Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
750 am EDT Friday Mar 27 2015
a low pressure system will exit the region today leading to a
quiet weather pattern over the next couple of days. The drier air
will lead to a return of below normal temperatures through the
weekend. At the beginning of next week another low pressure system
will bring a weak cold front through the forecast region leading
to a chance of precipitation on Monday.
Near term /until 8 PM this evening/...
as of 725 am EDT Friday... radar echos are beginning to fill in
over northern New York so I feel pretty good about where the
forecast is at the moment. Will continue the chance probability of precipitation for the
orographic snow showers through the early morning. Temperatures and dew
points were right in line with current observation so no significant
chances to the previous forecast. Based on latest NAM guidance I
continued the potential for fog mainly in the Champlain Valley and
over southern Vermont through 14z which is about 2 hours later
than I had this morning. Boundary layer winds will still be
marginal so there is still potential for fog development under a
mostly saturated surface layer. As of the latest ob at Rutland
visibilities have dropped to 1/4 mile and in Springfield the ob
has be fluctuating between 3/4 to 1 mile over the last hour.
Previous discussion as of 351 am Friday... current composite
radar shows the bulk of the available precipitation is well south and
east of the forecast area and only a few light echos show over
southern Vermont. Currently dont have any ground truth as to the
light echos but its possible a few light snowflakes are making it
to the surface as the surface is almost completely saturated.
Given the heavy saturation and the weak boundary layer winds, some
patchy fog has formed across southern Vermont and up into the
Champlain Valley. Here at the btv Airport we are still clear but
across the lake in Plattsburgh they are reporting 3 miles of
visibility and further south in both Rutland and Springfield both
sites are reporting between 1-3 miles of visibility. Current short
range guidance keeps the region pretty much locked in with
saturation through the late morning before finally beginning to
dry out. Forecast boundary layer winds look to stay below 6 miles per hour in
the Champlain Valley through around 15z this morning expect this
mornings commute to see some areas of patchy fog. As of this
update I dont expect any sort of widespread dense fog.
As the surface low pressure system drifts off south of Nova Scotia,
the positively tilted upper level trough will finally begin to makes
its way into the north country. The vorticity associated with the
trough will combine with the topography of the mountains in both
The Greens and the Adirondacks to produce some light orographic
snow showers today before the dry air in the middle levels pushes
into the area by late afternoon/early evening. With northwesterly
winds at the surface expect the cold air to continue to be
funneled into the region most of the day. Highs today will likely
be in the upper 30s across most of Vermont and in the middle to low
30s across northern New York.
Short term /8 PM this evening through Sunday/...
as of 351 am EDT Friday...it remains a broken record but the
upper level trough will be quite slow to actually clear the New
England region and will still be trying to hold on this evening.
As the trough does move the east we will see a return of
northwest flow and continued cold air advection as a surface high
pressure system builds into the area. This will result in clearing
skies and cold dry weather over the weekend. Expect maximum temperatures on
Saturday to be in the middle to upper 20's across the Saint Lawrence
and Champlain Valley and only rising to the teens in elevations
above 2000 feet. Overnight lows on Saturday night/Sunday morning
will drop into the middle teens in the valleys with the typical cold
spots dropping into the single digits. By Sunday the high pressure
system centered over the Carolinas will slowly drift offshore
leading to a return of warmer southerly flow. That will cause
temperatures on Sunday to rebound into the middle to upper 30s across most
of Vermont and northern New York.
Long term /Sunday night through Thursday/...
as of 331 am EDT Friday...a progressive middle-upper level flow pattern is
anticipated through the extended forecast period...with temperatures
continuing slightly below average and an absence of any
significant precipitation systems. A few minor troughs/low
pressure systems embedded in west-northwest flow expected...with main light
precipitation potential late Sunday night into Monday...and again during
the daylight hours on Thursday.
Northern stream shortwave trough...with main surface low passing to
our north will bring increasing clouds followed by scattered light
snow showers late Sunday night. Overall moisture is limited with
this system...so generally looking at a dusting to 1-2" of
snow...with higher amts generally at or above 1000ft. May see a
few rain showers during the day Monday as surface trough shifts eastward
across the north country. Lows Sunday night generally in the middle-upper
20s...with temperatures warming into the upper 30s to lower 40s for
Generally looking at a northwesterly middle-level flow pattern Tuesday and
Wednesday. Next shortwave trough/clipper type system is expected to
pass just to our south and west during the day Tuesday. May see a
period of increasing cloudiness...and also carried 20-30 probability of precipitation across
northern New York zones for Rain/Mountain snow showers as best differential positive vorticity advection
passes by during Tuesday afternoon. Highs on Tuesday generally in
the middle 30s across the Adirondacks...to upper 30s to lower 40s
elsewhere. Generally fair Tuesday night...Wednesday...and Wednesday
night with narrow ridge of surface high pressure expected across the
northestern Continental U.S. Into Quebec. Looking at overnight lows generally in the
20s...and highs on Wednesday in the upper 30s to lower 40s.
Middle-tropospheric flow becomes zonal to west-southwesterly on Thursday with
warm/occluded front passing from west to east across the region.
This likely brings another period of cloudy skies and light
rain/snow showers. At this point...significant quantitative precipitation forecast appears
unlikely. Highs on Thursday again near to slightly below climatology
norms...with afternoon readings generally in the low-middle 40s.
Aviation /12z Friday through Tuesday/...
through 12z Saturday...mainly MVFR conditions through the daylight
hours today...with localized IFR ceilings/visibility in mist at
slk/pbg/rut/mss through 15-16z. Region remains in frontal zone
north and west of departing frontal zone off the New England
coast. Upstream secondary front across southern Quebec will push southeastward
across the region later this morning...resulting in northwest wind shift
(5-10 kts). Winds will remain 5-10 kts this afternoon through tonight.
Ceilings generally MVFR this afternoon and through tonight...with
sprinkles/flurries possible at times.
Outlook 12z Saturday through Tuesday...
12z Saturday through 00z Sunday...areas of MVFR central/eastern Vermont
with isolated snow showers. Otherwise...VFR.
00z Sunday through 00z Monday...VFR/mostly clear with high
pressure in place.
00z Monday through 00z Tuesday...low pressure moving eastward from the
Great Lakes brings light snow or rain shower activity with periods
of MVFR cigs/vsby. May see a brief period of S-SW wind gusts 25kts
06-12z Monday in advance of approaching low pressure system.
00z Tuesday through 00z Wednesday...mainly VFR conditions
expected...but some MVFR possible in showers late Tuesday...mainly
across the Adirondacks/slk.