Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
1103 PM EDT Tuesday Mar 11 2014
low pressure will move from the Middle-Atlantic States tomorrow into
the Gulf of Maine tomorrow night. This storm is expected to
generate a large amount of precipitation with the majority of it
being in the form of snow. As the system moves into the Canadian
Maritimes on Thursday precipitation will come to an end. High
pressure then builds over the region and will remain in control of
the weather into the early part of the weekend.
Near term /until 6 am Wednesday morning/...
1100 PM...minor estf update to reflect current mesonet.
700 PM...minor estf update to reflect satellite trends as well as
generally calm before the storm tonight. Lingering west-northwest flow could
spit out a few shsn in the northern mountains however. Low temperatures will be on
the mild side...as clouds begin to work in from the developing
storm to the west.
Short term /6 am Wednesday morning through Wednesday night/...
all model guidance is in agreement that rapidly increasing warm air advection
aloft will saturate the column Wednesday morning...from west to east. Strong
isentropic lift along the developing highly sloped fnt should
allow precipitation to quickly become steady after onset. Expect that by
noon the majority...if not all...of the County warning forecast area will have precipitation
Initially wet bulb cooling should allow most precipitation to fall as snow.
Gradually the boundary layer will warm...so that southern zones and the
immediate coastline may change to rain for a time. There is plenty
of cold to the north...but high pressure is not in an ideal location for
strong ageostrophic drainage to the coastal plain. So temperatures may
not slip back below freezing...even as low pressure strengthens to the
S. As a result surface temperatures will have a large role to play in the
ultimate snfl totals for these southern and coastal areas.
Aloft American model guidance is in good agreement that melting
layer will push northward to roughly the lakes region of New Hampshire into kizg
and eastward to just north of kpwm. 11/12z European model (ecmwf) remained warmer aloft...as
has been the case the last several runs. Mixing would push well
into the White Mountains if this were the case. What is true of all
guidance is that warmth aloft is maximized above 800 mb. With warm
nose that high...and highly sloped fnt yielding deep sub-freezing
layer below...soundings lean more towards sleet than freezing rain. Used a
blend of European model (ecmwf) and nam12 mixing heights to produce weather grids. The
result is all snfl for the mountains...mix with mainly sleet through
central and coastal zones...with rainfall for the immediate coast and
parts of southern New Hampshire. Based on 12z radiosonde observations...model guidance did
initialize with a slight warm bias. This trend will have to be
monitored...especially at 00z...for corrections in overall
This leaves a high confidence snfl forecast for northern zones...where
heavy snow will total between 12 and 20 inches by Thursday morning. Along
the transition zones towards the coast...confidence is much lower.
However...generally 4 to 10 inches is possible...along with
significant amounts of sleet. Near the immediate coast S of kpwm...2
to 4 inches along with sleet and some freezing rain will also have
significant impacts on travel. Given the impacts of combined
snow...sleet...and freezing rain have upgraded the remaining winter storm
watches to warnings...including coastal Cumberland County.
Rockingham County and coastal York will have winter weather advisories
in effect...as warm air will penetrate farther inland in these
Late Wednesday cold fnt quickly collapses towards the coast. Temperatures
should quickly fall from near freezing to the teens in a few
hours. This will allow stronger winds aloft to mix down to the
surface...with occasional gusts to 35 or 40 miles per hour. It will also allow any
liquid to freeze quickly. This flash freeze could prolong slippery
conditions well into Thursday morning.
Long term /Thursday through Tuesday/...
low pressure moving from the Gulf of Maine into the Canadian
Maritimes will generate gusty north to northwest winds across the
area. Precipitation will come to an end from south to north across
the County Warning Area as the day progresses. Cyclonic flow and northerly winds
will keep mostly cloudy skies and snow showers in place over the
mountains throughout the day on Thursday.
High pressure begins to build over the region Thursday night and
will keep things rather quiet for Friday. Low pressure passing
well to the north of Maine on Saturday will drag a weak cold front
across northern New England with a slight chance for some
precipitation. High pressure then makes a return on Sunday and
will remain in place over the eastern third of the nation through
Aviation /03z Wednesday through Sunday/...
short term...VFR conditions last into the overnight before
gradually going downhill Wednesday morning. Snfl moving in from the west
around 12z will bring widespread IFR or lower conditions.
Gradual improvement is expected by Thursday morning...though -sn will
linger into the afternoon...with areas of IFR at times. Winds will
also increase from the north as cold air moves in after midnight
tomorrow. Occasional gusts at or above 30 kts are possible.
Long term...IFR conditions in snow on Thursday will slowly improve and
become VFR by Thursday night. VFR conditions will remain in place
through Friday before a weak cold front moves across the region on
Saturday. This system may cause some areas to drop to MVFR.
short term...low pressure moving into the Gulf of ME Wednesday will
gradually increase northeasterly winds over the waters. Gale warnings
posted for all waters beginning Wednesday evening...continuing through the
overnight as flow turns northwesterly.
Long term...strong northwest winds behind tomorrows system will
gust over the waters on Thursday. Once the low begins to move into
the Canadian Maritimes Thursday afternoon and evening the winds
ME...Winter Storm Warning from 8 am Wednesday to noon EDT Thursday
Winter Storm Warning from 11 am Wednesday to noon EDT Thursday
Winter Weather Advisory from 11 am Wednesday to noon EDT
Thursday for mez023.
New Hampshire...Winter Storm Warning from 8 am Wednesday to noon EDT Thursday
Winter Weather Advisory from 8 am Wednesday to noon EDT
Thursday for nhz013-014.
Marine...Gale Warning from 8 PM Wednesday to 8 PM EDT Thursday for