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Area forecast discussion 
National Weather Service Taunton Massachusetts 
111 PM EST Thursday Dec 4 2008 


Synopsis... 
a cold front will cross the region this afternoon and evening. Much 
colder weather will move in on Friday and continue into Monday. A 
low pressure system may graze southern New England with a touch of 
wintry weather late Saturday night into Sunday. Another low pressure 
should arrive toward the middle of next week. 


&& 


Near term /until 6 PM this evening/... 
leading edge of clouds moving into SW New Hampshire/west Massachusetts at 15z. Also noting a 
few light showers reaching ground into Berkshire County. Radar 
showing a batch of showers from near kafn-kore-kbaf into Litchfield 
County but not seeing anything reach ground. 


Have updated zones and grids to reflect temperatures a bit warmer than 
previously forecast...mainly over western areas. Have upped the maximum 
temperatures a few degrees. Also noting good mixing with winds picking up even 
over the land. Spotter reported wind gust to 46 miles per hour at around 10 am 
in Milford Massachusetts. Also note gust to 34 knots at kmqe. Have increased the 
wind a bit as well. At this point...feel the highest winds will 
occur through 18z then should start to diminish as clouds move in. 


See main batch of showers holding together across upper Hudson 
Valley into S central New York state late this morning...so feel that 
there will be a somewhat better shot of precipitation into western areas. 
Have increased probability of precipitation to chance for S New Hampshire/north central and west Massachusetts for this 
afternoon. Still agree with previous forecast and anticipate precipitation 
to tend to break apart as it moves into central and eastern areas by 
this evening. 


Expect front to approach western areas by 6 PM or so. 


&& 


Short term /6 PM this evening through Friday night/... 
tonight... 
the brief scattered light rain showers/sprinkles should move through 
the coastal plain during the evening. Otherwise...expect skies to 
become mostly clear to partly cloudy. Much colder air will be 
ushered in behind the cold front. Low temperatures should fall into 
the 20s across most locations...with lower 30s expected in downtown 
Boston/Providence. 


Friday... 
a partly sunny but much colder day is on tap for the region. Model 
cross sections indicate a bit of high cloudiness along with the 
formation of a fair amount of diurnal cumulus clouds across the 
interior during the afternoon. Can not even rule out a passing 
flurry or two across the east slopes of the Berkshires...but not 
Worth inserting into the forecast at this point. However...the main 
story will be a return to cold weather with 850 mb temperatures 
dropping to between -10c and -12c. Highs should only reach into the 
middle to upper 30s across the interior...to the lower 40s along the 
coastal plain. 


&& 


Long term /Saturday through Wednesday/... 
***uncertainty continues for Sat night - sun evening snow risk*** 


Draft at 107 PM...to be updated around 430pm. This is for evening 
media early view. The severe weather potential statement et cetera will fall out from this later today. 


Hazards... 
1/ "possible" wxa for snow southeast coastal mass and S coastal Rhode Island Sat night 
or sun. 


2/ "possible" Wind Advisory for Cape Cod and ack Sun night 


3/ possible southerly flow high wind/Wind Advisory situation for a portion of southern New England 
next Wednesday. 


4/ possible minor southerly flow coastal flooding buzz and narr Bay next 
Wednesday high tide. 


Details follow through 12z op runs as noted. 


Snow situation: models...both successive cycle same...and from within the 
international suite...have been variable on sharpness of digging short 
wave that eventually GOES negative tilt off the New England coast. NAM is 
drying out after its 18z and 00z cycles from yesterday and the 09z 
sref ensembles which offer 12 hour probs for 1 inch of snow through 
00z/Monday have only a 7 percent probability of 1 inch of snow pvd-owd-pym-ewb 
region and that is in the period ending 18z Sunday. 12z op GFS 
targets that region southeastward to cirrocumulus for 1-4 inches of snow but we have bl 
temperature problems that are far from being resolved. The suggestion here is 
that there will be some melting Sat night S coast. Also...low level 
inflow is weak and limited in duration. The 12z UKMET and ggem look dry. 


The 12z UK in particular is a decent model...and in my opinion recently 
more predictively stable and accurate when compared to the European model (ecmwf) through 
72 hours. 


Note that through 06z..the GFS ens mean quantitative precipitation forecast has backed to its original 
Tuesday Dec 2nd forecast of .2 for Cape Cod and the islands and less than 
that elsewhere. I do know for several cycles Wednesday the 3rd that it 
spread .2 back to the Berkshires and 0.4 to the mass coast. 


However...I think this mean quantitative precipitation forecast can be biased high if just a couple 
of members have large amounts...with most of the members light. That 
can happen if one or 2 members track much closer to the coast or are 
stronger with resultant heavier quantitative precipitation forecast. 


At this time snow growth looks good for several hours midday Sunday and thats 
when I think we could get an inch or 2 of MDT to heavy snow showers. 


12zgfs fgen while deep and organized...is weak...there is some instability... 
as seen in 850-500 6.5c/km lapse rates and divergence of q increase which 
pass through southern New England 18z Sunday! 


