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Area forecast discussion 
National Weather Service Taunton Massachusetts
348 PM EDT Friday may 22 2015

Synopsis...
a cold front will move offshore this evening...ushering in
unseasonable cold air into much of western Massachusetts. Some locations
should see near record low minimum temperatures. There will also
be areas of frost tonight. Gradual warming is expected through
next week...leading to hot and humid conditions by middle week.
There is the low chance for a shower or thundershower Monday
through Wednesday.

&&

Near term /until 6 am Saturday morning/...
other than a spot evening shower associated with the frontal
passage...dry weather prevails overnight. Strong cold air
advection behind departing this front...will result in strong
negative seasonal departures...and near record low temperatures
for some locations.

The big question is whether or not winds will decouple
sufficiently to allow for frost formation. The raw model guidance
says no...but the MOS output suggests yes. Since the majority of
raw model guidance has a general high bias for wind speed...will
go more with the scenario of decoupling winds and stronger
radiational cooling. Favored a consensus of the MOS guidance...
which had lower temperatures than the majority of model 2 meter
temperatures. Freeze warnings issued for northwest Massachusetts...surrounded
by a ring of frost advisories. We could see some frost in the
normally colder locations across eastern Massachusetts...such as Norwood and
Taunton...but feel it will not be widespread enough to warrant an
advisory.

&&

Short term /6 am Saturday morning through Saturday night/...

Higher pressure over the Middle Atlantic States gradually increases
its influence on our weather Saturday into Saturday night. With
this high pressure remaining to our south...we will see a
continuation of a generally west wind. Present thinking is this
flow will be strong enough to prevent seabreezes from developing.

Unseasonable cold continues...with high temperatures Saturday only
recovering into the lower to middle 60s at most. More seasonable
temperatures are expected for Saturday night low temperatures.
Dry weather continues.

&&

Long term /Sunday through Friday/...
highlights...

- some showers possible over the interior Monday...but hit-or-miss
- gradual warming leads to hot and humid conditions by middle week.

Overview and model preferences...

With 22.12z model guidance continuing to converge on a solution...
agree with the latest CPC outlook that warmer than usual weather
will return after a cool start this weekend. Previous shift
forecaster noted that there is now much better agreement that
Bermuda high and it/S subtropical ridge are likely to gain control
over the region through at least middle week as longwave trough
continues to recede back into NE Quebec/Labrador. Therefore...
will be continuing this trend thanks to better confidence in the
latest run solutions. Kind of like the CMC/European model (ecmwf) as a blend to
start given their better consistency and slightly lower amplified
solutions. However...this mass field ridge is accompanied by
fairly robust Theta-E ridge with precipitable waters nearly 3 Standard deviations
above normal. To quote west.B. Yeats...the centre cannot hold...a
destabilized column could yield diurnal convection particularly as
a weakening cutoff low pressure currently over The Rockies shifts east
by Tue-Wed. Near neutral ao/nao also suggest The Block won't hold
up.

Details...

Sun...mainly a rebound day. The colder temperatures of Sat will be
giving way to more moderate...seasonal temperatures. 850 mb temperatures
will be reaching the near normal values of +8c to +10c. SW winds
will promote some downsloping so warmer locales of western Massachusetts/CT will
likely approach 80...while the remaining locales remain in the
70s. This moderate west flow is likely also to limit sea breeze
development.

Monday...as the upper ridge begins it/S building process low level jet and
attendant surface warm front will be nosing in from the west on the
periphery of this ridge. Suspect enough moisture convergence
/pwats increase to nearly 1.0 inches/ and lift associated with
this feature to yield a risk for afternoon -shra development
mainly across interior western mass/CT. Echo previous forecaster that
it is unlikely to be a washout...and cips analogs continue to keep
the bulk of the action to the northwest. 850 mb temperatures will increase to +10c
or +12c...but a little weaker mixing with increasing cloud cover
ahead may keep ambient temperatures near seasonal...but with increased
humidity as the building Theta-E ridge suggests dewpoints heading into
the 50s.

