Area Forecast Discussion
Issued by NWS Burlington, VT
FXUS61 KBTV 221513
Area Forecast Discussion
National Weather Service Burlington VT
1113 AM EDT Sat Oct 22 2016
Periods of rain and drizzle continue as a mid level trough of low
pressure remains over the Northeast. As the system moves past,
colder air will filter in bringing with it northwest flow
producing upslope snow at the higher elevations tonight into
Sunday morning. Another surface low pressure system looks to
affect the Northeast Thursday into Friday.
.NEAR TERM /THROUGH SUNDAY/...
As of 1108 AM EDT Saturday...Quick update to snowfall totals and
issuance of a winter weather advisory 22Z SAT thru 15Z SUN for the
northern Adirondack region. Colder 850mb temps and evolution of
colder 2-m temps on 06Z NWP guidance suite lends to the idea of
accumulating snowfall across areas above 1500` in nrn NY. 3-5" on
avg, highest near 2000` and above. In VT, also anticipate a switch
to snow late this evening and overnight, with orographically
favorable snowfall into Sunday morning with strengthening nwly
flow as deepening low pressure tracks nwd through eastern Quebec. Most
of the accumulating snow is above 2000`, so no advisory due to
limited spatial impact. However, 6-8" at summit level expected Jay
Peak to Mt. Mansfield.
Previous discussion...Overall forecast in good shape. Expect
winds to pick this morning at 6-16kt with some gusts developing in
the afternoon/evening hours. Near term forecast challenges are
thermal profiles and potential for strong winds to mix down from
Current radar reflectivities show light rain and drizzle
affecting the North Country as the 500mb trough continues to to
slowly tilt negatively. Models continue to show more pronounced
negative tilting developing today as 500mb trough develops closed
low. This will be reflected at the surface as closed low
traversing northward from the southern New England coast this
morning, to Maine by this evening. As the North Country winds up
on the backside of this system, colder air filters in on the NW
flow, increasing potential for snow in the higher terrain. Also in
this NW flow, terrain enhancement of precip will result. Models
disagree on thermal profiles with NAM appearing to be coldest
solution throughout the low levels. Overall, expectation for snow
to develop at highest elevations this afternoon into evening with
colder air lowering down to about 1500-2000 feet with snow or mix
of rain and snow possible overnight. Broad valleys will remain
warmer with rain showers. Moisture will tapering off Sunday
morning, with best chances for lingering precip being terrain
induced by mid day Sunday. Temperatures expected to warm enough on
Sunday to mostly be rain except at summits.
Addressing concerns of strong winds/wind gusts. 850mb jet out of
the NW of 40-50kts expected to move into the North Country this
evening around 00Z. Jet looks to strengthen around 06z Sun to
50-60kts. Mesoscale models show these winds only mixing to
30-40kts in Adirondacks at 2500ft elevations and above. BUFKIT
soundings show similar trends as precip overnight and into Sunday
morning will help keep low levels stable and prevent mixing these
winds down. Therefore, only expect isolated gusty winds greater
than 39kts, as most areas will see gusts more in the range of
20-30kts. With newly saturated soils, can`t rule out an isolated
incident of tree damage and power outages. Best chance for this
would be in high terrain above 2500 ft and any possible
downsloping on SE facing slopes. 850mb jet begins to weaken Sunday
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 411 AM EDT Saturday...The region will remain under cyclonic
flow through the period, as a surface low pressure area remains
over Quebec. Have gone with a dry forecast for Sunday night, as
mos pops are low. On Monday, forecast area remains under cold
advection, with models hinting at some orographic rain and snow
showers over the Adirondacks and Green Mountains for Monday and
Monday night. Have gone with slight chance pops in these areas for
Monday and Monday night. Have kept valley areas such as the
Champlain and Saint Lawrence valleys dry through the period.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 411 AM EDT Saturday...The region will still remain under
cyclonic flow Tuesday and Wednesday. Will continue with slight
chance pops for orographic rain and snow showers over the
Adirondacks and Green Mountains for Tuesday and Wednesday.
Wednesday night, a high pressure area will build into the region
from the Great Lakes with fair and dry weather expected across the
north country. Models showing some differences on Thursday, with
the GFS model keeping the weather dry all day, as a ridge of high
pressure will be over the region. GFS model also suggesting dry
weather will continue into Thursday night and Friday as well.
However, the ECMWF model starts Thursday off dry across the
region, but brings rain showers ahead of a warm front into
northern New York Thursday afternoon, mainly across the
Adirondacks and Saint Lawrence valley, while the Champlain valley
and Vermont remain dry on Thursday. Have adjusted superblend pops
to the ECMWF timing, and will bring in showers to northern New
york Thursday afternoon. Much like the GFS, the ECMWF model has
trended slower with bringing in showers to the region on Thursday.
Have gone with superblend pops for Thursday night and Friday,
given model differences. Thus, will have a chance of showers in
the forecast for Thursday night and Friday, per the ECMWF model.
.AVIATION /15Z Saturday THROUGH Wednesday/...
Through 12z Sunday...Widespread LIFR and IFR start the period
with gradual improvement to MVFR/IFR expected this morning into
early afternoon. Coastal low moves northward into Maine, allowing
more wrap around precip and moisture to affect the North Country
this afternoon. Expect conditions to deteriorate to IFR/LIFR when
this happens along with increasing winds/wind gusts. NW winds
shifting WNW at 5-15kts increase to 10-20kts with developing gusts
of 20-30kts late in the day and into the overnight. Periods when
winds briefly subside will likely result in strong LLWS around
Colder air will also filter in on this NW flow, meaning icing
aloft possible and snow in the higher terrain, generally above
Outlook 12z Sunday through Wednesday...
12z Sunday through 00z Monday: A prolonged period of unsettled
conditions is expected with widespread IFR/LIFR in periods of
00z Monday through 00z Wednesday: A mix of VFR/MVFR with upslope
showers in NW flow.
00Z Wednesday through 00Z Friday: IFR/MVFR fog development
possible during the early morning hours.
As of 445 AM EDT Saturday...Observed rainfall amounts have varied
widely across the North Country so far, with highest amounts over
Northern New York in excess of 3 inches. This has resulted in
river rises well within banks. Additional rainfall of 1 to 2
inches expected through Sunday evening with more rises on streams
and rivers expected without incident. However...some minor urban
and street flooding is possible associated with the heavier
rainfall rates through Saturday with leaves clogging storm drains.
Otherwise...no widespread flooding is anticipated.
NY...Winter Weather Advisory from 6 PM this evening to 11 AM EDT
Sunday for NYZ029>031-034.