000
FXUS61 KGYX 020550
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1250 AM EST Tue Mar 2 2021

.SYNOPSIS...
Winds will increase in the wake of the arctic front tonight and
temperatures will take a tumble. Very cold wind chill values
are expected later tonight and Tuesday with wind gusts of 40 to
50 MPH expected. Thereafter, little if any precipitation is
expected for the rest of the week outside of mountain snow
showers. However, colder than normal temperatures are expected
on average, especially by the end of the week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1245am Update...It looks like the heaviest of the snow
showers/squalls have now moved offshore, but there are some
weaker ones still rotating through the CWA at this hour.
Expecting these to wane in coverage as the core of the upper low
moves east of the are over the next few hours. Made some slight
adjustments to PoPs and matched temperatures to the latest
observations; no other changes at this time.

950 PM...SHSN seem to be focused along boundary across S central
NH, and some have drifted into SW ME. It seems original band of
snow showers earlier this evening prevent Tds from falling and
developed a little low level moisture moisture pool, which has
been active thanks to dynamics aloft. Overall the intensity of
these showers has gone down, but may see them continue through
midnight before the drier air moves in they dissipate.
Otherwise, just some tweaks to sky and temps based on current
obs, but overall forecast in good shape.

740 PM...Cold front Part 2 has moved thru the CWA, the winds
increased and the temps are falling, as one band of showers
moved through. Cold Part 3, and likely the final front will move
trough around midnight, with stronger W-NW winds and even colder
temps moving in. The final cold front is being pushed along by
500 MB trough axis which has some energy with it. This has and
will likely continue to produce snow showers, and perhaps
embedded squalls, given the winds, across central srn NH,
through this evening. Will have to watch as brief bursts of
snow and sudden drops in vsby are possible. Otherwise should
start to see some clearing after midnight as the really dry and
cold air moves in.

Previously...Main concern tonight will be the passage of arctic
cold front...winds will be covered below as they mostly take
place very early Tue morning thru mid afternoon.

Front is just entering Nrn zones at this hour...with a
combination of rain and snow showers along it. Temps are falling
sharply behind it...from the upper 30s into the upper 20s. The
core of the tropopause polar vortex (TPV) is easily seen
spinning to the E of Georgian Bay. This will be the main feature
to watch for snow squalls and plunging temps. Current trajectory
would have it grazing Srn NH this evening...and that is where I
have the highest PoP. Core of the best snow squall parameters
looks like it may stay S of the forecast area...so this will
need watching thru the evening but I have not played up the
threat too much with respective to brief heavy snow and low
visibility in the grids as of yet.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
Early Tue thru mid afternoon will be all about the wind. Deep
mixed layer in strong CAA will support efficient momentum
transfer to the surface. Model guidance...especially hi-res...is
showing a strong NW LLJ in excess of 50 kt developing early Tue.
This favors widespread wind gusts in excess of 50 mph and wind
advisories remain in place for this threat.

What is more concerning is the developing inversion that lowers
into the morning Tue. The inversion is currently forecast to
lower to near ridgeline. Upstream locations are forecast to have
a similar inversion setting the stage for strong downslope
acceleration in the lee of the mtns. Forecast cross sections
feature theta lines bending towards the surface downwind of the
summits...along with strong downward omega. Higher-res guidance
even develops a jet in this zone...similar to other downslope
wind storms. Winds are also strongest near the summit and
decrease vertically. This will help support vertically
propagating waves...and acceleration of flow over and down the
mtn slopes. This will particularly be the case downwind of the
White Mtns...Mahoosucs...and Bigelows. For this reason I have
issued a high wind warning for these downslope winds. This
situation is not that different from some of the big winds of
recent years like Feb 2019 monthly record gust of 171 mph at
MWN.

These winds combined with temps falling to near 0 will drop wind
chills colder than 20 below in the foothills...and 30 below N of
the mtns. There have been no changes to the wind chill
headlines.

The cold and winds will be relatively short lived. An
approaching wave will send a warm front Nwd and that will
diminish the winds and allow temps to warm thru the night Tue
night.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
A zonal, shortwave driven pattern gradually amplifies during
the back half of the forecast period with mean troughing
settling in over eastern NOAM by the weekend. Thus expect a
fairly quiet period of weather with temperatures trending a
couple to a few degrees below normal through the week. The only
weather to speak of during this time is a few snow showers
mainly over the mountains along with breezy northwest winds as
shortwave axes rotate around the trough overhead, centered on
the Thu/Fri time period. Ensemble anomalies agree on the
general magnitude of cold with this airmass... with an h850
airmass around M20C dipping into New England by the start of the
weekend. The pattern grows more uncertain by the start of the
next week... a southern stream wave tracks across the southern
states and may phase with the northern stream trough and bring a
warmer airmass - and perhaps a storm off the coast - by the
start of next week.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Short Term...Remaining MVFR CIGs will clear out S of the mtns as
we transition to upslope SHSN. MVFR CIGs will remain N of the
mtns...including HIE. Isolated SHSN are possible S of the
mtns...with local IFR possible. Most likely terminals affected
will be HIE and then LEB. Small chance these will also sneak
into CON and MHT. Winds ramp up late tonight thru midday Tue.
Surface gusts of 30 to 40 kt possible at all terminals.
Diminishing winds and VFR conditions expected Tue night.

Long Term...VFR prevails through the long term with a general NW
wind. The best shot at any restrictions is in upslope flow and
SHSN.

&&

.MARINE...
Short Term...Arctic front is dropping into Nrn zones at this
time and will cross the waters this evening. Strong winds gusts
will develop behind it. Isolated heavy snow showers are possible
along the front. Headlines for wind have not changed but the
heavy freezing spray warning has been expanded SW into Casco Bay
and the waters N of Cape Elizabeth.

Long Term...SCA conditions at times in offshore flow but
otherwise fairly quiet over the waters for the end of the week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Advisory until 4 PM EST this afternoon for MEZ007-014-
     018>028-033.
     Wind Chill Advisory until 11 AM EST this morning for
     MEZ012>014.
     High Wind Warning from 5 AM early this morning to 3 PM EST
     this afternoon for MEZ008-009-012-013.
     Wind Chill Warning until 11 AM EST this morning for MEZ007>009.
NH...Wind Advisory until 4 PM EST this afternoon for NHZ001>003-
     005>015.
     Wind Chill Advisory until 11 AM EST this morning for NHZ003-
     004.
     High Wind Warning from 5 AM early this morning to 3 PM EST
     this afternoon for NHZ004.
     Wind Chill Warning until 11 AM EST this morning for NHZ001-002.
MARINE...Heavy Freezing Spray Warning until 1 PM EST this afternoon for
     ANZ150>153.
     Gale Warning until 7 PM EST this evening for ANZ153.
     Storm Warning until 1 PM EST this afternoon for ANZ150>152-154.
     Freezing Spray Advisory until 1 PM EST this afternoon for
     ANZ154.

&&

$$

NEAR TERM...Watson
SHORT TERM...Legro
LONG TERM...Casey

NWS GYX Office Area Forecast Discussion








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