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000
FXUS61 KBOX 272015
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
315 PM EST Mon Jan 27 2020

.SYNOPSIS...
Varying amounts of clouds much of the week ahead along with
mainly dry conditions expected. Dry conditions with closer to
seasonable temperatures for the remainder of the workweek. Still
watching for the potential for a coastal storm which may impact
the region for the weekend, though it remains far from a
certainty.


&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1015 AM Update...

Mainly cloudy skies across the region at mid morning as seen on
15Z observations and GOES-East visible satellite imagery. Only
area with mostly sunny skies was across most of Cape Cod,
Nantucket and Martha`s Vineyard. Temps were in the upper 30s
across N central and W Mass into N CT, up to the lower 40s
elsewhere.

Area of snow showers lingering across the Capital District of E
central NY into the Berkshires, though noting -SHSN reported at
KORE at 15Z. Also noting patchy light precip on the latest NE
regional 88D radar imagery across portions of N central CT and
just off Cape Ann and outer Cape Cod. However, in these areas,
T/Td spreads remain at 6 degrees or higher, so appears to be
evaporating before reaching the ground.

Mid level short wave working SE across E NY into W CT and W Long
Island, which could trigger a brief light rain or snow shower
there. May also see brief light rain and/or snow showers across
portions of the E slopes of the Berkshires through at least mid
afternoon as yet another short wave wraps SE around the low
across the Maritimes.

Previous Discussion...

Northern stream short wave approaches the region from the west today
providing cyclonic flow and lots of clouds especially inland and the
high terrain with less clouds across the coastal plain. Not much
moisture from this feature so any snow showers/flurries should be
confined to the upslope regions of the Berkshires and possibly the
northern Worcester Hills.

Not as mild as Sunday with 850 mb temps down to about -6C
today. Although well mixed boundary layer and some downslope W-NW
wind component should support highs of 40-45, except upper 30s
high terrain which is still 5-10 degs above normal. A modest
W-NW wind will make it feel a bit cooler.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
Early Morning Update...

Tonight...

Dry weather continues behind departing short wave along with
decreasing clouds after sunset. Weak cold air advection behind the
trough with 925 mb temps cooling from about -2C at 00z to -4C
by 12z Tue. Brisk NW winds at sunset will diminish as boundary
layer likely decouples except in the urban areas, high terrain
and Cape Cod/Islands should be enough pres gradient for at least
some wind. Cooler but lows still a few degs above normal with
low temps in the 20s, except 30-35 in the urban areas and Cape
Cod/Islands.

Tuesday...

Dry weather likely prevails with next potent northern short wave not
approaching the region until Tue night. The only exception to dry
weather may be across the outer Cape including Nantucket and Cape
Ann if winds have enough northerly component to generate some ocean
effect snow (OES) showers. All Hi Res guidance hints at this OES
potential. 925 mb temps cool a bit more to about -3C, supporting
highs from the upper 30s to lower 40s, mid 30s high terrain. Still a
few degs above normal. Regarding cloud cover, breaks of sunshine in
the morning likely give way to diurnal clouds with cooling temps
aloft and cyclonic flow. Clouds most abundant over Cape Cod and
Nantucket with winds becoming northerly and cold advection across
the relatively warm ocean waters.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Highlights...

* Dry conditions with seasonal to slightly above normal temps through
  Fri.

* Still monitoring for a potential storm next weekend, but
  uncertainty remains high

Details...

Tranquil stretch of weather for the rest of the workweek as ridging
both at surface and aloft builds across Southern New England. A weak
shortwave trough will dig southward from eastern Quebec through much
of New England during the latter part of Wednesday; though it will
be a dry passage and its only real influence will be to induce a
shot of cooler air (925 mb temps -8 to -11C per ECMWF, not exactly
cold but a colder airmass than seen recently) for Wednesday night
into Thursday. High pressure then shifts off the coast later
Thursday, affording more of a milder southerly flow Thursday night
into Friday.

Overall looking for seasonable temperatures with good diurnal
ranges, with mostly sunny skies during the day and clear/calm
nights. Highs in the mid-upper 30s for Wednesday, with the coldest
day being on Thursday with the cooler thermal profiles (low to mid-
30s); warming back into the mid 30s to lower 40s for Friday. Lows on
Wednesday and Thursday nights into the teens to lower 20s; while
lows Friday night in the mid 20s to near freezing.

Saturday into Sunday:

Still a considerable degree of uncertainty on the forecast for the
weekend, as models continue to simulate a coastal low pressure near
the Carolinas on Saturday. While today`s guidance has shown some
tendency for a south/east-of-the-benchmark track, the exact track
and resulting impacts remains uncertain.

