Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 231117
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
717 AM EDT Tue May 23 2017

.SYNOPSIS...
High pressure will build into the northeast U.S. today with fair
weather and moderating temperatures in the upper 60s to lower
70s. A few afternoon showers are possible Wednesday, but high
temperatures will continue to warm into the low to mid 70s. On
Thursday low pressure will move out of the Tennessee and Ohio
Valleys and will bring widespread rainfall across the North
Country on Thursday and Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 715 AM EDT Tuesday...No changes with this update,
forecast tracking along well. Clouds have dissipated over New
York portion of forecast area, however satellite showing more
clouds to south, upstream, will work in here in a few hours.
Winds have eased as surface high pressure builds across the
forecast area. The 500 mb ridge shifts east during the near term
period as the low to the west deepens. Great Lakes 500 mb low
gets kicked out and moves across southern Quebec in the northern
stream today, bringing a few clouds along the border during the
day. Weak westerly flow and a little sun will allow
temperatures to warm into the 60s to low 70s.

Ridging continues tonight, and low level moisture trapped under
inversion, wet ground from recent rainfall and light winds will
contribute to valley fog formation. A 500 mb shortwave trough
moves out of the base of the mean trough to our west, and up
the Atlantic coast. A surface low spins up along the coast, and
the main precip area with this feature will brush southern New
England tonight, with no precip over Vermont/northern NY. Lows
tonight in the 40s to low 50s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 340 AM EDT Tuesday...For Wednesday the northeast is under
the influence of a weakening surface ridge, while a weak mid
level vort max lifts northeast. Combination of a little bit of
lift from this feature and some differential heating over the
mountains break out slight to low chance pops during the day in
the northern Adirondacks and part of the Green Mountains.
Warming trend continues into Wednesday with highs generally in
the 70s, and lows Wednesday night in the 50s.

Changes start on Thursday as the low to the west begins its
move to the east. Surface and upper low remain further to
south/southwest with diffluent flow aloft. 300 mb southerly jet
noses into New York/Vermont during the day Thursday, while 850
mb easterly flow brings Atlantic moisture into the area. Pops
begin to increase far western St. Lawrence County before
sunrise, then continue to increase west to east during the
day. Temperatures Thursday 5-10 degrees cooler than Wednesday
with rain, clouds, and cool flow off the Atlantic.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 259 AM EDT Tuesday...New 00z guidance showing some
disagreement with evolution of closed mid/upper level trof and
associated surface low pres. GFS shows a track further east
with limited qpf Thursday Night into Friday...while ECMWF shows
a negatively tilted and vertically stacked system moving from
the Mid Atlantic into Southern New England during this time
period. Both agree on precip across our cwa...but exact details
on placement of heaviest precip axis and associated pops still
has some disagreement. Will continue to mention high likely to
low cat pops for Thursday Night into Friday (65 to 80%)...with
highest values central/eastern cwa. Expecting a similar type
scenario for qpf...as nose of easterly 925mb to 700mb jet is
angled toward our eastern zones...helping to enhance moisture
advection off the Atlantic. Speaking of Atlantic...expecting a
chilly maritime airmass over our cwa during this time period and
have cut superblend temps by 2 to 4 degrees...especially
eastern/central cwa. The combination of cooler easterly
flow...lots of clouds/precip...and progged 925mb temps btwn 6-8c
support highs mid 50s to mid 60s. Warmest temps will be western
dacks/SLV.

For the weekend...weak 1013mb high pres builds into the North
Country for Saturday...with still some embedded short wave
energy and moisture with westerly flow aloft impacting our
northern zones. The combination of lingering moisture...upslope
flow...and weak energy aloft...cannot rule out a few midday
showers...especially central/northern cwa on Saturday. 925mb to
850mb thermal profiles support highs very close to normal with
mid 60s to mid 70s depending upon elevation and cloud coverage.

For Sunday...still some uncertainty on placement of weak
backdoor cold front or developing warm front lifting from
southwest to northeast across our region. This weak convergence
with embedded energy aloft may provide enough lift to support a
few afternoon showers. Instability is limited and displaced to
our southwest...so not anticipating any thunder threat. Have
continued to mention slight chance to chance pops...with threat
increasing during the afternoon hours. In addition to precip
uncertainty...still some question on max temps for Sunday...with
a wide range in thermal profiles. We will stick close to
superblend values...which is consistent with previous couple of
forecasts. Highs mainly in the upper 60s to mid 70s...with 74
expected at BTV.

Even more uncertainty as we head into early next
week...associated with additional energy aloft and timing of
another surface cold front. Latest ECMWF shows several
boundaries lifting across our region with numerous embedded
vorts in the flow aloft...along with ribbons of enhanced mid
level moisture. Initially instability is limited...but increases
some on Tuesday to support a chance of thunder. Will continue to
mention chance pops with near normal temps...as we have plenty
of time to work out the details in the upcoming days. Bottom
line not expecting any long windows without the chance for rain
and no significant heat in days 4 thru 7.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
High pres building into our taf sites will provide the region
with vfr conditions. Some lingering fog/br at MPV this morning
may produce an hour of ifr/lifr cigs/vis thru 13z. Satl and
observations show mid/upper level clouds moving toward our taf
sites this morning. Soundings show a broken to overcast deck
developing from south to north between 5000 and 8000 feet. These
clouds should prevent fog development tonight with vfr
conditions prevailing for the next 24 hours. Expect
north/northwest winds 4 to 8 knots to become light and mainly
terrain driven overnight.

Outlook...

Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. Slight Chance SHRA.
Thursday: VFR. Breezy. Chance SHRA.
Thursday Night: VFR/MVFR. Definite RA.
Friday: MVFR. Definite RA.
Friday Night: VFR. Slight Chance SHRA.
Saturday: VFR. Slight Chance SHRA.

&&

.EQUIPMENT...
The WSR-88D at Burlington, VT (KCXX) will be unavailable from
Tuesday May 23, 2017 through Friday May 26, 2017.

During the outage, radar coverage is available from adjacent
radar sites including Montague, Albany, and Buffalo, NY and Gray
ME.

A new signal processor will be installed, which replaces obsolete
technology, improves processing speed and data quality, provides
added functionality, and supports IT security.

&&

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

&&

$$
SYNOPSIS...Hanson
NEAR TERM...Hanson
SHORT TERM...Hanson
LONG TERM...Taber
AVIATION...Taber
EQUIPMENT...Team BTV



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