Area forecast discussion
National Weather Service Taunton Massachusetts
437 am EDT sun may 19 2013
Synopsis...
high pressure will move offshore today. A warm front will bring a
few showers to the region tonight as it crosses the area. The
front is expected to stall over central New England Monday. A back
door cold front will bring a dry and less humid air mass into most
of southern New England Tuesday before retreating back as a warm front
on Wednesday. Scattered showers and possible thunderstorms are
anticipated Tuesday afternoon in the Connecticut River valley and over
most of southern New England Wednesday and Thursday. A cooler and
less humid air mass is expected for the coming weekend.
&&
Near term /until 6 PM this evening/...
320 am update...
Plenty of middle/high clouds across southern New England this morning
but low cloud deck over coastal ME/New Hampshire pushed back into
Manchester...Lawrence and Beverly. High res models indicate that
is about as far S as it will get before it begins to push
offshore by middle morning.
Still not seeing much in way of showers to our SW as activity over
New Jersey is pivoting offshore. High res models are insistent we will
see development into Hudson Valley and CT before daybreak.
Rap/hrrr bring showers to CT valley by 8 am and to rest of area
before noon. Not seeing much support for that to occur based upon
radar mosaic so we continued with slower trend shown by 00z NAM...
namely any showers hold off until this afternoon. Any rainfall is
expected to be light.
Temperatures are a challenge today with varying amounts of cloud cover.
Should be able to warm quickly this morning before skies cloud
over areawide this afternoon. We will continue to show warmest
temperatures across Rhode Island/eastern Massachusetts /upper 60s/ and used a NAM/GFS MOS
blend as confidence is moderate at best.
&&
Short term /6 PM this evening through 6 PM Monday/...
warm front lifts through region tonight accompanied by few showers.
Dynamics are not overly strong as main forcing mechanism appears
to be middle level warm advection...especially across CT/RI/se Massachusetts
where we expect greatest coverage. Models do show marginal
instability and meager cape so included isolated thunder...again
mainly for locations closer to S coast. Higher dewpoint air on
S/SW winds should promote patchy fog formation.
Although front remains to our north Monday...cross sections show plenty
of lower level moisture which means cloud cover will be tough to
break...especially near S coast where SW flow will maintain deeper
marine layer. Models differ in coverage and timing of
precipitation...but it appears we will see at least scattered
showers/isolated thunder across interior throughout day.
Expect warmer/more humid day but not quite sure we can reach
lower 80s as indicated by GFS MOS. Toned back a bit by blending
NAM MOS and 2m temperatures which yields highs in middle-upper 70s
except 60s around Cape Cod/islands with onshore flow.
&&
Long term /Monday night through Saturday/...
highlights...
Highlights...
* backdoor cold front will reduce humidity and chance for showers/thunderstorms
east of the CT River Valley on Tuesday
* warm and humid with scattered showers and possible thunderstorms Wednesday afternoon
through at least Thursday night
* cooler and drier air expected for the coming weekend
Medium range models paint a consistent synoptic scale picture for
Tuesday through Thursday but still difficult to resolve timing and
distribution of short wave energy. Both 00z GFS and 00z European model (ecmwf)
models suggest a backdoor intrusion of dry air on Tuesday into Wednesday
morning through all except possibly the CT River Valley. The front
lifts back NE during Wednesday afternoon. Thus for Tuesday will relegate
chance showers/thunderstorms just to SW zones. Then the European model (ecmwf) and GFS
operational runs and the prior run ensembles diverge on character
of eastern trough that will flush out the air mass late in the week.
The European model (ecmwf) has been consistently showing a consolidated northern
stream trough driving a cold front through Thursday night/early Friday morning.
The GFS operational run and ensemble mean keep a notable chunk of
energy south of the main stream northern flow and results in the
spin up of a surface low off the middle Atlantic coast and wet day for much
of the forecast area on Friday.
Tue-Wed...will indicate scattered showers and widely scattered thunderstorms during
this period with highest probability of precipitation during the diurnally favored
afternoon/evening period and SW of a een-orh-ewb line given the
potential for a backdoor air mass to ease into our NE zones.
The trend for both the GFS and European model (ecmwf) models to bring a backdoor
intrusion of dry air into the region on Tuesday lends greater
confidence that any shower activity Tuesday will likely be restricted
to the CT River Valley area. Have also lowered dewpoints. Onshore
flow will keep temperatures cooler along the East Coast. Thus for eastern Massachusetts
and Rhode Island Tuesday no longer looks to be a warm and humid day.
Wednesday...the warm and humid air mass advances back NE and so does
the risk of scattered showers and widely scattered thunderstorms in the afternoon and
early evening.
