Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 221947
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
247 PM EST Fri Feb 22 2019

.SYNOPSIS...
High pressure will build in from the west tonight and will crest
over the region early Saturday before shifting offshore. A warm
front will approach the region from the southwest Saturday night
and lift north into southern New England on Sunday spreading
snow that will change to a wintry mix and rain before ending
Sunday evening. Low pressure developing on this front will
strengthen rapidly as it moves into the Canadian maritimes on
Monday resulting in very strong westerly winds that will bring
much colder air into the region. Seasonably cold and dry
conditions will continue for the remainder of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure building in from the west overnight will dry up
any remaining clouds lingering over the mountains and
Connecticut Valley this evening. Low temperatures will range
from the mid teens to lower 20s north and will range through the
20s in the south.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
High pressure will crest over the region early Saturday before
shifting offshore in the afternoon. Aside from a few high
clouds...skies should be mostly sunny through the day with highs
ranging through the 30s north and upper 30s to lower 40s south.

Low pressure moving northeast through the western Great lakes
will lift a warm front toward the region Saturday night. Broad
area of over-running will shift in from the west after midnight
initially bringing snow into southwest zones. Warmer air aloft
will quickly stream into southern zones by after midnight so
expecting snow to quickly mix with sleet and change to rain or
freezing rain toward Sunday morning across southwest New
Hampshire. Could see an inch or two of accumulation before the
change-over. Expect lows to be reached during the evening hours
before becoming steady or slowly rising after midnight. Lows
will range from the mid teens to lower 20s north and mid to
upper 20s south.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...

**Slick Travel Sunday Followed by Very Strong Winds Monday**

High Impact Weather Potential:

* Snow and mixed precipitation Sunday.
* Advisory level winds /45 mph gust/ likely on Monday...with some
  threat of Warning level winds /60 mph gust/.
* Advisory level wind chills possible in the mountains Monday
  night.

--Pattern and Implications--

The trough/ridge pattern discussed yesterday continues across the
United States...but the trough over the southwestern states is on
the move and promises to be our next weather maker as it rides over
the eastern ridge and teams up with northern stream energy dropping
out of Canada.  This will result in a potent surface low that rides
north and east through the Great Lakes giving way to a low that
develops in the Gulf of Maine and deepens rapidly as it moves
into the Canadian maritimes. This will bring an end to the ridge
over the southeastern United States...with a relaxation of flow
over the Pacific /EPO turning negative/ allowing the northern
stream to become more dominant next week...with lower than
normal heights and temperatures taking hold across the northern
states implying an impressive westerly jet across the northern
tier between this and more seasonable temperatures/heights over
the south. While the storm system on Sunday into Monday is well
agreed upon...the fast flow pattern for the remainder of next
week suggests lower confidence in feature timing.
However...given the dominance of the northern stream...systems
will be more moisture-starved with no high-impact weather likely
beyond early next week.

--Daily Details--

Sunday:  Low pressure Sunday morning will be located near the
Straits of Mackinac and will continue to be strengthening as it
moves north and east.  Broad warm advection signal ahead of this
feature in association with +2-3 sigma southerly LLJ at H8 combined
with PWATS around 1" over southern New England will allow for a
region of precipitation to move through the region during the day.
The overall setup is not dissimilar to what we saw yesterday...but
with more moisture...and a much stronger primary low. The overall
trend over the past 24 hours has been a bit warmer solution
aloft...but with a cold air damming signature suggesting that
it will be more difficult to scour out low level cold air.
Thus...have a snow to mix to rain scenario in the foothills and
points south...with primarily snow in the mountains. The thrust
of precipitation favors a pretty quick hit...and have continued
to be cautious with QPF...with storm total values 0.4-0.7"
favored. Overall this suggests an advisory level event with 4-6"
of snow in the mountains and 1-3" of snow to the south of this.
Best chance of ice accumulations appears to be over the terrain
of SW New Hampshire /accumulating during the AM/ where warm air
aloft will arrive first. Here 0.1-0.2" of ice is possible...but
most likely over the hills /above 1000 ft/ with no more than a
very light coating in the lower terrain. Temperatures will be
pretty stubborn...reaching the mid/upper 30s by evening over
southern NH and along the coast of Maine...with temperatures
elsewhere hovering around the freezing mark.

