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Area forecast discussion
National Weather Service Taunton Massachusetts
115 PM EST Thu Feb 23 2017

Synopsis...
high pressure centered offshore southeast of New England will
bring dry and unseasonably warm conditions today and tonight. A
cold front stalls over southern New England tonight and then
moves north as a warm front Friday. A strong cold front will
cross the region late Saturday afternoon and night, bringing
areas of rain and patchy fog. There will be a low chance for
isolated thunderstorms as the front passes. Near seasonable
temperatures will return early next week, with blustery
conditions on Sunday and Monday. There may be another chance for
precipitation around the middle of next week.

&&

Near term /until 6 PM this evening/...

1 PM update...

*** record highs this afternoon away from the South Coast ***

+12c air at 925 mb has mixed to the surface and resulting in
record highs this afternoon with most locations away from the
South Coast already in the low to mid 60s with some locations
briefly hitting 70 before the day is over. As of 1 PM new
record highs at Providence (66), Boston (66) and Worcester (62).
65 at bdl 1 PM and likely getting very close to their record
high of 68. As mentioned above temps will likely rise a few
more degs. Adjusted temps to reflect this thinking and trend.

Across Cape Ann seabreeze from the southeast has kept temps in
the 50s but thinking south-southwest gradient will increase enough the next
few hours to flip winds to the south-southwest and temps climbing into the
60s.

Low clouds and areas of dense fog will continue to impact the
South Coast including Cape Cod and the islands the remainder of
the day. Tricky how this will evolve as this low level moisture
is beginning to lift and erode partial across Long Island New York.
This may be the trend here late today and early evening will see
some improvement but then low clouds and fog becoming more
widespread later tonight as surface ridge builds northwest off
the Atlantic.

See climate section below for records highs today.



&&

Short term /6 PM this evening through 6 PM Friday/...
tonight...

Cold front trailing the Canadian low will drift into or near
southern New England tonight, but becomes parallel to the upper
flow by midnight and should stall by that time. Digging
shortwave over the plains will eventually turn the upper flow
more southwest and push the stalled front north as a warm front.

Although placement of the front when it stalls will determine
our overnight weather, it seems likely that most of our area
will remain south of the front...certainly the areas south of
the Mass Pike. This will mean another night of moist air with
fog and low clouds again moving ashore from the south. Dense fog
may again be a concern overnight. Dew points in the 40s point to
min sfc temps in a similar range.

Friday...

Cold front slowly lifts north of our area during the day.
Southwest flow will increase through the day, eventually
generating lift across the front and resulting in light rain or
showers. The best chance of this will be in areas north of the
front, northern Massachusetts.

Clouds will work against similar temps to Thursday. But temps at
1000 mb continue to support Max sfc temps near 60. The southwest
flow will again work to keep South Coast areas several degrees
cooler.

&&

Long term /Friday night through Wednesday/...
highlights...

* mild with widespread showers likely Sat into Sat night
* blustery and cooler sun/Mon
* more active pattern for next week

Pattern overview...

00z guidance is in general agreement synoptically, still have some
several mesoscale features to resolve. Synoptically potent plains
trough will move towards New England on Saturday pushing a cold
front through by Saturday night. Chilly and blustery conditions for
Sunday and Monday as zonal flow takes shape. Guidance diverges
beyond Sunday leaving a low confidence forecast. Zonal flow to start
but the GFS is more progressive and develops a quick moving system
on Monday while the ec is dry until Tuesday. Timing issues need to
still be resolved. Next system to watch is Wednesday/Thursday
timeframe but model sensitivity to this system is high as the ec is
more progressive than the GFS. Regardless, looks like precip during
the mid-week with cooler temperatures once again by Thursday.
Trended the next weeks forecast towards a blend of the ensembles as
well as the ec which appears to be inline with the UKMET.

Details...

Saturday into Saturday night...

Potent shortwave will move through the flow and approach southern
New England on Saturday. This wave will drag a cold front across the
region ending the chances for above average temperatures.

During the morning, appears to be enough low level moisture trapped
under an inversion to keep low clouds and drizzle across a portion
of the area. Highest confidence is across the South Coast, but this
area can be greater as surface southerly winds will continue to
advect higher dewpoint into the region.

Ahead of the front, anomalous southerly flow with low level jet increasing to
35-45 kts as 925 mb temps warm to 11c. This will result in above
average temperatures for the region as well as gusty winds. Precipitable water
values also increase near 2 Standard above normal as southern stream
moisture is fed into the system. Along the front, a secondary low
will develop but appears it will be to far north and east and will
to keep southern New England out of the heavy qpf. This appears to
be inconjunction with the gefs as well as the ec ensembles which has
just a 20 percent prob of qpf over 0.5 inch. Will need to continue
to watch this secondary low and see where it will eventually develop
during this system.

