Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 240247

Area Forecast Discussion
National Weather Service Burlington VT
1047 PM EDT Sun Jul 23 2017

Chances for precipitation increase tonight as an upper level
trough brings widespread rain to the region during the day
Monday and into Monday night. Showers will be heavy at times,
especially across northern New York. Total rainfall through
Monday night will range from near an inch and a half across
northern New York, to three-quarters to around inch across
Vermont. Overcast skies will yield unseasonably cool
temperatures, with Monday afternoon highs mainly in the low to
mid 60s. High pressure and warmer temperatures should return by
Wednesday. However, a frontal system will bring showers and
thunderstorms on Thursday.


As of 1044 PM EDT Sunday...Our brief reprieve of calm weather
ends overnight as an upper level low over the Great Lakes moves
ewd and brings showers back to the North Country to start the
work week. As the upper level low tracks towards the Saint
Lawrence valley, a series of low pressure systems will bring
widespread rainfall to the region. The first of those lows will
move into northern New York ushering in thicker cloud cover and
enhanced PWAT. Consensus of the guidance brings the PWATs to
1.5-1.6 across the Saint Lawrence valley with 1.2-1.4 across
Vermont which is slightly above normal based on the ALY sounding
climatology. The first showers are developing east of Lake
Ontario at 0245Z, and should shift newd into St. Lawrence County
over the next 1-2 hrs, before overspreading the remainder of the
North Country by 12Z Monday. As the showers increase in coverage
through Monday, it should be pretty much a washout across the
North Country. Temps will be seasonable cold as we`ll be 15
degrees below normal (highs mainly in the low-mid 60s).

Concerning the showers, with the above normal PWATs and
persistent rainfall, I did keep with the previous forecaster`s
idea that the rainfall will be heavy at times. As the first
surface low tracks up the Saint Lawrence it should bring a burst
of moderate rainfall overnight and then as the upper level low
tracks closer the parent low will pivot and begin to dive
southeast. This should mean that northern New York receives the
most significant rainfall as the energy from the systems will
be focused on that area for the longest period of time whereas
eastern Vermont will see slightly less total rainfall. Between
1-2 inches will fall over northern New York with between 0.5-1
inch of rain should fall over Vermont. Flooding isn`t currently
a concern because RFC flash flood guidance is nearly 2 inches in
the 1 hour and between 2-3 in the 3 hour range. There should be
enough instability and cold air aloft to support some embedded
thunder with the showers mainly over northern New York.


As of 321 PM EDT Sunday...Mid-level trough over the North
Country will continue producing showers on Tuesday into Tuesday
evening. The trough will be replaced with high pressure Tuesday
night with diminishing cloud cover allowing for possible fog
development towards early Wednesday morning. At the surface, the
ridge of high pressure will crest over the region early
Wednesday, then slide off the New England coast during the day.
Southwest flow will return, filtering in warmer air. Seasonably
cold temperatures on Tuesday with maxes generally in the 60s and
mins Tuesday night in the 50s will recover on Wednesday as
maxes reach the mid to upper 70s.


As of 321 PM EDT Sunday...Surface ridge continues to slide into
the Atlantic as frontal system approaches the North Country
from the northwest on Wednesday night. Expect this boundary to
bring showers late Wednesday night through Thursday.

At this point, models diverge on sensible weather Thursday
night into Friday, but trending to keep precipitation and
associated low further south, possibly affecting the southern
half of the forecast area. GFS and ECMWF agree on another ridge
of high pressure building in from Canada for the weekend.
Temperatures throughout the period expected to be near normal.


Through 00Z Tuesday...VFR conditions starting the period are
expected to deteriorate as a low pressure system will bring
showers to the North Country between 8-10z Monday. Ceilings
should be mostly VFR until late in the period when MVFR ceilings
will be possible most likely at SLK/MPV. OVC 2500-3000 feet
ceilings should move into the region between 13-15z tomorrow
expect for PBG where downsloping should keep ceilings as VFR.
Showers will start light after 09Z and then become more
widespread and heavier with visibility dropping to MVFR and even
briefly IFR as heavier showers pass over the region. Slight
improvement in intensity of showers and visibility will come
very late in the period for eastern TAF sights while western
sites will not see improvement until after the end of the

Winds will be southeast at less than 10 knots during the
overnight hours and then 05-10 knots with gusts up to 18 knots
Monday afternoon.


Monday Night: MVFR. Likely SHRA.
Tuesday: VFR/MVFR. Chance SHRA.
Tuesday Night: VFR. Patchy FG.
Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. Slight Chance SHRA.
Thursday: VFR. Likely SHRA...Slight Chance TSRA.
Thursday Night: VFR. Chance SHRA.
Friday: VFR. Chance SHRA.




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