Scientific Forecaster Discussion
fxus61 kgyx 121108
Area forecast discussion
National Weather Service Gray ME
608 am EST Thu Dec 12 2019
high pressure will build in and then cross the region today
with fair weather. Low pressure will track over western New
England Friday night through Saturday night bringing mainly
rain, and possibly heavy rain to the area. Precipitation may
briefly start as a wintry mix before quickly changing to rain
except in the mountains where the highest elevations may see
prolonged wintry precipitation before changing over. Windy and
colder conditions follow Sunday into Monday. Another colder
system will approach New England Monday night into Tuesday that
may bring more wintry precipitation.
Near term /until 6 PM this evening/...
6 am update...little change to the going forecast other than to
adjust temperatures and sky cover based on latest observational
data. Wind gusts continue to diminish.
Cold air advection with brisk winds continue in the wake of a
cold front early this morning. Gusts up to 30 mph will subside
early this morning as high pressure continues to build on in.
Increasing subsidence will allow for mountains snow showers to
shut off this morning also. Otherwise, a mostly sunny and cold
day for most locations today with some increasing clouds likely
late this afternoon as warm air advection strengthens in advance of the next
Short term /6 PM this evening through 6 PM Friday/...
fair weather is expected tonight with dry weather. However,
there should be a good amount of mid and high clouds around in
association with the increasing warm air advection pattern. This should limit
Warm air advection continues Friday, with low level moisture
increasing from the south during the day. This may allow for
some drizzle and freezing drizzle during the afternoon hours.
The coldest temperatures are expected to be in the mountains and
foothills where readings around or just below 32 degrees are
expected. This is where the best chance of light ice accretion
Long term /Friday night through Wednesday/...
late Friday night into early Saturday morning, ridging will be
moving offshore as southern stream short wave energy moves
northeast along the East Coast. Increasing southerly flow will
pump high Theta-E air northward ahead of deepening low pressure.
At the surface, a well-defined warm front associated with the
surface reflection will help to increase lifting for ascent as
it arrives overnight. As this happens stratiform precipitation
will be increasing across northern New England, with near total
coverage by the morning.
Colder air will be weakly dammed across northern New Hampshire and the
western ME mountains initially, creating a chance for a wintry
mix early on before warmer air advances north. Farther south
rain will be falling. By Saturday morning almost the entire area
will have changed over to rain, and with pwats well above
normal and ample forcing, expect moderate to even heavy rain at
times Saturday and Saturday night. A this time it looks like
1-2" of rain will fall over the weekend. Snow amounts look
light...although some additional accumulations are likely Sunday
as colder air arrives and the mountains change back over to
Warmer temperatures, heavy rainfall, and a ripe snowpack will
all contribute to rises in area rivers with this event. Also
agree with wpc's day 3 excessive rainfall outlook citing higher
rainfall totals near the coast and higher rainfall rates
possibly leading to pockets of flash flooding.
The system accelerates as it becomes more negatively-tilted, and
the center of the low will pass to our west Saturday night. The
main short wave trough swings through on Sunday. Sunday will be
especially windy with a tight pressure gradient in place, with
gusts in the 25-35 mph range.
By Monday highs will be struggling into the lower 20s north to
low to mid 30s south. Another system moving up the East Coast
will affect New England around next Tuesday. The storm will stay
south of US, and with cold air already in place, it looks like
snow for the majority of our area. Another shot of reinforcing
cold air arrives behind this system.
Aviation /11z Thursday through Monday/...
short term... VFR will prevail through tonight. Gusty northwest winds
will diminish by 12z today. Otherwise, mostly VFR on Friday,
although MVFR conditions are expected to develop by late
afternoon as low level moisture increases. Some light drizzle
will be possible as well, with pockets of freezing drizzle in
the mountains and foothills.
Long term...low pressure will track over western New England
bringing widespread rain to the area Saturday into Saturday
night with MVFR likely. The main precipitation type will be rain
with snpl or -fzra mixing in at the higher elevations. Conditions
will improve to VFR Sunday into Monday. Winds will be quite
gusty Sunday with gusts around 25 kts.
short term...gales have been downgraded to scas at this hour as
winds continue to diminish. Otherwise, some marginal Small Craft Advisory
conditions will be possible Friday afternoon off the midcoast of
Long term...scas or possible gales are likely by Friday night
into Saturday for the outer waters and possibly the bays. Winds
decrease Saturday night somewhat with the passage of a storm,
but a tight pressure gradient will bring winds back up to gales
over the outer waters and possibly the bays on Sunday,
decreasing to scas Monday.
low pressure tracking up the East Coast will bring 1 to 2 inches
of rain to the region Friday night into Saturday night. Recent
rain and mild temperatures have lead to many rivers in New
Hampshire running high into the 90th percentile for this time
of year. While much of the snowpack south of the mountains has
been decimated from recent warmth, nohrsc estimates show that a
ripened snowpack remains from the New Hampshire lakes region
southwestward towards the border with Massachusetts and Vermont. This snowpack,
although heavily reduced, will likely melt off with this system
and along with rainfall, will lead to flooding concerns for
rivers in central and southern New Hampshire. Farther north
into the White Mountains, snow followed by rain will likely
serve to moisten the snowpack leading to less runoff and
low pressure tracking to the west of the area Friday night
through Saturday night will bring strong onshore flow and
increasing near shore waves. Peak surge with this system is
forecast to occur a few hours after the mid-day high tide
Saturday and this with near shore waves around 5 to 7 feet may
pose some beach erosion and minor coastal flooding concerns.
Marine...Small Craft Advisory until 11 am EST this morning for