Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 231824
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
124 PM EST Tue Jan 23 2018

.SYNOPSIS...

Heavy rain and isolated thunderstorms are the main story this
afternoon along with a period strong winds across portions of
southeast MA and RI. Rapidly improving conditions from west to
east early this evening. Blustery, dry and colder weather
follows Wednesday through Friday, then a warming trend next
weekend. A cold front may bring showers next Sunday or Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

120 pm update...

Although the surface warm front is still south of the MA
turnpike...latent heat release has allowed temps to rise to
between 32 and 34 degrees across north central and northeast MA.
We opted to extend the winter weather advisory through 3 pm for
lingering icy spots...but probably not much more ice accretion.
Improvement in time for the evening rush hour!

Otherwise...main story is the feed of heavy rain focused across
eastern MA and RI along with isolated thunderstorms. This is on
the nose of a potent 80+ knot low level jet coupled with some
elevated instability. Given Pwats/LLJ 3+ SD above normal...heavy
rain and isolated t-storms will continue to impact the region
through 21 or 22z. Activity should diminish after that time as
LLJ/forcing shifts east of the region...but still expect some
scattered showers. Main impacts with heavy rain will be brief
nuisance poor drainage street flooding. We may also see some pea
sized hail with any convection given cold temps aloft.

As for strong winds...temps rising through the 50s now south of
the Pike. Still an inversion in play...but any heavier
rain/convective elements may bring stronger winds to the ground.
Therefore...wind advisory continues along and southeast of the
BOS-PVD corridor for a 1 to 3 hour period of 35 to 50 mph wind
gusts. High temps will be in the 50s to perhaps a few areas near
60 across RI/SE MA. This airmass will probably reach into
portions of CT and Central MA...but parts of CT Valley and
northern MA may struggle to get much higher than the 40s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
425 AM update...

Tonight...

Frontal passage occurs this evening with strong post frontal drying,
so expect decreasing clouds and a drying trend from west to east
early. Temps may initially jump upward across the interior where
shallow cold air was unable to scour out during the day, as post
frontal winds mix down warm air aloft initially before CAA develops.
However core of cold air is delayed until Wed night/Thu. Thus only
seasonably cold tonight.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
*/ Highlights...

 - Slightly unseasonable, breezy through the remainder of the week
 - Mild conditions along with wet weather return early next week

*/ Overview...

Fairly benign pattern for the remainder of January. Progressive flow
across the CONUS with colder, Arctic air locked up around the Hudson
Bay / Davis Straight region. H3 jet streak with wave break out over
the N-Central Pacific, H5 ridge into the Bering Straight, downstream
H5 trof into the Gulf of AK into the W CONUS, but overall flat, an
unimpeded flow downstream, not greatly amplified, so long as traffic
does not bottle up across the N Atlantic. Milder pattern lies ahead
of any synoptic disturbances, wet weather as well, followed by cold
that is not as deep, slightly unseasonable, lacking a deeper Arctic
connection. However, watching early February closely. Aforementioned
H3 wave break progressing E, potential H5 ridge into the W CONUS, a
nod to ensemble signals of a +PNA pattern emerging. Winter isn`t
over just yet.

*/ Discussion...

Through Friday...

Quiet and cold. Cyclonic flow persisting aloft, additional mid-level
energy rotating through, cold air advection enhanced and maintained,
boundary layer mixing up around H9 through which NW flow prevails,
looking at slightly below seasonable conditions (typically mid 30s
for highs, around 20 for lows) and breezy conditions. Talking wind
chills as low as the single digits, possibly below zero for the N/W
high terrain. Scattered cloud decks, flurries over the Berkshires,
NW wind gusts as high as 30 to 35 mph, otherwise quiet. Some thought
as to refreezing ice jams, but cold not as deep, so perhaps river
flows elevated by Tuesday rains are uninhibited as ice jams would
not be expected to refreeze so quickly.

Weekend into early next week...

