Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
1202 am EDT Monday Aug 3 2015
persistent low pressure aloft...situated over Quebec...will bring
the threat of showers and thunderstorms Monday afternoon into
Tuesday. A few storms could be strong Monday afternoon and
evening. Cooler air moves in for the middle to late week...and it
will be mainly dry...although scattered showers will be possible
in the mountains Wednesday.
Near term /until 6 am Monday morning/...
midnight...other than usual adjustment of T/dew point for current
observation...decided to scale back probability of precipitation significantly through early
afternoon Monday /see below/.
Previously...warm air advection cirrus will exit to the east and
diurnally driven cumulus will dissipate after sunset...leaving mainly
clear skies overnight. With relatively light winds...expect patchy
inland fog to develop late tonight. Most of this fog will not be
overly dense with temperatures dropping close to their dew
points...in the middle to upper 50s.
Short term /6 am Monday morning through Monday night/...
update...based on latest nam12 and mesoscale models...scaled back
probability of precipitation through a good chunk of Monday...keeping the morning dry...and
most of the afternoon...except for far northern and western zones where chance
probability of precipitation move in middle afternoon...given low-middle level subsidence out
ahead of approaching wave.
Previous...anomolous upper low for this time of the year...will
continue to progress south and east towards New England Monday
afternoon. Strong dynamics and moderate instability will combine
to produce scattered showers and thunderstorms during the middle/late
afternoon hours in the far north and west. 12z guidance continues
to slow the surface front to the east with each run - and in fact
we hold the highest probability of precipitation until about the 00z timeframe.
Therefore...any chance for severe weather should be limited to the
late afternoon hours over the northern and western half of the
forecast area. It is in this location that Storm Prediction Center continues to hold
the potential for a slight risk of severe thunderstorms.
It will be hot on Monday in all locations except for the
midcoast...where an onshore flow will keep readings cooler from
wiscasett to Rockland. Readings will approach 85-90 over southern
interior locations with humid conditions as dew points creep back
into the middle/upper 60s.
Mesoscale models indicated this convection will continue to March
east...dissipating somewhat as the precipitation reaches the coast
during the late evening hours. It is at this point the front will
likely become stationary for a period. This will continue the
threat of scattered showers and storms as we head into the long
term portion of the forecast.
With the overnight precipitation on Monday...expect more widespread late
night fog to develop.
Long term /Tuesday through Sunday/...
in the long term upper level low pressure will be the driving
force in our weather. A cold front will slide off the coast
Tuesday with showers and thunderstorms possible. Models keep
delaying the passage of this front with each run. Once the front
makes its way off shore we will continue to see cyclonic
circulation aloft which will translate to afternoon showers and
maybe an isolated thunderstorm in the mountains Wednesday. The
forecast gets a bit complicated for Thursday and Friday as model
guidance is showing a short wave moving just to our south. The 12z
GFS is faster and farther north with this feature and moves it
through southern New England Thursday and off the coast before
dawn Friday while the European model (ecmwf) moves the feature through southern New
England Friday and off the coast Friday night. A period of rain is
possible for southern portions of the forecast area in this time
period. Once this short wave move through will still be under the
influence of 500 mb low with chance of afternoon showers Saturday and
Aviation /04z Monday through Friday/...
short term...a light developing southerly gradient in addition to
increasing moisture aloft may delay onset of inland valley fog
tonight. Patchy fog was mainly forecast for after 09z. Fog may be
more widespread late Monday night with rainfall and scattered
convection increasing the low level moisture. Patchy IFR
conditions are expected.
Long term...MVFR possible in showers and possible thunderstorms
Tuesday. Expect mostly VFR Wednesday expect for briefly MVFR in showers.
MVFR possible Thursday into Friday depending on how far north
surface low treks.
short term...a developing southerly gradient on Monday and Monday
night will increase winds over the coastal waters with wind gusts
to 20 knots expected. Seas will be on the increase as well beginning
Monday afternoon and continuing. Small Craft Advisory conditions
may be possible by Monday night.
Long term...seas of 5 feet possible Tuesday through Thursday.