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


Synopsis... 
hot and humid weather today and Sat along with the potential for a 
few strong to severe thunderstorms this afternoon along and north of 
the Mass Pike. 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 6 PM this evening/... 
temperatures rising quickly late this morning so made an update 
to hourly temperatures. Otherwise forecast generally remains on track. 
Convective temperatures are quickly being approached across northern 
interior southern New England. A few pulse storms may develop by 2 PM 
across northern Massachusetts and southern New Hampshire. Main short 
wave across eastern Ontario/western Quebec provinces expected to 
approach by 00z. This will allow middle level lapse rates to steepen. 
Given the amount of low level instability...a more concentrated area 
of showers and thunderstorms is expected to cross mainly northern 
sections early this evening. May have to raise probability of precipitation further in a 
later update but will first examine the 12z model suite. 


The storms prediction center has brought southern New Hampshire into 
the slight risk area this afternoon and early evening. Will continue 
to keep the enhanced wording for this area. 


An air quality alert has been issued for all of Rhode Island and 
Hillsborough New Hampshire this afternoon and early evening. 


&& 


Short term /6 PM this evening through 6 PM Saturday/... 
this afternoon and evening... hot and increasingly humid conditions 
across much of southern New England. Even Marthas Vineyard hit 87 
degrees yesterday and it should be similar there this afternoon. 
Little change to previous forecast temperatures...with highs in the 
middle 90s in most interior locations as 850 mb temperatures reach +20c to +21c 
by 00z. Apparent temperatures are forecast to remain in the upper 90s 
with one hour of 100 degrees at Hartford. This is just below the 
thresholds for a heat advisory...which is 100 to 104 for 2 hours or 
more. So will not issue this for now. 


Have increased probabilities of thunderstorms to 30 to 40 percent in 
southern New Hampshire and into northern Massachusetts for late this afternoon and early 
this evening. Have also added some enhanced wording for gusty winds 
and small hail in Cheshire...Hillsborough...northern Worcester... 
northern Middlesex...and northwest Essex counties in that time period. 
Northern half of New England should see severe weather with damaging 
winds the main threat as band of 35-50 knots winds at 700 mb exists 
there. Less than 35 kts across southern New England. NAM has k index 
of 41 and total totals index of 52 in the Keene area at 00z. GFS on 
BUFKIT also shows a lot of upward vertical motion through a deep 
layer at 00z in the Manchester New Hampshire area. Models diverge in opinion 
though regarding how far south any convection will get. GFS shows 
most of Massachusetts...especially from Worcester to Boston...with k indices 
higher than 38... a very Good Thunder indicator this evening. NAM not 
as impressive. There is an axis of moisture convergence in that 
region in association with a weak pre-frontal trough. For now have 
included chance probability of precipitation as far south as the Mass Pike and slight chance 
as far as the CT/MA/RI border. 


Later tonight...hazy warm and muggy conditions. Cannot rule out a 
stray shower or thunderstorm with high k indices around...but 
probability too low for inclusion at the moment. 


Saturday...with a very warm start...a very hot day is again in store. 
Made no changes to interior maximum temperature forecast. Middle 90s 
again expected with perhaps as high as 97 in parts of the CT valley. 
Heat advisories may be needed as apparent temperatures reach up to 
101 in several locations for a few hours. Too early now to issue 
this. Do not expect excessive heat watch/warning criteria of 105 
degrees or higher for the apparent temperature. 


Have included 20-30 percent chances of thunderstorms in deference to 
large area of 38+ k indices over all of southern New England all day 
Sat. This could be a very active day. Although wind fields are not as 
strong as today...the heat and humidity will make the atmosphere 
quite unstable and some scattered strong thunderstorms may form. Stay 
tuned for later forecasts on this potential. 


&& 


Long term /Saturday night through Thursday/... 
middle level flow across New England remains zonal through early 
sun...then begins to become cyclonic later sun and especially early 
next week as long wave trough sets up across the Great Lakes and the 
northeast. This flow regime will support a stalled boundary over the 
region Sat night...then likely lifting north Sunday as a warm front 
in response to the middle level flow becoming southwest. Therefore the 
chance of showers and thunderstorms exist Sunday. In addition...very warm 
and humid conditions will continue Sunday. 


As cyclonic flow becomes entrenched across the region next 
week...expect unsettled weather with showers and thunderstorms /mainly 
diurnal/ becoming more widespread. Any rainfall will be beneficial 
given our recent dry weather. In addition...the trend for 
temperatures will be to fall back to more seasonable values next week. 


Other feature Worth mentioning will be the tropical wave currently 
off the southeast 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 tropical feature 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 /18z 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 Tuesday... 


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


&& 


Marine... 
a Small Craft Advisory for hazardous seas has been pushed up to the 
current time for southeast swell due to Bertha. 


Outlook...Saturday night through Tuesday... 


Sat night...possible thunderstorms with weak cold front entering the region. 
Not much wind or wave to speak of. 


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


Monday and Tuesday...very uncertain given track of tropical wave currently 
off the southeast coast. For the moment expecting south winds to 
increase to 20-25 knots Monday and Tuesday along with the 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...nocera 
near term...Strauss 
short term...gaf 
long term...nocera 
aviation...wtb/nocera 
marine...nocera/Strauss/gaf 
climate... 

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