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Area forecast discussion 
National Weather Service Taunton Massachusetts 
200 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/... 
clouds have moved into most areas early this afternoon. However... 
winds remain a problem along the South Coast of Rhode Island/southeast Massachusetts. Have 
received some calls about gusts 30-35 miles per hour in Westport and Dartmouth 
areas...which was verified by ASOS at kewb with gusts to 34 knots at 
18z. Previously thought that winds will diminish quickly as clouds 
arrived...but appears to be hanging on with low level jet in 
vicinity. 


Updated zones and grids to reflect higher winds over southeast Massachusetts/Rhode Island and 
the cape areas. Also noted temperatures were not rising as quickly over the 
CT valley into S New Hampshire...so adjusted those as well. Still expect winds 
to diminish rather quickly...but delayed until around sunset. 


Kept same timing for precipitation into the region...as leading edge moving 
into the Berkshires on NE regional mosaic radar. 


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. 


12z GFS 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 /19z 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 158 PM 
short term...Frank/evt 
long term...drag/Belk 111 PM 
aviation...drag/jwd 111 PM 
marine...drag/Belk/Frank/evt 

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