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  Tuesday May 23, 2017

 

NWS Area Forecast Discussion


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669
FXUS61 KBTV 212316
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
716 PM EDT Sun May 21 2017

.SYNOPSIS...
Surface high pressure will translate east of New England this
evening allowing a warm front to push into the North Country
from the eastern Great Lakes region. We will see periods of
rain developing this evening across northern New York, and
during the overnight hours across central and northern Vermont.
Lighter rain showers and overcast skies will linger during the
day Monday, resulting in relatively cool temperatures. Rainfall
amounts between one-third and one-half inch are generally
expected across the North Country tonight into Monday morning.
Dry conditions return on Tuesday with a brief period of surface
high pressure.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
As of 715 PM EDT Sunday...Overall little change to previous
forecaster thinking for this update, but based on current radar
and hi-res model trends decided to increase PoPs to 100% for
tonight. Showers are finally beginning to reach the ground over
the Tug Hill area and will be shifting into the St. Lawrence
Valley within the hour, and eastward through the night with
everyone seeing measurable precipitation.

Previous Discussion...
Mosaic composite radar reflectivity indicates axis of
steady/moderate rainfall across sern Ontario swd across far wrn
NY/wrn PA and ern OH at 1830Z. There are some leading echoes
east of Lake Ontario into St. Lawrence County NY, which will
bring a few light sprinkles or isold -SHRA across nrn NY late
this afternoon/early this evening. However, bulk of steady
precipitation doesn`t reach nrn NY until after 00Z, with onset
of stronger 850-700mb WAA and isentropic ascent approaching from
the SW. Mesoscale models, including the HRRR /BTV-4km WRF and
NAM-Nest all show rainfall reaching the Champlain Valley by 03Z
or so, and far ern VT by 05-06Z. Anticipate a 5-6hr period of
rainfall, yielding amts generally between 0.33-0.50" thru early
Monday morning. Will also see increasing P-gradient overnight.
This will result in low-level channeling of winds in the
Champlain Valley, with gusts locally up to 30 mph in the BTV
area. A Lake Wind Advisory has been issued for Lake Champlain
beginning at midnight as south winds increase to 15-25kts during
the pre-dawn hrs. Overnight lows will generally be in the mid-
upr 40s tonight.

Best large-scale forcing slides to our east between 12-15Z
Monday, but NAM RH profiles indicate continued saturated
conditions in 950-850mb layer, and skies will generally remain
cloudy with low overcast in place. The low-level inversion
layer in place will keep sfc temps cool, despite 850mb thermal
ridge in place (+10C to +11C) across nrn NY. Sfc high temps
generally low- mid 50s east of the Greens, upr 50s in the
Champlain Valley, and upr 50s to lower 60s across nrn NY.
Maintained a chance of showers Monday afternoon. There is some
indication of a trailing sfc trough/convergence line moving ewd
across nrn NY into VT late in the afternoon, which may result in
an additional period of (brief) rain shower activity.

A weak sfc ridge builds newd into our region from western NY
Monday night. This results in lowering inversion layer and light
near-sfc winds. With moist soils, will see combination of
abundant low clouds and patchy fog areawide. Moist layer is
quite shallow, so not anticipating any precipitation. Lows
Monday night mainly 43-48F.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 339 PM EDT Sunday...The short term looks to be the quiet
intermission between the unsettled periods of the near and long
term. After the passage of a cold front and associated trough, a
weak ridge moves in, leaving Tuesday looking like a dry and fair
day across the region. Winds will remain west-southwesterly
behind the front so little change in the air mass leads to
warmer temperatures than just prior to frontal passage with
highs in the upper 60s and low 70s. Gradual increased cloud
cover moving in from the west Tuesday night ahead of the next
system will lead to low temperatures low 50s in the western
counties and 40s in the eastern half.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 339 PM EDT Sunday...The long term pics up again in
activity as multiple systems will impact the area through to
the weekend. A coastal low moves northeast into New England. The
GFS and ECMWF still disagree on the inland advection of the
precipitation with the GFS keeping it mostly offshore while the
ECMWF being more aggressive and extended the precip into
Southeast VT. For now have just kept chance PoPs east of the
Greens for Wednesday.

Thursday has a positively tilted upper trough associated surface
low over Ohio Valley with a closed off upper low. The low
progresses slowly to the northwest of the CWA before shifting
west over the northern counties. This leads to and extended
period of unsettled conditions and potential for precipitation
from midday Thursday and through midday Friday as low pushes out
to the coast. Lingering showers in the higher terrain remains
in the resulting northwest flow through to early Saturday
afternoon. The second half the weekend sees a high pressure
ridge begin to build back in leading to a brief return to fair
conditions.

High temperatures in the long term will range from the upper 60s to
upper 70s, while lows will be in the 40s to 50s.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday...Will see a gradual lowering of cloud
ceilings through the evening with increasing chances for rain
showers, especially during the overnight hrs. After midnight,
should see development of MVFR ceilings (2-3kft) at SLK/MSS,
along with HIR TRRN OBSCD areawide and vsby 4-5SM at times in
showers and BR. There is a chance of MVFR ceilings at the
remaining TAF locations, but anticipate predominantly 3-4kft
ceiling heights for RUT/BTV/PBG. Should see MVFR developing at
MPV by 14Z/Mon. Shower/rain activity diminishing in coverage but
another possible focus area coming across from west to east
late in the day. Otherwise, persistence with MVFR/VFR ceilings.

Winds generally less than 10kts through 06Z. Thereafter, should
see some gusts from the south approaching 20kts at BTV/PBG as
gradient flow strengthens toward daybreak.

Outlook...

Monday Night: VFR/IFR. Chance SHRA...FG.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. Chance SHRA.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Chance SHRA.
Thursday Night: VFR. Likely SHRA.
Friday: VFR/MVFR. Likely SHRA.

&&

.MARINE...
As of 231 PM EDT Sunday...A Lake Wind Advisory is in effect
starting at midnight (04Z Monday). Gradient flow increases out
of the south during the pre- dawn hours Monday, with sustained
winds over Lake Champlain reaching 15-25kts after midnight and
waves building to 2-4 feet. The highest waves are expected
across the northern portion of the broad lake south of Grand
Isle. South winds will remain generally in the 15-25kt range
during the daylight hours on Monday, before diminishing Monday
evening.

&&

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

&&

$$
SYNOPSIS...Banacos
NEAR TERM...Banacos/Lahiff
SHORT TERM...MV
LONG TERM...MV
AVIATION...Banacos/SLW
MARINE...Team BTV



 
 
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