Area Forecast Discussion
Issued by NWS Burlington, VT

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBTV 171944 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 344 PM EDT Mon Oct 17 2016 .SYNOPSIS... Skies will range from partly sunny to mostly cloudy across the north country today. Clouds will be on the increase late this afternoon and tonight as a strong warm front lifts northeast across the North Country, bringing showers and a possible rumble of thunder. Well above normal temperatures and breezy conditions for Tuesday precede a cold frontal passage on Tuesday night. Above normal temperatures continue into midweek, with the weather pattern turning more unsettled late this week. && .NEAR TERM /THROUGH TUESDAY/... As of 146 PM EDT Monday...The cloud cover has slowly thinned out across the northern Champlain Valley and northern Vermont. However as mentioned with the previous update the clear skies will quickly give way to increasing cloud cover building from the southwest as a warm front advances towards the North Country. Otherwise the forecast is in good shape with no changes needed. Previous discussion from 638 AM EDT Monday...Issued an early update for two purposes: to add patchy fog in the forecast into mid-morning and to get temperatures better in line. METARs and reports from spotters indicate that fog has been dense in isolated spots this morning. While the trend is for improvement, it will likely continue to impact the morning commute before lifting as the cold front - and its associated increase in north winds and dry air advection - begin to lift out areas of mist or fog into the mid- morning hours. For more specific details, see the Special Weather Statement issued earlier. Other than that, the other main update was to adjust the hourly temperatures generally up a few degrees into the next few hours. The cold front still is slowly making its way out of Quebec and as such, houry temperatures have generally been several degrees warmer than conveyed in the grids. So I made some changes to try to get those better in line. Otherwise, the forecast for the rest of the day still looks on track. Previous near-term discussion issued at 400 AM Monday follows... We start the first day of the workweek off cloudy across southern Vermont. However much of the rest of the North Country is stuck in areas of radiational fog/mist due to skies having cleared, relatively high dewpoints for late October and wet ground from yesterday`s rainfall. Still awaiting the actual cold front which is located along the US/Canada border at this point. The fog/mist should be temporary as once this boundary slips southward across our area, north winds and dry air advection should lift the fog. However, it may restrict visibilities into the morning commute. Morning commuters should drive with a little extra caution in areas of fog this morning. Front will continue to sag southward through today, while areas to the south see prevailing overcast begin to erode by the afternoon hours. So, expect to see variable cloud cover today, greatest to the south with more sun to the north. Highs today are pretty tough to pin down given the cold advection to the north and the cloud cover to the south. I`ve shown temperatures being pretty uniform, give or take a couple degrees, as areas that receive more sunshine also are cooler this morning at 925 mb than the cloudier areas in southern Vermont. I`ve shown highs ranging from the upper 50s across northern Vermont to the lower 60s in southern Vermont and the St. Lawrence Valley. For tonight: Clouds should increase from southwest to northeast from rather strong isentropic ascent owing to an approaching warm front tied to a low pressure that will pass well to our northwest. A number of forecast models both global and higher-resolution CAMs generally agree on precipitation timing between about 00z through 10z and primarily across our northern and western counties. Strongest warm thermal advection between 925-700 mb takes place during that period of time, driven by a low-level jet of 35-45 kts as progged by the BTV-4km WRF. There are also indications from the 00z NAM and BTV-4km of elevated instability (Showalter values as low as -2) as the front lifts northeast. So, PoPs increase into the the high-Likely range across the northern half of the CWA, with lower slight/low Chance range across southern VT further removed from the stronger lift. While rain is the predominant weather, I`ve included isolated thunder as well from the St. Lawrence Valley, northern Champlain Valley of NY/VT and northern/central VT given the negative showalter indices. It should be more of an exception than the rule, however. Rainfall amounts range from a few hundreths in southern Vermont up to a third of an inch along the northern border counties. Temperatures tonight are also challenging as the potential for cooler temps in shallow northeast drainage flow in the St. Lawrence Valley amidst strong warm advection aloft and overcast. Given the clouds, temps should be slow to cool and likely rise after midnight. Lows range from the low to mid 40s across the Northeast Kingdom and northern St. Lawrence Valley, to the middle 50s in southern Vermont. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
As of 344 PM EDT Monday...A weakening cold front will move through the region Tuesday night. Models showing QPF falling about as the front moves through the region Tuesday night. Thus, have stayed with just chance pops for Tuesday night. A weak ridge of high pressure will build east from the Great Lakes on Wednesday and will remain over the region through Wednesday night. Models showing some differences for late Wednesday night, with the NAM and ECMWF trying to bring some showers into the region after 06Z Thursday, while the GFS model is dry. Will stick with the dry GFS and keep a dry forecast for Wednesday night, with just increasing cloud cover late Wednesday night.
