FXUS61 KBTV 252339
Area Forecast Discussion
National Weather Service Burlington VT
739 PM EDT Sat Jun 25 2016
High pressure to remain in control of the weather across the North
Country through Sunday evening. Abundant sunshine, warm
temperatures in the mid 80s to low 90s and low humidity levels
should be the rule. Next chances for showers and thunderstorms is
on Monday continuing into Tuesday. Temperatures then trend near to
below normal for the middle to latter part of the week.
.NEAR TERM /THROUGH SUNDAY/...
As of 738 PM EDT Saturday...Going forecast in great shape and no
real changes needed at this time. Shallow cumulus over the
mountains continues to decrease in areal coverage and later
tonight it looks like we could see some mid and high level
convective debris clouds from the Upper Midwest roll into our
area, which going forecast has covered well. Otherwise...temperatures
should plummet pretty quickly everywhere but then start to level
off after midnight especially in the Champlain and St. Lawrence
Valley areas. Thus, I`d expect to see a significant variation in
low temperatures from the mid/upper 40s in the Adirondacks to the
lower to mid 60s in the Champlain Valley, with 50s pretty common
east of the Greens. All are about 1-2 degrees warmer than 12z MOS
and recent GFS LAMP guidance.
On Sunday...ridge of high pressure remains in control with
similar sensible weather conditions to today. The only difference
will be an increase in south winds (occasional gusts to 20-25 mph
in the Champlain Valley) and a slight uptick in dewpoints (upper
50s to low 60s). 925 mb temperatures increase to +21 to +23C which
under mostly clear to filtered sun supports highs into the 80s to
low 90s, cooler along Lake Champlain. Still generally comfortable
perceived humidity levels with afternoon RH values around 30%.
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 305 PM EDT Saturday...Mid/upper level ridge across the
eastern CONUS will slowly breakdown as a series of short waves and
associated 5h trof approach the region. The first pre-frontal trof
and embedded 5h vort in the southwest flow aloft arrives by 12z
Saint Lawrence Valley and moves from west to east across our cwa
on Monday. Dynamics are weakening with this system and axis of
enhanced 850 to 500mb moisture is very narrow...resulting in a 1
to 3 hour window for mainly showers on Monday. Have noted SPC
place our northern NY in marginal outlook...but best instability
occurs after dynamics and ribbon of mid level moisture shifts to
the east of greatest instability and deep layer shear. Based on
limited instability and timing will mention showers with isolated
thunder on Monday...with highest pops/qpf across northern NY.
Thinking initial band of showers will enhance low level moisture
and result in greater instability parameter across Saint Lawrence
Valley after 18z Monday...but soundings are very dry and upstream
forcing is very weak. A mild night is expected Sunday Night with
developing southerly flow ahead of pre-frontal trough with
readings mainly in the 60s to near 70f Champlain Valley. Highs on
Monday afternoon in the 80s....with increasing surface dwpt values
from expected rain showers will produce some higher humidity
values. Another warm and muggy night is expected on monday with
lows mainly in the 60s to near 70f again.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 305 PM EDT Saturday...Still anticipating an active day on
Tuesday with widespread showers and thunderstorms...with some
uncertainty on the degree of instability. Synoptic scale shows
strong mid/upper level trof across the northern Great Lakes
approaching the Saint Lawrence Valley by 12z Tuesday with a
surface cold front draped over northern NY. The forecast challenge
will be how much surface heating and instability can develop
before clouds and showers develop. Model progs show surface based
CAPE values between 700-1000 J/kg with most unstable values
associated with warmer surface temperatures/higher dwpts between
1000 and 1500 J/kg from the Dacks eastward. Given the available
upper level forcing...a ribbon of 700 to 500mb winds of 35 to 45
knots...creating deep layer 0 to 6 km shear values around 40
knots...some robust updrafts will support scattered stronger
thunderstorms. The best interaction of instability and shear looks
to occur over central and eastern VT...given expected position of
boundary and location of right rear quad of 75 knot jet at 250mb.
The primary focus would be gusty winds and small hail...if current
progged stability and shear profiles verify. Will continue to
mention likely to cat pops central and eastern cwa with scattered
convection...but not mention enhanced wording due to uncertainty
associated with instability. Still plenty of time to determine
areal coverage of clouds and associated impacts on surface heating
and instability along with timing of boundary.
Wednesday...mid/upper level trof axis swings across our region with
associated cool pocket aloft. This energy and leftover moisture will
produce additional scattered showers on Weds...with highest pops
across the mountains. Thermal profiles support slightly below normal
temperatures with readings mainly in the mid/upper 60s mountains to
mid/upper 70s warmer valleys with progged 850mb temps around 11c.
Thursday through Saturday...fast zonal flow aloft with general
mid/upper level trof will continue with weak short wave ridge by
Friday. This supports a dry forecast on Friday with near normal
temps. Latest trends show the potential for a few lingering leftover
showers on Thursday with trof. Another front along with energy aloft
is expected to impact our region on Friday night into Saturday with
additional showers. Plenty of uncertainty on timing and magnitude of
system...so will just mention chance pops at this time.
.AVIATION /00Z Sunday THROUGH Thursday/...
Through 00Z Monday...VFR through the TAF forecast period. High
pressure remains in control producing a few cirrus clouds through
the period. Winds light/variable and largely influenced by
terrain effects through evening. By Sunday midday, should see
more of a southerly component to the winds which will then
increase to 6-9 kts with occasional gusts to 20 kts Sunday
Outlook 18Z Sunday through Thursday...
00Z Monday through 12Z Monday...VFR under high pressure.
12Z Monday through 00Z Wednesday...VFR deteriorating to MVFR/brief
IFR as a cold front brings showers and t-storms. Couple storms may
become strong Monday or Tuesday afternoon.
00z Wednesday through Thursday...VFR with nightly occurrence of
IFR/LIFR radiation fog at MPV and SLK.