Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 241937 AFDBTV AREA FORECAST DISCUSSION National Weather Service Burlington VT 337 PM EDT Mon Jun 24 2019 .SYNOPSIS... Our nice weather will come to an end during the overnight hours as rain showers will move into the region early Tuesday during the pre dawn hours. Showers will move into northern New York early and then into Vermont by mid morning. We can expect increased cloudiness, rainfall, and possible thunderstorms as the system moves through. That sets the stage for the rest of the week as we`ll see chances for showers with embedded thunderstorms through much of the end of the week. We may see a dry day but then another more organized frontal system will track through on Saturday. && .NEAR TERM /THROUGH TUESDAY NIGHT/... As of 329 PM EDT Monday...The pleasant weather should continue through this afternoon as sunny skies eventually give way to increasing clouds this evening. Most areas today warmed well into the upper 70s to low 80s and with relative humidities dropping into the 30% to 40% range, its been quite the nice day across the North Country. Unfortunately a pattern change will be coming as the high pressure and upper level ridge that has been in place will start pushing towards the east and a cold front will start sliding through the North Country. Rain will spread into northern New York overnight and then begin to overspread the rest of the North Country during the morning hours. Trends in the guidance still point to a sharpening of the ridge axis to our east and that results in two things. 1 - The best forcing for any thunderstorm development gets displaced well to our north and west. 2 - Our warm cloud depths increase to near 12,000 feet. This means that while the lightning chances are decreasing, the overall rainfall threat is increasing. With the headwaters flow guidance between 2-3 inches over 3 hours we should be safe from any river flooding but I anticipate the rainfall is going to come down fairly heavy at times. Rainfall totals should be in the 1/2 to 3/4 of an inch range basin averaged but could be locally higher. The cold front tracks through the North Country Tuesday evening and showers will slowly be coming to an end as partly cloudy skies return. Expect lows behind the front to be bit more humid as temps only fall into the mid 60s with upper 50s dew points. && .SHORT TERM /WEDNESDAY/... As of 329 PM EDT Monday...Wednesday should start with a mostly clear and pleasant morning. A surface trough extends south from low pressure across the Hudson Bay in Canada. 925mb temperatures should warm to 20C and mostly clear skies. Highs will reach the low to mid 80s across most of the North Country, and dewpoints should creep into the 60s. Looking for key ingredients to convection (instability, moisture, and a lifting mechanism), it appears we should be 2 for 3. Diurnal instability should yield surface based CAPE of 500-1500 J/kg during the afternoon. Additionally, lapse rates improve to 7-8 C/km during the afternoon with hints of an elevated mixed layer later in the evening, which should allow us to maintain some instability beyond sunset even. The aforementioned trough and a weak, mid-level vort max will act as the lifting mechanism with Q-vectors convergence across the North Country with the trough coming through later Wednesday evening. We will also be positioned in the favorable left exit region of an upper jet. The main inhibiting factor will be lack of deep moisture. Thus, organized convection is not anticipated, despite 25-35 kts of 0-6km shear, instead favoring a scattered convection along a broken line or two. Anticipate convection to be slow to develop Wednesday with activity largely confined between 2 PM Wednesday through 2 AM Thursday. Thunder will be less likely across eastern Vermont, where developing easterlies will advect a more stable, maritime airmass. Convection gradually wanes overnight with otherwise partly cloudy skies, so we should lows cool to the upper 50s to mid 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... As of 329 PM EDT Monday...Mainly making slight tweaks and adjustments based on the latest forecast guidance. Thursday should be fairly similar to Wednesday, but there will be less instability and moisture available. Height rises should also limit convection, but should still see some develop with the greatest chances along the International Border. It`s a persistence forecast for Friday. Then, a cold front shifts south on Saturday, which should result in another day of afternoon showers and storms followed by cooling. Unfortunately, the amplification of upstream ridging causes a potent upper shortwave trough, possibly even closed low, to plunge southwards on Sunday. So showers remain a part of the forecast. This will also result in temperatures becoming cooler than normal, generally hovering in the low to mid 70s for the start of next week. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... Through 18Z Tuesday...VFR conditions are expected through most of the period. Increasing cloud cover will continue through the rest of the overnight hours and start to lower between 6-10z overnight. Anticipate rain showers spread towards the east generally after 10z and becoming prevailing during the morning hours Tuesday. MVFR ceilings and brief MVFR visibilities will be possible through much of Tuesday. Winds will be under 10 knots through the entire period. Outlook... Tuesday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Wednesday: VFR. Chance SHRA, Slight chance TSRA. Wednesday Night: VFR. Chance SHRA, Slight chance TSRA. Thursday: VFR. Chance SHRA, Slight chance TSRA. Thursday Night: VFR. Slight chance SHRA, Slight chance TSRA. Friday: VFR. Chance SHRA, Slight chance TSRA. Friday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Saturday: Mainly VFR, with local IFR possible. Chance SHRA, Chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Deal NEAR TERM...Deal SHORT TERM...Haynes LONG TERM...Haynes AVIATION...Deal

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