Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 230703

Area Forecast Discussion
National Weather Service Taunton MA
303 AM EDT MON MAY 23 2016

We are in between weather systems today, with fair dry weather
during much of the daylight hours. Coastal low pressure moves up
the coast this evening through Tuesday bringing showers and
thunderstorms. A significant warmup will occur Wednesday,
continuing into next weekend. Scattered showers or thunderstorms
are possible from Thursday into next weekend, especially over
western sections.


Closed upper low is in place along the Northeast and Mid Atlantic
coasts, although the most significant instability remains from PA
to North Carolina through the day before moving into Southern New
England this evening.

Heating by the sun will create sufficient mixing to reach near 800
mb, where temps will support max surface values in the mid to
upper 70s. A light northeast surface wind will keep temperatures
near the Mass East Coast in the upper 50s and 60s.



Instability moving up from Eastern PA may reach western CT this
evening and bring a few showers. The more significant feature will
be low pressure surface and aloft that will move north toward New
England. This feature will bring colder temps aloft over our area,
supporting greater instability. Upper jet moving around the low
will be just east of MA with the lift-supporting left exit region
over RI and eastern MA. For both reasons, expect showers moving up
from the south tonight with sufficient instability for a couple of
thunderstorms too. Will use likely POPs, but on the lower side of
this range.

Clouds and the northeast flow off the water point to min sfc temps
near the dew point, in the lower 50s.


Core of the upper low moves over RI and Eastern MA. Similarity
among the models gives some confidence to this positioning. Core
of the cold pool aloft also moves over our area, so instability
will linger through the day. Concern remains for the chance of a
couple of thunderstorms due to the unstable airmass. We will
mention slight chance of thunder. POPs will be at high-end chance
or low-end likely much of the day.

Tuesday will be much cloudier than today so more limited mixing,
probably to 925 mb or 900 mb. Temps at these levels would support
max surface temps in the 60s.



 * Significantly warmer Wednesday into next weekend
 * Scattered showers and thunderstorms Thursday into next weekend,
   especially over western sections.

Overview and Model Preferences...

Very good agreement in the latest guidance suite in moving a
persistent upper low toward the Maritimes by late Wednesday
afternoon. Strong ridging over the north Atlantic edges west over
the southeast USA late this week. This will mean more summer-like
conditions late this week into next weekend. With the increasing
heat and humidity, also expecting the possibility for diurnal
showers and thunderstorms, each day.

Subtle, but significant, differences in the details Friday into
next weekend. The predictability of these details is rather low,
so will favor a consensus approach, for now.



Brief ridge of high pressure to our south takes over, leading to
downslope air flow, drier conditions, and more summer-like
temperatures away from the coast. There could be seabreezes, but
it appears the synoptic flow could be just strong enough to
prevent lower temperatures along parts of the MA east coast. Cape
Cod and the islands, as well as Cape Ann, however, will likely
remain as cool as the south coast of New England, where southwest
winds should prevail.

Thursday through Sunday...

This still appears to be a prolonged period of summer-like heat
and humidity, especially away from the coasts. The questions to
be answered during this portion of the forecast are: where will a
frontal boundary be between Thursday and Friday, and how quickly
will it move? A scenario can be seen where we wind up on the cold
side Friday, which would mean lower temperatures and a greater
risk for showers.

Diurnal showers, and perhaps some thunderstorms, are expected
through most of this period. The position of this front will have
a large impact on chances, and is one of the more uncertain
aspects of this forecast. Will keep a chance for showers in the
forecast until this critical detail can be better worked out.


Forecaster Confidence Levels.

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

Short Term /through Tuesday/...

Today...Moderate-High Confidence.

VFR most of the day. Areas of IFR ceilings/vsbys in patchy early
morning fog, especially in Greater Springfield and in the
lowlands of Southeast MA. Showers may develop late in the day in
CT, and toward evening along the South Coast. This could bring
local MVFR vsbys at that time.

Tonight...Moderate Confidence.

Showers and widely scattered thunderstorms move across Southern
New England. This will bring a few periods of MVFR cigs and vsbys.
Also MVFR/IFR cigs/vsbys in fog especially in RI and SE Mass.

Tuesday...Moderate Confidence.

Showers and widely scattered thunder will continue. Areas of
MVFR/IFR in showers and fog areas. Conditions may improve to
mainly VFR especially in CT and Western MA late in the day.

KBOS TAF...Greatest uncertainty is in timing of showers for this
evening and tonight. Because of this any mention of showers has
been tagged as vicinity rather than directly mentioned.

KBDL TAF...Greatest uncertainty is in timing of showers for this
evening and tonight. A couple of showers could reach the airport
between 5 PM and 8 PM, but more likely to occur after 8 PM.

Outlook /Tuesday Night through Friday/...

Wednesday...High Confidence. Mainly VFR.

Thursday...Moderate Confidence. Mainly VFR. Scattered MVFR in
scattered showers and thunderstorms, mainly west of KLWM-KORH-KIJD.

Friday...Moderate Confidence. Mainly VFR. Scattered MVFR in
scattered showers and thunderstorms.


Forecaster Confidence Levels.

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

Today...Moderate Confidence.

Low pressure moves up the coast from Virginia and the Carolinas.
Most of the day will be fair with North winds turning from the
Northeast. Speeds will be 15 knots or less. Seas will slowly
subside through the day with lingering 5 to 7 foot seas subsiding
through the day. Small craft advisory for hazardous seas is in
effect, mostly for the outer waters, through the day.

Tonight and Tuesday...Moderate Confidence.

Coastal low pressure moves across the waters. This will bring
showers and widely scattered thunder with lower visibility in
showers and fog. Winds will remain 15 knots or less, and seas will
mostly be less than 5 feet. A few 5 foot readings could show up on
the southern outer waters Tuesday.

Outlook /Tuesday Night through Friday/...

Wednesday into Friday...High Confidence.

High pressure briefly builds over the waters. Mainly quiet
boating weather is expected with winds and seas below Small Craft
Advisory levels.


MARINE...Small Craft Advisory for hazardous seas until noon EDT today
     for ANZ231-251.
     Small Craft Advisory for hazardous seas until 11 PM EDT this
     evening for ANZ250-254-255.
     Small Craft Advisory for hazardous seas until 8 AM EDT this
     morning for ANZ256.


MARINE...WTB/Belk is the U.S. government's official web portal to all federal, state and local government web resources and services.