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Area forecast discussion 
National Weather Service Taunton Massachusetts
726 am EDT Friday Aug 22 2014

Synopsis...
the threat for showers will continue...especially across the west
through tonight. Drier and cooler weather follows this weekend. A
warm-up is possible next week prior to an unsettled pattern ahead
of a frontal boundary sweeping south out of Canada.

&&

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

Latest runs of the hrrr appear to have a good handle on the
showers this morning...at least in terms of the overall trends.
As such...used the hrrr to tweak probability of precipitation for this morning. Also
tweaked temperatures and dew points to reflect the latest
observed trends.

Previous discussion...

Showers continue to develop in-situ this morning across the region
as the first of a series of vort-Max/S moves through the region
early this morning. Precipitable waters are marginal /around to just below 1.5
inches/ with k-vales in the west about 30-32. Therefore...suspect
this threat for -shra to continue through the morning. Especially
were weak convergent boundaries are allowed to form in the
relatively weak near surface flow. Will carry probability of precipitation through middle day
mainly west of the Worcester Hills into southern New Hampshire...but would not be
surprised to see a few showers make it into the bos-pvd corridor.

Otherwise today...this first vorticity maximum is expected to join forces
with cutoff low pressure stalled in blocking flow across Atlantic
Canada...forming a hanging trough whose base will rest to the S of
region. Note that as this trough develops and a series of weaker
waves rotate through...heights continue decline into the overnight
hours. Overall column moisture does actually diminish through the
day...closer to between 1.0-1.25 inches and overall instability
/including k-values/ diminish through the day as well. Given
this...and the fact that another axis of surface based instability
remains to the west in New York thanks to what is likely to be more clear
skies...and continued marine influence thanks to east component to
the flow suspect convective activity to once again fire mainly west
of New England this afternoon and evening. This may actually usurp
some of the available moisture...so will actually highlight
declining probability of precipitation through the afternoon...except in the due to
remnant convection advecting east.

As mentioned...expect a lot more widespread cloud cover today
thanks to marine influence and cooling temperatures aloft.
Therefore...highs may struggle to make it out of the 60s in spots.

&&

Short term /6 PM this evening through 6 PM Saturday/...
tonight...
am noting similar setup as Thursday night. Another weak shortwave will
push north-S across the region and phase with offshore longwave trough
connected to cutoff in Atlantic Canada. Two conditions are
different however...precipitable waters are a bit lower /1.0-1.25 inches as
opposed to 1.5/ and k index values are lower as drier air intrudes
through the column from the top down. Therefore...save for the
advection of leftover convection from the west...suspect that -shra
are likely to be a bit weaker and less widespread than Thursday night.
However...will still maintain at least chance probability of precipitation especially for
west and northwest portions of the forecast area.

One other issue is fog and/or low ceilings moving into east portions of
the forecast area. Guidance continues to note an area of moisture
backing in from the Gulf of Maine overnight thanks to continued
Ely component of the flow. Do note in BUFKIT profiles that there
is a layer of dry air above the surface which may negate fog
development...especially if stratus backs in...limiting radiative
processes. Therefore...will mainly mention low clouds...but may
need to monitor for drizzle with drier moving in over moisture
pooling in the low-middle levels. Should some areas radiate...fog
remains a risk.

Sat...
one last parting shot for showers Sat as shortwave energy forces
some digging and southward progression of the offshore longwave
trough. Leftover moisture combined with cooling temperatures aloft are
likely to lead to a fair amount of cloud cover during the early
half of the day...along with showers especially from portions of
the Merrimack valley east and points southeast. However...improvement by the
afternoon looks possible thanks to gradually rising heights from
the S shift in the trough. This will allow surface inverted ridging to
gradually regain control across the region toward evening. In
fact...despite the cloudy start to the day...its possible many
locations still get to see the sunset /even in the east which will
likely take the longest to break out/. Highs remain on the cool
side of normal thanks to the early cloud cover limiting diurnal
influence.

&&

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

* quiet weather expected through much of this period
* uncertainty increases middle of next week with an approaching
front

21/00z models are in good agreement through about Tuesday. Then
significant differences arise for the latter half of next week...
making for a lower confidence forecast from the middle of next week
Onward.

A persistent upper level trough over the northeast will slowly make
its way east...moving just offshore this weekend as an upper level
ridge tries to push northeastward from the southern USA. This upper
trough is rather persistent though...with each successive model run
lingering this trough over the North Atlantic longer and longer.

Cooler...less seasonable weather is expected while high pressure in
Quebec will keep things relatively dry. Still agree with the
previous forecaster...thinking 21/00z guidance continues to struggle
with convective feedback into early next week. As such...kept a dry
forecast across most of southern New England.

A high pressure will sink south into early next week...eventually
moving south and east of southern New England and returning US to a
more westerly flow. A low pressure in Ontario may eventually move
east into Quebec...swinging a cold front through southern New
England Wednesday or Thursday. This is where models start to diverge
more significantly.

The European model (ecmwf) looks a bit quicker than the GFS with the approach of this
front...but neither is as progressive as the Canadian. Will take a
blended approach with the timing for now. Given the strength of the
surface ridge expected to be near the coast...would not be overly
surprised if the ultimate timing turns out to be slower than the
GFS. Depending on available moisture...we could see some showers and
thunderstorms ahead of this front.

&&

Aviation /11z Friday through Tuesday/...
forecaster confidence levels...

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

Short term...through Saturday...moderate confidence.

Today into tonight...
conditions improve to VFR most locations through the day...
although low VFR ceilings are likely especially areas west of the
Worcester Hills. Showers linger in this region as well. By
tonight...showers dissipate but there may be more widespread fog
in the west and the possibility of lower ceilings in the east.
Therefore...complex overnight scenario...where some occasional
MVFR/IFR conditions are possible.

Sat...
conditions improve to VFR all locations except maybe areas east of
the wst-orh-afn...where some MVFR conditions may linger into the
day in low ceilings. By afternoon...likely to see VFR all locations.

Kbos terminal...moderate confidence. Mainly VFR today except for
occasional showers and MVFR this morning. Overnight...easterly
flow could yield a period of low clouds with MVFR/IFR ceilings
possible. Should these be established...its possible they linger
into the morning hours Sat.

Kbdl terminal...moderate confidence. MVFR/VFR may bounce back and
forth through the morning with showers. By afternoon...conditions
improve to VFR and may stay that way thereafter.

Outlook...Saturday through Tuesday...

High confidence VFR. Low probability of patchy MVFR/IFR fog each
night.

&&

Marine...
forecaster confidence levels...

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

Short-term...through Saturday...high confidence.

East to NE flow will continue into Sat as high pressure to the NE slowly
regains control. Through the day today and night tonight...periods
of wind gusts of 15-20 knots are possible at times with a slowly
building swell. Seas should remain below 4 feet even on the southeast and S
waters. Therefore...no small craft headlines. Some fog and showers
are possible on the waters at times as well...mainly this
morning...and once again overnight.

Outlook...Saturday night through Tuesday...

High confidence.

High confidence. Quiet boating weather is expected for much of this
period with high pressure across the region. Seas could approach 5
feet across the outermost southern coastal waters this weekend. Not
enough confidence to issue a Small Craft Advisory though. Low
probability of patchy overnight fog limiting visibilities.

&&

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

&&

$$
Synopsis...Belk/doody
near term...Belk/doody
short term...doody
long term...Belk
aviation...Belk/doody
marine...Belk/doody

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