Tuesday and Wednesday...things start to get tricky here. Peak Theta-E
ridging and slight cooling at 500 mb are likely to yield moderate middle
level lapse rates within the warm sector. BUFKIT profiles denote
very high precipitable waters /near 1.75 inches/ along with surface based
instability 500- 1000 j/kg each afternoon. Stronger low level jet and upper
level divergence remain to the northwest on Tuesday...so suspect most
convective activity remains northwest. On Wednesday...reloading of the pattern
and secondary ridge building behind the Tuesday shortwave may mitigate
afternoon convective activity in spite of the destabilized
profile. Given the diurnally driven instability but with
mitigating factors...will increase probability of precipitation to low end chance in the west
each afternoon as it/S likely to be more hit or miss. Return
flow...with west component and warming middle level temperatures all suggest
continuous temperature moderation. Highs may approach the 90f in
warm spots. Dewpoints in the low-middle 60s suggest uncomfortable
humidity.

Thursday and Friday...once again a tricky forecast here. In this
case...better low level forcing is expected in the form of a more
robust middle level shortwave and attendant cold frontal passage.
However...at issue is the rebounding ridge mentioned early. This
will lead to an overall weakening of the cold front/trough system.
BUFKIT does show signs of a subsidence inversion in place which
could preclude afternoon convection. Instability still somewhat
favorable...but this is a week out. Will need to continue to watch
this period should the front slow to a near stall as it interacts
with the building ridge. Providing a near steady source of lift
for the destabilized atmosphere.

&&

Aviation /19z Friday through Wednesday/...
forecaster confidence levels...

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

Short term /through Friday/...

19z update...

Through tonight...west-northwest winds increase up to 25 knots in gusts. Spot
shower possible until 03z or so. Otherwise VFR and dry weather.

Saturday...west winds up to 20 knots in gusts. VFR and dry weather
prevail.

Saturday night...VFR...with diminishing west winds.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Sunday through Wednesday...

Sunday into Monday...high confidence. VFR. Mainly light west-SW
winds...with sea breezes likely. Low chance for a shower in western
Massachusetts/CT Monday afternoon and evening.

Tuesday and Wednesday...high confidence. Mainly VFR. Although some overnight
fog and stratus is possible near coastlines...this could lead to
localized IFR/MVFR. Also...SW flow dominates. Low chance each
afternoon/evening for afternoon showers/thunderstorms and rain mainly in the far
interior.

&&

Marine...
forecaster confidence levels...

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

Short term /through Saturday/...

Tonight...cold front sweeps across the waters with west-northwest winds
gusting up to 25 knots. Good visibility.

Sat...west-northwest winds 15 to 20 knots possibly gusting up to 25 early becomes
west-southwest 15 to 20 knots during the afternoon. No precipitation and good visibility.

Sat night...west-southwest winds briefly diminish below 20 knots. No precipitation and
good visibility.

Outlook...Sunday through Wednesday...

Sunday and Monday...high confidence. High pressure will move over the
waters yielding period of mainly quiet boating weather.

Tuesday and Wednesday...moderate confidence. Winds shift to the
SW...and increase with a few near shore gusts between 20 and 25 knots.
Expect a slowly building SW swell. There may be a need for small
craft advisories through this period...but not the entire time.
Some marine stratus and fog may develop...reducing visibilities.

&&

Fire weather...
very dry conditions expected Saturday...along with gusty west
winds. With the lack of appreciable rainfall across southern New
England last night...and information from state fire officials...will
issue a statement concerning an elevated risk for fires across
southern New England.

&&

Climate...
record lows for may 23rd...

Boston - 40 /1967/
Hartford - 37 /1976/
Providence - 40 /1950/
Worcester - 32 /1929/

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...frost advisory from 2 am to 7 am EDT Saturday for maz004-
009>011-026.
Freeze warning from 2 am to 7 am EDT Saturday for maz002-003-
008.
Rhode Island...none.
Marine...Small Craft Advisory until 11 am EDT Saturday for anz231>235-
237-250-251-254>256.
Small Craft Advisory until 8 am EDT Saturday for anz230-236.

&&

$$
Synopsis...Belk/doody
near term...Belk
short term...Belk
long term...doody
aviation...Belk/doody
marine...Belk/doody
fire weather...staff
climate...staff

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