NWS Gray, Maine Area Forecast Discussion



000
FXUS61 KGYX 200326
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1026 PM EST Wed Feb 19 2020

.SYNOPSIS...
Much colder air will move into the region through tonight as
Canadian high pressure settles into the eastern half of the United
States.  This cold air will remain in place through the end of the
week.  High pressure will move south of the region this weekend
allowing temperatures to moderate with continued dry conditions.
The next potential for widespread precipitation will come Monday
night and Tuesday of next week as an area of low pressure forms
along the east coast.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
1020 PM...Not too many changes, mins came up a little bit based
on current obs, and winds holding on thru the evening, as well
as some clouds in the mtns. Those clouds partially caused buy
the broad troughing aloft N of the CWA and the weak waves moving
thru it, as well as some moisture working its way in from Lake
Ontario, though too dry to produce any snow reaching the sfc.

630 PM...Made a few tweaks to wind, keeping a little bit
stronger through the first couple hours after sunset, and thus
having temps drop slower earlier, but more later, to end up with
similar mins and wind chills overnight. Otherwise, should be a
cold February night.

Previously...
High Impact Weather Potential:

  * Wind gusts in excess of 35 mph coming to an end shortly.
  * Wind chills below -20 F in the mountains and points north
    tonight.

Pattern: Broad troughing has enveloped all of the northeastern
United States in the mid levels with a sprawling surface high
pressure centered over the northern Plains directing an arctic
airmass into our region upon strong northwesterly winds. We will
reside on the eastern flank of the aforementioned high pressure
system...with northwesterly flow bringing progressively drier
and colder air into the area. Thus...the focus through the near
term forecast will be on temperatures...winds...and the
potential for dangerous wind chills tonight.

Through this evening: Gusty northwest winds will continue into the
evening given robust gradient and ongoing cold advection...but with
decreasing low level instability and a weakening isallobaric
component...overall wind speeds will subside.  Temperatures will
fall rapidly with 7pm values in the teens in the mountains...with
20s from the coast into the foothills.

Tonight: High pressure continues to build in from the west with
drier air pushing PWATs below 0.10" overnight.  This will cause snow
showers to weaken and be confined to upslope areas of the Whites.
There will be increasing breaks in the clouds in this region with
full clearing to the south and east.  The wind gradient will
decrease overnight but should be strong enough to keep most
locations coupled through midnight...with some of the deeper valleys
decoupling beyond this.  Consensus low temperatures /which should
perform well given the mixing/ bring lows below zero in the
mountains and in the single digits to around 10 to the south and
east.  The combination of continued light winds and these
temperatures should allow wind chills to fall below zero throughout
the CWA...and below -20 in the north.  Thus...will run a Wind Chill
Advisory tonight for these areas in coordination with BTV and
CAR.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
High Impact Weather Potential: Minimal.

Thursday: The coldest of our cold /T8s near -2 sigma/ airmass will
be overhead with cold advection largely coming to an end.  With a
significantly drier airmass in place and weak height falls shifting
to weak rises by afternoon as the mid level trough axis shifts east
of our longitude...expect any remaining mountain snow showers to
come to an end with increasing amounts of sun in these locations...
and mostly sunny skies to the south and east of the mountains.
T9s in the mid minus teens will only allow highs into the single
digits in the mountains...with teens in the foothills and lower
to middle 20s over southern NH and coastal ME. Northwest winds
10 to 20 mph will keep wind chills below zero through the day in
the north...and near zero in the foothills and along the coast.

