Scientific Forecaster Discussion
fxus61 kgyx 222137
Area forecast discussion
National Weather Service Gray ME
537 PM EDT Thu Aug 22 2019
high pressure will dominate the weather pattern this weekend for
pleasant weather and comfortable humidity levels. An area of
low pressure off the East Coast will track south off Cape Cod
early next week that will likely be too far offshore to impact
the area. A front will approach the area from the west midweek
bringing an increase in temperatures and humidity and a chance
Near term /tonight/...
special 19z gyx sounding showed impressive 1200 SBCAPE and 40kt
shear available this afternoon. However, MLCAPE was only 200, a
result of some dry air just above the ground. This seems to be
what is limiting the intensity of convection today as dry air
mixing into updrafts is reducing the instability. While the
eastward advancing boundary is colliding with the sea breeze
over the midcoast now, aiding in low level convergence and
upward motion, it still has not been enough to produce strong
updrafts. Thus expect the remaining activity over the I-95
corridor northeast of Augusta to gradually move southeast and
dissipate over the next couple of hours. Have updated the
forecast with this thinking without much change overall.
a cold front is moving through the region this afternoon with
scattered showers and thunderstorms. At 19z the leading edge of
the front was just moving into the western mountains with
increasing westerly winds across Vermont and decreasing
dewpoints. To the east the coastal plain remained calm, with
dewpoints near 70f. This has resulted in around 1000-1500 j/kg
of surface based cape across the region. As the front moves into
this more moist airmass expect convection to strengthen across
the eastern portion of the area. So far, a weak cap present in
the kgyx 12z sounding has kept cells from getting very tall, but
a 19z sounding in progress should provide more representative
information for the afternoon environment. With the stronger
winds aloft, some damaging winds are possible in the stronger
As the front makes its way through the region through the
evening expect convection to move offshore and die off as the
sunsets. While the Post frontal environment is a lot drier, the
back edge of the upper level support on water vapor imagery is
still back in the St. Lawrence Valley and will likely take most
of the night to clear through. This may allow for just enough
moisture in the northern valleys for some fog to form.
Short term /Friday and Friday night/...
by Friday, we move fully into the Post- frontal environment
with drier air mixing to the surface and northwesterly flow.
Highs will be around 10 degrees cooler than today with
temperatures dropping into the 40s and 50s Friday night.
Long term /Friday night through Thursday/...
the long term forecast will feature mainly dry weather with
temperatures near to slightly below average. On Saturday high
pressure at the surface will build in from the west as a 500 mb
trough over the Canadian Maritimes moves east. Come Sunday a piece
of the 500 mb trough will break off forming a closed upper level low
in the vicinity of New Jersey while high pressure at the surface
slowly migrates eastward. Both Saturday and Sunday look like
pleasant days with temperatures in 70s on Saturday and near 70
on Sunday with dewpoints in the mid to low 50s.
On Monday the upper level low will move over southern New England
and may provide enough instability for a chance of showers over
southern areas during the day Monday. After Monday models start
to diverge in handling an area of low pressure off the East
Coast as a 500 mb trough digs into the Great Lakes. On Tuesday
global models take the area of low pressure south and east of
southern New England with a large spread in the placement and
timing of its passage. At the moment it looks like this low will
be too far south and east to bring rain to the region. By the
middle of next week the trough over the Great Lakes slowly moves
east with a front approaching from the west. This set up will
bring an increase in temperatures and humidity with a chance of
precipitation Wednesday into Thursday.
Aviation /22z Thursday through Tuesday/...
short term...some scattered showers and thunderstorms are
expected to briefly impact the area as a cold front moves
through. These may briefly lower conditions to MVFR. Elsewhere
VFR will remain. Overnight flow becomes northwesterly behind the
front. In the CT River Valley and into the northern mountain
valleys patchy fog may lower conditions
Long term...VFR through the weekend under high pressure.
short term... a cold front will cross the waters tonight with a
few scattered showers possible late this evening. Overnight fog
returns to the eastern waters before a drier airmass slowly
moves in overnight. Northwesterly flow will move into the waters
to start the weekend.
Long term...winds and seas will remain below Small Craft Advisory thresholds
through the weekend. Seas will build to around 5 feet Tuesday as
an area of low pressure tracks offshore of the southern New