Area forecast discussion
National Weather Service Taunton Massachusetts
411 PM EDT Thursday may 23 2013
Synopsis...
a cold front will move slowly into New England Friday as low pressure
lingers over the region through the weekend. This will bring
showery and much cooler weather...with improvement on Monday.
Seasonable temperatures and dry weather for the middle week.
&&
Near term /until 6 am Friday morning/...
numerous showers and isolated thunderstorms with locally heavy rainfall
moving NE across western new eng. Environment is marginally
unstable with MLCAPES around 500 j/kg while middle level lapse rates
are less than 6 c/km. Instability is a limiting factor for severe weather
despite 30-40 knots 0-6km shear. Near term forecast of significant
severe parameter also supports limited severe potential. Still cant
rule out an isolated severe storm...but heavy rainfall is primary
concern into this evening across the interior with precipitable waters near
1.7".
Tonight...cold front moves slowly east from central New York and
will approach western new eng toward daybreak as middle level trough
amplifies over the Great Lakes. Southern New England will be under the right entrance
region of the upper jet which will provide good forcing acting on
high precipitable water airmass to bring locally heavy rainfall to southern New England. Showers
and isolated thunderstorms will be ongoing across the interior in the
evening...then focus will shift to the coastal plain after
midnight as low level jet strengthens across southeast new eng.
Instability will be weakening overnight and even elevated
instability parameters are marginal. Still cant rule out isolated
thunderstorms given deep synoptic forcing...but lack of instability
should limit rainfall rates. Areas of urban and poor drainage
flooding likely overnight in eastern new eng.
&&
Short term /6 am Friday morning through 6 PM Friday/...
high amplitude trough forecast to close off over the middle Atlantic
region on Friday with southerly flow aloft. Surface low develops on
the front which will slow its eastward progress across southern New England. Low level
jet will be situated just east of Cape Cod in the morning with axis
of heavy rainfall confined to the cape/islands...before moving east
in the afternoon. However...showers will persist all day across
much of the region with deep moisture axis in place and surface wave
moving along frontal boundary. In fact...this has a winter look
to it with decent low level frontogenesis and deformation axis
setting up across western new eng northwest of surface low. Temperatures will
likely fall into the 50s over northwest higher terrain as front moves to
the east...but should reach well into 60s to around 70 across southeast
new eng which will remain east of the boundary for most of the day.
The front should reach the i95 corridor by late afternoon.
&&
Long term /Friday night through Thursday/...
highlights...
* wobbly upper level low will keep showers and cooler temperatures for the
weekend.
* Improvements begin on Monday...with dry weather and seasonable temperatures.
* Temperature improvement by the mid-week.
Confidence level/model guidance...low confidence in model
performance...but moderate confidence in the forecast. The
models/ensembles show an upper trough with an embedded closed low
across New England over the weekend. This system will wobble over
the region until pushing out by early next week thanks to ridging
across the Midwest. Have high confidence that a cooler weekend is
in store with moderate confidence on precipitation timing and placement.
Believe Monday will dry out the region with a mainly dry forecast
for the mid-week. Models indicate a warming trend by late week
with temperatures above 80f.
Details...
The weekend...looks like cloudy skies...showers and cool temperatures
are in store for the Holiday weekend. Models continue to slow down
the timing of the elongated trough with an embedded cut off low.
Expect the low to linger across New England before pushing out by
Monday. This low will bring a cold pool over the region allowing
for temperatures to struggle to get into the 60s. Breezy northwest winds
wont help much either. Models are indicating some sort of trowal
feature from the cut off lows cyclogenesis. Still too hard to
pinpoint but believe that areas across the CT valley have the best
potential to see the heaviest precipitation with quantitative precipitation forecast values ranging up to
an 1.5 to 2 inches total for the weekend. Since this particular
region has had several round of convection in the past few
days...and with more on the way...may need to watch for potential
flooding amongst the rivers and low lying areas. Precipitation should
begin to lift Sunday night/early Monday morning. Kept any
indication of thunder out of the grids for this time period as
there if very low instability and cloud cover will limit diurnal
heating. Heavy downpours will be the main threat as precipitable water values
will reach up to an inch.
Monday and beyond...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.
&&
Aviation /19z Thursday through Tuesday/...
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Overview...moderate confidence.
Variable MVFR/IFR ceilings this afternoon will trend to widespread
IFR/LIFR tonight into Friday with areas of fog developing. Showers
and scattered thunderstorms CT valley and western new eng this afternoon will
expand east across rest of southern New England tonight into Friday...with focus for
heavy rainfall shifting to the coastal plain late tonight and Friday
morning. Localized low level wind shear possible late tonight cape/islands as low level jet
strengthens across the region.
Kbos terminal...moderate confidence. Expect lowering ceilings to IFR
tonight with showers increasing. Scattered thunderstorms possible.
Kbdl terminal...high confidence. Widespread showers and a few
thunderstorms this afternoon and evening.
Outlook...Friday night through Monday...
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 Thursday...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 through Friday.
Low level jet will bring near Small Craft Advisory gusts on the waters through
tonight...diminishing west of the canal later tonight as the low level jet
moves to the east. Strong low level inversion will limit gusts so
gales not expected. Persistent SW flow will result in building
seas through Friday. Winds will diminish on Friday as the low level jet
moves east of the waters. Expect low visibilities in fog and locally heavy
showers. Isolated thunderstorms are also possible.
Outlook...Friday night through Monday...
The weekend...cold front will linger across the waters as surface
low stays over New England. Expect seas to remain above Small Craft Advisory for most
of the weekend. Gusty northwest bring gusts close to gale force Sat into
Sat night with strong Small Craft Advisory needed for Sunday.
Monday...moderate confidence. Winds and seas will slowly diminish.
&&
Tides/coastal flooding...
Rhode Island South Coast this evening...
a moderately strong southerly fetch of surface wind and increasing
low level jet is expected to drive enough water into Narragansett
Bay for a surge around or even just above a foot at the time of
the evening high tide...about 2330z. This will be on top of a
particularly high Spring tide. Both the estofs and etss surge
guidance depict essentially no surge this evening but seems like
too much of a S to SW wind to avoid some surge...and at 15z pvd
was already showing a .4 feet surge and climbing. In
addition...shoreline flooding could be exacerbated some by any
heavy rain producing fresh water runoff that struggles to drain
at the shoreline during high tide.
East Coast of Massachusetts this weekend...
astronomical high tides will occur this weekend into early next week.
With surface low wobbling over southern New England Saturday and
into Sunday...expect gusty northerly to northwest winds especially
during the daytimes hours. At Boston...a high tide of 11.9ft will
occur on Friday night at 11:21 PM and 12.2ft early Sunday morning
at 12:12 am. Expect a light southerly winds during the Friday high
tide so this is less than 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 expect 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...none.
New Hampshire...none.
Rhode Island...coastal Flood Advisory until 9 PM EDT this evening for riz002-
004>007.
Marine...Small Craft Advisory until 10 am EDT Friday for anz232.
Small Craft Advisory until 6 am EDT Friday for anz233-234.
Small Craft Advisory until 10 PM EDT this evening for anz230-
236.
Small Craft Advisory until 4 am EDT Friday for anz231-251.
Small Craft Advisory until 6 PM EDT Friday for anz235-237.
Small Craft Advisory until 8 PM EDT Friday for anz250-254>256.
&&
$$
Synopsis...kjc
near term...kjc
short term...kjc
long term...dunten
aviation...kjc/dunten
marine...kjc/dunten
tides/coastal flooding...
