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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 79 °
• Low: 59 °
• T-Storms

• Thursday
• 
• High: 79 °
• Low: 59 °
• Chance of T-Storms

• Friday
• 
• High: 81 °
• Low: 63 °
• T-Storms

• Saturday
• 
• High: 86 °
• Low: 59 °
• Partly Cloudy

• Sunday
• 
• High: 73 °
• Low: 57 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service Taunton Massachusetts 
1012 PM EDT Tuesday may 22 2012 


Synopsis... 
low pressure southeast of Nantucket will move to Nova Scotia by 
Wednesday morning. A weak cold front will move into New England on 
Wednesday. Southeasterly flow over southern New England late 
this week may result in showers and thunderstorms. Chance for 
storms increases Saturday as a cold front approaches the area. 


&& 


Near term /until 6 am Wednesday morning/... 
10 PM update...see a few areas of drizzle by precipitation reports... 
mainly across eastern Massachusetts. Could see areas of drizzle 
continue as low pressure slowly moves away from the area. Areas of 
fog continue to impact much of eastern Massachusetts...as well as 
parts of Rhode Island. For the most part...visibilities remain 
above 1 mile. So while there is the possibility for locally dense 
fog...particularly along the South Coast...will not issue a dense 
fog advisory at this time. Made only minor updates to the 
forecast. 


Previous forecast discussion... 
low pressure offshore moves northeast to Nova Scotia tonight 
while a weak upper level ridge builds over New England. So we 
expect remaining showers to diminish/move off early tonight. Probability of precipitation 
will show a diminishing trend from press time through midnight. 


Not much drying expected in the airmass with weak west flow in 
place and a cold front over New York. So dewpoints will remain 
55-60...and therefore min temperatures should be in the same range. With 
so much of the region near saturation overnight...we expect areas 
of fog with locally dense values especially in Rhode Island and eastern 
mass. 


&& 


Short term /6 am Wednesday morning through Wednesday night/... 
Wednesday... 
upper low moves up the coast and resumes the south flow into 
southern New England. Meanwhile a weak cold front moves across 
western and central sections during the day. Models show some 
instability focused over that region. Cape values of 500-1000 
j/kg...lifted index around -2...totals at 47-48. Not sure how much 
solar heating will be able to work on the airmass...but the 
presence of the front will provide lift through low level 
convergence. We will go with chance probability of precipitation for showers/tstms. Winds 
of 5 knots at 850 mb and 10 knots at 500 mb do not argue for 
severe weather. Precipitable water values near 1.5 inches suggests 
potential for locally heavy downpours. 


Temperatures/dewpoints are a blend of bias corrected MOS. 


Wednesday night... 
what is left of the cold front will stall over southern New 
England and dissipate. So no change in airmass expected. Wednesday 
night should be similar to tonight with light wind and dewpoints 
55 to 60. Min temperatures should be close to dewpoint and the resulting 
saturation should bring areas of fog...with some locally dense 
fog. Temperatures are a blend of MOS. 


&& 


Long term /Thursday through Tuesday/... 
highlights... 
* unsettled weather continues through the end of the week 
* temperatures on a gradual warming trend through early next week 


Confidence level... 
moderate confidence on overall package as model timing is different 
beginning at day 5 and Onward. High confidence that precipitation will 
occur from Thursday through Friday...exact timing and location is 
still uncertain but believe that it will be more showery rather than 
a widespread event. Friday night Onward is uncertain as timing of a 
dynamic cold front is questionable as well as other certain surface 
features through the work week next week. Moderate confidence on 
thunder potential for the rest of this week. 


Details... 


Thursday through Friday... 
strong upper level ridge will move over New England during this time 
frame. This will temperatures increase. Only caveat is a disturbance 
caught in the flow. This upper level low currently over the 
southeast will cut off then move toward the northeast as the ridge 
builds. This system will keep showery weather across the region 
during this timeframe. With a good amount of moisture in the 
area...and some breaks in the clouds believe diurnal showers will 
develop. There is a slight chance that a rumble of thunder could 
occur as instability increases and lapse rate steepen. However 
severe weather seems likely as there is very little shear in the 
region. The better day for convection appears to be on Friday. 


With the good amount of moisture combined with southerly 
flow...develop of fog is likely especially across the South Coast during 
the evening on both Thursday and Friday. Temperatures will be on the rise 
thanks to the building ridge...expect upper 70s into the 80s with 
coastal region being a tad cooler as sea breeze development is 
possible due to light winds. 


