Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
951 am EST Tuesday Mar 3 2015
high pressure across the area will shift offshore this afternoon.
Low pressure will swing through southern Canada tonight trying to
push a warm front north across the region. As the low shifts to
our north...it will drag a cold front through the region late
Wednesday. High pressure will build in from the west Thursday and
crest over the region on Friday. A weak disturbance will drag
trailing warm and cold fronts across the region this weekend.
Near term /until 6 PM this evening/...
950 am update: update reflects no real changes. Previous forecast
looks perfect on all grids.
615 am...quick update to T/dew point based on current observation. Otherwise
forecast thinking has not changed all that much. Off hour model
runs sending mixed messages with 06z nam12 coming with more quantitative precipitation forecast
and 06z GFS coming in with less...but timing stays the same same
with bulk of quantitative precipitation forecast coming in 00-06z...but just a little later in
the eastern zones.
Previously...surface high passing to the S of the County Warning Area has finally
allowed winds to diminish and we will start the day with sunshine
which should linger through the morning. The middle to high clouds
roll in around midday as warm air advection kicks into gear aloft...in advance
of the next system. Details of the this system are addressed in
the short term section...but will start to see snow break out in
southern and western New Hampshire in the 4-6 PM timeframe...although bulk of precipitation
will hold off until after sunset.
Temperatures today will warm with the sun this morning and then more
slowly this afternoon beneath the clouds...but increasing S flow
this afternoon should keep temperatures slowly moving upward through the
afternoon...rising to the low-middle 20s in the north and upper 20s to
near 30 in the S.
Short term /6 PM this evening through 6 PM Wednesday/...
main core of this system with deeper surface low and 500mb closed low
will remain well to our north and west...but broad area of strong warm air advection and
isentropic lift will move through the County Warning Area from SW-NE
overnight...and mostly focused on the 00-06z time period. So bulk
of the snow will hit this evening into the Post-midnight hours.
Could see some brief heavier bursts of snow in this time frame.
The SW winds away from the coast will have a hard time mixing to
the surface overnight...and although temperatures will be rising...will likely
be stuck below freezing...and with above freezing air moving
aloft...could see a bit of freezing rain as the precipitation ends in the
pre-dawn hours...although this would be very light...and limited
to southern New Hampshire and SW ME /York and southeastern Cumberland counties/. A
widespread 3-5 inches look reasonable given quantitative precipitation forecast of a quarter to
just under a half inch. In all but northern and eastern...ratios will start
in the 13-15 to 1 range...but will get closer to 8-10 to 1 as the
night progresses...so this will be a wetter snow than most of US
are used to this winter...and could lead to slight lower amts in
S New Hampshire as well. Also of concern is the 00z reg CMC...which has
noticably lower quantitative precipitation forecast.
Once we break out into the warm sector Wednesday morning a breezy west-SW
flow will allow temperatures to rise nicely into the 40s across most of
the County Warning Area...with even the mountains seeing upper 30s...and breaks of sun
outside the mountains midday and afternoon.
Long term /Wednesday night through Monday/...
in short...a continuation of below normal temperatures but no
significant precipitation events. The models are in general
agreement on the long wave pattern well into next week. The
western ridge gradually flattens and moves onshore into the
western half of the Continental U.S....while we see lingering trofiness here
in the east and below normal temperatures...punctuated by periodic
brief warm ups. We begin the period with a surface front stalled
just to our south and east. We'll be on the northern periphery of
the cloud shield...but expect any measurable precipitation to
remain to our south. There could be a few upslope flurries in the
mountains...otherwise a dry day on Thursday as an upper impulse
races east across the area. High pressure builds to our south
Thursday night and Friday. The next impulse approaches the area by
Saturday with an associated cold front to cross the region early
Sunday. The next impulse and cold front arrive for Monday and
Aviation /15z Tuesday through Saturday/...
short term...VFR through most of the day...but conds fall to IFR
around sunset or early evening in snow...and will stay there
through tonight...with improvement back to VFR on Wednesday.
Thursday and Sat...scattered MVFR in mountain snow showers.
short term...wind diminishing quickly during the pre-dawn...and
will be light through most of the day as they shift south-southwest and
increase. Will probably need Small Craft Advisory tonight into Wednesday.
Thursday...small craft winds and seas are possible.
Sat...gale force winds are possible.
ME...Winter Weather Advisory from 7 PM this evening to 7 am EST
Wednesday for mez007>009-012>014-018>028.
New Hampshire...Winter Weather Advisory from 4 PM this afternoon to 7 am EST
Wednesday for nhz001>015.