Area forecast discussion 
National Weather Service Taunton Massachusetts 
307 PM EDT Wednesday may 16 2012 


Synopsis... 
scattered showers and a few thunderstorms are expected ahead of a 
cold front this and into this evening...mainly across western New 
England. The cold front will then bring dry weather from Thursday into 
the weekend along with a warming trend. Unsettled weather may 
return to southern New England early next week. 


&& 


Near term /until midnight tonight/... 
***a few strong to severe thunderstorms are possible across the 
interior late this afternoon/evening*** 


***severe thunderstorm watch is in effect for portions of northern 
Connecticut...western Massachusetts...and southern New Hampshire 
until 9 pm*** 


While the better subtropical axis has shifted offshore...focus now 
pertains to the west. Per Storm Prediction Center mesoanalysis...strong axis of SBCAPE 
up to 2000 j/kg extends from the middle-Atlantic through PA-New York into western 
portions of New England ahead of a cold front. The better shear 
environment /40-50 knots 0-6 km bulk shear/ lies upon and to the rear 
of the surface cold front presently extending from the Adirondack State 
Park in upstate New York southwestward into Youngstown Ohio. 


While thunderstorms are initiating within the warmer unstable 
thermal axis as westerly flow impinges upon higher terrain...the 
greater severe threat lies upon the surface cold front. The latest 
thinking is for western New England to gradually clear out...while 
locales along and east/S of the Worcester Hills will be under a surface 
inversion trapping low-level stratus and a more stable profile. 


Into the afternoon...the convective line is anticipated to become 
better organized. While isolated to scattered thunderstorms are 
definitely plausible through the western forecast area early on...the main 
convective line will likely swing into western New England around 6 
PM. Anticipate severe weather threats of small hail and damaging winds 
for those areas within the severe weather watch. Thunderstorms 
will weaken progressing eastward into the more stable airmass...likely 
becoming elevated. The nocturnal timing will likely aid in 
deterioration of the convective line through the forecast area. 
Thunderstorms are still possible into the early evening hours... 
especially those areas NE of the watch /se New Hampshire...NE MA/. 


Will be watching closely surface dewpoints and moisture availability. 
Areas to the west have mixed down drier dewpoints to the surface within 
the warm unstable sector. This can have impacts on lower the 
instability and resulting in high bases with oncoming storms. But 
keep in mind...large inverted-v soundings could yield a more 
significant wind damage threat. 


&& 


Short term /midnight tonight through Thursday night/... 
tonight... 


The cold front itself should be offshore after midnight by which 
point cooler and drier air advected by west/northwesterly flow will follow. 
There is the possibility for fog development along the S/southeast coast 
ahead of the cold front initially...likely to dissipate into the 
early morning hours as west/northwest flow brings in drier air at the surface. 
Should be a mild night moreso for the S/E...while north/west which will see 
clearing conditions after midnight into morning will fall into the 
middle 40s. 




Thursday and Thursday night... 


Northwest flow through the day with mostly clear conditions. Cant rule out 
some diurnal scattered cumulus...but the abundance of cooler and drier air 
pushing into the region will likely mix-down and mix-out the lower 
atmos. Low relative humidity values at the surface. May also see a few minor gusts 
around 15 miles per hour. 850 mb temperatures falling down to around +3c...so high temperatures 
into the low 70s is possible. Sea breezes anticipated near the waters 
due to the light west/northwest flow. Overnight...high pressure pushing across the 
region will lend to light winds and continued clear conditions. 
Nocturnal cooling likely. Temperatures to west Massachusetts into S New Hampshire should fall into 
the middle 30s so frost will be possible...with low- middle 40s elsewhere. 
Frost headlines may be necessary. 


&& 


Long term /Friday through Wednesday/... 


Highlights... 


* dry with moderating temperatures through sun 
* showers possible Monday into Wednesday 


Will be brief given the expected convection this afternoon and 
evening across western New England. Nice weather remains in the 
forecast from Friday into the weekend as low amplitude middle level 
troughing over the northeast Friday is replaced by building middle level 
ridge over the Ohio Valley and eventually the northeast this weekend. 
This will provide large scale subsidence over southern New England 
yielding dry weather along with warm may sunshine. Expect mild days 
and cool nights with highs in the 70s to near 80 inland Sat and sun. 
Seabreezes expected all three days given proximity of high pressure and 
associated light pgrad. Thus cooler along the immediate shore. 
Nonetheless nice may-like weather expected. 


