Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
353 am EDT Tuesday Oct 21 2014
an extended period of precipitation has begun over the north country
as an upper level trough of low pressure slowly move across the
northeast United States. Eventually this system will stall off the
southern New England coast and develop an easterly fetch of moisture
from the Atlantic late Wednesday into Friday. The net result of this
scenario will be scattered to numerous showers over the area today
and tonight...then the development of a more widespread rain
Wednesday into Friday.
Near term /until 8 PM this evening/...
as of 353 am EDT Tuesday...an upper level trough of low pressure just
to our west early this morning is enhancing scattered to numerous
showers across the area and as this system moves slowly east today...
the showers will linger over the area along with plenty of cloud
cover. This will have an effect on the temperatures with highs in
the upper 40s to middle 50s.
Short term /8 PM this evening through Thursday/...
as of 353 am EDT Tuesday...the upper trough begins to start cutting off
tonight as it reaches the middle-Atlantic coast Wednesday morning. This
feature will only reach the southern New England coast by Thursday.
As a result...we are looking at an extended period of precipitation...
thermal profile indicates it will all be in the form of rain...
especially Wednesday and Thursday. This is when a deeper easterly
fetch of moisture from the Atlantic moves into the region and enhances
precipitation. The easterly component will result in some upslope
precipitation along the eastern slopes of the Green Mountains and
northern Adirondacks. Some downsloping is also expected to occur...
especially over the Northeast Kingdom of Vermont. However...the
duration of the easterly fetch will not be too long as eventually
the low level flow will become more northeast with time on Thursday.
Bottom line...after a distinct west to east gradient of precipitation
chances tonight...less west more east...the areal coverage of the
precipitation will expand westward Wednesday and Thursday. Precipitable
water values will be about 150 percent above normal...and with an
upslope component to the flow...looking at a general 1 to 2 inches
of rain with some higher amounts along the east slopes of the Green
Mountains and parts of the Champlain Valley and northern Adirondacks.
With all the clouds and precipitation...little diurnal change in
temperatures is expected with lows in the 40s each day and highs
in the middle 40s to lower 50s each day.
Long term /Thursday night through Monday/...
as of 340 am EDT Tuesday...the north country will remain under
the influence of the much talked about large upper low Thursday
night through Friday night as it continues its track northeast
from Cape Cod 00z Friday to the Gulf of Maine and Canadian Maritimes
by 12z Sat. Copious amounts of Atlantic moisture will continue to
stream into the forecast area on north-northeast flow with
additional rainfall amounts of of a quarter to half inch through
Going into the weekend...weather remains unsettled with some
uncertainty in regards to the strength and depth of another and
upper low moving through central Canada. Latest European model (ecmwf) digs the
trough much further south than the GFS offering a continuation of
our cold autumn pattern with the 500mb low closing off over Maine
Sunday night into Monday. Not going to completely bite off on the
Euro yet...but with its recent good performance in the past couple
of weeks it's hard to ignore. Will trend slightly cooler than the
consensus blend and offer temperatures just a little below climatology in the
40s and 50s. Some lingering showers will be around as well through
the weekend...especially across the northern mountains.
It looks as though we might see some relief from the cold and wet
conditions to start next week as an upper ridge over the central
Continental U.S. On the weekend shifts eastward onto the eastern Seaboard with
building surface high pressure over the southeast. As the high
shifts off the coast Monday and a developing area of low pressure
in the Lee of The Rockies moves in the Great Lakes
region...southerly flow increases across the northeast with temperatures
warming back above normal in the 60s.
Aviation /08z Tuesday through Saturday/...
through 06z Wednesday...current VFR conditions will slowly
deteriorate over the next 24 hours as low pressure over the
eastern Great Lakes moves off the middle-Atlantic coast this evening.
Showers will spread northward overnight with rain expected across
the region by mid-day...though not looking at any real restrictions
in visibility per upstream observation. Ceilings are another story though.
Kslk/krut/kmpv will generally lower to only MVFR through the
daylight hours...then possibly down to IFR after 00z. Just northwest of
kmss ceilings are IFR on northeast flow...and these lower ceilings
should shift into the St. Lawrence Valley from 08-10z and remain
there through the taf period. For kpbg/kbtv...when winds shift to
the north-NE feel IFR ceilings north of the border will drain down the
Champlain Valley...likely middle-morning for kpbg and towards the
evening for kbtv. Winds will generally by light from 5-10kts and
variable in direction from site to site. Exception will be kmss
where NE winds will increase to a steady 10-15kts through the day.
Outlook 06z Wednesday through Saturday...
06z Wednesday - 12z Friday...periods of rain with prevailing MVFR/IFR
conditions as low pressure lifts slowly northeast along the New
12z Friday - 00z sun...slowly improving conditions as low pressure moves
away to the northeast and coverage of rain diminishes over time.
Some lingering IFR/MVFR likely early in the period...trending to
mainly VFR after 12z Saturday.
rivers across the area are starting out low before the start of the
precipitation event the next few days. The larger rivers across the
area are generally 5 to 10 feet below normal. Total rainfall amounts
will come over a long period of time...today through Friday...and we
are looking at a general 1 to 2 inches with some higher amounts in
the upslope regions along the east slopes of the Green Mountains and
the northern Adirondacks of New York. River levels will rise as a
result...but no flooding is expected at this time. The situation
will continue to be monitored nonetheless.