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Area forecast discussion
National Weather Service Burlington Vermont
957 am EDT sun may 20 2018

Synopsis...
a cold front will push through the region on this morning,
bringing showers to an end with clearing in the afternoon. High
pressure quickly builds back in tonight and Monday with clear
skies and warm temperatures. Other than a chance of showers
Tuesday and Wednesday, most of the week ahead looks dry with
temperatures on the warm side of normal.

&&

Near term /through Monday/...
as of 953 am EDT Sunday...no significant changes were needed
with this update. The cold front continues to March across the
region at this hour and now lies roughly from St Johnsbury to
Waterbury to Newcomb. The showers associated with this front
will also continue to move southeast through the morning hours
and should exit the Vermont and northern New York by early afternoon.
Satellite imagery shows clearing behind the front, so still
anticipate sunshine returning this afternoon. The forecast has
this pretty much all covered, so just made some minor tweaks to
pops and sky cover to match the latest trends.

Previous discussion...an upper level trof and associated cold
front will move through the region between 12 and 18z today. It
will be preceded with showers most numerous over northern New
York and northern Vermont. There is some very limited elevated
instability and a few pulses of lightning detected in Ontario
last hour but not enough to be concerned with. Some light to
moderate rainfall has been seen on mrms qpe in the showers, so
another few tenths of an inch of precipitation is possible.

Drier air will follow the frontal passage, bringing the showers
to an end this morning and eventually allowing for some sunshine
Sunday afternoon, perhaps a bit more stratocu in the mountains
with developing northwest flow. 925mb temps get up to around 12c at btv
which should bring high temps from the mid 60s in the higher
elevations to lower 70s in the wider valleys.

Clear skies will dominate Sunday night and Monday with high
pressure building into the region. Low temps will range from the
mid 30s in parts of the Adirondacks and extreme nek to mid 40s
near Lake Champlain. 925 temps on Monday get back up to 14-15c
so it will be a little warmer with highs in the 70s, perhaps
upper 70s in a few warm spots.

&&

Short term /Monday night through Tuesday night/...
as of 340 am EDT Sunday...no big changes from the 00z guidance,
so the forecast remains fairly similar to the previous version.
Quiet and dry weather Monday night. Still looking at a weak
upper level trough to swing across the region during the day. As
it approaches, it will pull clouds and moisture toward the
region from the south. Latest model trends indicate that the
thicker clouds will likely be across southern areas closer to
the deepest moisture. Those clouds will also keep it a smidge
cooler (upper 60s-lower 70s) in our southern areas. 00z NAM and
btv 4km WRF indicate that with the slightly more sunshine and
warmer temperatures (mid-upper 70s) closer to the Canadian
border, minimal surface based instability will develop and
result in a few showers, perhaps an isolated T-storm, forming
along the thermal gradient resulting from the more sun vs more
clouds region. All in all, still appears most of the day will be
dry for most folks. Pops remain in the 30-40% range for mid
afternoon thru early evening. Any showers dissipate by late
Tuesday evening, resulting in clearing skies.

&&

Long term /Wednesday through Saturday/...
as of 340 am EDT Sunday...00z guidance all seem to be pretty
similar to one another, and in line with prior runs. Should be a
fairly dry period, with likely Summer-like conditions at the
end of the week. A few notes concerning the forecast for each
day follows...

Wednesday: a mostly dry cool front should push southward during
the day. Temperatures aloft south of the front will be quite
warm (16-19c @ 925mb), so southern valley areas should make a
run at 80f before the front arrives. Northern areas will still
top out in the lower-mid 70s. Given pretty dry airmass in place
prior to the front, don't think there will be much in the way of
shower activity. Have painted in generally 20-30% pops. Clear
with seasonable temperatures Wednesday night.

Thursday: 925mb temperatures will be down to 9-11c, but this
will still result in near normal temperatures, with highs in the
upper 60s to lower 70s. Ridging at lower levels will result in a
sunny, dry day.

Friday: looks like upper level ridging builds to our west.
Although flow aloft will still be northwest, there will be
anomalously warm air in place across central Canada which will
begin advecting into our region. The GFS, Canadian and European model (ecmwf)
models are all consistent with 925mb temperatures in the 17-20c
range. Typical rule of thumb for the warm season under sunny
skies is to add 10c to those temperatures to get a rough
estimate of high temperatures at lower elevations. That rule
gives 27-30c, which equates to low/mid 80s. At this point, most
statistical MOS guidance is still much lower than that, so I
did go higher than those models, and trended about 5 degrees
warmer than previous forecast. Painted in highs around 80f for
valley regions and mid/upper 70s elsewhere. This may still end
up being a conservative forecast if the recent model trends are
correct.

Saturday: upper ridging moves nearer to the region, though
low/mid level flow turns more southwest and starts to advect in
moisture. A bit more uncertainty as to how warm it may get.
925mb temperatures range 14-17c per ECMWF, 19-22c per Canadian
and 20-23c in the GFS, which cover a range supportive of
potential highs in the upper 70s to upper 80s (which is all
above normal). Again, statistical guidance is all closer to the
low end of that temperature range. I did opt to go a few
degrees above, but only to around the 80f mark. Also some
indications that with some extra moisture around, we could get
daytime heating showers or T-storm and that would act to keep
things a bit "cooler". Have 20-30% pops for the shower
potential. However, it's still possible the temperature forecast
is again conservative and it could feel much more like mid-
Summer to kick off the Holiday weekend.

&&

Aviation /14z Sunday through Thursday/...
through 06z Monday...mainly MVFR in showers through about 16z
then becoming VFR behind a cold front through the rest of the
period. Showers along and just ahead of the front have pushed
through mss and are moving through slk, btv, and pbg through
about 14z and rut/mpv through 15-16z. Otherwise, winds will
gradually shift to north-northwest as front moves through. Expecting winds
to be between 10-15 kt with gusts up to 20 kt possible. With
advection of drier air, ceilings will lift with some scattered- broken
low and middle clouds this afternoon with sky clear and light winds
tonight as high pressure builds in.

Outlook...

Monday: VFR. No sig weather.
Monday night: VFR. No sig weather.
Tuesday: VFR. Chance rain showers.
Tuesday night: mainly VFR, with local IFR possible. Slight chance
rain showers.
Wednesday: VFR. Slight chance rain showers.
Wednesday night: VFR. No sig weather.
Thursday: VFR. No sig weather.

&&

Btv watches/warnings/advisories...
Vermont...none.
New York...none.

&&

$$
Synopsis...Sisson

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