NWS Forecast Area Discussion - New England Area

378
FXUS61 KBOX 200202
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1002 PM EDT Thu Apr 19 2018

.SYNOPSIS...
An upper level disturbance moves east of Massachusetts
overnight, ending any remaining rain and snow showers. Drier
air moves in on Friday as high pressure over the Great Lakes
Region moves eastward. Building high pressure will bring
gradually warming temperatures and dry weather into early next
week. Storm system expected for mid to late week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...

Upper level low and cold pool pver New England early in the
night with clouds covering the region and radar showing
scattered light rain/snow showers over the region. The trough
moves east of Southern New England by morning, taking with it
the support for any showers. Moisture aloft trends less with
time, so expect partial clearing from the south overnight.

Gusty northwest winds observed around 22 knots. Mixing continues
overnight as the cold pool and strong lapse rates continue to
bring some winds to the surface overnight.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Friday...

Cyclonic flow around the upper low continues on Friday. Models
continue to show a decrease in overall moisture over the course of
the day, however sufficient moisture in the low levels for diurnal
cumulus/stratocu. Mainly dry conditions expected, though could
see some spot showers along the east slopes of the Berkshires, and
a few sprinkles elsewhere.

The cold advection and cold temperatures aloft should allow
mixing to at least 850 mb. Models continue to show winds in this
layer around 25 knots, so NW gusts of 25-30 mph anticipated for the
afternoon. Highs generally in the mid 40s to low 50s, except for low
40s along the east slopes of the Berkshires. For most of the region
this is a good 10 degrees or so below normal for mid April.

Friday night...

Upper trough lifts east of the area while surface high pressure over
the Great Lakes Region moves eastward. This allows for drier air and
skies becoming mostly clear. Diminishing NW winds become light,
with lows in the upper 20s and 30s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...

* Moderating temperatures and dry weather will prevail through the
  weekend and into next week
* Next batch of rainfall will occur during the mid-week

Overview...

Longwave wave trough over the Northeast will lingering through the
weekend before mid-level ridging pushes through for early next week.
At the surface, strong high pressure leaning towards 2-3 STD above
normal will lead to dry weather. However with the upper level
trough, temps will slowly moderate out through next week. By
Tuesday/Wed, both the GFS and EC indicate a cut-off 500mb low
associated with the southern stream. This southern stream could
interact with an approaching northern stream wave, developing a
system for mid next week. This is supported by ensemble guidance
which has between 50-70 percent probs of seeing 0.5 inches of
rainfall.

Details...

Temperatures...Moderate confidence.

Spring will make an appearance during this medium range forecast as
temperatures will begin to moderate through the weekend and into
next week. Longwave trough over the region will slowly begin to exit
towards the Maritimes by early next week. This will keep the weekend
below average for temperatures as both 925 and 850mb are near 1-2
STD below normal. Still plenty of sunshine across the area for the
weekend with fairly light winds so it will feel pretty warm
compared to this past week.

Mid-level ridge will build into the area by Monday/Tuesday. This
will help increase temperatures back into the low to mid 60s. Near
the coastline, temperatures will feel cooler due to potential sea
breeze develop as high pressure is situated right over the area.

Approaching system for the mid-week will drop temperatures back down
below average, especially behind the system.

Precipitation...High confidence.

Dry weather will prevail from Saturday into Tuesday thanks to
surface high building in from the west. Model guidance indicates
this high will near 2-3 STD above normal. A good break to dry out
the soils. However, approaching surface low that develops near the
Carolinas will track towards southern New England between Wednesday
and Thursday bringing wet weather to the area. As mentioned above,
ensemble guidance has between 50-70 percent probability of seeing
0.5 inches of rainfall. Chances are this amount will go up
especially since this event is still 6+ days out and there is strong
agreement amongst the ensembles and deterministic guidance.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Friday Night/...

Overnight...Moderate confidence. Lingering MVFR cigs over Cape
Cod and Islands will improve to VFR overnight. VFR over the rest
of Southern New England overnight. Sky cover diminishes from the
south and southwest overnight.

Friday...High confidence. VFR. Northwest winds will gust to 25
knots during the day. Isolated -SHRA/-SHSN possible along the
east slopes of the Berkshires, this could briefly cause MVFR
cigs/vsbys. Elsewhere patchy sprinkles possible.

Friday night...High confidence. VFR.

KBOS Terminal...High confidence in TAF. VFR. Gusty NW winds on
Friday preclude sea breeze development.

KBDL Terminal...High confidence in TAF. VFR.

Outlook /Saturday through Tuesday/...High confidence.

VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Friday Night/...High confidence.

Overnight... A low pressure system moves off south of Nova
Scotia overnight. Increasing northwest winds expected tonight,
gusting 25 to 30 kts at times. Seas will build overnight, with
5-8 foot seas on the southern outer coastal waters overnight.
Small craft advisory continues for all waters.

Friday...Northwest winds gusting to 25 knots, with seas 5-7
feet on the outer coastal waters. Small Craft Advisory in effect.

Friday night...Northwest winds gust 20-near 25 kts with seas
gradually subsiding. A Small Craft Advisory may be needed for the
outer coastal waters.

Outlook /Saturday through Tuesday/...Moderate

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

Saturday Night through Tuesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 2 AM to 3 PM EDT Friday for
     ANZ231>234-251.
     Small Craft Advisory from 4 AM to 6 PM EDT Friday for ANZ230.
     Small Craft Advisory from 4 AM to 11 AM EDT Friday for ANZ236.
     Small Craft Advisory until 5 PM EDT Friday for ANZ235-237.
     Small Craft Advisory until 6 PM EDT Friday for ANZ250.
     Small Craft Advisory until 8 PM EDT Friday for ANZ254>256.

&&

$$
SYNOPSIS...WTB/Dunten/NMB
NEAR TERM...WTB/Dunten/NMB
SHORT TERM...NMB
LONG TERM...Dunten
AVIATION...Dunten/NMB
MARINE...WTB/Dunten/NMB

NWS BOX Office Area Forecast Discussion