Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 300240 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1040 PM EDT Thu Sep 29 2016 .SYNOPSIS... Fair and dry weather continues as high pressure over Quebec builds over the North Country through Friday. A closed upper low over the Ohio valley will linger there through Saturday. This low will move northward into the Great Lakes Saturday night into Sunday. Moisture from the closed upper low will bring increasing chances for rain showers to the North Country this weekend through Monday. && .NEAR TERM /UNTIL 6 PM FRIDAY EVENING/... As of 1040 PM EDT Thursday...Same as earlier...going forecast in real good shape with no real changes needed at this time other than a few tweaks to current temperatures and dew points. Clouds will generally be on the increase as the night wears on helping to limit the threat of fog. Previous Discussion... The North Country stays dry through Friday as a ridge of high pressure resides over Quebec keeping a cutoff low over the Ohio River Valley. Models continue to indicate 500mb heights increasing over the North Country with mid-high level clouds pushing northward over northern New York. Any rain showers associated with deeper moisture over western and central New York dissipate in the drier air over the St Lawrence Valley and Adirondacks as dewpoints generally in the low to mid 40s. The cutoff low meanders a little southward around the Ohio Valley, likely seeing a brief retreat in clouds overnight, but Friday afternoon will see deeper moisture spread northward into southern portions of the forecast area. With PWATs increasing to around 1 inch late in the day, lower clouds and possibly some late period showers begin to edge in from the south. Have included slight to low chance POPs near southern CWA border late Friday. Min temps tonight ranging from the mid 30s to upper 40s. Friday max temps will vary on cloud cover and cloud depth; with overall less sunshine, expect temperatures to be a few degrees cooler than today. && .SHORT TERM /6 PM FRIDAY EVENING THROUGH SATURDAY NIGHT/... As of 307 PM EDT Thursday... The North Country will still be under the influence of two main weather features during the short-term period: a lingering ridge of high pressure extending from Maine into the eastern half of the North Country, and the very slow-evolving upper low centered over the Ohio Valley and its associated northward feed of Atlantic moisture on its extreme eastern periphery. The main forecast challenges in this period will be on temperatures and identifying a period when PoPs may be more focused. Specific to the latter point, there remains little clarity on when there may be a more widespread period of rain as dry surface to 850 mb air should limit areal coverage. The 12z NAM is the most aggressive in showing QPF across our area on Friday into early Saturday. Feel this is more overdone as compared to the 09z SREF and the 12z GFS which is a lot more spotty. Through Friday night and early Saturday morning, PoPs are kept generally under Chance except for the extreme southern part of Vermont. Precipitation would also likely show a good component of southeasterly upslope with highest precip chances along the eastern spines of the Greens and Adirondacks and lower in the Champlain and St. Lawrence Valleys on the lee side. PoPs then begin to increase into the Chance/low Likely range for the second half of Saturday into Saturday night as mid-upper flow becomes more diffluent and might be just enough to spark a greater coverage of light showers. Temperature trends through the short-term period will be largely governed by mostly cloudy to overcast skies, with milder than normal lows but below-normal highs. Lows Friday night are generally coolest north (in the low 40s) to the mid/upper 40s south and in the valleys. Clouds and off-and-on light showers keeps highs Saturday a rather raw upper 50s to lower 60s east to a somewhat milder mid 60s for the St. Lawrence Valley. Little change to lows from daytime highs Saturday night in the 40s to mid 50s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 307 PM EDT Thursday... Upper low through the previous period undergoes a deamplifying trend into more of an open wave Sunday into Monday. Focus for highest PoPs would generally be Sunday into Monday but it`s worth pointing out that precipitation would be more showery in nature, meaning that not everyone would see rain and it would not amount to very much. Still some lingering slight chance PoPs on Tuesday but the weaker open wave then merges with a northern stream trough with a dry trend then offered for Tuesday night. A good stretch of dry weather looks to be the case with a broader diurnal range in temps for the mid-week period. Temperatures stay generally a few degrees above normal through the period, though expect to see more cooler nights Wednesday and Thursday with more clear skies. && .AVIATION /03Z Friday THROUGH Tuesday/... Through 00Z Saturday...Largely a persistence forecast over the next 24 hours. VFR conditions expected throughout with BKN- OVC100-150 across nrn NY, and SCT-BKN120-150 generally across the VT terminals. Can`t completely rule out a bit of 2-3SM BR at MPV during the pre-dawn hours, but it appears there will be just enough mid-level cloud cover (and impedance to radiative cooling) that patchy fog/mist formation is a low probability tonight. Otherwise, region is on nern fringe of cyclonic circulation associated with cutoff low over the Ohio Valley. This will generally keep a light easterly component to the winds across the North Country. Locally channeling effects in the St. Lawrence Valley will result in somewhat stronger winds at KMSS, generally NE 10-12kts overnight. Outlook 00Z Saturday through Tuesday... 00Z Sat though 12Z Saturday...Mid-level cloud cover continues in place, with increasing chances for light rain showers, especially s-central VT/RUT. 12z Sat - 12z Tue: Mix of VFR/MVFR in scattered rain showers, mainly from 00z Sun onward. 12z Tue onward: Generally VFR as rain showers depart eastward and surface high pressure builds into the North Country. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...KGM NEAR TERM...Evenson/KGM SHORT TERM...Loconto LONG TERM...Loconto AVIATION...Banacos/KGM

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