Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service Taunton Massachusetts
145 am EDT Sat Apr 19 2014

Synopsis...
a weakening cold front will move across southern New
England early this morning. High pressure will then build over the
region bringing dry and pleasant weather Saturday through Monday.
Low pressure and an associated cold front will likely bring a period
of wet weather to the region sometime late Tuesday into a good
portion of Wednesday. Another high builds in with dry... pleasant
conditions into late next week.

&&

Near term /until 6 am this morning/...

145 am update...

A cold front will cross the region early this morning. Very little
moisture is available with the front...so just expect a continuation
of some middle/high level cloudiness. Low temperatures will mainly be in the
30s...but some upper 20s are expected across portions of southwest
New Hampshire/northwest Massachusetts.

&&

Short term /6 am this morning through 6 PM Sunday/...

Saturday...
the cold front moves offshore Saturday morning. The trailing upper
trough crosses New England between 12z and 18z. There is some
concern for additional clouds popping as the coldest air moves
overhead. But the forecast moisture content of the airmass
diminishes...so we will follow model trends and go with clearing
skies. The solar heating and cooling temperatures aloft will allow for
deep mixing of the airmass with the mixed layer reaching to at
least 900 mb and probably to 850 mb. Winds in this layer tomorrow
will reach at least 25 knots...and there are some model
indications of 30 knots. This would mean gusts of 30-35 miles per hour mixing
to the surface toward midday and the afternoon.

Temperatures at 850 mb will be 0c to -2c...the NAM suggests -4c. With
full mixing this would support maximum temperatures in the middle 50s to around
60. The building surface pressures should be high enough to add
another 1-2f to these expectations. We will forecast middle 50s to
lower 60s.

Saturday night...
high pressure in Quebec builds over New England. Expect clear
skies and light winds with dewpoints in the 20s and lower 30s.
Radiational cooling should allow min temperatures in the upper 20s and
30s.

&&

Long term /Sunday night through Friday/...

Highlights...

* dry Sunday and Monday with chilly nights and mild days
* wet weather likely sometime late Tuesday into most of the
day Wednesday
* another high brings dry and seasonable conditions into late next
week

Overview and model preferences/confidence...
medium range models and ensembles continue to signal changing
conditions during this timeframe...from a rather flat...split flow
pattern early to a developing amplified...slowly progressive
pattern by the middle to end of next week. Question as to whether
this slowing in the upper levels will translate to the surface...
causing approaching frontal system during Tuesday into Wednesday to slow as
it moves off the coast. Operational model runs showing quite a bit
of spread beyond Wednesday as the next system that tries to shift
east out of the Great Lakes with...of all models...the 12z ec trying
to keep the next system moving faster while the GFS slows the
ridge across the region through Friday.

Used a blend of the GFS/ec ensembles along with the previous
forecast...giving good consistency. This was also pretty close to
the wpc guidance. Have overall moderate forecast confidence
Sunday into Wednesday...then lower confidence late next week.

Details...

Sunday and Sunday night...
large high pressure will build across Quebec during late Sunday into
Monday. Skies will start out mostly clear early Sunday
morning...then some clouds will develop especially along the coast
as east to northeast winds will bring cooler conditions. Expect
highs from only around 50 along the immediate coast...ranging to
the middle 50s to near 60 across the Connecticut River valley.

Ocean clouds may move inland during Sunday night with the onshore
winds as the high shifts across the Gulf of Maine to east of New
England. Expect generally light winds that will begin to shift to southeast
to S overnight. May also see some patchy fog develop along the shore
after midnight. With light winds...temperatures will fall back to the 30s
at most locations...though may hold near 40 along the immediate
coast. Some question as to the temperature regime...depending upon how much
cloudiness works inland.

Monday...
high pressure remains in control east of the region...though the ridge
tends to weaken during the day. Skies will be mainly mostly
sunny...though a few clouds might linger along the coast early.
Expect winds to become more southerly during the day but will
remain at 10 miles per hour or less. With the light pressure gradient across the
region and 850 mb temperatures rising to +6c to +9c during the day as the S
winds take hold...will see temperatures rise to the middle and upper 60s
well inland. Big question will be whether sea breezes develop
along the coast...which could keep temperatures back in the 50s. If they
do develop...may be rather shallow and remain within a few miles
of the shoreline.

