Area forecast discussion
National Weather Service Taunton Massachusetts
1020 PM EDT Monday Jun 17 2013
Synopsis...
A slow moving cold front will bring scattered showers and
thunderstorms this evening. Another round of showers/thunderstorms
are anticipated Tuesday afternoon/evening. Large high pressure
will bring mainly dry and seasonable conditions Wednesday through
Friday...then will anchor south of New England Saturday. An
approaching warm front may bring widely scattered showers and
thunderstorms next weekend.
&&
Near term /until 6 am Tuesday morning/...
1030 PM update...
Diffuse cold front lingers across central and western New England
from an area of low pressure over northern Maine. Some renewed
activity along the front over the lower Hudson Valley...but while
the 0z Chatham sounding exhibits the potential threat of elevated
thunderstorms...the broader synoptic environment while cyclonic
contains little lift. Not seeing any indications of enhanced
ascent per middle-level energy...nor support from upper-level jet
dynamics. Quiet and dry forecast into morning...perhaps an
isolated shower to cover the bases.
So attention turns to other potential threats...namely low clouds
and fog.
11-3.9 satellite shows a low cloud deck offshore of New England...
difficult to discern with obscuring middle-high cloud. Hrrr/RUC has
done very well this evening with handling earlier thunderstorm
remnants. Model forecast solutions suggest the low clouds drifting
into New England along the near-shore towards morning...and will
follow suit accordingly. Low stratus along the near-shore.
Also...am concerned over the antecedent rains and high dewpoints
setting the stage for fog development as temperatures drop...best
chances along the shores. While the hrrr/RUC does not feel this to
be the case...will keep fog in the forecast.
Temperatures and dewpoints remain on track. Looks to remain mild
overnight...but temperatures lowering to the dewpoint allowing for
fog development.
&&
Short term /6 am Tuesday morning through Tuesday night/...
Tuesday and Tuesday night...
another rather tricky forecast across southern New England. The
bulk of Tuesday morning will probably be dry. However...another
shortwave will be approaching from the west. This should allow
showers and thunderstorms to overspread the region from the west
during the afternoon. Based on the model consensus...have enough
confidence to run with likely probability of precipitation across most of the region.
As for severe weather potential...instability might be limited
depending on the amount of cloud cover and position of the front.
However...there will be another day of 0 to 6 km shear values on the
order of 40 to 50 knots. Therefore...we can/T rule out a few
strong to severe thunderstorms with the best chance south of the
Massachusetts Turnpike. The bigger concern may be with heavy rain and
localized flooding...as precipitable water values will still be on the order of
1.5 inches.
The bulk of the showers and thunderstorms should come to an end
sometime Tuesday evening. However...a few showers may linger into
the overnight hours especially along the coastal plain.
&&
Long term /Wednesday through Monday/...
Big picture/preferences...
Upper trough moves across New England Wednesday with a small amount
of cold advection aloft. Building heights Thursday as high pressure
over the plains edges east. Even with the building heights...a
couple of shortwaves sweep around baffin island upper low and across
Quebec/northern New England
toward the weekend.
The dailies...
Wednesday-Thursday...cold front moves offshore early Wednesday.
Southern New England remains in the right entrance region of the
upper jet...and 70 percent relative humidity lingers at 800-850 mb through the
afternoon. So potential exists for diurnal cumulus during maximum
heating. For this reason we have 40-60 percent sky cover during the
afternoon.
Otherwise dry weather as surface high pressure builds over the
region...then moves offshore during Thursday. This will bring light
northeast flow Wednesday and a developing southwest flow Thursday.
Mixing depths will reach 800 mb Wednesday and 800-850 mb Thursday.
Mixing the temperatures at the top of these layers will support middle 70s to
lower 80s...although the northeast wind Wednesday may buffer any
mixing in eastern mass and hold temperatures there a few degrees cooler.
Friday through Monday...due to the ongoing Severe Thunderstorm
Watch...forecast grids for Friday through Monday remain unchanged.
Previous discussion...
Friday...mainly dry and seasonable conditions expected to
continue with high pressure in control. Temperatures mostly in the 70s...with
cooling seabreezes expected each day with light boundary layer
flow.
Saturday and Sunday...
forecast confidence decreases as GFS/European model (ecmwf) differ on eastward extent of
warm sector airmass. As mentioned above we leaned toward the European model (ecmwf)
which keeps the warm front to the west with increasing chance of
showers/thunderstorms from possible mesoscale convective system...but still a lot of uncertainty.
Temperature forecast also uncertain and will depend on position of warm
front. We undercut mex guidance by several degrees more in line
with European model (ecmwf).
&&
Aviation /02z Tuesday through Saturday/...
Forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Overview...moderate to high confidence in tafs through Tuesday
night.
Tonight...
the last of the showers and isolated thunderstorms will push off the
southeast New England coast by late evening. Otherwise...mainly
VFR conditions this evening will probably give way to localized
MVFR-IFR conditions in patchy ground fog late.
Tuesday and Tuesday night...
any patchy ground fog should burn off by middle morning. However...
another round of showers/thunderstorms anticipated Tuesday
afternoon will bring a period of MVFR-IFR conditions. The bulk of
the activity ends sometime Tuesday evening...but IFR to MVFR
conditions may develop late in low clouds and patchy ground fog.
Kbos terminal...moderate to high confidence in tafs. Additional
showers/storms possible Tuesday afternoon.
Kbdl terminal...moderate to high confidence in tafs. Additional
showers/storms possible Tuesday afternoon.
Outlook...Wednesday through Friday...
Wednesday through Friday...high confidence. VFR.
&&
Marine...
Forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
High confidence through Tuesday night.
Lingering swell of around 5 feet across the southern Atlantic waters
should diminish this evening. Otherwise...winds and seas should
be below Small Craft Advisory thresholds through Tuesday night.
The main concern will be for a few strong to severe thunderstorms
this evening...especially across the eastern Atlantic waters to the
north of Plymouth Massachusetts. Another round of showers and thunderstorms
may affect some of our coastal waters Tuesday afternoon and night.
Outlook...Wednesday through Friday...
High confidence.
Wednesday-Thursday...lingering 5 foot seas on the southern outer
waters Wednesday but subsiding during the day. Winds remain
below 20 knots.
Friday...winds and seas below small craft criteria. NE winds may
gust to 20 knots Wednesday.
&&
Hydrology...
Rivers continue to recede across the region...with most falling
below flood stage yesterday and overnight. Only the Charles River at
Dover remains in minor flood. Latest guidance indicates that this
river will only slowly fall and remain in minor flood into
Wednesday morning.
The main concern will be locally heavy rainfall/poor drainage street
flooding from convection this evening and again Tuesday afternoon/
evening. However...given river levels are quite high will have to
keep an eye on some of them especially the smaller streams.
&&
Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory until 5 am EDT Tuesday for anz254>256.
&&
$$
Synopsis...wtb/Frank
near term...sipprell
short term...Frank
long term...wtb
aviation...wtb/Frank
marine...wtb/Frank
hydrology...weather forecast office box staff
