Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 212349

Area Forecast Discussion
National Weather Service Burlington VT
749 PM EDT SAT MAY 21 2016

Low pressure will settle into the mid-Atlantic states over the next
24 hours, then weaken as it drifts slowly northeast along the New
England coast by next Tuesday. As a result, scattered showers will
be possible on Sunday, then again by next Tuesday with Monday being
primarily dry. Temperatures will remain seasonably mild through
Monday, then trend warmer by the middle and later portions of next


As of 749 PM EDT Saturday...Previous forecast in good shape, so
no changes have been made. Surface observations showing large
temperature/dew point spread, so any showers that do fall out of
the clouds will likely evaporate before reaching the surface.

Previous discussion from 300 PM EDT Saturday...A generally quiet
night remains on tap for the area as surface ridging is bridged
aloft by lingering upper troughing at mid and upper levels. Models
remain consistent in digging the upper energy southward and over
time as it becomes a closed center in the vicinity of the northern
mid- Atlantic states by Sunday morning. Broad southwesterly flow
aloft will allow thickening mid and upper level clouds to filter
into our area overnight with only a minimal/outside shot at a
stray shower or sprinkle across our southern counties. Believe the
output from most recent runs of the HRRR and assorted CAMs are
overdone in their depiction of blossoming showers in this area
this evening due to erroneously high surface dewpoints and
resultant instability. Based off current radar trends, the
thickening upper clouds and a quite dry boundary layer have
downplayed this idea accordingly, opting instead for just a very
low end threat in the 15-20 percent range this evening into
tonight. Low temperatures should run a bit milder than last night
given the clouds, generally mid 40s to lower 50s. Winds light.

By Sunday the upper closed energy will pivot across the mid-Atlantic
region as background flow trends more north to northeasterly.
Low to mid-level convergence along the old trough line combined with
slightly higher moisture should spell continued mostly cloudy skies
along with scattered to numerous showers, especially across the
central and eastern portions of Vermont and the Adirondacks where
added input from terrain-induced flows will occur. Drier conditions
more likely in the northern Champlain Valley west into the St.
Lawrence River Valley where higher probabilities of partial sunshine
will exist. Also continued an outside shot of a few non-severe
thunderstorms per most recent SREF calibrated t-progs of
approximately 20 percent and some low-end mixed-layer CAPE to
perhaps 500 j/kg. With the higher abundance of clouds high
temperatures will be slightly cooler than today, mainly mid 60s to
lower 70s, perhaps mid-70s out across the St. Lawrence Valley.


As of 340 PM EDT Saturday...Any showers or thunderstorms will be
ending early sunday night as mid-level trof axis gradually shifts
to the southeast leaving a drying NE flow in place. Little change
in air mass, and with surface dewpoints expected in the upper
40s/lower 50s, areas seeing rainfall during Sunday will be prone
to some fog formation Sunday night. low temperatures will
generally in the lower 40s to lower 50s.

A closed upper low forms east of the Delmarva peninsula during
the day Monday, with an elongated trough axis still in place along
the New England coast. precipitation from this system should stay to
the south and east of the forecast area, as GFS depicts 1000-
500mb and some precipitable water drying across northern NY and
northern VT with continued N-NE flow. with 850 temps around 10c
expecting High temperatures on Monday generally 74-78F degrees
with North winds 5-10 mph.

Models in good agreement that the closed low moves slowly
northward monday night east of NJ by tuesday morning, so the
deeper moisture begins to return with precipitable water values
increasing to near an inch in southern vermont. this is enough to
bring a low chance of showers back to southern vermont. again
little change in overnight lows with readings in the mid 40s to
mid 50s.


As of 340 PM EDT Saturday...reasonable model agreement in the
long term with a gradual pattern shift toward a more summery warm
and more humid airmass with chances of showers and thunderstorms.
Of course the daily details vary and we may have to contend with a
backdoor front next weekend, but it`s just too soon to tell for

Models are generally consistent in tracking the closed upper low
from east of NJ Tue morning through eastern MA by 06z Wednesday
before bumping east of New England Brunswick by Wednesday
afternoon followed by a general WSW flow aloft with rising
heights by saturday.

The North Country will reside on western periphery of the
cyclonic flow regime on Tuesday, with axis of instability (Best BL
CAPE values of 500-1000 J/kg) across the region from n-central VT
SW into portions of the northern Adirondacks during the peak
heating hrs. Expectation is for scattered showers and possible
thunderstorms to develop with slow westward or southwestward storm
motions. PW values continue around 1" may result in some locally
heavy downpours, and with WBZ heights around 9kft, can`t rule out
some small hail with any stronger cores. PoPs on Tuesday generally
30-50%, highest southeast where east of the green mountains it
will be cloudier and cooler with highs in upper 60s to near 70
while it will be more unstable further north and west where temps
get into the 70s resulting in scattered showers and thunder.

On Wednesday flow becomes more NW behind departing upper low but
enough convergence and terrain-induced lift enough for a low
chance of showers or isolated thunderstorm, but should see high
temps in the upper 70s to around 80 as 850 temps rise to 10 to

Thursday into Saturday low-level flow becomes SW and a more moist
and unstable air mass advects into the region for with showers and
possible thunderstorms possible. GFS/ECMWF differ on the near
surface details with the location of a warm/backdoor front but PoPs
Generally 30-40% each day. Should see higher humidity values
(dewpoints in the upper 50s to lower 60s possible) Thursday and
Friday with high temperatures in the upper 70s to lower 80s but
could be slightly warmer or cooler depending upon the status of
the front.


.AVIATION /00Z Sunday THROUGH Thursday/...
Through 00Z Monday...VFR through the forecast period with broken
mid to high cloud cover in place and remaining. Winds generally
light south to southwesterly with slight variation per
terrain/lake breeze influences, trending light overnight. After
12Z Sunday broken to overcast mid level VFR ceilings in the
050-090 AGL range continue as winds trend light north to
northeasterly 5-10 kts. Increasing confidence that scattered
showers/isolated thunderstorms will develop across
eastern/southern VT and portions of the Adirondacks after 15Z and
drift southwesterly over time. Have gone ahead and mentioned a
prevailing group at MPV and RUT where best chance to see
showers...vcsh mentioned at BTV, PBG, and SLK.

Outlook 00Z Monday through Thursday...

00z Mon - 06z Mon: Mainly VFR with periods of brief MVFR
visibility possible in rain showers/isolated thunder at all
terminals except MSS.

06z Mon - 12z Tue: VFR/high pressure

12z Tue through 00z Thu: Mainly VFR with chance of showers and
brief MVFR visibility with coastal low pressure system passing by
to the east. Highest confidence of showers at eastern terminals.

00z Thursday onward: VFR/high pressure.




LONG TERM...Sisson
AVIATION...JMG/Neiles is the U.S. government's official web portal to all federal, state and local government web resources and services.