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Area forecast discussion 
National Weather Service Taunton Massachusetts 
933 am EDT sun Mar 21 2010 


Synopsis... 
much cooler conditions today behind a cold front. Coastal low 
pressure will bring rain starting Monday...but the heaviest rainfall 
will be Monday night into Tuesday. Mainly dry weather with just 
above normal temperatures follows Wednesday into Thursday before 
somewhat colder weather arrives next Friday and Saturday. 


&& 


Near term /until 6 PM this evening/... 
a surface warm front will remain nearly stationary just to our south 
this afternoon. The bulk of the warm air advection-induced clouds and any light 
precipitation associated with the frontal system will likely remain located 
north of the Mass Pike for the afternoon...although a brief period 
or of broken skies could affect pretty much anyone south of there. 
This should allow for mostly sunny skies for much of southern New 
England for the balance of the day. However...northern and 
northwesternmost zones will have to deal with a band of cloudiness 
and isolated light rain showers /more likely just sprinkles/ today. Most 
locations will remain dry. 


Temperatures appear to be on track. Warmest readings will occur in 
the lower CT valley 


&& 


Short term /6 PM this evening through 6 PM Monday/... 
tonight...deeper moisture remains confined to the north so we only 
have slight chance probability of precipitation for north zones. Old frontal boundary may move 
back northward to S coast which may lead to some patchy low clouds/fog 
along the coast but confidence is low. NAM has it but GFS does 
not. 


Monday...isentropic lift increases and moisture deepens ahead of low 
pressure approaching from the SW. This will result in some light rain 
overspreading the region from west to east...but heavier rainfall 
will hold off until Monday night as low level jet still SW of new eng through 00z 
Tuesday. Will have likely probability of precipitation in the interior with chance in the 
coastal plain. Temperatures a mav/met blend with maxes in the 50s. 


&& 


Long term /Monday night through Saturday/... 
Monday night through Tuesday night... 
the models are in very good agreement in closed upper level low 
lifting northeast across the benchmark...with the surface 
reflection actually tracking in the vicinity of the I-95 corridor. 


In response...expect widespread rain to overspread southern New 
England Monday evening. A decent low level jet/forcing should 
result in a period of heavy rain Monday night into Tuesday morning. 
There is still plenty of uncertainty as to where the axis of 
heaviest rain will set up since the event is still 48 to 72 hours in 
the future. The srefs/gefs ensembles pin Rhode Island/eastern 
Massachusetts/southeast New Hampshire as the most likely locations to receive the heaviest 
rainfall. This is also where the models show the highest precipitable water 
values along with a decent low level jet. There also could be other 
localized maximum such as the east slopes of 
Berkshires/Monadnocks/Worcester Hills due to the added benefit of 
the upslope. The heaviest rain looks to occur by early Tuesday 
afternoon...but expect numerous rain showers to persist through 
Tuesday night as closed upper level remains to the southeast of our 
region. 


Total rainfall amounts from this system look to be on the order of 1 
to 2.50 inches. The best chance of the higher amounts appear to be 
across Rhode Island/eastern Massachusetts/southeast New Hampshire. This may result in 
renewed flooding for some of the same rivers/streams that had 
moderate or major flooding last week in Rhode Island/eastern 
Massachusetts/southeast New Hampshire. The potential flooding does not look to be as 
significant as what occurred last week. However...there is still a 
good chance that flood watches will need to be issued in the next 12 
to 24 hours for a portion of this region. 


Finally...there is a chance the precipitation ends as a bit of snow 
across the interior high terrain late Tuesday night/very early 
Wednesday morning. However...the bulk of the precipitation will be 
over so even if this happens not expecting much of an impact at this 
time. 


Wednesday and Thursday... 
any left over lingering showers should come to an end Wednesday 
morning as the upper level low lifts to the northeast of our 
region. Otherwise...westerly flow should result in mainly dry 
weather. Temperatures look to remain above normal although it will 
not be as warm as what has been experienced the last few days. Good 
mixing will also result in breezy to even windy conditions. 


