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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 64 °
• Low: 55 °
• T-Storms

• Tuesday
• 
• High: 63 °
• Low: 55 °
• Chance of Rain

• Wednesday
• 
• High: 68 °
• Low: 57 °
• Chance of Rain

• Thursday
• 
• High: 66 °
• Low: 52 °
• Fog

• Friday
• 
• High: 63 °
• Low: 55 °
• Fog

Area forecast discussion 
National Weather Service Taunton Massachusetts 
204 PM EDT Monday may 21 2012 


Synopsis... 
low pressure will track up the coast...bringing showers through 
tonight. Scattered mainly afternoon showers or thunderstorms are 
expected both Tuesday and Wednesday afternoon. A cold front may 
produce showers and thunderstorms across much of the area on 
Saturday. 


&& 


Near term /until 6 PM this evening/... 
10 am update...low clouds/fog/drizzle have moved up the coastal 
plain and by late morning extended from Boston to westerly. Lowest 
conditions are along the immediate coast with visibilities 1 mile or 
less. Some sun lingered in southern New Hampshire late morning but the 
movement of clouds should cover the sky there for the afternoon. 


Expect the fog to linger in the coastal plain through the 
afternoon. Visibilities should improve this afternoon as temperatures climb a 
few more degrees. Low confidence on this improvement happening 
along the immediate coast...where onshore winds may keep temperatures 
cooler and dewpoints higher. 


Most of the observed showers have been moving northwest through 
NYC and southern New York...also northwest into southern New Jersey. Okx radar 
shows signs of showers at extreme range voer the offshore waters 
south of New England. Extrapolation of these showers would bring 
them to the south New England coast around 18z. This is in line 
with our forecast of likely probability of precipitation to the coast. We have slowed probability of precipitation 
a little and tightened the gradient from none pop to likely. But 
overall forecast remains intact. 


Previous discussion... 
most of the long range models appeared in fairly good agreement 
for this period. Only outlier noted was the 00z op NAM run...which 
appeared to develop a deeper low and bring it up the coast quicker 
than the ggem/GFS or ecwmf. Expect first low to push into the middle 
Atlantic coast today...then another low will work up the coast later 
today which will bring first slug of moisture into the region. 
Along with increasing low level moisture working up with this low 
is also increasing pw/S...on the order of around 1.5 inches by 
this evening. Will also see fairly good instability working 
northward ahead of deformation zone/warm front. Noting tq values 
for elevated instability at around 20...with lifted indices as low 
as -1 moving across from S-north through the day. Have kept mention of 
isolated thunder in the grids and zones. 


As showers move into the region...some could bring brief heavy 
downpours mainly this afternoon but not expecting widespread heavy 
rainfall at this point. Will also see patchy fog especially along 
the coast with light onshore winds. Even with light east-southeast 
winds...expect highs only in the 60s...maybe pushing to around 70 
well inland. 


&& 


Short term /6 PM this evening through 6 PM Tuesday/... 
tonight...looks like band of heavier precipitation will move across as warm 
front moves across. If any instability manages to make it in... 
should occur prior to or around midnight. Precipitable water/S increase just a bit 
more as low level moisture continues to feed up to coast...upwards 
to 1.6 to 1.7 inches...so could see some localized downpours again 
mainly along the coast. Band of precipitation shifts north-northwest with a break in 
the best action after midnight...but could still see scattered 
showers with short wave moving across. Overnight lows will only fall 
back to the middle 50s to around 60. 


Tuesday...models continue to signal another low to pass east of 
Nantucket and Cape Cod during the day. Looks like most of the precipitation 
will remain offshore...though some may clip the cape and islands. 
Short wave will also push NE...so could see some improving 
conditions though clouds will linger. May see some brief gusty east-NE 
winds across the cape as the low passes during the morning until 
around midday. Have kept chance probability of precipitation going mainly in the 
morning...then may break up briefly during the afternoon. Highs will 
be in Lower-Middle 70s except in the 60s along the coast with continued 
onshore winds. 


&& 


Long term /Tuesday night through Sunday/... 
overview... 
various large scale pattern changes advertised by medium range 
models during this forecast time period. Broad diffuse upper trough 
looks to persist through middle week along the eastern Seaboard 
followed by significant long wave amplification across North America 
toward end of the week into the weekend with very anomalous middle 
tropospheric height falls in the west and rises in the east. Then 
there looks to be a transition to a more zonal pattern for the 
following week. For southern New England...we start to experience 
building heights toward the end of the week only to have a strong 
enough short wave trough progressing across Canada to arrest this 
development and bring northwest flow aloft to the region by at least the 
second half of the Holiday weekend. Just how this unfolds will 
determine the sensible weather. The 00z GFS is a little faster in 
its cfropa compared with the 00z European model (ecmwf). 


Day to day details... 


