Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
409 PM EDT sun Apr 19 2015
a prolonged period of unsettled weather is expected this week
with widespread rain Monday and Tuesday, followed by on and off
showers through the weekend.
Near term /until 8 am Monday morning/...
as of 400 PM EDT Sunday...dry weather continues through most of
the overnight hours but will see clouds increase and lower
overnight ahead of next approaching system. A warm occluded front
will approach later tonight into the early morning hours. Min
temperatures will be coldest in the Northeast Kingdom where it takes the
longest for the clouds to reach there. Otherwise upper 30s to low
40s are expected for min temperatures.
Short term /8 am Monday morning through Tuesday night/...
as of 400 PM EDT Sunday...weather turns unsettled for most of the week
and into the weekend as a digging upper trough over the central
Continental U.S. Develops into a vertically stacked closed low and takes
residence over the Great Lakes. Aforementioned occluded front will
sweep across the region on Tuesday. Strong southeasterly flow
along the boundary will tap into rich Gulf moisture with precipitable waters
approaching 1" supporting moderate rainfall which could cause some
Hydro issues as snowmelt continues from deep snowpack across the
higher elevations. As expected...have raised a Wind Advisory as a
moderate to strong southeasterly downslope wind event will
materialize along the western spine of the Green Mountains and
portions of the Adirondacks Monday afternoon. Have also included
western Rutland County and LaMoille County where these areas
typically are also impacted by this type of event. Local 4km WRF
continues to show a strong 925-850mb jet moving across the area
Monday afternoon through late evening. Winds of 50-60kts at 925mb
over the favored downslope regions along the western slopes of the
northern peaks from Killington to Jay Peak. Forecast sounding
shows the low level inversion is just below 925mb so while not all
of these winds will mix to the surface still think we'll see
gusts in excess of 40mph and likely up towards 50mph.
Occlusion shifts through the region late Monday night into
Tuesday morning with a middle level dry slot developing over the area
Tuesday which should end the widespread precipitation. As the front
shifts through models are indicating a little bit of elevated
instability therefore have continued with mention of thunder as
previous forecaster added. For Tuesday through Wednesday region
will continue to be stuck under influence of meandering cut off
low pressure system.
Long term /Wednesday through Sunday/...
as of 333 PM EDT Sunday...extended period to be characterized by
below normal temperatures, precipitation chances and more clouds than
sun. Closed 500 mb low moves east out of Great Lakes at the start
of the extended period, moves across forecast area through
Thursday, and east of area from Friday Onward. Towards the end of
the extended period some model differences arise with European model (ecmwf)
maintaining a more compact closed off low over the Gulf of Maine
with a sharper ridge in the upper Midwest, while the GFS keeps the
ridge further west.
Best precipitation chances on Wednesday/Wednesday night in advance of the
low passage, and from Thursday on mainly diurnally driven. With
cold pool aloft, 500 mb temperatures as low as -32c Friday morning,
daytime heating will easily destabilize and kick off afternoon
convection. In addition, colder air aloft will affect precipitation type,
and snow or rain/snow mix possible mainly over higher terrain and
mainly overnight Wednesday night and Thursday night.
Temperatures...not really wild swings with little variation in temperatures
after initial cold air advection on Wednesday. Maximum temperatures limited
by cool airmass and plenty of cloud cover to inhibit sunshine, and
overnight lows also limited by same cloud cover. Highs 40s/50s
with lows in the 30s.
Aviation /20z Sunday through Friday/...
through 18z Monday...VFR clear the rest of the day with increasing
high clouds and wind toward morning. The main feature this
forecast period is wind becoming southeast overnight and
strengthening 09-12z timeframe. From 12-18z Monday expect winds
15-25 kts and gusts 25-35 kts. With southeast wind direction will
be downslope on western slopes of the Green Mountains and northwest
slopes of the Adirondacks. Frontal system will move into the
region after 15z and spread rain west to east with ceilings/visible
remaining VFR. Left low level wind shear out of this period as surface winds
increase in pace with winds aloft and about a 20 knots differential,
below the low level wind shear criteria. However will be a bumpy climb out and
approach 12-18z Monday.
Outlook 18z Monday through Friday...
18z Monday - 00z Wednesday...rain area to lift northeast during
the period with ceilings/visible remaining mainly VFR but some MVFR
possible in rain showers. Gusty south-southeast winds to continue during this
period with gusts 35-40 kts possible mainly in Rutland. Low level wind shear
00z Wednesday - 00z Saturday...broad upper trough moves into the
region and to remain in place through the rest of the week. Mainly
VFR ceilings/visible with scattered MVFR in rain showers. On Thursday some
snow possibly will mix in with rain shower mainly over higher
terrain sites..kmpv/kslk with cooler temperatures.
Vermont...Wind Advisory from 8 am Monday to midnight EDT Monday night
New York...Wind Advisory from 8 am Monday to midnight EDT Monday night