Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
324 PM EDT Tuesday may 5 2015
a ridge of high pressure will build across the north country
tonight...lasting right though the workweek. Mostly sunny
skies...above normal temperatures and dry conditions will
continue through Friday with an associated concern for wildfire
danger. Conditions then turn more unsettled into the weekend
which offers the next chance for precipitation for the north
Near term /until 7 am Wednesday morning/...
as of 324 PM EDT Tuesday...large-scale middle-level confluent flow
regime in place across the north country this afternoon, with
surface ridging prognosticated to build southeastward from eastern
Ontario tonight. Leftover baroclinic zone from the cold frontal
passage this morning trails back to a quasi- stationary boundary
over the lower Great Lakes, with high clouds streaming in
northeastward. The boundary itself remains to our south, but
aforementioned high clouds will continue to stream in into the
overnight. So not a completely clear night, but the high clouds
won't be enough to stop temperatures from falling quickly tonight
either. Relative humidities rebound from low afternoon values with
the falling temperatures. Looking at lows from a few degrees above
freezing in the Adirondacks to the low/middle 40s elsewhere.
Short term /7 am Wednesday morning through Thursday night/...
as of 324 PM EDT Tuesday...main message in this period is high
and dry, as high-amplitude middle- level ridge builds in aloft.
Sensible weather conditions pretty similar each day and night,
with mostly clear skies producing sizable diurnal ranges with
abundant daytime sun and sharp cooling at night. Winds will
generally be light and largely terrain/lake- breeze driven as
well. The primary concern in this period will be the continued low
relative humidities and extremely dry fine fuels making the north
country susceptible to wildfires. For more specific details, see
our fire weather section below.
Thermal fields warm by a couple degrees each day, up to around +10
to +11c at 850 mb by Thursday. We should mix to this level at least,
but likely even higher than that. After upward adjustments to highs
due to sunshine and dry soil moisture conditions, looking at highs
into the 70s by Wednesday and then the upper 70s/spot 80 degrees on
Thursday, with lows in the 40s Wednesday night and the upper 40s-low
50s Thursday night. From a moisture perspective, still have a Good
Reservoir of 925-700 mb drier air to mix down, but guidance forecast
soundings show progressively higher moisture in this layer each day.
It means dewpoints aren't likely to fall quite as much as we've seen
over the past couple of days. So afternoon min relative humidity
levels should stay in the 20-30 percent range through the period,
due to roughly offsetting effects from warming air temperatures and gradual
rise in dewpoints.
Long term /Friday through Tuesday/...
as of 351 am EDT Tuesday...above normal temperatures continue
through the extended portion of the forecast. Weather will be
quiet on Friday as surface high pressure off the coast of New
England will be main weather feature. There will be increasing
chances for showers over the weekend as a series of low pressure
systems cross north of our forecast area. Some differences between
the GFS and European model (ecmwf)...though not significant. Low passes north of
the area Saturday and cold front approaches from the northwest. A
second low passes even closer to our area on Sunday and front
remains nearly stationary to our northwest. Looks like it will be
a cloudy weekend with a few chances for some light rain
showers...though not seeing abundant low level moisture at this
time. Have slight chance for some thunder on Saturday as well.
Aviation /19z Tuesday through Sunday/...
through 18z Wednesday...VFR with no precipiation or restrictions
to visibility over the next 24 hours. Winds generally light west
to northwesterly and less than 10 knots through the period with
passing scattered to occnly broken high clouds from 20 to 30 kft above ground level.
Outlook 18z Wednesday through Sunday...
18z Wednesday-12z Saturday...VFR conditions with weak surface
high pressure prevailing for much of the period.
12z Saturday-00z Monday...mainly VFR with areas of MVFR/IFR in
scattered showers and thunderstorms.
as of 318 PM EDT Tuesday...a Special Weather Statement remains in
effect for all of Vermont through 6 PM this evening due to fire
Weather conditions will continue to remain favorable for fire
weather through the rest of the workweek. Light winds are
anticipated through Friday, which will preclude a red flag condition
across Vermont and northern New York. However, minimum afternoon
relative humidity values will still fall into the 20 to 30 percent
range. In addition, one- and ten-hour fuels are already extremely
dry due to several days of sunshine and a lack of precipitation
(under two tenths of an inch from last night's frontal passage).
Futher drying of these fuels will continue to take place, and with
these conditions, fire weather concerns will linger into Friday.
as of 318 PM EDT Tuesday...boaters should keep in mind that water
temperatures remain cold - in the 40s. Swimming early in the
season is discouraged as immersion for prolonged periods of time
could produce hypothermia given these water temperatures.