What I think will happen...instability flurries and snow showers interior 
and much of the coast Sat night or Sunday. We will look for a possible 
12 hour inverted trough focusing ocean effect somewhere in Rhode Island/southeast mass 
late Sat or early Sunday but there is bl shear and inflow is weak. 


Confidence as of this writing is average to above average that there will be 
any snowfall amount exceeding 2 inches in southern New England except "possible" 4 inch 
related ocean effect somewhere south of a pvc pym pvd line. Have 
been wrong before. We will look at this constantly the next several 
days. I just dont think there is enough digging soon enough...no 
confluence of importance for our area to our north and limited 
moisture inflow. Climatology for most Boston snows is around 1 inch. 
In my opinion...this system just does not fit a pattern for 
productive snow generation. 






Sun night...Wind Advisory mainly pvc and ack. Low probability at this time. 


Next Wednesday...noticed GFS for 3 cycles predicting near 100kt 850 mb winds 
somewhere in southern New England or along the southern New England coastal waters. Ec has fairly strong 
southerly flow as well. 7 days out and this could easily shear and break 
down so anything said here is of limited value. Tides are coming up... 
astronomically and surface pressure is modeled low with poor surge forecasts for 
Fox Point in southerly flow situations. For Plum Island on NE mass coast. 
Cant envision much of an erosion problem on strong southerly flow. 


&& 


Aviation /18z Thursday through Tuesday/... 
this afternoon...updated 1237pm 


18z tafs maintain VFR through period. 


Radar continued to indicate light rain showers with no visibility restriction 
moving into western New England at 1730z. These were moving NE and 
will slowly edge their way across region this afternoon and tonight 
as cold front moves through. Ceilings mostly 4-5kft at worst and only 
prime area for MVFR ceilings appears to be far northwest Massachusetts and SW New Hampshire per 
09z sref data. There is also a low probability of MVFR ceilings 
kfmh/khya/kack 06z-09z but confidence was not high enough to mention 
in tafs. 


Wind gusts will remain a concern through 20z across southeast Massachusetts with SW 
30kt gusts likely...though as thicker cloud cover arrives winds will 
diminish rapidly. Expect wind shift to west around 00z all terminals 
before veering to northwest 05z-08z as cold front moves through. 


Front will be offshore by 12z Friday with northwest winds at or below 10kt...backing 
to northwest Friday afternoon. 


Kbos terminal...widely scattered showers 22z-06z but no visibility 
restriction. SW winds diminish to 12g20kt by 20z and become west at or below 
10kt by 00z Friday. 






Friday and Friday night...VFR. 


Outlook...Friday night through Monday... 


Saturday...VFR. Low probability of MVFR conditions in scattered late 
afternoon snow or rain showers along the southeast coast. 


Saturday night into Sunday...periods of MVFR or IFR developing in 
snow or snow showers mainly Rhode Island and southeast Massachusetts airports. 


Sunday night into Monday...any lower ceilings/visibilities improve to VFR by 
morning. Wind gusts up to 38 knots possible late Sunday into Sunday 
night across Cape Cod and the islands. 


Tuesday...VFR day degrade MVFR or IFR at night in warm air advection rain. 


&& 


Marine... 
this afternoon...winds picking up with approach of cold front. Have 
kept gale gusts going for southern waters this afternoon. Note that 
buzm3 tower reported gusts to 37 knots at 15z. Also kept small crafts 
going on Boston Harbor...Narragansett Bay and the waters from 
Merrimack River to Plymouth. Note seas up to 7 feet at unh buoy well east 
of the Merrimack River. Appears low level jet will pass east of the 
waters by this evening. 


Tonight...winds will gradually turn northwest overnight behind the 
cold front. We still may see wind gusts in the low 20 knots with 
good mixing in the cold air advection pattern. Shorter fetch though 
should allow seas to slowly diminish...but we will continue to need 
headlines for our southern open waters for the remainder of the 
night. 


Friday...we should be able to remove all headlines by afternoon as 
high pressure gradually builds in from the west and left over seas 
diminish. However...20 knot wind gusts will remain possible with 
cold advection promoting good mixing over the ocean. 


Outlook...Friday night through Monday... 


Winds and seas diminish Friday night into Saturday as a high pressure 
crosses the waters. A coastal low pressure is expected to pass southeast 
of the waters Sunday. 


Sun...winds and seas will increase... with a Small Craft Advisory 
needed by Sunday night...with perhaps a gale for gusts. Winds and 
seas gradually diminish Monday as a high pressure builds across the 
waters. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Gale Warning until 3 PM EST this afternoon for anz231>235-237- 
254-255. 
Small Craft Advisory until 5 PM EST this afternoon for anz230- 
236-250. 


&& 


$$ 
Synopsis...Belk/Frank 
near term...evt 
short term...Frank/evt 
long term...drag/Belk 111pm 
aviation...drag/Frank/jwd 
marine...drag/Belk/Frank/evt 

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