Otherwise appears that the bulk of the heavy precip will be across
upstate New York and Vermont including The East Slope of the Berks. This area
is where the better dynamics will be as well as enhancement due to
upslope. May need to watch river levels after this system because of
the heavy rainfall potential and snow melt up north. Right now
ensembles are pointing towards a few sites near action stage.

As the cold front approaches, does appear that profiles turn moist
adiabatic. This may help mix some of the higher winds to the
surface. So cannot rule out a few gusts above 40 miles per hour. Also guidance
continues to show some elevated instability with tt above 50 and Li
below 0. Because of the steep pressure falls with this system,
cannot rule out the potential for a rumble of thunder and have
continued to mention the potential in the forecast.

Frontal passage will be quick as temperatures plummet behind the front. Could
see some wet flakes on the backside depending on how much moisture
is left as front moves through. Right now cannot rule out an inch
across far northwest mass.

Sunday into Tuesday...

Chilly and blustery northwest flow will take over the region by Sunday into
Monday. Temperatures difference between Saturday and Sunday could be
close to 15-20f. Wind gusts could also increase close to 30 miles per hour as
the region mixes well above 850mb. This will result in wind chill
values in the 30s. A Stark contrast from the previous several days.

Guidance mesoscale issues come to light by Monday as a weak wave
appears to move through the flow. 24 hour timing difference between
the GFS and ec with the ec pushing the system through on Tuesday.
The latest ecens and gefs are leaning closer to the ec keeping the
high pressure over the region on Monday. However there are still a
few members that are on the fast side. Whether this system comes in
on Monday or Tuesday we could see some rain/snow showers for the
region. Low confidence on timing.

Wednesday and beyond...

Large spread in the guidance for this period. Synoptically mean
upper level ridge over the Atlantic will help temps warm above
average. However potent shortwave moving through the Great Lakes
will push a warm and cold front towards southern New England. A lot
of issues to be resolved in exact placement of the low and if any
secondary low pressure systems develops. But right now models are in
agreement on the timing with this system coming through Wed
PM/Thursday with another cold snap behind it.

&&

Aviation /18z Thursday through Tuesday/...
forecaster confidence levels...

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

Short term /through Friday/...

1 PM update...

Thru 00z...moderate forecast confidence with some uncertainty at
the interface of VFR-IFR

VFR and south-southwest winds 10 to 20 kt. IFR and LIFR along the South
Coast including Cape Cod and the islands.

After 00z...low confidence forecast with lots of uncertainty on
areal extent of IFR-LIFR conditions.

IFR-LIFR likely South Coast this evening. Thinking is these
conditions slowly creep northward tonight but confidence is low.
Patchy drizzle may accompany these low clouds as well.

Friday...moderate confidence.

Combination of IFR-MVFR in the morning with slow improvement to
from south to north. Low risk of some spotty light rain across
northern Massachusetts.

Friday night...MVFR likely with light spotty showers/drizzle
possible.

Kbos taf...high confidence until about 00z then diminishing
tonight and thereafter.

Kbdl taf...high confidence until about 00z then diminishing
tonight and thereafter.

Outlook /Saturday through Monday/...

Saturday...moderate confidence. Fog and drizzle to start the day in
MVFR/IFR conditions. Potent cold front will move through Sat PM
brining heavy rain, gusty winds near 30 kts and the potential for
thunder. Behind the front could see some wet flakes across the northwest
terminals. All of this could drop conditions to IFR/LIFR overnight,
but anticipate a rapid improvement near dawn Sunday.

Sunday...moderate confidence. Improving conditions with blustery northwest
wind gusts near 30 kts.

Monday...low confidence. Still a large spread in guidance. Mainly
VFR conditions with northwest gusts near 25kts. Could see some sct showers
across the South Coast.

&&

Marine...
forecaster confidence levels...

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

Short term /through Friday/...high confidence.

1 PM update...

Low clouds and fog will impact the south coastal waters much of
the day with patchy dense fog embedded in this area. Elsewhere
very tranquil weather for late Feb.

Previous discussion below...



Tonight and Friday...

Cold front moving south will stall overnight or Friday morning,
then move slowly north. The Massachusetts North Shore may spend
a few hours north of the front with winds shifting from the east
or southeast. Areas south of the front will maintain southwest
winds through the period.

Outlook /Friday night through Monday/...

Saturday...moderate confidence. Increasing southerly flow with the
potential for Small Craft Advisory gusts. Waves will also increase in response. Vsbys
reduced in developing rain and fog. Low potential for thunder late
in the day.

Sunday...high confidence. Northwest winds will keep seas up and
increase wind gusts near 30 kts. Low probability for gales across
the outer waters.

Monday...low confidence. Large spread in the guidance but gusty northwest
winds will continue keeping seas up for sometime.

&&

Climate...

Updated 1 PM...

Record highs for Thu Feb 23

Bos...65/1990 (66 at 1 pm)
bdl...68/1990 (65 at 1 pm)
pvd...60/1990 (66 at 1 pm)
orh...61/1990 (66 at 1 pm)

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

$$

Synopsis...wtb/dunten
near term...nocera

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