Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 202332

Area Forecast Discussion
National Weather Service Taunton MA
632 PM EST Mon Feb 20 2017

A brief return to cooler weather today continues into Tuesday
with high pressure in control. High pressure off the mid Atlc
coast combined with a series of low pressure systems moving
through the Great Lakes will result in an extended period of
unseasonably mild temperatures Wednesday through Saturday, with
near record warmth possible Thursday. A strong cold front will
cross the region Saturday, likely bringing some rain, followed
by blustery and more seasonable conditions Sunday and Monday.


630 PM update...
SKC across SNE with diminishing wind will result in a sharp
temp drop this evening across typically colder locations.
Adjusted T/Td grids for current trends, otherwise forecast on

Previous discussion...

Mid level closed low over Nova Scotia will continue to
circulate a dry cool airmass into New England tonight. Last
short wave pinwheeling around this large circulation at late
afternoon is moving across western sections of Gulf of ME and
Georges Bank. As a result winds have shifted to the NW across
northern MA along with the back edge of the cloud shield now
east of Cape Cod and continuing to move seaward.

As this last short wave moves farther offshore this evening mid
level heights begin to rise across the region and in response
surface ridge advects over the area later tonight. So with
diminishing winds, mostly clear skies and low dew pts, ideal
radiational cooling conditions will support temps free falling with

Min temps tonight were derived from the coldest MOS guid along with
shaving a few more degs off the typically cooler locations such as
the CT river valley and interior eastern MA. Lows here in the mid to
upper teens, 20s elsewhere.



Fairly high deep amplitude ridge over the region in the morning and
afternoon provides deep layer subsidence and abundant sunshine.
However as ridge continues to slide east, mid and high clouds will
begin to invade from the western horizon during the afternoon.

Chilly start to the day but despite shallow blyr mixing and light
winds from 1027 mb high overhead, temps will climb into the 40s
regionwide. Coolest readings will be along the immediate coast as
winds become onshore in the afternoon off the chilly near shore
waters with SSTs in the upper 30s.

Tuesday night...

High pressure moves offshore with WAA pattern overspreading the
region. Increasing clouds will give way to the risk for some showers
with highest pops...chance across western section of MA/CT. Only
wrinkle here is that shallow cold air may linger long enough across
northwest MA for a low risk of freezing rain. Temps around freezing
across interior eastern MA are some concern however precip may dry
up before reaching this area. Overall risk is low given marginal
cold airmass (temps near freezing vs temps in the 20s) and precip
possibly drying up as it moves eastward.



* Mild conditions Wed with near record warmth possible Thu
* A backdoor front may bring cooler temps Fri but low confidence
* Mild with widespread showers likely sometime Sat/Sat night
* Blustery and cooler Sun/Mon


Guidance in general agreement on amplifying trof moving into the
Rockies and Plains toward the end of the week with building
downstream ridge along the east coast. This will result in a
period of unseasonably mild temps into the weekend, but will
have to watch a northern stream shortwave which could allow a
backdoor front to cool things off around Friday. Models agree on
mid level low lifting across the Great Lakes Sat with inside
runner and strong cold fropa likely bringing a period of rain,
although timing and details are uncertain. More seasonable and
blustery conditions follow for Sun/Mon as broad trof develops
across the NE.


Wednesday into Thursday...

Pronounced warming trend as high pres sets up south of New Eng with
SW flow of mild air into SNE. There may be some clouds to contend
with Wed as weak shortwave moves through with low risk of a few
showers and isold fzra early in the morning interior N MA, but
expect partly sunny skies in the afternoon as mid level drying
develops from the north. Highs should reach into the 50s Wed with
upper 50s possible in the coastal plain if there is sufficient

On Thursday, continued SW flow will push 925 mb temps to near 12C
which supports highs well into the 60s away from the south coast
with partly sunny skies. Even GEFS mean 925 mb temps around 10C so
above average confidence of temps above 60 Thursday with potential
for some upper 60s with sufficient sunshine. Could see near record
highs at some of our climate sites. See climate section below.


Low confidence temp forecast as a backdoor front will be nearby and
may slip south of the region. GFS and GGEM push front to the south
with cooler temps while ECMWF hold the front to the north with temps
in the 60s again. Expect more cloud cover Fri along with a risk of a
few showers as deeper moisture moves into the region, but forcing
for ascent is limited so most of the time should be dry.


Timing uncertain but widespread showers likely to move into the
region sometime Sat into Sat night depending on the timing of the
cold front. Pre-frontal southerly low level jet should result in
more unseasonably mild temps.

Sunday into Monday...

A return to more seasonable temps with blustery W/NW winds as the
low pres moves into the Maritimes.


Forecaster Confidence Levels...

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

Short Term /through Tuesday Night/...


VFR. Diminishing winds becoming light.


More of the same, VFR with dry weather and light winds.

Tuesday night...

VFR to start then MVFR with chance of a few showers except
probably remaining dry over RI and southeast MA. Interior MA
will have to watch the potential for some -FZRA with temps near

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday...Moderate confidence. Leftover MVFR/IFR conditions
possible in the morning, then improving to VFR.

Thursday...Moderate confidence. Mainly VFR.

Friday...Low confidence. Potential for easterly flow and MVFR cigs
if backdoor front slips to the south. However, VFR with SW winds if
front remains to the north.

Saturday...Moderate confidence. Potential for widespread MVFR/IFR
conditions with rain overspreading the region.


Forecaster Confidence Levels...

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

Short Term /through Tuesday Night/...

Tonight...High confidence. Lingering marginal small craft wind
gusts/seas across our eastern waters this evening should
diminish after midnight as high pressure builds in from the

Tuesday...High confidence. High pressure overhead will result
in light winds and flat seas.

Tuesday night...High confidence with winds becoming south.
Chance of showers and patchy fog late may reduce vsby at times.

Outlook /Wednesday through Saturday/...

Wednesday into Thursday...High confidence. Mainly SW flow with
gusts to 20 kt. A few gusts to 25 kt possible Thu afternoon.

Friday...Low confidence. Winds will depend on location of a backdoor
front. Easterly flow if the front moves to the south, but continued
SW flow with gusts to 20-25 kt possible if front remains to the

Saturday...Moderate confidence. Increasing southerly flow with SCA
gusts likely. Vsbys reduced in developing rain and fog.


Record Highs for Thu Feb 23



MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ231-
     Small Craft Advisory until 6 AM EST Tuesday for ANZ250-254-255.


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