BOX issues Area Forecast Discussion (AFD) at Feb 10, 3:40 PM EST149
FXUS61 KBOX 102040
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
340 PM EST Mon Feb 10 2025
.SYNOPSIS...
Dry and cold conditions through Tuesday with below normal
temperatures. Low pressure will track well south of New England
Tuesday night and may bring some light snow to the immediate
south coast and Islands followed by drying conditions Wednesday.
A stronger frontal system then affects Southern New England
Wednesday night through Thursday, with a variety of
precipitation types anticipated to impact the Thursday morning
commute. Drier weather returns for Friday into early on Saturday
before another strong frontal system brings another period of
mixed precipitation over the weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Diurnal strato-cu will gradually erode this evening leading to
mostly clear skies as high pres builds into the region from the
west. Diminishing wind and clearing skies will result in a
period of good radiational cooling conditions but high clouds
will be moving in overnight which could have some impact on low
temps. We blended the colder MOS guidance with NBM to derive
temps tonight, yielding lows in the teens except single numbers
across interior northern and western MA.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday...
The high pres slides offshore with mid-high level moisture
streaming into SNE from the SW. High clouds will gradually
lower and thicken during the day with any sunshine fading
behind increasing clouds. Temps will remain below normal with
highs mostly 30-35, but upper 20s across interior MA high
terrain. Increasing SW flow ahead of a northern stream
shortwave will result in 10-20 mph winds developing per
forecast soundings.
Tuesday night...
Flat wave tracks ENE off the NC coast and passes well south of
the benchmark. Bulk of snowfall from this system will remain to
the south. However northern extent of deep moisture may move up
along the south coast. The forecast challenge is how far north
will snow shield extend. 3km NAM is most aggressive with around
0.25" QPF over the Islands but very sharp gradient on the
northern edge. Rest of hi- res guidance sources are further
south with heavier QPF and keep most of the snow to the south.
EPS and GEFS ensembles also show just moderate probs of 0.10"
QPF grazing the Islands with higher PoPs to the south. So we are
leaning toward light accums, around an inch or 2 for the
Islands and just a coating to less than an inch for the south
coast and Cape Cod. However, given the sharp gradient on the
northern edge, any shift to the south would result in little to
no snow for the south coast and less than an inch for the
Islands. A further northward trend would result in a bit more
snow. Either way, this is not expected to have much impact as
snow will be developing after 9-10 pm with only minor accums and
mostly done before daybreak.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Messages:
* Frontal system Wed night into Thurs brings a wintry mix of snow,
icing and eventually rain, with adverse impact to the Thurs AM
commute. Although accumulations are still uncertain, winter
weather headlines seem likely to be needed.
* Quiet Friday, but colder temps settle in over the area.
* A low-pressure system approaches Saturday, likely bringing another
round of wintry precip to southern New England.
Details:
Wednesday and Thursday:
High pressure early Wed then slowly retreats NE as a rather potent
500 mb shortwave embedded in fast SW flow aloft moves through the Gt
Lakes region Wed night and into northern New England into Thurs. The
progged strength of this wave and the associated mass response
downstream (e.g. height rises) ahead of it supports stronger influx
of warmer air intruding in aloft on lower level southerly flow,
suggesting a variety of p-type changes and wintry mix scenario in
play specific to this storm. This lends itself to uncertainties
regarding snow/ice amts and precip type timing/changeovers. With
adverse impacts from wintry weather looking likely to impact
travelers late Wed night and into Thurs, especially the Thurs AM
commute, it has the look of an winter wx advisory type event for
most of interior Southern New England.
Antecedent airmass when precip comes in, around mid to late Wed
night, is plenty cold enough to support a period of steadier-
accumulating light to moderate wet/dense snow at onset. It is
possible we could get some "thump" of heavier embedded snowbands in
response to warm advection/frontogenesis effects, but where and when
this takes place is still unclear. Eventually warmer air wins out
and facilities a transition from snow to ice pellets/freezing rain
from south to north overnight into Thurs. As the column graudally
warms aloft, sustained/prolonged onshore flow near the E MA
coastline may allow for an earlier p-type transition than further
inland. Although temps in most areas warm above freezing enough to
flip any wintry mix over to rain, there are several global ensemble
members which show at least some bagginess to isobars/possible
secondary low pressure development near or just east of Southern New
England. If this were to develop, this could help to maintain or
draw down colder near/sub-freezing temps from NH/ME and keep wintry
p-types in for a longer period of time, especially in northern and
northeast MA. We then dry out by Thurs afternoon with not much if
any impact to the Thurs PM commute.
Thursday Night through Monday:
Decent ridging ahead of a quick moving high will allow for rather
chilly temps Thursday night and Friday, with overnight lows in the
mid-teens, and a brief respite from the rain and snow.
Another shortwave moves east off the Rockies Saturday, bringing a
surface low through New England on Sunday. Model guidance on the
track of the system is still very uncertain. The GFS is favoring a
faster, more southerly track, while the ECMWF and GEM are indicating
the system may stall out over eastern Ohio/western Pennsylvania
sometime Sunday morning. Regardless, the embeded upper-level
WAA combined with colder surface temps will likely pose several
p-typing issues for the weekend.
&&
.AVIATION /21Z MONDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Tuesday...High confidence.
VFR through the period. BKN cigs around 5k ft this afternoon
will erode this evening. Increasing high clouds Tue. WNW gusts
to 20 kt this afternoon becoming light tonight, then SW 10-20 kt
Tue.
Tuesday night...Moderate confidence.
Uncertainty with northern extent of snow area as it approaches
the south coast. Best chance for a period of snow with IFR vsbys
and minor accum will be over the Islands with lower probability
along the south coast. VFR north of HFD-PVD-PYM.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Wednesday through Saturday/...
Wednesday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SN.
Wednesday Night: Mainly IFR, with areas MVFR possible. Breezy.
Chance SN, PL, FZRA, patchy BR.
Thursday: Mainly IFR, with local MVFR possible. Breezy. FZRA,
PL, chance RA, patchy FG.
Thursday Night through Friday: VFR. Windy with gusts up to
30 kt.
Friday Night: VFR. Breezy.
Saturday: Mainly VFR, with local IFR possible. Chance SN.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Gusty NW winds to 20-25 kt eastern MA waters will diminish
tonight, then shift to SW 10-20 kt during Tue. Winds will then
become N-NE 10- 20 kt late Tue night as front slides south of
the region. SCA for eastern MA waters into this evening for
winds and seas.
Outlook /Wednesday through Saturday/...
Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of snow.
Wednesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft. Rain, sleet, chance of
snow, freezing rain, patchy fog. Areas of visibility 1 to 3 nm.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 10 ft. Rain, freezing rain, patchy
fog.
Thursday Night through Friday: Strong winds with gusts up to
30 kt. Rough seas up to 9 ft.
Friday Night: Winds less than 25 kt. Local rough seas.
Saturday: Winds less than 25 kt. Chance of snow, chance of
rain.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 AM EST Tuesday for ANZ250-254.
Small Craft Advisory until 9 PM EST this evening for ANZ251.
&&
$$
SYNOPSIS...KJC/Loconto/McMinn
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...Loconto/McMinn
AVIATION...KJC/Loconto/McMinn
MARINE...KJC/Loconto/McMinn
Source:
BOX issues Area Forecast Discussion (AFD) at Feb 10, 3:40 PM EST----------------
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