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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 151146
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
746 AM EDT Mon Oct 15 2018

.SYNOPSIS...
This week will feature several swings in the weather as we see
warm showers move in today followed by a sharp cold front
overnight. This pattern will be repeated mid week with more rain
and mountain snow showers. Temperatures on the warm days will
be in the mid to upper 50s with cold days in the upper 40s to
near 50. Lows will vary widely between the low 30s behind cold
fronts to mid 40s on warm days. Some minor snow accumulation is
possible this week in the higher terrain.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 732 AM EDT Monday...Latest radar imagery shows some light
rain has just moved into southern NY so we`re still on track to
see the warm advection rainfall push into the North Country by
mid morning. The ENX VWP is starting to show 35kt winds at
3-4kft and so the low level jet is starting to push into the
into the region so we`ll see how much rainfall occurs over the
Champlain Valley.

Previous discussion...Current obs paint quite a different
picture today than last night as the clouds have for the most
part cleared out over Vermont rather than New York and thus in
the cloud free areas temps are in the low 30s. The upper level
system that will bring rain later today is featuring quite the
warm conveyor belt on the WV satellite and is rapidly pushing
clouds into northern New York so temps are a fair bit warmer in
the upper 30s to low 40s.

We are still on track today to see a warm front associated with
that upper level cyclone bringing some warm advection showers
to the North Country. I backed off pretty strongly on the amount
of rainfall in the valleys with this system. The dynamics are
strong enough that as the initial surge of warm advection moves
in most areas should see some rainfall but there`s quite a
different signal in the high res vs low res guidance. I`m
leaning towards the idea that we may see some light rain move
into the North Country between 13-16z ahead of the low level jet
but once the 40-50kt low level jet moves in the rainfall will
become orographically forced as any lee side valleys will be
shadowed pretty strongly. The NAM has 45kts of wind at 925mb in
the 18z sounding at BTV and so if that happens we`ll be on the
outside looking in for rainfall. Given that I trended back on
precip, I trended up on max temps with the idea that we`ll be in
the upper 50s with a chance at a few spot 60`s in the Champlain
Valley.

The best chance for rainfall looks to be just ahead of the
front as surface convergence rapidly increases between 20-23z
as the front sweeps through. I think that`s when we`ll pick
most of our rainfall. Even with backing off the chances for
rainfall and total precip I still feel we`re on track to see
generally a tenth in the valleys with between 0.25-0.5" in the
higher elevations.

In addition to the the rainfall we`ll see moderate to strong
boundary layer winds. That 850mb jet mentioned earlier will push
winds in the higher elevations up towards 45-55mph and will end
up being funneled through the Champlain Valley. I could easily
see gusts in the afternoon pushing towards 20-30 mph out of the
south especially on the more exposed eastern side.

Overnight behind the front the air turns quickly back to cooler
than normal. Anticipate another round of low level strato cu
developing which should limit how cold we get so I`ve bumped up
temps above MOS guidance.

Clouds continue through the day tomorrow as the local BTV CU
sky rule shows we may not break out of the cloud cover til mid
to late afternoon. So the combination of cloud cover and cold
air advection means that we`ll likely be in for a brisk day with
westerly winds turning southwesterly by the nightfall. Expect
max temps Tuesday to peak in the upper 40s to low 50s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 431 AM EDT Monday...Tuesday night an extremely cold upper level
trof will approach the region from the Great Lakes with falling
heights and backing low level flow. In fact, this trof and its NAEFS
forecasted 700/500 mb heights and temperatures are colder than any
in the 1979-2009 CFSR climo with 30+ year return periods and -3 to
-3.5 standardized anomalies making this a truly unusually cold event
for this time of year.

This trof will pick up some moisture from the lakes with some lake
enhanced precipitation to northern areas especially in NY before
midnight spreading across northern VT afterward. Most areas will be
rain showers though some of the highest elevations could be mixed
with snow. Low temps won`t fall too much with readings in the
30s except lower 40s in the St Lawrence and Champlain Valleys.

On Wednesday a cold front will move across the region with rain
showers changing to snow showers with high temps again in the 40s.
Behind the front another period of NW upslope flow is expected and
with 1000-500mb thicknesses falling as low as 516dm in the NEK and
850 temps falling to -10 to -12C (-2.5 std anoms) by Wed night into
Thursday morning. With these temps could see some decent dendritic
snow growth for some light fluffy snow shower accumulations possibly
reaching the lower elevations along the western slopes. Still
thinking the potential exists for total snow accumulations by
Thursday morning of 1-3" in the mountains from 1500 ft to the
summits, a dusting to an inch from 500-1500` and perhaps a few
flurries at the valley floor. Lows will be mainly in the 20s in the
lower terrain to lower 30s in the valleys. In addition NW winds will
be picking up with wind chills falling into the teens and we
won`t even talk about how cold it will be on the summits.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 431 AM EDT Monday...Models in very good agreement in the long
term which features a period of much cooler than normal temps
as the anomalously deep upper level trof progresses quickly
through the northeast US through Thursday followed by a brief
warming with rising heights by Friday. On Saturday, another very
cold digging Canadian trof and cold front approaches with
another shot of very cold air.

The upper level trof moves off to the east on Thursday so any
lingering flurries will come to an end but it will be quite blustery
and cold with highs mainly in the 30s but it will feel colder.
Maybe SLK doesn`t get above freezing.

By Thursday night and Friday some moderation in temps is expected as
the upper level trof moves out followed by some warm advection and
perhaps some weak warm frontal precip in northern areas. Lows
in the 20s and highs rebounding into the upper 40s to lower 50s.

The next cold front and chance of precipitation comes on Saturday
for another round of chilly temperatures. Rain showers will be
changing to snow showers once again. A cold blustery NW flow follows
for Sat night into Sunday with snow showers continuing and it
looks like more light accumulations. Looking at lows dropping
back in the 20s and lower 30s and highs in the 30s to lower 40s.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Through 12Z Tuesday...Expect VFR conditions through 13-14z this
morning before a warm front brings lowered ceilings and
visibilities. The LIFR fog at MPV should mix out by 13z as the
winds start to pick up. The latest thinking is that we`ll be
mainly VCSH in at PBG and BTV with -SHRA at RUT beginning
shortly after 13-14z and lifting towards the northeast.
Ceilings will generally become MVFR with brief periods of IFR
possible in showers. Winds will pick up quickly out of the
south to southwest and become fairly gusty by mid afternoon as a
modest low level jet will bring the potential for some low
level turbulence as mountain waves will be possible. Anticipate
the gusts ahead of the front to be as high as 25-30kts
especially at SLK/MSS/BTV. Behind the front westerly 10-20kt
winds will push in through the overnight hours Tuesday morning.

Outlook...

Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. Chance SHRA.
Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA,
Chance SHSN.
Wednesday Night: Mainly VFR, with local MVFR possible. Slight
chance SHSN.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: Mainly VFR, with local MVFR possible. NO SIG WX.

&&

.MARINE...
As of 431 AM EDT Monday...A lake wind advisory is in effect
today as strong southerly winds will pick up in the morning
hours becoming 20-30kts as the pressure gradient ahead of an
advancing cold front tightens. Expect choppy conditions today on
the lake as there should be a decently long fetch. Waves on the
northern side of Lake Champlain will be approaching 2-4 feet
with locally higher waves possible. This will impact Cumberland
Bay and most of the broad lake.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Deal
NEAR TERM...Deal
SHORT TERM...Sisson
LONG TERM...Sisson
AVIATION...Deal
MARINE...