Thursday night through Saturday... 
its still a long way off so this portion of the forecast is 
certainly subject to change. However...the models are in good 
agreement that a strong cold front will move through the region 
Thursday night/Friday morning. This front may be accompanied with a 
band of rain showers especially in the southern sections so included 
some low chance probability of precipitation. Otherwise...dry but unseasonably chilly air 
will work in behind this front. Since we are talking the last few 
days in March and we expect sunshine it should not be an extremely 
cold airmass. Nonetheless...expect below normal temperatures over 
this period and a big change from what has been experienced of late. 


&& 


Aviation /14z Sunday through Thursday/... 
this afternoon...moderate to high confidence VFR ceilings in areas of 
middle clouds. 


Tonight...low confidence VFR forecast. GFS is mainly VFR but NAM is 
showing areas IFR ceilings/visibilities in St/fog developing late. Sref ceiling/visibility 
probs also showing chance of St/fog developing along the S coast. We 
used GFS forecast for the tafs but uncertainty exists. 


Monday...conditions lowering to MVFR/IFR in developing showers and 
areas of St/fog...moderate confidence. 


Outlook...Monday night through Thursday... 


Monday night through Tuesday night...high confidence in MVFR-IFR 
conditions in rain/low clouds/fog patches. 


Wednesday... 
low to medium confidence that MVFR-IFR ceilings early improve to VFR 
during the afternoon. Northwest wind gusts of 25 to 35 knots 
expected in the afternoon. 


Thursday...high confidence in VFR conditions with northwesterly 25 
to 30 knot wind gusts. 


&& 


Marine... 
easterly winds 10-15kt this afternoon as warm front remains to the 
south. A few gusts between 20 and 25 knots possible near the cape early 
this afternoon. 


Tonight and Monday...winds become southerly over south coastal waters 
as front lifts northward to near the S coast...but winds remaining light east 
over northern waters. 


Outlook...Monday night through Thursday... 


Monday night and Tuesday...low pressure will track somewhere near 
the I-95 corridor. Winds and seas will begin to increase toward 
daybreak on Tuesday. A period of gale force northeast wind gusts 
may occur on Tuesday across our far northern and eastern 
waters...with Small Craft Advisory wind gusts and seas expected across the rest of 
our open waters. In addition...areas of fog may reduce visibilities 
at times especially Monday night/Tuesday morning. 


Wednesday...low pressure pulls away and winds shift to the 
northwest. Small Craft Advisory wind gusts are expected across the open waters with 
perhaps marginal near shore gale force wind gusts as mixing will be 
better over the land. 


Wednesday night and Thursday...a nice northwest flow of middle level 
air should generate strong Small Craft Advisory wind gusts. Brief marginal gale 
force northwest wind gusts are also possible for a time 


&& 


Hydrology... 
most of the remaining mainstem rivers in NE Massachusetts should drop below 
flood stage today. However...the Charles River at Dover and Concord 
River at Lowell will remain in flood into early next week. 


Please see flood warnings and statements for more specific 
information about the status of individual rivers. 


Total rainfall amounts from this system look to be on the order of 1 
to 2.50 inches. The best chance of the higher amounts appear to be 
across Rhode Island/eastern Massachusetts/southeast New Hampshire. This may result in 
renewed flooding for some of the same rivers/streams that had 
moderate or major flooding last week in Rhode Island/eastern 
Massachusetts/southeast New Hampshire. The potential flooding does not look to be as 
significant as what occurred last week. However...there is still a 
good chance that flood watches will need to be issued in the next 12 
to 24 hours for portions of the region. 


&& 


Tides/coastal flooding... 
splashover or minor coastal flooding are no longer expected across 
the region. Winds and seas do not appear large enough to support 
this potential at the time of high tide Tuesday morning. Onshore 
flow may result in some minor beach erosion in areas that have been 
hard hit across eastern Massachusetts in the past month. 


&& 


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


&& 


$$ 
Synopsis...kjc/Frank 
near term...ekster 
short term...kjc 
long term...Frank 
aviation...kjc/ekster/Frank 
marine...kjc/ekster/Frank 

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