Thursday Night: Ridge axis will be centered overhead allowing winds
to slacken and setting up the potential for a very chilly night
across the forecast area.  Looking at the low level gradient...most
locations should have no trouble decoupling with winds going calm.
Biggest challenge for the overnight will be the potential for mid
level cloudiness associated with mid level troughing that will
remain in our vicinity through the night. Given the decoupling
wind...expect that we/ll not need any wind chill headlines despite
the colder overnight low temperatures.  As for lows...with the cloud
cover...have some concerns about going below the cold end of the
guidance envelope /which would be typical for a more clear cut
radiational cooling event/.  Still...it will be cold with lows
likely below zero for all but the immediate coast and far
southeastern NH with minus teens in the mountains. With a bit
less cloud cover...and some -20s are very possible.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
The extended forecast looks warmer and very quiet as far as
sensible  weather is concerned. A gradual warming trend is
expected from Friday through Tuesday with near-zonal flow aloft
for several days. There will be a dearth in disturbances with
most energy either north or south of our latitude. This will
result in few periods of precipitation across the area. With the
extended warming period, and some decent QPF possible early
next week, there may some issues with ice jams by next
Wednesday.

After a very chilly start Friday, temperatures rebound to near
or  just above climatology. Highs should be in the upper
teens/lower 20s north to the upper 20s along the coast and over
the warmer regions of southern NH. At the surface, high pressure
centered over the southern CONUS will extend farther northeast,
building into northern New England as it does so. Winds at the
surface will be light and variable, with plenty of sunshine.

The high pressure center shifts gradually towards the
southeastern U.S. over the weekend. A weak trough will attempt
to move through the region Saturday into Sunday, and will bring
cloud cover and perhaps a few snowflakes to the international
border. For the next several days, temperatures will be warming
under mostly full sunshine, with 30s to the lower 40s in store
for Saturday. Sunday through Tuesday we will reach the upper
30s/lower 40s north to the mid 40s south/near 50 degrees south.

Winds turn southerly by Sunday night, allowing for PWATs to
increase ahead of the next system. Cutoff low pressure over the
southern Plains will shift to the Mid-Atlantic region before
exiting into the Atlantic. Farther north, a short wave within
the polar jet will swing into eastern Canada. Isentropic lift as
well as specific humidities will be on the increase Monday night
into Tuesday as a warm front nears. This will trigger some
scattered warm air advection showers in the area from the SW. A
cold front will eventually sweep through the region Tuesday.
Models differ on QPF amounts quite a bit during this time, as
well as temperatures, so we may be seeing a rain/snow mix for
part of the area. Will keep high chance PoPs in for the FROPA
Tuesday.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Short Term...

Summary: High pressure over the central portion of the country will
gradually build east into the northeast...with slowly diminishing
snow showers and winds tonight...with clearing skies and moderate
northwest winds on Thursday.

Restrictions: VFR conditions will dominate the terminals through
Thursday night.  Only exception is the potential for SHSN at HIE
through midnight tonight with a brief MVFR/IFR restriction possible.

Winds: Northwest winds 20G30KTS will continue through this afternoon
to diminishing to 5-10kts for the overnight. For the day Thursday...
northwest winds will strengthen to 12G18KTS before going light
and variable Thursday night.

LLWS: LLWS is not expected through Thursday night.

Long Term...Light and variable winds are expected for the first
part of the weekend. Expecting increasing VFR/MVFR clouds over
the mountains and KHIE/perhaps KLEB as a trough moves through.
Chance of -SHSN with this feature is very low. Elsewhere, it
will be VFR through Monday.

&&

.MARINE...
Short Term...

Gales continue into this evening...with residual small crafts likely
through tonight as winds/waves diminish.  Over the outer waters...
winds will remain near SCA levels through Thursday and Thursday
night as waves continue to subside.

Long Term...Friday evening into Saturday morning there may be
some weak SCA conditions over the outer waters with gusts around
25 kts and waves around 5 ft. Otherwise, light and variable
winds are forecast through the remainder of the weekend with
high pressure over the waters. There may be some light freezing
spray early Friday morning.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Chill Advisory until 10 AM EST Thursday for MEZ007>009.
NH...Wind Chill Advisory until 10 AM EST Thursday for NHZ001-002.
MARINE...Small Craft Advisory until 10 AM EST Thursday for ANZ150>152-
     154.

&&

$$
SYNOPSIS...Arnott
NEAR TERM...Arnott/Cempa
SHORT TERM...Arnott
LONG TERM...Hanes
AVIATION...Arnott/Hanes
MARINE...Arnott/Hanes

NWS GYX Office Area Forecast Discussion