Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
345 am EDT Sat Mar 28 2015
low pressure will pass southeast of Cape Cod today and south of
Nova Scotia tonight. A lingering trough of low pressure will allow
for some light snow today. High pressure will build in for Sunday.
Weak low pressure will pass over or north of our region later
Monday and Monday night. Weak low pressure is expected to pass
south of New England Tuesday night into Wednesday followed by high
pressure into Thursday. A storm system may affect New England late
Near term /until 6 PM this evening/...
low pressure will form well south of Long Island New York today and
move well southeast of Nova Scotia by this evening. Strong upper
level low pressure moving over New England today will aid in a
weak low level trough of low pressure to linger across the region
today. This trough will induce some light snow...perhaps mixed
with a little light rain at times at lower elevations today.
It appears as though the main forcing for ascent and best
moisture advection with this feature will be across southern New
England and this is where we expect the highest quantitative precipitation forecast to be.
However...southern and central New Hampshire as well as portions of
southernmost Maine may see it snow just hard enough for some
Current thinking is that the monotonic region of New Hampshire
stands the best chance at picking up 1 to 3 inches of snow due to
elevation and proximity to best convergent zone. The sun angle is
quite high this time of year so it will take a decent intensity to
allow the snow to stick effectively and accumulate outside of any
narrow heavier bands of snow that develop.
Since this is a mesoscale-driven event...it will have to be
nowcasted through the morning into the afternoon hours and
snowfall amounts changed accordingly. However...the upshot is that
it is expected to be light for most everyone but a few locations
may see a few hours of heavier snowfall. Across the far northern
and eastern zones...not much of anything may fall.
As for temperatures...they should be in the lower to middle 30s
today...colder in the mountains. Winds will be gusty from the
Short term /6 PM this evening through 6 PM Sunday/...
any light precipitation is expected to rapidly come to an end this
evening...if not late this afternoon. Cold high pressure builds
in tonight with lows well below normal.
Warm air advection regime gets going on Sunday so we are expected
temperatures to rebound to at least the lower 40s under plenty of
Long term /Sunday night through Friday/...
model guidance remains consistent with the theme through the
extended. Broad trough will exist over the eastern Continental U.S....meaning
generally near to below normal temperatures for the northeast. The Silver
lining for those eager for Spring is that the pattern doesn/T seem
conducive for sustained cold but rather transient shots of colder
The first of which arrives Monday from the west. Precipitation will be
light...but expect plenty of rain or snow showers will be around during
the day. Westerly flow will keep shsn going in the mountains into
Tuesday...before ridging brings an end to any precipitation. It is quickly
followed up by another northern stream wave...but model guidance is
more focused on keeping that S of our area. Beyond that time frame
confidence is low...as these fast moving...compact shortwave troughs are
difficult for nwp to handle this time of year. These timing an
evolution differences lead to solutions like the GFS being very
progressive with the next wave by late in the work week. Or
conversely the stronger wave could delay like the European model (ecmwf) and arrive
over the weekend.
Again with temperatures averaging near to below normal at least some snow
will remain in the forecast with any of these systems.
Aviation /07z Saturday through Wednesday/...
short term...variable conditions in light snow or a rain/snow mix
at the coast are expected today. Conditions will be VFR at
times...but later this morning into the early afternoon
hours...conditions are expected to become IFR at times. VFR
conditions return tonight right through Sunday.
Long term...VFR conditions will give way to widespread MVFR as a
cold front approaches from the west. Rain and snow showers will cross the
area Monday...with lingering upslope shsn for khie through much of the
day and overnight. Gusty westerly flow and improving conditions are
expected Tuesday and Wednesday. There is low confidence in precipitation across southern
New Hampshire as another weak low pressure passes S of the region.
short term...Small Craft Advisory for the bays today for wind gusts around 25 knots.
Small Craft Advisory for the ocean waters through Sunday initially for winds
today...then probably just seas at or above 5 feet tonight into Sunday.
Long term...with trough hanging around the eastern Continental U.S....the waters
will be susceptible to continued shots of colder air. These cold
fronts will bring with them likely Small Craft Advisory conditions.
Marine...Small Craft Advisory from 7 am this morning to 6 PM EDT this
evening for anz151-153.
Small Craft Advisory until 6 PM EDT Sunday for anz150-152-154.