Area forecast discussion
National Weather Service Gray ME
303 am EDT Sat may 18 2013
Synopsis...
high pressure will move off the coast as a developing warm front
approaches from the southwest today through Sunday. Unsettled
weather can be expected next week as a series of disturbances
track eastward across New England.
&&
Near term /through today/...
the upper level pattern shows a cutoff low over the Maritimes with a
ridge to our west centered over the Great Lakes. This will result in
a northwest flow over New England which has an embedded weak short
wave/jet segment sliding southeast in this northwest flow into New England. At
the surface weak high pressure between the two upper level systems will slowly
shift offshore. This will allow winds to turn onshore during the
day...being enhanced by a developing sea breeze along the coast.
The upper level short wave/jet segment is accompanied by an area of
higher relative humidity which will translate into varying amounts of cloudiness
across the forecast area today. This feature may even trigger an
isolated -shra or two this afternoon as it moves into the region.
The GFS model is overdoing the chance of prcp and quantitative precipitation forecast for this event.
Will lower the chance of prcp down to slight chance and will use rfc quantitative precipitation forecast
which shows minimal amounts. High temperatures today will be tempered by
onshore flow...especially near the coast. Will use a blend of
met/mav MOS which is a compromise between the cooler met and
warmer mav. Expect highs in the 60s with around 70 possible over southern
interior New Hampshire and coastal Maine a little cooler...especially the
middle coast with highs topping out in the 50s. Also used a blend of
mav/met MOS for dew points and winds.
There will be some patchy frost in sheltered inland areas early
this morning with lows in the 30s...but will be very limited and
in areas where the growing season hasn't begun so no frost advection
needed.
&&
Short term /tonight through 6 PM Sunday/...
the upper level pattern doesn't change over the short term period as
the upper level short wave/jet segment in the northwest flow pushes off the
coast tonight. This brings the area of higher relative humidity offshore as well as
isolated -shra. However...a developing warm fnt, between the cooler air
associated with the upper level cutoff to our NE and the upper level ridge
to our W, will be spreading more clouds and possible -shra NE into the
forecast area on Sunday /mainly in the afternoon/. Again the GFS chance
of prcp and quantitative precipitation forecast appear overdone so have lower the chance of prcp
considerably and using rfc quantitative precipitation forecast which keeps amounts very low. A
blend of mav/met MOS was used for temps, dew points and winds.
The onshore flow increases on Sunday as the pressure gradient
increases between the high which strengthens off the coast and
the warm fnt that pushes in from the SW.
&&
Long term /Sunday night through Friday/...
the numericals are in basic agreement on longwave pattern through the
middle of next week. Initially the upper ridge builds through the
Midwest and Great Lakes which leaves the forecast area in west-northwest
flow into early next week. Thereafter...falling heights as the
ridge weakens and some degree of eastern trough emerges. With mean
jet axis overhead or nearby...the area for much of the period will
be unsettled as a series of disturbances travel eastward along a
boundary separating Summer-like warmth from early Spring chill.
In the dailies...unsettled weather can be expected next week as a
series of disturbances track eastward across New England.
&&
Aviation /06z Saturday through Wednesday/...
short term /through Sunday/...VFR today...tonight and early Sunday but
possibly lowering to MVFR at times in any isolated -shra. A slightly
better chance of MVFR ceiling/visibility in isolated to scattered -shra late Sunday.
Weak winds become onshore today and enhanced by a sea breeze along
the coast. Winds drop off tonight but onshore flow picks up again on
Sunday.
Long term...
Monday - Wednesday...areas of MVFR in showers.
&&
Marine...
short term /today through Sunday/...winds and seas will remain
below Small Craft Advisory levels. Light and variable winds become onshore as high
pressure moves off the coast today . Winds enhanced today from daytime
sea breezes. Southeast onshore flow continues tonight and increases on
Sunday as the pressure gradient increases as the high strengthens and
a warm fnt approaches from the SW.
Long term...
Sun night - Monday...small craft winds and seas are possible.
&&
Fire weather...
the fire weather danger will be fairly low for the next several
days as green up continues across the region. Relative humidity values will be
the lowest today but winds will be fairly light except for a
developing sea breeze along the coast which will also force relative humidity
values to increase there. Winds increase on Sunday but off the
ocean which will result in higher relative humidity values pushing inland. Isolated
-shra over the weekend may increase in coverage late Sunday. There
will be a better chance of -shra during the work week which will be
accompanied by fairly high relative humidity values.
&&
Gyx watches/warnings/advisories...
ME...none.
New Hampshire...none.
Marine...none.
&&
$$
