50.6°F
Current conditions from King Hill
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  Tuesday May 23, 2017

 

NWS Area Forecast Discussion


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FXUS61 KBTV 230719
AFDBTV

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

.SYNOPSIS...
A weak cold front crossing New York and Vermont through this evening
will bring isolated showers, along with lingering low clouds and
areas of fog overnight. Will see clearing Tuesday with a weak
area of high pressure in place across the northeastern U.S. and
temperatures moderating back into the upper 60s to lower 70s. A
few afternoon showers are possible Wednesday, but high
temperatures will continue to moderate into the low to mid 70s.
A large mid-level trough across the Tennessee and Ohio Valleys
and associated developing surface low pressure will bring
increasing chances for widespread rainfall across the North
Country on Thursday and Friday.

&&

.NEAR TERM /UNTIL 2 PM THIS AFTERNOON/...
As of 702 PM EDT Monday...Minor adjustments to the previous
forecast for this evenings update, mainly to reduce pops and
tweak sky cover. Frontal showers have quickly exited the region
to our east, and while a few stray showers may be around through
the evening, in general the remainder of the night will be dry.
Forecast challenge for sky cover remains though with subsidence
building in aloft and an abundance of low level moisture
around. Current thinking is that sky cover will be widely
variable through the night with some low stratus hanging tough
over higher elevations, while many valley locales may clear out
to a scattered/overcast mid/high deck. Can`t rule out some areas
of fog, especially in any clearing so have left that in, but
signals are trending towards less of a chance of dense fog and
more BR-ish with winds just off the deck hanging in the 10-15
knot range. Lows remain on track for mid/upper 40s to low 50s.

Previous Discussion...
Will see some gradual mid-level drying this evening (above
750mb) with WSWLY flow aloft, but pronounced low- level
inversion should continue to hold low stratus in areawide with
overcast skies and cool temperatures. Afternoon highs only
expected to range from the lower 50s east of the Green Mtns, to
near 60F at BTV, and upr 50s to lower 60s across nrn NY. The
KCXX vad wind profile still indicates 25-30kt flow at 2-3kft
AGL. Won`t fully see these winds at low elevations due to
stability, but occasional gusts to 20-25 mph are possible thru
this aftn. Expect winds remaining 20-25kts over the broad
portion of Lake Champlain, and the Lake Wind Advisory continues
there.

Tonight through Tuesday a weak surface ridge builds into the
region. Lowering inversion and light surface winds, along with
moist ground from recent rain will promote fog formation in the
usual areas. During this time flow aloft remains southwesterly,
and low pressure over the Great Lakes will ride through the 500
mb ridge, suppressing the ridge & shifting it east. The low
passes well enough north that the surface ridge will win out
with no rain during this time, but will still be quite a few
clouds around. Tuesday about 10 degree warmer than monday with
highs in the 60s/near 70.

&&

.SHORT TERM /2 PM THIS AFTERNOON THROUGH THURSDAY/...
As of 315 PM EDT Monday...12z guidance suite still indicating
that Wednesday will be the warmest day of the entire weak. Weak
ridging aloft will put the region into a col area (light flow
regime). Hi-res models do hint at just enough low level moisture
and surface instability will exist to pop a few showers,
primarily across the higher terrain in the afternoon, though
with an inversion around 15,000ft not expecting any t-storms to
develop. Winds from 10,000ft down to the surface will be
generally 10 knots or less, so look for onshore lake breezes to
develop. 925mb temperatures will be running about 17C, which
given a decent amount of sunshine will result in lower elevation
temperatures within a couple of degrees of 80F.

Wednesday night flow starts to turn south/southeast as low
pressure moves toward the Great Lakes. Models all show an area
of deeper moisture moving toward the region, so as we move
toward daybreak Thursday it appears precipitation will be
starting to overspread the region. Have depicted a ramping up of
PoPs up well after midnight, though most of the night will be
dry.

&&

.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 /07Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...A challenging aviation forecast
continues thru 12z this morning with fog product and obs showing
multi cloud layers with categories ranging from ifr at rut/mpv to
vfr elsewhere. Thinking ifr conditions become mvfr/vfr at
rut/mpv shortly as winds help with mixing. The combination of
yesterdays rainfall and lighter winds after 08z...and several
locations going 3 to 6 degrees below cross over temps...thinking
some fog/br will develop between 08z-11z. Have utilized tempo
group at rut/mpv and slk to highlight fog/br potential early
this morning. Overall confidence in IFR potential is on the low
side...given 10 to 15 knots of winds around 975mb. After
12z...expecting cigs/vis to become VFR with winds shifting to
the north at 4 to 8 knots...with some localized terrain driven
gusts. Some high clouds possible today as coastal system passes
to our east.

Outlook...

Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Breezy. Likely RA.
Thursday Night: MVFR with areas of IFR CIGS MPV. Breezy. Likely RA.
Friday: MVFR with IFR MPV/SLK. Likely RA.
Friday Night: VFR. Chance SHRA.
Saturday: VFR. Slight Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Banacos
NEAR TERM...Banacos
SHORT TERM...Nash
LONG TERM...Taber
AVIATION...Taber



 
 
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