NWS Technical Forecast Discussion


Observed at
Lowell, Massachusetts
18-Feb-2018 10:30 PM

Temperature

30.1°F

Hour Change

-0.5°F

Humidity

72%

Hour Change

1%

Dewpoint

22.2°F

Hour Change

-0.2°F

Wind

0 mph from 240° (WSW)

Wind Gust

1 mph

Barometer

30.511 inHg

3 Hour Trend

0.072 inHg

Today's Rain

0.46 in

Rain Rate

0.00 in/hr

Rain Last Hour

0.00 in

Monthly Rain

2.68 in

Yearly Rain

3.71 in

Wind Chill

30.1°F

Heat Index

30.1°F

Today Highs / Lows

High Temperature

Low Temperature

43.3°F at 03:23 PM

28.8°F at 07:30 AM

High Humidity

Low Humidity

96% at 08:03 AM

48% at 03:40 PM

High Dewpoint

Low Dewpoint

32.7°F at 09:53 AM

22.0°F at 10:22 PM

High Barometer

Low Barometer

30.513 inHg at 10:28 PM

29.892 inHg at 03:45 AM

High Wind Gust

24 mph from 355° at 11:59 AM

High Rain Rate

0.45 in/hr at 10:19 AM

Low Wind Chill

22.8°F at 06:33 AM

High Heat Index

43.3°F at 03:23 PM

Yesterday's Statistics

High Temperature

Low Temperature

38.2°F at 01:50 PM

23.3°F at 07:10 AM

High Humidity

Low Humidity

94% at 10:45 PM

27% at 01:49 PM

High Dewpoint

Low Dewpoint

29.1°F at 11:45 PM

6.6°F at 01:12 PM

High Barometer

Low Barometer

30.415 inHg at 08:34 AM

30.052 inHg at 11:43 PM

High Wind Gust

19 mph from 336° at 12:00 AM

Rain

0.00 in

High Rain Rate

0.00 in/hr at 12:00 AM

Low Wind Chill

14.3°F at 07:38 AM

High Heat Index

38.2°F at 01:50 PM

000
FXUS61 KBOX 190311
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1011 PM EST Sun Feb 18 2018

.SYNOPSIS...
A warm front will likely bring a period of showers late Monday
into Monday night. This will bringing near record high
temperatures Tuesday and Wednesday. A cold front Wednesday night
will bring showers and then cooler temperatures, but still at
or above seasonal normals. Another weather system will pass to
our west and north over the weekend bringing another period of
wet weather.

&&

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

10 PM Update...

High pressure cresting across the region this evening. Noting
a veil of high thin cirrus crossing the region on latest GOES-
East Air Mass RGB composite satellite loop. Even with the high
clouds, the calm winds across the majority of the region have
allowed for temps to drop below forecast levels through the
evening. Have adjusted downward, especially across Cape Cod
where readings have been as much a 5 degrees below forecast
levels. However, suspect that the temps will level off or even
rise a bit after midnight as the high pushes E of the region,
which will allow winds to become light S.

Remainder of this evening`s forecast on track, but did update to
incorporate near term trends.

Previous discussion...

Large high pressure will pass by just to the south of New
England tonight. This will mean diminishing wind this evening,
especially overnight. Once this high pressure approaches the
Maritimes late tonight, a light south wind should develop.

Decent radiational cooling conditions tonight. Expecting lows to
be mainly in the 20s. This should be sufficient to refreeze any
standing water into black ice on untreated surfaces.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Increasing south winds will boost temperatures well above
normal Monday, and likely keep temperatures nearly steady or
slowly rising Monday night.

Morning sunshine. Increasing clouds during the afternoon as a
warm front approaches. There appears to be enough forcing and
moisture for a likely period of showers sometime late afternoon
into Monday night. Chance for showers should decrease after
midnight Tuesday as a warm front moves into northern New
England. It should remain mostly cloudy, though.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Big Picture...

Upper ridges build over the Eastern USA and the East Pacific with a
deep trough over the Western USA. Contour heights over Southern New
England reach 585 dm, well above the normal 542-545 dm for February.
These values lower over the Northeast USA Thursday-Friday but still
remain well above normal most of the weekend. Several weak
shortwaves eject from the western trough Wednesday through Sunday,
with the strongest moving through the Northeast during the weekend.

Model large-scale mass and thermal features are in general agreement
through Friday, with some differences Saturday-Sunday.

Details...

Tuesday-Wednesday...