Expunging cold air prior to the onset of the next Pacific-origin
disturbance. Question progressive nature and subsequent morphology
with the potential downstream traffic. Certain Arctic air remains
locked up around the Hudson Bay region, the approaching system warm-
core, exhibiting inside-runner behavior along regions of better baro-
clinicity N and W, looking at another period of mild conditions and
wet weather over much of the NE CONUS followed by return colder air
however not exceptionally deep. However, acknowledge the spread in
ensemble member solutions, nothing is certain. Preference to slower
EC/UKmet solutions, parent with GEFS beginning to signal anomalous S-
influx trends. Cold ground prevailing, certain of fog / visibility
issues, potential for flooding with the possibility of moderate to
heavy rain, more so with swollen and/or ice jammed river basins.
Some uncertainty how quickly cold air is scoured out prior to and
with potential onset of wet weather.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Short Term /through Tonight/...

This afternoon...Moderate to high confidence. Mainly IFR with
strong LLWS. Bands of heavy rain and isolated t-storms continue
through about 21 or 22z with diminishing activity thereafter.
While the interior will struggle to mix out...should see a
period of southerly 30 to 40 knot wind gusts along and southeast
of the BOS-PVD corridor.

Tonight...Moderate to high confidence. Rapid improvement from
west to east between 22z and 02z with conditions improving to
VFR as much drier air works in from the west. Some marginal
MVFR cigs may work back into the region after midnight in the
CAA pattern...mainly across the interior.

Wednesday...Moderate to high confidence. Mainly VFR but some
brief marginal MVFR cigs possible for a time in the interior. W
winds gusts of 20 to 30 knots.

KBOS Terminal...Moderate to high confidence in TAF.

KBDL Terminal...Moderate to high confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday: VFR. Windy with areas gusts to 30 kt.

Wednesday Night: VFR. Breezy.

Thursday through Thursday Night: VFR. Windy with local gusts to
30 kt.

Friday: VFR. Breezy.

Friday Night through Saturday: Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Short Term /through Tonight/...

Today...

Southerly Gales develop with strongest winds along the waters of RI
and southeast MA this afternoon. Showers and fog limit vsby.

Tonight...

Front sweeps across the region early this evening with winds
shifting from S to west. Thus southerly gales diminish with the wind
shift along with vsby improving.

Outlook /Wednesday through Saturday/...

Tuesday: Moderate risk for gale force winds with areas of gusts
up to 45 kt. Rough seas up to 13 ft. Rain showers, areas fog,
isolated thunderstorms. Visibility 1 nm or less.

Tuesday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 12 ft. Chance of rain showers, areas
fog. Local visibility 1 nm or less.

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

Wednesday Night: Winds less than 25 kt. Local rough seas.

Thursday: Moderate risk for Small Craft Advisory winds with
local gusts up to 30 kt. Areas of seas approaching 5 ft.

Thursday Night: Moderate risk for Small Craft Advisory winds
with local gusts up to 30 kt. Local rough seas.

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.

Friday Night: Winds less than 25 kt.

Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of seas approaching 5 ft.

&&

.HYDROLOGY...
The heavy rain will mainly just result in typical brief nuisance poor
drainage street flooding. However...a Flood Watch has been issued for
the Millers River near Athol where an ice jam remains frozen in place
and has the potential to cause additional flooding.  A Flood Warning
also remains in effect for the CT River at Middle Haddam...where this
heavy rain may result in increased flooding problems as a result of
the ice jam.

For details on specific area rivers, including observed and
forecast river stages, please visit the Advanced Hydrologic
Prediction Service (AHPS) graphs on our website.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Wind Advisory until 7 PM EST this evening for MAZ013-015>024.
     Winter Weather Advisory until 3 PM EST this afternoon for
     MAZ004>007-014-026.
     Flood Watch until 6 PM EST this evening for MAZ003-004.
RI...Wind Advisory until 7 PM EST this evening for RIZ002>008.
MARINE...Gale Warning until 8 PM EST this evening for ANZ232>235-237-
     250-254>256.
     Gale Warning until 6 PM EST this evening for ANZ230-231-236-
     251.

&&

$$
SYNOPSIS...Frank/Nocera/Sipprell
NEAR TERM...Frank
SHORT TERM...Nocera
LONG TERM...Sipprell
AVIATION...Frank/Sipprell
MARINE...Nocera/Sipprell
HYDROLOGY...Staff



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