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


Synopsis... 
a cold front will cross the region this 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 am Friday morning/... 
appears that the cold front is just starting to enter New England 
out of New York state at 20z. Steady light rain has moved into the 
Berkshires with a few showers from near kore to kfit. 


As precipitation moves into the region...best upper level support runs out 
ahead of it so expect continued trend of dissipating showers to 
continue. Already noting this trend on NE radar mosaic. Have a brief 
likely period of showers over SW New Hampshire/northwest Massachusetts early this evening... 
otherwise will see scattered showers push across the region tonight. 
Will be on light side with best shot of measurable precipitation over 
central and western areas. Expect less than 0.1" with this feature. 
Also expect precipitation to push off the Cape Cod coast by around midnight. 


Still noting wind gusts to 25 knots or so over Cape Cod and the 
islands...otherwise appears that the core of the low level jet has 
pushed east. Expect winds to continue to diminish as they shift to 
west tonight. 


Models indicating good shot of cold air working into the region. 850 mb 
temperatures drop -6c to -11c by 12z Friday. Used blend of mavmos guidance 
and metnam for overnight lows...which will mainly be in the 20s. 


&& 


Short term /6 am Friday morning through Friday night/... 
Friday... 
cold air advection continues through most of the day...though 
appears that the core remains over northern New England. 850 mb temperatures 
will still be on order of -10c to -12c. So...will see some diurnal 
clouds developing. Otherwise...expect a dry day with temperatures running 
at least 5 degrees below normal. High pressure ridge builds out of the Ohio 
Valley. 


Friday night... 
high pressure remains in control. Models start to show development of 
low pressure off the southeast U.S. May see some precipitation develop well offshore 
late at night. Otherwise...expect another dry and chilly night. 
Overnight lows mainly in the teens...except 20s along the immediate 
coast. 


&& 


Long term /Saturday through Thursday/... 
***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 /21z 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... 
tonight...winds will continue to diminish. Will see gusts to 25 knots 
this evening mainly on the eastern waters as winds shift to west. 
Seas will remain high...upwards to 10 feet on the southern outer 
waters early...but will slowly subside. Continued Small Craft 
Advisory through tonight for all waters except Boston Harbor and 
Narragansett Bay. May be able to discontinue for the south sounds 
and bays earlier depending upon how quickly seas subside. 


Friday...may need to continue a small craft for seas on the outer 
waters for leftover 5-6 feet seas. Otherwise...expect west-northwest winds at 15 
knots or less. 


Friday night...as high pressure center builds west of the waters...west winds 
will be at 15 knots or less. Seas will be 3 feet or less. Depending upon 
timing of high...winds may start to shift to SW after midnight west 
of Marthas Vineyard. 


Outlook...Saturday through Tuesday... 


Winds and seas below small craft criteria 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...Small Craft Advisory until 5 am EST Friday for anz231>235- 
237-250-254-255. 


&& 


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

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