FXUS61 KBTV 180540
Area Forecast Discussion
National Weather Service Burlington VT
140 AM EDT Tue Sep 18 2018
Unseasonably warm weather will continue tonight into tomorrow
morning behind high pressure off the east coast. Moisture from
former Hurricane Florence arrives across southern Vermont later
tonight into the first half of Tuesday, with a steady wetting
rainfall likely along and south of U.S. Route 4 and very little
precipitation to the north. A cold front moving south across
the region Tuesday will bring a cooler, more seasonable airmass
into late week as high pressure builds in from Canada behind the
front. The next chance of precipitation comes late in the week
as another frontal system moves through the area.
.NEAR TERM /UNTIL 2 PM THIS AFTERNOON/...
As of 709 PM EDT Monday...A record high temperature for 9/17 of
87F was set at BTV this afternoon, beating the old record of
86F set in 2015. High level clouds will continue to overspread
the North Country tonight from SW-NE, in advance of the tropical
remnants across the upper Ohio River Valley. Have made some
minor adjustments for sky cover and temperatures. With clouds
mitigating radiative cooling, left out any fog development for
the overnight hrs.
Models continue to show the remnant of Florence`s deeper
moisture arriving overnight after 06z lasting until about noon
in the far southeast near VSF. The question is how far north it
gets and how much QPF. Going more with the GFS which has a
pretty good handle on the current location of the moisture. NAM
is a little bit south of the GFS. Keeping continuity with the
previous forecast categorical PoPs are forecast in Rutland and
Windsor counties. Also expecting a tight gradient of rainfall
with up to an inch amounts a half to r so near KVSF, but with
such a tight gradient it could vary either way. Low temperatures
to remain quite mild in the 60s to locally near 70 in the
Champlain Valley as light south winds continue.
There will be a period of time behind the Florence moisture and
ahead of an approaching cold front where clouds will break a bit and
instability develops on the order of 200-400 J/kg so a shower is
possible with the front as high temperatures approach 80 before
falling during the afternoon from north to south. Expect a little
northerly wind channeling in the Champlain Valley of 10 to 10 mph
behind the front. There may also be a band of lower clouds as the
front pushes south.
By Tuesday night, the front will push south and some clearing
expecting 40s north and 50s south. Will have to watch for the
possibility of fog and stratus developing by Wed morning, but its a
bit unclear at this point with some cold advection offsetting that
.SHORT TERM /2 PM THIS AFTERNOON THROUGH WEDNESDAY NIGHT/...
As of 350 PM EDT Monday...Wednesday should see gradual
improvement throughout the day as high pressure nudges south out
of Canada. Morning clouds will hold on across much of the area
with an inversion in place preventing the mixing of drier air
aloft. As temperatures warm slowly, the inversion should begin
to break down allowing us to eventually mix out some to possibly
most of the clouds, with far southern and eastern VT likely
holding on to clouds the longest. Overall, precipitation chances
are close to nil Wednesday but a few hi-res models are hinting
at some subtle surface convergence, and subsequently some light
drizzle, for far eastern Northeast Kingdom (along the NH-VT
border) Wednesday afternoon. Have kept a slight chance in across
these areas at this time.
With cooler air moving in, 925mb temperatures Wednesday will be
around 11C, supporting temperatures in the mid to upper 60s across
much of the area. Temperatures spreads on Wednesday are highly
dependent on cloud coverage, and since thinking is at this time that
clouds could be lingering into the afternoon have trended away from
some of the warmer guidance for Wednesday...but didn`t want to take
it as cold as NAM is suggesting. Currently have high of 68 in for
With plenty of dry air aloft, and most of the clouds dissipating by
sunset, anticipating a good night of radiational cooling across much
of the area. Have nudged temperatures down a bit, mainly across the
Northeast Kingdom and Adirondacks. Biggest challenge for Wednesday
night, aside from temps, will be the fog potential across the area.
Difficult to tell at this time whether or not fog or low status deck
will develop. As with temperatures, if areas hold onto any residual
clouds this would affect their ability to radiate efficiently.
Overall, still quite a bit of uncertainty on exact details of the
forecast at this time...a lot of moving parts at play here.
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 350 PM EDT Monday...Thursday should see similar
conditions to Wednesday. Temperatures will moderate slightly as
winds gradually turn southerly throughout the day Thursday. High
clouds will increase Thursday night ahead of the next system
which should keep temperatures slightly warmer compared to
Wednesday night. Model consensus is becoming better aligned for
the system Thursday/Friday with ECMWF beginning to catch on to
the idea of a deepening low tracking well north out of the Great
Lakes. The greatest forcing, and bulk of the precip, will be
considerably north of the CWA, but portions St. Lawrence and
Franklin counties, NY, could see a chance for rain Thursday
night as the warm front pushes north into Quebec. A chance for
rain remains during the day on Friday into Friday night with the
cold front expected to cross our area quickly Friday
evening/night. CAPE values as this front pass are pretty meager,
~200 J/kg (GFS) ~500 K/kg (ECMWF), but wouldn`t rule out the
possibility of an isolated strong storm and a few rumbles of
thunder. Additionally, winds ahead of this cold front will
likely be pretty breezy, with SW winds between 40-50 knots at
850mb. With differences still in the strength of this low, the
strength of these winds could change as things become better
Aside from the brief warm up ahead of the low on Friday,
temperatures through the weekend should be seasonable with highs in
the mid to upper 60s Saturday, Sunday and Monday. Low temperatures
will certainly feel fall-like with the coldest temperatures likely
Sunday night (mid 30s to mid 40s across the area) as Canadian high
pressure settles over the region. The system that the ECMWF was
picking up on during the Sunday timeframe looks to pass just south
of our far southern zones. However, the GFS has some piece of energy
streaming north of the area...with uncertainty in the forecast at
this time have kept a 20-30% of rain in the forecast for
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Through 06Z Wednesday...Changeable conditions over the next 24
hours with a mix of VFR/MVFR. Mainly VFR/light winds through 15Z
with only restrictions at KRUT where a period of steadier light
rains and occnl MVFR will prevail in the 06-12Z time frame.
Thereafter, two separate cold fronts drop south into the area by
this afternoon/evening with scattered light shower activity
expected. Scattered nature of activity warrants only VCSH in the
forecast at this point. Winds shift from light
south/southwesterly to northerly behind the boundaries with cigs
likely lowering to MVFR at northern terminals by later this
afternoon and this evening.
Wednesday: Mainly VFR, with local MVFR possible. NO SIG WX.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. Slight chance SHRA.
Thursday Night: MVFR/IFR conditions possible. Chance SHRA.
Friday: Mainly MVFR, with local VFR possible. Chance SHRA.
Friday Night: Mainly VFR, with areas MVFR possible. Chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. NO SIG WX.