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FXUS61 KBOX 250958
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
458 AM EST Tue Feb 25 2020

.SYNOPSIS...

A weak cold front will drop south across the region today with a
wind shift to northeast but it will be another mild day. Other than
a period of light rain this morning over Nantucket, mainly dry
conditions are expected today. The front will settle south of New
England tonight and Wednesday with a moist northeast flow bringing
patchy light rain and drizzle at times. Low pressure lifts
slowly northeast Wednesday night into Thursday, bringing an area
of rain across the region with a wintry mix or a period of
light snow across the higher terrain of north central and
northwest Massachusetts. As the low exits, cold and blustery
conditions move in for Friday into next weekend, along with some
scattered snow showers at times across the high terrain. High
pressure slowly moves across the eastern third of the country
early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Mid level shortwave passage this morning combined with deep moisture
lifting north from the ocean will bring a period of rain to mainly
Nantucket this morning. Hi-res and global guidance are indicating a
few hours of rain here which may also briefly impact portions of the
Cape. The rain which impacts Nantucket is developing off NJ coast
and lifting NE. Otherwise, weak subsidence behind the shortwave and
subtle drying in the column should result in a mainly dry day
although can't rule of some light rain/drizzle late in the day south
of the Mass Pike as moisture returns from the south and west. 925 mb
temps remain mild today and with a bit of sunshine possible, highs
should reach into the mid 50s away from the coast with some upper
50s possible, except cooler northern MA as weak cold front drops
south across SNE with a wind shift to NE. This wind shift will
result in temps falling through the 40s along east coastal MA
during the afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Tonight...

Weak front sets up south of New Eng with a sfc wave tracking along
the boundary to the south. Weak warm advection and deep moisture
through the mid levels should bring some light rain/drizzle to the
region, which may mix with some snow late tonight and Wed morning
over the higher elevations in far northern MA where the column is
marginally cold enough. Little or no accum is expected. Lows will
range through the 30s with light NE winds.

Wednesday...

Mid level trough amplifies from the Gt Lakes to the Ohio valley with
downstream ridge building over New Eng. Mid level drying from the
south moves up across SNE during the day. Low levels will be rather
moist so low clouds expected with some patchy light rain/drizzle at
times but most of the day should be mainly dry. Leading edge of
steadier rain will be approaching from the west but should hold off
until Wed night. Low clouds and NE wind will result in cooler temps
with highs upper 30s to mid 40s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...

Highlights...

* Low pressure will slowly push NE across the region Wed night
into Thursday, bringing an area of rain and increasing E
winds. A wintry mix is forecast for the higher terrain of N
central and NW Mass.

* Strong cold front crosses the region by midday Thursday as
winds to W during the day, bringing colder air along with some
light snow or a wintry mix across N central and NW
Massachusetts

* Dry and blustery conditions on Friday with well below normal
temperatures. Wind chills values in the single digits and
teens early. Remains cold and dry this weekend.

* High pressure slowly moves toward the region early next week
with slowly moderating temperatures.

Details...

Wednesday night through Thursday night...

Low pressure will slowly push across the mid Atlc states as a
secondary low tries to form off the Delmarva peninsula early Wed
night. With high pressure sitting across eastern Quebec and
Labrador, a strong easterly fetch will keep a steady stream of
moisture across the region. Noting increased PWATs (around 1")
on the 00Z NAEFS anomaly, with a 1-2 SD above normalized values
moving across the region on Thu night. Rather strong mid level
jet crosses the region as well.

Looks like best shot for a quick hit of precip will cross the
region Wed night into Thu morning, then will shift NE as the
system shifts into northern New England. Current forecast
suggests QPF values around 0.5 to around an inch. However, may
see PTYPE issues across the highest terrain of N Central Mass
and the E slopes of the Berkshires. 00Z models suggest that
there could be a light snow or mixed precip accumulations there
with the E-NE flow and decent cold air damming in place. As the
front and low pres lifts N Thu morning, should see the steadier
precip lift out of the region. Precip may linger through midday
across the Route 2 area.

