Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kgyx 181036 
afdgyx

Area forecast discussion
National Weather Service Gray ME
636 am EDT Wed Oct 18 2017

Synopsis...
high pressure will pass by to the south of New England today
with warm weather expected through Thursday. A cold front will
move east through the region Thursday night bringing cooler, but
still above normal temperatures into the weekend. A deep
southerly flow develops into the beginning of next week keeping
the warm weather in place and bringing increasing humidity as
well. The next significant chance of rain arrives by the middle
of next week.

&&

Near term /until 6 PM this evening/...
update...
have updated the forecast to account for latest observations and
mesoscale models. Upslope cloudiness will continue over the
northern mountains for a few more hours before the gradient
relaxes this afternoon. Have made adjustments for current
temperatures and dew points, generally lowering them a few
degrees. Temperatures will once again climb to well above
normal levels today.

Prev disc...
some cloudiness will linger this morning over the
upslope region of the mountains and foothills of New Hampshire
and western Maine. However, as the gradient relaxes today and
the upper trough shifts to the east, clouds will diminish with
time.

As the upper level ridge shifts east over our region this
afternoon, 800 mb temperatures will be on the rise as well, reaching
+8 to +10c. Good mixing will allow temperatures to climb into
the 60s in most areas, with lower 70s possible over far
southwestern Maine and southeastern New Hampshire.

&&

Short term /6 PM this evening through 6 PM Thursday/...
mainly clear skies and increasing dew points tonight will allow
for inland valley fog to develop. A west to southwesterly
gradient will eventually increase late tonight over the region.

On Thursday, a weak trough will pass well north of the region. A
gusty west, southwesterly flow will develop, allowing our
warming trend to continue further with temperatures topping out
in the 70s. Winds will be off the water along the midcoast
region, so expect cooler temperatures in the coastal areas. Dew
point values will slowly be on the increase as well with
readings in the 50s over southern areas.

The record high temperature in Portland is 81 degrees set back
in 1963. We will fall quite a bit short of the figure.

&&

Long term /Thursday night through Tuesday/...
big picture:
although we get a glancing blow from a trough to our north
later this week, the story for the weekend and into next week
will be a building ridge over the East Coast. This will bring
continued warmth to the area. A deep trough is eventually
expected to develop over the center of the country and make its
way eastward, but this will not occur until the middle of next
week. Expect it to bring a good chance of rainfall and
eventually some colder temperatures.

The details:
a cold front will push eastward through the area Thursday night
associated with low pressure moving through northern Canada.
There could be a stray shower as far south as the northern part
of our forecast area, but for the most part expect this to be a
dry frontal passage. With the core of the colder air still well
to the north, expect temperatures to only be a few degrees
cooler behind this front for the rest of the week and into the
weekend. As the high builds in behind the front on Friday expect
temperatures to top out in the 60s. With the high moving across
New England overnight Friday night, expect good radiational
cooling conditions to exist with temperatures falling into the
30s for most areas and near freezing in the colder valleys. Went
below the Standard blend of model guidance for lows Saturday
morning especially over southwestern parts of the area closer to
the center of the surface high. This puts the forecast more in
line with the mex guidance for this period.

High pressure shifts east on Saturday with a southerly flow
developing at the surface and an upper ridge building overhead.
This will bring warmer temperatures back into the area with 70s
becoming more and more widespread with time. Dewpoints will be
climbing into the upper 50s and low 60s which will keep
nighttime lows quite balmy. Some models would like to bring a
preceding cold front through the area as early as Monday, but it
seems unlikely that this will do much to change the sensible
weather in our area even if it does move through. There is a
better consensus that a deep upper trough over the center of the
country will slowly move east toward our area on Tuesday
bringing a more organized frontal system into the area with
widespread rainfall possible. Although models are in great
agreement on the potential for rainfall next Tuesday, it is
Worth noting that the movement of these high amplitude patterns
tend to have fairly low predictability, with the bias being
toward a slower progression of these systems. Thus it seems a
fair forecast would be for the warmth to continue through
midweek with increasing chances of rain through Wednesday. Would
not expect the colder air behind the trough to be felt in our
area until late next week.

&&

Aviation /12z Wednesday through Sunday/...
short term...VFR through Thursday, except for some patchy
valley fog tonight. Areas of low level wind shear are expected through early
this morning as a 30-40 kt westerly low level jet continues
over portions of the region. Low level wind shear possible once again late
tonight and early Thursday as the gradient increases once again.

Long term...generally expect VFR conditions through Friday,
though there could be some MVFR in the mountains as a cold front
moves through Thursday night. High pressure this weekend brings
a clear sky but a good chance of morning fog in the valleys this
weekend and into early next week.

&&

Marine...
short term...Small Craft Advisory for ocean waters into this morning as
southwesterly winds increase and gust around 25 kt. Winds
should decrease this morning, however seas will still run in the
3 to 5 foot range over the eastern outer waters.

Long term...expect winds to shift to the west-northwest behind a cold front
Thursday night into Friday morning, with gusts to 25 or 30 knots
possible. These stronger wind gusts will diminish through the
day on Friday as high pressure builds in. It may take a bit
longer for the higher seas to subside, but the trend will be for
quieter conditions this weekend.

&&

Gyx watches/warnings/advisories...
ME...none.
New Hampshire...none.
Marine...Small Craft Advisory until 11 am EDT this morning for anz150-
152-154.

&&

National Weather Service Glossary of Abbreviations