Tuesday night through Thursday night... large scale pattern 
influenced by broad upper low over Middle Atlantic States that lifts 
out and diminishes as heights across New England and southeast Canada 
build. Conditions look marginally unstable Wednesday and to a lesser 
extent Thursday afternoon with relatively high precipitable waters  1.25 to 1.5 
inches. Am forecasting scattered diurnal convection Wednesday afternoon into 
the early evening and to a lesser extent Thursday afternoon. Note by 
Thursday that a low/middle level ridge builds from the northwest Atlantic into southeast 
Canada and northern New England. No significant forcing either day 
so any showers/thunderstorms may develop on fairly weak diffuse boundaries 
including any outflow boundaries. Just went slight chance southeast 
coastal areas where surface based instability is less. 


Friday... 
have gone with a dry solution as both GFS and European model (ecmwf) show ridging 
over the area. Gem brings significant low up coast on Friday but this 
appears to be an outlier without any support from other medium range 
models. 


Sat... 
strong short wave trough progressing across southern Canada has 
associated cold front that approaches Sat and then probably washes 
out as it moves S of the area Sat night and sun. European model (ecmwf) slower with 
timing than GFS which could prove correct considering the strength 
of the eastern ridge. Not much vertical wind shear shown at this 
time but unstable with moisture pooling to support chance thunderstorms Sat 
afternoon and evening. Activity might linger for a while Sat night 
along the S coast. Have moderate confidence in this solution due to 
reasonably good model continuity of this feature...although a 
stronger extension of the major eastern USA upper ridge could cause 
front to become delayed or stall prior to making it through the 
area. 


Sun... 
expect lower dewpoints but some disparity as to extent of cooling 
between GFS and European model (ecmwf). European model (ecmwf) does not flatten upper ridge as much as 
GFS...and in fact keeps 850 mb temperatures of 16c over the area. For now 
hedged a little warmer from GFS based solution to reflect this 
uncertainty. 


&& 


Aviation /18z Monday through Saturday/... 
forecaster confidence levels... 
low...less than 30 percent 
moderate...30 percent to 60 percent 
high...greater than 60 percent 


This afternoon...high confidence ceilings/low confidence visibilities 
model data show precipitation developing as this is being typed. But radar 
shows most of the action in NYC/western CT. Hints of 
sprinkles...but nothing upstream over the ocean. The constant is 
a moist low level east flow which should keep ceilings around 500 feet 
along the coast and around 15 hundred feet inland. We have cut 
back on precipitation to scattered/widely scattered levels and maintained 
fog/drizzle with minor visibility restrictions. 


Tonight...low-moderate confidence 
ceilings will remain around 500 feet along the coast and lower to 1000 
feet or below in the interior. Visibilities will lower after sunset...but 
the question is whether it will be from showers or from fog and 
drizzle. We have maintained a period of showers moving across 
southern New England...but with low confidence due to the lack of 
ground truth upwind. 


Tuesday...low confidence 
ceilings and visibilities will improve by midday...and may reach VFR in the 
interior. East coastal areas will improve to MVFR...but south 
coastal areas including Cape Cod should hold at IFR. Low pressure 
offshore will pass US around midday and move out to sea. This will 
bring changeable winds over New England during the afternoon. 


Tuesday night... 
light wind and lots of moisture will mean potential for fog/low 
clouds bringing widespread IFR/LIFR. 


Kbos taf...moderate confidence. Ceilings below 1000 feet this 
afternoon and below 500 feet at night. Visibilities at the surface may 
improve to unrestricted but will be 1-3 miles in fog just above 
the runways. Visibilities lower to 1 mile tonight with potential for 
periods of 1/2 mile. Improvement to MVFR ceilings and VFR visibilities on 
Tuesday. 


Kbdl taf...moderate confidence. MVFR ceilings will lower to IFR 
tonight. Showers and areas of light fog may bring MVFR visibilities. 


Outlook...Wednesday though Friday... 


Wednesday...moderate confidence. Mostly VFR except MVFR ceilings/visibilities in 
vicinity of scattered afternoon/early evening thunderstorms. 
Wednesday night...low to moderate confidence. Patchy stratus and fog with 
IFR cigs/vsbys. 
Thursday through Friday...moderate confidence. Mostly VFR conditions. 


&& 


Marine... 
moderate to high confidence in forecast through Tuesday. 


Expect S-southeast swells up to 7 feet to continue moving across the outer 
waters into the open south sounds through this period. Have extended 
small craft for hazardous seas for the waters east of Cape Cod 
southward through Tuesday...and will likely need to extend up the 
coast on Tuesday as low pressure passes. 


Expect winds to remain below small craft criteria through 
Tuesday...though low probability of brief 25 knots gusts early Tuesday 
on the eastern outer waters. 


Expect these swells to also produce moderate to high risk of rip 
currents along exposed South Coast beaches. 


Outlook...Tuesday night through Friday... 


Moderate confidence. Wave watch model looks reasonable for this 
period. Anticipate subsiding swells during this period. Only 
uncertainty is if Alberto retains a little more life than expected 
and keeps swell higher than currently expected for the middle week time 
period. No significant winds expected across the coastal waters 
during this time period. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Small Craft Advisory for hazardous seas until 6 PM EDT Tuesday 
for anz254>256. 


&& 


$$ 
Synopsis...evt/Thompson 
near term...wtb/evt/Thompson 
short term...evt 
long term...Thompson 
aviation...wtb/Thompson 
marine...evt/Thompson