Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 190750
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
250 AM EST Mon Feb 19 2018

.SYNOPSIS...
Periods of showers and steadier rainfall will develop later
today into Wednesday as a strong warm front lifts through the
area. Unseasonable, near record breaking warmth is expected for
Tuesday and especially on Wednesday fostering river ice breakup
and potential flooding concerns. Temperatures trend cooler by
Thursday onward into next weekend, though remain well above late
February norms. Additional precipitation will move into the
area by next weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 250 AM EST Monday...Quiet weather is expected through the
first half of the day as building western Atlantic ridge
evolves off to our east. Increasing south/southwest flow is
expected over time with gusts topping out in the 10 to 20 mph
range by afternoon. Higher gusts from 25 to 35 mph are expected
in the Champlain Valley as low level channeling effects take
shape in the 975-925 mb level. As the afternoon progresses a
warm front and associated deeper moisture advect quickly north
and east into the forecast area with an increasing threat of
showers and/or periods of light rain, especially south and west.
High temperatures a blend of available guidance supporting
seasonably mild values in the upper 30s to lower 40s east and
lower to mid 40s from the Champlain Valley west.

By tonight into Tuesday the start of another, near-record breaking
period of warmth surges into the area under strengthening
southwesterly flow aloft. An unusually strong Bermuda-like
subtropical high with 500 mb heights to in excess of 590dm will be
the driving force during this period. The warm front will pivot
northward to a position near or just north of the international
border during this time with periods of showers and/or steadier
rainfall expected across central and northern counties in proximity
to better lift along the frontal zone. Temperatures take on a
classic non-diurnal trend tonight as values trend steady or slowly
rise under continued light to modest south/southwest flow. By
sunrise Tuesday readings should range from the upper 30s to lower
40s across eastern VT, and in the 40s further west. By Tuesday
afternoon readings should climb solidly into the 50s for most spots
with a few spot 60f readings possible south where some partial
sunshine is expected. Dewpoints will also climb considerably during
this time (into the 40s), fostering a 24-36 hour period of rapid
snowmelt as condensation processes begin in earnest on the snowpack.
See climate and hydrology sections below for specific details.

&&

.SHORT TERM /TUESDAY NIGHT/...
As of 420 PM EST Sunday...The warm front will remain poised to
our north Tuesday and Tuesday night with waves of low pressure
traversing along the boundary. Moisture will increase through
the day Tuesday as PWATs approach 1.50 inches. These factors
will result in periods of rain through the period, with the
steadiest precipitation falling over far northern VT, the
northern Adirondacks, and the Saint Lawrence Valley.
Temperatures will be quite mild Tuesday, in the lower to mid 50s
for most, but still a bit short of daily record highs.
Dewpoints will rise through the 40s, exacerbating snowmelt from
the warm temperatures. After a brief drop in the evening,
temperatures may actually rise back into the mid 50s overnight
Tuesday night, particularly for areas west of the Greens. As
such, record warm low temperatures may be set.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 420 PM EST Sunday...Very mild conditions expected on
Wednesday as temperatures sky rocket into the upper 50s to lower
60s. Some locations in the southern Champlain Valley and lower
Connecticut River valley could actually approach 70, especially
if they see any breaks in the cloud cover. Daily record highs
will be threatened in many locations; see the Climate section
below. The warm front will begin to slowly move south as a cold
front late in the day, slowly shifting the rain back toward
central portions of our forecast area. There are still some
timing differences in exactly when the front will make its
southward push, but cooler and drier air will follow in its
wake, bringing an end to the rain, perhaps changing to snow
late. Did note that the GFS is slower with the frontal passage,
which would extend the precipitation into Thursday morning.
Rainfall amounts through Wednesday evening will mainly be in the
0.50 to 1.50 inch range across the northern areas of our
forecast area, while central and southern Vermont will get less
than a half inch. Runoff from snowmelt and rainfall will
continue through at least part of the night, so area waterways
will need to be watched even once temperatures drop back below
freezing.

For Thursday through Sunday...looking cooler and fairly active
as the northeastern CONUS remains under fast zonal flow with low
pressure systems progged to move through every day or two.
While temperatures will be cooler than what we`ll see in the
middle of the week, they`ll still be above normal, generally in
the mid 30s to mid 40s during the day, overnight lows in the
teens and 20s. There`s little model agreement on whether
precipitation will fall as rain or snow...so have stayed close
to a model blend on temperatures which resulted in a lot of
rain/snow mix through the end of the week.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Through 06Z Tuesday...VFR through 21Z, lowering to a mix of
mainly MVFR/VFR thereafter as periods of rain showers move into
the region from the south and west. SCT/BKN high cigs above 100
AGL expected through 18Z, trending BKN/OVC in the 035-060 AGL
range from 18-00Z, then lowering further thereafter. Some patchy
IFR possible at KMSS late. Winds south/southwesterly and
increasing to between 8-15 kts this afternoon into tonight.
Exceptions at KBTV and KPBG where low level southerly jet will
push speeds into the 14-20 kt range with gusts to 30 kt
in the 14-00Z time frame. As the stronger southerly flow moves
in aloft some brief LLWS to 40 kt possible at KSLK in the 09-13Z
time frame.

Outlook...

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

&&

.HYDROLOGY...
As of 250 AM EST Monday...A 48-hour period of anomalously warm
temperatures will affect the region from Monday through
Wednesday afternoon. Periods of rainfall, modest winds and
dewpoint temperatures climbing into the 40s to lower 50s will
foster rapid snowmelt and ice break-up across the entire area.
Also boosting confidence are extremely high thawing degree hour
totals - averaging 900 to 1200 over the Tuesday/Wednesday time
frame. The model consensus continues to show totals to average
from 0.5 to 1.75 inches across far northern VT into the northern
Adirondacks and SLV with the highest totals in the SLV. Lesser
amounts generally under a half an inch are expected across
central and southern VT. Taking this all into account, modest to
substantial river rises look highly probable starting Monday
night and continuing into Wednesday, supported by NAEFS/SREF
MMEFS hydrograph data. While widespread open water flooding is
not expected, several rivers may approach minor flood. More
importantly numerous ice jams remain in place from the
substantial thaw this past January, so the potential for
localized high water and/or flooding near these features remain
a real threat as ice break-up occurs.

&&

.CLIMATE...
Here are the current record high temperatures for February 20th
and 21st:

Record High Temperatures:

     ............Feb 20th....Feb 21st....
BTV.............58 (1981)...59 (1981)...
MPV.............56 (1994)...57 (1953)...
MSS.............63 (1994)...62 (1953)...
St. Johnsbury...60 (1981)...62 (1981)...

Record High-Minimum Temperatures:

     ............Feb 20th....Feb 21st....
BTV.............50 (1981)...49 (1981)...
MPV.............47 (1981)...47 (1981)...
MSS.............47 (1994)...41 (1981)...
St. Johnsbury...40 (1981)...46 (1981)...

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Flood Watch from late tonight through Wednesday evening for
     VTZ001>012-016>019.
NY...Flood Watch from late tonight through Wednesday evening for
     NYZ026>031-034-035-087.

&&

$$
SYNOPSIS...JMG
NEAR TERM...JMG
SHORT TERM...Hastings
LONG TERM...Hastings
AVIATION...JMG
HYDROLOGY...TEAM BTV
CLIMATE...TEAM BTV



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