Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
647 am EDT Tuesday Sep 30 2014

cool temperatures expected through most of this week as
persistent northeast winds remain in place. One or two weak waves
of low pressure may bring a chance of showers for the region. An
approaching front with associated low pressure looks to affect
southern New England Friday night and Saturday.


Near term /until 6 PM this evening/...

7 am significant changes made at this time. Cool
northeast flow continues. Adjustments based on observed conditions
but general flow of the forecast remains the same.

Previous discussion...
northeasterly flow continues allowing for areas of
low clouds... fog...and drizzle through the morning hours. As the
boundary layer starts to mix a bit though...drizzle should come to
an end. A few steadier showers are possible across Rhode Island
and southeastern Massachusetts later today as a weak shortwave
moves across southern New England. Expect temperatures to be about
5 degrees below normal.


Short term /6 PM this evening through 6 PM Wednesday/...
tonight...expecting another night much like the last with low
pressure well southeast of Nantucket. Areas of low clouds...
fog...and drizzle are likely once again with very moist air in the
low levels. More widespread showers are possible across Rhode
Island and southeastern Massachusetts as the middle level low pushes
into southern New England. Overnight lows will be fairly mild
thanks to the low level humidity with most locations remaining in
the 50s. shot of showers as middle level low moves over
southern New England. These will likely be limited mainly to
southeastern Massachusetts and Rhode Island where the best lift
exists. Otherwise...more of the same low clouds...drizzle...and
fog. Overcast skies and wet weather will keep temperatures in the
low to middle 60s.


Long term /Wednesday night through Monday/...
big picture... Alaska shortwave digs over the western USA/Canada and
kicks the established upper trough east to the Great Lakes. This
brings a broad cyclonic flow over the eastern USA with below
normal heights while an upper ridge builds over the western USA.

Embedded in this flow...a closed low over New England Wednesday
night moves off through the Maritimes Thursday and Friday.

The dailies...

Wednesday night-Thursday... upper low over southern New England
moves off to the east. Lingering instability under the cold core
should support lingering showers Wednesday night tapering off
Thursday morning. Cross sections show plenty of moisture below 600
mb through Thursday midday followed by a drying trend in the
afternoon. Temperatures at the top of the mixed layer are equiv to 850 mb
temperatures of 2-5c...supporting maximum temperatures in the low to middle 60s. Moist
ground and cooling temperatures Thursday night will allow patchy fog to
form especially over the interior.

Friday... high pressure builds south over New England. Cross
sections of relative humidity show increasing cirrus-level moisture but dry through
most of the column...increasing low level moisture toward evening.
Overall...expect a fair weather day with light east to southeast
wind. Temperatures at the top of the mixed layer would support maximum temperatures in
the middle and upper 60s. The east flow may keep cooler temperatures near the
east mass coast.

Friday night-Saturday... shortwave driving around the deepening
eastern trough pushes a cold front across the Middle Atlantic States
Friday night and across New England on Saturday. The shortwave and
the supporting jet energy show signs of lifting through eastern New York
and Vermont...but with potential to directly affect southern New
England. Another concern would be the dry pattern we have been in
for several weeks...these patterns tend to maintain themselves even
when forecast data says otherwise. And a day 5 forecast is rather
far out to show great certainty. We will maintaining continuity with
probability of precipitation from the previous forecast and with adjoining offices...but our
actual confidence is 15-20 percent lower.

Sunday-Monday... high pressure builds up from the south and should
provide dry weather much of this period. The upper trough centered
to our west will bring lower heights over the Great Lakes which will
mean cooler temperatures. Temperatures here in New England should be a
little cooler than normal but expect the coldest temperatures to remain
west of New England with the axis of the trough.

A shortwave moves through the trough on Monday and southerly winds
ahead of the shortwave will bring higher moisture air our
way...generating some clouds and possibly showers. These
clouds/showers should hold until the shortwave gets
closer...probably Monday night.


Aviation /12z Tuesday through Saturday/...
forecaster confidence levels...

Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.

Short term...high confidence on trends but lower confidence in

Today...IFR conditions slowly improve from west to east. Showers
are possible particularly across eastern Massachusetts/Rhode Island where MVFR/IFR
conditions are likely to continue throughout the day.

Tonight...more of the same with IFR conditions likely in low
clouds...fog...and drizzle.

Wednesday...conditions improve once again at least temporarily in
the west. Showers are possible particularly across eastern MA/RI.

Kbos...high confidence on trends...lower confidence on timing.

Kbdl...high confidence on trends...lower confidence on timing.

Outlook...Wednesday night through Saturday...

Wednesday night-Thursday...cigs/vsbys at MVFR/IFR in lingering low
clouds and fog Wednesday night and Thursday morning. Conditions
should improve to VFR Thursday afternoon. Patchy IFR ceilings/visibilities in
fog after midnight Thursday night.


Saturday...conditions diminishing to MVFR in showers as a cold front
moves through. South winds lead the cold front...with winds
shifting to west after the front moves through.


forecaster confidence levels...

Low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.

Short term...high confidence through Wednesday.

Persistent northeasterly flow will result in building seas through
the period. Increased wave watch guidance by 20 percent to account
for a general low bias in this type of scenario. Small Craft Advisory continues for
the northeastern waters through this morning. Also issued Small Craft Advisory for
seas across the southern and southeastern outer waters for tonight
and Wednesday.

Outlook...Wednesday night through Saturday...moderate confidence.

Northeast winds Wednesday night through Friday with gusts near 20
knots. Winds shift to south Saturday ahead of the cold front...then
shift west after the cold front moves through. Wind gusts 20 to 25
knots possible on Saturday. Seas of 5 to 8 feet linger on the
exposed waters through much of the period. Expect Small Craft
Advisory on at least the exposed waters for much of the period.

May experience a storm surge of 1 to 1.5 feet during midweek but
the astronomical tides are not all that high.


Box watches/warnings/advisories...
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory until 11 am EDT this morning for anz250-
Small Craft Advisory from 10 PM this evening to 8 PM EDT
Wednesday for anz254>256.


near term...wtb/rlg
short term...rlg
long term...wtb

National Weather Service Glossary of Abbreviations