Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KBOX 241123
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
723 AM EDT Sun Mar 24 2019

.SYNOPSIS...
High pressure over the Mid Atlantic states provides dry but much
milder temperatures this afternoon. However a trend toward cooler
weather arrives Monday as a dry cold front sweeps across the region.
Dry weather prevails much of next week with chilly weather Tue
gradually moderating as the week progresses.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
715 AM update...

The FEW CI have dissipated this morning as the very weak vort-
max has shifted further to the SE. Plenty of sunshine, plus a W
component to the flow will allow mixing to be fully realized
today especially where downsloping can be maximized. Therefore,
still anticipating highs in the 50s to near 60 across the
region. Pres gradient remains in play however, so breezy
conditions can be expected, though not as strong as yesterday.

Previous discussion follows...

Short wave ridging across the region and associated 1026 mb high
pressure over the Mid Atlc provides dry weather across southern New
England today. However low level WAA commences ahead of approaching
cold front from the north this afternoon. This results in 925 mb
temps warming from about -1C early this morning to +5C this
afternoon. Model soundings indicate blyr mixing up to about 900 mb.
This combined with abundant sunshine and WNW winds becoming WSW this
afternoon will support highs in the mid to upper 50s. Even a low
prob some locations away from the south coast briefly touch 60!
Quite the difference from Saturday`s blustery conditions. Coolest
temps this afternoon along and near the south coast with highs in
the low 50s early this afternoon then falling into the 40s as winds
shift to the SW off the chilly ocean waters.

&&

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

Cold front slowly sags southward to near the south coast by sunrise
Monday. Modest lift associated with short wave trough and attending
cold front but model cross sections reveal lots of dry air below 10
kft. Thus not expecting much than a spot shower or sprinkle second
half of the night. Most locations remain dry. Not as cold as
previous nights given prefrontal airmass, with lows mainly in the
30s.

Monday ...

Cold front along or near the south coast at sunrise. As mentioned
above lots of dry air below 10 kft. Thus just expecting an abundance
of mid clouds with just the low risk of a spot morning shower or
sprinkle. Otherwise front moves offshore with sunshine developing
from north to south. Core of cold air lags and holds off until Mon
night into Tue. Thus seasonable temps Monday with highs 45-50.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
* Dry through the week with high pressure building over the region
* Colder weather through mid week, then temperatures look to
  rebound late next week

Overview and model preferences...
Overall, noting fairly good agreement between both ensemble and
operational guidance with the 24.00Z guidance update. The only
caveat, unsurprisingly, is toward the end of the 7 day period,
dealing with two separate waves, one from the Pacific, the other
moving out of NW Canada. As such, there remains timing, and
strength differences regarding low pres and attendant frontal
passage for late next weekend. Overall, a consensus blend will
be used given the agreement early, and the uncertainty late, to
take into account differences.

Mon night into Wed...
Coldest stretch of the long term. Deep cutoff settles across
Quebec and Labrador, allowing H85 temps to drop near seasonal
record lows per SPC sounding climatology. This range is general
-14C to -16C on Tue which should limit highs to the upper 30s
and low 40s. Milder Wed, closer to seasonal normals thanks to
mixing likely exceeding H85. Overnight mins coldest Tue and Wed
nights as high pres crests, yielding good setup for radiational
cooling.

Thu and Fri...
More spring like as H85 temps approach 1 std deviation above
normal, or around +5C to +7C. This should allow highs Thu to
move into the upper 40s to mid 50s and potentially approaching
60F by Fri. Dry wx continues under high pres influence even as
modest mid lvl warm advection occurs. One fly in the ointment,
will be sea breezes given light sfc flow and cool SSTs in the
40s. So coastal areas likely remain cooler.

Next weekend...
Will be watching the gradual approach of low pres and attendant
cold front. Given there is at least a loose link to subtropical
moisture, anticipate there will be a period of precipitation,
but timing remains somewhat uncertain. Mild conditions continue
until this frontal passage.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

Short Term /through Monday/...

Today ...
VFR. A few mid/high clouds work in later today. WSW winds with
a few gusts 20-25 kt dissipating somewhat this evening.

Tonight ...

VFR and dry during the evening along with WSW winds. After 06z
VFR cigs OVC100 along with a spot shower or sprinkle possible.
WSW winds shifting to NW.

Monday ...

MVFR in the morning, mainly south coast with low risk of a spot
shower/sprinkle, then trending VFR from north to south along
with dry conditions. North winds.

KBOS terminal...High confidence in TAF.

KBDL terminal...High confidence in TAF

Outlook /Monday Night through Thursday/...

Monday Night through Thursday: Mainly VFR. Daily sea breezes
possible especially Tue-Thu.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Monday/...

Today ...

Modest WNW winds 15-20 kt with gusts up to 25 kt then winds shifting
to the WSW ahead of an approaching cold front. Dry weather and good
vsby prevail.

Tonight ...

Dry cold front moves across southern New England. WSW winds become
NW toward daybreak as cold front slips toward the south coast.

Monday ...

WSW winds becoming NNW by midday as dry cold front moves offshore.

Outlook /Monday Night through Thursday/...

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for
     ANZ231>235-237-254>256.

&&

$$
SYNOPSIS...Nocera/Doody
NEAR TERM...Nocera/Doody
SHORT TERM...Nocera
LONG TERM...Doody
AVIATION...Nocera/Doody
MARINE...Nocera/Doody



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.