Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbox 192040 
afdbox

Area forecast discussion
National Weather Service Taunton Massachusetts
340 PM EST sun Feb 19 2017

Synopsis...
a cold front will be followed by a brief cool down tonight into
Tuesday. Milder weather returns the middle of next week.
However, another front may be accompanied by some precipitation
sometime Tuesday night into Wednesday. At this point, Thursday
has potential to be the warmest day of the week.

&&

Near term /until 6 am Monday morning/...
unseasonably mild day across southern New England with temps ranging through the
50s and near 60 across portions of CT/Rhode Island and southeast Massachusetts. Mid level
shortwave dropping south across new eng will drive a cold front
through southern New England late afternoon and evening followed by a wind shift
to northwest and colder temperatures overnight. Lows will settle back
to the upper 20s to lower 30s. Winds will become gusty across
the cape and islands with occasional gusts to 25-30 mph.

&&

Short term /6 am Monday morning through Monday night/...
Monday...
mid level trof amplifies to the east of New England as
additional shortwave energy rotates through. This will result
in a dry but brisk northwest flow. The column is dry which will lead to
mostly sunny skies, but some ocean effect clouds will be moving
across the Outer Cape. Temps will be near seasonable normals,
generally upper 30s higher terrain to lower 40s elsewhere. Northwest
winds will gust to 20-25 mph at times.

Monday night...
strong high pres builds into new eng with clear skies and
diminishing wind. Good radiational cooling will result in a cold
night with lows dropping into the teens in the colder outlying
areas and 20s elsewhere.

&&

Long term /Tuesday through Sunday/...
highlights...

* seasonably cool Tuesday
* light rain/pockets of freezing rain Tue night into Wed
* Thursday looks to be our warmest day
* more likely of widespread rain Friday night into Saturday

Overview and model preferences...
the initially amplified and complex synoptic pattern across the
east half of noam will gradually trend toward a more zonal
(although with SW-NE orientation) toward the end of the week.
This is mainly a response to an Arctic influenced wave which
should remain to our north as it meets the building heights within
ridging across the northeast and Maritimes. Still noting good
agreement amongst both ensemble and deterministic guidance that
positive 500hpa height anomalies remain through the long term,
suggesting the influence of warmer air and a quieter pattern
overall. This is indeed the case amongst guidance save for a
stronger wave arriving by late Fri-Sat. Given there is fair
agreement across the board, will continue with the consensus
blend used over the last few updates until some of the subtle,
mesoscale features are better resolved.

Details...

Tue...
quiet wx remains thanks to high pres which will crest early Tue
morning. Nearly isothermal profile with both h92 and 850 mb temps
between 0c and +3c suggests warmer temps, in the mid 40s for the
most part. Southerly flow with increasing moisture will yield
more clouds through the latter portions of the day.

Tue night into Wed...
the differences in timing of a weak warm frontal passage and
its attendant overrunning continue with the 19.12z guidance
update. GFS continues to be the faster model, but also the
weakest and driest while, out of the operational runs, European model (ecmwf)/CMC
are slower and slightly more robust. Noted a modest trend
toward the latter solution in both gefs/ecens members, so
timing/impacts will be more reflective of the ECMWF/CMC.

Modest overrunning begins overnight and continues through the
first few hours of daylight Wed. Isothermal profiles remain,
with low lvl temps mainly near 0c to +3c. Bulk of the moisture
(pwats only around 0.7 inches) relegated to the lowest 200hpa.
Initial wet-bulb processes could yield a mix of sleet/wet snow,
but this will shift to mainly rain. Pockets of freezing rain
possible, especially north central and west MA, as temps may drop near
or below freezing before precip onset, and wetbulbs will only be
lower. Not expecting much in the way of ice, but enough that
overnight, early am commutes could be slippery on untreated
roadways.

Otherwise, improvement on Wed outside of some lingering clouds.
Warming of h92 temps to nearly +6c to +8c by 00z Thu suggests
temps will rapidly rebound and may even approach the low 50s in
spots especially if enough afternoon sunshine is observed.

