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Area forecast discussion 
National Weather Service Taunton Massachusetts 
707 PM EST Tuesday Feb 9 2010 


Synopsis... 
a rapidly intensifying coastal storm will bring significant snow and 
strong winds to portions of southern New England...with areas along 
and south of the mass Turnpike most at risk for substantial amounts. 
High pressure then brings dry and seasonably cold weather Thursday 
into this weekend. Another low pressure may swiftly pass US 
sometime Sunday night into Monday night. 


&& 


Near term /until 6 am Wednesday morning/... 
middle and high clouds overspread the region tonight in advance of Ohio 
Valley low. Good model agreement on precipitation arrival time around 12z 
Wednesday across western Massachusetts and western CT. Otherwise expect a dry night 
with seasonably cold temperatures along with very light winds. 


No major changes early this evening...just updated temperature and 
dew points per latest observed trends. Also tweaked winds early this 
evening. 


&& 


Short term /6 am Wednesday morning through Wednesday night/... 
looking at the model suite...appears to be two camps for the 
upcoming storm beginning around middle morning Wednesday and continuing 
through around midnight Wednesday night. Seeing this mornings NAM 
gave US pause seeing how it pushed the developing low further north and 
passing it close to the benchmark Wednesday night...along with its banding 
features. The 12z GFS and UKMET were close to this solution. 
However...the two Canadian models as well as the European model (ecmwf) kept the low 
passing further S than the other models as well as their packages of 
quantitative precipitation forecast and a sharp northern edge. 


Already seeing area of c/g lightning off the Carolina coast at 
18z...so it looks like the low is starting to develop in that 
region. Considering the setup over Quebec and the explosive 
development that this low will undergo over the next 24 hours as 
well as the excellent moisture inflow...felt that the further north 
solution was more prudent...especially considering the banding 
features that both the NAM and GFS exhibited. One disconcerting 
note to these models was the amount of warm air intrusion from the 
ocean...which would cut back on snow amounts especially at the 
onset of the storm along the coast. It does look like S coastal 
areas as well as coastal Plymouth County will start off with a mix 
or even all rain. However...as the low deepens and wraps the cold 
air back around...should see a change to heavy...wet snow especially 
on the cape and islands Wednesday night. 


Appears to be enough quantitative precipitation forecast and banding to give most areas warning 
criteria snowfall with the heaviest amounts across north CT/north Rhode Island into 
interior southeast Massachusetts. Based on our forecast this afternoon...have issued a 
Winter Storm Warning from near the Mass Pike southward for Wednesday until 
around midnight or so Wednesday night. While we feel that the snow will 
make it all the way northward to Route 2 and into southern New 
Hampshire...the question of maximum quantitative precipitation forecast placement and low track raised 
by the European model (ecmwf)...ggem and rgem...decided to hold off on issuing the 
warning for those areas to see if later model runs help clear up 
this issue. 


The other concern is the winds picking up along the coast. Models 
are still indicating a very strong low level jet...on the order of 
50-55 knots at 925 hpa...moving across S coastal areas late Wednesday 
afternoon and Wednesday night. Felt the best shot of 55-60 miles per hour gusts will 
occur on Cape Cod and the islands...so issued the High Wind Warning 
for those areas. Along the remainder of the coast...will likely see 
advisory level winds but this is covered under the Winter Storm 
Watch/warning already issued. 


The last question will be whether conditions could reach blizzard 
criteria. We discussed this...and felt that due to the heavy nature 
of the snow even in some of the likely snow bands...it would be 
difficult for visibilities to lower below 1/4 mile so we did not go with 
blizzard warnings. It will be close in some areas mainly early Wednesday 
night...but will probably not quite make it. 


Daytime highs Wednesday will reach the middle to upper 30s along the 
coast...but will start to drop by around midday as colder air wraps 
in around the low. Overnight lows will fall to the 20s to around 30 
with some upper teens across the east slopes of the Berkshires. 


&& 


Long term /Thursday through Tuesday/... 
this portion of the forecast starts out with the departure of the 
noreaster Thursday. Cyclonic curvature and a little bit of cold air 
advection could result in scattered ocean-effect snow showers across 
the Outer Cape and Nantucket. The problem will be the winds... 
which are likely to be too strong to allow such a snow band to 
develop. Will need to monitor this...as the forecast is mainly dry 
Thursday afternoon into Thursday night. 


Winds diminish and become more northwest Thursday night into 
Friday. This should be a relatively tranquil period heading into 
Sunday with below normal temperatures. 


