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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 061406
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1006 AM EDT Tue Jun 6 2023

.SYNOPSIS...
Shower activity will increase in coverage today, along with some
improvement to smoky skies from the Quebec wildfires. A few
rumbles of thunder cannot be ruled out this afternoon, but no
organized storms are expected. Below normal temperatures
continue for the remainder of the work week with a gradual
warming trend into the weekend. Diurnally driven showers are
possible on most days this week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
-- Changed Discussion --
As of 955 AM EDT Tuesday...Forecast in on track for some
isolated to scattered showers developing this morning, becoming
more numerous this afternoon with increasing instability. WV
satellite imagery showing shortwave pushing into our area from
the north, which has allowed a few showers to blossom over
northern NY this morning. Still haven`t had any reports of
precipitation at the surface, so it`s likely that most or all of
the precipitation from these showers is not making it to the
surface at this point. However, as forcing increases throughout
the day with additional shortwave energy moving into the area,
do expect a few hundreths of an inch of QPF to make it to the
surface within showers. Otherwise, smoke forecast looks on track
and the Vermont Agency of Natural Resources has reissued the Air
Quality Health Advisory for all of Vermont. Do still expect some
improvement in smoke today for Vermont, but enough of a concern
remains to continue the Advisory. Further west, the Air Quality
Alert remains in effect for our NY counties through midnight.
Previous discussion follows...

According to the US EPA Air Now page, worst conditions smoke
wise for the pre dawn into the morning hours will be across
western St Lawrence Valley. Seeing some radar reflectivity
returns across our western zones but no rain has been reported
or observed by ASOS or on webcams. This could be the result of
the Quebec wildfire smoke dampening the lapse rates and
suppressing the QPF output. In fact, CAMs have been overly
aggressive with what should have been a wetting rainfall for
parts of the region so far. So continued to cap PoPs at slight
chance or low chance (30 percent) for the remainder of overnight
hours. In addition, there could be areas of localized fog
across the Northeast Kingdom during the pre dawn hours where the
dew point depressions are a couple of degrees or less along
with near calm conditions.

For today, the main weather concern remains areas of smoke from the
Quebec wildfires. The good news is that as showers become more
widespread during the course of the day, hi-res guidance is showing
near-surface smoke diminishing from the northeast to the southwest.
This coincides with improved dynamics for more widespread rainfall
coverage due to the phasing of a shortwave trough energy from the
northwest along with the vertically stacked low pressure system
along coastal New England. So have PoPs increasing during the
daytime hours. And as PoPs reach the likely to low-end categorical
threshold, the mention of smoke in the weather grids also goes away.
We shall see how that unfolds, since the smoke has helped suppress
rainfall so far, presumably due to the dampening of the atmospheric
lapse rates. It is worth noting that this is rather unchartered
territory for many NWS forecasters across the Northeast WFOs having
to deal with wildfire smoke for the first time in their forecasting
career. In other words, we are learning and adapting as the event
unfolds.

Models do show some weak instability developing in response to
height falls aloft and some decent lapse rates during the
afternoons. This may yield a few rumbles of thunder but it seems
more likely this instability will be more useful in increasing the
coverage of showers across the region. Like today, we will have to
watch how the smoke impacts the skies as it could be a wild card and
limit some much needed rainfall.

On and off diurnally driven showers continue into Wednesday thanks
to anomalously cold temperatures aloft that are more typical for
early April according to the SPC sounding climatology. Wednesday
will be another unseasonably cool day with highs 10 to 15 degrees
below normal. Thunder potential is non zero but confidence is too
low to include in the forecast. As with cold core upper level low
pressure regimes, there will be good low-level and mid-level lapse
rates but little instability to tap into.

A tenth to quarter inch of rainfall is possible, which together with
the rainfall on Tuesday be the first widespread wetting rainfall
since May 24th. Much of VT is currently under the D0 abnormally dry
category according to the U.S. Drought Monitor so the rain will be
welcome. It does make for a rather dreary day though with daytime
highs only in the mid 50s to low 60s. For reference, typical highs
this time of the year are in the low to mid 70s. Some of the
deterministic guidance Wildfire smoke from Quebec may continue to
impact the region on Wednesday but details will have to be fine
tuned in the next 24 hours as it remains outside of the HRRR/RAP
guidance at this time.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 335 AM EDT Tuesday...Persistence will be the forecast for the
end of the work week as a deep, closed upper level low over eastern
Maine and Nova Scotia Wednesday night will retrograde southwestward
over central New England through the period. The result will be
continued daily chances for showers, though with greater areal
coverage compared to previous days in the afternoons due to the
projected location of the low and steeper low level lapse rates
owing to cold upper level temps around -20C at 500mb. Showers will
generally wane each day after sunset, but overnight can`t be ruled
out completely. Temperatures will remain seasonally cool with lows
mainly in the 40s for and 60s for highs which is about 5-10 degrees
below normal for mid June.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
As of 335 AM EDT Tuesday...Heading into the weekend, it appears we`ll
have one more day under the influence of the aforementioned upper
low with scattered showers continuing on Saturday, but by Saturday
night signals continue to point towards upstream blocking briefly
breaking down allowing the system to shear out and shift north of
Newfoundland. Dry conditions should develop for Saturday night into
Sunday, but unfortunately, ensemble mean NAO forecasts indicate the
blocking redevelops and supports another upper low dropping through
the Great Lakes and closing off over the mid-Atlantic and/or
Northeast States heading into Sunday afternoon and early next week.
Time will tell exactly where this system will set up shop which will
play a large role in precip chances next week, but one thing is for
sure, the potential for any severe weather is quite low through the
period.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Through 12z Wednesday...VFR conditions expected to prevail
through the TAF period, with periods of MVFR and locally IFR
due to wildfire smoke from Quebec especially for the St Lawrence
valley terminals. More widespread showers arrive this
afternoon, which should lead to some improvement to the smoky
skies across the region. Light north to northwest winds become
gusty at 15-20 kt this afternoon. Better chance for more
widespread rain showers with 4-5 SM vsby and MVFR cigs arrive
after Tuesday 22z.

Outlook...

Tuesday Night: Mainly VFR, with areas MVFR possible. Chance SHRA.
Wednesday: Mainly MVFR, with areas VFR possible. Likely SHRA.
Wednesday Night: Mainly MVFR, with areas VFR possible. Chance
SHRA.
Thursday: Mainly MVFR, with areas VFR possible. Chance SHRA.
Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.
Friday: Mainly MVFR, with areas IFR possible. Chance SHRA.
Friday Night: Mainly MVFR, with areas VFR possible. NO SIG WX.
Saturday: Mainly VFR, with local IFR possible. Slight chance
SHRA.

&&

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

&&

$$
SYNOPSIS...Chai
NEAR TERM...Chai/Duell
SHORT TERM...Lahiff
LONG TERM...Lahiff
AVIATION...Chai