Thu and Fri...
modest clipper will move through north New England Thu. Although
little to no impact expected (outside of some clouds), the brief
increase in low-lvl temps in response, combined with a west
component to the mean flow, may yield the warmest day of the
week. H92 temps average +10c to +12c (as a comparison, today's
h92 temperatures are closer to +6c to +8c. Remaining snowpack,
additional clouds may limit mixing somewhat, but all conditions
point toward a day with widespread 60s possible. Ensemble
probabilities are supportive of this thinking. Some slight
cooling on Fri, especially with increasing clouds ahead of a
warm front suggests highs mostly in the 50s at best. Timing of
overrunning precip looks to hold until Fri night thanks to
initial mesoscale ridging possible.

Next weekend...
sharper wave currently wrapped up in the Aleutian vortex will
be forced east and may start taking on a neutral or even negative
tilt as it arrives in the Ohio Valley. Good agreement that parent
low pres remains an inside runner, but it will have some
connection to Gulf of Mexico moisture with precipitable waters approaching
1.3+ inches (3+ Standard deviations above normal). Within the
warm sector (saturday) low level jet 40-05 kt, tt values near 50 and mid
lvl lapse rates steeper than moist-adiabatic, therefore, will
need to watch for pockets of heavy rainfall at times along with
this feature passage. Can't even rule out a rumble of thunder or
two if conditions line up. Conditions improve sun, with a
return to much more seasonable cool temps following in the wake
of this stronger system.

&&

Aviation /21z Sunday through Friday/...
forecaster confidence levels...

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

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

Mainly VFR. Some MVFR cigs may develop across the interior
tonight into Monday morning. Also some ocean effect MVFR cigs
possible across the Outer Cape and ack late tonight and lasting
through Mon night. Northwest gusts to 25 kt developing over the Outer
Cape/islands later tonight into Monday. Elsewhere, northwest gusts to
20 kt expected Monday. Diminishing wind becoming light Mon
night.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook /Tuesday through Friday/...

Tue...high confidence.
VFR. Winds mainly S.

Tue night into Wed...moderate confidence.
Overnight low-moderate risk for some MVFR/IFR ceilings along with
occasional MVFR vsbys in light rainfall. Low risk for some light
icing with light freezing rain, mainly Worcester Hills and
western Massachusetts. Improvement to VFR gradually after sunrise on Wed.
Winds shift to the W-SW.

Thu and Fri...high confidence.
Mainly VFR. Low risk for some mixed MVFR ceilings by late day Fri,
but these may hold off until Fri night.

&&

Marine...
forecaster confidence levels...

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

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

Tonight...a surge of gusty northwest winds will develop behind a cold
front this evening with gusts 25-30 kt, strongest across eastern
waters.

Monday...winds gradually diminish below Small Craft Advisory by afternoon,
except across eastern waters where northerly gusts to 25 kt
will persist most of the day,

Monday night...some leftover northerly gusts to 25 kt eastern
waters in the evening, otherwise diminishing wind as high pres
builds into the waters.

Outlook /Tuesday through Friday/...

Tue into Wed...moderate confidence.
Quiet boating wx remains in place on Tue. Accompanied by some
light rain early Wed morning, west-SW wind gusts may reach near the
25 kt threshold for small craft advisories, but then diminish by
about mid day on Wed. Seas remain generally 5 ft or less, so
there is a low risk that a brief period of small craft
advisories may be needed Tue night into Wed morning.

Thu and Fri...high confidence.
Generally quiet boating weather even as winds shift from mainly
west-SW to east by Fri.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 10 PM this evening to 7 PM EST
Monday for anz231-232.
Small Craft Advisory from 1 am to 1 PM EST Monday for
anz233>235-237.
Small Craft Advisory until 1 am EST Tuesday for anz250-254.
Small Craft Advisory until 9 am EST Monday for anz251.
Small Craft Advisory from 1 am Monday to 1 am EST Tuesday for
anz255.
Small Craft Advisory from 1 am to 3 PM EST Monday for anz256.

&&

$$
Synopsis...kjc/doody

National Weather Service Glossary of Abbreviations