or -TSRA possible across the HIR TRRN toward 18Z Wednesday, and may see developing BKN030-045. Isold nature of convective activity does not warrant inclusion of VCSH/-SHRA attm, but best chance would likely be at SLK/MPV. Will continue to monitor. Outlook... Wednesday: Mainly VFR. SCHC -SHRA/-TSRA over the mtns. Wednesday Night: VFR. Slight Chance SHRA. Thursday: VFR. Breezy. Chance SHRA. Thursday Night: VFR/MVFR. Definite RA. Friday: MVFR. Definite RA. Friday Night: VFR. Slight Chance SHRA. Saturday: VFR. Slight Chance SHRA. && .EQUIPMENT... The WSR-88D at Burlington, VT (KCXX) will be unavailable from Tuesday May 23, 2017 through Friday May 26, 2017. During the outage, radar coverage is available from adjacent radar sites including Montague, Albany, and Buffalo, NY and Gray ME. A new signal processor will be installed, which replaces obsolete technology, improves processing speed and data quality, provides added functionality, and supports IT security. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos/Hanson SHORT TERM...Hanson LONG TERM...Taber AVIATION...Banacos EQUIPMENT...Team BTV is the U.S. government's official web portal to all federal, state and local government web resources and services.