Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
652 am EST Sat Dec 20 2014
surface high pressure across the Great Lakes region will build
slowly eastward through the weekend bringing generally dry weather
conditions. The next significant storm system arrives for
Christmas evening with very windy and mild conditions. Periods of
moderate to briefly heavy rain are expected late Christmas evening day
into Christmas evening night. This will be followed by brisk and
somewhat colder conditions during Christmas day with snow showers
possible...especially across the higher terrain.
Near term /until 7 PM this evening/...
as of 622 am EST Saturday...main change for 630 am update was to
use btv12 blended with btv4 to get close to current sky cover and
how clouds might evolve through the day. Most breaks in the clouds
this morning with more clouds moving in this afternoon. Rest of
the forecast is in good shape. Previous discussion follows.
Large surface high pressure ridge remains over the north country
today. Generally dry weather conditions are expected with light
winds. Clouds are still the toughest part of the forecast for
today...which of course affects our temperature forecast. Have
gone with a forecast with some clearing skies this
morning...followed by some middle level clouds across the area this
afternoon. Temperatures today will be colder than seasonal
normals...middle 20s to around 30. Temperatures will be highly
dependent on clouds.
Short term /7 PM this evening through Monday/...
as of 315 am EST Saturday...more of the same for the rest of the
short term forecast with surface high remaining over the area
through Monday. Dry weather with light winds will be the main
story. Some vorticity advection will bring clouds to the area
Sunday. Temperatures will be below normal through the period.
Long term /Monday night through Friday/...
as of 340 am EST Saturday...longer range data still supports the
idea of rainy and windy conditions on Christmas evening day and night.
Extended portion of the forecast starts off on a rather quiet note
as high pressure retreats into Canadian Maritimes Monday night
into Tuesday. Weak disturbance in flow aloft combined with
increase in moisture as low level flow becomes more easterly will
result in clouds and a chance of snow or rain showers on Tuesday
with high temperatures in the 30s.
Precipitation chances increase Tuesday night and especially on
Wednesday into Wednesday night. Deep upper trough develops over
the Midwest and evolves into vertically stacked low over the
central Great Lakes Wednesday. Significant piece of energy
rounding base of this trough Tuesday night will result in upper
trough taking on negative tilt during Wednesday. This will lead to
good influx of moisture into the region...driven by increasing 850
mb jet which may reach 50-60 kts later Wednesday. Will need to
keep an eye on the wind situation with these strong winds
aloft...especially over the higher terrain and along the western
slopes. These winds could have an impact on utilities. One to two
inches of rain is expected with this system. Amounts may vary
quite a bit however due shadowing in some areas and orographic
enhancement in others...especially on southeast facing slopes of
southern greens and Adirondacks. The combination of rain and mild
temperatures will cause significant snowmelt. This combination of
snowmelt and rainfall will cause rivers to rise and flood threat
will need to be monitored as well. Dry slot moves in Christmas day
and by the time colder air moves in...the bulk of the precipitation
will be out of the area. Best chance for seeing some snow showers
on Christmas day will be over the Adirondacks and northern greens.
Maximum temperatures will be in the 30s to around 40. Southwest flow
continues Friday. Expect little change with chance mountain snow
showers and temperatures mainly in the 30s.
Aviation /12z Saturday through Wednesday/...
through 12z Sunday...low clouds have dissipated across much of the
area. IFR conditions hanging on at slk however...with improvement
to VFR expected by around 14z. MVFR ceilings trending VFR at pbg this
morning. At rest of sites...expect mainly clear skies into this
afternoon with just scattered low clouds. Some middle clouds enter
the area later today with a return of low stratus tonight.
Conditions expected to deteriorate to MVFR at most sites...and
IFR at slk. Also...visibilities may lower to MVFR at times tonight
in br...especially at slk/mss. Winds will be light/variable
through the period.
Outlook 12z Sunday through Wednesday...
12z sun-00z Tuesday...some periods of MVFR ceilings with areas of low
clouds...otherwise mainly VFR conditions under high pressure.
00z Tuesday-12z Wednesday...periods of MVFR in light mixed precipitation.
12z Wednesday-00z Thursday...periods of MVFR/IFR in rain. Gusty winds possible.