Area Forecast Discussion
Issued by NWS Burlington, VT

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821
FXUS61 KBTV 270823
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
423 AM EDT Tue Jun 27 2017

.SYNOPSIS...
Showers will becoming rather widespread during the late morning
and afternoon hours across the entire area. In addition...the
potential for thunderstorms will exist and gusty winds and small
hail will be possible with any of the storms. The showers and
storms end tonight and much of the area will be dry on Wednesday
with just the possibility of some showers up along the
international border. Below normal temperatures will continue
through midweek...but a warmer and wetter pattern sets up for
the rest of the week and into the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 423 AM EDT Tuesday...Dry weather will only last through
about mid-morning as well defined shortwave trough moving out of
the eastern Great Lakes early this morning is enhancing
convection over western New York state. This feature moves
across our area during the late morning and afternoon hours and
increase dynamic support across the region for greater areal
coverage of showers and isolated storms across our area. Going
forecast of convection ramping up into the likely category looks
real good. Colder core aloft associated with the shortwave
trough will steepen lapse rates over the area and despite cooler
temperatures today...sufficient instability will develop with
CAPE values in the 200-500 J/kg range. Low wet bulb zero values
and layer of drier air in the sub-cloud region both point to
gusty winds and small hail with any of the stronger convection.
Going forecast already has this in and will continue to
maintain. In addition...will issue a Special Weather Statement
to highlight the threat of stronger storms.

The showers will end across northern New York in the early
evening hours and then across Vermont by midnight. Surface high
pressure builds into the region behind the departing upper
trough tonight and Wednesday. Any forcing will remain north of
the border on Wednesday and thus most of the area should remain
dry. Could see a few showers up along the international border
Wednesday afternoon. High temperatures will actually be a few
degrees warmer than today with highs in the upper 60s to lower
70s...which is a few degrees cooler than normal for this time of
year.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 423 AM EDT Tuesday...Any Wednesday afternoon convection
dissipates going into the evening and overnight hours with the
loss of surface heating and a weak ridge of surface high
pressure building over the region. As such, it should be a
relatively quiet night, and likely the last of the week with
active weather quickly returning Thursday as low pressure moving
through the Great Lakes will push a west/east oriented warm
front over the region. Showers develop along the boundary across
northern New York during the morning, and become widespread
across the entire forecast area through the afternoon and into
Thursday night. Tricky forecast in regards to thunderstorm
potential as surface instability is quite weak Thursday morning
to mid-day when 0- 6km shear is the strongest (60-70kts), but as
the warm front begins to slowly lift northward during the late-
day and overnight hours instability actually increases while the
shear decreases. As such, feel thunderstorm potential will be
greatest across central/southern areas during the late afternoon
to around midnight, with coverage decreasing towards daybreak
Friday as the North Country becomes entrenched in the warm
sector.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 423 AM EDT Tuesday...By Friday morning the aforementioned
warm front will be lingering around the international border
with the majority of the North Country firmly in the warm
sector. Over the next 24-48 hours several waves of low pressure
riding along a cold frontal boundary to our west will provide
ample instability for showers and thunderstorms along with
additional moisture and PWATs surging to 1.5-2". While the exact
timing of each individual wave is difficult at this time,
confidence is growing high that periods of heavy rain from
Friday afternoon through Saturday night are likely with
additional rainfall amounts in the 1-2" range on top of the 1"
we`re likely to see on Thursday. Considering how wet area soils
are already, this could be the tipping point to realize flash
flood potential and bears watching through the week.

Sunday remains showery, especially across northern areas as the
parent upper trough and surface cold front look to swings through
the region, with quieter and drier conditions expected Monday post
fropa.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Through 06Z Wednesday...Showers will be exiting Vermont by about
09z this morning and clear skies over northern New York should
move into Vermont as well. Moisture from the evening and early
morning rainfall combined with the clear skies and light winds
will produce a period of IFR to VLIFR conditions at a number of
locations due to the development of fogs and low clouds. These
lower conditions will last until about 12z before low level flow
increases and promotes mixing. An upper level trough of low
pressure moves into the region later this morning and afternoon
and widespread showers are expected between 16z and 22z.
Conditions will mainly be VFR...but may lower into the MVFR
category during this period due to the showers. The potential
will exist for thunderstorms and any of the storms will have the
potential to produce gusty winds and small hail. The
precipitation comes to an end around 00z and VFR conditions are
expected for the remainder of the period.

Outlook...

Tuesday Night: VFR.
Wednesday: VFR. Slight Chance SHRA.
Wednesday Night: VFR. Slight Chance SHRA.
Thursday: VFR/MVFR. Likely SHRA.
Thursday Night: VFR/MVFR. Likely SHRA...Slight Chance TSRA.
Friday: VFR. Chance SHRA...Chance TSRA.
Friday Night: VFR. Chance SHRA...Chance TSRA.
Saturday: VFR/MVFR. Likely SHRA...Likely TSRA.

&&

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

&&

$$
SYNOPSIS...Evenson
NEAR TERM...Evenson
SHORT TERM...Lahiff
LONG TERM...Lahiff
AVIATION...Evenson



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