Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 250754 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 354 AM EDT Sun Jun 25 2017 .SYNOPSIS... Scattered showers and thunderstorms are expected to develop later this morning and afternoon across the North Country. Gusty winds and small hail will be possible with any of the thunderstorms. The showers and storms will taper off tonight...but the potential for additional showers or storms will develop once again Monday afternoon. High temperatures will be right around seasonal normals today and a few degrees below normal on Monday. && .NEAR TERM /THROUGH MONDAY/...
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As of 157 AM EDT Sunday...Convection has come to an end early this morning and dry weather is expected through mid-morning. Deep layer shear has developed over the area and will persist through tonight. Instability is expected to develop as temperatures warm into the 70s and temperatures aloft cool a couple of degrees. This will create nearly dry adiabatic lapse rates in the 850-500 millibar layer...thus creating sufficient instability. Meanwhile dynamic support will be increasing over the area as a pronounced shortwave trough moves out of the eastern Great Lakes and into our area tonight. This will all be sufficient to create scattered showers and thunderstorms later this morning and afternoon across the area. Forecast soundings show low wet bulb zero values and drier air in the sub cloud layer. As a result...the potential for gusty winds and small hail will exist and will include in the forecast. For tonight...convection will decrease in areal coverage toward midnight as we lose instability and dynamic forcing shifts north and east of the area. Should be relatively dry during the overnight hours. Deep layer shear remains over the area on Monday and instability should develop during the afternoon hours. Temperatures will be a few degrees cooler than Sunday...thus instability will not be as favorable as Sunday. And there will be less of a forcing mechanism on Monday...thus looking at only a chance for showers or storms during the afternoon hours. Activity should not get organized enough to become strong...so no enhanced wording at this time.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
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As of 325 AM EDT Sunday...not much change in the overall forecast for this period - still more unsettled weather. The first half of Monday night will have a weak shortwave push across the region. Models all show some disorganized convection associated with the shortwave lifting southwest to northeast through 08z, so have aligned the PoPs with a blend of some of the hi-res models to show the evolution. One little feature to see if it comes to pass will be the potential for a little bit of lake effect showers come off Lake Ontario into the St Lawerence Valley area first thing Tuesday morning thanks to some cooler air aloft. A stronger upper trough approaches the area Tuesday. Although there will be plenty of clouds and temperatures on the cool side (upper 60s to lower 70s), the temperatures aloft (around 500mb) are rather cold (near -22C), so that should result in some instabilty to produce another round of afternoon/evening showers and perhaps a few t-storms. With the cold air aloft, wet bulb zero heights are quite low (7000-8000ft), so chance for some small hail in any deeper convection.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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As of 325 AM EDT Sunday...00z model suite still pointing toward a continued lengthy stretch of unsettled weather. Not that it will be cloudy and rainy continuously, rather we will see short dry periods of 12-18 hours followed by 12-18 hour long periods where scattered showers and t-storms will be around. At upper levels, we will be in a region of fast mainly zonal (west to east) flow with embedded shortwaves zipping through. It will be these shortwaves, combined with daytime heating, that will be the primary triggers for the convection. Given the uncertainty in timing these shortwaves, it`s best to take a bit more of a general approach to the forecast and use a model blend for day- to-day PoPs. At this point, I don`t see anything indicating any widespread severe weather through Friday. GFS and ECMWF continue to show a more significant upper trough develop to our west on Saturday, resulting in a deeper southerly flow which brings in some very moist air (precipitable water closes in on 2.0"). If this does come to pass, we could have some hydro related issues by then, especially if we have enough convective activity repeat across the same areas during the week. Just something to watch at this point. In general, temperatures will be slightly below normal through much of the week though trending closer to normal late week as the more southerly flow develops. Again, stuck with model blend for temperatures, and there is considerable error potential if we end up having much more sunshine than currently expected.
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&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/... Through 06Z Monday...Overall looking at VFR conditions through the period. There may be some low clouds and fog developing at KSLK between 08z and 12z...which would result in MVFR/IFR conditions. Otherwise main item of note will be potential for showers and thunderstorms between 16z and 01z. Some of the storms could produce gusty winds and small hail during this time period. The threat for showers and storms will end after 01z. Winds will generally be from the south and southwest through the period...but speeds will generally be 10 knots or loss. Outlook... Sunday Night: VFR. Chance SHRA...Slight Chance TSRA. Monday: VFR. Chance SHRA...Slight Chance TSRA. Monday Night: VFR. Chance SHRA. Tuesday: VFR. Chance SHRA. Tuesday Night: VFR. Slight Chance SHRA. Wednesday: VFR. Chance SHRA. Wednesday Night: VFR. Chance SHRA...Chance TSRA. Thursday: VFR. Chance SHRA...Chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson SHORT TERM...Nash LONG TERM...Nash AVIATION...Evenson

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