Scientific Forecaster Discussion
fxus61 kbox 131507
Area forecast discussion
National Weather Service Boston/Norton Massachusetts
1007 am EST Wed Nov 13 2019
high pressure building in from the west will become centered
over New England tonight. It will bring record cold temperatures
today, along with gusty winds this morning. As the high moves
off the coast, temperatures begin to moderate on Thursday, but
will still be below normal for the middle of November. Even
milder weather is forecast for Friday, but then another strong
cold front will deliver unseasonably cold temperatures Friday
night through Saturday night. An ocean storm may impact the
region Sunday night into Monday with rain and wind along the
coast and pockets of interior ice.
Near term /until 6 PM this evening/...
1005 am update...
Current forecast on track so no major changes. Winds gradually
diminish today, with record cold temperatures under sunny
Strong, large high pressure builds eastward into New England
today providing completely sunny skies. Despite the sunshine, we
are expecting record cold temperatures. Highs will be hard
pressed to break 32 in most areas and will likely remain in the
20s in northwestern Massachusetts. If so, this would break long-standing
records for the lowest maximum temperature for this date in
history. Boston's record low Max temperature of 36 degrees has
stood for 145 years...since 1874. Please see climate section
Northwest winds will be gusty this morning...up to 25-35 mph at
times, but the pressure gradient will slacken this afternoon and
winds will be correspondingly diminishing.
Short term /6 PM this evening through 6 PM Thursday/...
High pressure overhead will mean light wind and cold
temperatures. Skies will be clear before midnight, allowing for
good radiational cooling. But models show an increase in mid and
high level moisture overnight. Any mid cloudiness would probably
be enough to prevent temperatures from dropping into the single
digits. Am forecasting lows from 10 to 15 most areas, except
lower to mid 20s Outer Cape cod and Nantucket.
High pressure moves offshore, allowing a return flow of moist
southerly air. A low level jet of 25-30 kt develops by afternoon
across southern New England, increasing low level warm
advection. Highs are forecast to reach the mid and
upper 30s in the interior and 40s in Rhode Island and southeast Massachusetts.
Am believing the 3km NAM model which is the most emphatic at
developing a rapid influx of low cloudiness from south to north
during the late morning hours. It is very dry aloft, which
means that as we saturate the low levels, drizzle or very light
rain showers should develop in the afternoon, especially across
Rhode Island and southeast Massachusetts. The air may be initially cool enough in the
Merrimack valley and in Worcester County for light snow to be
mixed with any rain and drizzle. For now, have only introduced
chance pops of 30-35 percent for Thursday afternoon. Will have
to see how this trends.
Long term /Thursday night through Tuesday/...
* mainly dry with seasonable temps Fri
* turning much colder again Fri night into Sat night
* an ocean storm may impact southern New England Sun night/Mon with rain and coastal
wind along with pockets of ice possible in the interior
High pres moves to the east with warm advection pattern developing.
Low level moisture moves in by evening across southeast new eng and deepens
a bit overnight as modest low level jet develops. Models are hinting
at a weak inverted trough setting up across southeast new eng which may
bring a few showers during the night, mainly across Rhode Island and southeast Massachusetts.
Low temps will drop into the 20s in the interior, but mid/upper 30s
along the coast as southerly flow develops.
Friday into Saturday...
Robust northern stream shortwave dives southeast across northern new eng
which will deliver another strong cold front which drops S across
southern New England Fri night. Ahead of the front, expect dry conditions Fri with
seasonable temps, then turning much colder Fri night into Sat behind
the front as strong high pres builds to the north on Sat. Temps well
below normal although not quite as cold as current Arctic airmass.
Gusty north winds will result in wind chills in the single numbers and
teens late Fri night and Sat morning. Expect a mainly dry fropa Fri
night with mostly sunny skies Sat.
Sunday into Tuesday...
It appears dry weather will hang on through Sunday as high pres
keeps moisture to the south. However, ocean storm will be
approaching from the south and may impact the region Sun night into
Mon. Still lots of uncertainty with the track of the storm and how
close it gets to new eng with large spread among deterministic
guidance as well as European model (ecmwf) ensembles for track and quantitative precipitation forecast. Also,
uncertainty on a potential second storm approaching from the south
on Tue. Will continue chance pops as European model (ecmwf) ensembles show decent quantitative precipitation forecast
probs. Temps aloft are warming so rain will be favored, but high
pres to the north may provide enough low level cold air for some
interior ice Sun night/early Mon. It may also become windy along the
coast depending on how close storm tracks to new eng.
Aviation /15z Wednesday through Sunday/...
forecaster confidence levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short term /through Thursday/...high confidence.
Today...high confidence. VFR. Northwest gusts 20-30 kt this morning,
diminishing this afternoon.
Tonight... high confidence. VFR.
Thursday...moderate confidence. VFR early. Then MVFR ceilings
developing with areas of drizzle and light rain showers in the
afternoon, possibly mixed with snow in central and northeast Massachusetts.
Local IFR possible late in the day.
Kbos terminal...high confidence in taf.
Kbdl terminal...high confidence in taf.
Outlook /Thursday night through Sunday/...
Thursday night: VFR. Breezy. Slight chance rain showers.
Friday: VFR. Breezy.
Friday night through saturday: VFR. Windy with gusts up to
Saturday night: VFR. Windy with gusts up to 30 kt.
Sunday: mainly VFR, with areas MVFR possible. Windy with local
gusts up to 30 kt.
short term /through Thursday/...high confidence.
1005 am update...
Gale warnings were allowed to expire. Small craft advisories now
posted for all coastal waters. As high pressure builds in from
the west, the pressure gradient will weaken. Rough seas from
5 to 10 ft this morning over the outer waters will be subsiding
Tonight...seas of 5 feet linger on the outer waters this
evening, but will then be subsiding to 2 to 4 ft. North winds 10-20
kt become light NE.
Thursday...winds become S and increase to 15 to 20 kt in the
afternoon. Chance of showers in the afternoon.
Outlook /Thursday night through Sunday/...
Thursday night: winds less than 25 kt. Areas of seas
approaching 5 ft. Chance of rain showers.
Friday: low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
Friday night: low risk for gale force winds with gusts up to
40 kt. Areas of rough seas.
Saturday: moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 12 ft.
Saturday night: low risk for gale force winds with gusts up to
35 kt. Rough seas up to 10 ft.
Sunday: moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 10 ft. Slight chance of rain
record low min temps for Wednesday Nov 13
Providence 19/2019 - previously 20/2001
Worcester 13/2019 - previously 15/1986
Record low Max temps for Wednesday Nov 13
Record low min temps for Thursday Nov 14
Marine...Small Craft Advisory until 1 PM EST this afternoon for
Small Craft Advisory until 6 PM EST this evening for anz230-
Small Craft Advisory until midnight EST tonight for anz250-254-
Small Craft Advisory until 4 PM EST this afternoon for anz256.