Sunday Night - Monday:  Secondary low pressure rapidly deepens
Sunday night becoming a powerful /970s/ low in the Canadian
maritimes for Monday.  Pressure rises behind this departing low of
+12/18 mb/6hr are well aligned with the west northwest
gradient...and H9 winds to 50kts.  Model sounding profiles favor 50-
60kts at the top of the mixed layer...with 40-45 kts around 2kft.
Robust cold advection will ensure ample mixing to transport a good
deal of this wind to the surface. Overall...a rather impressive
signal for wind in a cold advection regime.  Fully expect that we/ll
have many areas hitting wind advisory criteria...with gusts to
warning level /50kts/ not out of the question...particularly over
the hilltops. Otherwise...expect a non-diurnal temperature evolution
especially away from the coast...with robust cold advection allowing
for steady/falling temperatures.  High temperatures won/t be all
that cold given the mild airmass that will be departing...but by
evening temperatures will range from the single digits in the
mountains to around 20 along the coast with wind chills 10-15F
colder than this.

Monday Night:  Robust cold advection will drive temperatures to near
zero in the mountains...and only lower teens over southern NH and
the coast.  These temperatures combined with continued strong west
and northwest winds will likely bring wind chills below -20 in the
mountains after midnight...which would require wind chill headlines.
Residual moisture and cyclonic flow should continue snow shower
activity in the mountains with light accumulations in favored
upslope areas.

Tuesday: Much colder day expected with T9s firmly in the minus
teens and plenty of residual gradient to allow for continued
gusty west and northwest winds. The drying low level airmass and
slowly relaxing cyclonic flow should cause mountain snow
showers to wane. Expect some spots along the Canadian border to
struggle to 10F...with teens and 20s in the foothills and
coastal areas...10-15F below seasonal norms.

Wednesday: Pretty large model disparities for the middle of the
week...with the GFS dropping a clipper system through the region
with a widespread area of snowfall.  The GGEM is more suppressed
with this feature...and the ECMWF is suppressed further...to the
point of dissipating it before it reaches the east coast. Both the
EC and GFS has ensemble support for it/s solution...which suggests
neither operational run is a particular outlier.  Therefore will
continue to include CHC pops...but favor the more suppressed
EC/GGEM/EC-EPS solution to some degree.  The below-normal
temperature trend will continue...with the drier/suppressed
solutions favoring temperatures aloft actually falling from those on
Tuesday with morning wind chill headlines again possible.  Will
continue to follow consensus highs in the teens and lower 20s.

Thursday-Friday: Overall agreement improves for the end of the
week...bringing a sprawling area of high pressure into the region to
end the forecast period Thursday and Friday ensuring a good deal of
sunshine and dry conditions.  Also...a warming trend is expected a
heights aloft recover and the llevel flow backs. Despite the
warming...it is unlikely that temperatures move back above seasonal
norms through the end of the week.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Short Term...VFR tonight through Saturday. VFR Saturday
evening...then IFR/LIFR ceilings/vsby developing after midnight.

Long Term...

VLIFR/LIFR in Snow changing to mix/rain at the terminals on
Sunday before rapid improvement to VFR Sunday night /MVFR-IFR
SHSN continuing at HIE/. Westerly winds on Monday will likely
gust over 40kts...and continue through the evening with gradual
slackening of the winds Monday night into Tuesday. VFR likely to
continue Monday-Tuesday /with SHSN still possible Monday at HIE/
with some threat of -SHSN on Wednesday...especially over the
southern terminals.

&&

.MARINE...
Short Term...No flags.

Long Term...

Wind gusts to gale force are likely under southeasterly flow ahead
of approaching low pressure on Sunday.  This low passes over the
waters Sunday evening with westerly winds rapidly strengthening in
it/s wake overnight Sunday night with widespread gales for Monday.
The threat exists for storm force gusts during the day Monday
through Monday evening.  Gale force gusts should continue Monday
night and potentially Tuesday /particularly over the outer waters/
before a large area of high pressure arrives from the west with
lighter winds for the remainder of the week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Gale Watch from Sunday morning through Tuesday morning for
     ANZ150>154.

&&

$$
SHORT TERM...Sinsabaugh
LONG TERM...Arnott


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