Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 231921

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

Chances for precipitation increase tonight though as an upper
level trough will bring widespread rain to the region late
tonight through Tuesday along with much cooler temperatures. The
showers will be heavy at times over northern New York. High
pressure and warmer temperatures should return by Wednesday
however a frontal system will bring showers and thunderstorms
on Thursday.


As of 219 PM EDT Sunday...Our brief reprieve of calm weather
ends this evening as an upper level low over the Great Lakes
will bring 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 which happens this evening ushers 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. As the showers increase through
the 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.

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 18Z Monday...Overall VFR conditions 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. Winds will be light
north/northeast less than 10 knots shifting to southeast during
the overnight hours tonight.


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




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