Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
1011 am EST sun Feb 14 2016

Synopsis...

Historic Arctic outbreak for the modern era continues with
dangerously cold wind chills of 25 to 35 below. Winds diminish
later today and especially tonight...but it will remain bitterly
cold. A period of accumulating snow is then likely for much of
region especially away from the coast late Monday afternoon and
evening...changing to rain by Tuesday morning. A powerful storm
system will likely track west of New England Tuesday into Tuesday
night bringing heavy rain...strong winds and warm temperatures to
the region. A trend toward drier and colder weather follows on
Wednesday and Thursday. Another weather system will bring snow and
rain toward the end of the week.

&&

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

*/ highlights...

* dangerous wind chills of 25 to 40 below zero towards noon

* historic Arctic outbreak for the modern era brings the coldest
temperatures to Boston and Worcester since 1957

Wind chills 25 to 35 below-zero persist towards noon. But the
threat will diminish as winds relax through the day with high
pressure building into the area. Still frostbite will remain a
threat which can occur on exposed flesh in just 10 minutes.

Abundant sunshine but beneath a continued Arctic airmass aloft. A
dry subsidence inversion building across the region in tandem with
high pressure will limit mixing through the day per sinking air.
Highs around the single digits to teens. Record minimum high
temperatures likely to be set. Ocean-effect snow showers over the
Outer-Cape will diminish with the winds to flurries late. Just
trace accumulations.

&&

Short term /6 PM this evening through 6 am Monday/...

***bitterly cold tonight but without the wind***

High pressure building across southern New England will result in
light winds and an ideal night of radiational cooling. Given the
Arctic air firmly in place across the region...it will be another
bitterly cold night but with out the wind. Guidance temperatures may be
10+ degrees too warm in the typically prone outlying locations.
Would think we see low temperatures near 20 below zero in the typically
coldest outlying locations of western Massachusetts. Most other areas will
likely see low temperatures between -5 and -15...but some urban heat
islands will not get quite that cold. One example is Boston...which
should see low temperatures remain above zero given lack of cold advection
with that location needs to get below zero.

&&

Long term /Monday through Saturday/...

Highlights...

* wintry mix possible Monday night
* heavy rain expected on Tuesday
* brief cool down Wednesday night into Thursday

Overview and model preferences...

Although current western hemispheric setup shows negative nao/ao
and positive pna...which has allowed Arctic air to spill somewhat
modified Arctic air across the region...this will be changing. In
fact...the more amplified flow pattern becomes much more zonal
across the central Continental U.S. Much of the coming week and these same
teleconnections trend in the opposite direction. This suggests a
fairly active pattern but with less cold air than the last week or
so. Indeed the two most impactful features currently prognosticated look
to be inside runners thanks to earlier sharpening of the
associated trough along with some influence of the southern stream. A
blend of operational guidance will be used as a baseline as the
track discrepancies are beginning to converge for the Tuesday low pressure
passage.

Details...

Monday...
high pressure will be moving over the region through the day on Monday.
Although temperatures will start cold thanks to good radiational cooling
Sun night...modest late day return flow will allow for some
warming as h92 temperatures increase back to near -8c. This will allow a
bit of a reprieve as highs go back into the 20s to middle 30s.
However...diurnal cooling...along with evaporational cooling is
expected as isentropic lift begins by late afternoon/evening.

Monday night into Tuesday night...
strengthening but non-occluding low pressure approaches from the
Mississippi Valley...carrying with it Gulf moisture and precipitable waters of 2
Standard deviations above normal...or generally above 1.00 inches.
Isentropic lift on the front end Monday night will yield evaporative
cooling and diurnal cooling such that precipitation will start in the
evening as light-moderate snow. Quantitative precipitation forecast values during this period range from
about 0.1 to 0.25 inches...so where it stays deeply coldest the
longest /NW MA/...as much as 2-3 inches of snow /less and less
toward the coast/ is possible before warmer air above 0f moves in
at h92-h85. This will begin a transition to rain from S-north after
midnight through about 7am. Not a traditional cold air damming
situation here as high pressure is oriented well to the
east-northeast...although do note some response in the mass fields in the
form of an inverted ridge. Therefore...can/T rule out some ice
accretion on the new fresh snowpack...especially in the CT valley
and colder valleys of the Worcester Hills and northern CT high
terrain. Possible T-0.2 inches of ice is possible...suggesting at
least winter weather advisories are likely going to be needed.

By Tuesday...warm advection will have increased enough to bring surface
temperatures above normal in spite of the modest snowpack across the
region. This will lead to a changeover to all rain. Heavy rain
looks likely at times given the high precipitable waters and increasing low level jet with
60-70 knots possible as low as h92. Quantitative precipitation forecast values could be greater than
an inch after the changeover given the dynamics and moisture
available...so will need to watch for minor/nuisance flooding
especially as snows could clog area drains. Other issues is the
low level jet itself...which could yield dangerous strong winds.
However...the early snow and increase in temperatures aloft could yield
enough of an inversion to limit potential wind gusts. BUFKIT
currently supports this hypothesis...keeping any momentum Transfer
numbers below even advisory criteria. Will still need to watch
this however...given how strong the low level jet is expected to be /as much
as 3 Standard deviations above h92 normal/. Overnight lows in the 20s
will give way to highs mainly in the upper 30s and 40s...although
an isolated 50f cannot be ruled out.