As winds shift to W, colder air will filter in after 18Z across
central and western areas. Temps on Thu will range from the mid
30s to around 40 well inland to the mid-upper 40s across the
coastal plain. As the colder air shifts to the coast by evening,
W winds will increase with the increasing low level mixing.
Gusts will increase to 25-30 kt, highest along the immediate
coast Thu night, possibly up to 35 kt at times across the
southern islands.

Friday through Monday...

Overall mid level steering pattern undergoes major shift as the
cutoff 510 dm cutoff H5 low slowly lifts across northern New
England and eastern Canada. Long wave trough keeps as steady
westerly flow in place, so will see a dry but cold regime in
place through a good portion of the upcoming weekend.

May see some scattered lake effect snow showers reach the E
slopes of the Berkshires at times Fri into Fri night. Otherwise,
should see dry conditions. The large cold pool aloft moves
across central and northern New England Fri night/Sat. By
Sunday, the H5 trough should slowly but steadily shift offshore,
but a NW wind flow will bring the coldest air across Sat night.

Expect high temps from Friday through Sunday to run anywhere
from 5 to as low as 15 degrees below normal, the coldest
readings across the E slopes of the Berkshires. Highs will
range from the mid 20s to lower 30s across the higher terrain to
the mid and upper 30s across the coastal plain on Friday and
Saturday, falling to the 20s to mid 30s on Sunday.

N-S oriented ridge builds from Quebec to Florida by Monday
morning, so winds will diminish and temps will start to rebound.
High temps will range from the mid 30s across the higher
terrain to between 35 and 40 along the coast.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

Through 12z...
VFR cigs, but MVFR/IFR cigs with a period of rain will
overspread ACK 10-12z.

Today...Moderate confidence.
IFR cigs ACK should improve to VFR by midday with rain exiting
by 14z. Otherwise VFR cigs trending to MVFR south coast and Cape
Cod toward evening. Light winds becoming NE

Tonight...Moderate confidence.
Cigs becoming widespread MVFR with areas of IFR. Patchy light
rain/drizzle and fog developing. Light NE winds.

Wednesday...Moderate confidence.
MVFR/IFR cigs with patchy drizzle/fog at times. NE winds 5-15
kt.

KBOS Terminal...Moderate confidence in TAF.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Mainly IFR, with areas MVFR possible. Windy
with gusts up to 35 kt. RA, FZRA.

Thursday: MVFR/IFR conditions possible. Windy with gusts up to
35 kt. Chance RA.

Thursday Night: VFR. Windy with gusts up to 30 kt.

Friday: VFR. Windy with areas of gusts up to 30 kt.

Friday Night: VFR. Windy with local gusts up to 30 kt.

Saturday: VFR.

&&

.MARINE...

Today...High confidence. Light SW winds turning NE across NE MA
waters in the afternoon.

Tonight and Wednesday...High confidence. NE winds increasing to 10-20
kt late tonight into Wed with building seas. Gusts to 25 kt
developing by late Wed.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Low risk for gale force winds with gusts up to
40 kt. Rough seas up to 11 ft. Rain, patchy fog. Local
visibility 1 to 3 nm.

Thursday: Low risk for gale force winds with gusts up to 40 kt.
Rough seas up to 12 ft. Chance of rain.

Thursday Night: Moderate risk for gale force winds with gusts
up to 35 kt. Rough seas up to 12 ft.

Friday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 11 ft.

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

Saturday: Winds less than 25 kt. Local rough seas.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from late Wednesday night through Thursday
afternoon for ANZ250-254.
Gale Watch from late Wednesday night through Thursday
afternoon for ANZ251.
Small Craft Advisory from 4 AM to 7 PM EST Wednesday for
ANZ255-256.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT
MARINE...KJC/EVT
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