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Area forecast discussion 
National Weather Service Taunton Massachusetts 
557 PM EDT Thursday Aug 28 2008 


Synopsis... 
high pressure dominates our weather through the end of this week. A 
cold front will cross southern New England Saturday night. This 
should be followed by high pressure from Canada providing dry and 
warming weather through midweek. 


&& 


Near term /until 6 am Friday morning/... 
the forecast area remains underneath a weak upper level ridge and 
surface high pressure. An upper level low near 40n and 60w is 
expected to drift north tonight. The remnants of Fay will remain 
southwest of the region. 


Changes: yesterdays GFS signals appear to have been spot on! Broken SC 
now flirting with Cape Cod. Reviewing more data but likely adding 35 
percent more cloud to Outer Cape cod and ack tonight...will be done by 615 
PM. 


Otherwise variable cirrus and ac interior. 


So...overall a partly cloudy forecast tonight...becoming mostly 
cloudy for a time especially across the Outer Cape and ack. Fog 
patches will be possible across the interior valleys. Used a blend of 
mav/met MOS guidance to derive overnight lows. 


&& 


Short term /6 am Friday morning through Friday night/... 
Friday...925mb east to northeast flow will weaken and increasing 
sunshine will allowing for any morning low clouds to dissipate. 
Otherwise expect a partly sunny and mild day with remaining diurnal 
cumulus clouds. A weak upper level ridge remains. The 12z GFS tries 
to bring measurable precipitation during the afternoon...from the 
remnants of Fay...but it also appears to be suffering from 
convective feedback issues including a spurious short wave. 
Considerable high clouds will occur due to convection to the 
southwest but dry conditions are expected at this time. The srefs 
and the majority of GFS ensembles signal dry conditions as well. 


Friday night...the weak upper level ridge begins to dissipate 
allowing the westerlies to advance an approaching cold front from 
the Great Lakes. The best moisture convergence and mechanisms for 
lift remain west of the forecast area across central and western New 
York state in the vicinity of the cold front. Currently have maintained 
a slight chance pop over extreme western New England approaching 
daybreak Saturday. 


&& 


Long term /Saturday through Thursday/... 
the 12z GFS and 00z European model (ecmwf) look similar in handling the pattern over 
the USA this period. Main features are a weak cold front moving 
through New England Saturday and moving offshore early Saturday 
night...and building upper high pressure over the eastern USA 
thereafter. 


The cold frontal passage on Saturday looks like a marginal event. Jet level 
support trails the front late Saturday night. Middle level winds are 
forecast around 30 knots and low level winds at 15 knots. The best 
dynamical support based on the 12z runs would be in northern and 
western sections...but 4 more model runs between now and then the 
timing could shift enough to move this favored area. Precipitable 
water values are expected to climb to 1.7 inches which might support 
a few heavy showers. For now we will maintain low end chance probability of precipitation 
for Saturday afternoon and early night. 


Closed upper low over the Maritimes will keep a cool northwest flow 
over New England Sunday with -12c aloft over Maine and New Hampshire...and 
probably into eastern mass as well. This would support some diurnal 
cumulus development midday...then diminishing as the low moves east. 


Otherwise the upper pattern digs a trough over the western USA and 
builds a ridge over the east. This means generally dry weather for US 
Sunday through at least Wednesday. 850 mb temperatures start around 11c 
Sunday and increase to 18c Wednesday...suggesting highs around 80f 
Sunday warming through the 80s through midweek. If 850 temperatures actually 
linger near 18c Wednesday...then highs near 90f would be possible. 
For now we will go above guidance but keep it in the 80s. 


On Thursday a cold front approaches through the eastern Great 
Lakes. Low pressure lingers off the Maritimes. The GFS keeps US 
between systems...warm and dry...while the 00z European model (ecmwf) drifts the 
ocean storm west and brings a chance of showers to eastern 
sections. Inclination is to keep the weather dry Thursday. Could be a 
chance of showers Thursday night especially in northern sections...with 
the approaching cold front. 


&& 


Aviation /22z Thursday through Tuesday/... 
tonight...generally VFR through 06z...excepting ack where intermittent 
ceilings near 1500 feet through the night. 


MVFR ceilings 2-3 thousand feet developing hya by 06z and mht-bos for a time 
10z-15z Friday. Local MVFR visibilities in ground fog patches across sheltered 
locations near the interior river valleys and bogs for a time late 
tonight. 


Friday...generally VFR. MVFR ceilings 020-030 hundred feet mainly kbos hya ack 
until 15z. Local seabreezes developing near shore by 15z. 


Friday night...generally VFR. Local MVFR visibilities in ground fog patches 
across sheltered locations. Isolated rain showers after 09z western terminals. 


Outlook...Saturday through Tuesday... 
generally VFR through the period. Patchy MVFR/IFR in showers/thunderstorms 
Saturday afternoon and night with cold front passage. Northwest 
surface flow Sunday through Tuesday. 


&& 


Marine... 
tonight through Friday night...some east-northeast swell around 2 feet expected 
from the offshore low tonight through Friday...with significant wave 
heights of 2 to 4 feet. The east swell could increase to 2 to 4 feet Friday 
night into early Saturday. Winds and seas expected to remain below 
Small Craft Advisory criteria at this time. 


Outlook...Saturday through Tuesday... 
light winds and seas through most of the period. A cold front moving 
across the waters Saturday night may bring scattered showers and 
thunderstorms. Low pressure lingering south of Nova Scotia may send 
4 to 5 foot swells to the waters east of Cape Cod and Nantucket 
Monday. 


&& 


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


&& 


$$ 
Synopsis...wtb 
near term...drag/Strauss 557 
short term...Strauss 
long term...wtb 
aviation...wtb/Strauss 557 
marine...wtb/Strauss 

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