Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kgyx 180226 aab 

Area forecast discussion...updated
National Weather Service Gray ME
926 PM EST sun Nov 17 2019

high pressure will retreat into the Maritimes tonight. Low pressure
off the mid Atlantic coast will move north overnight and Monday,
spreading moisture into New England and resulting in a wintry
mix of precipitation types. Unsettled weather will continue
through the midweek with temperatures near seasonal norms.


Near term /through Monday/...
925 PM update...
precipitation has not really moved into our areas yet, but snow
showers have reached Portsmouth the last few hours. Temperature
and thus p-types still look consistent with the forecast at
this time. Adjusted a few areas for sky cover and dew point
discrepancies, otherwise forecast is on track.

640 PM update... minor changes to the forecast with some snow
moving into Portsmouth...otherwise no big changes to the
forecast. Very light echoes moving into Maine at this time.
Temperatures are on track.

Previous discussion...
at 19z a 1032 mb high was centered along the Maine/New Brunswick
border. GOES visible imagery showed low clouds had overspread
far southern New Hampshire as well as extreme southwest Maine in
the onshore flow. Otherwise skies were clear across the remainder
of the area. While temperatures have recovered into the 30s
today...where we're clear for much of the night temperatures
will nosedive in the dry airmass. Further south the low cloud
will keep US a bit warmer but still flirting with 32f overnight.
The onshore flow may generate some patchy drizzle/freezing
drizzle towards morning over far southern and coastal sections
prior to the arrival of any synoptic precipitation associated
with the ocean low.


Short term /Monday night/...
models have trended a bit slower with the ocean low and arrival
of precipitation with this system. I expect we'll see some light
freezing precipitation over coastal and southern areas by the
end of the morning commute just from the onshore flow and have
opted to issue an advisory with this package. The precipitation
from the ocean low arrives during the morning and gradually
spreads north and west. Quantitative precipitation forecast numbers have come down and i've
lowered potential glaze amounts as well. I'm concerned the cold
layer across the interior may be slower to erode and a bit
deeper than advertised by the models...resulting in more sleet
then freezing rain. I held on to advisories longest over northern
and western areas where light freezing rain potential should
linger the longest. Highs tomorrow should be in the mid and
upper 30s with a few coastal locations warming to the lower 40s
by afternoon. Areas along the international border should be
limited to lower 30s for highs. Tomorrow night the low crosses
the Gulf of Maine with colder air gradually settling back south
into the area behind the low. As the column cools off the
mountains and foothills are likely to see more sleet and maybe
wet snow. Elsewhere...rain should taper before the colder air


Long term /Tuesday through Sunday/...
as we head into the latter half of November the hemispheric
pattern remains quite consistent with the ridge over the West
Coast of North America generally holding strong. A few waves are
able to move through this, either over the top bringing a very
cold Arctic airmass as we say this weekend or undercutting
bringing coastal lows and moisture up from the south. The
combination yields a fairly active pattern through the next week
or so.

Tuesday the coastal low which brought US mixed precipitation is
out of the way into the Maritimes leaving US with some
lingering clouds and nwly flow. Showers and clouds will both
decrease in coverage throughout the day, although blocked flow
will likely result in both lingering through the mountains as is

High pressure is able to build in for Wednesday and Thursday as to
our west a closed low develops over The Four Corners as 500 heights
climb ever higher into the Bacon. For US, this means a return
to near normal temperatures with highs in the 40s.

The next system looks to move into the region on Thursday into
Friday. Unfortunately that's also the time range at which the
predictability takes a sharp nose dive. We're waiting for anther
short wave to form up near the Yukon and works its way southwards
into the Great Lakes before becoming the source of possible
widespread light precipitation Thursday night into Friday.

The spread in the potential low locations couple with the
Continental airmass source leads to some healthy skepticism on
the forecast quantitative precipitation forecast amounts getting realized and pops have been
lowered somewhat to reflect the potential for a swing-and-a-miss
to the north. Pop remains highest in the north where the
mountains will likely pull some precipitation out of the system
but the coastal plain is less certain. With the prolonged high
pressure and southerly flow through the middle part of the week
temperatures will be quite warm on Friday with highs in southern
New Hampshire reaching 50 degrees. Behind the warmth colder air
will move in from the Great Lakes with the next system with
light precipitation changing over to snow in the north.


Aviation /03z Monday through Friday/...
short term /through Monday night/...MVFR cigs southern and
coastal sections in onshore flow will gradually overspread the
remainder of the region south of the mountains overnight.
-Ra/-fzra with IFR conditions developing Mon btw 10 and 15z
southern and coastal areas and spreading north and west into
the remainder of the area by 17z. All but mountain sections
should transition to -ra aft 17z with -fzra/-pl for the
mountains. NE surface winds may gust up to 25 kt at coastal
terminal sites on Monday.

Long term... expect a gradual recovery from IFR to MVFR and
finally VFR through the day on Tuesday as the coastal low pulls
out. High pressure builds in for midweek with the VFR
continuing. Another storm approaching from the Great Lakes may
bring lowering ceilings as well as scattered showers for Friday.


short term.../through Monday night/...northeasterly winds strengthen
in response to the approaching ocean low, with gales for all waters
Monday. Winds decrease below gales Monday night as the low pulls
away to the northeast.

Long term...Tuesday through Thursday...
gales will diminish on Tuesday as low pressure moves off into
the Maritimes. High pressure will move over the Gulf of Maine
from Wednesday into Thursday. Another low will pass north of the
waters in the St. Lawrence on Friday bringing a chance of
scattered showers and more cold advection to start the weekend.


Tides/coastal flooding...
prolonged NE flow to gale force, along with building seas ahead
of the coastal low may result in splashover and minor coastal
flooding a few hours either side of the 3 PM high tide on
Monday, mainly south of Casco Bay. This is supported by snap-ex,
etss, and estofs models which continue to show a storm surge of
around 1.5 ft.


Gyx watches/warnings/advisories...
ME...Winter Weather Advisory from 7 am to noon EST Monday for
Winter Weather Advisory from 9 am to 4 PM EST Monday for
Winter Weather Advisory from 6 am to 10 am EST Monday for
New Hampshire...Winter Weather Advisory from 7 am to noon EST Monday for
Winter Weather Advisory from 9 am to 4 PM EST Monday for
Winter Weather Advisory from 6 am to 10 am EST Monday for
Marine...Gale Warning from 3 am to 10 PM EST Monday for anz150>154.


National Weather Service Glossary of Abbreviations