By next week forecast confidence decreases rapidly as models differ 
on the magnitude of troughing left behind over the Gulf states and 
the evolution of this trough potentially up the eastern Seaboard. At 
84 hours the 12z GFS doesn/T have support from the 12z NAM/00z European model (ecmwf) 
and UKMET...which all have more troughing over the Gulf states than 
the 12z GFS. Thereafter the 00z European model (ecmwf) and now the new 12z UKMET both 
indicate a middle level trough or closed low potentially coming up the 
eastern Seaboard in response to building western Atlantic ridge. The GFS 
only offers a frontal passage around the Tuesday timeframe. Forecast 
confidence is below average here given the time range and model 
spread but given the UKMET and the European model (ecmwf) are close...we will follow 
a non-GFS solution here with chance probability of precipitation from Monday into Wednesday. This is 
close to our previous forecast as well. 


In addition did bring highs down a notch Monday-Wednesday given potential 
cloud cover and precipitation along with onshore flow. Blended the 2 meter 
temperatures from the European model (ecmwf) to accomplish this. Overall not much change 
from our previous forecast. 


&& 


Aviation /19z Wednesday through Monday/... 
forecaster confidence levels... 
low...less than 30 percent 
moderate...30 percent to 60 percent 
high...greater than 60 percent 


Overview... 
moderate to high confidence in tafs. MVFR low clouds are expected 
to linger over the eastern two-thirds of New England...where to the west 
there is a definite convective threat. Thunderstorms in the vicinity due to uncertainty of 
the evolution of the convective threat. Terminals through the CT valley 
should be aware of lightning...with possible damaging winds and small 
hail. Any storms will yield tempo MVFR/IFR impacts. The threat 
looks to impact around 0z. Thereafter...cold front swings through the 
terminals after midnight ushering clearing through the region. May see 
fog along the S/East Coast...uncertain. Into the remainder of the 
forecast thereafter...high confidence VFR with northwest winds. 


Kbos taf... 
moderate to high confidence. Feel low clouds will hang and limit 
thunder chances to none. Ushered vcsh around the time of cold frontal 
passage but feel convective threat will be diminished. Improving 
thereafter to VFR with northwest flow. 


Kbdl taf... 
moderate to high confidence. Am confident a convective threat is 
poised upon the terminal around 0z. Exact specifics remain 
uncertain. Should thunderstorms and rain impact...anticipate MVFR/IFR impacts with 
lightning and possible damaging winds and strong hail. Will update as 
the convective threat becomes closer. Improving into the evening... 
VFR with northwest flow. 


Outlook... 


Friday through Monday...high confidence for VFR and dry weather. Monday...low 
confidence. VFR to start but possibly lowering to MVFR in showers. 


&& 


Marine... 
moderate to high confidence. Modest S/southwesterly winds gusting to 25 kts 
will continue swell and high seas over the outer waters...with 6-8 
feet S and east of Rhode Island out to Cape Cod and the islands. Cold front should 
be across the waters during the early morning hours followed by weaker 
west/northwesterly flow. May be some gusts around 15 kts...but not considering 
anything greater. Showers...and fog will be possible down to a half to 
quarter mile...for the S/southeast waters overnight and prior to the passage 
of the cold front. Seas to diminish by late Thursday allowing small 
craft advection to drop. 




Outlook...Friday through Monday 


Pleasant boating weather Friday through sun with high pressure over 
southern New England. Only wrinkle could be some modest southeast swells on 
the ocean waters from low pressure southeast of New England Sat and sun. 
Forecast confidence decreases next week as the magnitude and track 
of this low becomes uncertain. 




&& 


Equipment... 
buoy 44013 in mass Bay will be returned to service around June 
19th...pending weather conditions. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Small Craft Advisory until 9 am EDT Thursday for anz235-237. 
Small Craft Advisory until 3 PM EDT Thursday for anz250-256. 
Small Craft Advisory until 9 PM EDT Thursday for anz254-255. 


&& 


$$ 
Synopsis...nocera/sipprell 
near term...sipprell 
short term...sipprell 
long term...nocera 
aviation...nocera/sipprell 
marine...nocera/sipprell 
equipment...Willie