NWS Technical Forecast Discussion


Observed at
Lowell, Massachusetts
01-20-2020 08:00 AM

Temperature

13.6°F

Hour Change

-0.5°F

Humidity

67%

Hour Change

0%

Dewpoint

4.7°F

Hour Change

-0.5°F

Wind

6 mph from 315° (NW)

Wind Gust

15 mph

Barometer

30.128 inHg

3 Hour Trend

0.130 inHg

Today's Rain

0.00 in

Rain Rate

0.00 in/hr

Rain Last Hour

0.00 in

Monthly Rain

1.49 in

Yearly Rain

1.49 in

Wind Chill

4.3°F

Heat Index

13.6°F

Est. Cumulus Base

2198 feet

Today Highs / Lows

High Temperature

Low Temperature

18.6°F at 12:00 AM

13.6°F at 07:42 AM

High Humidity

Low Humidity

67% at 05:12 AM

61% at 12:00 AM

High Dewpoint

Low Dewpoint

7.8°F at 01:23 AM

4.7°F at 07:42 AM

High Barometer

Low Barometer

30.131 inHg at 07:57 AM

29.925 inHg at 12:00 AM

High Wind Gust

19 mph from 360° at 02:13 AM

High Rain Rate

0.00 in/hr at 12:00 AM

Low Wind Chill

-2.0°F at 07:58 AM

High Heat Index

18.6°F at 12:00 AM

Yesterday's Statistics

High Temperature

Low Temperature

41.3°F at 01:04 PM

17.6°F at 01:37 AM

High Humidity

Low Humidity

92% at 08:02 AM

55% at 06:14 PM

High Dewpoint

Low Dewpoint

30.9°F at 11:31 AM

7.4°F at 11:58 PM

High Barometer

Low Barometer

29.933 inHg at 11:46 PM

29.589 inHg at 12:26 PM

High Wind Gust

23 mph from 305° at 02:22 PM

Rain

0.39 in

High Rain Rate

0.21 in/hr at 12:09 PM

Low Wind Chill

3.4°F at 11:12 PM

High Heat Index

41.3°F at 01:04 PM

000
FXUS61 KBOX 201147
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
647 AM EST Mon Jan 20 2020

.SYNOPSIS...
Dry, but cold weather is on tap for today and Tuesday as high
pressure slowly builds in from the west.  Temperatures will begin to
moderate Wednesday and especially by Thursday/Friday, but dry
weather will persist.  There is the potential for a coastal storm
this weekend, but uncertainty exists in regards to timing and
precipitation types.

&&

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

645 AM Update...

Overall...previous forecast remains on track.  Strong cold
advection has allowed early morning temps to tumble well down
into the teens early this morning. Skies were mainly clear,
except for some scattered light ocean effect snow
showers/flurries across Cape Cod. This activity should continue
into the early afternoon, but any accumulations will just be a
coating to less than an inch.

Cold and dry air mass advecting in on NW flow related to the
passage of the compact trough, with 925 mb temps -11 to -13C
progged across Southern New England today. After a very cold
start early this morning, there will not be too much of a
recovery. Highs should top out in the lower to middle 20s in the
high terrain to the upper 20s to near 30 elsewhere. Despite the
cold advection, mixing heights are progged to be pretty low.
Still expect NW gusts of 20-25 with a few gusts around 30 mph.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...

Tonight through Tuesday:

Surface ridge, extending E from a strong 1044 mb high pressure area
centered over the Northern U.S. Plains, will remain across much of
New England through the short-term forecast period. High pressure
weakens/modifies as it moves southeastward towards the central
Appalachians by late Tuesday. Cyclonic flow aloft is maintained
through the period as well, with some reinforcement of the trough
aloft being delivered by a shortwave disturbance which moves quickly
southeastward into northern NH through ME late tonight into Tuesday.

All told, this looks to be a continued chilly but also a fairly
tranquil stretch of weather. Plenty of sun during the day, and
clear/calm conditions at night supporting near optimal
radiational cooling and cold low temps. Lingering NW winds
around 10-15 mph early tonight will continue to lighten and
eventually become light and variable into Tuesday.

