NWS Boston/Norton, MA wrote its last area forecast discussion before the first event at Nov 3, 12:23 PM EST, 2 hours 37 minutes earlier.
Area forecast discussion, Nov 3, 12:23 PM EST, 2 hours 37 minutes before
Area Forecast Discussion
National Weather Service Boston/Norton MA
123 PM EDT Sat Nov 3 2018
.SYNOPSIS...
Low pressure over New Jersey at predawn will intensify rapidly
and move through New England today bringing periods of heavy
rain this morning followed by dry weather this afternoon but
accompanied by a period of strong to damaging winds. High
pressure Sunday provides dry cool weather along with light
winds to close out the weekend. Wet weather may return early
next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
10am update...
Low pres continues to deepen and should be dropping 1000mb in
the next hour or so as it moves along the spine of the Green
Mountains then begins to shift more NE. Drier air already
intruding at the lower levels with the last banded rainfall
moving across E MA/RI. The comma-head rainfall should remain
generally to the W given the trajectory of the low pres itself
so not anticipating needed to raise POPs due to this.
Otherwise, forecast is on track for rain to end soon and winds
to become the dominant issue through the afternoon, early AM
mesoscale guidance does not show a need to make adjustments to
headlines as they stand. The only change will be to drop the
Flash Flood Watch as rivers of concern are already covered by
ongoing warnings or have crested with little additional rainfall
expected.
Previous forecast below...
Heavy Rain/Flood Threat...
Negative tilt trough in the Mid Atlc states capturing a
tropical plume of moisture (PWATs up to 1.8 inches) up the
eastern seaboard into southern New England this morning,
resulting in periods of heavy rain. Received a rainfall report
of 3.62 inches from Turner Falls in western MA. In addition the
North Branch of the Park River in Hartford county was
approaching flood stage. This combined with periods of heavy
rain continuing until 6 am to 10 am from southwest to northeast,
decided to issue a flood watch to communicate the risk of
flooding this morning. Heaviest rain will be across northern CT
into northern MA. Model consensus including Hi Res guidance is
for storm total rainfall of 1-3 inches with isolated amounts up
to 4 inches, highest totals across western-central MA. By mid to
late morning rain ends with dry weather this afternoon.
Severe Weather Threat...
Impressive warm sector for this time of year over southern New
England this morning with dew pts in the low to mid 60s and
temps in the mid to upper 60s! Specifically at 4 am it's 68 at
Norwood! Frontal boundary has just cleared Boston with a wind
shift to the NW. Thus any chance for a strong thunderstorm
would be in the warm sector across eastern CT/RI into southeast
MA. Low level jet enhancing low level helocity in this area.
Convection south of New England beginning to intensify as strong
forcing for ascent moves over this region with mid level trough
taking on a negative tilt combined with 170 kt RRQ of upper
level jet streak. Specifically will have to watch line segments
beginning to form over central Long Island and the adjacent
ocean waters as it tracks northeast into the warm sector over RI
and southeast MA especially near frontal boundary where low
risk for rotating storms. Low risk is valid until about 13z-14z
then cold front sweeps across the region.
Strong to Damaging winds...
As negative tilt trough sweeps northeast frontal wave deepens
rapidly from about 1000 mb near NYC at 09z to 983 mb low over
Maine late today. This will be accompanied by a strong pressure
rise-fall couplet that will enhance the isallobaric wind
component. In addition strong CAA on the backside of the low
will steep low level lapse rates and aid momentum wind transfer
from aloft. These two mechanisms will support wind gusts up to
60 mph which is supported by both NAM and GFS bukfit soundings.
Two areas of strong wind, 1) over Cape Cod and Islands with
steeper low level lapse rates due to relatively warm ocean
waters helping wind transfer from aloft and 2) over northeast MA
from the Worcester Hills into the Greater Boston area. As low
intensifies from south to north wind field increases, thus
stronger winds northward from northeast MA into ME. Therefore
will keep current configuration of headlines unchanged with High
Wind Warnings Cape Cod, Islands and northeast MA from Worcester
Hills to Greater Boston area. Greatest risk for tree damage and
isolated power outages will exist in the High Wind Warning area.
Temperatures...
Very mild this morning across eastern CT-RI into southeast MA
with temps well into the 60s. Elsewhere cooler with temps in the
50s as frontal boundary continues to sag south. All areas fall
into the 40s this afternoon as strong cold front sweeps across
the area. Very strong west winds this afternoon will add to the
developing chilly conditions.
&&
.SHORT TERM /SUNDAY/...
4 AM update...
Tonight...
Dry weather in the wake of departing low. Strong WNW winds in
the evening diminish overnight as high pressure builds in from
the west. Seasonably cool with lows in the 30s.
Sunday...
Definitely the pick of the weekend with 1032 mb high advecting
over New England. Given subsidence inversion blyr mixing will be
limited. 925 mb temps around +2C, which will support highs in
the lower 50s except upper 40s in the high terrain. About 5 degs
cooler than normal. However it will feel quite pleasant given
abundant sunshine and light winds.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
*/ Highlights...
- Widespread rain, embedded heavier showers for Monday
- Dreary, cool, drizzly conditions Tuesday
- Sharp sweeping cold front Wednesday with rain, heavy showers
- Cooler, drier pattern shaping up late week into weekend
*/ Overview...
