Area Forecast Discussion
Issued by NWS Burlington, VT

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094 FXUS61 KBTV 281429 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1029 AM EDT Fri Apr 28 2017 .SYNOPSIS...
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Drier air will filter in over the North Country today, leading to a decrease in clouds this afternoon. Temperatures will remain mild for Friday into Saturday...before a cold front produces another chance for showers and cooler temperatures Saturday afternoon into Sunday. A low pressure system will bring more chances for rain for the beginning of next week.
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&& .NEAR TERM /THROUGH SATURDAY/...
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As of 1027 AM EDT Friday...Forecast right on track and no changes with this update. Weak surface front has reached the Champlain Valley and dewpoints in northern New York have fallen into the upper 40s/low 50s, while BTV remains at 57. Some partial clearing in northern NY as well. Some gusty winds still possible across the Saint Lawrence Valley this afternoon as mixing increases...tapping into southwest winds of 20-30kts at 925mb. Max temperatures today will range from the 60s to mid 70s in the Champlain and CT valleys. Clouds will increase tonight as moisture aloft arrives on the persistent SW flow. This will be followed by a chance for rain showers early Saturday morning. Models do not agree much on placement of rain showers as more zonal flow keeps boundary moving and less defined. GFS and NAM lacking low level deformation with NAM taking a further south track of boundary and associated precip. Therefore kept only chance POPs. Expect cloudier skies to keep mins in the mid 40s to low 50s and max temperatures in the 60s to low 70s.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 330 AM EDT Friday...some differences have cropped up amongst the 00z suite of models with regard to the strength/depth of cold air that comes in from the north Saturday night behind the cold front, and then the resulting speed of warming later on Sunday as that front lifts back north as a warm front. In addition, differences exist with how much precip will fall (and exactly where) associated with overrunning with the warm front. In a nutshell, the NAM is 10-15 degrees colder than the GFS for Sunday`s temperatures. The NAM also has a batch of rain come across late Saturday night/early Sunday morning associated with the initial warm air advection push. Up to now, we`ve been advertising dry weather for that period. The GFS indicates increasing clouds, but is dry. Don`t think the NAM is right about the precip, but I think it`s on to something with colder temperatures on Sunday given it`s slightly better near surface vertical resolution and support from the ECMWF for cooler temperatures. With plenty of clouds and shallow low level northerly winds continuing to advect cool temperatures for at least half the day, it makes sense to go cooler. I dropped temperatures from the previous forecast about 6 to 8 degrees, but that might not be enough. Needless to say, not very high confidence. More consensus for areas of showers or just a steady rain to develop across northern areas Sunday night in association with the warm front setting up just north of the border along with strong isentropic lift thanks to strengthening low/mid level southwest winds. NAM and ECMWF are fairly robust on rainfall amounts along the border Sunday night, on the order of 1" by early Monday morning. GFS is much much less. At this point, thinking 0.30-0.45" along the Int`l border by 12z Monday. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 330 AM EDT Friday...00z suite of models is still in pretty good overall agreement with the scenario for early to mid week. Thus stuck with the model blend, which isn`t much different than what we had in the forecast. Going day by day... Monday: we should be in the warm sector, with the warm front just to our north. However close enough that we`ll have plenty of clouds and showers around. Some instability sneaks in across northern NY by the afternoon, so isolated t-storm is not out of the question. Pretty strong pressure gradient sets up, so breezy southerly winds (especially in the Champlain Valley) are expected. Monday night a surface trough will move through the region, accompanied by a band of showers. Decent moisture tap, so some briefly heavy downpours are possible. A bit of instability as well, so a rumble or two of thunder is not out of the question. Does move through quickly, so I don`t think we are looking at any significant hydro concerns, but still enough to monitor as we go through the weekend. Tuesday/Wednesday: Longwave trough settles across the region, with deep west/northwest flow and low level moisture about. Means plenty of clouds, scattered showers and a bit breezy at times. Cooler air filters in slowly later Tuesday and Wednesday, so Tuesday should be above normal for highs, but closer to or slightly below for Tuesday. Thursday: Weak ridging tries to develop, so lesser threat of any showers, but still expect a good amount of clouds. Unfortunately another developing storm system will be moving toward the region from the south later in the day. So even if we have any sunshine, clouds will win out by later in the day. Though beyond the period for the forecast, Friday could feature a good amount of rain and perhaps some wind. GFS and ECMWF begin to significantly diverge at that point, so way more questions than actual answers. It`s still a week away, so nothing to worry about right now. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... Through 12Z Saturday...VFR conditions will persist outside isolated and brief period of MVFR cigs at KMPV and KMSS through late this morning. Strong gusty winds channeling up the St Lawrence Valley will see SW gusts up to 30kts today. Other terminals could also see gusts of 15-25kts. Winds subside overnight to less than 10kts with increasing and lowering clouds, but remaining VFR. Showers expected to approach late in the period, ahead of a cold front. Outlook... Saturday: VFR. Breezy. Slight Chance SHRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Slight Chance SHRA. Sunday Night: MVFR. Chance SHRA. Monday: VFR/MVFR. Breezy. Likely SHRA. Monday Night: VFR/MVFR. Likely SHRA...TSRA. Tuesday: VFR. Breezy. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...KGM NEAR TERM...KGM/Hanson SHORT TERM...Nash LONG TERM...Nash AVIATION...KGM

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