Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbox 201129 
afdbox

Area forecast discussion
National Weather Service Taunton Massachusetts
629 am EST Tue Feb 20 2018

Synopsis...

A mild southwest flow will bring unseasonably mild temperatures
today with record warmth possible Wednesday. A cold front moves
through Wednesday night followed by much colder weather
Thursday. A wave of low pressure tracking along the front may
bring some rain Thursday, possibly mixed with snow in the
interior. An active wet weather pattern Friday through the
weekend during which there is the possibility of mixed
precipitation, freezing rain.

&&

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

630 am update...

Dense fog advisory till 9 am. High dewpoint air streaming north with
SW flow over the cooler waters, colder ground. Condensing, dense
fog developed overnight and continues this morning. Climatologically,
expect improvement across the interior, but low clouds and fog to
persist along the immediate S-coast, hampering marine traffic over
the near-shore waters especially to and from the islands which will
also remain socked in. HWRF and narre-tl, along with href and nbm,
all agree on soupy conditions just off the S-shoreline that will
likely require an extension of the dense fog advisory for some
areas should visibility hold at or below a quarter of a mile.

GFS / NAM / rap indicate decreasing moisture in the 1000-950 mb
layer which should lead to partial sunshine developing in the
afternoon, especially interior. For those areas it should warm
up into the 50s to low 60s, the full heating potential missed by
the limited mixing as noted by the prior forecaster, capped close
to h95. Will however aid in breezy SW winds, gusts up to 25 mph
at times. Otherwise, along the S-coast remaining cool, some
locales holding around the 50 degree mark.

&&

Short term /6 PM this evening through 6 PM Wednesday/...

Tonight...

Mild SW flow continues tonight. Abundant low level moisture will
lead to areas of stratus and fog redeveloping, most prevalent
along the South Coast. Dry air in the mid levels so patchy
drizzle possible. Temps may remain at or above 50 degrees
tonight, except 40s cape/islands and immediate South Coast.

Wednesday...

Persistent SW flow continues ahead of approaching cold front.
Areas of stratus and fog expected to burn off with at least
partial sunshine developing by afternoon. Soundings indicate
slightly deeper mixing than today, up to 925 mb where temps
15-16c. With full sunshine, potential would exist for low to mid
70s in the interior. However, low clouds expected to linger
through the morning which may limit full potential so expected
highs upper 60s to lower 70s away from the South Coast which
would still comfortably establish record highs at bos,bdl,orh
and close call at pvd. These temps are up to 30 degrees above
normal. SW flow with gusts to 25 mph will keep temps in the 50s
along the immediate South Coast.

Cold front approaching from the west may bring a few late day
showers to western Massachusetts.

&&

Long term /Wednesday night through Monday/...

*/ highlights...

- showers Wednesday night
- cold rain, wet snowflakes Thursday
- active weather pattern Friday through the weekend
- watching for potential mixed precipitation, freezing rain
- pattern change early next week

*/ overview...

Persistent southeast Continental U.S. Sub-tropical 500 mb ridge maintained by parked north-
central Pacific split flow and downstream 500 mb trof over the west Continental U.S.
Generating a warm-moist atmospheric river from the central Pacific
NE to southeast Canada. But nothing lasts forever. Breakdown of upstream
pattern, thermal wind flattens through which impulses stretch, dip
southward. A brief midweek warm-up is followed by an active weather
pattern late week into the following week. Along a parent frontal /
baroclinic zone, sulked S, stretching across the NE conus, thermal
profiles in question as intriguingly ensembles signal an evolving
blocky North Atlantic pattern per forecast strong -nao into March. Will
hit on targets of opportunity below. Ensemble guidance preferred.

*/ Discussion...

Wednesday night into Thursday...

Leaning with the cold front pushing S, suppressed via high pressure,
sinking mid-level air. Showers overnight. Attention turns to a wave
ejecting along the baroclinic zone into Thursday. Daytime event, 2m
temperatures wavering around 34. An over-running event, perhaps some
vertically-staggered west-east banding pressed up against the 1040+ high,
as cool, dry air undercuts. Expect a cold rain event, wet snowflakes
mixed in, but no accumulation. More activity/outcomes closer to the
S-coast of New England.

Thursday night...

Hold with an influential near 1040 high and hold off on any weather.
With that, light winds, mostly clear conditions, favor radiational
cooling and will lean towards cooler 2m temperature guidance.

Friday into Friday night...

Lifting warm frontal disturbance with surface high pressure settled
to the east. Noting ageostrophic wind profiles, wet-bulb temperatures,
low level thermal profiles, will be monitoring for potential shallow
cold air to lock-up briefly across north/west Massachusetts especially within interior
sheltered valleys. Can't rule out a short period of freezing rain,
confidence gained via cips analogs. Otherwise rain and warming
temperatures, non-diurnal trend during the overnight period.

