Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 201741 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 141 PM EDT Sun May 20 2018 .SYNOPSIS... A cold front will push through the region on this morning, bringing showers to an end with clearing in the afternoon. High pressure quickly builds back in tonight and Monday with clear skies and warm temperatures. Other than a chance of showers Tuesday and Wednesday, most of the week ahead looks dry with temperatures on the warm side of normal. && .NEAR TERM /THROUGH MONDAY/... As of 953 AM EDT Sunday...No significant changes were needed with this update. The cold front continues to march across the region at this hour and now lies roughly from St Johnsbury to Waterbury to Newcomb. The showers associated with this front will also continue to move southeast through the morning hours and should exit the VT and northern NY by early afternoon. Satellite imagery shows clearing behind the front, so still anticipate sunshine returning this afternoon. The forecast has this pretty much all covered, so just made some minor tweaks to PoPs and sky cover to match the latest trends. Previous Discussion...An upper level trof and associated cold front will move through the region between 12 and 18z today. It will be preceded with showers most numerous over northern New York and northern VT. There is some very limited elevated instability and a few pulses of lightning detected in Ontario last hour but not enough to be concerned with. Some light to moderate rainfall has been seen on MRMS QPE in the showers, so another few tenths of an inch of precipitation is possible. Drier air will follow the frontal passage, bringing the showers to an end this morning and eventually allowing for some sunshine Sunday afternoon, perhaps a bit more stratocu in the mountains with developing NW flow. 925mb temps get up to around 12C at BTV which should bring high temps from the mid 60s in the higher elevations to lower 70s in the wider valleys. Clear skies will dominate Sunday night and Monday with high pressure building into the region. Low temps will range from the mid 30s in parts of the Adirondacks and extreme NEK to mid 40s near Lake Champlain. 925 temps on Monday get back up to 14-15C so it will be a little warmer with highs in the 70s, perhaps upper 70s in a few warm spots. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 340 AM EDT Sunday...no big changes from the 00z guidance, so the forecast remains fairly similar to the previous version. Quiet and dry weather Monday night. Still looking at a weak upper level trough to swing across the region during the day. As it approaches, it will pull clouds and moisture toward the region from the south. Latest model trends indicate that the thicker clouds will likely be across southern areas closer to the deepest moisture. Those clouds will also keep it a smidge cooler (upper 60s-lower 70s) in our southern areas. 00z NAM and BTV 4km WRF indicate that with the slightly more sunshine and warmer temperatures (mid-upper 70s) closer to the Canadian border, minimal surface based instability will develop and result in a few showers, perhaps an isolated t-storm, forming along the thermal gradient resulting from the more sun vs more clouds region. All in all, still appears most of the day will be dry for most folks. PoPs remain in the 30-40% range for mid afternoon thru early evening. Any showers dissipate by late Tuesday evening, resulting in clearing skies. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 340 AM EDT Sunday...00z guidance all seem to be pretty similar to one another, and in line with prior runs. Should be a fairly dry period, with likely summer-like conditions at the end of the week. A few notes concerning the forecast for each day follows... Wednesday: A mostly dry cool front should push southward during the day. Temperatures aloft south of the front will be quite warm (16-19C @ 925mb), so southern valley areas should make a run at 80F before the front arrives. Northern areas will still top out in the lower-mid 70s. Given pretty dry airmass in place prior to the front, don`t think there will be much in the way of shower activity. Have painted in generally 20-30% PoPs. Clear with seasonable temperatures Wednesday night. Thursday: 925mb temperatures will be down to 9-11C, but this will still result in near normal temperatures, with highs in the upper 60s to lower 70s. Ridging at lower levels will result in a sunny, dry day. Friday: Looks like upper level ridging builds to our west. Although flow aloft will still be northwest, there will be anomalously warm air in place across central Canada which will begin advecting into our region. The GFS, Canadian and ECMWF models are all consistent with 925mb temperatures in the 17-20C range. Typical rule of thumb for the warm season under sunny skies is to add 10C to those temperatures to get a rough estimate of high temperatures at lower elevations. That rule gives 27-30C, which equates to low/mid 80s. At this point, most statistical MOS guidance is still much lower than that, so I did go higher than those models, and trended about 5 degrees warmer than previous forecast. Painted in highs around 80F for valley regions and mid/upper 70s elsewhere. This may still end up being a conservative forecast if the recent model trends are correct. Saturday: Upper ridging moves nearer to the region, though low/mid level flow turns more southwest and starts to advect in moisture. A bit more uncertainty as to how warm it may get. 925mb temperatures range 14-17C per ECMWF, 19-22C per Canadian and 20-23C in the GFS, which cover a range supportive of potential highs in the upper 70s to upper 80s (which is all above normal). Again, statistical guidance is all closer to the low end of that temperature range. I did opt to go a few degrees above, but only to around the 80F mark. Also some indications that with some extra moisture around, we could get daytime heating showers or t-storm and that would act to keep things a bit "cooler". Have 20-30% PoPs for the shower potential. However, it`s still possible the temperature forecast is again conservative and it could feel much more like mid- summer to kick off the holiday weekend. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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Through 18Z MONDAY...MVFR will continue to prevail through about 21z this afternoon, mainly due to low ceilings, with occasional improvement to VFR. Clouds will dissipate as we head through the evening, with skies eventually clearing tonight. West to northwest winds will remain around 10 kt this afternoon, then become light overnight, then pick back up a bit Monday morning once daytime mixing commences. Outlook... Monday Night: VFR. NO SIG WX. Tuesday: Mainly VFR, with areas MVFR possible. Chance SHRA. Tuesday Night: MVFR/IFR conditions possible. Slight chance SHRA. Wednesday: VFR. Slight chance SHRA. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: VFR. NO SIG WX.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Hastings/Sisson SHORT TERM...Nash LONG TERM...Nash AVIATION...Hastings/Sisson

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