Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Gray ME
1032 am EDT Monday Jul 6 2015
high pressure will crest across the region today before sliding
offshore. A return flow behind the high will transport warmer and
more humid air into the area Tuesday and Wednesday. A cold front
will bring a chance of showers and thunderstorms midweek. High
pressure follows for Thursday into the upcoming weekend.
Near term /until 6 PM this evening/...
sunny skies and a dry atmospheric column has resulted in a quick
warm up this morning with many sites warming into the upper 70s
by 10 am. One of the warmest sites so far is Sanford at 81 degrees
which is no surprise. Portland is already reporting a sea breeze
just after 10 am so the warm readings along the coast may have
already peaked. Will be updating temperatures hourly. Otherwise
cumulus field is developing over the higher terrain where upslope
flow is giving the airmass a boost. Not expected any showers to
develop however. In addition lingering valley fog dissipated
around 9:30 am.
at 06z...a 1022 millibar high was centered over northeast
Pennsylvania. The surface high will slide east and crest across
the area today before sliding offshore. GOES infrared imagery
showed patchy low and middle cloud across the forecast
area...otherwise skies were mainly clear with patchy fog and
stratus forming across some Interior Valley locations. For
today...any early morning fog will quickly burn off leaving mostly
sunny skies under the surface high. We'll warm into the 80s under
the strong July sunshine...with conditions a bit cooler along the
coast where the light synoptic flow will turn onshore by
Short term /6 PM this evening through 6 PM Tuesday/...
a clear start tonight...then warm air advection middle and high
clouds will spread northward into the forecast area after
midnight. Lows tonight should be mainly in the 60s.
Moisture continues to stream northward into the area on Tuesday
with a mix of clouds and sunshine and temperatures warming into
the 80s...with some 70s near the coast in onshore flow. Expect
showers and a few thunderstorms to develop by afternoon in
response to daytime heating and with approach of upper trough.
Long term /Tuesday night through Sunday/...
the long term appears most active early in the period...as cold
front slowly works its way across the northeast. Fairly Stout shortwave
ridge is place ahead of the cold front seemingly continues to slow
frontal passage in model forecasts. Ahead of the front will exist a warm and
humid air mass. However...lapse rates aloft are forecast to be
rather poor...as any elevated mixed layer air remains bottled up
to our SW with persistent eastern trofing. Even so...dewpoints
climbing well into the 60s should at least provide for modest
instability. The other issue is forcing aloft...as shortwave trough will
be shearing out off to the NE. This leaves the strongest wind
field across southern Canada...and shear lacking across New Hampshire and western ME.
Latest Storm Prediction Center sref suggest 30 kts of 0-6 km shear is about a Coin
flip across the northern zones...which would be just about enough for
possible storm organization. As such...would not be surprised to
see Storm Prediction Center extended a marginal severe thunderstorm risk into parts of the
forecast area...as a downstream continuation of swody2 marginal
risk across parts of the Great Lakes. A very warm and moist column
will limit any threat to water loaded wind gusts and heavy rainfall.
After the front clears the coast...high pressure will generally be in
control. Model forecasts are in agreement that flow becomes
somewhat more zonal across the northeast for the second half of
the week...keeping the real hot and humid air S across the middle
Atlantic. Late in the period western ridging tries to reload...which
in turn will help heights to fall across the eastern Continental U.S.. shortwave
dropping into the trough will try and draw moist air mass back
northward...giving the next best chance for precipitation early next week.
Aviation /15z Monday through Friday/...
short term /through 00z Wed/...mainly VFR through tonight...except
for valley fog vicinity of khie/kleb this morning...and possibly Tuesday
morning as well. Scattered MVFR Tuesday afternoon in rain showers and thunderstorms and rain.
Long term...VFR expected to prevail through the extended. Best chance
for ceiling/visibility restrictions appears to be Wednesday...as cold front
crosses the area. Most likely is scattered MVFR and isolated IFR in
rain showers/thunderstorms and rain as front crosses the forecast area. VFR returns Thursday through
short term /through Tuesday/...winds and seas will remain well
below Small Craft Advisory levels through Tuesday as high pressure traverses the waters.
Long term...winds are expected to remain below Small Craft Advisory thresholds through
the extended. Extended period of southwesterly flow over the outer waters
ahead of approaching midweek cold front may bring a period of 5 feet
seas Wednesday before subsiding.