Northeast sweeping lows. Pacific punch into the W CONUS as preferred
NW Pacific H5 troughing maintains, broader CONUS troughing prevails
through which Pacific-origin impulses obtain cyclogenesis to the lee
of the Rockies, cyclonically lifting NE up against a NW Atlantic H5
ridge. With greater pattern amplitude, opportunities emerge where
polar energy shears S rearward of broader cyclonic CONUS flow. A
series of NE sweeping lows in vicinity of New England, attendant
frontal boundaries, exchanging airmasses, chances of wet weather.
Seemingly typical Autumn weather through the early-half of November
with near-neutral teleconnections, relatively progressive mid-level
pattern, cold air mostly locked up N with subtle dips S at times.
*/ Discussion...
Monday ... Incipient low along the stalled frontal boundary draped
over the SE CONUS lifts N. Increasing isentropic lift beneath ascent
ahead of parent weak mid-level vortmax energy and H3 RRQ jet streak.
Decent precipitable waters, a bit of elevated instability, thinking
widespread rain with embedded heavier showers given some convective
indices at or slightly above thresholds. This within a cooler air-
mass as E/NE flow prevails, isallobarically driven by earlier high
pressure now NE up against the low approaching from the SW.
Tuesday ... Abundance of moisture as the surface low passes S/E. A
surface boundary remains kinked round New England along which we'll
see abundant moisture. Element of lift, expect low clouds, drizzle
to linger, cooler conditions prevailing with continued E/NE onshore
flow.
Wednesday ... Stronger, inside-runner low over the Great Lakes. Will
see flow revert S right before a sweeping cold front. Forecast model
timing discrepancies however consistent signal of a sharp cold front
yielding lift beneath favorable dynamics. Looking at a line of wide-
spread rain with embedded heavier showers, maybe a rumble of thunder
if instability is able to nudge far N. Likely will contend with some
of the S flow being breezy, especially along the S-coast. Clearing
out late within the dry slow, colder air held well back N/W.
Thursday onward ... Inside runner low lifting out as an area of N
Pacific low pressure continues, will see colder, Arctic air become
sheared S along with high pressure into S/SE Canada. Some snow cover
over Canada, however likely the airmass will moderate as it sweeps
along the US / Canada border. Cold, dry conditions following a re-
enforcing cold front and maybe some showers come Saturday.
Prior to, a pretty average Autumn pattern, but may have to watch
energy that ejects along the stalled frontal boundary offshore,
whether any weak areas of low pressure can develop and be
pulled back NW beneath the continued broader H5 troughing aloft.
&&
.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Sunday/...High confidence.
Through 20Z...
Cold front sweeps through, it has already passed Worcester and
will continue E over the next couple of hours. Winds shift
rapidly to the W. With this shift, expect increasing winds with
20-30 kt sustained and occasional gusts 50kt possible,
especially across NE MA and the Cape/Islands. Lingering MVFR
conditions rapidly become VFR with this shift as well.
After 20Z into Tonight...
VFR. Winds continue through about 03Z...then rapidly decline
into the morning hours.
Sunday...
VFR, dry and light winds.
KBOS Terminal...High confidence.
Remnant IFR should only last about an hour or two beyond the 18Z
TAF update. Then expect VFR after. Winds rapidly shifting to
the W and with it 20-30 kt sustained and gusts to 50 kt possible
through about 00Z, then diminishing gradually thereafter.
KBDL Terminal...High confidence.
Mainly VFR from now on. Winds peak out of the W this afternoon
with gusts to 45 kt, diminishing gradually after sunset.
Outlook /Sunday Night through Wednesday/...
Sunday Night: VFR. Slight chance SHRA, slight chance FZRA.
Monday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, slight chance FZRA.
Monday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.
Tuesday: Mainly VFR, with areas IFR possible. Breezy. Chance
SHRA.
Tuesday Night: Mainly VFR, with local IFR possible. Windy with
local gusts to 30 kt. SHRA likely.
Wednesday: VFR. Windy with local gusts to 30 kt. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
*** Storm Warning Saturday afternoon/early evening ***
Short Term /through Sunday/...Moderate to high confidence.
Today...low pressure near NYC intensifies rapidly today and
tracks through New England, delivering storm force west winds
this afternoon. Rain and fog yield poor vsby this morning but
improving with the wind shift mid to late morning.
Tonight...West Gales this evening diminish overnight as high
pressure builds in from the west. Dry weather and good vsby.
Sunday...very tranquil as 1032 mb high advects into New England.
Outlook /Sunday Night through Wednesday/...
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers.
Monday Night through Tuesday: Winds less than 25 kt. Local
rough seas. Chance of rain showers.
Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Local rough seas. Rain showers likely,
isolated thunderstorms.
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Rain showers likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory until 7 PM EDT this evening for CTZ002>004.
MA...High Wind Warning until 7 PM EDT this evening for MAZ004>007-
012>016-022>024-026.
Wind Advisory until 7 PM EDT this evening for MAZ002-003-
008>011-017>021.
RI...High Wind Warning until 7 PM EDT this evening for RIZ008.
Wind Advisory until 7 PM EDT this evening for RIZ001>007.
MARINE...Storm Warning until 8 PM EDT this evening for ANZ231>235-237-
250-251-254>256.
Storm Warning until 7 PM EDT this evening for ANZ230.
Gale Warning until 10 PM EDT this evening for ANZ236.
&&
SYNOPSIS...Frank/Nocera
NEAR TERM...Nocera/Doody
SHORT TERM...Nocera
LONG TERM...Sipprell
AVIATION...Doody/Sipprell
MARINE...Nocera/Sipprell