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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 230801
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
401 AM EDT Sun Jul 23 2017

.SYNOPSIS...
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A dry and seasonably cool day is expected across the North
Country today to end the weekend. 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. High pressure and warmer
temperatures return for Wednesday, with showers and
thunderstorms returning on Thursday along a passing cold front.
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&&

.NEAR TERM /THROUGH MONDAY/...
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As of 400 AM EDT Sunday...Surface high pressure over the region
this morning will largely remain in control providing dry
conditions to end the weekend, but a fast northwesterly flow
aloft will have clouds increasing through the day helping to
limit high temps to the mid/upper 70s. Active weather returns
tonight though, mainly after midnight, as a well advertised
upper level low currently tracking into the western Great Lakes
slowly shifts east to the St. Lawrence Valley and northern New
York by the end of Monday. Increasing southwesterly flow aloft
will usher in some modest PWATs, climbing to near 1.5" across
northern New York and 1.25" eastward with precipitation becoming
widespread through Monday as surface low pressure takes shape
over the eastern Great Lakes. It will be a damp and raw day with
temps only topping out in the 60s. Instability is rather meager
at the surface which will limit thunderstorm potential, but
steeper mid-level lapse rates of +6-7C/km support the idea some
embedded thunder so have kept in a slight chance of that.
Otherwise, the main threat during the period will be the
potential for bouts of heavy rain, mainly across northern New
York where rain/storms look to pivot during Monday morning as
the mid/upper level circulation slows/stalls across the St.
Lawrence Valley. Rainfall here through Monday will look to be in
excess of 1 inch and potentially close to 2", but the good news
is that 3-6 hour flash flood guidance is in the 2-3" range, so
while area rivers will see modest rises, no flooding is
expected. Eastward, QPF will be in the 0.50-0.75" range.
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&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
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As of 400 AM EDT Sunday...Widespread showers then continue
Monday night before tapering off through the daylight hours on
Tuesday as shortwave energy and accompanying longwave trough
pivot through the area. Good upper dynamical support warrants
pops on the higher end (60-90%) Monday night when best coverage
will occur. Patchy fog also a good bet, especially in favored
locales though I really can`t rule it out anywhere. The thunder
threat will remain rather minimal, mainly confined to our
southwestern-most counties in the evening hours where some weak
mid-level instability will linger. Additional rainfall totals
generally in the 0.25 to 0.50 inch range through this period.
Temperatures hold seasonably cool with lows in the 50s and
corresponding highs on Tuesday in the 60s to locally near 70 in
the SLV where some partial late day sun will be possible.
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&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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As of 400 AM EDT Sunday...Pretty much a persistence forecast
will be offered for the middle to later portions of the work
week with this morning`s global output maintaining good
consensus by and large. A general drying trend will occur by
Tuesday night into Wednesday as expansive surface high pressure
builds east from the Great Lakes and Ohio Valley as 500mb
heights slowly build. With a return of partial to full sunshine,
temperatures respond in kind by returning to near late July
seasonal norms with highs in the 70s to around 80 and overnight
lows in the 50s to lower 60s. Patchy fog a good bet once again
Wednesday night with partially clear skies and moist ground from
early week rainfall.

By Thursday into Thursday evening data continues to support a
weak cold front sweeping through the area with scattered to
numerous showers and thunderstorms. While a widespread severe
weather threat appears rather minimal at this point, a favorable
afternoon frontal passage combined with modest boundary layer
instability and shear would seem to promote at least a few
stronger cells. Time will tell.

Behind this feature the picture becomes a little unclear as we
progress toward next weekend. This morning`s ECMWF has abandoned
the wild, deep closed low scenario offered by its 07/22 12Z run
showing a somewhat more progressive flow across the
northeastern quarter of the nation. The GFS shows a somewhat
murkier solution showing the frontal system becoming bogged down
to our immediate south, eventually becoming entangled with
several weak coastal waves and keeping a modest shower threat
across the eastern and southern portions of the forecast area.
At this point will maintain a blended solution showing at least
a lingering threat of showers in these areas into Saturday,
though admittedly this is a low confidence forecast at this
point. Temperatures hold near seasonal norms with highs in the
70s to near 80 and lows in the 55 to 65 range.
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&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Through 06Z Monday...Overall VFR conditions are expected
through the next 24 hours with FEW-SCT mid clouds currently
over the region increasing to BKN-OVC through the day and
slightly lowering. Only exception is at KSLK where a brief
period of MVFR BR is likely through about 09Z with possible IFR.
Winds will be light north/northeast less than 10 knots through
the period, except locally southeast at KRUT during the
overnight hours.

Outlook...

Monday: MVFR. Likely RA. Areas +RA.
Monday Night: MVFR. Chance SHRA.
Tuesday: VFR/MVFR. Chance SHRA.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Likely SHRA...Chance TSRA.

&&

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

&&

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