Old Res Weather

Lexington, Massachusetts, USA

12/6/2023 9:54pm 
  • Lexington Conditions: Clear
  • Temperature: 26.8°F / -2.9°CColder 0.3°F than last hour.
  • Dew Point: 20.3°FDecreased 1.3°Fsince last hour.
  • Relative Humidity: 76%Decreased 3.0% since last hour.
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 29.99 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.00 in
  • UV Index: $VPuv None

Area Forecast Discussion
for Boston / Norton, MA

FXUS61 KBOX 062338

Area Forecast Discussion
National Weather Service Boston/Norton MA
638 PM EST Wed Dec 6 2023

High pressure maintains dry weather late this week into early in the 
weekend with temperatures rising to above normal levels. A strong 
frontal system has the potential to bring a period of steady rain, 
gusty southerly winds and potential for coastal flooding along the 
southern coastlines later Sunday night and into early on Monday. 
Turning drier by Monday afternoon with a brief shot of colder air 
for Monday night, but temperatures look to rebound back closer to 
seasonable levels by next Tuesday and Wednesday.


630 PM Update: 

While there are still a couple general areas of enhanced
cloudiness - one in the lower CT Valley and the other across
Cape Cod - the trends in many areas per satellite and RH cross
sections is for decreasing cloudiness. Subfreezing temps are 
common across SNE early this evening, and while we expect some 
radiational cooling, it's not completely maximized as there 
looks to be enough of a NW wind around for the balance of the 
evening. In addition, while most areas should trend clear, ocean
effect stratocumulus clouds ongoing across Cape Cod as 
mentioned above look to linger for most of if not all of the 
overnight. Thus lows in the upper 20s/low 30s there but 
otherwise, most everywhere should see lows down in the low to 
mid 20s.

Previous discussion:

Light snow has all but ended for eastern MA and only lingering as a 
few hit and miss showers in western MA/CT this afternoon. As the mid 
level trough axis moves offshore this evening cold, dry NW winds 
continue to bring in a much below average airmass. Surface 
temperatures are expected to dip as low as the upper teens in the 
highest elevations, closer to the low 20s elsewhere across SNE.


Thursday mid level ridging to our west will direct continued cool NW 
flow into the region keeping temperatures on the cold side of 
normal. Highs won't top out higher than mid 30s Thursday afternoon 
with a mix of sun and clouds. While there's not much moisture to 
work with, a subtle shortwave and a layer of moisture at 700 mb will 
bring increasing mid level clouds during the day. By evening heights 
will be on the rise with the approaching ridge and moisture exits 
leaving a clear sky. Given that and calm winds with a surface high 
overhead, it should be a good radiational cooling night, taking lows 
into the low 20s and even upper teens in the typically coldest 



* Dry weather Fri thru Sat with warming temperatures to above normal 

* Strong frontal system around later Sun night/Mon could bring gusty 
  winds, period of steady rain/possible downpours, and possible 
  coastal flooding along the south facing coasts. Still some 
  uncertainty on the timing. Stay tuned! Well above normal temps Sun 
  and possibly into Mon.

* Brief shot of colder air Mon night but gradual rebound to 
  temperatures on Tue.


Friday through Saturday Night: 

Gradual warming trend remains indicated in this period as high 
pressure is anchored to our south allowing for warm advection and 
500 mb heights rise. Skies both Fri and Sat should feature mostly 
sunny to partly cloudy conditions with more clouds the further west 
one goes. Despite some clouds around, dry weather is still 
anticipated with modest SW breezes. Temps rise to around or just 
above seasonable levels on Fri with values in the mid/upper 40s for 
highs, and should reach well into the 40s to the lower 50s for Sat. 

Sunday into Monday: 

This period is the most active in the long-term portion of the 
forecast - and while there are still some smaller timing differences 
that will still need to be nailed down, most of the deterministic 
and ensemble model depictions seem to be keying on later Sunday 
night and into the first part of Mon as being the most active. We 
are expecting a strong frontal system coming out of the OH Valley 
and Appalachians to move through the Northeast in that timeframe. 
This anticipated storm system still has the potential to bring 
several weather-related concerns to Southern New England, including 
a period of steady rains/perhaps a rumble or two of thunder, breezy 
to gusty southerly winds, hazardous marine conditions and a 
potential for minor coastal flooding and possible beach erosion for 
south-facing coastlines.

