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Area forecast discussion 
National Weather Service Taunton Massachusetts 
520 PM EDT Friday Jul 18 2008 


Synopsis... 
hot and humid weather continues into Sat. Potential for a few strong 
to severe thunderstorms this evening across northern CT...western and 
central Massachusetts and southern New Hampshire. Showers and thunderstorms should become more 
widespread Sunday...and especially next week as a trough of low 
pressure sets up across the northeast. Temperatures will begin to 
fall back to seasonable norms next week. 


&& 


Near term /until 10 PM this evening/... 
scattered showers and thunderstorms continued to spread from New 
York state into western New England late this afternoon. Somewhat 
more widespread activity is expected to develop early this evening 
across the interior as a short wave approaches from upstate New York. 
850-500 mb middle level lapse rates expected to steepen in response to 
this short wave between 6 and 6.5 celsius per km. 


Main challenge will be the timing and coverage of convection this 
evening. Currently favoring areas along and north of the Mass Pike 
with high chance to likely probability of precipitation...where best low level moisture 
convergence and strongest wind fields reside. Elsewhere a few 
scattered cells could track southeast of the Pike into far northern 
Connecticut...extreme northern Rhode Island and interior 
southeastern Massachusetts. A few of these storms will be severe. 
A Severe Thunderstorm Watch has been issued until 8pm for southern 
New Hampshire...and now an expansion will be issued further south 
into western and central Massachusetts and northern Connecticut this 
evening. Skywarn has been activated and will continue to monitor the 
potential for large hail and damaging winds this evening. 


A cold front approaching from northern New England should stall over 
extreme northern portions of the forecast area of just north of the 
forecast area late tonight. 


Otherwise expect convection to diminish after midnight with a muggy 
conditions expected. 


&& 


Short term /10 PM this evening through Saturday night/... 
Saturday...hot and humid conditions expected to persist as the cold 
front lifts back north. An uncomfortable day expected away from the 
immediate South Coast...although it appears heat indices will 
rise near 100 degrees for a brief time during the afternoon across 
urban sections including Boston and Hartford. Will not issue a heat 
advisory at this time but will mention this in the hazardous 
weather outlook. West flow and 850 millibar temperatures between +19 
and +20 celsius temperatures supports highs in the middle 90s away from 
the South Coast. 


Next concern will be the potential for thunderstorms and severe 
weather threat as the cold front may vacillates back to the south 
later in the day. There is considerable disagreement amongst the 
short range models regarding the placement of the front at this 
time...which will have a considerable impact on the potential for 
thunderstorms. Currently have decided to use the GFS as it keeps the 
front further north. This appears to make more sense given a nearly 
zonal flow at 500 millibars and little mechanism to drive the front 
further south. Overall have placed chance probability of precipitation across the northern 
half of the forecast area closest to the front. Given the amount of 
low level instability available any storms which do develop have the 
potential to become severe. Did not mention enhanced wording at this 
time but later shifts may want to consider this. 


Saturday night...evening convection possible over northern sections. 
Convection could linger for awhile as the front approaches. 
Otherwise another mild and humid night expected. 


&& 


Long term /Sunday through Friday/... 
still a lot of uncertainty during this portion of the forecast... 
especially with respect to the details. 


Middle level flow across New England remains zonal through early 
sun...then begins to become cyclonic later sun into early next week 
as long wave trough sets up across the Great Lakes and the northeast. 
This flow regime will support a stalled boundary somewhere around 
southern New England into early next week. 


Expecting unsettled weather with showers and thunderstorms /mainly diurnal/ 
becoming more widespread...but not a washout. In addition...the trend 
for temperatures will be to fall back to more seasonable values 
next week. 


Other feature Worth mentioning will be the quasi tropical wave 
currently off the southeast U.S. Coast. As broad southwest flow 
becomes established along the eastern Seaboard early next week in 
response to long wave trough over the Great Lakes and northeast...this 
system will begin moving northeast and possibly track across or 
near southern New England Monday or Tuesday. This may result in a widespread 
appreciable rainfall event. 


&& 


Aviation /21z Friday through Wednesday/... 
generally VFR this afternoon and evening except scattered MVFR/IFR in 
thunderstorms late today. The best chance looks to be in southern New 
Hampshire including mht from 22z to 01z. Extreme northern mass also 
possible. The thunderstorm potential includes a chance of wind gusts near 50 
knots. Mht taf will be updated if an actual thunderstorm is within 2-3 hours 
of the Airport...at 18z the potential action looked to be 5 hours away. 


With the convection in New Hampshire...we will need to keep an eye on thunderstorms 
potential this evening for baf-orh-bos. But the probability 
diminishes to the south with increasing distance from the supporting 
dynamics. 


Otherwise VFR overnight with areas of MVFR in haze/fog after 
midnight. 


VFR Sat except scattered MVFR ceiling and possibly local IFR visibility in 
mainly afternoon thunderstorms. 


Outlook...Saturday night through Wednesday... 


Predominantly VFR...however MVFR at times in scattered showers and 
thunderstorms. 


&& 


Marine... 
tonight...Small Craft Advisory for hazardous seas continues across 
the outer southeast waters tonight for persistent southeast swell up to 5 feet. 


Saturday and Saturday night...SW wind gusts up to 20 knots possible 
along the South Coast Saturday. Seas should remain near or just 
below Small Craft Advisory criteria as Bertha begins to track north of 
our latitude. 


Outlook...Sunday through Wednesday... 


Sunday...boundary begins to lift north as a warm front. Showers and 
thunderstorms possible. Winds become south and begin to increase. 


Monday into Wednesday...very uncertain given track of quasi tropical wave 
currently off the southeast coast. For the moment expecting generally 
south winds along with a chance of showers and thunderstorms. 


&& 


Climate... 
for informational purposes...here are some record high temperatures 
for today...July 18 


Orh...93 set in 1900 and 1982 
bos...98 set in 1982 
pvd...99 set in 1982 and 1999 
bdl...99 set in 1982. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Small Craft Advisory for hazardous seas until 6 am EDT 
Saturday for anz254-255. 


&& 


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

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