Wednesday into Thursday...
secondary Arctic front will be sliding through the region
following the exiting low pressure. Wednesday highs still mild...mainly in
the upper 30s to upper 40s as the cold air will not arrive until
overnight. An isolated overnight shsn is possible as the wave
moves through...but overall this feature is moisture starved so
any accums would be light. However the increased cloud cover will
keep mins mainly in the 20s. By Thursday...h92 temperatures are back to near
-10c...so highs will only be in the 20s to middle 30s at the warmest
in spite of the clearing skies.

Thursday night into Friday...
high pressure crests over the region...with another gradual warming
trend as the high moves east and h92 temperatures return to near -4c. This
suggests highs Friday back in the 40s once again.

Sat into sun...
although far from a washout...Alberta clipper associated with
shortwave energy currently wrapped up in the alleutian vortex will
be crossing the region. Current steering flow suggests a northward
passage which keeps southern New England on the climatologically drier
side of a clipper. Therefore...expect the milder weather to
continue...with a risk for rain showers for a period once the timing is
better locked in. This will be likely once the aforementioned
shortwave moves onshore from the Pacific.

&&

Aviation /15z Sunday through Thursday/...

Forecaster confidence levels...

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

Short term /through tonight/...

No major changes with 12z update...

Today and tonight...high confidence.

VFR. Northwest-gusts 20-30 kts diminishing through the day as well as MVFR
threats with -shsn persist for the Outer Cape. With -shsn only
expect light snow accums.

Kbos terminal...
northwest-gusts up to 30 kts expected for the early-half of the day. Will
taper thereafter.

Kbdl terminal...high confidence in taf.

Outlook /Monday through Thursday/...

Monday...high confidence.
VFR. Winds shift out of the southeast.

Monday night into Tuesday night...moderate confidence.
Periods of IFR/MVFR due to a combination of low ceilings and visibilities.
Precipitation starts as snow Monday evening...then transitions to a brief
period of freezing rain/sleet briefly before turning to all rain during the
day on Tuesday. Southeast winds may gust 20-30 knots at times during the day on
Tuesday...but very strong winds just off the deck could mix down at
times. Expect low level wind shear...with as much as 60-70 knots at 2kft.

Wednesday into Thursday...moderate confidence.
Mainly VFR but with cooling conditions late Wednesday into Thursday. Low risk
for an isolated shsn Wednesday night.

&&

Marine...

Forecaster confidence levels...

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

Short term /through tonight/...high confidence.

*/ Highlights...

* heavy freezing spray/Arctic sea smoke and gale force wind gusts
persists into middle/late morning before diminishing

Northwest-gusts to diminish along with the threats of gale force winds
and heavy freezing spray. Headlines to alter over all waters by
midday to a freezing spray advisory along with small craft
advisories. Anticipating all headlines to drop off into this
evening. Arctic sea smoke lingers with the record breaking Arctic
air across the waters with sea surface temperatures in the low 40s.

Outlook /Monday through Thursday/...

Monday...high confidence.
Quiet boating weather with high pressure over the waters.

Monday night into Tuesday night...moderate confidence.
Low pressure will approach from the SW...then move inland during the
day Tuesday. Increase southeast winds will lead to gusts 25-30 knots Monday
night...then shifting late Tuesday night. Seas build during this time
as well...and could reach 10-13 feet by Tuesday evening. Small craft
advisories will be needed. There is a low risk for gales...but it
is uncertain at this time.

Wednesday and Wednesday night...high confidence.
Winds shift to the west...but drop below 25 knots. Seas will begin to
subside...but will take some time. So small craft advisories are
likely to continue through much of the day for seas alone.

Thursday...high confidence.
Although wind gusts should remain below threshold as winds shift
to the northwest and persist...there could be 5-7 feet seas persisting on
the ocean waters.

&&

Climate...

***coldest temperatures recorded in Boston/Worcester since 1957***

Record low temperatures for February 14th

Boston -9 /prev -3 in 1937/. Coldest since 1957.
Hartford -12 /prev -9 in 1979/.
Providence -9 /prev -7 in 1979/.
Worcester -16 /prev -11 in 1979/. Coldest since 1957.

Record minimum highs for Feb 14th...

Boston.......14/1916
Hartford.....11/1979
Providence...10/1979
Worcester.... 7/1979
Blue Hill....10/1979

Record cold lows for 15th...

Boston...... -14/1943
Hartford.... -18/1943
Providence.. -14/1943
Worcester... -19/1943
Blue Hill... -18/1943

&&

Box watches/warnings/advisories...

CT...wind chill warning until noon EST today for ctz002>004.
Massachusetts...Wind Chill Advisory until noon EST today for maz022>024.
Wind chill warning until noon EST today for maz002>021-026.
Rhode Island...Wind Chill Advisory until noon EST today for riz008.
Wind chill warning until noon EST today for riz001>007.
Marine...heavy freezing spray warning until 11 am EST this morning for
anz231>235-237-250-251-254>256.
Small Craft Advisory until 4 PM EST this afternoon for anz230-
232>237.
Small Craft Advisory until 10 PM EST this evening for anz231-
251-255-256.
Gale Warning until 2 PM EST this afternoon for anz250-254.

&&

$$

Synopsis...Frank/doody
near term...Frank/doody/sipprell
short term...Frank
long term...doody
aviation...Frank/doody/sipprell
marine...Frank/doody/sipprell
climate...weather forecast office box staff

National Weather Service Glossary of Abbreviations