Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 251925 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 325 PM EDT Sun Jun 25 2017 .SYNOPSIS...
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Unsettled weather will continue across the region throughout the entire week with a daily threat of showers and a few thunderstorms. Some of the rainfall may trend heavy, especially later in the week as a more humid airmass moves into the area. Temperatures will remain close to seasonal early summer norms through the period.
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&& .NEAR TERM /THROUGH MONDAY NIGHT/...
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As of 325 PM EDT Sunday...Scattered showers and a few heavier thunderstorms continue across the area this afternoon in advance of of a vigorous shortwave to the immediate north of Lake Ontario. A few of the cells have produced small hail and gusty winds, which is not surprising given relatively low freezing levels near 9 kft and a near dry adiabatic sub-cloud layer. The shortwave feature will progress bodily east across the northern half of the area this evening when best threat of scattered showers/isolated storms occur, then exit east overnight with coverage waning. Lows a blend of available guidance showing values mainly in the 50s. More active weather still on tap for Monday as yet another strong shortwave drops into the central Great Lakes area. Low level surface trough boundary connecting today`s shortwave (then acoss the Canadian Maritimes) to the Great Lakes feature will serve as focus for low level convergence and additional showers/isolated thunderstorms by tomorrow afternoon. Best coverage to occur during peak heating hours of noon to 6 pm or so before covering slowly wanes into the evening and especially overnight hours. Low to mid level lapse rates are poorer than today and with cooler bondary layer temperatures per 925-850 mb progs updraft strength in covective cores will not be as robust. Thus no strong to severe storms are expected. Highs tomorrow mainly from the mid 60s to lower 70s with lows Monday night from 45 to 55.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... 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 Lawrence 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 instability 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. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... 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. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... Through 18Z Monday...Mainly VFR through the period with scattered showers and thunderstorms through early evening. Shortwave pushing across the area this evening driving scattered showers and thunderstorm activity across the area. No severe weather is expected though a few of the more robust storms could produce small hail, gusty winds into the 30-40 mph range, enhanced low level turbulence and brief MVFR/IFR conds. Coverage of storms to wane this evening and overnight with loss of surface heating and as shortwave exits east. Winds west to southwesterly 6 to 12 kts and occasionally gusty into the 15-20 kt range through sunset, abating to light overnight. After 12Z Monday VFR continues, but with an increasing threat of showers and thunderstorms once again as we approach the 18Z time frame. Given this will occur toward the very end of this forecast cycle have omitted specific mention at this point. Winds continue light west/southwesterly 5 to 10 kts. Outlook... Monday Night: VFR. Chance SHRA...Slight Chance TSRA. Tuesday: VFR. Chance SHRA...Slight Chance TSRA. Tuesday Night: VFR. Slight Chance SHRA...Slight Chance TSRA. Wednesday: VFR. Chance SHRA...Slight Chance TSRA. Wednesday Night: VFR. Slight Chance SHRA. Thursday: VFR/MVFR. Likely SHRA. Thursday Night: MVFR. Likely SHRA...Slight Chance TSRA. Friday: VFR/MVFR. Chance SHRA...Slight Chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG SHORT TERM...Nash LONG TERM...Nash AVIATION...JMG

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