Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 241731 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 131 PM EDT Sun Jul 24 2016 .SYNOPSIS... Other than areas of fog this morning it looks like we will have a break from the storms today with plenty of sunshine and high temperatures generally in the 80s. The dry weather will be short lived as the threat for more showers and thunderstorms returns Monday afternoon and evening. And as has been the case with the last couple of events...some of the storms could be strong to severe. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 131 PM EDT Sunday...Just a fantastic Sunday afternoon out there with just a few high clouds streaming overhead and comfortable temps in the 70s, dewpoints in the 50s. Adjusted max temps down a couple of degrees from the previous forecast based on trends, which now top out in the mid/upper 70s with a few isolated 80s possible. For tonight, upper ridge currently over the eastern Great Lakes shifts overhead of the North Country. Skies won`t be particularly clear with some convective debris clouds from activity currently over Michigan/Ohio drifting in, but conditions will remain dry with temps comfortable again in the mid/upper 50s east to the mid upper 60s west. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... As of 406 AM EDT Sunday...Monday: 00z guidance suite in okay agreement amongst one another, but as typically the case, it`s those subtle differences that really are the keys to locking in the details. that said, there still continue to be a number of items in the "pro strong convection" category. those being: shortwave moving into the area at peak heating time, an elevated mixed layer (EML), surface instability (model mean CAPE values 1500-2000 J/kg), decent 0-6km shear of 40- 45kt (esp later in the afternoon). in the "con strong convection" arena, question about how much sunshine we`ll be able to get as there could be some debris clouds during the morning, no strong low level convergence, fairly warm layer around 800 mb which may act as a cap to updrafts. after back and forth discussion (in my head, and with the other forecaster here), I think most things will come together for at least scattered convection to develop - that will have the potential to become locally strong. SPC`s latest Day 2 outlook keeps the region in a "Marginal Risk" for severe thunderstorms due to the uncertainty. That assessment seems reasonable at this point. Have added some enhanced characteristics to the forecast, namely to add in the potential for strong gusty winds and small hail with thunderstorms during the afternoon/early evening. Speaking of that warm layer aloft, models indicate 925mb temperatures could warm to as much as 25C. Mixing that down to the surface under perfect situation (sunshine and well mixed boundary layer) would result in temperatures reaching the mid-90s! In fact, some aspects of Monday`s setup appear similar to what we saw on Friday, where the warm layer aloft did cap convection for much of the day and allowed temperatures to soar into the 90s. At this point due to the uncertainty of cloud cover (thinking there will be some) and the fact that the majority of guidance has mid 80s for highs, I did go warmer than most guidance, but still played it a bit conservative and painted in Upper 80s to a few spot 90F in the valleys. Anticipate scattered thunderstorms to develop in the morning across northern NY and then spread east throughout the afternoon. Bulk of the storms should be east of the forecast area shortly after 21z (5pm), however some instability will continue across western half of the region into the early evening as those areas could have a chance to "reload" thanks to sunshine after the initial batch of storms earlier in the afternoon. So for PoPs, I ramp up to the 45-60% level by mid afternoon, then show a decrease, but keeping some 20- 30% PoPs going until a bit after midnight for eastern VT. Convective mode will probably start with isolated cells, a line forming during the afternoon. Primary threat would be strong wind gusts. Monday Night: residual thunderstorms wind down for the first half of the night across eastern sections. It will still be warm/muggy overnight as there isn`t any cold front out there. Tuesday: We`ll be on the backside of the trough responsible for Monday`s action. Generally means subsidence aloft, and this should be the case. Thus looking for a mostly sunny day. Guidance does suggest a little bit of moisture hung up across the Northeast Kingdom of VT and with that area being closer to the upper trough, a shower or two is not out of the question early in the day. Otherwise with 925mb temperatures in the 18-20C range, we will readily top out in the lower to mid 80s in the valleys. This is several degrees above normal. Tuesday Night: quiet and calm, but still mild. Generally lows in the upper 50s to lower 60s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 406 AM EDT Sunday...Decent agreement between the 00z GFS and ECMWF for much of the period. Wednesday should be dry and very warm. 925mb temperatures are a couple of degrees warmer than Tuesday, so we`ll see highs well into the 80s, perhaps a few lower 90s in the southern valleys. Hints of slight 500mb height falls and a weak surface front to our north that will probably be a focus for a few thunderstorms across Quebec. That feature should stay away from here based on 00z guidance, but previous runs didn`t have it as close. So perhaps that is a trend? Thursday is a little trickier. Even though the 00z suite are similar, they are differing from the 12z counterparts. At face value with the 00z models, it would be a generally sunny and hot day (925mb temperatures pushing 24C which would be mid 90s in valleys) and still show a front just to our north. Previous runs had moisture pushing up from the southwest. Thus will maintain idea of 20-30% chance of showers/t-storms. Won`t buy into the heat just yet, but even then, it will be another warmer than normal summer day (mid 80s at least). Friday a deeper southwest flow pattern should be established, and models bring increasing moisture into the region. Thus we should see more in the way of clouds and scattered showers/t-storms, and temperatures closer to normal assuming more clouds. Saturday is more "iffy". GFS continues the moist southwest flow pattern with a shortwave off to our west. That would mean a rather unsettled day. 00Z Euro has a weak ridge in place with light northerly flow, which would suggest dry and mild. Forecast will show a blend, which actually works out to climatology. Don`t cancel outdoor plans yet for Saturday. && .AVIATION /18Z Sunday THROUGH Friday/... Through 18z Monday...VFR conditions through the period. FEW/SCT cirrus this afternoon will lower to 10-15kft range and increase overnight before clearing out tomorrow morning ahead of our next system. Mid clouds approach the St. Lawrence valley towards mid- day. Winds variable 5-10kts today, light tonight, trending SSW tomorrow at 5-15kts with gusts up to 20kts west. Outlook 18z Monday through Friday... 18z Mon - 06z Tue: Mainly VFR with scattered to numerous showers and thunderstorms briefly reducing ceilings/visibilities to MVFR/IFR. 06z Tue - 00z Fri: Mainly VFR under high pressure. Isolated showers possible Wed/Thu afternoons. 00z Fri - 00z Sat: Increasing chances for widespread MVFR showers and isolated thunderstorms. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Lahiff SHORT TERM...Nash LONG TERM...Nash AVIATION...Lahiff

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