Saturday into Sunday...

More potent Continental U.S. Disturbance ahead of which high pressure builds
over east Canada. Will be monitoring for precipitation-type issues once
again with the possibility of a near-shore secondary low developing
despite the thrust of stronger dynamics north/west across the Great Lakes
region. Beyond 120 hours, notable ensemble member spread, confidence
low at this time. Cips analogs indicate freezing rain, mainly north/west Massachusetts
per a top analog from early February 2008. Snows further N/W.

Early next week...

Perhaps a breather before the pattern begins to change as noted in
the overview section above.

&&

Aviation /11z Tuesday through Saturday/...

Forecaster confidence levels...

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

Short term /through Wednesday/...moderate confidence.

Today...

IFR-LIFR cigs and vsbys will lift and erode away from S-shore
terminals where fog and ovc002-008 cigs are likely to persist for
much of today with perhaps some minor improvements close to MVFR.
SW winds with gusts up to 20 to 25 kts especially over southeast areas
of New England.

Tonight...

Stratus and patchy fog redeveloping with MVFR/IFR conditions.
Areas of LIFR along the South Coast. Patchy drizzle.

Wednesday...

IFR/MVFR to start, improving to VFR by afternoon. SW gusts to
25 kt.

Kbos terminal...moderate confidence in taf. Improvement expected
into this morning, VFR through the day. Will lower to IFR this
evening and overnight, but given a SW wind will hold it there.

Kbdl terminal...moderate confidence in taf. Web cam observations
across the area show improvement and presently the terminal is
VFR. Expect some lingering IFR-LIFR conditions during sunrise
then VFR with breezy SW winds much of today. IFR-LIFR conditions
returning this evening and overnight. Low level wind shear threat developing as
S winds become light.

Outlook /Wednesday night through Saturday/...moderate confidence.

Wednesday: mainly VFR, with areas MVFR possible. Breezy. Patchy
fog.

Wednesday night: VFR. Breezy. Chance rain.

Thursday: VFR. Chance ra, chance snow.

Thursday night: VFR. Slight chance ra, slight chance fzra,
slight chance sn, slight chance pl.

Friday: VFR. Chance ra, chance fzra, chance pl.

Friday night: MVFR/IFR conditions possible. Chance ra, chance
fzra, patchy br.

Saturday: mainly VFR, with local MVFR possible. Chance rain.

&&

Marine...

Forecaster confidence levels...

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

Short term /through Wednesday/...high confidence.

Persistent SW flow. Modest low level jet over the waters through
Wed but strong inversion will prevent winds from mixing down.
Expect gusts mostly below Small Craft Advisory but up to 20kt at times. Poor
vsbys in fog expected for most of the period, mainly over south
coastal waters.

Outlook /Wednesday night through Saturday/...

Wednesday: winds less than 25 kt. Seas up to 5 ft. Areas fog.
Local visibility 1 nm or less.

Wednesday night: winds less than 25 kt. Local rough seas.
Slight chance of rain.

Thursday: winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain.

Thursday night: winds less than 25 kt. Chance of rain, slight
chance of freezing rain.

Friday: winds less than 25 kt. Chance of rain, chance of
freezing rain.

Friday night: winds less than 25 kt. Chance of rain.

Saturday: winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain.

&&

Climate...

Record highest observed temperature for February...(since
records began)

Boston.........73 (2/24/2017)
Hartford.......73 (2/24/1985)
Providence.....72 (2/24/1985)
Worcester......69 (2/24/2017)

Record high temperatures...

February.......2/20......2/21

Boston.........68 (1930) 63 (1906)
Hartford.......69 (1930) 63 (1930)
Providence.....69 (1930) 63 (1930)
Worcester......65 (1930) 59 (1930)

Record warmest min temperature...

February.......2/20......2/21

Boston.........46 (1930) 45 (1994)
Hartford.......50 (1981) 49 (1981)
Providence.....48 (1981) 50 (1981)
Worcester......47 (1981) 43 (2002)

Extreme high dew points...
dew point forecast has values in the 50s Tuesday and Wednesday.

February.......2/20......2/21

Boston.........54 (1991) 56 (1953)
Hartford.......53 (1981) 55 (1989)
Providence.....58 (1939) 56 (1989)
Worcester......53 (1981) 54 (1953)

&&

Box watches/warnings/advisories...

CT...dense fog advisory until 9 am EST this morning for ctz002.
Massachusetts...dense fog advisory until 9 am EST this morning for maz020>024.
Rhode Island...dense fog advisory until 9 am EST this morning for riz006>008.
Marine...Small Craft Advisory from 7 PM this evening to 7 PM EST
Wednesday for anz235.
Small Craft Advisory until 7 PM EST Wednesday for anz250-
254>256.

&&

$$

Synopsis...kjc/sipprell
near term...kjc/sipprell

National Weather Service Glossary of Abbreviations