Temperatures will be below-average compared to typical late-January
climatology. Under good radiational cooling, low temperatures in the
single digits across north-central and northwest MA under a
light snowpack, with lower teens otherwise common in the
interior into the coastal plain. Lows on the Cape and the
Islands into the upper teens to low 20s. Highs Tuesday under
plentiful sun then rebound back into the 20s.

&&

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

Highlights...

* Moderating temps begin Wed with above normal temps Thu/Fri along
  with continued dry weather

* Potential coastal storm this weekend would favor more rain than
  snow along the I-95 corridor but uncertain across the interior

Details...

Wednesday through Friday...

Large high pressure will remain in control Wed/Thu and Fri.  This
will maintain dry/tranquil weather, but temperatures will moderate
as some upper level ridging builds into southern New England.  High
temps should recover well into the 30s Wed and then into the 40s by
Thu/Fri.  Weak gradient may allow for sea breeze development, so
could be some cooling along the very immediate coast during the
afternoon.  Regardless, given light winds and above normal
temperatures it will feel rather comfortable outside during Thu and
Fri afternoons for late January standards.

This Weekend...

The long range guidance/ensembles continue to indicate the potential
for a coastal storm to impact southern New England sometime this
weekend.  Given this is still 5 to 6 days in the future, uncertainty
exists on potential timing, ptype, and amounts.  The one thing we
can say is that the antecedent airmass ahead of this potential storm
will be relatively mild for January standards. This is a result of a
deep Alaskan trough allowing for modified Pacific air across our
region. That being said, there does appear to be a surface high
pressure located across eastern Canada.  Depending on its exact
positioning and track of the potential coastal storm, just enough
cold air may result in the threat for snow/ice across parts of the
interior. While snow can not be ruled out along the coastal plain
too, rain would be favored unless the low pressure system would be
ideal for winter weather.

So in a nutshell, this potential storm is still 5 to 6 days in the
future and not a guarantee the we are impacted.  There is some
blocking to the north, so this does have the potential to be a slow
moving coastal storm.  Ptype would favor more rain than snow along
the coastal plain, but greater uncertainty further back into the
interior.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

09Z TAF Update:

Today: High confidence.

VFR except for some MVFR conditions on the Cape/Nantucket in
some lower clouds and scattered light ocean effect snow showers
this morning into early afternoon. NW wind gusts of 20 to 25
knots.

Tonight: High confidence.

VFR. NW winds 8-10 kt early becoming 5-8 kt in the interior. NW
winds stay around 10 kt through the overnight.

Tuesday: High confidence.

VFR. NW winds become light/variable late.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...

VFR.

&&

.MARINE...
SCAs in effect for all waters into the afternoon. Seas over 5
ft will continue on the outer waters through late tonight/early
Tuesday AM.

Today: NW winds 15-20 kt with gusts 25-30 kt early, then subsiding
to 20-25 kt gusts late today, higher on outer waters. Seas 4-8
ft, highest on the outer eastern/southeast waters, around 1-2 ft
nearshore. Few snow showers reducing visibility to around 4-6
mi near/east of Cape Cod. Light freezing spray.

Tonight: NW winds 10-15 kt gusts 15-25 kt early, then subsiding to
20 kt gusts by overnight. Seas 4-6 ft. Good visibility.

Tuesday: NW winds around 10 kt decrease to light NW. Seas decrease
to 2-4 ft on offshore waters, around a foot nearshore. Good
visibility.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday Night: Winds less than 25 kt.

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

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.

Friday: Winds less than 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for
     ANZ230>235-237.
     Small Craft Advisory until 6 AM EST Tuesday for ANZ250-254-255.
     Small Craft Advisory until 1 AM EST Tuesday for ANZ251.
     Small Craft Advisory until 7 PM EST this evening for ANZ256.

&&

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

NWS BOX Office Area Forecast Discussion