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Area forecast discussion 
National Weather Service Taunton Massachusetts 
608 PM EDT Wednesday Oct 15 2008 


Synopsis... 
weak high pressure will move over New England this evening. A cold 
front will then move across New England on Thursday bringing showers. 
High pressure from the northern plains will bring fair and cooler 
weather for the weekend. The next cold front will then move through 
late Monday or early Tuesday. 


&& 


Near term /until 2 am Thursday morning/... 
after reviewing the latest 18z suite of model data have made some 
changes to the current cloud forecast. An area of stratus that 
affected the cape/islands today looks to expand further northwest 
onto portions of the coastal plain and possibly even further west overnight. 
The NAM boundary layer relative humidities show this nicely and with 
dewpoints in the 50s this scenario seems to make sense. 
Therefore...will Show Low stratus gradually spreading into portions 
of the region. In addition...the sref probabilities are showing 
some decent numbers for the potential of patchy fog developing as 
well. 


Previous discussion below: 


The next area of clouds is moving into western New York and 
extrapolates to western New England around 2-3 am...then across the 
remainder of our area by morning. Showers associated with the clouds 
are farther west in Michigan and Indiana. These will take until 
morning to arrive...possibly reaching our western zones by 6 am. 


Dewpoints in the 40s to lower 50s provide a lower end for min temperatures 
tonight...most of which should be achieved before the clouds arrive. 
After the clouds move in the temperatures should level out and even 
rise a little. We will go a little above guidance with mins in the 
middle 40s to middle 50s. 


&& 


Short term /2 am Thursday morning through Thursday night/... 
cold front moves through New England Tuesday afternoon and evening. 
The main low pressure center pulling the low has elected to pass well 
north of the Canadian border. But the front will be supported by a 
110 knot jet moving out of the Ohio Valley and across southern New 
England. Precipitable water values are forecast between 1.5 and 1.75 
inches in a plume of moisture from the western Gulf of Mexico. With 
this combination of moisture and lift in the next 24 hours...we will 
go with categorical probability of precipitation under the left exit region of the jet and 
likely probability of precipitation farther south. Clouds will limit maximum temperatures Thursday...but 
with 12c aloft and a southwest wind we should still reach the 
60s...with a few warmer spots in the upper 60s. 


The front moves off Thursday night. Expect clearing skies after frontal passage 
and cooling temperatures. Temperatures last night upstream in Minnesota and 
the eastern Dakotas were in the upper 30s to middle 40s...which seems a 
good range to use for Thursday night. 


Winds over the cape and islands and other southeast sections show 
some mixing potential in the cold advection behind the front. Winds 
at 950 mb are forecast 20 to 25 knots. We will go close to 
this...within the range of 15 to 25 knots. 


&& 


Long term /Friday through Wednesday/... 
Friday... 
a dry and cool push of air will follow behind a cold front for 
Friday. Skies should be partly to mostly sunny across the region. 
However...with 850 mb temperatures between 0c and -2c highs should 
be help in the upper 50s to around 60. 


Friday night... 
high pressure nosing in from the Great Lakes will provide for a 
chilly night. Skies should be partly cloudy as the models do show 
an increase in high clouds out ahead of the axis of the trough 
axis. Nonetheless...airmass is cold enough to support lows around 
30 across portions or southwest New Hampshire/northwest Massachusetts...to the lower 40s 
in the urban heat island of Boston/Outer Cape/Nantucket. Much of 
the rest of the region will see lows well down into the 30s. 


Saturday and Saturday night... 
a reinforcing shot of cool air will be ushered into the region. 850 
mb temperatures drop to between -3c and -4c. Skies should partly 
sunny across much of the region...but we do expect some scattered 
strato-cumulus clouds. In addition...skies may remain mostly cloudy 
across portions of the cape and Nantucket with some ocean effect 
cloudiness as lapse rates steepen. Would not even be surprised if we 
see some ocean effect sprinkles/very light rain showers Saturday 
night as the latest European model (ecmwf) does have some very light quantitative precipitation forecast. Not 
sure...but did add a 20 pop for this region Saturday night when 
lapse rates are the steepest for a passing sprinkle/light rain 
shower. Certainly not a big deal though. Expect high temperatures 
to only recover into the low to middle 50s for Saturday. These 
temperatures are about 5 to 10 degrees below normal for this time of 
year. 


Quite a chilly night is in store for southern New England Saturday 
night. Large high pressure building into the region and mostly 
clear skies will provide for an ideal night of radiational cooling. 
The exception will be for portions of the cape/Nantucket where ocean 
effect clouds will affect the region. Lows should range from the 
middle 20s across southwest New Hampshire/northwest Massachusetts...to mainly well down into 
the 30s elsewhere. Even downtown Boston should see the Mercury fall 
to around 40. 


Sunday and Monday... 
high pressure will begin to move off the coast on Sunday allowing 
for warming middle level temperatures. However...mixing will not be 
great and with a cold start the surface will take bit more time to 
warm. Skies should be mostly sunny on Sunday...but with highs in 
the middle to upper 50s. On Monday...we should see temperatures 
rebound into the lower to middle 60s on the coastal plain ahead of an 
approaching cold front. 


Monday night through Wednesday... 
the European model (ecmwf)/GFS show a strong cold front moving through the region 
late Monday or Tuesday. They differ a bit on the timing with the 
GFS about 6 to 12 hours faster. Maintained a 30 pop as the front 
could be accompanied by a brief band of rain showers late Monday or early 
Tuesday. Otherwise...a chilly airmass will be ushered back into the 
region on Tuesday and Wednesday with highs only in the 50s. 


&& 


Aviation /22z Wednesday through Monday/... 
tonight...based on 18z suite of model data will be making some 
modifications to the aviation forecast. Low stratus that affected 
the cape/islands looks to expand further northwest tonight onto 
portions of the coastal plain and possibly a bit further. 
Therefore...will indicate MVFR ceilings for much of the coastal 
sites overnight. In addition...localized IFR conditions are 
possible particularly on the cape/islands. 


Developing MVFR in clouds and showers Thursday. Brief IFR possible in 
heavier showers. Conditions linger into the evening...ending from 
west to east. 


Clearing skies later Thursday night with VFR most spots. Possible IFR 
in patchy fog late Thursday night especially in the CT valley. 


Outlook...Friday through Monday 


VFR the vast majority of the time. The only exceptions are some 
isolated early morning fog patches in the typically prone 
locations. There also may be a period of marginal MVFR/VFR ocean 
effect clouds on the Outer-Cape/Nantucket Friday night into early 
Sunday. 


&& 


Marine... 
winds and seas remain below small craft levels tonight and Thursday. 
A cold front moves across the waters Thursday evening or early night. 
Cold advection behind the front will promote northwest gusts to 20 or 
25 knots across the waters...a Small Craft Advisory may be needed at 
that time. 


Outlook...Friday through Monday 


Friday and Saturday... 
northerly winds with gusts of 20 to 25 knots are expected for much 
of the time as cool advection will provide for good mixing. The 
strongest winds may occur Friday morning and then again late 
Saturday and Saturday night with another surge of chilly air. 


Sunday and Monday... 
winds should diminish on Sunday as high pressure builds over the region. 
However...gradient will increase on Monday ahead of an approaching 
cold front. Therefore...we may see Small Craft Advisory seas along with 25 to 30 
knot southwest wind gusts develop. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...none. 


&& 


$$ 
Synopsis...wtb/Frank 
near term...wtb/Frank 
short term...wtb 
long term...Frank 
aviation...wtb/Frank 
marine...wtb/Frank 

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