Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Gray ME
958 am EDT Monday may 25 2015
a warm front will cross the area overnight....providing a chance
for showers and storms beginning late today. Warm and more humid
conditions are expected middle to late week.
Near term /until 6 PM this evening/...
thicker cloud cover moving into New Hampshire as well as area of light
showers/sprinkles this morning. So far little is making it to the
ground and according to area soundings it will take a while still
before it does with quite a lot of dry air throughout the
atmospheric column. Adjusted sky cover... hourly temperatures...
as well as today's high temperatures. There is room for Portland
and areas like Wiscasset to reach 80s as they are warming rapidly
with the help of west winds. Therefore went closer to the warmer
NAM forecast and brought highs up a little in some spots.
Previously...forecast for today /and tonight/ will be about
ongoing warm air advection through the atmosphere as warm humid air overrides the
not quite as warm and definitely drier air in the lower part of
the atmosphere. This dry air...dew points currently in the upper 30s to
middle 40s...will initially prevent any rain from reaching the ground
and should keep all but the mountains rain-free through the afternoon
today. Clouds...however...will be on the increase as the
strongest warm air advection moves downward through the atmosphere today. This
morning will mainly see the cirrus that is currently out
there...and looks to be mostly transparent at this time...so
partly sunny or filtered sunshine this morning will fade to become
mostly cloudy across the County Warning Area in the afternoon. Initially the west-southwest
flow will begin to mix US out again as well...and this should
allow temperatures to rise back up well into the 70s to low 80s in a few
spots today...although may be a degree or two cooler than Sunday
given the clouds.
Given the strong warm air advection and persistent isentropic lift through the
day...cannot rule a few sprinkles almost anywhere falling out of
middle deck...especially this afternoon...but measurable precipitation seem
unlikely...except for the mountains this afternoon where there will be
better forcing as the 500 mb wave comes over the top of the ridge
and begins to clip our northwest County Warning Area. Any rain showers will be weaker as even
elevated instability will not move in until tonight.
Short term /6 PM this evening through 6 PM Tuesday/...
the warm front will cross the County Warning Area overnight into early Tuesday. Rain showers
break out in the northern zones and parts of the CT valley this
evening...with more frequent rain showers moving across the mountains in the
hours around midnight. Some weak elevated instability moves through
the north as well...and cannot rule a thunderstorms and rain or two. Quantitative precipitation forecast in the
north overall though will only exceed a quarter of an inch where
convection does occur. Across the coastal plain...could see a few
rain showers move through overnight as well...but given less dynamic forcing
and the dry air near the surface...these may be few and far between.
Models are indicating more quantitative precipitation forecast along the middle coast...which may be
the result of the marine layer moving in late today and allowing
more rain to fall to the surface...but even this would only a few
hundredths of an inch.
On Tuesday any rain showers shift out to the east during the first half of
the morning and the warm air mixes out on S-SW winds as skies
clear out. Highs will surge into the middle to upper 80s in many
spots...although will only top around 80 in the mountains and along
most of the coast. The midcoast and Penobscot Bay coastal areas
will be coolest in the upper 60s to middle 70s.
Long term /Tuesday night through Sunday/...
the models are in general agreement on the long wave pattern
through early next week. We begin the period with an upper ridge
situated just offshore and a broad southwest flow aloft. With
surface high pressure parked offshore...the warm southerly flow
will provide several days of above normal temperatures and
unsettled weather as weak shortwaves traverse the region. The
upper ridge will eventually retreat offshore...with an upper
trough driving a cold front across the region by late in the
Aviation /14z Monday through Friday/...
short term...VFR into through sunset...then MVFR...at times in rain showers
overnight...perhaps tempo IFR late tonight...before a return to
VFR on Tuesday.
Long term...Wednesday - Friday...scattered MVFR possible in showers and thunderstorms.
short term...winds/seas diminish somewhat this morning into early
afternoon...but SW flow picks up again late today and overnight
although will stay below Small Craft Advisory criteria. Tuesday will see SW flow come
close to Small Craft Advisory winds...and seas will likely reach 5 feet offshore
during the day.
Long term...Wednesday - Friday...small craft winds and seas are possible.
relative humidity values drop off to 35-45 percent this afternoon as low level
moisture begins to increase. Will still see some west-SW winds gust
to near 20 miles per hour this afternoon as well...so although below red flag
criteria...fire danger will still be enhanced a bit especially
given the dry conditions. Good recovery and some rain showers
expected in the north tonight...but wetting rains are unlikely. More
humid conditions move in on Tuesday...with min relative humidity closer to 50
percent in the afternoon.