On Monday night...middle and high level clouds will increase ahead of
approaching system out of the Great Lakes. Overnight lows will only
be in the 40s.

Tuesday and Wednesday...
models continue to signal a rather strong 500 mb short wave working east
out of the Great Lakes into northern New England later Tuesday.
Associated cold front will bring round of showers across the
region...though timing is still a bit uncertain. For now...looks
like best shot for precipitation will be from Tuesday night through most
of the day on Wednesday. Another question will be whether the
system slows down as it moves into the region on Wednesday. Models
still showing some solution spread with this aspect...though does
look like it should push offshore early Wednesday night.

Thursday and Friday...
another high ridge will looks to build down the eastern Seaboard
during Thursday...with another shot of dry but cooler air. Some
models try to keep some spotty precipitation along the coast early
Thursday.

Looks to be mainly dry on Friday as the ridge slowly pushes
offshore...though a warm front may bring a few widely scattered showers
late in the day or Friday night. Timing remains uncertain though.

&&

Aviation /06z Saturday through Wednesday/...
low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.

Short term...today through Sunday...

Today...high confidence. Any brief MVFR conditions in low
clouds/patchy fog across the southeast New England coast will burn
off by 12z. Otherwise...high confidence in VFR conditions.
Northwest wind gusts of 20 to 25 knots develop by afternoon.

Tonight and Sunday...high confidence in VFR conditions. Gusty
northwest winds diminish this evening.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf..

Outlook...Sunday through Wednesday...

Sunday night - Monday...high confidence.
VFR conditions.

Tuesday and Wednesday...low to moderate confidence.
VFR conditions to start on Tuesday. Ceilings/visibilities may lower to MVFR
in scattered showers and patchy fog late Tuesday through at least midday
Wednesday. Conditions should improve to VFR from west-east Wednesday
afternoon and evening.

&&

Marine...
forecaster confidence levels...

Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.

Short term /through Saturday night/...high confidence.

Winds most of the time will remain below 25 knots. It is possible
on Saturday that gusts close to shore may be near 25 knots. Winds
will shift to northwest on Saturday and north Saturday night. A
lingering swell will keep seas 5 to 7 feet through Saturday...and
5 foot seas may linger on the outer waters Saturday night.

Will continue Small Craft Advisory for hazardous seas on the outer
waters and on Massachusetts Bay/Ipswich Bay.

Outlook...Sunday through Wednesday...

Sunday...moderate to high confidence.
Expect NE winds to gust up to 20 knots early...then will diminish
during the day as they shift to east as the high starts to shift
offshore late Sun afternoon/Sun night. Leftover 5 foot seas
across the southern outer waters should subside.

Monday and Tuesday...moderate to high confidence.
Expect light southeast winds on Monday to become S Monday night and Tuesday.
Seas remain below small craft criteria.

Tuesday night and Wednesday...moderate confidence.
SW winds Tuesday night will shift to west as low pressure and cold front
move slowly across the waters. Expect northwest winds to pick up during
Wednesday...though timing is uncertain. Could see low end small craft
winds and seas late Wednesday or Wednesday night across the open waters.

&&

Fire weather...
weather conditions dry out during the day Saturday with dewpoints
in the 20s and minimum relative humidity values reaching 28-35 percent. Northwest
winds are also expected to pick up with gusts of at least 25
knots and possibly 30 knots. Weather conditions are sufficient to
create an elevated fire weather concern...but reports received so
far indicate ground conditions are still too moist. No fire
weather headlines will be issued at this time...but the situation
will be monitored.

&&

Hydrology...
minor flooding continues along portions of the main Stem CT river.
Most points have crested and are now receding...Middle Haddam will
crest tonight. See the latest flood statement for details.

Flood warnings remain posted along CT river at...

Northampton
Thompsonville
Hartford
Middle Haddam

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory for hazardous seas until 5 am EDT Sunday
for anz250-254.
Small Craft Advisory for hazardous seas until 10 am EDT this
morning for anz251.
Small Craft Advisory for hazardous seas until 1 PM EDT this
afternoon for anz255-256.

&&

$$
Synopsis...wtb/evt
near term...Frank
short term...wtb
long term...evt
aviation...Frank/evt
marine...wtb/evt
fire weather...wtb
hydrology...staff