Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 181935 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 335 PM EDT Tue Jul 18 2017 .SYNOPSIS... A ridge of high pressure will bring warmer and drier conditions to the area today and tomorrow before another frontal system moves in on Thursday and Friday with a chance of showers and thunderstorms. A little bit cooler and drier weather are likely by Saturday under high pressure from Canada. && .NEAR TERM /THROUGH WEDNESDAY/... As of 109 PM EDT Tuesday...Weak surface high pressure continues to ridge into the region this afternoon. The upper level trof is moving out with warm advection aloft. Have noticed a couple tiny showers popping up east of the Greens, but no lightning has been noted. Going forecast is in good shape, previous discussion follows. Tonight should be mostly clear under weak high pressure centered a bit to our south, short wave ridging aloft, and low PWs less than 0.75". Northern St. Lawrence and Champlain valleys will hold onto a weak pressure gradient favoring a bit of a SW and S flow overnight, elsewhere calm or light variable winds will allow for dense river valley fog to form as is typical for this time of year as we enter the time of year with the highest frequency of occurrence for radiational fog. A weak westerly flow on Wed with mostly sunny skies and 850 temps up to 16C will again bring temps into the 80s perhaps topping out around 88 at BTV. A weak cold front moving through Ontario late in the day will bring about a bit of an increase in CAPE (near 500-750 J/kg), PW (1.50"), and clouds in the St. Lawrence Valley late in the day, so just a slight chance of a shower or thunderstorm there. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 321 AM EDT Tuesday...Overall Wednesday night and Thursday looking pretty good with weak high pressure over the area. Any convection near the Canadian Border Wednesday night should dissipate as the night wears on with the loss of instability. Highs on Thursday will be in the low to mid 80s and dew points in the 60 to 65 degree range. These conditions should be sufficient to produce instability Thursday afternoon and forcing from the mountains should be able to produce some showers and possibly a thunderstorm. Parameters for organized storms do not look like they will be a factor. && .LONG TERM /FRIDAY THROUGH TUESDAY/...
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As of 334 PM EDT Tuesday...Northwest flow aloft develops over the region by Friday morning. Models disagree on timing of a disorganized front moving down over our area. The potential is there for showers and some isolated thunderstorms, especially along the higher terrain and along the international border but pining down when exactly during the morning/day/evening is not easy a this time. Flow aloft remains from the west and northwest through the weekend keeping with a chance again of terrain enhanced showers for Saturday. By Sunday, a series of shortwaves will move through the flow and continue to enhance the potential for some showers or storms. As with the previous shift, the models are again at odds with each other for timing and movement of the upcoming systems through the back half of the weekend and early next week, so again have opted to keep just chance showers ad some slight chance of the thunder through the end of the period. High temperatures will be in the low to mid 80s on Friday before a trending down toward seasonal normals and possibly slightly below normal by early next week. Lows will be in the upper 50s to lower 60s.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... Through 18Z Wednesday...VFR for the period. Some afternoon fair weather cumulus will give way to mostly clear skies overnight. Some periods of overnight fog is possible at KMPV/KSLK bringing visibility down to IFR until sunrise. Winds generally south to southwest at 5 to 10 knots during the day then calm after sunset tonight. Outlook... Wednesday Night: VFR. Slight Chance SHRA. Thursday: VFR. Slight Chance SHRA...Slight Chance TSRA. Thursday Night: VFR. NO SIG WX. Friday: VFR. Chance SHRA...Chance TSRA. Friday Night: VFR. Slight Chance SHRA. Saturday: VFR. Slight Chance SHRA. Saturday Night: VFR. Slight Chance SHRA. Sunday: VFR. Chance SHRA...Slight Chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Neiles/Sisson SHORT TERM...Evenson LONG TERM...Verasamy AVIATION...Verasamy

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