Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
1030 PM EDT Sat Sep 20 2014
a warm front tracks northeast across the area tonight. A cold
front will quickly follow from the west late Sunday into
Monday...and will provide a round of showers and maybe even an
isolated thunderstorm. A second cold front will cross the area
Tuesday followed by high pressure for the remainder of the week.
Near term /until 6 am Sunday morning/...
1030 PM update...have updated the forecast to account for minor
trends in observational data...mainly sky cover. Skies continue
to clear out and should be the trend for the next few hours. After
3 am...expect coastal stratus and fog to develop along with
a widely scattered showers.
7 PM update...have updated the forecast for minor adjustments
based on latest trends in observational data. This evening should
continue to be mostly cloudy but dry. Well after
midnight...positive Theta-E advection in the low levels
strengthens as k-indices rise and showalter indices drop to around
zero. Showers are therefore expected to develop late at
night...with an isolated rumble not out of the question.
12z sounding noted SW flow and a saturated layer from about 925 to
800mb this morning. Forecast sounding show this layer continuing
tonight as warm air advection continues and moist tropical air pushes into the
region. Expecting cloud cover and much warmer temperatures
tonight...with almost all areas staying in the 50s overnight.
Moisture advection should also help in the formation of fog over
the waters and along coastal zones.
Short term /6 am Sunday morning through Sunday night/...
models are having a tough time handling the wave/low pressure developing
off the Carolinas. The wave/low will move northward tomorrow and
pass very close to the 40/70 benchmark. Models all agree that this
system will not supply much in the way of rainfall to the area but
the tropical airmass will be noted as precipitable water values will increase to
the 1.7 range tomorrow...which is about 2 Standard deviations
above normal values. This moisture combining with a weak leading
short wave will be enough to maybe bring some light rain and
drizzle to the southern forecast area by tomorrow morning. A cold
front will approach the area tomorrow afternoon into tomorrow
evening. This front will kick off scattered showers and possibly a
thunderstorm...however...even with the increase in low level
moisture the instability is looking modest at best. The best
chance for a storm will be in the western forecast area...where
breaks of sun and heating is most likely to occur.
Long term /Monday through Saturday/...
a cold front will be moving offshore and into eastern Maine
Monday morning. Skies will clear out over the interior and
along the coast as downsloping westerly winds develop behind the
boundary. Clouds and showers will diminish and eventually just
remain over the higher terrain by early afternoon. We should see a
decent temperature gradient from north to south due to this with
upper 50s north to lower 70s along the coast.
The colder air begins to dip down Monday night into Tuesday
morning and is entrenched along the green and White Mountain
basins. There will be a few locations in the lower 30s but the
majority of sites should hover in the middle 30s. This is partly due
to the proximity of the jetstreak and some lingering middle and high
level cloudiness. Elsewhere temperatures will be in the lower to
middle 40s. Another reinforcing cool front moves through during the
day Tuesday...but the source is well north and will result in
little more than a wind shift.
The remainder of the week looks pleasant and precipitation free
as high pressure dominates the weather at the surface and aloft.
High temperatures will transition into the 60s and 70s by
Wednesday and remain there through at least Saturday. High
pressure will promote clear skies...light winds...and quickly
dropping temperatures in the 30s and 40s each night.
Aviation /23z Saturday through Thursday/...
short term...increase in low level tropical moisture will advect
fog and low stratus into the area tonight. This will cause IFR
conditions from midnight through tomorrow morning. Ceilings and
visible should then increase to MVFR and VFR conditions before a cold
front drops through the region late tomorrow afternoon and into
Long term...MVFR or briefly lower conditions Monday
morning..mainly in mountain terminals in showers and fog. Fog will
again be possible in mountain terminals Tuesday morning. VFR will
short term...marginal Small Craft Advisory conditions with gusts around to 25
knots and seas around 5 feet are expected overnight on the ocean
waters. Have therefore issued a Small Craft Advisory for tonight into Sunday.
Long term...a Small Craft Advisory may be needed Monday into
Tuesday morning as a cold front crosses the waters.
Marine...Small Craft Advisory until 3 PM EDT Sunday for anz150-152-154.
Near term update...mle