Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Taunton Massachusetts
359 am EDT Sat Mar 15 2014
a brief band of mainly rain showers will sweep across the region
this morning...followed by a breezy and mild afternoon. Dry...but
very cold and blustery conditions return later tonight and
Sunday.A coastal storm is expected to pass far enough offshore
Monday to spare the region a winter storm. A cold front will bring
more precipitation Wednesday and Thursday.
Near term /this morning/...
***brief band of mainly rain showers will sweep across the region
through late morning***
A 50 knot low level jet ahead of a shortwave was resulting in a
burst of middle level lift and instability. A band of mainly rain
showers will sweep across the region from west to east through late
morning. While the activity should be short lived in a given
location...feel most locations will see a brief period of rain
showers...so will continue likely probability of precipitation.
As for ptype...warming boundary layer on south to southwest winds
will result in mainly rain showers. However...initially dry air may
cause soundings to go isothermal at the onset across the higher
terrain of southwest New Hampshire/western Massachusetts...resulting in a brief period of
wet snow. Any accumulations would be a dusting to less than 1 inch.
Surface temperatures have warmed above freezing in all locations...so not
expecting freezing rain or the need for any winter weather headlines
Short term /6 am this morning through 6 PM Sunday/...
The initial band of rain showers should exit the region by late
morning. An upper level shortwave will then swing through the
region this afternoon. The cold pool aloft will result in scattered
to broken cumulus clouds...but still expect peeks of sun at times.
While most the late morning/afternoon will be dry...a spot shower or
two will be possible underneath the cold pool aloft so will include
a low pop.
Given mild start and good mixing with southwest wind gusts of 25 to
30 miles per hour...it will be a mild afternoon. High temperatures should top out in
the middle to upper 40s across the higher terrain...with mainly
lower to middle 50s elsewhere.
A strong cold front will cross the region tonight allowing much
colder air to work back into the region. The front will come
through mainly dry...but can/T rule out a flurry or two along the
east slopes of the Berkshires. Otherwise...low temperatures will be back
down into the middle and upper teens across the interior high
terrain...to mainly the 20s elsewhere by early Sun morning. West
winds will gust to between 25 and 35 miles per hour behind the front. This
will allow wind chills to fall into the high single digits and teens
Mostly sunny skies but unseasonably cold air will continue to work
into the region. 850 mb temperatures will fall to between -14c and -18c by
the end of the day. This should hold high temperatures to between 25 and
30 across the higher terrain....to the lower to middle 30s on the
coastal plain. West to northwest wind gusts of 25 to 35 miles per hour will
make it feel like its the middle of winter across the region.
Long term /Sunday night through Friday/...
overview and model preferences...
15.00z model guidance now starting to have reasonably good
agreement regarding final storm track of low pressure Sun night into
Monday. Arctic high pressure will have moved too far S on sun...combined
with positive nao/ao suggesting progressive flow across the
Atlantic. Therefore it appears the low will track too far S with
too much dry air to the north to have much affect on southern New England.
Given this general agreement...a blend of operational guidance
will be used for the middle term.
Following this low pressure...modest western Continental U.S. Ridge looks shunt
polar vortex a bit further north. Leading to reasonably progressive
split flow regime across the Continental U.S.. synoptically...there is fairly
good agreement here...suggesting a period of moderating
temperatures until secondary northern stream shortwave approaches /in
the form of an inside runner at the sfc/. The issue at hand is in
how amplified the flow pattern is by that point...which will
affect timing/strength of the low as it makes it/S pass. European model (ecmwf) is
more amplified and slower while GFS is less amplified and faster.
Ensembles from either family support both solutions here...so will
lean on an unsettled and potentially wet pattern for Thursday and Friday
until pattern is better nailed down.
Sun night into Monday...
surface high pressure approaching 1030 hpa will be gradually settling
across the NE Continental U.S....carrying dry/cold airmass with it. This
strong ridging now looks to shunt low pressure off the coast of the
Carolinas several hundred miles southeast of the 40/70 benchmark by 18z
Monday. Given the dry air...there will likely be a very tight
gradient of final precipitation...but bulk will remain offshore.
