Scientific Forecaster Discussion
fxus61 kbox 112042
Area forecast discussion
National Weather Service Boston/Norton Massachusetts
342 PM EST Mon Nov 11 2019
a strong cold front will cross our region Tuesday with some
light rain or showers, which will likely end as a brief period
of snow along with rapidly falling temperatures. Record cold
along with windy conditions follow Tuesday night into Wednesday,
with wind chills dropping to between 5 below and 10 above zero.
Temperatures will remain well below normal Thursday, but with
much less wind. A brief moderation occurs by Friday, but
unseasonably cold weather returns by Saturday behind another
Near term /until 6 am Tuesday morning/...
deep upper trough digging over the western Great Lakes with
heights well below normal. This will turn the westerly upper
flow over US to come out of the southwest. This should stall the
southward progress of a cold front over our area and even push
it back to the north. Radar showed a few light showers over far
northern Massachusetts during the afternoon. This may continue into the
evening, but as the upper flow turns it is likely these showers
will shift north of our area.
Upper jet moving through this southwest flow will approach US
later tonight, generating an area of lift later tonight and
generating some showers at least and possibly a broader area of
rain. The best chance of wet weather will be in western Massachusetts and
adjacent CT, while southeast Massachusetts may escape the wet weather
during the night.
A 50-kt low level southwest jet will move over the waters and
may clip the South Coast areas. This would suggest gusts to 30
kt later tonight along our coastal areas including the cape and
Wide range of temperatures tonight, but all of them above
freezing. Northern Massachusetts temps in the 40s with dew points in the
30s...expect min temps in the north to reach the mid to upper
30s. Southern areas of Massachusetts-RI-CT reached the lower 60s with dew
points in the mid 40s to low 50s...expect min temps in the south
to reach the mid 40s to lower 50s.
Short term /6 am Tuesday morning through Tuesday night/...
overall... upper trough approaches from the Great Lakes Tuesday
and moves over New England Tuesday night. It will bring much
below normal 500-mb heights and temperatures.
Surface low pressure wave passes across New England during the
morning and midday. Operational model positions bring it either
across western Massachusetts or passing north of Massachusetts. That would place most
of Massachusetts in the warm sector and suggest precip as showers rather
than a steady rain. Precipitable water values top out around 1 inch, which is
above normal but not excessively so. So we expect rain/showers
during the morning and midday, ending as the low moves off to
the northeast and swings a cold front across our area. Cold air
moving in behind the cold front may arrive fast enough to
convert the last of the showers over to snow, but the expected
quantitative precipitation forecast for that part of the storm should be limited resulting in
amounts less than an inch in most places, but possibly 1-2
inches on the east slopes of the Berkshires.
Temperatures will show a non-diurnal pattern, with warmest temps
in the morning, then getting colder late morning west and
afternoon east as the cold front moves past. Morning highs will
be just a few degrees higher than the overnight lows, with
temperatures falling through the 30s and upper 20s in the west
and through the 40s and upper 30s in the east.
Cold advection will support mixing of strong wind gusts to the
surface with values of 25 to 35 kts/30 to 40 mph available for
The last of the rain/snow tapers off over Cape Cod and vcnty
early Tuesday night. Colder drier air advects in on northwest
winds during the night. Expect clearing skies from west to east
during this time with continued 30 to 40 mph wind gusts.
Temperatures will fall to the teens in most spots, which is at
or near record territory for min temps Wednesday morning.
Wind chills will be in the teens in the evening and single
numbers either side of zero late at night.
Long term /Wednesday through Monday/...
* windy with record cold possible Wed
* wind chills between 5 below and 10 above zero Wed morning
* still unseasonably chilly on Thu, but with much less wind
* briefly milder Fri, before turning much colder again by Sat
Expecting temperatures for this portion of the forecast to
remain below normal. For the case of Wednesday and Wednesday
night, make that well below normal. Continued with a forecast
for record minimum high temperatures Wednesday. Low
temperatures Wednesday night should approach the existing
records. Will need to monitor the timing and magnitude of the
colder air Wednesday night. Should radiational cooling
conditions be more ideal than currently thought, those records
could be challenged.
