Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 221704
Area Forecast Discussion
National Weather Service Gray ME
1204 PM EST Sun Jan 22 2017
A cold front will stall to our south through tonight as high
pressure builds by to our north over eastern Canada. A storm
system tracking up the coast will bring wintry precipitation to
the area Monday and Tuesday. A cold upper trough will remain over
the area through the latter part of the week with a return to
colder temperatures. Scattered snow showers in the mountains and
foothills can be expected through the latter part of the week.
.NEAR TERM /UNTIL 5 PM THIS AFTERNOON/...
-- Changed Discussion --1205 PM...For this ESTF update I adjusted pops upward to reflect
echoes associated with backdoor front as well as ingested the
latest mesonet in near term grids.
945 AM...The backdoor front has now dropped to our south and we
find ourselves in light northeast flow with 1031 millibar high
situated just east of Hudson Bay. GOES imagery shows widespread
clouds across the region with clearing confined to areas north of
the Saint Lawrence river. Despite the lack of sunshine
today...it`ll be another unseasonably mild day across the forecast
area. For this ESTF update...I ingested the current mesonet into
near term grids and adjusted pops to reflect current radar trends.
Otherwise...only minor adjustments were needed.
Update... Have updated the grids based on current
conditions. A weak front will be situated over southern New
Hampshire today. In this proximity, pockets of drizzle or very
light rain may develop from time to time. This weak feature is
being picked up by latest set of mesoscale models.
Fortunately, surface temperatures remain above freezing over much
of New Hampshire. Nevertheless, similar to yesterday, this area
will need to be monitored closely for pockets of -FZDZ. Patchy fog
will continue through the morning hours as well.
High pressure will rebuild into the region from Canada as a
backdoor cold front crosses northern New England. The boundary
will stall near southern New Hampshire. Once again, patchy drizzle
may break out today with the most likely location being near and
along this boundary.
Surface temperatures continue to be very mild for this time of the
year with most areas climbing to above freezing as the drizzle
forms over southern portions of the region. Nevertheless, this
area will need to be monitored closely as there remains the
possibility of pockets of freezing drizzle to break out.
By afternoon, temperatures will be near 40 degrees in southern
locations, despite modest cold air advection.
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.SHORT TERM /5 PM THIS AFTERNOON THROUGH 6 PM MONDAY/...
Similar conditions will persist tonight with the possibility of
drizzle with freezing drizzle potentially breaking out as the
night goes on. Not entirely sure this will be in the form of
flurries arriving off the ocean or drizzle/freezing drizzle as
dynamics slowly increase.
By Monday, the coastal front will be nearly fully developed as
warm air advection increases in the soundings. The wet bulbing
effect will allow for snow to break out across the interior with a
mixture of rain and snow along the shoreline. Blended models
together, however we leaned more towards the cooler Euro.
Surface temperatures are expected to be cooler with readings in
the mid 20s in the north to the mid 30s in the south as cold air
damming continues. This sets the stage for a complex forecast in
the long range.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
A vertically stacked low pressure system will lift northeast from
the southeastern US up the eastern seaboard reaching the Gulf of
Maine by Monday night and Tuesday. A generous amount of qpf will
be associated with the system as per models and its source region
would suggest. Ahead of this system a Canadian ridge of high
pressure will be centered to the north of northern New England
suppling cold air drainage from the north in the low levels.
This all will make for a very complex forecast. PTYPE will be a
major forecast challenge as boundary layer temps along southern
and coastal areas should quickly warm above critical levels change
any snow or mix over to rain rather quickly before any
accumulations. Further inland will be more of a problem where cold
air damming will be occurring and deep enough, along with UVV
helping in mixing down some additional cold air, plus some evapo
cooling, all for a time allowing for the precipitation to remain
snow through part of Monday night allowing the potential of some
significant snow accumulations to occur. A matter of a 2 deg
Celsius swing could make for significant changes in the forecast.
It appears several warm layers will work well inland by later
Monday night due to the very strong ESE 50-65kt low/mid level jet
changing most areas over to a prolonged period of sleet or even
some freezing rain. Used a blend of the models for overall
forecast but weighed heavily on the EURO/NAM blend especially for
PTYPE using the BTV top-down approach. Winds along the immediate
coast may get gusty for a time late Monday night as the warm low
level east winds mix down to the surface. Have opted to hold off
on any winter storm watches at this time due to a high degree of
uncertainty on PTYPE.
All models agree on system exiting into the maritimes Tue night
gradually bringing an end to the mixed precipitation.
Wednesday a weak dirty ridge of high pressure moves over the area
allowing some scattered snow showers in the mountains otherwise
partly sunny conditions elsewhere with mild temps. By Thursday a
broad colder upper trof moves into the Northeast allowing for
scattered snow showers mainly in the mountains. This broad colder
cyclonic flow will continue Friday and into the weekend with
colder temps and scattered snow showers mainly in the mountains.
Stayed with superblend for the latter part of the week and into
.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
Short Term...Generally MVFR conditions will persist with patchy
fog and low clouds. Conditions deteriorating to IFR and LIFR with
the development of steady precipitation over southern areas late
in the day Monday.
Long Term...IFR to LIFR conditions Monday night through much of
Tuesday in precipitation. Conditions slowly improve Tuesday night.
VFR conditions expected Wednesday. Thursday scattered MVFR
conditions in snow showers in the mountains, VFR elsewhere.
Short Term...Winds will be on the increase Monday afternoon,
gusting into the Gale force category, before reaching storm force
over the outer waters towards evening. Wave will be rapidly
building as well in response to the increasing wind fields.
Long Term...Storm Warnings have been issued for Monday night into
Tuesday over the outer waters. Gale Warnings have been issued in
the bays beginning Monday afternoon into Tuesday. Ahead of the
approaching coastal low a very strong pressure gradient will
develop due to the high to the north allowing low level wind
gusts to exceed 50 kts over the outer waters at times. Also
increased seas forecast for the outer waters to near 20 ft which
was above guidance.
Despite being in the low portion of our astronomical tide
cycle, large building waves may produce some erosion and splash-
over near the times of high tide Monday night and Tuesday.
Preliminary storm surge values appear to be around 1.5 to 2 feet
with a persistent...strong easterly wind developing. A coastal
flood advisory may be needed from the impact of the wave action.
MARINE...Gale Warning from 3 PM Monday to 11 AM EST Tuesday for ANZ151-
Storm Warning from 6 PM Monday to 11 AM EST Tuesday for ANZ150-