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Area forecast discussion 
National Weather Service Taunton Massachusetts
900 am EDT Sat Jul 12 2014

dry and beautiful Summer weather continues today. Breezy and
turning more humid Sunday along with a chance of showers and
thunderstorms across western New England late in the day. Becoming
unsettled early next week with periods of showers and
thunderstorms. Some of the storms may be strong along with
localized flash flooding. A trend toward drier and less humid
weather follows middle to late next week.


Near term /until 7 PM this evening/...

9 am update...

A beautiful day in progress with sunny skies at middle morning. Some
scattered diurnal cumulus will develop this afternoon particularly
across the interior...but still plenty of sunshine expected. Not
enough moisture/forcing for any precipitation this
will continue with a dry forecast. High pressure will slowly move
off the coast...allowing for readings a few degrees warmer than
yesterday. Afternoon high temperatures will mainly be in the middle to
upper 80s...except a few degrees cooler across some locales on the
immediate coast with sea breezes developing. Humidity levels will
remain comfortable for July standards.


Short term /7 PM this evening through 6 PM Sunday/...

A few spotty showers may spark by the evening hours especially across the
Berks where a thin line of instability may develop. However because
of the low probability remained a dry forecast.

High pressure will continue to move eastward out towards Georges
Bank late tonight allowing for return flow. Low level moisture will
increase allowing for the potential for fog to develop overnight.
Otherwise anticipate a dry night as the better forcing and lift for
any showers is to far west.

Astronomical high tide will occur tonight allowing for the
possibility of minor splashover across east facing beaches on the
mass coastline.


Upper level trough will begin to swing its way towards the eastern
half of the region. A weak wave will move through the flow sparking
of some showers and thunderstorms...especially across upstate New
York. Still plenty of dry air aloft over southern New England on
Sunday so believe that much of the region should remain dry minus
the western zones. Precipitable waters are increasing close to 2 inches and with
850mb low level jet increasing...could see some heavy rainfall out of any
thunderstorms that develop. Especially west of the central hills...cape
values are increasing to 1000 j/kg and 0-6 km shear values around
325-30 kts may allow for some gusty winds as well as the heavy
rainfall potential. Believe areal coverage will be isolated by the
late morning/early afternoon...but increase into the evening hours
and shortwave approaches southern New England.

Soundings suggest that mixing up to 850 mb will occur which would
allow for temperatures to warm up to the mit to upper 80s. With the
increase in 850 mb winds...expect gusty winds between 20-30 miles per hour on
Sunday. Dewpoints will also be on the increase which will allow for
the return of that summertime mugginess.


Long term /Sunday night through Friday/...

* showers and thunderstorms likely Sun night through Tuesday with
strong storms possible along with a threat for flash flooding
* drier and less humid weather returns Thursday and Friday.

Synoptic overview and guidance evaluation...

Ensembles and deterministic guidance continue to show good
continuity on an evolving highly amplified pattern across North
America beginning this weekend and continuing into next week. The
long wave pattern will feature two high amplitude
across western Canada attaining heights + 3 South Dakota. The other ridge will
be located over the northwest Atlantic. Between these two ridges an
anomalous closed low dives southward into the Great Lakes with
heights reaching -3 South Dakota Tuesday over the Ohio Valley. This high amplitude
meridional flow will be accompanied by a strong frontal zone with
tropical moisture to the east and a Spring-like cool airmass to
the west. This frontal zone will also be accompanied by strong jet
dynamics...yielding a risk for strong to severe thunderstorms Monday and Tuesday
along with a threat for flash flooding.

00z gefs ensembles and its operational 00z GFS are more progressive
with the upper trough and frontal passage than the 12z ecens
ensembles and new 00z European model (ecmwf). These are typical model biases we see
with frontal passages... European model (ecmwf)/ecens slower than GFS/gefs. Given the
time range here best course of action is to follow a model blend to
minimize model biases. Although would not be surprised to see the
slower European model (ecmwf)/ecens solutions verify given the high amplitude
meridional flow.

Daily details...

Sunday night...a mild night as warm sector overspreads southern New
England. Risk of scattered showers/thunderstorms as well.

Monday...lead short wave trough and attending prefrontal trough
should be sufficient to trigger scattered showers/T-storms across
the region with a more of a focus over western New England given
proximity to trough. Precipitable waters + 2 South Dakota combined with at least modest
instability of 1000-1500 ml convective available potential energy support T-storms with potential
heavy rain and wind. Warm and muggy conditions as well.

Tuesday...timing differences here regarding arrival of trailing
short wave trough and attending surface cold front. GFS and its
ensembles faster than the European model (ecmwf) and ecens. Nevertheless stronger jet
dynamics with this trailing short wave trough as gefs anomalies
suggest 250 mb jet reaching + 3 South Dakota over New York state with rrq across
southern New England. This will provide strong qg forcing. These
synoptic scale features combined with model quantitative precipitation forecast signal heavy
rainfall potential with new 00z European model (ecmwf) storm total of 1-3" across the
region...heaviest amounts western CT/MA. 00z GFS not far behind with
up to 2.5" across the Berkshires. The more progressive 00z gefs
indicate areas of low probability of 2-3" rains from New Jersey northeast to
downeast ME. Thus a moderate risk of heavy rain and localized
flooding here Monday and Tuesday. Warm and muggy conditions continue as

Wednesday...lots of uncertainty here given model spread on timing of
frontal passage. A model blend suggest this will be our transition
day with a risk of showers/T-storms across eastern Massachusetts and Rhode Island early
in the day...followed by a trend toward drier/less humid conditions
from west to east as frontal passage works across the region.

Thursday and Friday...mid/upper level trough remains west of New
England Thursday however the upper air pattern begins to deamplify as
short wave trough lifts northeast into southeast Canada Friday. Overall
this supports a trend toward drier and less humid weather for
southern New England.


Aviation /12z Saturday through Wednesday/...
forecaster confidence levels...

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

Short term /through Sunday/...high confidence.

7 am change from 06z tafs. Earlier discussion below.


Today and tonight...VFR other than perhaps a touch of late
night/early morning patchy ground fog in the typically prone
locations. Sea breezes on both coastlines.

Sunday...VFR to start. MVFR ceilings possible in shower and thunderstorm
develop by late Sunday afternoon especially across western sites.

Kbos taf...high confidence in taf. Easterly sea breeze develops
around 14-15z.

Kbdl taf...high confidence in taf.

Outlook...Sunday night through Wednesday...

Moderate to high confidence on MVFR/IFR at night in areas of fog
along with scattered showers/tstms. Conditions may improve to low
end VFR during the afternoon hours. However risk of showers/thunderstorms
increase during this time. Low probability of some improvement Wednesday
from west to east.


forecaster confidence levels...

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

Short term /today through Sunday/...high confidence.

Nice boating weather through tonight. Weak pressure gradient
will keep winds/seas below Small Craft Advisory thresholds. Variable winds this
morning will become southerly at 5 to 15 knots as high pressure
moves off the coast. Winds will then become south southwest at the
same speeds by tonight. Pressure gradient increases on Sunday
allowing for winds across the waters to increase to 20 kts. Expect
near shore waters to gust closer to 30 kts. Small Craft Advisory may be needed.

Outlook...Sunday night through Wednesday...

Moderate to high confidence on modest south-southwest winds 15-20 knots with gusts
up to 25 possible. Visibility lowering at times in areas of fog along with
tropical downpours Sun night through Tuesday. Some improvement possible Wednesday
as frontal passage may sweep across the waters.


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


near term...dunten/nocera
short term...dunten
long term...nocera

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