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Area forecast discussion 
National Weather Service Taunton Massachusetts 
740 PM EDT Wednesday Mar 17 2010 


Synopsis... 
high pressure building over the region will bring dry and 
unseasonably mild weather for the rest of the week and into the 
weekend. A cold front will likely bring a period of heavy rain 
showers and gusty winds late Sunday night into Monday. 


&& 


Near term /until 6 am Thursday morning/... 
the afternoon was mild...roughly 20f above normal middle March maximum 
temperatures. Amdar soundings showed a mixed layer up to 776 mb over Boston 
with temperatures of -4c at that level...equiv to about 4c at 850 mb. 


Weak cold front dives into northern New England but becomes aligned 
with northwest flow aloft...so it should stall and remain well north 
of our area. Limited cirrus may work into the forecast area during 
the overnight. Interior areas should decouple...allowing the wind to 
become light and temperatures to cool toward dewpoints...mostly into 
the 30s east and below freezing in the west. Temperatures are a blend 
of MOS. MOS dewpoints are too high compared with current values...so 
forecast dewpoints a blend of the NAM and the rgem. 


&& 


Short term /6 am Thursday morning through Thursday night/... 
Thursday...some increase in clouds but mostly high level. Otherwise 
mostly sunny. With the cold front to our north...the pressure 
gradient will be a little tighter than today and so it should keep 
winds westerly. This will allow for more mixing...and maximum temperatures will 
depend on how deep we mix. Temperatures aloft...800 mb will be 0 to -2c. 
So figure on 850 mb equivalents of 3-5c...which supports maximum temperatures of 
63 to 67f. Should be cooler along the South Coast/cape and islands. 


Thursday night...the cold front will shift south and bring additional 
clouds to southern New England...but overall a partly cloudy/mostly 
clear night. Dewpoints will be a little higher...supporting milder 
min temperatures. Min temperature forecast comes from a blend of MOS. 


&& 


Long term /Friday through Wednesday/... 
fairly quiet weather expected in the long term. One exception to 
this will be Sunday into Monday when a cold front is expected to 
move through southern New England. 


Friday and Saturday...low pressure moving across southeastern Canada 
will pull a weak cold front through southern New England Saturday. 
With very dry low level air in place...precipitation is unlikely to 
develop...so should be mostly just a wind shift. Temperatures will 
be 15 to 20 degrees above normal during the day with lows 10 to 15 
degrees above normal. Used a blend of available guidance for 
temps/winds. 


Sunday and Monday...low pressure moving through southeastern Canada 
with a middle-level trough will pull a cold front through southern New 
England sometime in this time frame. There is a timing discrepancy 
between the 00z European model (ecmwf) and the 12z GFS with the GFS a bit faster 
bringing the front through on Sunday. The 00z European model (ecmwf) doesn/T bring 
the front through until Monday. Either way...expect a decent period 
of showers along and ahead of the front. The models do show a 
strong low level jet over the area during the time just before the 
frontal passage as well as some decent instability which may lead to 
a period of gusty winds and thunder. Will keep a slight chance of 
thunder in the grids. Given the timing uncertainty in this latest 
model run...will keep probability of precipitation no higher than likely through this period 
with the highest probability of precipitation Sunday night and Monday where there is the 
biggest overlap between models. Temperatures remain 10 to 15 
degrees above normal Sunday with near normal temperatures Monday. 


Tuesday and Wednesday...dry weather returns with cold high 
pressure. Temperatures fall to near normal levels. 


&& 


Aviation /00z Thursday through Monday/... 
tonight through Thursday...VFR. High confidence. Some cirrus mainly 
Thursday. More substantial pressure gradient in place during the day 
Thursday so no sea breeze forecast for Boston. 


Thursday night...VFR. High clouds. High confidence. 


Outlook...Friday through Monday... 


Friday and Saturday...high confidence VFR. 


Sunday and Monday...low confidence forecast. VFR conditions 
deteriorating to MVFR/IFR in rain showers with a frontal passage. 
Models have frontal passage occurring either Sunday afternoon or during the 
day Monday. 


&& 


Marine... 
tonight...Small Craft Advisory for seas continues across the outer 
waters and Massachusetts Bay. Winds remain light. 


Thursday...Small Craft Advisory for seas continues through the 
evening south and east of Cape Cod and islands. Winds and seas small 
craft thresholds on the remaining waters. 


Thursday night...seas subside below 5 feet south and east of Cape 
Cod and islands. 


Outlook...Friday through Monday... 


Friday and Saturday...quiet weather with high pressure overhead. 
Light winds and 1 to 3 foot seas expected. 


Sunday and Monday...seas and winds increase ahead of a cold front. 
Rain showers likely. High probability of gale force winds on the 
outer waters. 


&& 


Hydrology... 
have cancelled river Flood Warning for the Merrimack River at 
Haverhill at 6 PM. River level has fallen below flood stage. Will 
likely be able to cancel a couple more points /Neponset at Norwood 
and the Merrimack at Lowell/ in the next hour or so. Also...appears 
that small streams across Rhode Island have receded...so will likely 
be able to cancel the areal Flood Warning for the state. 


Remainder of areal flood warnings will likely be extended at around 
9 PM. Several of the smaller rivers and streams remain in minor or 
moderate flood with the Taunton river at Bridgewater in major flood. 
Please see flood warnings and statements for more specific 
information about the status of individual rivers. 


Floods of record and final peak crests/flows for river gages are 
determined by the United States geological survey /USGS/. From a 
preliminary standpoint...it appears that the following rivers may 
have had their flood of record. 


Pawtuxet River at Cranston...preliminary crest at 14.98 feet shortly 
after 2 PM Monday. Previous record is 14.50 feet set in June 7 1982. 
Records go back to 1939. 


Charles River at Waltham...preliminary data indicates the river 
crested at 7.56 feet around 830 PM Monday. The previous record crest 
listed is 6.54 feet set on February 3 1976. Records go back to 1931. 


Shawsheen river at Wilmington...preliminary data indicates a crest 
of 10.59 feet around 845 PM Monday evening. The previous record crest 
listed was 10.49 feet set on Oct 22 1996. Records go back to 1963. 


The Taunton river at Bridgewater...as of this Wednesday morning the river 
was at 14.51 feet and nearing crest. The previous record crest for 
this location is 14.48 feet set on March 20 1968. With some 
gaps...records go back to 1929. 


Additional notes... 


Neponset river at Norwood...this past event was likely the highest 
crest since November of 1955. In November of 1955...the river reached 
11.32 feet. During this event...the river reached 11.07 feet at 215 
PM Monday. 


The river gage equipment for the Nashua River at East Pepperell maxed 
out yesterday and could not report any higher. River stage forecasts 
will continue to be produced for this location. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...Small Craft Advisory for hazardous seas until noon EDT 
Thursday for anz250-251-256. 
Small Craft Advisory for hazardous seas until 8 PM EDT 
Thursday for anz254-255. 


&& 


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

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