691 
fxus61 kbox 091024 
afdbox 


Area forecast discussion 
National Weather Service Taunton Massachusetts 
524 am EST Friday Jan 9 2009 


Synopsis... 
high pressure from the eastern Great Lakes to Middle Atlantic States will drift 
to the northeast and become centered over the St Lawrence River 
valley late Sat. The next winter storm will move out of the Ohio 
Valley Sat. The storm will pass south of the southern New England 
coast late Sat night and early sun. High pressure builds overhead 
Monday. Low pressure swings a cold front through on Tuesday. High pressure will 
bring dry and cold weather Wednesday. Another weak low will pass S of New 
England Thursday. 


&& 


Near term /until 11 am this morning/... 
winds should continue to diminish during the early morning hours and 
then begin to increase again with mixing in the late morning. Some 
orographic cloudiness spilling over the Berkshire crest and across 
the Monadnocks. Skies should become mostly clear all areas east of the 
Berkshires by middle or late morning. 


&& 


Short term /11 am this morning through 6 PM Saturday/... 
this looks to be the quiet before the storm. West to northwest gradient tight 
enough for brisk winds gusting to near 25 knots most land and ocean 
areas today...dropping off over land tonight...but diminishing more 
slowly over the water. Have gone close to mavmos temperatures for today but 
lowered a few degrees to be closer to NAM 2 M temperatures tonight. Believe 
winds will eventually decouple most interior areas late at night and 
under clear skies and snow cover inclined to go a little than the 
statistical guidance. 


Have depicted increasing clouds Sat and relatively light winds. 
Stayed close or just slightly lower than mavmos temperatures. Brought 
chance probability of precipitation into SW zones around middle afternoon. This seems to fit with 
a blend of faster GFS and slower NAM or fairly close to Canadian Gem 
timing which we like and was favored in the pmdhmd. We also note that 
the operational NAM and GFS 00z runs show convergence toward the 
approaching surface low track. 


&& 


Long term /Saturday night through Thursday/... 
***plowable snow expected Saturday night into Sunday for all of 
southern New England. Highest amounts expected south of the Mass 
Pike.*** 


Our main focus this morning has been on the potential for a storm 
Saturday night into Sunday which will bring up to 5-10 inches of 
snow to much of southern New England. The models have come to more 
of an agreement on the track and to an extent the timing of this 
clipper type low. The low is expected to track out of West Virginia 
through the middle-Atlantic south of Long Island and across the 40/70 
benchmark before heading out to sea. Both the 08/12z and 09/00z 
European model (ecmwf) have a more northern track for this system. While we can not 
completely rule this scenario out...these solutions lay north of the 
rest of the operational models as well as the GFS/sref ensembles. 
For timing of this system we used a blend of the faster GFS and 
slower NAM with the result looking similar to the Canadian Gem 
timing. In the end...all this means is a winter storm focused south 
of the Mass Pike will impact southern New England late Saturday 
afternoon into Sunday morning. 


As this system tracks south of the area and then southeast of 
Nantucket...snow will overspread the area from the southwest. 
Looking at both NAM and GFS BUFKIT cross-sections...the best snow 
growth lays across northeastern Connecticut...northern Rhode 
Island...and southeastern Massachusetts. Could see some bands of 
heavier snow in this area and so this is where we are expecting the 
higher amounts of snow. If the track of the low does shift 
northward so would the higher snow amounts. With this forecast 
package we will issue a Winter Storm Watch for northeastern 
Connecticut...all of Rhode Island...southeastern Worcester 
County...southeastern Massachusetts /including the cape and 
islands/...and northeastern Massachusetts. The remainder of the 
area will see advisory level snow /3-6 inches/. 


The clipper will move out to sea Sunday morning bringing an end to 
the snow. Snow should come to an end from west to east Sunday 
morning...moving offshore by the afternoon. 


Made few...if any...changes to the forecast beyond Sunday night. 
Following is the previous discussion for those time periods. 


Sunday night-Monday...will be cold and blustery Sunday night... 
mainly near the coast. Wind will be short lived...though...as the 
progressive upper level pattern keeps systems moving across the lower 
48. High pressure ridge builds across New England on Monday. Overnight 
lows Sunday will be cold...dropping to the single digits over the 
inland higher terrain...ranging to around 20 or so along the 
immediate S coast. 


Beyond Monday...models still showing disagreement with progression 
of systems to the eastern Seaboard due to timing and track 
issues...as is usually the case further out in time. 


