Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
720 PM EDT Friday Apr 24 2015
a low pressure area at the surface and aloft over the Canadian
Maritimes will keep the north country under cyclonic flow through
this weekend with a chance of rain or snow showers and below
Near term /until 6 am Saturday morning/...
as of 715 PM EDT Friday...going forecast in good shape. Cloudy skies
and mainly dry conditions across the area at this time...with just
a few mountain flurries. A few minor adjustments to hourly temperatures
for this evening...otherwise no changes at this time.
cloudy skies will persist over the north country overnight with a
chance for some rain or snow showers. Gusty northwest winds
combined with the cloud cover will help to keep temperatures up
overnight...so have gone a few degrees higher than MOS guidance
for min temperatures overnight.
Short term /6 am Saturday morning through Sunday night/...
as of 403 PM EDT Friday...model guidance showing more moisture
rotating southwest from northern Maine and the Canadian
Maritimes...so have gone with chance probability of precipitation for rain and snow
showers on Saturday...with snow showers mainly over the higher
elevations. 850 mb temperatures will not be as cold as today...so
expecting high temperatures on Saturday to be warmer than
today...but still looking for temperatures mainly in the 40s with
some temperatures around 50 in some valley locations. Have gone
below MOS guidance for maximum temperatures on Saturday and have
leaned toward the cooler ensemble MOS guidance for maximum
temperatures on Saturday.
The region will remain under cyclonic flow through Sunday from the
low over the Canadian Maritimes...so have chance probability of precipitation from
Saturday night through Sunday night for rain or snow showers
(mainly elevation dependent for the snow showers). MOS guidance
again looks too warm for maximum temperatures on Sunday given expected
cloud cover and chance for showers...so have gone below MOS
guidance by several degrees for maximum temperatures on Sunday.
Long term /Monday through Friday/...
as of 339 PM EDT Friday...early next week the closed upper level
low will finally be showing signs of exiting the region as a
Midwest upper level ridge will start building into the region. As
the upper level low rotates around on Monday it will combine with
a weak surface shortwave that will retrograde back over New
England bringing enough low to middle level moisture that the
persistent northwest upslope flow will bring a likely chance for
some rain showers across the area. At the summits there will
likely be a mix of rain or snow showers but that should only
really be in areas above 2500 feet.
Then Tuesday the short wave ridge will build into the region
brining about a welcomed change to the pattern with dry air moving
into the low levels shutting down shower potential over the middle
week. Late in the week on Thursday/Friday an upper level trough
will move into the middle Atlantic region which may bring a chance
for some rain showers. The problem is confidence is low in how
exactly the situation will unfold. The models diverge in their
respective solutions for how the surface low will develop and
there has been poor run to run consistency from the 00z to 12z
runs for each of the systems. The latest guidance points towards a
low pressure system that will become a fish storm and push well
east of the benchmark affecting only mariners. As such I went with
a blend of the available suite of long range guidance and
currently only have chance to slight chance probability of precipitation out at the end of
Concerning temperatures we will remain below normal through the
early part of the week with highs in the upper 40s to low 50s and
gradually warm under the ridging to near normal in the upper 50s
to low 60s in the valleys. Then as that upper level trough slides
in late in the week we will turn slightly colder trending back
down about 5-10 degrees into the low to middle 50s. Overnight lows
will largely be in the 30s to low 40s with the summits in the
upper 20s through the period.
Aviation /23z Friday through Wednesday/...
through 18z Saturday...primarily VFR through 00z Saturday under a
broken-overcast skies except for mpv/slk where MVFR ceilings will prevail
through this evening. Similar MVFR ceilings will set in at
btv/mss after 09z with the northern New York and Vermont sites
looking at 2500-3000ft ceilings overnight. Some
instability/wraparound moisture may bring rain/snow showers into
the northern half of the region...mainly across mountains after
00z Sat. Surface winds west-northwest 10-15 knots with some gusts up to 20
knots...easing up in the evening (after 00z) to 5-10 knots. Look
for northwest New York stations to see winds pick back up to 10-15 knots
by late Sat morning.
Outlook 18z Saturday through Wednesday... for the entire period
expect VFR with periods of MVFR (and possibly brief ifr) in
scattered rain showers during the day and rain/snow showers at