Area forecast discussion
National Weather Service Taunton Massachusetts
719 am EDT Friday may 24 2013
Synopsis...
a cold front will move slowly into New England today. A low
pressure will develop on this front...causing the entire system
to linger across the region through this weekend. This will bring
showers and cooler conditions...with a few thunderstorms possible.
Some of the rainfall will be heavy at times. Conditions should
improve Monday. Dry weather and seasonable temperatures are expected into
the middle of next week.
&&
Near term /until 6 PM this evening/...
730 am update...
Have continued the Wind Advisory for the cape and the islands as
gusts are showers are still over this region and with the strong
low level jet right over head...some mixing may occur. Same reason to keep
the short-fuse Gale Warning for the adjacent coastal waters. Rip
current risk still seems on track as we are heading into the
Memorial Day weekend...did continued to highlight the high risk
of rip currents for some exposed south-facing beaches. Have let
the Flood Watch go for areas west and south of the the I-95
cooridor. Although shome showers are passing through...believe
there may be a bigger threat later this afternoon as heavy showers
form along the front...and the threat of convection exists.
Otherwise forecast continues to be on track this morning...have
made some minor updates to account for current trends.
Previous discussion...
Current preference is for a blend of the 24/00z NAM and 24/00z
GFS for the timing and location of the various synoptic features
today into tonight. The GFS solution was slightly faster to move
the upper level components of this system away from southern New
England than the NAM. However...there are details in the NAM
solution which we felt should not be ignored...mainly the banding
and intensity of the rainfall which are tougher for the GFS to
resolve.
Expecting the cold front across eastern New York state and northeast PA
to slowly move into southern New England late tonight into this
morning. This front should continue to move toward the coast
before stalling this evening as a low pressure develops along it.
This front will provide plenty of lift for the abundant moisture
already in place to produce periods of moderate to heavy rainfall.
Convective instability is weak this morning...however the low-
level jet may be enough of a focus to produce a few thunderstorms
today. The main area of concern for that would be Rhode Island and eastern
Massachusetts.
Temperatures were a blend of the mav and met MOS guidance...with
some local bias-corrected guidance thrown in for good measure.
Not expecting a large diurnal range today.
&&
Short term /6 PM this evening through 6 am Saturday/...
a developing low-pressure just east of Massachusetts this evening is not
expected to make much progress away from our region. However...as
this low develops a dry slot is expected to briefly cut back on
the coverage of rainfall toward the East Coast. Main deformation
and frontogenesis zones shift inland as well.
Seasonable temperatures forecast. A blend of the mav/met guidance
handles this well.
&&
Long term /Saturday through Thursday/...
highlights...
* upper level system will keep showers and cooler temperatures for the
weekend.
* Improvements begin on Monday with moderating temperatures through the middle
week.
* Warm front by end of the week will push temperatures well above average.
Confidence level/model guidance...moderate confidence in the
overall forecast. Model guidance has seem to get its act together
and have a better handle on the northern stream shortwave and its
phasing with the upper level trough. Appears that the 00z GFS has
good run to run consistency and is supported by several other
models...including the 00z ec. Have trended the forecast to a
blend of the NAM and GFS and GFS/ec for the extended portion.
Overall have high confidence of rain and cooler temperatures for this
weekend and drying conditions for Monday. Low confidence on exact
timing of precipitation and thunder potential. Moderate confidence for
next week...with dry weather and seasonable temperatures for middle week.
Appears a warm front will try to lift jumping temperatures well above
average...have moderate confidence.
Details...
The weekend...
Precip/qpf...cold and wet Holiday weekend is in store for
southern New England. The only region which may have some hope is
the cape/islands and perhaps eastern mass...where dry air will try
to punch through. Upper level trough will push over the region and
pinwheel over southern New England until Sunday before pushing
northward. Surface low over Cape Cod canal will push eastward of
the North Shore. This may allow for slightly warmer temperatures and
drier conditions for the cape on Saturday as dry air intrusion
will push through as low pressure undergoes cyclogenesis. Appears
that a good wrap around of rain on the back side of the low will
develop over the CT valley and drop over an inch to perhaps 2
inches of precipitation for the weekend in this region...may need to
watch for possible river flooding as there have been several
inches already fallen over the past 24 hours...with more on the way.
Surface low will get pushed more northward into the Gulf of
Maine...this will push precipitation farther east and northward on Sunday
and slowly dissipate from south to north Sunday night. May be a
tad slow on timing of precipitation yet have low confidence on the exact
exit timing.
Thunder...there is a low probability of thunder for Saturday and
into Sunday. However included an isolated chance as total totals
reach above 50 and surface lifted indices do drop to near 0. Appears that the
potential is there especially across the eastern half of the region on
Saturday thanks to the dry air allowing for some diurnal heating
to break through. Do not anticipate anything to be strong or
severe. However with it being a Holiday weekend wanted to focus on
that the potential is there.
Temperatures...as upper level low drops over southern New
England...a cold pool will set up allowing for temperatures to drop well
below average. Expect highs to struggle to reach into the 60s on
Saturday and the middle 60s on Sunday. Lows overnight do get quite
chilly...in the middle to upper 30s.
