Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Gray ME
430 PM EDT sun may 3 2015
high pressure offshore will bring a southerly flow over the
northeast and transport warmer air into the area. A weak cold
front will cross the area Monday night and early Tuesday with
scattered showers and thunderstorms. A moisture starved cold
front will cross the area Wednesday. A ridge of high pressure
follows for late Wednesday and Thursday. A developing onshore
flow and an approaching warm front will make the weather
increasingly unsettled for Friday. The warm front should lift to
the north of the area by Saturday followed by a trailing cold
front late Saturday night and Sunday.
Near term /until 6 am Monday morning/...
issued a Fire Weather Watch after talking with New Hampshire forestry service
and surrounding offices. This brings US in line with the
surrounding offices. We are still short of criteria but dew points
may be lower than forecast.
afternoon showers are pretty weak and likely having difficulty
producing any appreciable rain at the surface due to significant
dry air in the low levels. These should quit forming over the next
hour or two and the remnants will dissipate as the evening GOES
on. Biggest forecast question is whether marine layer will reform
and push onshore again tonight. Satellite imagery this afternoon
shows that the offshore marine clouds fully dissipated today and
thus it may be more difficult to regenerate tonight. Warmer
temperatures along the coast this afternoon may also contribute to
a more difficult cloud/fog formation. With this thinking... did
not hit up the clouds and fog too much tonight. Should drop into
the 40s for most of the area tonight with a few 30s in the
Short term /6 am Monday morning through Tuesday/...
Monday will be the warmest day of the year so far with many areas
cracking the 80 degree mark. A little cooler near the coast where
a sea breeze will be prone to developing but even Portland should
reach 70 degrees.
Strong mixing with the daytime heating will bring really dry air
to the surface again Monday. Model dew point forecasts continue
to be pretty atrocious this time of year with the difficulty in
accounting for the mixing. Have undercut afternoon dew points by
several degrees to account for the mixing away from the coast but
even this might not be low enough. This dry air will spell fire
weather concerns detailed in the fire weather discussion below.
Cold front begins moving across the forecast area overnight. Moist
advection ahead of the front will likely lead to clouds and warmer
overnight temperatures. Remnant convection from Quebec will likely
move southeast into the border regions before dissipating as the
front moves across the forecast area overnight. Any showers will
not arrive until after dark and this along with the lack of
substantial forcing and significant moisture will make the threat
of thunderstorms fairly low.
By Tuesday morning the front will be nearing the coastline and
sagging slowly southward through southern New Hampshire. Could see
showers trying to develop along the front in the late morning or
early afternoon over southern New Hampshire before the front
finally pushes fully south into Massachusetts. Otherwise it will
be a dry and warm day again across the region. Offshore flow will
prevent much of a sea breeze so Tuesday could be the warmest day
Long term /Tuesday night through Sunday/...
the models are in general agreement on the long wave pattern
for the entire forecast period. We begin the period with west-
northwest flow aloft in advance of an upper ridge centered across
the western Great Lakes. An impulse embedded in that flow will
drive a weak moisture starved cold front across the area
Wednesday. High pressure then builds by to our north late
Wednesday through Thursday. The flow turns onshore by Thursday
night...and with an upper ridge building to our west...a warm
front develops across the region Thursday night and Friday.
Light overrunning precipitation and some drizzle and fog is
possible Friday mainly over northern and eastern sections of the
forecast area as the front presses north. During the past
day...the models have come around to a solution that drives the
warm front to our north by Saturday followed by a trailing cold
frontal passage Saturday night/early Sunday. Unfortunately...the
front then stalls out and provides the Prospect of clouds and
unsettled weather for the tail end of the weekend and early next
Aviation /21z Sunday through Friday/...
short term...afternoon showers dissipate early this evening.
Should see VFR conditions and nearly calm winds for most of the
area. The marine clouds and fog are less likely to form tonight
than last night but cannot rule it out completely. Best chance
would be at Rockland. If this does form it will dissipate again in
the morning Monday leading to VFR conditions again areawide.
Friday...scattered MVFR possible in showers.
short term...light winds over the waters today but becoming more
southwesterly and strengthening Monday evening. Could potentially
see gusts to 25 knots Monday night over the outer waters before a
cold front moves through.
Wednesday evening - Thursday morning...small craft winds and seas
Friday...small craft winds and seas are possible.
afternoon heating on Monday will lead to good mixing and pull down
significantly drier air from aloft. Afternoon humidity levels fall
below 25 percent for much of the area but wind speeds will only
reach around 10 or 15 miles per hour. Both of these criteria are one category
below red flag warning conditions but there is some concern that
dry air could be more intense than forecast. Therefore a watch has
been issued and we will continue to monitor conditions.
ME...Fire Weather Watch from Monday afternoon through Monday
evening for mez007>009-012>014-018>021.
New Hampshire...Fire Weather Watch from Monday afternoon through Monday
evening for nhz001>013-015.