NWS Technical Forecast Discussion


Observed at
Lowell, Massachusetts
21-May-2018 10:00 PM

Temperature

67.0°F

Hour Change

-4.1°F

Humidity

47%

Hour Change

8%

Dewpoint

46.1°F

Hour Change

1.2°F

Wind

0 mph from N/A (N/A)

Wind Gust

0 mph

Barometer

30.101 inHg

3 Hour Trend

0.053 inHg

Today's Rain

0.00 in

Rain Rate

0.00 in/hr

Rain Last Hour

0.00 in

Monthly Rain

1.62 in

Yearly Rain

14.12 in

Wind Chill

67.0°F

Heat Index

67.0°F

Today Highs / Lows

High Temperature

Low Temperature

80.2°F at 03:13 PM

49.7°F at 06:02 AM

High Humidity

Low Humidity

90% at 05:56 AM

24% at 12:14 PM

High Dewpoint

Low Dewpoint

55.9°F at 12:09 AM

35.3°F at 12:14 PM

High Barometer

Low Barometer

30.154 inHg at 09:30 AM

30.003 inHg at 12:00 AM

High Wind Gust

12 mph from 343° at 04:18 PM

High Rain Rate

0.00 in/hr at 12:00 AM

Low Wind Chill

49.7°F at 06:02 AM

High Heat Index

80.2°F at 03:13 PM

Yesterday's Statistics

High Temperature

Low Temperature

77.4°F at 11:47 AM

50.7°F at 12:00 AM

High Humidity

Low Humidity

98% at 05:08 AM

66% at 07:20 PM

High Dewpoint

Low Dewpoint

69.6°F at 03:22 PM

49.6°F at 12:00 AM

High Barometer

Low Barometer

30.048 inHg at 12:00 AM

29.816 inHg at 01:36 PM

High Wind Gust

16 mph from 318° at 09:55 AM

Rain

0.18 in

High Rain Rate

0.67 in/hr at 02:14 PM

Low Wind Chill

50.7°F at 12:00 AM

High Heat Index

77.4°F at 11:47 AM

000
FXUS61 KBOX 212320
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
720 PM EDT Mon May 21 2018

.SYNOPSIS...
Dry and tranquil weather continues tonight. Rather cloudy skies
are anticipated Tuesday along with cooler temperatures. A warm
front will bring some showers to the region...generally Tuesday
afternoon and evening. Mainly dry weather Wednesday through
Saturday. Moisture increases through the weekend with the best
chance of showers on Sunday. Much warmer Friday into the
weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
7PM update...
Overall, forecast remains on track. Both cloud cover and rain
activity is going to be very slow as the column is quite dry
even at this time. With light flow developing early, some
radiational cooling should allow temps to fall into the low 50s
before the cloud shield prevents further outgoing radiation.
Lowered mins a bit.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday and Tuesday night...

A rather cloudy day is on tap for Tuesday ahead of a warm
front. There appears to be enough forcing/moisture along with a
modest low level jet for some showers Tuesday afternoon/evening.
Not expecting a complete washout...but most locations should
see a period of wet weather during this time. There is even a
low risk for a rumble or two of thunder...mainly near the south
coast with some marginal elevated instability. High temperatures
will be held in the upper 60s to around 70 in most locations
given the clouds along with the afternoon/evening showers.

The bulk of the showers should come to an end Tuesday
evening...but a few will remain possible after midnight as a
weak cold front crosses the region. Clouds will probably hang
tough for most of the night and may see some fog develop given
ample low level moisture. This should hold overnight low
temperatures in the lower to middle 50s.

&&

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

* A spot shower lingers Wednesday
* Cool Thursday but much warmer into the weekend
* Risk of showers increases by Sunday

Overview...
Through the mid term, the N stream dominates, mainly in the
form of a longwave trof settling across the Maritimes which is
linked to a Baffin Sea vortex. However, with the mean trof axis
to the W, central CONUS ridging will lead to rising heights and
generally cyclonic flow through the latter half of the week. It
is not until the tropical disturbance in the Gulf of Mexico gets
caught up with shortwave energy moving out of the Pacific that
there is a transition for New England. These impacts,
particularly with a plume of tropical moisture, could yield a
wet latter half of Memorial Day weekend. Overall, enough
agreement between guidance to use a consensus blend for this
forecast update.

Wed...
Cold front slows as it begins to parallel mid lvl flow.
However, soundings support rapid influx of drier air through the
column, reducing PWATs to below 1.00in by mid day. Although
this does steepen lapse rates, the overall lack of moisture may
limit convective potential. Near NIL QPF supports this thinking.
Still enough to warrant at least slight chance POPs. Delayed
cold advection suggests highs should reach the mid 70s to around
80, especially as some clearing is observed.

Thu through Sat...
Mainly dry thanks to implied ridging through mid and upper lvl
height rises and sfc high pres as a response. Thu looks to be
the coolest day, but with H85 temps avg around +8C, it still
should yield low 70s across much of the region. Milder Fri and
Sat with temps in the upper 70s and low 80s thanks to a gradual
increase in mid lvl temps. These are best observed inland
however, as weak pres gradient suggests local sea breezes at
area coastlines.

Sun into early next week...
Echo previous forecasters concern and lack of overall
confidence as guidance widely diverges during this period. This
is not surprising, as models often struggle with complex
tropical interactions. At odds for New England, is a resurgence
in N stream forcing trof out of the Arctic with its sfc
response, a N-S moving cold front front which makes temperatures
rather uncertain. From the S stream, is tropical moisture plume
with PWATs potentially reaching near 2.00 inches just to the S.
If this dominates a period of wet and very unsettled conditions
are possible, keeping the front to the N. For now, will lean
most heavily on ensemble means for this period as it takes into
account the potential solutions. This will come into focus
better as the feature players, particularly the tropical wave
become better sampled.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

Short Term /through Tuesday Night/...

Tonight...High confidence.
VFR.  Winds becoming light and variable.

Tuesday and Tuesday night...Moderate to high confidence. Mainly
VFR conditions into Tuesday afternoon. It probably will take
until evening especially along the coast for MVFR to localized
IFR ceilings and visibilities to arrive. These lower cigs/vsbys
will likely persist Tuesday night. Some showers expected
especially Tuesday afternoon and evening. A low risk for a
rumble or two of thunder mainly near the south coast Tue
evening.

KBOS Terminal...High confidence in TAF. Still uncertainty though
in wind direction through 22z. BOS sea breeze kicked offshore as
of 19z...but still close enough where it needs to be watched for
another few hours.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday through Saturday/...Moderate confidence.

Wednesday: Mainly VFR.

Wednesday Night: VFR. Breezy.

Thursday through Thursday Night: VFR.

Friday through Friday Night: VFR. Breezy.

Saturday: Mainly VFR, with areas MVFR possible. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Tuesday Night/...

Tonight through Tuesday night...High confidence. Weak pressure
gradient will keep winds and seas below small craft advisory
thresholds through Tuesday night. Biggest concern for mariners
will be the potential for some fog developing Tuesday night
along with the low risk for a rumble or two of thunder across
our southern waters.

Outlook /Wednesday through Saturday/...Moderate confidence.

Wednesday: Winds less than 25 kt. Slight chance of rain
showers, patchy fog. Local visibility 1 to 3 nm.

Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft. Patchy fog. Local visibility 1 to 3 nm.

Thursday through Thursday Night: Winds less than 25 kt.

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

Friday Night: Winds less than 25 kt. Areas of rough seas.

Saturday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

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

NWS BOX Office Area Forecast Discussion