For now...have another weak system moving north of New England with its 
trailing cold front bringing scattered snow showers on Monday night 
and Tuesday. After the front pushes through...dry and colder weather 
for Wednesday. Will be very cold Wednesday night...with overnight 
lows ranging from 5 to 10 below over the higher inland terrain to 
10-15 degrees on the Outer Cape and islands. Another fast moving low 
approaches late Wednesday night...with scattered snow showers by 
Thursday. Not a whole lot of confidence with this portion of the 
forecast...however. 
&& 


Aviation /12z Friday through Tuesday/... 
expect VFR conditions today through 19z or 20z Saturday...after 
which ceilings and visibilities will lower as snow spreads into northern CT and 
southwest Rhode Island. Within an hour or two of snow beginning...ceilings and 
visibilities will likely rapidly lower from VFR to IFR. 


West winds gusting 20 to 25 knots in most areas today will cause low level 
mechanical turbulence. Winds should diminish this evening interior 
but still remain gusty for a time in the evening near the coast. 


Outlook /Saturday night through Tuesday/... 
Saturday night...IFR/LIFR conditions expected in snow. Heaviest snow 
will affect terminals south of the Mass Pike and east of I-95. 


Sunday...IFR conditions early in snow. Precipitation tapers off in the 
morning CT valley/SW New Hampshire...and moves offshore by late afternoon. As 
snow ends...conditions will improve to MVFR then VFR. 


Monday...VFR. 


Monday night into Tuesday...VFR conditions diminish to MVFR/IFR in 
possible snow showers. 


&& 


Marine... 
in the short term...will let the Gale Warning go with the release of 
this package but keep all marine zones into a small craft advsy 
today through tonight. It may be possible to drop bos Harbor and 
bays/sounds a little sooner but not that confident and would be 
splitting hairs at this point. Seas expected to continue to slowly 
subside through Sat morning. Used swannam through midday and then 
wave watch thereafter. 


Saturday night...seas increase gradually as clipper low moves 
through the waters southeast of Nantucket. Northeasterly winds 20 
to 25 knots expected with gusts to 30 knots possible. Visibilities reduced in 
snow. 


Sunday...seas continue to increase through the morning and then they 
gradually decrease as the clipper moves out to the open waters. 
Northeasterly winds 20 to 30 knots shift north then northwest and 
gradually decrease through the day. 


Monday...seas gradually decrease...falling below 5 feet. Winds shift 
from west to S and gradually increase overnight gusting to 25 knots. 


Tuesday...seas increase as another low pressure/frontal system 
affects the area. Winds will shift from S to west and increase as the 
system moves across the waters. There is a low probability of gale 
force wind gusts. 


&& 


Tides/coastal flooding... 
as noted by the prior shift...the late Sun morning astro high tide is 
a Spring tide with 11.9 feet predicted for bos at 1047 am. Mrpsse guidance 
depicts .7 feet surge on top of that near the time of high tide 
sun...now that the GFS has slowed down a little. We note that the 
mrpsse guidance...although dependent upon the GFS wind 
forcing...tends to have somewhat of a low bias more often than not. 
The eventual strength and track of the surface low...low level 
momentum Transfer to the sea surface and how much of an onshore 
component to the wind remains to the time of high tide will determine 
just how much of a surge we see. In addition how much impact from 
splash over will also be a function of the wave action. For 
now...looks like we may see seas of 5 to 10 feet just offshore. With 
all that stated...see a fairly high risk for minor coastal flooding 
along the east facing shorelines...especially those S of bos for that 
late Sun morning high tide. 


Thus...may need sometime this weekend to consider a coastal flood 
advisory depending upon path/ strength and timing of weekend storm. 


&& 


Equipment... 
WSR-88D is currently out of service. It will be looked at later this 
morning. 


&& 


Box watches/warnings/advisories... 
CT...Winter Storm Watch from Saturday afternoon through Sunday 
morning for ctz002>004. 
Massachusetts...Winter Storm Watch from Saturday afternoon through Sunday 
morning for maz005>007-012>024. 
New Hampshire...none. 
Rhode Island...Winter Storm Watch from Saturday afternoon through Sunday 
morning for riz001>008. 
Marine...Small Craft Advisory until 4 am EST Saturday for anz230>237- 
250-254-255. 


&& 


$$ 
Synopsis...rlg/Thompson 
near term...Thompson 
short term...Thompson 
long term...evt/rlg 
aviation...rlg/Thompson 
marine...rlg/Thompson 
tides/coastal flooding... 
equipment... 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)