Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
316 am EST Sat Feb 28 2015
high pressure will build over the region today and will shift
offshore Sunday. Weak low pressure crosses the region Sunday
night...producing some accumulating snow...before moving into the
Canadian Maritimes on Monday. High pressure crosses the area
Monday night and Tuesday. Low pressure will move out of the Great
Lakes Tuesday night and will track northeast through the St
Lawrence Valley on Wednesday...bringing a round of mixed
precipitation to the area. A cold front follows Wednesday night.
High pressure builds in for the end of the week.
Near term /through today/...
high pressure will continue to build in from the west today
providing sunny skies and slightly warmer temperatures. Highs will range
from the upper teens to lower 20s north and middle to upper 20s
Short term /tonight through 6 PM Sunday/...
high pressure will crest over the region tonight. Good radiational
cooling will again send temperatures well below normal but not quite as cold
as Friday night. Colder mountain valleys will bottom out between
5 and 15 below. Temperatures in the south will be between 5 above
and 5 below. Expect some high clouds to filter in from the west
Clouds will be on the increase Sunday as high pressure shifts east
and a cold front approaches from the west. Have gone with low
chance probability of precipitation for southwest zones for late in the day but expect any
snow showers to be light and spotty. High temperatures will continue
below normal with readings ranging through the 20s to near 30.
Long term /Sunday night through Friday/...
500 mb pattern in the extended looks to remain mostly unchanged
through the extended although starting to see some seasonal
shifting of the jet back toward the pole. Also...some weaken in
both the upstream and downstream blocks will allow for some more
compact and progressive waves to develop which should help
transport some warmer into the northestern Continental U.S....at least for short
First on the Agenda is the fast moving wave that swings southeast out of
the cansdi9an prairie and then shifts into New England before
showing a bit of a negative tilt. Looks like the energy get S into
the base of this trough to late to deepen the surface low until it is
to our east...and so we will some snow late Sunday and mainly
Sunday night. Quantitative precipitation forecast looks to come in the around 0.20-0.25" fairly
evenly across the County Warning Area...and this should generally translate to
2-4" of snow given snowfall ratios of roughly 10-15 to 1. Highest
amts look to be in the southern third of New Hampshire...with lowest amts in
interior central ME. Snow should wind down in most places by
12z...with west winds picking up by midday and temperatures rising into
the low-middle 30s near the coast and in southern New Hampshire...and in the middle-
upper 30s in the north. Cold air filters in Monday night with lows
dropping back down between -5 and +10 f. Tuesday will be a little
colder as light flow becomes more onshore and clouds roll in from
the next approaching from the SW.
This next system will feature a 500mb closed low well to our northwest
and a few weak waves rotating around it and gradually flattening
out the ridge until the kicker wave come through on Thursday. This will
keep things unsettled from Tuesday night into the Thursday...although the
highest confidence in precipitation occurring for now Tuesday night into Wednesday
morning. It will start out as snow...but it will be accompanied by
decent SW flow aloft...and main chunk of high shifts off to the
east and does not entrench itself to the NE. This should allow
the warn air to move in fairly close to the surface. The question is
how long does the cold air dam at the surface hold on...given the deep
snowpack. Models are probably overdoing the warm to some degree.
Have included freezing rain in the mix on Wednesday. Still system is fairly
progressive and qpfs generally look to be in the half inch
ballpark...so not a big event for now.
Models do want to stall the front just to or S Wednesday night into
Thursday...and then develop a wave along the front. For now models
generally agree that most of any precipitation stays to our S...but have
kept the chance probability of precipitation in the forecast to cover this possibility.
Colder high pressure then builds in for Friday.
Aviation /07z Saturday through Wednesday/...
short term...VFR today through tonight. Areas of MVFR ceilings
developing late Sunday.
Long term...will likely see IFR ceilings/visible in snow for a good chunk of
Sun night at all terminals...but should see rapid improvement ot
VFR form SW to NE during Monday morning /except khie which will see
occnl MVFR-IFR in shsn through Monday afternoon. VFR holds Monday night and
Tuesday before another system moves in Tuesday and will produce flight
restrictions late Tuesday night into Wednesday.
short term...freezing spray advisory through late morning.
Long term...expect to need an Small Craft Advisory Monday after into Monday night in west
flow. May need gales for a period late Monday and Monday
evening...before winds diminish late Monday night. Small Craft Advisory may be needed
again in SW flow late Tuesday nigh and Wednesday.
Marine...freezing spray advisory until noon EST today for anz150>152.