NWS Technical Forecast Discussion


Observed at
Lowell, Massachusetts
21-May-2018 12:20 PM

Temperature

74.7°F

Hour Change

3.4°F

Humidity

26%

Hour Change

-10%

Dewpoint

37.5°F

Hour Change

-5.4°F

Wind

3 mph from 307° (NW)

Wind Gust

6 mph

Barometer

30.132 inHg

3 Hour Trend

-0.019 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

74.7°F

Heat Index

74.7°F

Today Highs / Lows

High Temperature

Low Temperature

74.7°F at 12:17 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

9 mph from 5° at 08:34 AM

High Rain Rate

0.00 in/hr at 12:00 AM

Low Wind Chill

49.7°F at 06:02 AM

High Heat Index

74.7°F at 12:17 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 211332
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
932 AM EDT Mon May 21 2018

.SYNOPSIS...
Dry weather is in store through tonight. Cooler with passing
showers Tuesday afternoon as a warm front approaches. Showers
are still likely Tuesday night as weak low pressure moves
across the region. Mainly dry weather Wednesday through Friday.
Moisture increases through the weekend with the best chance of
showers on Sunday. Much warmer Friday into the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

930 am update...

High pressure in control will result in continued sunny skies,
light winds and a beautiful afternoon along with low humidity.
Highs will mainly top out in the upper 70s to around 80...but a
bit cooler along the immediate coast with sea breezes developing
given weak pressure gradient.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
High pressure moves through our region tonight. Winds turn SW,
starting the warm air advection process. Only impact should be
increasing mid and high level clouds. Light winds to start
should lead to modest radiational cooling conditions before the
clouds arrive, especially with the lower dew points. Preferred
the lower MOS-based minimum temperatures.

For Tuesday, a passing mid level shortwave and a low pressure
moving into the Great lakes should be enough to warrant at least
a chance of showers. Low and mid level lapse rates expected to
be rather poor to start the day. While low level lapse rates are
unlikely to favor thunderstorms, mid level lapse rates may
steepen just enough later in the afternoon and evening where a
few thunderstorms may develop. Many more clouds in place, so
expecting temperatures to be 5-10 degrees lower than Monday, still
near to slightly below normal.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Highlights...

* Showers likely Tuesday night
* Cool Thursday but much warmer into the weekend
* Risk of showers increases by Sunday

Overview...

A northern stream trough will amplify to the north and east Wed
into Thu which will push a cold front through the region.
Rising heights and shortwave ridging follow Fri into Sat then
the next northern stream trough approaches Sunday.

Tuesday night...Low pressure moves across New England and off
the coast late. Showers are likely in southeastern MA and RI
with more scattered showers farther to the north and west.
Although there is no surface instability, some marginal elevated
instability could support an isolated thunderstorm.

Wednesday...Early morning cloudiness gives way to mostly sunny
skies. However, an approaching cold front could trigger widely
scattered showers in eastern MA where there will be a weak
trough, CAPE of 500-1000 J/kg, and a narrow axis of K Indices of
32. Highs 75-80 away from the coast.

Thursday...Sunny skies but 850 mb temperatures will have cooled
from +13C Wed to +8C on Thu. Winds will be light NW inland but
NE at the coast. Expecting highs 70 to 75 inland but cool upper
50s to lower 60s along Cape Ann, Cape Cod, and the Islands.

Friday...High pressure to our southeast and weak low pressure
over northern New England will lead to a westerly downsloping
flow of air across southern New England. That, coupled with
ridging at 500 mb will lead to a much warmer day. Right now am
calling for 80-85 away from the coast, but it is possible to see
a few upper 80s readings.

Saturday and Sunday...In general, moisture will be increasing
through the weekend as flow aloft shifts to the southwest.
Increasing precipitable waters as deep tropical plume that has
been sitting along the southeast U.S. coast edges its way
through the mid-Atlantic and we begin to get on the northern
fringes of the moisture. K Indices increase to the mid 30s in
southwestern CT by Sunday. Thus scattered showers on Saturday
will become more numerous by Sunday. Cannot rule out scattered
thunderstorms, too.

In addition, a warm front will be in the vicinity. Its location
will have major ramifications for the temperature forecast. If
it moves completely northward through the region, then highs
both Sat and Sunday could be well up into the 80s to near 90 in
a few spots. But, as the GEM has been hinting, there is a chance
that it only bisects the region and the northeast portions of
the region could be stuck in the 60s. For now, have blended the
models and gone a few degrees higher than the blend, which
yields 80-85 inland Sat and 77-81 Sunday, but again, these are
subject to much change.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

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

Through tonight...VFR with winds less than 10 kt. Local
seabreezes from mid morning into early evening.

Tuesday...VFR. SHRA moving from west to east across southern New
England during the day. Low risk for a few -TSRA, too.

KBOS Terminal...High confidence in TAF. Sea breeze should
develop between 14 and 16z.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...Moderate confidence.

Tuesday Night: MVFR with areas of IFR. Showers likely. Areas of
fog.

Wednesday: VFR. Slight chance SHRA, mainly eastern MA.

Wednesday Night through Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

We have dropped the remainder of the small craft headlines as
seas have dropped below 5 feet. Winds will remain rather light
across the coastal waters through Tuesday. Some showers arrive
across the waters during Tuesday afternoon, and continue into
the evening hours. Low risk for a few rumbles of thunder, too.

Outlook /Tuesday Night through Friday/...Moderate confidence.

Tuesday Night: Winds less than 25 kt. Showers likely. Areas of
fog with visibility reduced to 3 nm or less.

Wednesday: Winds less than 25 kt. Slight chance of a shower.

Wednesday Night through Thursday night: Winds less than 25 kt.

Friday: Winds less than 25 kt. Seas approaching 5 ft southern
and eastern outer waters toward evening.

&&

.FIRE WEATHER...
Spotty locations received as much as 0.5 inches of precipitation
this past weekend, but several locations received less. Given
fuels were dry, this may not have been enough to fully moisten
them. RH values Monday will drop as low as 25 percent inland,
but winds should remain light out of the NW, around 10 mph most
of the day.

&&

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

&&

$$
SYNOPSIS...Belk/GAF
NEAR TERM...Frank
SHORT TERM...Belk
LONG TERM...GAF
AVIATION...Frank/Belk/GAF
MARINE...Frank/Belk/GAF
FIRE WEATHER...Staff

NWS BOX Office Area Forecast Discussion