-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 232008
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
408 PM EDT Fri Jun 23 2017

.SYNOPSIS...
Numerous showers with scattered thunderstorms, some with heavy
rainfall will continue across the area this evening before
tapering off overnight. After a mainly dry Saturday a generally
unsettled weather pattern returns for much of next week with
daily chances for showers and a few storms. Temperatures remain
near seasonal norms for early summer.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 245 PM EDT Friday...Flash Flood Watch remains in effect
for the Adirondacks into portions of northern VT through 11 pm.
Latest analysis showing deep and moist southwesterly flow
continues across the area this afternoon ahead of a slowly
advancing surface front across the eastern Great Lakes south
into the Ohio Valley. In this airmass scattered to numerous
showers and a few heavier thunderstorms will continue into this
evening before the front clears east and precipitation tapers
off overnight. Given near saturated soils and antecedent 1-2
inch rainfall in the Flash Flood Watch area it won`t take much
to cause hydro issues. Threat is conditional at this point with
most recent CAM QPF output quite varied in convective evolution
over the next 3 to 6 hours. Problematic is a lack of steeper
lapse rates aloft to foster more robust vertical cloud growth.
That said, we remain in a 1.8 to 2.0 PWAT airmass so efficient
rainfall processes will occur with locally heavy downpours a
near sure bet. By later tonight areas of mist/patchy fog likely
under variably cloudy skies. Stuck close to blended temperature
guidance offering lows in the 60s.

By Saturday into Saturday night a brief period of drying can be
expected for most areas as we lie between shortwave troughs on the
southern edge of a dominant polar trough across central Canada.
Additional weak low level troughing settling south toward the intl
border during the afternoon may spark scattered showers/isolated
storms across the far north, but most of the day should be rain-free
for most areas. Highs similar to today (upper 70s to lower 80s),
though humidity will be more tolerable as dewpoints lower back into
the 50s over time. Lows Saturday night in the 50s to locally near 60
in milder valley locales.

&&

.SHORT TERM /SUNDAY/...
-- Changed Discussion --
As of 359 PM EDT Friday...Broad upper level trof and weak
surface wave moving to the north of the international border
will provide a chance for shower and a few thunderstorms once
again on Sunday. Have increased rain chances over previous
forecast based on the preponderance of available guidance.
Instability is marginal, but sufficient for at least isolated
thunder.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
-- Changed Discussion --
As of 359 PM EDT Friday...Great Lakes and northeast will
continue to be under the influence of a broad upper level
trough of low pressure through the middle of the week before
more zonal flow returns to ther region. Weak shortwaves will
rotate around the trough providing the chance for showers and
storms. Despite the flattening flow at the end of the week, a
weak boundary laid out just north of the area will continue to
provide convective chances at the end of the work week.
-- End Changed Discussion --

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Through 18Z Saturday...Changeable conditions through the period
with a mix of VFR/MVFR/IFR expected. Numerous showers/sct
thunderstorms producing locally heavy downpours to continue
through this evening. Heavier precipitation cores to drop vsbys
to MVFR/IFR with MVFR cigs and low probabilities of gusty
winds. Later tonight steadier showers/isolated storms gradually
end west to east with passage of cold front. Vsbys generally
lower in the 4-6sm range with patchy br/fg and MVFR/IFR stratus
in the 02-12Z time frame. After 12Z conds improve to VFR. Winds
generally light south to southwesterly 6-12 kts through the
period.

Outlook...

Saturday: VFR. Slight Chance SHRA/TSRA...mainly north
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. Breezy. Chance SHRA.
Sunday Night: VFR. Breezy. Chance SHRA.
Monday: VFR. Chance SHRA.
Monday Night: VFR. Chance SHRA.
Tuesday: VFR. Chance SHRA.

&&

.HYDROLOGY...
As of 1030 AM EDT Friday...Storms will have high rainfall rates
today, and training storms moving over same location could
produce areas of flash flooding in the Flash Flood Watch area,
where 0.75 to locally 2 inches of precipitation fell earlier
today. With the overnight rains, 1 hour FFG has decreased into
the 1.0 to 1.5 inch range, with 3-hourly guidance running from
1.5 to around 2 inches. With the lack of an organized forcing
mechanism for storms this afternoon heavy rainfall will be hit
or miss, but latest output suggests instability on the south
side of warm front to our immediate north may drive additional
activity into the watch area. Per coordination with NERFC
additional amounts of 1 to 2 inches is forecast, which raises
concerns for smaller watersheds. Larger rivers and will see
modest rises but should remain within banks.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Flash Flood Watch until 11 PM EDT this evening for VTZ005>010-
     017-018.
NY...Flash Flood Watch until 11 PM EDT this evening for NYZ028>031-
     034-035.

&&

$$
SYNOPSIS...JMG
NEAR TERM...JMG
SHORT TERM...Manning
LONG TERM...Manning
AVIATION...JMG
HYDROLOGY...JMG/Hanson