Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
734 PM EDT Friday Jul 31 2015
a series of disturbances in the flow aloft will bring scattered
showers and isolated thunderstorms to the north country tonight
through Saturday. Weak high pressure brings drier conditions
Saturday night into Sunday before the weather turns unsettled again
Sunday night into early next week.
Near term /until 7 am Saturday morning/...
as of 725 PM EDT Friday...daytime fair weather cumulus clouds have
largely dissipated across the north country per early evening
visible satellite imagery with onset of diurnal cooling cycle.
Combined with low dewpoints/dry vertical column...will have good
viewing conditions across most of the region for the rise of the
Blue Moon between 810-820pm. Only exception will be portions of
St. Lawrence County with upstream shortwave trough bringing
scattered showers into the St. Lawrence Valley next 1-2 hours.
Leading showers just west of the St. Lawrence River...and will
maintain chance probability of precipitation across northern New York late evening...and ultimately
increasing clouds and 20-30 probability of precipitation across northern Vermont during the
overnight hours. Some light precipitation is forecast with rainfall
amts expected <0.10". Some weak elevated instability rooted around
800mb indicated by 18z NAM (generally 100-200 j/kg)...so
maintaining isolated thunderstorms with a few rumbles possible (bulk of
thunderstorm activity will progress north of the international border per
latest radar trends). Min temperatures expected to be mostly in the
upper 50s and lower 60s. With increasing clouds and surface dewpoints
in the 50s...fog potential appears limited. Winds overnight
generally light S-SW 5 miles per hour or less.
Short term /7 am Saturday morning through Sunday night/...
as of 351 PM EDT Friday...for Saturday through the rest of the
weekend...our weather will be largely dominated by fast cyclonic
flow aloft as a deep upper low takes up residence over Hudson Bay.
Several shortwave troughs moving through the flow will bring
scattered showers and a few isolated thunderstorms with the
highest probabilities of precipitation coming Saturday and then
again later Sunday night.
First shortwave will be departing Saturday morning...with another
weak disturbance moving through later in the day. This combined with
some weak surface based instability and steepening lapse rates
with some cooling aloft will result in at least scattered showers
along with the chance of a few thunderstorms. Maximum temperatures expected
to be in the middle 70s to lower 80s.
Any lingering showers should end Saturday night with loss of daytime
heating with lows again in the middle 50s to lower 60s. Mainly dry
weather expected to continue into Sunday with just the low chance
for a few scattered showers or perhaps a thunderstorm. Temperatures remain
close to seasonal norms with highs in the upper 70s and lower 80s.
Chance of showers increases once again later Sunday night with
approach of next shortwave from the Great Lakes region.
Long term /Monday through Friday/...
as of 256 PM EDT Friday...persistence is the name of the
game...thus discussion borrowed from midshift as the longer term has
looked the same for several days now. No heat waves on the
Broad upper troughing and seasonal middle-Summer temperatures for the
longer term. Precipitation chances will be tied to passing
shortwaves rotating through the base of the mean eastern Canada
trough, with the strongest of these features swinging through Monday
into Monday night with a decent threat of showers and thunderstorms.
Given timing and evidence of instability/increasing 0-6km shear some
of the convection could trend on the more robust side. Time will
tell. Outside of this time period, slight to low chance probability of precipitation (20-
40%) will be maintained for much of the period, suggesting that
while dry weather should be the general rule, a few showers will be
around from time to time. As mentioned above, temperatures will by
and large range within a few degrees of seasonal norms with daily
highs mainly in the 70s to around 80 (slightly warmer on monday) and
overnight lows in the 50s to around 60. R broad upper troughing and
seasonal middle-Summer temperatures. Precipitation chances will be tied
to passing shortwaves rotating through the base of the mean eastern
Canada trough, with the strongest of these features swinging through
Monday into Monday night with a decent threat of showers and
thunderstorms. Given timing and evidence of instability/increasing 0-
6km shear some of the convection could trend on the more robust
side. Time will tell. Outside of this time period, slight to low
chance probability of precipitation (20- 40%) will be maintained for much of the period,
suggesting that while dry weather should be the general rule, a few
showers will be around from time to time. As mentioned above,
temperatures will by and large range within a few degrees of
seasonal norms with daily highs mainly in the 70s to around 80
(slightly warmer on monday) and overnight lows in the 50s to around
Aviation /00z Saturday through Wednesday/...
please see equipment section below for krut data outage
Through 18z Saturday...mainly VFR through the period with scattered
clouds in the 040-070agl range, broken at times over the higher
terrain. Winds generally west to southwesterly through the period,
around 10 kts with occasional gusts from 18-00z then light. After
00z ceilings trend occasionally broken from 035-060agl with approaching
trough which should spark scattered showers, mainly at kmss/kslk
terminals. A few showers may also encroach toward the
kpbg/kbtv/kmpv terminals after 06z but confidence lower. Brief
MVFR visibilities possible with this activity, mainly at kslk.
Thereafter...VFR with scattered-bkn040-060 and vicinity rain showers across the
region as afternoon approaches.
Outlook 18z Saturday through Tuesday...mainly VFR. Chance of
daily scattered showers/isolated thunder, especially on Saturday
and again by next Monday. Brief MVFR conds possible with any
heavier showers. Patchy IFR in br/fog possible at kmpv/kslk 06-12z
each morning, but synoptic setup not generally favorable for
persistent or widespread coverage.
AWOS observational data from the Rutland/southern Vermont
regional Airport (krut) remain unavailable at this time. For
aviation partners current observations may be accessed via telco.
Please reference FAA krut notam 07/007 for more information.