Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbox 291056 
afdbox

Area forecast discussion
National Weather Service Taunton Massachusetts
656 am EDT Thu Jun 29 2017

Synopsis...
a warm front moves through the region this afternoon with a few
showers and thunderstorms possible across northern Massachusetts
tonight, as more humid air moves in. Summer heat and humidity
arrives Fri and continues into the weekend. A cold front likely
breaks the heat and humidity later Sunday and will be
accompanied by thunderstorms. Not as warm or humid early next
week including the Fourth of July Holiday.

&&

Near term /until 6 PM this evening/...

7 am update...

Overall trend in the forecast remains on track early this
morning. Made some minor adjustments to precip chances. Latest
radar imagery continues to show a few spot showers across the
Mohawk Valley in New York. Believe this may be more virga then rain as
ceiling heights are well over 10k. Still cannot rule out a few
sprinkles for western Massachusetts but very little impact is expected.

Otherwise, warm front will continue to lift northward today.
Showers will ride along the front which will be near the Massachusetts/New Hampshire
border so a few late morning/early afternoon precip could impact
locations north of Route 2. Overall anticipate a mainly dry day
with more clouds than sun.

Today...

Cirrus canopy continues to stream across southern New England in
response to warm air advection pattern ahead of Great Lakes trough. As warm front
approaches the region expect clouds to lower and thicken this
afternoon. Not expecting much if any precip with this feature as
best lift and deep layer moisture track into central New England.
Thus greatest risk for any showers today associated with warm
frontal boundary will be along the ME/New Hampshire border. So most of the
region remains dry today.

As low level jet moves across the area breezy conditions will
develop later this morning into the afternoon with SW winds 15-20 kt
gusting up to 25 mph.

Given the warm air advection pattern temps will be a few degs warmer than yesterday
with highs in the upper 70s and low 80s. Most sunshine (through mid-
high clouds) will be south across CT/Rhode Island and southeast Massachusetts. Becoming
slightly more humid as well as dew pts climb into the upper 50s and
low 60s.

&&

Short term /6 PM this evening through 6 PM Friday/...
tonight...

Warm front lifts north of the region with warm sector airmass
overspreading southern New England. Thus becoming more humid as dew
pts rising into the 60s. This will result in patchy fog.

Any possible mesoscale convective system will track well north of the region as nose of 850 mb-
7 jet tracks across northern New England. Thus best chance for any
showers/T-storms would be across northern Massachusetts (including city of
boston) toward the New Hampshire border.

Remaining breezy across southeast Massachusetts in response to tight SW pgrad.

Given warm sector airmass a mild night with lows only in the mid to
upper 60s.

Friday...

Subtropical ridge begins to build northward up the East Coast with
height rises into southern New England. This will suppress
convective chances by providing a cap over the area. However can/T
rule out a few storms across western Massachusetts/CT especially across the
higher terrain. Nevertheless much of the region remain dry Fri.

It's a warm airmass over the area Fri with good model agreement on
925 mb temps at +22c and +17c at 850 mb. This supports highs in the
upper 80s to low 90s. Heat indices will be higher as dew pts climb
into the mid to upper 60s. Fortunately there will be a bit of a SW
breeze with winds 15-20 mph, gusting up to 30 mph across southeast
Massachusetts.

Beach forecast...could be some rough surf at ocean beaches along the
South Coast of Massachusetts and Rhode Island as persistent southwest winds today and Fri
generate at least a moderate surf.

&&

Long term /Friday night through Wednesday/...
highlights...

* hot and humid conditions continue for Saturday into Sunday
* scattered showers/thunderstorms for the weekend
* cooler and less humid Monday and Tuesday

Pattern details...

Overall the deterministic models and their ensemble means have a
fair handing on the evolution of the synoptic pattern for the
period. However, there still remains the timing and strength
difference with each shortwave. Southern New England remains in
northerly stream as quasi-zonal flow become more amplified Friday
night into Saturday. This will result in a deeper trough over the
northern plains, and thus a building of the sub-tropical ridge over
the East Coast. This ridge stalls an approaching cold front for the
weekend before pushing through on Sunday/Monday. Pattern change
aloft for early next week as the region is more in the broad trough
keeping heat and humidity at Bay. Guidance difference increases by
mid-week with the ec more amplified versus the progressive GFS.
Overall, trended towards a blend in the guidance unless otherwise
noted below.

Details...

Friday night...

Lingering showers/thunderstorms will come to an end during the
overnight hours. This is thanks to mid-level dry air pushing into
the area and building subtropical ridge. Still plenty of clouds will
keep overnight temps near 70f. Increase low level moisture and
higher dewpoint airmass will result in areas of fog, especially
across the South Coast.

