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FXUS61 KBTV 261730
Area Forecast Discussion
National Weather Service Burlington VT
130 PM EDT Wed Sep 26 2017
Strong high pressure at the surface and aloft will continue to
provide unseasonably warm, record setting temperatures for the
region today through Wednesday. A cold front will move across
northern New York and upstate Vermont Wednesday night with some
isolated to scattered showers and isolated thunderstorms. A much
cooler air mass will return, and seasonable weather is expected
behind this front from Thursday through the upcoming weekend.
As of 130 PM EDT Wednesday...Another hot, record breaking day is
expected with H850 temps still running a few standard deviations
above normal according to the latest 00Z GEFS with actual H850 temps
in the +18C to +19C range. High temps should be fairly similar to
yesterday and maybe a degree or two cooler with a few- sct cumulus
and the scattered cirrus around. Overall, mostly sunny conditions
should be prevail with the cumulus mainly along the western spine of
the central and northern Greens and over the Adirondacks. Highs will
be in the upper 80s to lower 90s in the valleys especially the St
Lawrence and Champlain Valleys and 70s to mid 80s over the elevated
terrain. Sfc dewpts will still be in the 60s and it will be very
humid outside. We will re-run the SPS with the heat indices in the
lower 90s. They fall just short of the 2nd day with heat indices in
the mid 90s for a possible advisory for n-cntrl VT. Please see the
climo section below with the records that may be broken.
Expecting a similar night to this morning with the sfc high
weakening, and the mid level ridging flattening aloft.  Some locally
patchy dense fog may form in the valleys.  We are expecting some
high clouds to move in from the west ahead of the cold front over
the eastern Great Lakes Region and southeast Canada towards
daybreak. Lows will be in the mid 50s to mid 60s.  It will be the
last mild night.
As of 130 PM EDT Wednesday...Maria drifts close to the Mid-Atlantic
Coast then starts to make the turn to the east to northeast.  Mid
and upper level heights continue to fall over upstate NY into
western New England during the day with low pressure moving into
north-central Quebec and a cold front approaching the region. The
increasing clouds should hold temps down a bit west of the Champlain
Valley with upper 70s to mid 80s in the valley areas, and upper 60s
to upper 70s over the higher terrain.  Some upper 80s are possible
in the Champlain Valley and near BTV /possibly some isolated 90F
reading/, with generally 80-85F readings in the other valley
locations, and 70s to around 80F over the mtns. Some record temps
are possible again at several sites.
There is modest convergence with the front and some small amounts of
sfc based instability in the 250-750 J/kg range based on the latest
GFS. We have placed slight to low chances of showers in the
afternoon with a slight chc of thunderstorms.
We will continue the previous BTV discussion highlighting heat
hazards below:
While these temps are considered sub advisory(<95 F), they are
not to be taken lightly especially given the time of year. Based
on the forecast and current records, its expected that records will
fall at many sites by 2-5 degrees. Prolonged exposure outside
combined with strenuous activity can lead to heat related injuries.
Please take caution, stay hydrated and take frequent breaks during
any outdoor activities. This will be the fourth consecutive day with
90+ degree heat indexes during the afternoon.
Wednesday night into Thursday...Fairly good agreement with the
latest deterministic guidance that the front will clear the forecast
area between 06Z-12Z/THU.  We did keep a few lingering showers over
nrn-cntrl VT.  Total rainfall from this front will likely be less
than a tenth of an inch unless some convection occurs. Cold
advection occurs in the wake of the front with H850 temps falling to
+2C to +10C from the St Lawrence River Valley southeast across
central VT.  Lows will fall into the 40s to lower 50s.  Cool and
breezy conditions are expected on THU with sunshine mixing with
clouds, as a sfc high noses in from the southeast Ontario.  Highs
will trend back to normal readings with mid 60s to around 70F in the
valley areas, and 50s to lower 60s over the higher terrain.
Thu night...A short-wave moving through the upper level trough over
s-central Canada, the Great Lakes Region and into the Northeast will
approach the forecast area.  Mostly clear conditions early will give
way to increasing clouds especially over northern NY.  The short-
wave and its associated cold front looks to impact portions of the
local area on Fri.  It should remain dry THU night with lows in the
30s to around 40F. There could be some patchy frost with lower to
mid 30s in the northern Adirondacks.
As of 130 PM EDT Wednesday...Persistence was used predominately in the
long term with the one change being the short-wave diving south and
east of the region during the day.  The limited low-level moisture
will hold the chances of showers mainly in the slight chance
category on Friday mainly west of the Champlain Valley. From the
Champlain Valley eastward we have kept it dry.
A slight chc of showers was kept in Fri night into Saturday with the
mid and upper level trough passage, but overall this could end of
dry again which has been the trend the past few weeks.  A large
ridge of high pressure builds in late Saturday into Monday with fair
and dry weather with seasonable temps.  Some patchy frost may be
possible in the sheltered valleys within the higher terrain on the
Through 18Z Wednesday...VFR through the period except late night/early
morning IFR/LIFR in br/fog at KMPV/KSLK from 06-13Z Wed. Winds light
and variable through 12Z Wednesday, then south/southwesterly 5 to 10
knots thereafter.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Slight Chance SHRA.
Thursday Night: VFR. NO SIG WX.
Friday-Friday Night: VFR. Chance SHRA.
Saturday-Sunday: VFR NO SIG WX.
Record high temperatures and year recorded for the period Tuesday
Sep 26 to Wednesday Sep 27
Day    Burlington    Massena      Montpelier
9/26   84 / 1934     82 / 1970    83 / 2007
9/27   83 / 1920     82 / 2003    80 / 2007
For Burlington, here are the latest in the year dates for reaching
specific temperature thresholds
90F or higher:  9/16/1939
88F or higher:  9/22/1965
87F or higher:  9/23/1895
86F or higher:  9/23/1895 (was 87F that day)
Day   Burlington   Massena   Montpelier   St Johnsbury
9/23                 86
9/24     91          88         85          89* (Tied)
9/25     92          91         88          91

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