Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 281653
Area Forecast Discussion
National Weather Service Gray ME
1153 AM EST Tue Feb 28 2017
Warm weather continues today and intensifies on Wednesday as a
warm front lifts through the region. Temperatures will be near
record warm levels before a cold front moves across the area
Wednesday night. Showers and thunderstorms will be possible as
the front moves through. Colder air rushes in behind the front
Thursday morning and lasts through the weekend.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Have updated the grids for solid cloud cover early this
afternoon over southern portions of NH and southwest ME.
Otherwise, partly to mostly sunny conditions furthern to the
north. The warming trend may trigger additional ice jams later
today or Wednesday.
Lowered forecast highs over southern areas today due to the
persistent cloud cover.
555 AM Update...
Have updated to show a low chance of showers across southern NH
where some drizzle has developed in warm air advection regime.
Cloud cover, winds, temperatures on track.
Continued warmth today with readings in the 40s and 50s
areawide. A shortwave and associated frontal fracture approaches
today from the SW with increasing cloud cover from the south
expanding north during the day. This will keep temperatures a
bit lower than otherwise. Light QPF still being advertised by
the models this evening and overnight as the moisture increases
and the warm front lifts north. P-type should be mainly rain
with any light accumulations confined to the mountains.
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
We should stay above freezing tonight with warm overnight lows
as the warm front moves north and we remain in the warm sector.
This system will deepen quickly into a ~987 mb low center
Thursday afternoon centered near Lake Ontario. Lapse rates from
700-500 mb increase to 6-7 C/km and convection will increase in
coverage and intensity.
There are a couple concerns with this system for Wednesday.
Although CAPE will be relatively low, shear will be extremely high
with 0-1 km approaching 50-60 kts and lapse rates. Depending on the
cloud cover/any breaks allowing for heating, any storms that do
develop will rotate and there will be a real concern for damaging
Basin averaged QPF isn`t extremely high but anomalies and
return intervals for the PW values are pinging this as an
extreme event. There will be the possibility for heavy rainers,
especially along the front with a deep and warm boundary layer, and
this will contribute to downward momentum transfer of strong winds.
In fact, several other factors are anomalously significant as well
including MSLP and 850/925 mb temperatures. Needless to say another
very warm day with 850 mb temperatures once again 2 to 3 standard
deviations above normal. We will be very close to breaking the
record at Concord (65 degrees in 1972) while Portland will likely be
a few degrees short (59).
PoPs diminish Wednesday night as the low quickly ejects north.
Expecting a cloudy, foggy night with some residual showers
across the Canadian border. Lows will drop into the lower 30s
north to 40s south.
.LONG TERM /THURSDAY THROUGH MONDAY/...
Cold air will be pouring in on westerly winds Thursday morning.
The cold advection will promote good mixing of the lower levels
of the atmosphere, especially downwind of the mountains. It
should be a windy day, though just how windy is a little bit
uncertain. The GFS is stronger with the winds aloft and would
suggests winds could gust closer to wind advisory levels. At the
moment we will go with 35 to 40 mph gusts, but a few gusts
higher would not be out of the question. Temperatures may end up
falling through the day as cold advection continues.
Below normal temperatures are expected Friday and Saturday, with
the cold reaching its peak intensity on Saturday. Might even
approach wind chill advisory criteria in the north on Saturday.
Highs on Saturday will be about 10 degrees below normal. Expect
gradually moderating temperatures Sunday and Monday. The next
significant chance of precipitation will be Monday night as the
next trough moves into the area from the west. Precipitation
type seems to favor snow at this point though the warm advection
would raise suspicions for more of a mix of precipitation types
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Short Term...VFR clouds will gradually decrease throughout the
day today and tonight to MVFR conditions with possibly lower as
moisture pools along a northward moving warm front. -SHRA will
increase in coverage with the chance for -FZRA, IP, or -SN away
for HIE and possibly AUG. Amounts will be very light if the
threat does develop. Expecting some fog developing with
increasing moisture tonight. In addition there will be a chance
of -TSRA Wednesday afternoon mainly in the MHT/CON/LEB corridor
and perhaps including PWM and HIE later on.
Long Term...MVFR conditions linger in the mountains on Thursday
while the rest of the area goes VFR to clear. Westerly winds
will gust to 30 KT on Thursday, with a few stray gusts higher
than that. Should see a fairly prolonged period of VFR
conditions through the weekend.
Short Term...Currently winds and seas have diminished and have
allowed the SCA to expire. Have issued a gale watch beginning
Wednesday evening and into Thursday evening as a strong front
affects the waters.
Long Term...Westerly winds behind the cold front will likely
reach gale force on Thursday. These winds diminish below gale
force through the evening hours. Continued offshore cold
advection flow will continue through Saturday with winds likely
staying above 25 KT through most of this time period. It is
possible that winds could again reach gale force on Saturday as
the pressure gradient tightens a bit.
There are currently no problems noted on the rivers as ice
movement from a few days ago has largely stopped. But continued
warm weather especially on Wednesday could get things flowing
again and will raise the possibility for more ice jam related
MARINE...Gale Watch from Wednesday evening through Thursday evening for