-- End Changed Discussion --
-- Changed Discussion --
As of 344 PM EDT Monday...ECMWF and GFS models showing some timing differences on Thursday with the ECMWF faster than the GFS in bringing rain into the region on Thursday. Models show a digging upper trough over the Mississippi valley which will transport plenty of moisture northeast into the region from the Ohio valley and the lower Mississippi valley on Thursday and Friday. The cold front associated with this will be slow to move eastward, as both the ECMWF and GFS models showing a hybrid subtropical low over the western Atlantic that will drift slowly northward Thursday and Friday. This low will slow the eastward progression of the front on Thursday and Friday. Have gone with likely pops for rain on Thursday and Friday. Models showing some timing differences on Saturday with the ECMWF much more progressive than the GFS with less QPF on Saturday, while the GFS model is slower and suggesting a wetter day and more QPF across the region on Saturday. Have stuck with the superblend pops from Saturday through Monday, given the model timing differences. Model guidance showing colder air aloft will move into the region Saturday night and Sunday, as an upper trough moves through the region. The higher summits of the Adirondacks and Green Mountains will likely see some snow showers Saturday night and Sunday.
-- End Changed Discussion --
&& .AVIATION /19Z Monday THROUGH Saturday/... Through 18Z Tuesday...VFR expected to trend towards MVFR as a warm front moves into the area. The mostly clear skies this afternoon will give way to an MVFR cloud deck as clouds advance into the North Country this afternoon. Showers will begin in earnest over northern New York between 22-00z however confidence in measurable precip is limited to just MSS with this update so elsewhere I mentioned the precip chances at VCSH. Upstream observations are indicating thunder is possible through the early evening and overnight hours but have not chosen to include in the TAF for MSS/SLK with this update. A strong low level jet 30-40kts will develop overnight over the Saint Lawrence Valley and with northeasterly drainage flow expect low level wind shear to be prominent at MSS from 08-14Z. Expect veering winds with the warm front gradually trending southeast 6-10 kts overnight and early morning. By mid morning tomorrow the low level jet will have moved over most of the North Country and winds across the Saint Lawrence and Champlain Valleys will become very gusty. Expect southerly wind gusts of 20-30kts developing at SLK/MSS/BTV between 13-16z with sustain winds of 15-20kts. Outlook 18Z Tuesday through Saturday... 18z Tuesday - 00z Wednesday: Early MVFR improves to VFR. Gusty south/southwest winds possible at MSS and BTV. 00z Wednesday - 12z Wednesday: VFR deteriorates to MVFR with showers along a cold front. 12z Wednesday - 00z Thursday: VFR under weak high pressure. 00z Thursday through Friday: Trending MVFR by 00z Thursday with MVFR to IFR at times through parts of Friday as steady rain advances northeastward. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Loconto NEAR TERM...Deal/Loconto SHORT TERM...WGH LONG TERM...WGH AVIATION...Deal/Loconto is the U.S. government's official web portal to all federal, state and local government web resources and services.