The next potential snowfall looks to be sometime Sunday night into 
Monday night. Expecting a quick-mover...which would limit 
accumulation potential. Timing with this system is still very 
uncertain. 09/12z GFS slightly lags the European model (ecmwf). Leaned toward the 
GFS for now which was in slightly better agreement with previous 
forecast. 


&& 


Aviation /00z Wednesday through Sunday/... 
tonight... 
VFR to start with MVFR ceilings entering bdl/baf late. Snow may 
approach bdl/baf toward 12z. Elsewhere...snow should hold off till 
after 12z. 


Wednesday... 
moderate to high confidence on LIFR conditions 18z-00z from bdl-orh- 
bos and points south in heavy snow with visibilities 1/2 mile or less...strong 
east- northeast winds and snowfall rates of 1-2 inches possible. 
North of this line including mht higher probability of MVFR possibly 
lowering to IFR in snow. LIFR conditions may enter bdl/baf as early 
as 15z- 18z. Moderate to high confidence for issuance of aviation 
weather warnings for strong winds and low visibilities Rhode Island airports as well 
as Logan Wednesday afternoon. 


Wednesday night... 
high confidence in IFR conditions in snow across most terminals... 
but conditions across mht are more uncertain. Northeast wind gusts 
of 35 to 45 knots are possible across the coastal terminals... 
possibly up to 50 knots over the cape and islands. Aviation weather 
warnings likely to continue overnight. 




Outlook...Thursday through Sunday... 


Thursday...expect conditions to improve to VFR across most locations 
by early to middle morning...with the possible exception of khya and 
kack. 


Friday into Sunday...high confidence for VFR. 


&& 


Marine... 
tonight...W-NW winds mainly at 10 knots or less will shift to easterly 
late at night and begin to increase across the southern outer 
waters. 


Wednesday and Wednesday night...as low pressure rapidly develops S of 
New England and pushes near 40n latitude...expect east-NE winds to 
quickly increase to gale force Wednesday afternoon...then some storm force 
gusts on the outer waters mainly near and S of Cape Cod and the S 
coast where the strong low level jet passes. Have issued a Storm 
Warning for those areas and gales elsewhere. 


Used the swam NAM wave model guidance as seas will build close to 20 
feet east of Cape Cod and Nantucket...may even see the seas build to over 
10 feet on the upper portion of Cape Cod Bay as winds back to north Wednesday 
night. 


Outlook...Thursday through Sunday... 
north to northwest gale force wind gusts should diminish by late 
Thursday morning or afternoon...but Small Craft Advisory winds 
continue. Winds continue to diminish Thursday night into Friday... 
but rough seas are likely to continue across the outer coastal 
waters into Saturday. There is the possibility of rough seas and 
wind gusts up to 25-30 knots Saturday night into Sunday. 


&& 


Tides/coastal flooding... 
tides will peak at 2-2.5 feet above normal across the eastern Massachusetts coast 
Wednesday night into Thursday morning with 20+ feet seas developing just offshore 
by late Wednesday night. No problems are anticipated during the Wednesday evening 
high tide as this is a low astro tide and seas will just be in the 
process of ramping up. The Thursday morning high tide is higher and 
although winds will be shifting to the N/NW...a storm surge of 2 feet 
and 15-20 feet seas could result in some minor coastal flooding as a 
worst case scenario...particularly from the Outer Cape to ack where 
the highest seas will be. 


&& 


Box watches/warnings/advisories... 
CT...Winter Storm Warning from 8 am Wednesday to 1 am EST Thursday 
for ctz002>004. 
Massachusetts...Winter Storm Watch from Wednesday morning through late 
Wednesday night for maz002>008-010-014-026. 
Winter Storm Warning from 8 am Wednesday to 1 am EST Thursday 
for maz009-011>013-015>024. 
High Wind Warning from 4 PM Wednesday to 7 am EST Thursday for 
maz022>024. 
New Hampshire...Winter Storm Watch from Wednesday morning through late 
Wednesday night for nhz011-012-015. 
Rhode Island...Winter Storm Warning from 8 am Wednesday to 1 am EST Thursday 
for riz001>008. 
Marine...Storm Warning from 4 PM Wednesday to 5 am EST Thursday for 
anz231-232-250-254>256. 
Gale Warning from 1 PM Wednesday to 5 am EST Thursday for 
anz230-233>237-251. 


&& 


$$ 
Synopsis...Belk 
near term...nocera/Belk 
short term...evt 
long term...Belk 
aviation...nocera/Belk/evt 
marine...Belk/evt 
tides/coastal flooding... 

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