Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 220024
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
724 PM EST Tue Feb 21 2017

.SYNOPSIS...
A weak cold front dissipates as it crosses New England late
tonight. Unseasonably mild temperatures will remain across
southern New England late this week as weak low pressure
systems pass west of the region. A strong cold front will cross
the region Saturday afternoon and evening, bringing showers and
possibly a few thunderstorms. Near seasonable temperatures will
return early next week, with blustery conditions on Sunday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...

7 PM Update...

Bands of high clouds crossing the region out of NY state as seen
on latest NE regional IR satellite imagery. Also noting some mid
level clouds on latest surface OBS across the northeast. Noting
some light precip moving E out of NY state, but appears most if
not all has not reached the ground. Rather wide T/Td spreads of
15-20 degrees per 00Z OBS across the CT valley. SE winds across
NE Mass at 00Z shifted to S-SW further W, though remaining
light as high pressure pushes SE off of Nantucket.

Looks like it will take a while for precip to reach the ground,
if it does with the dewpt depressions. They may decrease
overnight with slowly increasing low level moisture. Have left
previous forecast intact for the remainder of the overnight
hours. Still could see a little precip reach the ground, so
warrants the CHC POPS going.

Have updated near term forecast to bring conditions current.

Previous Discussion...

High pres moves offshore tonight with weak warm advection
developing along with weakening shortwave moving into New
England. Forcing for ascent is limited but models indicating
deep moisture plume moving across SNE 06z-12z. A few showers
possible mainly after midnight as this moisture plume and weak
shortwave moves through but some areas may remain dry.

Will maintain low chc pops for late tonight. The main issue is
the potential for patchy light freezing rain across interior N
MA as the precip moves in and temps will be near freezing here.
Elsewhere, expect temps will be mostly above freezing. Since
temps will be marginal and some areas may remain dry, no
advisory will be issued but will address potential for some
spotty icy spots in an SPS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Wednesday...
Moisture axis will be oriented south of the Pike by 12z and
moving south of the coast during the morning. Clouds and a few
showers are possible in the morning across CT/RI and SE MA,
otherwise mid level drying moving in from the north should
allow ptsunny skies to develop late morning into the afternoon
from north to south. SW flow will bring milder temps into SNE
with highs likely reaching the low/mid 50s across most locations
but cooler Cape/Islands and higher terrain. However, potential
for upper 50s to near 60 in the coastal plain if there is
sufficient sunshine. Cloud cover may limit full heating.

Wednesday night...
Mainly dry conditions and above normal temps with modest SW
flow persisting. Patchy low clouds and fog may develop
overnight. Lows will range through the 30s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...

* Record warmth remains possible Thursday
* Scattered showers possible with mainly mild temps on Friday
* Widespread showers expected Saturday-Saturday night, with a
  few thunderstorms possible
* Blustery and seasonably cool Sunday-Monday

Overview...

Overall upper level pattern continues across the lower 48 late
this week, with building H5 ridge across the eastern U.S. as a
trough digs out of the Rockies into the Plains states. This
trough will slow surface systems down on Thu and Fri, with high
pressure pushing offshore. A weak cold front may briefly work
into northern areas Fri, but will retreat quickly north as S-SW
winds pick up so could see another mild day for most areas.

The big question is the timing of the surface system/developing
cutoff H5 low that will work slowly east either Fri or Sat.
Models seem to have a decent handle on the movement and shearing
of the mid level system into Quebec, but some question as to
the timing of the associated cold front. At this point, looks
like it should push across Saturday into Saturday night. This
will likely bring a decent amount of rainfall, and may even see
a few thunderstorms ahead of the front.

Beyond this, cutoff low pres over central Canada should keep
progressive pattern in place through the remainder of the
weekend into early next week with seasonable temperatures
returning.

Details...

Thursday...

High pressure off the eastern seaboard will keep steady stream
of mild air pushing northward across the region. Could see some
isolated showers move across western areas during the day, but
models having a tough time handling the low level moisture
field. Noting mainly light QPF during Thu night. Leaned toward
the drier solution with the weakening system, at least with any
shower activity during the day Thu.

Noting a strong low level jet pushing across the region Thu
afternoon and night ahead of weakening cold front. Low level
mixing is marginal, though does improve between H925 and H95
after 00Z Fri across S coastal areas, so could see brief gusts
up to 20-25 kt.

Area of clouds may linger, especially across central and
western areas during the day, which may cut back on the full
heating potential. Depending upon how much mixing takes place up
to H925, where readings will be around +10C to +11C, and
whether the clouds could actually clear for a time, temps may
reach the lower-mid 60s. Record highs may be close at KPVD and
KORH, but may be tougher to reach at KBOS and KBDL.

Low level capping seen on 12Z BUFKIT soundings Thu night, which
could trap low level moisture along the S coast with the SW
winds in place. Have mentioned patchy drizzle during the
nighttime hours for those areas. May also see some isolated
showers during the overnight as well, mainly across central and
western areas, but precip will be light.

Friday...

Cold front stalls just S of the region Fri morning, but temps
will not get too cool as H925 and H85 temps remain on the mild
side. Light E-SE winds in place early in the day will shift to
S-SW again as system returns as a warm front during the
afternoon. This will be ahead of low pressure moving across the
Great Lakes. May see scattered showers mainly from the Mass Pike
northward during the day ahead and with the front.

