Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 211231 AAA
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
831 AM EDT Fri Oct 21 2016
A slow moving frontal boundary and a developing low pressure
center will bring wet weather and a cool onshore flow to the
region into Saturday. Later Saturday and Saturday night...the low
will gradually lift north into Quebec. On the backside of this
low...colder air will arrive on brisk northwest winds for the
latter part of the weekend and early next week. Some accumulating
snow will be possible in the mountains Saturday night into Sunday
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Mesoscale update...Early look at conditions this morning suggest
hi-res model guidance may be better handling the evolution of rnfl
for this afternoon. IR and WV satellite show an area of convection
over the Gulf Stream that is moving NWwd. This is likely in
response to developing low level jet thanks to the upper air
pattern over the Northeast. Current trajectory puts that
convection over Ern New England...which would support QPF of the
HRRR...CMC regional...and NCAR ensembles...vs the GFS and ECMWF.
Will continue to keep the forecast more on the side of hi-res
models until the radar fills in and then will adjust from there.
A strong digging upper short wave will be moving through the Ohio
Valley today. In advance of this deepening system a very moist south
to southeast flow will transport plenty of moisture across the
area. Warm moist air aloft will move over the cooler surface
maritime air mass today produce periods of overrunning rain and
also developing drizzle and areas of fog. The onshore flow will
keep temperatures in the upper 50s to lower 60s across most areas.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
The digging short wave continues to drive southeast into the mid
Atlantic coast tonight allowing the trough to become negatively
tilted, and then tapping some tropical moisture that will exist
from a system well off the east coast. The rain will become heavy
at times tonight due the combination of the tropical moisture and increasing
UVV as the upper trough swings northeast and develops a closed low
over our area by Saturday morning. QPF totals of 1.5-2.5 inches
On Saturday with the upper closed low moving across northern New
England, will have to expect scattered showers through the day
and most numerous in the mountains. By later in the day winds will
increase from the west over southern areas of the forecast area
under the strong cyclonic flow to the south and west of the upper
low as it slowly departs to the north.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --Chance of high impact weather: Low. Wind gusts Sunday could
approach 40 mph. Accumulating snow is expected at higher
elevations in the mountains.
500 mb pattern across NOAM continuing to show signs of a change,
with troughs developing over the the eastern and western parts of
the continent in a broad omega type block. Not high confidence
that this pattern will hold as even during the course of next
week the troughing shows signs of breaking down before being
reinforced, but the trend will favor cold air rather than warm air
so look for temps run below normal to normal in the long range.
Will start the period on Sat night and Sunday with deepening
closed 500 mb low and sfc low tracking N across the region before
stacking up over interior Quebec Sunday night. This will produce
gusty NW flow across the region beginning Sat night and peaking
during the day on Sunday, with gusts in the 30-40 mph range. Any
lingering Shra outside of the mountains Sat night should wind
down on Sunday as the downslope takes over. In the mountains, look
for SHRA to continue into Sunday in upslope flow, with rain
changing to snow across the higher terrain, and perhaps mixing
with snow a little in the valleys Sunday morning. Because the the
stacked low shifts back to the NW on Sunday the coldest air will
have to wait for secondary 500 mb trough crossing the region Sun
night into Monday, and models have backed off the intensity of
the cold air on Sunday, so, it does look like the accumulation
will be limited to higher elevations late Sat night into Sunday
evening. Lows sat night will range from the low to mid 30s in the
N, to the low 40s along the coast and in srn NH. Highs on Sunday
will be in the low to mid 40s in the mountains to low to mid 50s
in the south, where some downslope warming will counteract the CAA
and bring some sun to this areas as well. Sunday night`s lows will
be similar to Saturday night as decent boundary layer flow
persists and clouds return as the next wave approaches.
Monday will see the stronger cold of cold air, and it will remain
breezy, but not as bad as Sunday. Highs Monday may be a degree or
two cooler than Sunday, but situation is similar with
downslope/upslope conditions. Mon night lows will range from
around30 in the N, to the mid to upper 30s in the S. NW flow
persists on Tue, with CAA weakening and eventually clearing out
Tue night and Wed. Highs Tue and Wed will be in the mid 40s to
lower 50s, and lows Tue night will be in the mid 20s N to low to
mid 30s S. Wed night may be the coldest night as winds finally
diminish with some rad cooling and lows may get below freezing
across most of the CWA, with the mountains possible dropping close
Next chc for precip will be Thu or Fri and could start as snow
in the mountains as 500 mb trough drags a weakening sfc low across
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.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
Short Term /through Friday night/...IFR to LIFR conditions in
rain...drizzle...and areas of fog through early Saturday...then
conditions will improve to MVFR in scattered showers Saturday
Long Term...MVFR Sat night should improve to VFR by Sunday
morning outside of the mountains, which will linger in MVFR to IFR
briefly in SHRA at KHIE through Sunday. Also look for NW winds of
of 15-20 kts on Sunday with gusts as high as 35 kts possible. VFR
is expected at all terminals Mon and Tue.
Short Term /through Friday night/...Increasing and persistent
onshore flow will bring small craft conditions to the open waters
and marginal small crafts to the bays through Saturday.
Long Term...A period of gales is expected Sat night into Sunday
with winds diminishing a bit Sunday night into Monday morning,
but gales could return briefly Mon night.
This afternoon the 4 pm astronomical tide in Portland will be 10.6 feet.
A weak southeasterly flow ahead of the system may allow for a
half to as much as a one foot storm surge during the time of high
tide. This will not be enough to cause any minor coastal flooding
although some minor splashover may occur due to some rough seas.
The situation will continue to be monitored during the afternoon.
MARINE...Small Craft Advisory until 8 PM EDT Saturday for ANZ150>154.