Saturday into Sunday... 
models diverge during this timeframe...which causes confidence level 
to drop. Upper level disturbance will move through the trough across 
the northern plains on Friday and approach New England by Sat/sun 
dragging a cold front through the weekend. The GFS is still to fast 
on the timing of this cold front compared to the European model (ecmwf). Decided to 
trend towards previous forecaster and HPC on timing of the front as well 
as precipitation chances. If the front does slow down and move through by 
the later afternoon to early evening hours...thunderstorm 
development is not out of the question. However because of 
uncertainty decided to keep it out of the forecast for now. As the 
front moves through expect conditions to dry out for the overnight 
hours. Appears that another frontal boundary will move through 
sometime on Sunday into Monday. This again will bring a chance for 
thunderstorms across the area as warm moisture air returns to 
southern New England. 


Temperatures will be on the increase over this Holiday weekend. 
Noticed HPC is pushing above 90 for portions of the area on the 
weekend. Deviated to blend previous forecast and MOS for high temperatures to 
show upward trend. With the amount of boundaries around the area as 
well as cloud cover...think temperatures might be just a few degrees shy of 
HPC guidance. 


The work week... 
good model agreement in the upper levels as upper level ridge begins 
to break down as high pressure slides southward. Strong upper level 
disturbance moves southward from Canada. Still some model 
discrepancies on exact location this disturbance will move over as 
the GFS is more progressive than the European model (ecmwf). Until the models have a 
better handle continued with previous forecast keeping showery weather across 
the area through the beginning of the work week. 


&& 


Aviation /02z Wednesday through Sunday/... 
forecaster confidence levels... 
low...less than 30 percent 
moderate...30 percent to 60 percent 
high...greater than 60 percent 


Overview... 
moderate confidence in tafs. Persistent north/NE flow will keep low 
ceilings locked in through Wednesday morning and areas of fog expected to 
become widespread again this evening. Ceilings will be slow to improve 
Wednesday but am confident on improvement to VFR around midday...except 
on Outer Cape cod and kack where low ceilings will probably remain all 
day. Weak gradient will bring return of low clouds/fog Wednesday night... 
especially near coast. 


Kbos taf...moderate confidence. Timing of lowest conditions 
tonight may be an hour or two off. Expect conditions to improve 
slightly between 6-9z. Higher confidence on timing of improvement Wednesday. 


Kbdl taf...moderate confidence. Timing of low ceilings may be a few 
hours too fast tonight. Higher confidence on timing of improvement 
Wednesday. 


Outlook...Thursday though Sunday... 


Thursday through Friday...low to moderate confidence. 
Daytime generally VFR with periods of MVFR in showers and possible 
thunderstorms and rain. Nighttime MVFR with periods of IFR in fog. 


Saturday into Sunday...low to moderate confidence. 
Fog will dissipate by the morning hours. Expect MVFR in showers and 
thunder as cold front moves through. Sunday expect mainly VFR with 
low probability of MVFR as showers and thunder moves through via 
warm front. 


&& 


Marine... 
tonight through Wednesday night...moderate confidence 
light winds through the period. South swell will slowly diminish 
through the period with 6 foot values on the southern exposed 
waters tonight and 4 foot values Wednesday. Wnawave and Swan NAM 
wave values were quite similar this afternoon so we used a blend 
of the two. Small Craft Advisory for hazardous seas has been 
expanded to include the eastern outer waters between Merrimack 
River and Provincetown. This Small Craft Advisory continues through Wednesday on 
the outer waters and on Rhode Island Sound/bid sound. 


Outlook...Thursday through Sunday... 


Thursday into Friday....moderate to high confidence. 
Seas remain below 5 feet through the period with high pressure over 
Maine and the Maritimes. Similarly winds will remain generally out 
of the south and below 25 kts. High confidence in fog reducing 
visibilities at times...mostly during the overnight periods. 
Showers and thunderstorms are a low probability each afternoon and 
evening 


Saturday into Sunday...low to moderate confidence. 
Winds and seas will continue to be below Small Craft Advisory for the period. However 
believe that model guidance has underdone both as frontal system 
will pass through on Saturday bring precipitation to the waters. Sunday 
another wind shift will occur as a warm front will move through 
bring another chance of showers. Low probability for thunder during 
the afternoon into evening. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Small Craft Advisory for hazardous seas until 3 PM EDT 
Wednesday for anz235-237. 
Small Craft Advisory for hazardous seas until 8 PM EDT 
Wednesday for anz250-254>256. 


&& 


$$ 
Synopsis...wtb/dunten 
near term...wtb/rlg/dunten 
short term...wtb 
long term...dunten 
aviation...dunten/jwd 
marine...wtb/dunten