While it is not well agreed upon across the model suite, there are 
some solutions which show the initiating 500 mb trough taking on a 
negative tilt around Sunday night and early on Mon as the system's 
surface cold front works its way through. Did note in response to 
this added potential for stronger synoptic-scale vertical motion, 
QPF amts in the GFS and ECMWF deterministic models were quite a bit 
higher. Deep layer moisture content also becomes elevated with PWAT 
standardized While there wasn't much in the way of convective 
instability, the meager amt there is could be augmented by the 
enhanced dynamic ascent to support a few rumbles of thunder along 
the frontal zone for the Sunday overnight period. Significant 
flooding problems are not expected but nuisance hydro issues could 
result from any clogged storm drains in the face of steady 
rains/local downpours. Frontal boundary looks to clear into the 
offshore waters by mid to late morning on Mon, but that too is 
subject to further fine tuning regarding timing. 

Southerly winds stand to be on the increase during the day on Sun, 
but the greatest potential for period of enhanced southerly gusts is 
later Sunday night and into early Mon just ahead of the frontal 
boundary. Models still depict a robust 925-850 mb southerly low 
level jet of 75 to 85 kt Sunday night along the southern and eastern 
coastlines. How much mixing we see is still unclear but potential 
exists for wind-related headlines on the southern and perhaps 
eastern coastal areas if we can realize enough mixing. Stronger 
southerly gusts over the water may support potential gale or perhaps 
storm force conditions over the waters for Sunday evening into Mon. 
Finally the strong southerly flow may lead to elevated storm surge 
for south coastal MA/RI and could bring the risk for coastal 
flooding concerns and/or beach erosion for those southern coastal 
RI/MA locations. While minor coastal flooding tends to occur more 
often, if peak surge values can coincide with high tide (slated for 
620 AM Mon AM at Providence) some coastal flooding could develop. 
Little if any notable coastal flooding concerns are likely on the 
eastern coast given southerly flow component.

Above normal temps are favored for this period, especially with the 
nighttime lows Sunday night. Highs Sunday should be well above mid-
December climo in the mid 50s to low 60s (climo is upper 30s to mid 
40s), with lows in the 40s to low 50s. Highs on Monday are more 
susceptible to frontal timing although above normal temps are still 
favored until frontal passage, and then temps then steadily fall 
upon frontal passage.

Monday Night and Tuesday: 

Rapid clearing takes place Mon night with strong cold advection 
setting shape for a chilly night, though not likely to be as cold as 
it could be given enough of a NW breeze. Dry conditions remain 
favored with lows in the 20s.

Dry weather continues into Tue with high pressure to our south. In 
addition, it looks as though colder air that moves in on Monday 
evening is brief with temps recovering around seasonable levels in 
the upper 30s to low 40s.


Forecast Confidence Levels:

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

00z TAF Update: 

Tonight: High confidence.

VFR for most, although BKN/OVC MVFR bases at times at HYA/ACK 
thru 02z Thu before trending BKN VFR. N winds around 5-10 kt,
with occasional gusts 18-22 kt over the Cape and Islands.

Thursday and Thursday night...High Confidence.

VFR. NNW winds becoming W 5-10 kts. Turning NW 5-10 kts on 
Thursday night. 

KBOS Terminal...High confidence in TAF. VFR. NNE winds initially
to trend NW around 10 kt by 02z Thu, remaining that way until
becoming a WNW around 6-8 kt around ~15-17z Thu.

KBDL Terminal...High confidence in TAF. VFR. Light NW winds will
trend W by Thu ~14-16z with increasing midlevel clouds.

Outlook /Friday through Monday/... 

Thursday Night through Saturday Night: VFR. 

Sunday: Mainly VFR, with local IFR possible. Windy with gusts
up to 35 kt. Chance RA.


Forecaster Confidence Levels:

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

High Confidence.

Low pressure tracking well southeast of the 40N/70W benchmark 
will continue to generate elevated winds and higher seas through
tonight. Expecting winds and seas to diminish by Thursday as
high pressure moves overhead Thursday and Thursday night. 

Outlook /Friday through Monday/...

Friday through Saturday Night: Winds less than 25 kt. 

Sunday: Low risk for gale force winds with gusts up to 35 kt.
Seas locally approaching 5 ft. Chance of rain.


KBOX is down due to a mechanical failure. Technicians will need
to assess before repairs can be completed. At this time there is
no estimate for return to service.


MARINE...Small Craft Advisory until 11 PM EST this evening for 
     Small Craft Advisory until 10 AM EST Thursday for ANZ254.
     Small Craft Advisory until 7 AM EST Thursday for ANZ255.


NEAR TERM...Loconto/BW
LONG TERM...Loconto

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