With a light onshore flow on both coasts, temps will be a bit
cooler there. However, another mild day on tap for inland areas
though not quite as warm as expected on Thursday. Readings away
from the coast and into the inland valley could approach or
exceed 60 in some spots. Otherwise temps mainly reaching the
50s.

Saturday...

Will be an active day. Low pressure will push into Quebec
during the day with the weakening upper level cutoff low.
However, its associated short wave will wrap across the region.
Strong vorticity ribbon with this short wave, along with band of
instability. Noted LI/s near zero, total totals in the lower
50s and TQ values up to 18-19 for elevated convection. So, have
also mentioned a slight chance for thunderstorms Sat afternoon
and evening for now. Have also noting good low level southerly
jet up to 35-45 kt ahead of the front, so could see some of this
mix down with any convection.

Cold air will wrap in quickly overnight Sat night as the precip
tends to cut off. Could still see a quick mix or changeover to
snow showers across central and western areas. System pushes
offshore quickly though, so may not see much of a wintry mix
toward the coastal plain as the moisture ends quickly.

Highs on Saturday may reach the lower 60s across interior E
Mass and the CT valley, otherwise readings mainly in the 50s.
Temps fall quickly overnight, bottoming out in the 30s at most
locations, except around 40 on the outer Cape and the mid-upper
20s over the higher inland terrain.

Sunday through Tuesday...

Cold front pushes offshore by 12Z Sun, so should see mainly dry
conditions for Sunday. Blustery NW winds in place, with gusts
up to 25-30 kts, highest along the immediate coast and higher
terrain. The gusty winds will make it feel more like
temperatures in the mid 20s to mid 30s during the day, though
actual highs will be close to seasonal normals /mid 30s to mid
40s/.

May see another weak short wave quickly move across Sunday
night-Monday. Have only carried slight chance POPs with this
system as it appears to be moisture starved in the W-NW flow
aloft. This is ahead of another reinforcing cold front. Timing
of this system is in question though with fast flow aloft.

For now, Tuesday should be a dry and seasonable day as high
pressure builds across. Winds should diminish. Systems continue
to move quickly in progressive flow aloft, so timing this far
out is in question.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

Short Term /through Wednesday Night/...

Through 00z...
VFR with increasing high clouds. Coastal seabreezes developing.

Tonight...Moderate confidence.
VFR cigs, but areas of MVFR developing late tonight in western
MA and portions of northern CT. A few showers possible mainly
after midnight with low risk of patchy freezing rain in interior
northern MA.

Wednesday...Moderate confidence.
Patchy MVFR cigs/vsbys in the morning, mainly from CT valley to
the south coast, improving to VFR in the afternoon. Low risk of
a morning shower near the south coast.

Wednesday night...Moderate confidence.
Areas of MVFR/IFR cigs may develop along with patchy fog.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Thursday through Sunday/...

Thursday...Moderate confidence. Mainly VFR across most of E Mass.
MVFR-IFR CIGS lingering along the S coast, Cape Cod and the
islands, possibly into the CT valley Thu afternoon/night. Patchy
fog may develop overnight as well with local MVFR-IFR VSBYS.

Friday...Low confidence. Leftover MVFR-IFR VSBYS through mid
morning in patchy drizzle/fog. CIGS improve to VFR, though may
see patchy MVFR-IFR CIGS as warm front pushes N during the day,
especially across central and N Mass. Scattered showers linger
across the interior. Light E-SE winds shift to S from S-N Fri
afternoon and evening. May see gusts up to 20 kt along the S
coast.

Saturday...Moderate confidence. Areas of MVFR-IFR CIGS/VSBYS in
showers and patchy fog. Low risk for isolated thunderstorms Sat
afternoon/evening. A few snow showers possible across western
areas before precip ends. Conditions may improve to VFR after
midnight across western areas.

Sunday...Moderate confidence. A few rain and/or snow showers
may linger across central and eastern areas through mid morning
Saturday with local MVFR conditions.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Wednesday Night/...High confidence.

Persistent SW flow through the period with windspeeds and seas
remaining below SCA. However, may see a few gusts 20-25 kt late
tonight into Wed morning across eastern MA waters.

Outlook /Thursday through Sunday/...

Thursday...High confidence. S-SW winds in place, gusting up to
around 20 kt during the afternoon. Gusts up to 25 kt and seas
building to around 5 ft on the outer waters Thu night. May see
patchy drizzle and fog develop Thu night along the S coast with
reduced visibilities.

Friday...Low confidence. Winds should become light N-NE across
the eastern waters Fri morning, with light/variable winds on the
southern waters. Expect winds to shift back to S-SW during the
day as warm front pushes N. May see gusts up to 20 kt on the
outer water Fri night. Local visibility restriction in patchy
fog.

Saturday...Moderate confidence. S winds increase, gusting to
around 25 kt. Small crafts likely. Seas build up to 5-8 ft on
the southern outer waters. Reduced visibilities in showers and
patchy fog. Low chance for thunderstorms Sat afternoon/evening.

Sunday...Moderate confidence. Winds shift to W and gust up to
25-30 kt. Seas up to 6-9 ft on the open waters.

&&

.CLIMATE...
Record Highs for Thu Feb 23

BOS...65/1990
BDL...68/1990
PVD...60/1990
ORH...61/1990

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC/EVT
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT
MARINE...KJC/EVT
CLIMATE...Staff



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