Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 261044 AFDBTV Area Forecast Discussion National Weather Service Burlington VT Issued by National Weather Service ALBANY NY 644 AM EDT Tue Sep 26 2017 .SYNOPSIS...
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Strong high pressure at the surface and aloft will continue to provide unseasonably warm, record setting temperatures for the region today through Wednesday. A cold front will move across northern New York and upstate Vermont Wednesday night with some isolated to scattered showers and isolated thunderstorms. A much cooler air mass will return, as more seasonable weather is expected behind this front from Thursday through the upcoming weekend.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY/...
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As of 644 AM EDT Tuesday...High pressure remains in control early this morning with mostly clear/partly cloudy skies and light to calm winds, as radiative mist and fog continues to slowly dissipate across the forecast area based on the GOES-16 fog product and the latest local observations. The fog has been locally dense in parts of the Champlain Valley, eastern VT near the CT Valley, portions of the St Lawrence Valley, and the favored climo locations in the northern Adirondacks such as Saranac Lake. The mist/fog should burn off between 7-10 am with the strong subsidence from the high and sunshine. Some cirrus has increased across the region well in advance of the cold front over s-central Quebec and the central and northern Great Lakes Region, as well as along the northern periphery of the mid and upper level ridge. The cirrus is thin and should not hold temps down too much. Another hot, record breaking day is expected with H850 temps still running a few standard deviations above normal according to the latest 00Z GEFS with actual H850 temps in the +18C to +19C range. High temps should be fairly similar to yesterday and maybe a degree or two cooler with a few-sct cumulus and the scattered cirrus around. Overall, mostly sunny conditions should be prevail with the cumulus mainly along the western spine of the central and northern Greens and over the Adirondacks. Highs will be in the upper 80s to lower 90s in the valleys especially the St Lawrence and Champlain Valleys and 70s to mid 80s over the elevated terrain. Sfc dewpts will still be in the 60s and it will be very humid outside. We will re-run the SPS with the heat indices in the lower 90s. They fall just short of the 2nd day with heat indices in the mid 90s for a possible advisory for n-cntrl VT. Please see the climo section below with the records that may be broken. Expecting a similar night to this morning with the sfc high weakening, and the mid level ridging flattening aloft. Some locally patchy dense fog may form in the valleys. We are expecting some high clouds to move in from the west ahead of the cold front over the eastern Great Lakes Region and southeast Canada towards daybreak. Lows will be in the mid 50s to mid 60s. It will be the last mild night.
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&& .SHORT TERM /6 AM WEDNESDAY THROUGH THURSDAY NIGHT/... As of 430 AM EDT TUESDAY...Maria drifts close to the Mid-Atlantic Coast then starts to make the turn to the east to northeast. Mid and upper level heights continue to fall over upstate NY into western New England during the day with low pressure moving into north-central Quebec and a cold front approaching the region. The increasing clouds should hold temps down a bit west of the Champlain Valley with upper 70s to mid 80s in the valley areas, and upper 60s to upper 70s over the higher terrain. Some upper 80s are possible in the Champlain Valley and near BTV /possibly some isolated 90F reading/, with generally 80-85F readings in the other valley locations, and 70s to around 80F over the mtns. Some record temps are possible again at several sites. There is modest convergence with the front and some small amounts of sfc based instability in the 250-750 J/kg range based on the latest GFS. We have placed slight to low chances of showers in the afternoon with a slight chc of thunderstorms. We will continue the previous BTV discussion highlighting heat hazards below: While these temps are considered sub advisory(<95 F), they are not to be taken lightly especially given the time of year. Based on the forecast and current records, its expected that records will fall at many sites by 2-5 degrees. Prolonged exposure outside combined with strenuous activity can lead to heat related injuries. Please take caution, stay hydrated and take frequent breaks during any outdoor activities. This will be the fourth consecutive day with 90+ degree heat indexes during the afternoon. Wednesday night into Thursday...Fairly good agreement with the latest deterministic guidance that the front will clear the forecast area between 06Z-12Z/THU. We did keep a few lingering showers over nrn-cntrl VT. Total rainfall from this front will likely be less than a tenth of an inch unless some convection occurs. Cold advection occurs in the wake of the front with H850 temps falling to +2C to +10C from the St Lawrence River Valley southeast across central VT. Lows will fall into the 40s to lower 50s. Cool and breezy conditions are expected on THU with sunshine mixing with clouds, as a sfc high noses in from the southeast Ontario. Highs will trend back to normal readings with mid 60s to around 70F in the valley areas, and 50s to lower 60s over the higher terrain. Thu night...A short-wave moving through the upper level trough over s-central Canada, the Great Lakes Region and into the Northeast will approach the forecast area. Mostly clear conditions early will give way to increasing clouds especially over northern NY. The short- wave and its associated cold front looks to impact portions of the local area on Fri. It should remain dry THU night with lows in the 30s to around 40F. There could be some patchy frost with lower to mid 30s in the northern Adirondacks. && .LONG TERM /FRIDAY THROUGH MONDAY/... Persistence was used predominately in the long term with the one change being the short-wave diving south and east of the region during the day. The limited low-level moisture will hold the chances of showers mainly in the slight chance category on Friday mainly west of the Champlain Valley. From the Champlain Valley eastward we have kept it dry. A slight chc of showers was kept in Fri night into Saturday with the mid and upper level trough passage, but overall this could end of dry again which has been the trend the past few weeks. A large ridge of high pressure builds in late Saturday into Monday with fair and dry weather with seasonable temps. Some patchy frost may be possible in the sheltered valleys within the higher terrain on the weekend. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/...
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High pressure at the surface and aloft will be over the region today into tonight. A cold front will approach from the west tomorrow. The locally dense fog and low stratus with IFR/LIFR/VLIFR conditions at KMSS, KSLK, and KMPV will gradually dissipate between 12Z-14Z with the strong subsidence with the ridge and abundant sunshine. The fog may linger the longest at KMPV. VFR conditions will prevail at KBTV, KRUT and KPBG this morning. VFR conditions will dominate from the late morning through the afternoon at all the TAF sites with some sct-bkn cirrus and a few- sct cumulus clouds. The clouds will thin towards sunset with some lingering scattered cirrus. Some locally dense fog will be possible once again tonight, especially after 06Z at KSLK, KMPV and possibly KMSS. Conditions may lower to LIFR/VLIFR at these locations. Some brief MVFR conditions maybe possible at KRUT after 08Z. The winds will be from the southeast to southwest at 6 kts or less during the late morning through the afternoon, and will be light to calm tonight. Outlook... Wednesday: VFR. Chance SHRA. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday-Saturday: VFR. Slight Chance SHRA.
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&& .CLIMATE... Record high temperatures and year recorded for the period through Wednesday Sep 27 Day Burlington Massena Montpelier 9/26 84 / 1934 82 / 1970 83 / 2007 9/27 83 / 1920 82 / 2003 80 / 2007 NEW RECORDS: Day Burlington Massena Montpelier St Johnsbury 9/23 86 9/24 91 88 85 89* (Tied) 9/25 92 91 88 91 && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Wasula/JMG NEAR TERM...Wasula SHORT TERM...Wasula LONG TERM...Wasula AVIATION...Wasula CLIMATE...WFO BTV

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