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  Monday October 14, 2019

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 141036
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
636 AM EDT Mon Oct 14 2019

.SYNOPSIS...
A weak front will move through today, accompanied by some
clouds and a few spotty light showers. The next chance for
widespread rainfall comes Wednesday as a low pressure system
moves through the area. Temperatures will be close to seasonal
normals through Wednesday, then turn noticeably cooler Thursday
and Friday behind the low.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 631 AM EDT Monday...Tricky hourly temperature forecast
this morning. Some areas (mainly the Saint Lawrence Valley and
the Champlain Valley) experiencing southerly flow through the
night and near steady temperatures. Other areas (eastern VT and
the northern Adirondacks) saw sharply falling temperatures
overnight under favorable radiational cooling conditions. Have
been tweaking temperature forecast to capture these trends.
In addition, have added mention of some valley fog in the CT
River Valley.

Previous discussion...Satellite imagery showing a large
occluded low pressure system centered near Lake Superior. The
southeastern fringes of cloud cover associated with the system
are poised to enter the BTV forecast area from the west later
this morning. These clouds are in associated with a weak
cold/occluded front that the system will push through the
northeastern US today. Ahead of the boundary, VAD wind profiles
are picking up on increasing southwesterly winds just off the
surface. This flow has kept limited diurnal cooling in the
overnight hours, resulting in relatively warm overnight lows. As
the wrapped up system progresses east today, low-mid levels
will experience cooling temperatures...leading to increased low-
level instability. In conjunction with weak forcing along the
frontal boundary, the pattern will support the development of a
few showers during the day today. Best dynamics/upper-level
support for deep lift remain well removed to our north, and
moisture advection is marginal at best. Thus, expecting any
showers to be light and spotty in nature, with QPF amounts
limited to only a trace to a few hundredths of an inch. The
northern Adirondacks and the northern Greens have the best
chance for measurable precipitation as local moisture advection
is briefly enhanced downstream of Lake Ontario. High
temperatures today will be in the mid 50s to low 60s over
northern NY, and low to mid 60s in VT.

Low clouds will linger tonight behind the frontal passage, with
moisture trapped beneath a strengthening subsidence inversion.
Best chance for some lifting clouds/best radiational cooling
potential exists further west over northern NY, where overnight
lows will be in the low 30s. Vermont will retain a higher degree
of insolation from the lingering clouds, and can expect lows in
the mid to upper 30s.

Tuesday will feel the full effects of high pressure tracking
from the Mid Atlantic into southern New England. A beautiful day
is expected with clouds lifting through the morning and plenty
of sun for the afternoon. Winds will be light and highs slightly
cooler in the low to mid 50s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 328 AM EDT Monday...Surface high pressure will depart the
region Tuesday night ahead of the advancing frontal system expected
to impact the region on Wednesday. An increasingly strong pressure
gradient is expected to develop across the North Country through the
overnight hours in response to the departing high and approaching
front. This will yield increasing winds through the overnight period
with gusty winds in the 25 to 35 mph range expected to develop
during the day on Wednesday. The overall set up hasn`t changed with
a mature extratropical cyclone crossing the Great Lakes during the
day with a secondary low forming along the triple point at the
intersection of the warm front and cold front off the coast of
Virginia. This secondary low will quickly become the main focus with
the low north of the international border weakening and ultimately
phasing with the low off the northeast coastline late on Wednesday.
The latest model trends relating to the timing of precipitation on
Wednesday seems to be about 6 hours slower than the runs yesterday
which is likely attributed to the rapid cyclogenesis expected to
occur with the secondary low developing off the New England coast
Wednesday afternoon and evening.

There are still a few discrepancies relating to the track the newly
formed low will take on Wednesday and a change of just 25 miles will
have a drastic impact on the amount of rainfall we may see across
the North Country. The GFS, which is the eastern outlier once again,
keeps the main axis of moisture and frontogenetic forcing well to
our south and east as the surface low tracks east of the benchmark.
However, the new NAM. ECMWF and Canadian all show the surface low
tracking within benchmark which would put eastern and southern
Vermont in some of the strongest frontogenetic forcing which could
yield heavy banded precipitation structures. While it`s still a
little too far out to get an exact total on rainfall amounts
Wednesday and Wednesday night, it wouldn`t be surprising to see a
widespread inch to an inch and a half of rainfall with some
locations seeing upwards to 2 inches.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 328 AM EDT Monday...The steady rainfall will begin to come to
an end Thursday morning with a brief reprieve in rainfall possible
through the morning hours. However, rain showers will quickly
develop across the North Country by late morning as a decent
shortwave rotates along the western periphery of the upper level
trough. When you couple this upper level support with steepening low
level and mid level lapse rates, you get the perfect ingredients for
widespread shower activity. These showers will not be as intense as
those observed on Wednesday with the moisture axis now well offshore
with PWAT values only hovering around 0.5 to 0.6 inches.
Nevertheless, shower activity will continue through the evening
hours on Thursday before finally tapering off as we head into Friday
morning. It should be noted that the GFS has trended warmer with 850
and 925 mb temperatures Thursday afternoon and evening and has come
into better agreement with other deterministic guidance. Should this
pan out, chances for snow at higher elevations (above 2500 ft) will
be stunted with just some light accumulations possible at summit
level.

A reprieve from this wet and active pattern is expected to develop
on Friday with deep layer ridging becoming more pronounced throughout
the day. This ridging will help scour out any residual low to mid
clouds and moisture and allow for partly to mostly sunny skies to
develop by sunset. Friday will still be on the chilly side with 850
mb temperatures across the region near zero degrees C. Afternoon
high temperatures on Friday should only climb into the mid 40s to
lower 50s. This period of drier weather will continue through the
weekend with deep layer ridging continuing to reside across the east
coast. By Saturday, we will begin to see some weak warm air
advection in the low and mid levels which will help warm
temperatures back near or possibly above seasonal normals while
skies remain mostly clear. The next chance of precipitation
shouldn`t come until Monday with another frontal system expected to
impact the region.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday...Predominantly VFR conditions expected for
the 24 hr TAF period. The pressure gradient will increase
tomorrow ahead of a cold front with a slight chance of light
rain. Skies should be mostly clear until the front arrives, then
ceilings will drop to 6,000 to 10,000 ft behind the front.
Light and variable winds will increase tomorrow morning and
remain southerly increasing up to 12 kts by afternoon, gusting
up to 20 kts at BTV and MSS.

Outlook...

Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. Definite SHRA.
Wednesday Night: Mainly VFR, with areas MVFR possible. Definite
SHRA.
Thursday: Mainly IFR, with areas MVFR possible. Likely SHRA.
Thursday Night: Mainly MVFR, with local IFR possible. Chance
SHRA.
Friday: Mainly MVFR, with local VFR possible. Slight chance SHRA.

&&

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

&&

$$
SYNOPSIS...Duell
NEAR TERM...Duell
SHORT TERM...Clay
LONG TERM...Clay
AVIATION...Duell


 
 
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