NWS Forecaster Discussion
BOX
Area Forecast Discussion National Weather Service Boston/Norton MA.
000
FXUS61 KBOX 191528
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1028 AM EST Sun Jan 19 2020
.SYNOPSIS...
Secondary area of low pressure in the Gulf of Maine will
continue to pull away from New England today. High pressure
building in from the west will result in dry, but cold weather
tonight into Wednesday morning. This high will push south of the
region by Thursday and Friday with continued dry conditions,
but bringing above normal temperatures. We will then need to
watch a potential coastal storm which may impact the region
sometime next weekend.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Temperatures remain a concern this morning. Colder air was
holding in a bit longer. Expecting temperatures to rise more
quickly once an inversion is broken now that sunshine was more
prevalent. Made minor tweaks to temperatures into this afternoon
to reflect observed trends.
Will still need to contend with some clouds across the western
half of southern New England through this afternoon.
645 AM Update...
Otherwise, intensifying low pressure was lifting northeast into
the Canadian Maritimes. This will quickly mix out our remaining
low level cold inversion, so untreated icy roads will quickly
improve this morning. Partial sunshine will result in high
temperatures reaching the lower to middle 40s in many locations.
It will become blustery with 25 to 30 mph wind gusts developing
and perhaps a few gusts near 35 mph this afternoon. Dry weather
should pretty much prevail, but can not rule out a spot
rain/snow shower as a cold front approaches especially along the
east slopes of the Berkshires.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight:
Main story for tonight is the return of much colder air that
filters in on NW flow (850 mb temps plummet to the negative
teens Celsius), along with continued northwest winds. Sided a
little bit warmer on the lows with the idea that the winds will
keep temperatures from falling really sharply even though we`re
otherwise in a good radiational cooling setup. Showed range of
lows low- teens to the mid 20s. Wind chills in the single digits
below zero to the single digits above.
One feature that we will have to watch for overnight is a
secondary 500 mb trough rippling through the longwave cyclonic
flow. Model guidance continues to show some interaction with an
inverted trough associated with the distant secondary low
pressure in the Maritimes to foster a period of snow showers
across parts of Cape Cod and Nantucket. QPF isn`t substantial -
a few hundredths at most - but cold profiles and ocean-effect
instability could produce an inch or so of new snow late
tonight of across a good part of the Cape and into Nantucket.
Monday:
Continued quite chilly with the low-level thermal trough
overhead and blustery NW winds still prevailing, though speeds
and gusts should be less than today. Ocean-effect snow showers
may continue to brush the Cape through midday, though the threat
should be ending by afternoon as the inverted trough pulls away.
Full sun but heating offset by weakening cold advection supports
highs only the upper teens to the mid/upper 20s. Wind chills by
daybreak still at or below zero in NW MA but expected to warm
gradually in lockstep with slowly warming temps.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights...
* Dry and cold Mon night and Tue
* Temps moderate Wed and esp Thu/Fri with dry weather persisting
* Coastal storm possible next weekend with rain favored, but can not
rule out some snow/ice especially across the interior
Details...
Monday night and Tuesday...
Upper trough over the northeast will keep temperatures cold, but a
ridge of high pressure at the surface will result in dry weather.
Lows Mon night will bottom out in the teens with some single digits
possible across portions of western/central MA. Highs on Tuesday
will only be in the upper 20s to near 30 in most locations.
Wednesday...
After a cold start early Wednesday morning, temperatures will begin
to moderate. This in response to the upper level trough pulling
away from the region, allowing for rising height fields to commence.
This should be enough to allow afternoon highs to reach well into
the 30s in many locations. High pressure overhead will result in
rather light winds and plenty of sunshine too.
Thursday and Friday...
Some upper level ridging builds into southern New England. This will
bring a return to above normal temperatures Thu and Fri. A ridge of
high pressure at the surface will also keep our weather dry. High
should reach well into the 40s in many locations. It also is not out
of the question that a few locales break 50 by Fri.
Next Weekend...
There are signs in the long range guidance/ensembles of a potential
coastal storm. Timing/track of course is uncertain in this time
range, but if it comes to fruition might end up being slow moving
with some blocking to the north. As for ptype, still uncertain
given this is a day 6-7 forecast. That being said, cold air will be
lacking across much of the country given deep trough over Alaska.
This would favor rain at least along the coastal plain. However,
there is high pressure system across eastern Canada. Depending on
its position/strength, this may provide just enough cold air for
some snow/ice with the best chance across the interior. Not much
more to say at this point, but will have to see how things trend
over the next few days.
&&
.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Today: High confidence. Predominantly VFR through this afternoon
Local MVFR in fog in the CT River valley possible through noon.
Could also see some local MVFR cigs across the higher terrain
of western MA. WNW wind gusts of 25 knots should develop by
afternoon.
Tonight: High confidence.
VFR. Low prob MVFR ceilings and visibility across the outer
Cape and Nantucket, mainly after 20/05Z. NW winds decreasing to
10 kt (gusts 18-20 kt) in the interior, with 10-15 kt gusts to
20-25 kt on the Cape and Nantucket.
Monday: High confidence.
VFR. NW winds 6-10 kt in the interior, 10-12 kt with early gusts
to 20-25 kt out on the Cape.
KBOS Terminal...High confidence.
KBDL Terminal...High confidence.
Outlook /Monday Night through Thursday/...
Monday Night: VFR. Breezy.
Tuesday through Thursday: VFR.
&&
.MARINE...
SCAs continue on all waters with NW winds increasing by this
morning and colder air moves over the waters. Winds and seas may
still support continued SCA conditions on most offshore waters
through Monday morning. Potential for the SCAs to need to be
extended further into Monday but wasn`t confident on this as yet
to consider that extension.
Light freezing spray will be possible tonight with the colder
air across the waters. Into late tonight and Monday, snow
showers may affect Cape Cod Bay, Nantucket Sound and the waters
east of Cape Cod.
Outlook /Monday Night through Thursday/...
Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Local visibility 1 to 3 nm.
Tuesday Night through Thursday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ231>235-237-
250-251-254>256.
Small Craft Advisory until midnight EST tonight for ANZ230-236.
&&
$$
SYNOPSIS...Frank/Loconto
NEAR TERM...Belk/Frank
SHORT TERM...Loconto
LONG TERM...Frank
AVIATION...Belk/Frank/Loconto
MARINE...Frank/Loconto