Area forecast discussion
National Weather Service Taunton Massachusetts
610 PM EDT Tuesday Jun 18 2013
Synopsis...
showers and thunderstorms continue through this evening as a cold
front moves across the region. Large high pressure will
follow...bringing mainly dry and seasonable conditions Wednesday
through Saturday. Warmer and more humid weather is expected this
weekend as high pressure anchors just south of New England. Showers
and thunderstorms possible Saturday.
&&
Near term /until 6 am Wednesday morning/...
615 PM update...have updated the Flash Flood Watch...dropping
Hartford County in Connecticut and all of Massachusetts except
Plymouth and Bristol counties. Showers and thunderstorms have
moved out of these areas...or diminished in intensity. Flooding in
these areas has diminished as well.
Thunderstorms will heavy rainfall and localized flooding will
continue into this evening...
Line of showers/scattered thunderstorms moving slowly but steadily S across east
Massachusetts/north Rhode Island/southeast Massachusetts at 20z as seen on kbox 88d radar. Have had several
reports of flash flooding...as well as reports of up to 2 inches
of rain in 90 minutes or less.
Noting another area of rainfall moving across north New Jersey/western Long
Island...which will keep rainfall through this evening across NE
CT/RI/se Massachusetts as low pressure moves along the front as it pushes
offshore this evening. Pretty light pressure gradient except in thunderstorms
where gusts up to 25 knots possible.
Expect any thunder to end by around midnight as the low passes S
of Nantucket...but showers could linger on the cape and islands
through the night. May also see patchy fog develop prior to the
drier air working in...but should improve from S-north as dewpoints drop.
Will be a chilly night across interior S New Hampshire and north Massachusetts as temperatures fall
back to the upper 40s to around 50...ranging to the middle 50s along
the S coast.
&&
Short term /6 am Wednesday morning through Wednesday night/...
tonight...
The cold front will slow as it pushes offshore as a weak wave lifts
along the front from the mid-Atlantic. Expecting widespread rain
with embedded heavier showers and thunderstorms to linger over the
South Coast and adjacent waters. Concerns will still be present for
localized urban flooding and ponding of water along roadways...but
low confidence on severe weather threats as instability is expected
to be minimal. Lows down to around low 50s.
Wednesday...
Cooler airmass building south should allow significant boundary
layer mixing of around 4-6 kft. Subsequently...anticipating the mix-
down of faster momentum and drier air. Not looking at any fire
weather headlines with recent rains. Dewpoints down to around 50
degrees...some gusty northerly winds mainly across eastern New
England. Expecting diurnal scattered to broken fair-weather cumulus
across interior New England.
&&
Long term /Thursday through Tuesday/...
highlights...
* high pressure will lead to quiet weather Thursday and Friday
* high pressure S of southern New England brings warm...humid conditions this weekend
* showers and thunderstorms possible Saturday
There is good general agreement amongst the models through much of
the long term. There are some model discrepancies regarding the
strength and extent of an upper level ridge over the eastern U.S.
Through this weekend. Ultimately this will affect the weather in
this area mainly in where and when showers and thunderstorms are
able to develop. The consensus is with the European model (ecmwf) and the upper
level ridge over the southeast Continental U.S. Thursday and gradually building
northward into the Ohio Valley by Saturday and into the NE Continental U.S.
Sunday and sinking back south early next week. Otherwise...am
expecting fairly quiet weather with more Summer like temperatures
and a few humid days thrown in there as well. With thunderstorms
currently moving over southern New England...will make whatever
changes are necessary and base much of the forecast off the previous
forecast.
Thursday and Friday...high pressure crests over southern New England
with a warming trend in temperatures.
Saturday...best chance for showers and thunderstorms as warm...moist
air builds into the region on SW winds. We will still be on the
periphery of the ridge with decent instability noted in steep middle
level lapse rates.