Monday and Wednesday...
Monday is a transition day from the soggy cool weekend to a
warm...dry mid-week. Upper level low will continue to push off shore
into the Gulf of Maine...allowing for Midwest ridge to build.
Surface high pressure will slide over and help keep a dry forecast
for most of the work week. However cannot rule out a spot shower or
two...especially if sea breezes develops. Temperatures will increase through the
mid-week...with upper 60s for Monday to upper 70s by Wednesday.
Thursday...
mother nature is trying to make up for the cold/rainy weekend by
bring a strong warm front to southern New England by late week.
This warm front will bring muggy conditions and a chance os
isolated showers. However main think to watch is maximum temperatures...which
may reach the middle 80s. Some models even push the region into the
90s. Since this is several days away...keep in mind that mother
nature may change her mind.
&&
Aviation /11z Friday through Tuesday/...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Overview...moderate confidence.
Today...MVFR-IFR ceilings/visibilities continue through the day. Winds shift
to west-northwest across western areas this afternoon...then late today
across the eastern areas. Locally heavy rainfall...mainly this
morning. Low level wind shear likely across cape/islands through midday.
Tonight...expecting some improvement to visibilities overnight...
particularly inland. Not much improvement in ceilings though.
Kbos terminal...moderate confidence...mainly due to timing issues.
Scattered thunderstorms and rain possible. Low level wind shear likely east of the terminal for
approaches over the ocean.
Kbdl terminal...high confidence in trends. Moderate confidence in
timing.
Outlook...Saturday through Tuesday...
The weekend...low to moderate confidence. Very unsettled pattern
with variability between VFR conditions and MVFR/IFR conditions in
shra/tsra/fog. Improving conditions late Sunday night into Monday
morning from south to north.
Monday into Tuesday...high confidence. VFR. Low confidence on sea
breeze development.
&&
Marine...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
High confidence today.
A low-level jet and moderate to heavy rainfall will bring near 25
knots gusts on the waters early this morning. A strong low-level
inversion will limit gusts...so gales not expected. Persistent SW
flow will result in building seas today. Winds will diminish later
today as this low-level jet departs. Expecting low visibilities in fog
and locally heavy showers. Isolated thunderstorms are also
possible.
Tonight...moderate confidence. A low pressure and cold front will
likely stall across the eastern near-shore waters. Wind directions
will be quite different depending upon where this front sets up
exactly. South winds should continue to diminish...before
reintensifying from the north behind this low pressure. Low
probability for thunderstorms. Areas of low visibilities in heavier
showers and patchy fog. Seas will remain 5 feet or higher...mainly
across the open waters.
Outlook...Saturday through Tuesday...
The weekend...upper level system will linger across New England as
surface low stays over the New England waters. Expect seas to remain
high for most of the weekend. Small chance for an isolated T-
storms...but rain/showers will lower visibilities especially on Saturday. Gusty northwest
bring gusts close to gale force Sat into Sat night...have hoisted a
gale watch. Strong Small Craft Advisory will be needed for Sunday.
Monday and Tuesday...moderate confidence. Winds and seas will slowly
diminish.
&&
Hydrology...
based on recent radar data...we are contemplating canceling the
Flash Flood Watch west of the Boston metropolitan area and southeast Massachusetts.
Precipitation is much more broken than previously thought. The
current thinking is there is still some potential for stronger
convection later this afternoon east of the cold front which would
also be closer to better organizing shear. The next shift will
have to reevaluate this potential.
&&
Tides/coastal flooding...
East Coast of Massachusetts this weekend...
astronomical high tides will occur this weekend into early next
week. With a surface low lingering just off the southern New
England East Coast Saturday into Sunday...expecting gusty
northerly to northwest winds especially during the daytimes hours.
At Boston...a high tide of 11.9ft will occur tonight at 11:21 PM
and 12.2 feet early Sunday morning at 12:12 am. Expecting light
southerly winds during today/S daytime high tide...so this is less
of a concern. Looking at the Sunday morning high tide...northerly
to northwesterly winds may help increase the surge especially for
Cape Cod Bay. Right now only expecting minor splashover across
north-facing beaches. Will need to continue to monitor and update
with the latest forecast guidance.
&&
Box watches/warnings/advisories...
CT...none.
Massachusetts...Flash Flood Watch until noon EDT today for maz013-015>021.
Wind Advisory until 9 am EDT this morning for maz022>024.
New Hampshire...none.
Rhode Island...Flash Flood Watch until noon EDT today for riz005-007.
Marine...Gale Warning until 10 am EDT this morning for anz231>234-250-
251-254-255.
Gale watch from Saturday afternoon through Sunday morning for
anz235-237-255-256.
Small Craft Advisory until 2 PM EDT Saturday for anz235-237-
256.
&&
$$
Synopsis...Belk/dunten
near term...Belk/dunten
short term...Belk
long term...dunten
aviation...Belk/dunten
marine...Belk/dunten
hydrology...
tides/coastal flooding...
