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Area forecast discussion 
National Weather Service Taunton Massachusetts
647 PM EDT Thursday Jul 10 2014

a stalled cold front just offshore will finally move south of the
region early Friday. Drier and more seasonable weather will then
continue into Saturday. Unsettled weather returns late Sunday
into early next week with the risk of showers and thunderstorms
along with increasing humidity.


Near term /until 6 am Friday morning/...
645 PM update...showers and thunderstorms across the Delaware-Maryland-Virginia
peninsula continue to weaken as they move towards southern New
England. Most showers have stayed just southeast of Nantucket so far.
Have made minor updates to the temperatures and dewpoints to
account for the latest trends. Otherwise...the forecast is on
track. Previous discussion follows.

Currently...mass fields and available observation suggest cold frontal
boundary is stalled just off of Mainland southern New England...from
ack sound SW to Long Island. Convection near southern New Jersey and the
Delaware-Maryland-Virginia has begun to push east...and the northern extent looks to clip
especially ack by late this afternoon and evening. Convective
threat is likely to stay just to the S however...since instability
is increases and best Theta-E ridge extends S of the current
frontal position. Will maintain isolated ts in the weather for the time
being...but feel that anything that effects southern New England will
be just a rain shield by the time it arrives.

Will need to watch the development of a weak frontal wave off the
Delaware-Maryland-Virginia likely triggered by scattered convection currently in Maryland
and Delaware...this may be the last threat for rain across
ack/mvy or extreme southern Cape Cod during the overnight hours...will
continue a band of chance...tapering to slight chance probability of precipitation through
about 06 for this threat. After the frontal wave...the cold front
itself should begin a low migration further S.

Aside from this rain threat...drying dewpoints will continue into
tonight as high pressure slowly noses in from the west. The combination
of a remnant cirrus shield from convection to the S is likely to
mitigate radiational cooling expect overnight lows
to be a bit warmer than they otherwise could be. Expect lows
mainly in the upper 50s to middle 60s. A few northwest valleys...away from
the cirrus shield may drop into the low 50s thanks to a better shot
for radiational cooling.


Short term /6 am Friday morning through Friday night/...
with weak frontal wave shifting well to the southeast of New England
early in the morning...expect that cold front will finally begin a
further migration to the S...allowing high pressure to begin to crest
across the region during the day. Aside from some early cirrus from
the wave...clouds will come in the form of diurnal cumulus as models
show a modest moisture layer just above the bl. Models are still
trying to indicate a pocket or two of very light quantitative precipitation forecast thanks to
razor thin cape profile above the mixed layer per latest
soundings. However...agree with previous forecast shift that the
overall column looks much too dry at this time. Therefore...will
continue with none probability of precipitation. Typical middle Summer mixing profiles and 850 mb
temperatures near +13c support highs mainly low-middle 80s /near typical for
this time of year/ except near shorelines where weak pressure gradient
will support sea breeze development.

Tomorrow night...
similar setup to Thursday night as dewpoints fall into the low 50s. expect a bit more clearing and a generally weak pressure
gradient. Therefore...might see a bit more radiational cooling
across the region. Have mins a bit cooler...mainly in the low 50s
to around 60f. Possibly a little warmer in the urban spots.


Long term /Saturday through Thursday/...

* pleasant Summer weekend
* increasing humidity and thunderstorms Sun night through Tuesday
* high pressure returns middle week with quiet weather

Medium range model suite is in fairly good agreement on the synoptic
scale pattern throughout the long term...including the ensembles.
There are of course some mesoscale differences throughout the
forecast but overall feel a blend of available guidance will result
in a reasonable forecast. The main story will be a low/frontal
system in the Great Lakes late in the weekend through early next
week that will bring increasing humidity and a risk for severe
weather as the cold front reaches southern New England Tuesday.
High pressure returns towards the middle of the week with drier
weather expected.

Saturday through Sunday midday...high pressure slowly moves offshore
with seasonable and quiet weather expected.

Sunday midday through Monday...the European model (ecmwf) has a more pronounced cold
front moving through southern New England during this time...while
the European model (ecmwf) ensemble mean and the GFS both indicate perhaps a weak pre-
frontal trough while keeping the main front back across the Great
Lakes and Midwest. Given the wpc preference for the European model (ecmwf) ensembles
and the gefs...will go more with that solution. Regardless...a
period of unsettled weather is likely with showers and thunderstorms

Tuesday...with this run of model guidance Tuesday appears to be the
greatest threat for severe weather. A strong middle level low in the
Great Lakes coupled with a frontal system approaching southern New
England yields an excellent set up for severe weather across the
northeast including damaging winds...large hail...and tornadoes.
This has led the Storm Prediction Center to also indicate the
potential for severe weather across southern New England. At this
point...much depends on the position of the upper jet and the front
and where all this comes together. Pinpointing where these storms
may occur across the northeast is impossible at this time range but
suffice it to say the potential exists for severe weather.

Wednesday and Thursday...low pressure slowly moves into the
Maritimes as the cold front moves offshore. High pressure builds
into southern New England bringing quieter and drier weather.


Aviation /00z 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/...high confidence for most
except ack this evening.

Through tonight...
VFR for most. Only caveat will be ack...where another round of
stratus and low visibilities are possible in fog until late. Also...some
rain possible this evening for ack.

Friday and Friday night... VFR. Sea breezes once again likely at
near shore terminals. Start time is likely 15z-17z.

Kbos taf...high confidence in taf. Sea breeze should start 14-15z

Kbdl taf...high confidence in taf.

Outlook...Saturday through Tuesday...

Saturday and Sunday...high confidence. VFR.

Sunday night through Tuesday...low confidence. Mainly VFR.
MVFR/IFR conditions likely in scattered thunderstorms and rain.


forecaster confidence levels...

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

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

A cold front will slowly move S of the waters early
tomorrow...until then a few pockets of showers...and possibly even
a rumble of thunder is possible mainly on the waters S of Block
Island to Nantucket through the early half of the overnight. Winds
and seas will remain below Small Craft Advisory thresholds through
Friday night. Outside of an isolated ts.

Outlook...Saturday through Tuesday...

Saturday and Sunday...high confidence. Quiet boating weather
expected with seas 2-4 feet and southwesterly winds 10 to 15 kts.

Sunday afternoon through Tuesday...moderate confidence. Increasing
seas through the period on persistent southwesterly flow.
Overall...winds remain below 25 kts. Showers and thunderstorms are
possible at times throughout this period with the strongest storms
expected on Tuesday ahead of a cold front. Heavy rainfall...strong
to damaging winds...and even hail are possible with any
thunderstorms over the waters.


Box watches/warnings/advisories...
New Hampshire...none.
Rhode Island...none.


near term...doody/rlg
short term...doody
long term...rlg

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