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Area forecast discussion 
National Weather Service Taunton Massachusetts 
211 PM EST Thursday Nov 5 2009 


Synopsis... 
low pressure developing well S of Nantucket will steadily intensify 
in its trek to the S of Nova Scotia Friday. Large high pressure settles 
across the middle Atlantic coast this weekend...moving slowly out to sea 
early next week. A cold front moving east from the Ohio Valley may 
stall along the East Coast during the middle of next week. 


&& 


Near term /until 6 PM this evening/... 
made minor adjustments to temperatures and dewpoints to account for 
the latest trends. With increasing cloud cover through the early 
afternoon have opted to lower highs a degree or two in many 
locations. 


Latest radar imagery shows increasing showers across much of 
southern New England but particularly from Jaffrey New Hampshire to Worcester Massachusetts 
to Willimantic CT eastward. These showers are associated with an 
approaching shortwave. With weak low level convergence...kept chance 
probability of precipitation. 


&& 


Short term /6 PM this evening through 6 PM Friday/... 
tonight...a second more impressive short wave approaches from the 
Great Lakes region. This allows for the long wave trough to become 
more negatively tilted with an inverted trough axis extending 
northwest across the area. However phasing of subtropical moisture 
occurs too late as deeper moisture remains southeast of New England. 


The trend has been for a more progressive solution with low pressure 
developing further offshore. Therefore favored the more progressive 
00z GFS/European model (ecmwf) solutions versus the slower NAM which appears to be an 
outlier. 


Have included chance probability of precipitation as the 500 mb-7 upper level trough axes cross 
the region overnight. Vertical cross sections do not look favorably 
moist except along the southeast coast. Scattered rain showers should 
mix with and change to snow across much of the interior as 
temperatures cool aloft. Boundary layer temperatures remain 
generally too warm to support snow along the immediate coastline. 
Brief banding of precipitation could occur as the offshore low 
intensifies...though not well depicted at this time. Little if any 
wet snow accumulation is expected. 


Friday...brisk northerly flow expected. Leftover early morning 
showers will be possible across the Outer Cape and islands as the 
trough departs. Otherwise clearing is expected. Most of the region 
will experience high temperatures at least 5 degrees below normal. 


&& 


Long term /Friday night through Wednesday/... 
this portion of the forecast looks to be relatively tranquil with a 
modest East Coast middle level ridge through early next week. Models 
agree on the arrival of a middle level shortwave toward the middle of 
next week...but the cannot agree on its timing and amplitude. This is 
not uncommon for this time range. 


Building East Coast ridge should lead to a warming trend through 
early next week. A weak cool front is expected to cross southern New 
England early Sunday...but it is moisture-starved so it should not 
have much clouds or precipitation. Full sunshine should mitigate the 
shallow colder air it sends our way. This front is so weak...not 
expecting winds to shift northwest...which will also help to warm 
things up. 


Monday looks to be the warmest day of this period with south to 
southwest winds and plenty of sunshine. Tuesday could also be 
warm...but the uncertainty in the evolution of the middle level flow is 
resulting in significant timing issues for a cold front approaching 
our region. Currently thinking this front will arrive Tuesday 
night...so kept temperatures warmer on Tuesday but a bit below Monday 
in case there are more clouds. This front seems to be lacking 
abundant moisture as well...so just have some clouds int he forecast 
for now. 


&& 


Aviation /19z Thursday through Tuesday/... 
through tonight...VFR ceilings with scattered light showers causing patches 
MVFR ceilings. 


Model choice: the 12z rgem/NAM are almost spot on regarding heaviest 
shower development southeast mass midday today in our County Warning Area but Imo...missing 
the widespread convectively driven traces elsewhere. Have followed these 
two models closely through 18z Friday regarding the bands of significant 
measurable showers. These showers...partly driven by steep moist 
lapse rates with lift provided by modeled fgen/-epv in New York state. 


Suggest watch the eastward progression of the New York state band through the afternoon...then 
slow down in its entrance across SW New England as the 700 mb flow 
turns from west-southwest to northwest. 


My expectation is that afternoon scattered showers generally reduce near sunset 
all of the County Warning Area except the potent band of MDT to heavy showers expected 
from northwest Massachusetts to east CT or west Rhode Island during the 01z to 07z time frame. That band 
of showers could force snow levels to drop to 300 feet in heavier 
precipitation...about an hour or 2 after the heavy showers arrive. Snowgrowth looks 
excellent and only the warm bl prevents an hour or 2 of heavy wet snow 
reaching the ground. Of interest are tt over 58 /in some case near 62/ in 
this band...some weak cape and swi near 0. Would not at all be surprised 
at thunder in CT in the 02z to 04z time frame. Best chance of snow is 
baf/bdl due to their being in the proximity of the heaviest modeled showers. 
However...if this band ends up further east...then orh could rcv 1/2 
inch of wet snow in an hours time. 


Friday...VFR. North-northwest wind gusts 22-32 kts throughout....especially 
midday/aftn. SC ceilings between 3000 and 4500 feet expected between 15z 
and 20z. One exception... kfmh khya and kack may see a brief period of 
MVFR conds in showers during middle or late Friday morning as the showers 
occurring throughout Maine and east New Hampshire this afternoon...shift from a north-northeast 
movement to a south-southwest movement then S in the reorienting middle level flow as 
the sharp trough aloft passes east of our longitude. 


Friday night...generally VFR. 


Outlook /Friday night through Monday/... 


Generally VFR. Patchy IFR in valley fog and stratus during the early 
morning hours each night. 


&& 


Marine... 
today...winds and seas expected to remain below Small Craft Advisory 
criteria. 


Tonight...a Small Craft Advisory has been posted across all of the 
waters. NE winds gusting to 20 to 30 knots as low pressure intensifies 
offshore allowing the pressure gradient to increase. Seas building 
to 4 to 6 feet late across the outer waters. 


Friday...a Small Craft Advisory continues for all of the waters. Seas 
building to 5 to 9 feet. North winds 20 to 30 knots. Scattered gale force wind 
gusts to 35 knots possible. 


Outlook /Friday night through Monday/... 


Small Craft Advisory may be needed Friday night into Saturday 
depending on how quickly seas subside from an offshore low pressure. 
Main area of concern would be the outer coastal waters east of Massachusetts. 
Could also see a brief period of wind gusts up to 25 knots Sunday 
morning as a weak cool front moves across the waters. 


&& 


Tides/coastal flooding... 
latest indications are the threat of coastal flooding is diminishing. 
Some splashover is possible during the Friday afternoon high tide. 
Some beach erosion is possible as well...especially across Cape Cod. 


&& 


Equipment... 
two of our National oceanic and atmospheric administration weather radio all hazards transmitters are down... 
Soapstone Connecticut /which covers NE CT and portions of SW Massachusetts/ and 
Camp Edwards Massachusetts /which covers portions of southeast Massachusetts including 
the cape and islands/. This appears to be a phone line problem and 
verizon has been notified. As of this time there is no estimated time 
for return to service. Look for additional updates in this product 
throughout the day. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Small Craft Advisory from 4 am to 7 PM EST Friday for 
anz230>237-250-251-254>256. 


&& 


$$ 
Synopsis...Belk/Strauss 
near term...Strauss/rlg 
short term...Strauss 
long term...Belk 
aviation...drag/Belk 210p 
marine...Belk/Strauss 
tides/coastal flooding... 
equipment... 

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