Phasing of trough energy in the northern stream (digging south from
the Canadian Prairies) and southern stream (South Texas into the
Gulf Coast states) will prove critical in determining how close to
Southern New England this potential storm system may get. Today`s
deterministic model guidance from the GFS and ECMWF indicate this
phasing occurs late, with resulting deepening occurring south and
east of the 40N/70W benchmark. These more offshore solutions have
some support (a loose majority) from their respective ensemble
members (EPS, GEFS). This would verbatim bring a glancing blow to
the east and southeast coasts with little if any QPF in the
interior, instead supporting a colder/largely dry northwest flow.
Only the Canadian GEM brings a larger extent of the precip shield
back far enough west to permit some impacts across a larger spatial
area later Saturday into Sunday (on the western end of the
guidance). While today`s guidance indicates a more offshore track,
there does remain a number of members in the 12z GEFS and 12z EPS
that are closer to the benchmark; given this and the evolution of
this potential system hinging on aforementioned phasing, it still is
too early to lock into any solution. Lack of antecedent colder air
also opens the door for continued questions on p-type.

Given the above, and that were are still a good 6 days out with
guidance highly probable to change in subsequent days, think it is
prudent to side the official forecast fairly close to continuity,
with maybe a slight decrease in PoP in the interior given the SE
track. Chances for snow/rain are thus indicated for all locations.
Highs in the mid 30s to low 40s, and lows in the 20s.

Monday:

Some uncertainty exists on Monday depending on how weekend
developments transpire. Most guidance indicates dry conditions
under high pressure, with temperatures remaining near to
slightly above seasonal normals. Were any snowpack to be
around, again contingent on what may happen over the weekend -
could see some pretty chilly overnight lows. Stuck more closely
to a guidance blend for this period.


&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

15Z update...

Short Term...High confidence.

Through 00Z...

VFR CIGS at 040-060 for most areas through the afternoon. Local
MVFR CIGS across NW Mass, mainly across the E slopes of the
Berkshires. Mainly dry conditions, except for brief light -SHRA
and -SHSN across confined to higher terrain of N central and W
MA. W-SW winds through midday, becoming W-NW during the
afternoon.

Tonight...

VFR. Mid and high clouds dissipate. Modest W-NW winds.

Tuesday...

VFR to start but then MVFR cigs develop over high terrain and
also along eastern MA coast from Cape Ann to Cape Cod to
Nantucket along with isolated -SHSN.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday night through Thursday/ ...

Wednesday: VFR.

Wednesday Night: VFR. Breezy.

Thursday through Friday: VFR.

Friday Night: Mainly VFR, with local IFR possible. Slight
chance SHSN.

Saturday: MVFR/IFR conditions possible. Slight chance RA,
slight chance SHSN.

&&

.MARINE...
Short Term /through Tuesday Night/...High confidence.

Through this afternoon...W-SW winds 15-20 kt with gusts up to
25 kt through midday, becoming W during the afternoon. Dry
weather. Seas 4 to 7 ft on the open waters. Good visibility.

Tonight...NW winds 15-20 kt early, diminishing to around 10 kt
by around midnight. Seas up to 4 to 6 ft on the outer waters
then slowly subsiding after midnight. Dry weather and good
vsby.

Tuesday...N-NW winds 10-15 kt. Scattered rain/snow showers
eastern waters from Nantucket to Cape Cod to Cape Ann. Mainly
dry elsewhere. Seas lingering at around 5 ft E and S of Cape
Cod, otherwise 4 ft or less. Dry weather and good vsby.

Outlook /Wednesday through Saturday/...

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft.

Wednesday Night through Thursday: Winds less than 25 kt. Local
rough seas.

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Friday: Winds less than 25 kt.

Friday Night: Winds less than 25 kt. Slight chance of rain
showers, slight chance of snow showers. Local visibility 1 to
3 nm.

Saturday: Winds less than 25 kt. Chance of rain, slight chance
of rain showers. Local visibility 1 to 3 nm.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 PM EST this afternoon for
     ANZ232>234.
     Small Craft Advisory until 7 PM EST this evening for ANZ235-
     237.
     Small Craft Advisory until 6 AM EST Tuesday for ANZ250-254>256.

&&

$$
SYNOPSIS...Loconto/EVT
NEAR TERM...EVT
SHORT TERM...Nocera
LONG TERM...Loconto
AVIATION...Loconto/EVT
MARINE...Loconto/EVT