Area Forecast Discussion
Issued by NWS Burlington, VT

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000
FXUS61 KBTV 200035
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
735 PM EST Mon Feb 19 2018

.SYNOPSIS...
Periods of showers and steadier rainfall will develop later
tonight 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 the weekend.

&&

.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
As of 644 PM EST Monday...No significant changes from previous
forecast. First off, not expecting any hydro/flooding issues
overnight...with any significant river rises not beginning
until the daylight hrs Tuesday.

Looking for a mild night with temperatures steady in the upr
30s to lower 40s...and generally slowly rising toward daybreak
on continued southerly winds. Synoptic warm front has lifted
north of the intl border, but it appears secondary warm front
and E-W boundary with richer moisture across nern OH, srn tier
of NY into srn VT, will continue to provide the primary focus
for periods of light to moderate rainfall overnight. Generally
expecting precipitation to focus northward across the St.
Lawrence Valley, nrn Adirondacks, and n-central VT toward
daybreak on Tuesday as 925mb theta-e gradient shifts nwd.
Rainfall amts will generally range from 0.1-0.25" overnight,
except locally 0.50" or so across St. Lawrence and Franklin NY
counties. With dewpoints pushing above freezing, will see patchy
fog develop, mainly in sheltered locations with continued low-
level mixing with south winds 10-15mph in more open valleys.

&&

.SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
As of 500 PM EST Monday...Lots of interesting aspects to the
forecast from Tuesday through Wednesday night. I`ll try to touch
on all of them in this discussion. Very warm system impacting
the region with a surface front stationary to our Northwest just
across the International border. This will be the focus for
several waves of energy and precipitation over the 48 hour
forecast period. Record breaking maximum temperatures are
forecast for Tuesday and Wednesday. Dewpoints will also be
surging into the 50s. Temperatures and dewpoints result in
thawing degree hours off the charts, we expect much of the snow
to melt across the region. On top of this, a quarter of an inch
to an inch and three quarters of rain is forecasted, highest in
the Saint Lawrence valley and lowest in Southeastern Vermont.
Losing much of our snowpack will release 3 to 7 inches of snow
water equivalent into the river basins. The rainfall and
snowmelt together have led to high confidence that we will have
flooding across much of the area. The northern Adirondacks and
Northern portion of the Vermont, as well as the Saint Lawrence
valley have the highest chances for flooding. Also, any
locations that still have ice jams in place from the January
event will be especially susceptible to flooding. Temperatures
on Tuesday, firmly in the warm sector, will surge into the 50s,
dewpoints will be approaching the 50s as well. Unprecedented wet
system with pwats surging to about 1.4 which is also near
record breaking for Feb. Thawing degree hours have already
started to accumulate, and will continue until sometime Wed
night. Thawing degree hours reach 850-1200 which is huge,
passing the 300 mark sometime Tuesday afternoon across our
Western zones, and Tuesday night across the entire area. This is
when I`d expect problems to start cropping up on the rivers as
far as ice movement goes. Once again temperatures will not fall
too far Tuesday night, lows in the upper 40s to lower 50s. Max
temperatures on Wednesday will be even warmer, widespread 60s.
Cold front will finally start moving and cross our area
Wednesday night, by the time the cold front moves across the
region, precipitation should have ended therefore not expecting
much snow on the backside of this system. There may be a brief
break in the precipitation Wednesday morning as the front
briefly drifts even further north from the border.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 405 PM EST Monday...Cooler but still warmer than normal
conditions will prevail through early next week. The region will
also remain in an active pattern as fast zonal flow dominates
aloft. High pressure will keep the weather dry Thursday and
Thursday night. Then the first in a series of low pressure
systems will bring a mix of rain and snow to the region Friday
into Friday night, followed by another later Saturday into
Saturday night. The third rain/snow system arrives Sunday into
Monday. Although there are still differences in the tracks of
each of these lows, overall it looks like temperatures will be
cold enough for snow at night, while daytime highs will allow
most areas to change over to rain.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...Warm frontal zone weather with mix of
VFR/MVFR ceilings across the North Country early this evening...
generally lowering into the MVFR category areawide after 03Z,
with HIR TRRN OBSCD. Will see periods of light/moderate rain and
BR thru the period, and localized IFR ceilings are expected to
develop at SLK after 03Z this evening. Winds will remain from
the south, with gusts locally to 25kt at BTV through 06Z with
valley channeling. Local valley channeling will also keep MSS
locally NE winds at 5-10kts. Winds slacken somewhat toward
daybreak, and will see some Low-Level Wind Shear (LLWS) issues
at SLK/MSS/RUT after 08Z, as winds near 2000ft strengthen to
40-50kts.

Outlook...

Tuesday Night: VFR/MVFR conditions possible. Chance SHRA.
Wednesday: Mainly MVFR, with areas VFR possible. Chance SHRA.
Wednesday Night: VFR. Chance SHRA, Chance SHSN.
Thursday: VFR. Slight chance SHRA, Slight chance SHSN.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. Chance SHRA, Chance SHSN.
Friday Night: MVFR/IFR conditions possible. Likely SN.
Saturday: Mainly MVFR, with local IFR possible. Scattered SHRA,
Scattered SHSN.

&&

.HYDROLOGY...
As of 400 PM EST Monday...A 48-hour period of anomalously warm
temperatures will affect the region 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 Tuesday
afternoon 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 1 AM EST Tuesday through Wednesday evening
     for VTZ001>012-016>019.
NY...Flood Watch from 1 AM EST Tuesday through Wednesday evening
     for NYZ026>031-034-035-087.

&&

$$
SYNOPSIS...Neiles
NEAR TERM...Banacos/Neiles
SHORT TERM...Neiles
LONG TERM...Hastings
AVIATION...Banacos
HYDROLOGY...TEAM BTV
CLIMATE...TEAM BTV


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