With the upper ridge building so strong and with the surface front
moving north to the Canadian border, a period of near record warmth
is anticipated. Warm advection aloft is expected to limit mixing to
about 950 mb where temps support sfc highs of 60 to 65 Tuesday and
65 to 70 Wednesday. South coastal areas will be affected by the cold
ocean temps and thus stay in the 50s. Model cross sections show high
moisture below 900 mb and dry air above 800 mb. If this moisture is
realized as clouds, it could keep all max temps in the 50s each day.
We compromised, with highs around 60 on Tuesday when there is a
higher chance of clouds.

Wednesday night-Thursday...

A shortwave supported by a 190-knot upper jet races across Eastern
Canada. New England falls under the right entrance region of the jet
during this time. This will draw the front south across New England.
There are differences in timing of cold fropa with the ECMWF showing
a Wednesday evening passage while the GFS shows passage Wednesday
night/Thursday morning. Low pressure waves forming along the front
could slow the progress of the front.

Expect showers during this time, and we will use the slower
Wednesday night timing. The model PW fields show a band of high
moisture content extending from the Western Gulf of Mexico to New
England. PW values over us reach to about 1.3 inches, which is
nearly record territory. Convective parameters are interesting with
totals in the mid to upper 40s and mid level lapse rates 6 to
6.25C/Km. Locally heavy downpours are possible. Would not rule out
some thunder, but the probability is too low to mention at this
time.

Friday through Sunday...

High pressure from the Northern Plains moves east to New England,
bringing clearing skies for Thursday night. Clouds then move back in
during Friday.

The next shortwave climbs out of the western trough and races
northeast in the fast-moving flow. Models currently show a second
shortwave on the heels of the first. The projected track of the low
favors rain for Southern New England, but with concern that some low
level cold air could bring a brief period of mixed precipitation
Friday night. The trend is for rain everywhere by Saturday.

The second shortwave would then maintain a chance of rain into
Sunday. Much uncertainty remains with timing of this feature.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

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

Overnight...VFR. Light/variable or calm winds becoming light S
after 05Z.

Washington`s Birthday: Mainly VFR, with local MVFR possible
late. Breezy. Chance SHRA late.

Monday Night: Mainly VFR, with areas of MVFR in -SHRA. Areas
IFR possible toward the south coast, including the Cape and
islands.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday through Friday/...Moderate to High confidence.

Tuesday: MVFR conditions possible, especially South Coast.
Breezy. Patchy BR early.

Tuesday Night: Mainly VFR, with local IFR possible. Breezy.

Wednesday: Mainly VFR, with local MVFR possible. Breezy.

Wednesday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, patchy BR.

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

Thursday Night: VFR.

Friday: VFR. Slight chance RA in the afternoon.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

Overnight...Seas have subsided below 5 ft so have allowed the
Small Crafts to expire at 03Z. Light/variable winds shift to
S after midnight. Good visibility.

Washington`s Birthday into Monday night...Increasing S winds,
resulting in build seas across the outer coastal waters. Small
Craft Advisories will likely be needed across the outer coastal
waters. Will post those, once the current set of advisories has
expired. Chance of rain showers. Patchy fog possible Monday
night with visibility of 1 to 3 nm.

Outlook /Tuesday through Friday/...Moderate to High confidence.

Tuesday through Tuesday Night: Winds less than 25 kt. Local
rough seas. Slight chance of rain showers.

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Local rough seas.

Wednesday Night: Winds less than 25 kt. Local rough seas.
Chance of rain showers.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.

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

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain late.

&&

.CLIMATE...
Record Highest Observed Temperature for February...
(since records began)

Boston.........73 (02/24/2017)
Hartford.......73 (02/24/1985)
Providence.....72 (02/24/1985)
Worcester......69 (02/24/2017)

Record High Temperatures (Tuesday 20th / Wednesday 21st)...

February.......20th......21st.....

Boston.........68 (1930) 63 (1906)
Hartford.......69 (1930) 63 (1930)
Providence.....69 (1930) 63 (1930)
Worcester......65 (1930) 59 (1930)

Record Warmest Low Temperature...

February.......20th......21st.....

Boston.........46 (1930) 45 (1994)
Hartford.......50 (1981) 49 (1981)
Providence.....48 (1981) 50 (1981)
Worcester......47 (1981) 43 (2002)

&&

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

&&

$$
SYNOPSIS...WTB/Belk
NEAR TERM...WTB/EVT
SHORT TERM...Belk
LONG TERM...WTB
AVIATION...WTB/Belk/EVT
MARINE...WTB/Belk/EVT
CLIMATE...Staff

NWS BOX Office Area Forecast Discussion