Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
400 PM EDT Monday Mar 10 2014
low pressure will move southeast out of Canada tonight...crossing
northern New England late tonight and early Tuesday before heading
into the Maritimes Tuesday afternoon. An area of high pressure
moves through late Tuesday and Tuesday night. Low pressure will
track out of the southern Appalachians and toward the middle Atlantic
and southern New England coast on Wednesday before crossing into
the Gulf of Maine Wednesday night. This will provide significant
snow to much of northern New England with a period of rain along
the coast. Low pressure moves into the Canadian Maritimes on
Thursday with snow ending across New England and cold air being
pulled in behind it. High pressure ridges in for Friday before a
cold front crosses the region on Saturday.
Near term /tonight/...
models in good agreement with an upper level jet stream/vorticity
maxima cross northern New England tonight. This forces a surface
low to track southeast out of Canada...reaching northern New England late
tonight. This will spread an area of light snow across the
forecast area with the best chance across more northern and
eastern zones which will be more likely to be north of the surface low
track. The area of higher relative humidity and the vorticity maxima move
quickly through by daybreak with snow ending late from SW to NE
across southern New Hampshire and SW ME. This is a fast moving system with
light snow moving in quickly this evening/early tonight then
ending quickly late tonight or very early Tuesday.
The precipitation may mix with some light rain late across
southern New Hampshire and SW ME as the precipitation lets up and some warmer
air inches northward with the low passing north of southern New Hampshire and SW
ME. Snow accumulations of an inch or two across northern and
eastern areas with locally 3 inches possible while southern areas
mainly an inch or less. Based snow amounts on quantitative precipitation forecast of 0.20 north...
0.10 central and under 0.10 south per HPC quantitative precipitation forecast and using a 10 to 1
snow to water ratio. Lows range from around 20 far north to around 30
along the coast.
Short term /Tuesday through Tuesday night/...
the surface low moves quickly out of northern New England early
Tuesday as the upper level system also quickly moves into the
Maritimes. This allows drier weather to move in on a west northwest flow.
Some clouds and maybe a few flurries may linger in the
North/Mountain zones with the upslope flow. Temperatures don't
drop much behind this system as 850 mb temperatures stay close to
0c over southern most New Hampshire and around minus 5c over northern areas.
Highs will range from 30s to around 40 north to 40s S with 50
degrees possible over our most southern zones. A weak area of high
pressure moves in late Tuesday and Tuesday night giving US fair
dry weather. Temperatures will cool mostly into the teens north and
Long term /Wednesday through Monday/...
trough digging into the central United States will strengthen a
surface low over the southern Appalachians into the middle Atlantic
on Wednesday. Models are in fairly good agreement on the track
of low pressure from the New Jersey coast to Cape Cod and into the
Gulf of Maine on Wednesday night before moving into the Canadian
Maritimes Thursday. This track puts the Sweet spot for heavy
precipitation directly across the forecast area... with an inch or
more of total melted precipitation likely for much of the area.
Biggest question will be precipitation type particularly in
southern areas and along the coast as warm air gets pulled into
Current expectation is that precipitation will begin moving into
the region during the day Wednesday. Temperatures initially start
off warm... with middle to upper 30s widespread. But as precipitation
begins temperatures will fall into the low 30s and likely start as
snow just about everywhere. As low pressure tracks northeastward
along its warm front toward Cape Cod... a battle will be raging
between cold air being drawn in from the north (enhanced by low
level cold air damming) and warmer air pushing in from the east. A
coastal front will set up near the coastline... with a transition
to rain occurring on the coastal side of this front Wednesday
evening. Unfortunately this battle is occuring during the time of
heaviest precipitation from Wednesday afternoon until midnight.
Warm air aloft above the surface coastal front may also be enough
to change snow to sleet for parts of the coastal plain and
southern New Hampshire... limiting snow totals there a bit. But as
low pressure moves east... cold air will be drawn in behind it at
all levels... changing precipitation back to snow for all areas
Confidence is highest that precipitation will stay all snow in the
foothills and mountains... perhaps the biggest snowstorm of the
season for these areas. For much of the coastal plain there could
be some sleet mixing in from time to time... cutting down on total
snow amounts a little bit. But along the immediate coast of
southwest Maine and southeast New Hampshire the transition to rain
could drastically limit totals there. Current watch headline will
remain in place... though there is still a lot of uncertainty on
totals from the coast into the adjacent coastal plain areas. Will
split the west-southwest product into two groupings to better describe the
threats for each area.
As the low moves away on Thursday... snow will end from west to
east. But a cold northerly flow will keep temperatures very
cold... with northern areas staying in the teens and
southern/coastal areas only rising into the low 20s before
possibly falling through the day. It will be a cold night Thursday
night with temperatures in the single digits above and below zero.
Cold high pressure crests across the area on Friday with
temperatures warmer but still likely staying below freezing. Low
pressure tracking through Quebec will push a cold front toward New
England Friday night and Saturday. This will allow temperatures to
warm back up into the 40s again on Saturday before the front
arrives. Some rain/snow is possible as the front moves through but
this does not look like a significant precipitation maker. Cooler
air moves in behind this low although temperatures on Sunday will
still be in the middle/upper 30s on the coastal plain due to
Aviation /18z Monday through Saturday/...
short term /through Tuesday night/...VFR /except locally MVFR
ceiling middle coast of Maine affecting rkd/ lowers overnight as an
area of light snow moves through. Ceiling/visibility lower to MVFR
southern areas and MVFR/IFR more northern and eastern areas that
will be mostly north of the surface low track.
Long term...snow moves into the area on Wednesday... bringing
conditions down to IFR or lower. Should see mainly rain at psm.
May see sleet mix in at con/Aug/rkd and a change to rain at
pwm/rkd. Precipitation changes to snow again by Thursday morning
before ending during the day Thursday. Conditions improve as the
day GOES on and should see VFR again by Thursday evening lasting
into Saturday morning.
short term /tonight through Tuesday night/...winds and seas stay
below Small Craft Advisory levels through Tuesday night.
Long term...as low pressure moves through the Gulf of Maine
Wednesday night... east/northeast winds will strengthen. Advisory
level winds are likely and gales are possible. Cold advection
behind the low on Thursday could also bring significant gusts
possibly reaching gale force. High pressure brings calmer winds by
ME...Winter Storm Watch from Wednesday morning through Thursday
morning for mez007>009-012>014-018>022-025>028.
New Hampshire...Winter Storm Watch from Wednesday morning through Thursday
morning for nhz001>010.
Long term... Kimble