307 
fxus61 kbox 230946 
afdbox 


Area forecast discussion 
National Weather Service Taunton Massachusetts 
446 am EST Monday Nov 23 2009 


Synopsis... 
low pressure along the Carolina coasts today will pass east of Cape Cod 
late Tuesday...possibly as a gale noreaster. Weak high pressure covers 
New England Wednesday. A large gale will be centered near the New 
England coast Friday then move into the Maritimes this weekend 


&& 


Near term /until 6 PM this evening/... 
as high pressure pushes toward Nova Scotia overnight...low ocean clouds 
continue to push westward. Fog satellite product shows the edge of 
these clouds all the way to the Berkshires and central Long Island 
at 04z. May see a few breaks in the clouds that may work ashore 
across the S coast...Cape Cod and the islands...but more clouds 
will work north overnight. Noting some radar returns on the NE mosaic 
radar...but remains well S of Nantucket and Long Island for now. 


Noted that temperatures were milder where the clouds had already reached... 
with cooler readings across north central Massachusetts/S New Hampshire where skies were 
mainly clear. However...as the clouds have continued to push in... 
expect temperatures to either remain steady or slowly rise overnight where 
skies started off clear. NE winds will also slowly increase across 
the cape and islands. 


Have updated the grids and zones to reflect current conditions... 
along with adjustments to reflect current thinking. 


&& 


Short term /6 PM this evening through 6 PM Tuesday/... 
still some uncertainty with the track and intensity of a low 
pressure moving northeast from the middle Atlantic coast Monday night. 
For now...used a blend of the GFS and NAM to minimize forecast 
error. 22/15z sref mean is even slower and weaker and slower than 
that solution. 


Most 22/12z models bring some rainfall to southern New England 
during the day Monday...especially during the afternoon. Given the 
uncertainty in the model timing...did trend the arrival of this 
precipitation faster than previous forecast. Thinking the best 
chance for the arrival of this rain will be Monday night. 


Used a blend of the mav/met guidance once more for temperatures 
during this portion of the forecast. 


&& 


Long term /Tuesday night through Sunday/... 
Tuesday...low pressure center probably near/south of Nantucket 12z 
Tuesday then tracks gradually northeastward towards Nova Scotia. NAM is 
a bit weaker and further inland than the other models...taking low 
over the cape. For this package generally leaned towards the 
GFS/ECMWF/ggem. Started off with chance probability of precipitation over the interior... 
but still opted to go with likely near the coast. Low level 
moisture should keep clouds around through the day. 


Tuesday night/Wednesday...low pressure continues to move further 
North/East of the area...being replaced by weak high pressure. NAM 
indicates a layer of low level moisture just deep enough to keep 
clouds around for these 2 periods...GFS much drier. Think that at 
least some low level moisture will linger...and middle/high clouds 
possible with a short wave. So kept partly to mostly cloudy skies in 
forecast. But low level moisture layer likely too thin for 
measurable precipitation. Temperatures are a blend of MOS. Continued with 
previous thinking that Wednesday will be cool and raw during the afternoon 
with onshore flow. 


Wednesday night through Thanksgiving...mostly cloudy skies/chance 
probability of precipitation due to combination of low level moisture from easterly flow as 
high pressure departs...and as low pressure develops off the 
Carolina coast. 


Thursday night through Friday night...went with HPC guidance for 
this period with a vigorous low pressure system potentially 
affecting our area. Model discrepancies exist...as European model (ecmwf) and GFS 
show surface low tracking over southern New England but ggem keeps 
center well to the south and east. But at this time high chance to 
likely probability of precipitation seem prudent for Thursday night through Friday. Possibility that 
precipitation could end as a light rain/snow mix Friday night in interior as 
colder air spills into the area. 


Saturday...potential for blustery and chilly weather as tight 
gradient lingers while surface low pulls to the northeast. Both 
European model (ecmwf) and GFS indicate a cold pool aloft and lingering moisture 
which could potentially lend itself to some showers. 1000-500 mb 
thickness are quite low...if this scenario pans out can/T rule out 
some snow showers in the far interior...but it would be too warm at 
the surface for any accumulation. 


Sunday...high pressure with below normal temperatures. 


&& 


Aviation /10z Monday through Friday/... 
overnight...MVFR ceilings across most areas...though some breaks in the 
overcast noted across the cape and islands. Expect the MVFR ceilings to 
continue...though visibilities will continue at VFR. 


Monday...MVFR-IFR ceilings continue for most areas. Local IFR ceilings along 
the S coast...Cape Cod and the islands during the afternoon. Patchy 
rain will approach north CT/RI/se Massachusetts during the afternoon with local 
MVFR visibilities. 


Monday night...MVFR ceilings...lowering to IFR eastern sections. Areas 
of MVFR/IFR visibilities in rain and fog...also mainly eastern sections. 


Outlook /Tuesday through Friday/... 


Tuesday...MVFR with areas of IFR in low clouds and scattered showers. 


Tuesday night through Thursday...MVFR-IFR conditions may linger in low 
clouds through this period. May have areas of drizzle and fog 
developing later Wednesday/Wednesday night. 


Thursday night and Friday...low to medium confidence of IFR ceilings and 
visibilities in showers. 


&& 


Marine... 
overnight...E-NE winds continue...with gusts up to 25-30 knots. Noted 
the Ferry on the Nantucket Sound crossing had gusts to 30 knots with 
seas up to 4 feet. Brought the small crafts up for the S sounds 
through the overnight as seas will continue to build. 


Low pressure moving northeast from the middle Atlantic coast Monday and 
Monday night will likely increase winds during this time as well. 
Small craft advisories continue for most waters. 


Outlook /Tuesday through Friday/... 


Tuesday and Tuesday night...Small Craft Advisory winds/seas linger Tuesday as low pressure 
tracks towards Nova Scotia. Winds diminish Tuesday night and Wednesday but 
seas will be slower to subside. 


Wednesday through Friday...persistent easterly winds will likely 
cause seas to remain above Small Craft Advisory thresholds across the outer waters. 
Winds and seas should increase Thanksgiving night and Friday in 
advance of the next system approaching from the south. Possibility 
of gales Friday. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...gale watch from late tonight through Tuesday afternoon for 
anz232-254-255. 
Small Craft Advisory until 1 am EST Tuesday for anz232-254>256. 
Small Craft Advisory until 1 PM EST Tuesday for anz233>235. 
Small Craft Advisory from 7 am to 1 PM EST Tuesday for anz230- 
236. 
Gale watch from Tuesday morning through Tuesday afternoon for 
anz231-250. 
Small Craft Advisory from 1 am to 7 am EST Tuesday for anz231. 
Small Craft Advisory until 1 PM EST Tuesday for anz237. 
Small Craft Advisory until 7 am EST Tuesday for anz250. 
Small Craft Advisory from 1 am to 1 PM EST Tuesday for anz251. 
Gale watch from late tonight through Tuesday morning for 
anz256. 


&& 


$$ 
Synopsis...drag/evt 446a 
near term...evt 
short term...evt 
long term...drag 
aviation...drag/evt 
marine...drag/evt 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)