Currently only 12z European model (ecmwf) and 00z CMC bring and some ensemble
members bring 0.01-0.05 of quantitative precipitation forecast to ack/mvy...but not subsidence
inversion in their soundings. Given this...will continue downward
trend in probability of precipitation. Otherwise...850 mb temperatures around -10c to -14c suggest
temperatures remain below normal...with lows in the single digits in the
northwest where some radiation is possible outside of cloud cover to
teens and 20s near southeast MA/RI. Highs Monday rebound little...only low
to upper 20s.
Tuesday into Wednesday...
the Arctic high will crest across northern New England and then slide
offshore by the day Wednesday. Therefore...dry weather is expected to
prevail. Coolest temperatures expected Tuesday of the two days...as 850 mb temperatures
look to average around -8c...yielding highs mainly in the 30s.
Guidance may be too warm on Tuesday night as radiational cooling
setup looks apparent. By Wednesday though...as return flow develops
behind the exiting high it appears temperatures may final have a run at
Thursday into Friday...
northern stream shortwave will allow low pressure to deepen and gradually
slide in vicinity of the St. Lawrence pushing a cold front across New
England. As mentioned above...there are still some differences in
strength and timing. Some guidance...particularly
GFS/CMC...suggest secondary low pressure development S of Long Island
along the front which may drag more cold air into the system which
may promote a change-over. For now...will highlight at least
chance probability of precipitation throughout...for an unsettled and wet period. Will
blend in a little of the potential colder solution...but the European model (ecmwf)
/warmer/ solution has been more persistent. Therefore more weight
will be given to it. In either case...the northern stream wave does
appear to tap some sub-tropical moisture so some heavier precipitation is
not out of the question.
low confidence here...but it appears given the joining of southern and
northern stream flow that another fast moving northern stream wave may
effect the region by the weekend.
Aviation /08z Saturday through Wednesday/...
low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Short term...today through Sunday...
Today...moderate to high confidence. A period of MVFR
conditions along with a band of mainly rain showers will work their
way from west to east through 15z this morning. It may be just cold
enough for a brief period of wet snow across the higher terrain of
southwest New Hampshire/northwest Massachusetts. Otherwise...mainly VFR conditions
despite scattered to broken cumulus clouds this afternoon.
Southwest wind gusts of 20 to 30 knots expected.
Tonight and Sunday...high confidence in VFR conditions. West to
northwest wind gusts of 20 to 30 knots expected.
Kbos terminal...moderate confidence in taf through 15z...with high
Kbdl terminal...moderate confidence in taf through 15z...with high
Outlook...Sunday night through Wednesday.
Sun night into Monday...high confidence.
Mainly VFR as it appears coastal storm stays too far southeast to
affect southern New England terminals. Northwest winds subside Sun night and
shift to the north by Monday
Tuesday into Wednesday...high confidence.
Mainly VFR. North winds on Tuesday shift to the SW on Wednesday.
forecaster confidence levels...
Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.
Short term /today through Sunday/...
Today through Sunday...Small Craft Advisory headlines posted for all waters right
through Sunday. Southwest winds will gust to between 25 and 30
knots today ahead of our next cold front. The front will swing
across the waters tonight...shifting the winds to the west
northwest. Winds will continue to gust between 25 and 30 knots
tonight and Sunday in the cold air advection pattern. Low
probability for brief gusts to 35 knots very late tonight/early Sun
morning...but not enough to warrant gale headlines.
Outlook...Sunday through Wednesday...moderate confidence.
Sun night into Monday...moderate confidence.
Northwest wind gusts 25-30 knots and seas of 5-8 feet continue Sun night into
early Monday morning...but then gradually subside during the day Monday
such that small craft advisories will likely end through the day.
At this time it appears the coastal storm will stay well to the
southeast on Monday.
Tuesday and Wednesday...high confidence.
Mainly quiet boating weather as high pressure crests over the waters.
Marine...Small Craft Advisory until 8 PM EDT Sunday for anz230>237-250-