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Area forecast discussion 
National Weather Service Taunton Massachusetts 
500 am EDT Thursday Jul 24 2008 


Synopsis... 
a slow moving cold front will bring heavy rainfall and possible 
flooding to portions of southern New England through this evening. 
A second cold front will approach late this weekend with another 
round of showers and thunderstorms possible. Unsettled weather will 
remain across the region through early next week. 


&& 


Near term /until 6 PM this evening/... 
a warm front continues to lift north across the forecast area this 
morning...in response to increasingly southerly boundary layer flow. 


Convection has weakened across the forecast area early this morning. 
However the next batch of precipitation was about ready to arrive 
from the NYC metropolitan area. 


A cold front located across western New York will gradually approach 
from the west. A series of short wave disturbances will also 
approach from the west today. The forecast area is expected to 
reside within the divergent right rear quadrant of a 110kt of 250 mb 
jet streak. 850 mb Theta-E ridge and precipitable water axes remain 
located across western New England this morning. Good low level 
moisture convergence as well with a southerly 45 knots low level jet 
approaching Long Island New York this morning. Overall will continue 
categorical probability of precipitation. Decided to use HPC guidance as operational models 
such as the GFS appear underdone. Flood Watch continues for western 
New England. Have decided to expand the Flood Watch further east 
given recent heavy rains in Rhode Island and eastern Massachusetts. 
Rainfall totals are expected to total 3 to 5 inches across western 
New England with localized amounts up to 8 inches. In eastern New 
England we expect the heaviest rainfall to occur from midday through 
the early evening hours...with totals of 1 to 3 inches expected and 
localized amounts up to 5 inches possible. Will continue to monitor 
this potential today. 


Next issue will be the potential for severe weather. Wind fields are 
fairly impressive with a decent low level jet and upper level jet 
centered over the region. Decent most unstable cape values aloft. 
Middle level lapse rates and helicity values are not quite as 
impressive as yesterday. Overall main threats will be flash 
flooding...damaging winds and hail. Have added enhanced wording 
across much of the forecast area. Any breaks of sun will enhance the 
severe potential today. Skywarn activation will likely be needed 
today. 


Otherwise expect a warm and very humid day with showers and 
thunderstorms producing torrential downpours. 


&& 


Short term /6 PM this evening through 6 PM Friday/... 
Thursday night...showers and thunderstorms this evening will come to 
an end as the cold front crosses southern New England. Have 
continued likely to categorical probability of precipitation across much of the forecast 
area. Expect a very humid night...but with some deceasing humidity 
late across the far interior. 


Friday...a few lingering morning showers will be possible on the 
cape and islands. Otherwise expect a seasonably warm day with 
increasing sunshine and lowering humidity values. 


&& 


Long term /Friday night through Wednesday/... 
models showing less continuity this afternoon...lending to less 
confidence to this portion of the forecast...especially from Monday 
Onward. Leaned toward the GFS and European model (ecmwf) ensembles for this portion 
of the forecast. 


One thing that appears to show some continuity is the long wave 
upper level trough that is expected to remain along the eastern U.S. 
Through at least Tuesday. 


Thursday night...front moves slowly across the region with likely to 
categorical shwrs/tstms. Models having difficulty with the timing of 
this system...though appears that the front will work into eastern 
Massachusetts by 12z. With high precipitable water values continuing...will also see more heavy 
rainfall as well. 


Friday...cold front swings offshore...then stalls S of the region in 
the general SW upper flow as high pressure remains stalled over the 
western Atlantic. Some leftover showers will end over eastern Massachusetts in the 
morning. Dewpoints will drop a bit...but remain in the Lower-Middle 60s as 
highs head to the lower to middle 80s. Will also remain dry Friday night 


Saturday...next front begins to approach around the cutoff upper low 
over Quebec. Timing is suspect as models showing some spread at this 
point...but have included chance probability of precipitation from west-east during the day. 
Dewpoints head back up with the continued SW flow. Current timing 
suggests best shot of showers/thunderstorms will occur during the nighttime 
hours...but not a whole lot of confidence. 


Sunday through Tuesday...at this point...appears that the front 
slows to a crawl as it crosses the region over this weekend...then 
will push just off the coast on Monday. Have carried chance probability of precipitation 
through Monday...though still have not a lot of confidence with the 
timing of this system. 


Wednesday...appears that it will be a dry day with high pressure trying 
to push east out of the Great Lakes. However...low confidence due to 
the very amplified upper pattern in place. 


&& 


Aviation /09z Thursday through Monday/... 
today...areas IFR ceilings will temporarily improve to MVFR. 
Scattered convection becoming widespread rain showers/thunderstorms and rain this morning and 
afternoon. Heavy rainfall expected. Isolated severe thunderstorms 
possible. 


Tonight...areas IFR ceilings will gradually improve to MVFR after 
midnight western terminals. 


Friday...conditions gradually improving to VFR...lingering IFR 
conditions possible cape and islands. 


Outlook...Thursday night through Monday... 


Sat...VFR early. Conditions lowering to MVFR-IFR in scattered rain showers/thunderstorms and rain 
from west-east during the day. 


Sun and Monday...IFR am/MVFR PM scattered rain showers/thunderstorms and rain and fog patches S coast 
each day. 


&& 


Marine... 
today...Small Craft Advisory has been expanded to include all waters. 
Wind gusts to 25 to 30 knots will be possible. Wna seas have been 
undercut 20 percent due to low level inversion. 


Tonight and Friday...Small Craft Advisory for hazardous seas and 
leftover swell. 


Outlook...Thursday night through Monday... 


Saturday and Sunday...Small Craft Advisory for hazardous seas will continue with 
building S-SW swell expected ahead of the next approaching cold 
front...mainly on the southern waters. 


Monday...winds shift to west and diminish. Leftover seas will remain 
close to small craft criteria on the southern outer waters. 


&& 


Box watches/warnings/advisories... 
CT...Flood Watch through late tonight for ctz002>004. 
Massachusetts...Flood Watch through late tonight for maz002>021-026. 
High surf advisory from 8 am this morning to 8 am EDT Friday 
for maz020-023-024. 
New Hampshire...Flood Watch through late tonight for nhz011-012-015. 
Rhode Island...Flood Watch through late tonight for riz001>007. 
High surf advisory from 8 am this morning to 8 am EDT Friday 
for riz006>008. 
Marine...Small Craft Advisory until 6 PM EDT this afternoon for 
anz232>237-254-255. 
Small Craft Advisory from 10 am this morning to 6 PM EDT this 
afternoon for anz230. 
Small Craft Advisory from 8 am this morning to 6 PM EDT this 
afternoon for anz231-250. 


&& 


$$ 
Synopsis...kjc/evt 
near term...Strauss 
short term...Strauss 
long term...evt 
aviation...Strauss/evt 
marine...Strauss/evt 

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