Scientific Forecaster Discussion
fxus61 kgyx 192211
Area forecast discussion
National Weather Service Gray ME
611 PM EDT Thu Sep 19 2019
high pressure will be in firm control across our region through
this weekend with increasingly warm temperatures late this week
and weekend. High surf conditions are expected at ocean beaches
Friday as swells from distant Hurricane Humberto roll in. A
cold front will approach on Monday and Tuesday with a chance of
showers as it moves through.
Near term /until 6 am Friday morning/...
very quiet evening. Made minor adjustments to temperatures and
dew points in the near term with the latest forecast package.
high impact weather potential: minimal.
Pattern: a look at GOES 16 water vapor imagery across the Continental U.S.
And southern Canada early this afternoon reveals a trough-
ridge-trough pattern looking somewhat like an Omega block. New
England finds itself within impressive shortwave ridging between
troughing/Humberto circulation well offshore and a weak
shortwave cresting over the ridge north of the western Great
Lakes. Drilling down to the surface reveals high pressure
centered from the Gulf of Maine south and west through southern
New England. The airmass is quite dry...with surface dewpoints
having fallen into the mid/upper 30s this afternoon. Little
change to this overall pattern is expected overnight...with
aforementioned shortwave north of the Great Lakes passing well
north of the region overnight. With quiet conditions
expected...forecast concerns will be centered on any cloud cover
as well as temperatures and potential fog/frost development.
Through this evening: clear skies with onshore winds south near the
coast /and even a bit inland/ going calm. Temperatures will likely
fall to around 50 in the cool spots by 8pm...with mid 50s elsewhere
/except upper 50s mht-ash-psm/.
Tonight: outside some scattered-broken high clouds spilling into
northern areas from shortwave passing north of the region...expect a
quiet night with nearby high pressure ensuring light winds and good
radiational cooling conditions. Temperatures/dewpoints this
afternoon will be higher than 24 hours ago...but still expect the
best radiating locations to fall into the upper 30s. This may
allow one or two locations to see some patchy frost...but not
sufficient for any headlines. Fog is again likely although
potentially not quite as widespread given a somewhat drier
airmass and somewhat warmer overnight lows. Stuck close to
statistical guidance given pattern recognition.
Short term /6 am Friday morning through Friday night/...
high impact weather potential: minimal.
Friday: high pressure settles south of the region with some increase
in deep moisture ahead of a southward sinking cold front. The
increase in deep moisture concurrent with warm air advection pattern
will allow for some increase in mid level cloudiness...and
likely some clouds over the higher mountain peaks...but
otherwise the bigger story will be warmer temperatures as t9s
warm to +16-17c allowing for highs to move into the 70s
throughout the forecast area...closer to 70 in the mountains...
and nearing 80 over far southeast New Hampshire and southwest ME. See
tides/coastal flooding section below for more details about the
high surf advisory.
Friday night: weakening cold front moves south through the
forecast area as shortwave trough sharpens will passing north
and east of our forecast area. Moisture plume looks to be too
shallow to support any precipitation...but do expect more in the
way of cloudiness during the overnight...with the added clouds
and boundary layer moisture causing for a significantly warmer
night than we have had recently. Consensus lows in the lower and
middle 50s look on target. Given the increase in moisture at and
above the surface...expect that we will see another round of
patchy valley fog.
Long term /Saturday through Thursday/...
at the beginning of the weekend the upper level ridge will be
cresting over northern New England, moving east on Sunday.
We'll be in SW flow aloft on Monday ahead of a long wave trough
translating east and reaching the East Coast by mid week.
At the surface, a weak backdoor front pushes through early on
Saturday, causing little more than a wind shift. High pressure
and southwesterly winds will reinforce rising heights through
the weekend. Forecast 850mb temperatures will be in the 14-16
degrees c degree range, which will support surface temps in the
80s over much of New Hampshire as well as the coastal plain. Mid 80s are
likely for the favored hot spots in southern NH, and Manchester
may break or tie their record Max on Sunday of 85 degrees, set
Moisture and temperatures remain above normal through Monday
ahead of a cold front, then begin to moderate by Tuesday.
Precipitation should approach the mountains from southern Canada
Monday morning and reach central and southern New Hampshire and ME by the
afternoon. Instability will be weak, so not expecting thunder at
this time. Models are forecasting a surface low forming south of
the Gulf of Maine Tuesday, prolonging the rain event. The whole
area of precipitation moves into eastern Maine by late Tuesday
night into early Wednesday morning.
Cooler and drier air arrives behind the frontal passage for mid week with
temperatures dropping into the 60s and lower 70s for highs.
Another front may arrive next Thursday, but may be lacking in
moisture and would mostly serve to reinforce the cooler air
Aviation /22z Thursday through Tuesday/...
Summary: high pressure will remain over the terminals through early
Friday before a weak trough passes through the region late Friday
and Friday night.
Restrictions: VFR through Friday night outside of fog development at
hie/leb. At these sites...vlifr/LIFR possible for a few hours
surrounding daybreak both tonight and again Friday night.
Winds: winds turning onshore at coastal sites while remaining light
and variable elsewhere. Winds will go calm overnight before
becoming northwesterly 5-10kts on Friday. Winds diminish to
calm/light-variable Friday night.
Lightning: no lightning is expected through Friday night.
Llws: no low level wind shear is expected through Friday night.
Long term...VFR conditions expected through the weekend except
for early morning valley fog. A cold front arriving on Monday
will bring some showers and possibly MVFR conditions at times.
Winds will remain below Small Craft Advisory levels through Friday night. Swell
generated from Hurricane Humberto well south and west of the
region will bring wave heights to Small Craft Advisory levels beginning Friday
and continuing into Friday night before subsiding.
Long term...high pressure gradually shifts east this weekend
with light winds becoming south to southwesterly on Sunday and
Monday. Could see a few gusts to 25kt as these winds pick up
ahead of the cold front on Monday. Seas will have decreased
below 5 ft for Saturday and Sunday but may reach 5-7 ft over
the outer waters Monday afternoon through Tuesday morning before
wave model guidance continues to show long period swell arriving
from Hurricane Humberto on Friday. No changes to the high surf
advisory this afternoon with support for large breaking
waves /4-7 foot/ and strong rip currents. The swells will
subside overnight Friday night.
ME...high surf advisory from 8 am to 10 PM EDT Friday for
New Hampshire...high surf advisory from 8 am to 10 PM EDT Friday for nhz014.
Marine...Small Craft Advisory for hazardous seas from noon Friday to 2
am EDT Saturday for anz153.
Small Craft Advisory for hazardous seas from 4 am Friday to 2
am EDT Saturday for anz150-152-154.