Thursday...relatively strong short wave trough and cold front will be
approaching from the west late in the day. Anticipating relatively
unstable air mass and increasing vertical shear Thursday afternoon and
evening. It is possible that we may experience a few strong/severe
thunderstorms late Thursday afternoon and evening...most likely western half of
area given the timing of the short wave and front. Raised probability of precipitation to
high chance late Thursday and Thursday night.
Friday...have relatively low confidence for this day due to model
disparity in handling the configuration of the eastern trough
energy. For now...plan to have showers into at least Friday morning
for most locations and perhaps have a chance of showers that
persist over the southeast zones...or at least the cape and islands...to
persist to at least Friday evening. In essence am leaning toward
European model (ecmwf) solution which has remained relatively consistent and seems
to be favored by wpc. The GFS has...however...been fairly
consistent in its solution and the operational run is supported by
its ensembles so cannot completely rule that out. If indeed a
surface low were to develop as advertised by the GFS...we could
see winds approaching marginal gales on the water and a risk for
some coastal flooding with the late Friday evening high tide...which
is quite high astronomically to begin with. That does not seem to
be the most likely solution at this time but will need to keep an
eye on it.
Sat...moderate to high confidence of a cool dry air mass
dominating the region.
&&
Aviation /09z Sunday through Thursday/...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Overview...high confidence.
IFR ceilings along ME/New Hampshire coast and into mht/lwm are not expected to
drop much farther S early this morning...and should erode toward
daybreak as this deck of low ceilings begins to push offshore.
Otherwise VFR ceilings at or above 080 expected this morning...before slowly
lowering to MVFR this afternoon from SW to NE.
S/SW gradient remains weak but sea breezes should be limited to S
coast today. Does not appear favorable along east Massachusetts coast but if it
were to occur it would be early this afternoon.
Fairly confident on period of showers late this afternoon baf/bdl
which shifts to Rhode Island/Massachusetts coasts this evening. Showers will be most
numerous near S coast tonight...where isolated thunder is also
possible.
Although showers exit before daybreak...additional showers/
thunder may redevelop during day Tuesday as warm front lifts to our north.
Appears coverage will be scattered at best...with interior
southern New England having best chance.
Kbos terminal...high confidence in taf. IFR ceilings expected to
remain north of Airport /lwm-bvy/ early this morning and included
few008 as a heads up. Not confident sea breeze will occur but if
it does it would be 16z-19z.
Kbdl terminal...moderate confidence in taf. MVFR ceilings possible
prior to 12z but not confident it will occur given higher ceilings
across NYC metros.
Outlook...Tuesday through Thursday...
Moderate confidence through the period.
Tuesday...scattered MVFR ceilings/visibilities in scattered showers and isolated thunderstorms CT
valley...VFR elsewhere.
Wednesday...areas of MVFR ceilings/visibilities in scattered showers and widely scattered
thunderstorms.
Thursday...MVFR ceilings/visibilities with fog and stratus in the morning
and then again in the afternoon with scattered showers and thunderstorms.
Possibly a few strong thunderstorms late Thursday afternoon/evening.
&&
Marine...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
High confidence through Monday.
High pressure moving offshore will maintain light winds/flat seas
today. Could see few light showers later this afternoon as warm
front approaches.
Increasing S/SW flow develops tonight and Monday as warm front lifts
into central New England. This will bring slowly building seas to
outer waters where current Small Craft Advisory has been extended into Monday. Added
Rhode Island/block is sounds to Small Craft Advisory as well...and Buzzards Bay/Vineyard
Sound where SW winds will create steep waves during times of
departing tide /high tide 355 am and 437 PM Monday at New Bedford/.
Should also see period of showers/isolated thunder tonight and
more widely scattered activity Monday. Patchy dense fog probable
around Cape Cod and islands.
Outlook...Monday night through Thursday...
Moderate confidence through the period.
A left over swell at or a little above 7 feet likely Tuesday...subsiding
Wednesday. Building seas likely Thursday as SW flow strengthens. Areas of
fog likely Wednesday night through Thursday. Winds may approach Small Craft Advisory levels late
Thursday and Thursday night.
&&
Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory for hazardous seas from 6 am to 7 PM EDT
Monday for anz233>235-237.
Small Craft Advisory for hazardous seas from 4 am to 7 PM EDT
Monday for anz254-255.
Small Craft Advisory for hazardous seas from midnight tonight
to 7 PM EDT Monday for anz256.
&&
$$
Synopsis...jwd/Thompson
near term...jwd
short term...jwd
long term...Thompson
aviation...jwd/Thompson
marine...jwd/Thompson
