Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbox 231414 
afdbox

Area forecast discussion
National Weather Service Taunton Massachusetts
1014 am EDT Tue may 23 2017

Synopsis...
drying trend develops today with sunshine and seasonable
temperatures. Another wave of low pressure tracks south of New
England brining a period of rain to the South Coast late tonight
into Wed morning followed by another dry and seasonable
afternoon Wed. A more potent area of low pressure impacts the
region Thu and Fri with widespread showers and cooler
temperatures. Dry weather and seasonable temperatures return for
the Holiday weekend as weak high pressure builds into the area.
However the weather pattern remains progressive with the next
round of wet weather possible Sunday night into Monday.

&&

Near term /until 6 PM this evening/...
10 am update...

Surface wave/low continued to move further offshore this
morning, with subsidence resulting in increasing sunshine.
Overall today sunshine thru some mainly mid and High Deck
clouds, with highs maily in the 70s. Cooler along the shoreline
where sea breeze development is expected.

Early morning discussion follows...
==================================================================

Today...

Weak surface low will be well offshore this morning with mid-level
frontal system still stalled over southern New England. Weak mid and
low level riding will develop over the area today. This will help
break up cloud cover resulting in diurnal heating. Temperatures will
warm into the 70s with cooler conditions along the coastline.

Dry weather will prevail for most of the day with high level clouds
passing through by the late afternoon hours, ahead of the next
weather system.

&&

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

Digging shortwave across the Midwest will push a weak disturbance
over the mid-Atlantic. A coastal low will develop in response and
move into southern New England along a stalled front tonight.
Overall models have come into above average agreement with the
evolution of the trough and closed low as it progresses east. The
00z NAM is a bit of an outlier compared to the remainder of the
guidance. Therefore trended closer to the rgem, ec and GFS.

As this system moves into the region, showers will overspread across
southern Rhode Island and southeast Massachusetts. Right now it appears that the highest quantitative precipitation forecast
over the cape and islands. Model guidance may be a bit underdone on
the quantitative precipitation forecast amounts as guidance indicated that the low will close at
700mb resulting in a good fgen area northwest of the low. This may
spread precip farther north and thus have adjusted pops to indicate
the potential trend.

Wednesday...

Showers will come to an end by the morning hours on Wednesday as the
system continues to move eastward. Northeast winds will gust during
the morning hours across the cape and islands due to tight pressure
gradient from building high pressure and passing coastal low. Gusts
will be near 15 to 25 miles per hour.

Upper and mid level ridge will build into the area during the day
resulting in a drying trend. Overall, a great day as temperatures
will warm into the mid to upper 70s as skies clear out. Cooler along
the eastern coastline as sea breezes may develop.

&&

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

* widespread rain Thu and Fri with locally heavy downpours possible

* mainly dry Sat and sun then risk of more showers sun ngt/Mon

* cool Thu and Fri but more seasonable Sat and sun

Details...

Thursday...closed low over the Ohio Valley yields deep moist southerly
flow into New England with mid level warm front ovespreading the
region during the afternoon. This is accompanied by fairly robust
mid level jet (50 kts) for late may coupled with pwats of up to +2
South Dakota from climo. Thus some heavier downpours possible. Could be some
embedded thunder as well as nose of mid level dry slot approaches
and steepens mid level lapse rates.

Modest easterly low level jet up to 40 kt will provide some
windswept rain as well. This onshore flow combined with precip
and SSTs in the low to mid 50s will hold temps down.

Friday...vertically/occluded low over the region with surface low
likely tracking along or just off the South Coast. This will result
in scattered showers especially during the morning hours. Could be
some locally heavy downpours given strengthening mid level low. This
track will also keep warm sector offshore and another day of cool
temps. Although some temp recover to near 70 across CT as conditions
improve from southwest to northeast.

Holiday weekend...closed low moves into the Maritimes with rising
heights and associated subsidence overspreading the area Saturday,
providing a real nice day with highs in the 70s. Most of the
guidance keeps dry weather here thru sun except the GFS which
appears on the fast side of the envelope. By sun ngt and Mon next
northern stream trough and associated moisture will overspread our
area, thus increasing the chance of showers. Temps seasonable
Sat and sun, likely a bit cooler Mon given cloud cover.

&&

Aviation /14z Tuesday through Saturday/...
forecaster confidence levels...

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

Short term /through Wednesday/...

14z update...

Most terminals have improved to VFR, which will continue thru
today. Exception is along the cape and islands, where lingering
IFR/LIFR conditions should improve to VFR by noon. Sea breezes
expected to develop today on coastlines.

Tonight...moderate confidence. Mainly VFR with MVFR/IFR across
the South Coast, cape and islands in passing showers from
coastal low. Gusty NE winds to near 20 kts is possible near
daybreak.

Wednesday...high confidence. Improving trend to VFR.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook /Wednesday night through Saturday/...moderate to high forecast
confidence.

Wed night...VFR likely and dry.

Thursday and Friday...widespread showers in IFR/MVFR.

Saturday...drying trend along with VFR conditions.

&&

Marine...
forecaster confidence levels...

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

Short term /through Wednesday/...high confidence.

Weak high pressure will build across the waters today as showers
continue to move eastward. Another coastal low will develop
across the mid-Atlantic and move over the waters tonight.
Visibilities could drop in heavy rainfall. Improving conditions
by Wednesday as high pressure builds in the area. Despite the
active weather, seas will remain below 4 feet and gusty
northeast winds Wednesday morning will remain around 20-25 kts.
Small Craft Advisory may be needed, but confidence is low.

Outlook /Wednesday night through Saturday/...

Thursday...east-northeast winds 20-30 kt with strongest winds late in the day
and evening with low risk of low end gales. Vsby poor in rain and
fog.

Friday...winds light and variable in the morning as high pres crest
over the area. Vsby poor in showers and fog but improving as the day
progresses as winds become more northwest.

&&

Tides/coastal flooding...
high astronomical tides will occur over several tide cycles along
eastern Massachusetts coast from Thursday into Memorial Day, with
tides around 12 feet in Boston and 4 feet on Nantucket.

At the very least, minor nuisance flooding will occur in the most
vulnerable locations such as morrissey Blvd in Boston. Any surge on
top of these tides would lead to more widespread, but minor,
coastal flooding, including on Nantucket. Right now, this looks
to be a possibility Thursday into Friday due to expected onshore
winds. Model surge guidance (estofs) shows a potential 0.6 ft
surge, which would give a storm tide near 13 feet Thursday
night in Boston and just under 5 ft on Nantucket.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

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

National Weather Service Glossary of Abbreviations