A little bit of a warming trend Thursday into Friday, but still
below normal. Another surge of colder air for Saturday,
followed by another slow warmup Sunday into Monday.
Dry weather will be in place Wednesday into Thursday as a high
pressure passes by southern New England. Will need to consider
more showers sometime Thursday afternoon into Friday morning
within the modest warm advection pattern. These showers would be
mainly towards southeastern Massachusetts and Rhode Island. Thinking most of these
showers will be in the form of rain, although some snow is
possible, depending upon timing.
High pressure nearby should mean another period of dry weather
Friday night into Sunday. Another low pressure may approach from
the south Sunday into Monday, providing an increasing risk for
some light precipitation Sunday afternoon into Monday. This
timing is not yet certain, and could even be slower. It is also
possible that high pressure holds on across northern New England
a bit longer, and steers this low pressure out to sea.
Aviation /21z Monday 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/...moderate confidence.
Tonight...VFR conditions early tonight, but lowering to MVFR-
IFR thresholds in most areas. Remaining VFR near the South
Coast. Winds become light/variable near and north of the Pike,
SW winds 10-15 kt near the S coast, Cape Cod and the islands.
Tuesday...MVFR-IFR ceilings/visibilities in rain/showers and patchy fog.
Winds shift from the west-northwest and increase to 15-25 kt
inland and 20-30 kt across south coastal terminals. This draws
cold air into southern New England during the afternoon, with
enough cold air to change rain to snow shortly before the
precipitation ends. Conditions should improve to VFR from west
to east during the afternoon and evening.
Tuesday night...lingering MVFR cigs/vsbys along Cape Cod and
islands early, but this will improve to VFR early in the night.
VFR the remainder of southern New England through the night.
West-northwest winds gusting 25-30 kt inland and near 35 kt at
Kbos terminal...moderate confidence in taf.
Kbdl terminal...moderate confidence in taf.
Outlook /Wednesday through Saturday/...
Wednesday: VFR. Windy with gusts up to 35 kt.
Wednesday night: VFR. Breezy.
Thursday: mainly VFR, with local MVFR possible.
Thursday night: mainly VFR, with local MVFR possible. Slight
chance rain showers or freezing rain.
Friday: VFR. Breezy.
Friday night through saturday: VFR. Windy with gusts up to
short term /through Tuesday night/...high confidence.
Winds will shift from the south and southwest and increase to
15-20 kt. Gusts to around 30 kt across the southern waters
around or after midnight. Winds east of Cape Ann may remain east-
southeast for a time but should shift from the southwest toward
morning. Seas will be less than 4 feet early at night, then
build to 5-8 feet on the exposed waters. Highest values should
be on the southern outer waters. Mainly good visibility.
Southwest winds shift out of the west-northwest midday as a
cold front sweeps across the waters. Expect afternoon winds
20-25 kt with gusts 35-40 kt. A Gale Warning is in effect for
all of the waters. Visibility restrictions in rain/showers/fog
especially in the afternoon. Seas will remain at 5 to 9 feet on
all exposed waters.
Cold front moves out to sea. Any precipitation should end and
skies will clear. However winds will continue at gale force
through the night. Seas will be 5 to 10 feet on all exposed
Outlook /Wednesday through Saturday/...
Wednesday: low risk for gale force winds with gusts up to
40 kt. Areas of rough seas.
Wednesday night: winds less than 25 kt. Areas of seas
approaching 5 ft.
Thursday: winds less than 25 kt.
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
35 kt. Areas of rough seas.
Saturday: low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 10 ft.
record low min temps for Wednesday Nov 13
Record low Max temps for Wednesday Nov 13
Record low min temps for Thursday Nov 14
Marine...Gale Warning from 1 PM Tuesday to 1 PM EST Wednesday for
Gale Warning from 3 PM Tuesday to 1 PM EST Wednesday for
Gale Warning from 10 am Tuesday to 1 PM EST Wednesday for