Saturday into Sunday...

Subtropical ridge will remain just to our east with southwest flow
in place. Southern New England will remain in the warm sector for
the weekend with precipitable water values reaching near 2 inches. Plenty of
instability each day and moderate shear in place will help sustain
thunderstorm potential.

On Saturday, the eastern half of the region will remain dry as mid-
level relative humidity values and k indicies remain low. However, across the
western half, appears that any storms that develop in New York will bleed
into western MA/CT. Some of these may still be strong as they are
closer to a surface pre-frontal trough.

Showers and thunderstorms may linger through the overnight hours as
mid-level shortwave and surface cold front approaches the northeast.
This front will stall as it moves across southern New England thanks to the eastern
ridge on Sunday. As heights and temps aloft begin to fall,
convection may fire along this stalled front. Still some
uncertainty on location and timing but latest trends is bos-hfd and
points east. Cannot rule out a few strong/severe storms as
instability values will be above 1000 j/kg and shear values
increasing to 30 kts with deep layer moisture. Something to watch in
the coming days.

Temperatures during this period will be above average with high
temps in the upper 80s to low 90s. Dewpoints in the 70s may result
in heat indicies above 95f. Low prob of heat headlines.

Monday into Tuesday...

Stalled front will push through on Monday as upper level trough will
move overhead. This will limit the heat and humidity keeping temps
seasonable, with highs in the mid 80s. Several shortwaves will move
through the flow during this period. While most of the period
remains dry, westerly/unsettled flow with cold pool aloft may
trigger a few isolated showers.

Wednesday...

Large spread in the guidance for this period. Trended towards wpc
with stalled boundary south of the region. Surface high pressure
from Canada will move through the northwest flow and settle over
southern New England.

&&

Aviation /12z Thursday through Monday/...
forecaster confidence levels...

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

Short term /through Friday/...high confidence.

7 am update...

Today...

VFR cigs and vsbys continue with low risk of light rain late in
the day across northern Massachusetts to the New Hampshire border. SW winds increase
this afternoon with gusts up to 25 kt across Rhode Island and southeast
Massachusetts.

Tonight...

VFR and mainly dry across CT/Rhode Island and southeast Massachusetts. Chance of
scattered showers and T-storms mainly across northern Massachusetts. MVFR
vsbys possible across the interior in patchy fog. Modest SW
winds 15-20kt likely along the South Coast of MA/RI.

Friday...

Mainly VFR with low risk of a few T-storms mainly across the
interior during the afternoon. Gusty SW winds continue 15-20 kt
with gusts up to 25 kt possible.

Kbos terminal...high confidence. Mainly dry thru 00z with low
risk of a few showers/T-storms thereafter.

Kbdl terminal...high confidence.

Outlook /Friday night through Monday/...

Friday night into Sunday...moderate confidence. Early morning fog
each day. Otherwise mainly VFR, except local IFR in possible strong
thunderstorms, mainly during the afternoon and evening hours through
the period. Southwest winds through the period with gusts near 20
kts.

Monday...moderate confidence. Improving conditions to VFR with
westerly flow. A low risk for spot shower.

&&

Marine...
forecaster confidence levels...

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

Short term /through Friday/...high confidence.

Today...

Increasing SW winds up to 25 kt late this afternoon across the
southern waters of MA/RI. Strongest winds near shore. Mainly dry
weather along with good vsby.

Tonight...

SW winds 15-20 kt continue with highest speeds across the southern
coastal waters of Massachusetts and Rhode Island. Scattered showers and T-storms possible
over the northern Massachusetts waters. Vsby may lower to 1 mile or less in
areas of fog as humid airmass overspreads the waters.

Friday...

SW winds 20-30 kt across the southern waters. Strongest winds near
shore. Morning fog may reduce vsby 1-3 miles. Mainly dry with any T-
storms confined to the interior.

Outlook /Friday night through Monday/...

Saturday into Sunday...SW winds continue, mainly 20 kts with
lingering seas. Scattered thunderstorms, some with reduced
visibilities and strong gusty winds especially on Sunday.

Monday...westerly flow as cold front stalls over the waters. A spot
shower is possible, but overall improving wind and seas.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 1 PM this afternoon to 8 PM EDT
Friday for anz231>237-255-256.
Small Craft Advisory from 3 PM this afternoon to 2 am EDT
Friday for anz230.

&&

$$
Synopsis...nocera/dunten
near term...nocera/dunten

National Weather Service Glossary of Abbreviations