Sunday through Tuesday...high pressure moves offshore as the upper ridge
sinks S slowly. Warm...moist air remains in the region on
southwesterly winds...and increases instability. However...not much
of a trigger any of those days and models are not showing much...if
any...quantitative precipitation forecast so will keep thunderstorm chances low.
&&
Aviation /22z Tuesday through Sunday/...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Near term /through Wednesday night/...
Moderate confidence for trends...lower confidence for timing
through tonight...then moderate confidence Wednesday-Wednesday night.
Through 00z...MVFR-IFR ceilings/visibilities in showers/scattered thunderstorms across east
Massachusetts/north Rhode Island/north CT as cold front moves slowly S. Noting brief
torrential rainfall in some storms. May see local LIFR conditions.
This will shift slowly S to the S coast this evening. Will also
see local IFR-LIFR ceilings/visibilities along S coast with low
clouds/patchy fog.
Tonight...expect mainly VFR conditions across north Massachusetts/S New Hampshire...patchy
MVFR-IFR ceilings/visibilities mainly in the valleys with patchy fog. Across
central and southern areas...MVFR-IFR ceilings/visibilities in low
clouds/showers. May see scattered thunderstorms through midnight. Brief LIFR
conditions possible.
Wednesday...MVFR-IFR ceilings/visibilities to start mainly S of the Mass
Pike...then improving to VFR during the morning. MVFR visibilities may
linger along S coast into the afternoon.
Wednesday night...VFR.
Kbos terminal...moderate confidence. Ra+/thunderstorms and rain possible from around
21z through 02z.
Kbdl terminal...moderate confidence. Ra+/thunderstorms and rain possible through
23z-00z.
Outlook...Thursday through Sunday...
Thursday and Friday...high confidence. VFR.
Saturday...moderate confidence. Mainly VFR. Low probability of
showers and thunderstorms briefly lowering conditions to MVFR/IFR.
Sunday...moderate to high confidence. VFR.
&&
Marine...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Near term /through Wednesday night/...moderate confidence.
Tonight...winds shift to NE as cold front moves offshore...then
low pressure passes S of the waters. NE winds increase...gusting to 25
knots toward daybreak across the southern outer waters and east of Cape
Cod with seas up to 5 feet. Low probability of thunderstorms this evening.
Wednesday...NE winds gusting to 25 knots through midday on the outer
waters from Cape Cod southward. May also see gusts up to 25 knots on
Nantucket Sound and Buzzards Bay mainly during the morning...so
have put up small crafts there. Seas up to 5 feet...but should
subside by evening.
Wednesday night...winds and seas below small craft criteria.
Outlook...Thursday through Sunday...
High confidence.
Quiet boating weather expected through Sunday with high pressure
near or over the waters. The only exception is Saturday when
showers and thunderstorms may limit visibilities on the waters.
&&
Hydrology...
have kept Flash Flood Watch up through this evening across the
region...though may end it early across lower CT valley region.
Have had several reports of flash flooding due to torrential rains
from thunderstorms as the cold front slowly moves through. Have also
received a couple of reports of small streams overflowing their
banks.
As for river flooding...the Charles at Dover remains just above
flood stage. Latest guidance indicates that this river will only
slowly fall and remain in minor flood through late Wednesday night.
&&
Box watches/warnings/advisories...
CT...Flash Flood Watch until 9 PM EDT this evening for ctz003-004.
Massachusetts...Flash Flood Watch until 9 PM EDT this evening for maz017>021.
New Hampshire...none.
Rhode Island...Flash Flood Watch until 9 PM EDT this evening for riz001>007.
Marine...Small Craft Advisory from 6 am to noon EDT Wednesday for
anz232-234.
Small Craft Advisory from 4 am to 6 PM EDT Wednesday for
anz254>256.
&&
$$
Synopsis...rlg/evt
near term...Frank/rlg/evt
short term...evt
long term...rlg
aviation...rlg/evt
marine...rlg/evt
hydrology...
