Scientific Forecaster Discussion
fxus61 kbtv 241937
Area forecast discussion
National Weather Service Burlington Vermont
337 PM EDT Mon Jun 24 2019
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
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.
Tuesday night: mainly VFR, with local MVFR possible. Slight
chance rain showers.
Wednesday: VFR. Chance shra, slight chance thunderstorms and rain.
Wednesday night: VFR. Chance shra, slight chance thunderstorms and rain.
Thursday: VFR. Chance shra, slight chance thunderstorms and rain.
Thursday night: VFR. Slight chance shra, slight chance thunderstorms and rain.
Friday: VFR. Chance shra, slight chance thunderstorms and rain.
Friday night: mainly VFR, with local MVFR possible. Chance shra,
slight chance thunderstorms and rain.
Saturday: mainly VFR, with local IFR possible. Chance shra,
chance thunderstorms and rain.