NWS Forecaster Discussion
BOX
Area Forecast Discussion National Weather Service Boston/Norton MA.
000
FXUS61 KBOX 291749
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1249 PM EST Sun Jan 29 2023
.SYNOPSIS...
Above normal temperatures continue today, along with mainly dry
conditions, until this evening when scattered showers impact our
region. The weather turns colder over the course of next week, but
the magnitude of the cold and timing remains uncertain. We also will
have to watch for some wintry precipitation in the mid-to-late week
timeframe, depending upon a few waves of low pressure passing close
enough to our region.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1010 AM Update:
Other than some generally small adjustments to temps and sky
cover to match current observations and expected near term
trends, no significant change needed with this forecast refresh.
While Cape Cod and SE MA currently seeing mostly clear skies,
move further westward and considerably more cloudiness (of the
mid-level type) fill the scene in broader warm sector ahead of a
surface low analyzed over the eastern Gt Lakes region. Expect
continued quite mild late-January conditions with temperatures
resembling typical values for late-March than late-January for
most. Won`t be as pleasant a day as yesterday was though, as
this mid- level cloudiness spreads eastward into the aftn, along
with an increase in S/SSW winds to around 10 to 15 mph (gusts
to 25 mph for Cape Cod and part of southeast MA/coastal southern
RI). As cloud ceilings lower late-afternoon into tonight, some
models generate some rain showers especially eastern and
southeastern New England; while dewpoints do rise, apparent in
model soundings that dry air above 925 mb still not likely to
saturate fully. Thinking mostly dry but left PoP unchanged for
now; were showers to develop they would be on the light side and
not impactful in any meaningful way.
Previous discussion:
An area of low-pressure track northeast across western NY will
drag an anomalously warm air mass over southern New England this
afternoon. Low-level southerly flow will advect nearly 5
Celsius temps at 925 hPa over the region. This will translate to
temps in the low to mid 50s across much of southern New England
today. Southerly flow will be accompanied by moisture advection
as well. Thus, expect mostly cloudy skies on this very mild
day. In addition to the warmth, a tight pressure gradient will
support 20 to 25 mph wind gusts this afternoon. Most of the area
will stay dry today, but a stray shower is possible across the
interior during the mid- afternoon hours when deeper moisture is
expected to push into the region from the west. Slightly higher
rain chances late afternoon/early evening will reside over The
Cape and Islands where PWATs are expected to rise to 0.75
inches. Accumulations will be limited to only a few hundredths
as deep-layer moisture and synoptic forcing for ascent will be
lacking.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight
Any remaining showers over The Cape/Islands taper off before
Midnight. Pressure gradient relaxes overnight as an area of low-
pressure continues to eject northeast over Nova Scotia. This will
allow the gusty southwest winds from this afternoon to diminish
while turning westerly in the process. Overcast skies persist
overnight, thus expect above normal low temperatures in the mid to
upper 30s across the southeastern half of the region. Further to the
north and west, temps will bottom out near freezing.
Tomorrow
Southwest flow settles back in on Monday ahead of a weak surface
cold front. Low-level WAA will allow a milder air mass to settle
over the region once more. Thus, we may be looking at another
afternoon with highs topping out in the 50s. However, upper 40s will
be more likely as 925 hPa temps are expected to be roughly 5 degrees
cooler than what is expected today. Some light showers will be
possible late afternoon/early evening as the surface front pushes
through the region. Once again, moisture and forcing will be
limited, so any showers that develop would produce minimal rainfall
accumulations.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights...
* Mostly dry this week with periodic shots of light precipitation
* Potential for much colder air toward the end of the week, but
details are uncertain.
Details...
Overall, expecting a generally zonal and confluent mid level flow
for the coming work week. Southern New England will be positioned
between an upper level ridge over the Caribbean and a trough over
eastern Canada. 29/00Z guidance has come into better agreement
regarding the favored storm track, which now looks to be too far to
our south to bring significant precipitation to most of southern New
England during this portion of the forecast. Will still need to
monitor portions of RI and eastern MA as an offshore low pressures
pass by towards both Tuesday Night/Wednesday, and again Friday
Night/Saturday. Even for these areas, the trend in overall
precipitation chances has been decreasing.
Temperature-wise, the forecast challenge remained consistent. Both
deterministic and ensemble guidance signaled near to below normal
temperatures for most of this portion of the forecast. Still have
questions about how much below normal we will get towards next
weekend, and how long will those condition linger. Ensemble guidance
has come into better temperature agreement through Thursday, with
the 80 percent confidence interval down to 10 degrees or less. That
interval increases to around 20 degrees by Friday, and to around 30
degrees by Saturday. With a high pressure expected over Ontario,
thinking a colder scenario is becoming more likely. Given the
uncertainty, stuck more closely to the NBM values, since those are
an ensembled solution.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update:
Rest of the Afternoon (thru 00z Mon): High confidence.
Mainly VFR ceilings thru the day; however lower-VFR/MVFR
ceilings possible late-day in NW MA and the terrain but away
from TAF sites. Still generally dry weather but an outside shot
at unrestricted -SHRA around ~20-00z especially east of ORH;
runways dry. S winds become SW around 10-13 kt this afternoon.
Occasional low-20s kt range for gusts across Cape and Islands.
Tonight: High confidence.
VFR ceilings, with lower-prob MVFR ceilings across northwest
MA. Mainly dry but a spot light shower possible thru 03z SE
MA/Cape Cod. SW winds around 10-13 kt (occasional 20 kt gusts
Cape Cod and Islands airports), veering to west after 05z and
diminish to 5-10 kt.
Monday: High confidence.
Mainly VFR, lowest ceilings around 035-040 west of ORH. Spotty
light rain after 20z but runways dry. W winds 4-8 kt, becoming
S late- day.
Monday Night: High confidence.
OVC lower VFR ceilings with MVFR ceilings for the south coast,
cape and islands. SW winds become WNW and increase to 10-15 kt,
with gusts around 20-25 kt.
KBOS Terminal...High confidence in TAF. Occasional 20 kt gusts
from the S but thinking more sustained winds. Outside shot at a
sprinkle, runways dry.
KBDL Terminal...High confidence in TAF.
Outlook /Monday Night through Thursday/...
Monday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance RA.
Tuesday through Tuesday Night: VFR. Breezy.
Wednesday: VFR.
Wednesday Night through Thursday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today...high confidence.
Light south winds early becoming SSW 15-25 kt in the afternoon. Dry
weather and good vsby, although low risk of scattered showers late
in the day.
Tonight...high confidence.
SSW winds in the evening of 15-25 kt, becoming west 10-15 kt
overnight. Scattered evening showers, trending dry overnight.
Tomorrow...high confidence.
Light SSW winds. Good visibility. Low risk for scattered showers mid-
late afternoon.
Outlook /Monday Night through Thursday/...
Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of snow.
Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of snow.
Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft.
Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 5 AM EST Monday for ANZ250.
Small Craft Advisory until 7 AM EST Monday for ANZ254>256.
&&
$$
SYNOPSIS...Belk/RM
NEAR TERM...Belk/Loconto/RM
SHORT TERM...RM
LONG TERM...Belk
AVIATION...Loconto/KS
MARINE...Belk/Loconto/RM