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Area forecast discussion 
National Weather Service Taunton Massachusetts
1033 PM EDT Thursday Jul 2 2015

Synopsis...
a cold front shifts south of New England tonight. High pressure
builds over the region later tonight and Friday. A mainly quiet
and dry 4th of July Holiday weekend beneath high pressure is
maintained into early next week. Thereafter the weather takes a
turn towards a warm...muggy...wet-weather pattern with chances of
showers and thunderstorms by midweek possibly continuing into the
following weekend.

&&

Near term /until 6 am Friday morning/...
1030 PM update...

Regional radar data...as well as latest runs of the hrrr...showing
an increased chance for showers across the South Coast of New
England. A secondary still expecting the majority of showers to
remain south of the islands. A middle level shortwave moving through
our region was responsible for generating the second area of
showers along and south of Long Island. It is this area of
showers which will most likely impact Cape Cod and the islands
later tonight. These showers should move out to sea late tonight.

Other than tweaking probability of precipitation...also tweaked sky cover and temperatures
to reflect latest observed trends.

&&

Short term /6 am Friday morning through Friday night/...
Friday...
high pressure builds over the region with plenty of subsidence.
Expect clear or mostly clear skies. Pressure gradient will be
light...so light winds through the day. This should allow sea
breezes to form along the coasts late morning/early afternoon. The
mixed layer is forecast to reach 850 mb with afternoon temperatures at
that level around 10c. Mixing this to the surface should support
maximum temperatures in the upper 70s...call it 75 to 80. Cooler values where
the sea breeze takes hold.

Friday night...
high pressure shifts east but remains in control over New England.
Another shortwave moves over the Great Lakes and forms another
wave along the front to our south. This should generate another
area of clouds and showers that approach from our south overnight.
We will bring some increase in sky cover during the night with the
most cover along the South Coast. But the dry air in place and the
focus of supporting lift to our south should keep the weather dry.
With dew points in the 50s...min temperatures should be in the 50s and
around 60.

&&

Long term /Saturday through Thursday/...
*/ highlights...

- possible shower activity for the 4th of july?
- Dry into early next week...perhaps warmer
- return of warm...muggy...and wet-weather by midweek
- chances for thunderstorms and heavy rain

*/ discussion...

An Ebb and flow pattern. Should a 500 mb low anomaly maintain across the
North Atlantic with 500 mb ridging in and around the vicinity of the west Continental U.S.
Then 500 mb troughing would be preferred through the c-Continental U.S. Along the east-
periphery of which the NE-Continental U.S. Would experience an active weather
pattern while wobbling between airmasses. Nothing is certain as the
atmospheric is chaotic...but interpreting anomalies as of late while
interrogating ensemble data leads to confidence that we will not be
seeing heat-waves nor 100-degree temperatures anytime soon. A sway
of temperatures not out of the question with exchanging
airmasses...going from cool and dry to warm and muggy...a
pattern as of late that is likely to continue. It will be
interesting to see if we draw parallels to the weak El-Nino Summer
of 2004 with the c-Continental U.S. Having well below-normal Summer
temperatures with the NE-Continental U.S. Holding near-normal.

Lets keep it simple and straight-forward with the above discussion
in mind. A consensus of forecast guidance is warranted as there is
overall good agreement into early next week. By midweek there are
signals of discrepancy as forecast guidance handles the return of
warm and muggy conditions along with the chance of showers and
thunderstorms. Best to look at cips analogs to see if there is any-
thing we should be concerned about on the horizon.

*/ Dailies...

July 4th weekend:

18z update...

The 02.18z GFS considerably obliterates 4th of July festivities
with a decent slug of rain as an area of low pressure deepens
across S New England. Appearing as an outlier as of present and
will treat it as so. Nevertheless the 02.12z European model (ecmwf) ensembles have
roughly a split of 50 members...half dry and the other half
suggesting some sort of wet-weather. 02.18z NAM continues the
forecast trend of wet-weather over PA perhaps advecting east/NE with
the mean flow into S New England by which time it is mainly middle-
level clouds into an area of low pressure and drier air.

Will have to keep a close-eye on this ever changing forecast and
now a growing uncertainty that it may not remain dry over S New
England after all.

Previous discussion...

Weak high pressure and dry-capping mechanism keeps US perhaps quiet
and dry throughout the period? Yet there has been an indication of a
Stout stretched middle-level vortex through the overall trough-pattern
for quite some time. Will need to monitor the relative strength of
the high up against the forcing mechanisms associated with middle-level
energy aloft...whether we can get some shower activity mainly per
middle-level forcing in what appears to be a rather dry environment
with a measure of stability. Will keep with a mostly-dry forecast
for now but holding slight chance probability of precipitation over S and west portions of S
New England...with chance probability of precipitation S offshore.

Otherwise low- to middle-level cloud decks encroach from the west. Flow
looks to be rather light...and beneath high pressure may make for
some smokey fireworks displays. Perhaps some faster flow moves in by
3z as the 02.12z NAM suggests but think its too robust. Wind speeds
through midnight look to be around 5 miles per hour and not entirely clear as
from what direction. Seasonable temperatures throughout.

Early next week:

Keeping it dry. High pressure sweeps across the region. Chilly into
Monday morning but begin to see return S-flow by the end of the day
going on into Tuesday. Could see a warmer-than-average pattern at
least by Tuesday with 850 mb +14c air moving in aloft. Highs around the
middle-80s with low-lying interior river valleys into the upper-80s.

Midweek:

A return of warm-muggy conditions ahead of a sweeping synoptic low
disturbance from the north. Increasing instability and moisture along
and ahead. Confidence towards chances of showers and thunderstorms.
From the cips analog guidance...analogs derived from the 0z gefs
have a 60% chance of above-average precipitation for portions of the
NE-conus...and naturally with the aforementioned environment...the
threat of heavy rain is not out of the question.

Should the troughing pattern persist as a consensus of deterministic
solutions suggest then we could be looking at rounds of wet-weather
all the way through the week into next weekend. Low confidence. No
certainty on outcomes. Will maintain seasonable conditions through-
out the forecast.

&&

Aviation /02z Friday through Tuesday/...
forecaster confidence levels...

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

Short-term /through Friday night/...

0230z update...

Tonight...high confidence.
VFR. Light winds gradually turning E/se. Scattered rain showers toward
Cape Cod and the islands for a time around midnight. Possible IFR
fog towards morning.

Friday...high confidence.
VFR. Sea breezes developing.

Friday night...high confidence.
VFR.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Saturday through Tuesday/...moderate confidence.

VFR. Vrb winds with sea-breezes along the coasts. More prominent S-
winds by Tuesday.

&&

Marine...
forecaster confidence levels...

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

Short-term /through Friday night/...

1030 PM update...

West to southwest winds become northwest to north...but remain
well below 20 knots. Forecast remains on track.

Friday and Friday night...
high pressure moves over New England. Winds and seas should remain
below small craft thresholds.

Outlook /Saturday through Tuesday/...

Variable winds throughout with sea-breezes along the coasts will
make for good boating weather through Monday. More prominent S-winds
are anticipated by Tuesday with gusts up to 15 kts. Will hold seas
below 5-feet despite anticipated swell from west-east S-offshore storm
systems.

&&

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

&&

$$
Synopsis...wtb/sipprell
near term...wtb/Belk/sipprell
short term...wtb
long term...sipprell
aviation...Belk/wtb/sipprell
marine...Belk/wtb/sipprell

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