Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Taunton Massachusetts
948 am EDT Thursday Apr 24 2014

Synopsis...
windy and dry conditions today...then winds diminish tonight and
Friday as high pressure builds into the region. Low pressure will
bring rain Friday night into Saturday...then mainly dry and
seasonable conditions Sunday into Monday as high pressure returns.

&&

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

10 am update...

Earlier forecast on track with current conditions. Thus no major
changes expected. Abundant April sunshine will be offset by cold
air advection on gusty northwest winds. 12z observed sounding from Albany
New York has -4c temperatures at 850 mb. This supports highs in the low 50s but
given blyr will extend beyond 850 mb along with downsloping
winds...temperatures this afternoon should climb into the mu50s and near
60 in the coastal plain including Boston to Providence.

No wind headlines as previous shift mentioned as wind gusts should
remain below 46 miles per hour. Earlier discussion below.
-------------------------------------------------------------------

Middle level low moves offshore but cyclonic flow hangs on across
eastern new eng for the first half of the day. Sunny skies will
prevail but there may be a few extra clouds east coastal Massachusetts and
cape/islands. The main concern today is the strong northwest winds. Deep
mixing through 850 mb expected and using average of the mean wind
in the mixing layer and the wind at the top of the mixing layer
yields potential for gusts to 35-40 knots /40-45 mph/. This falls
just shy of Wind Advisory criteria so we will hold off on
headlines.

850 mb temperatures -2 to -3c support maximum temperatures mainly in the 50s today
with mildest readings approaching 60 degrees in CT/Rhode Island and east Massachusetts.

&&

Short term /6 PM this evening through 6 PM Friday/...
tonight...
gusty winds lingering into the evening...then winds diminish as
pressure gradient relaxes with high pressure approaching from the
west. Clear skies and diminishing wind will result in a cold night
with mins middle 20s to lower 30s across much of the region...except
upper 30s bos/pvd and Outer Cape/islands.

Friday...
high pressure moves across new eng then to the east by days end. Next
shortwave will be lifting NE from the Ohio Valley which will
result in an increase in middle/high clouds in the afternoon from the
west. It will remain dry as deep moisture transport associated with
the low level jet remains to the west through 00z. It will be a
milder day in developing warm air advection pattern. Soundings
show mixing to 850 mb where temperatures increase to 2-3c around 18z.
This supports temperatures into the low and middle 60s...but 50s along the S
coast due to southerly wind.

&&

Long term /Friday night through Wednesday/...
highlights...

* unsettled but seasonable weather Friday night into Saturday
* uncertainty higher than normal for next week

24/00z models are in decent agreement through much of the long term.
There are of course some discrepancies towards the end of the
period. A double barreled low pressure system will affect
southern New England Friday night and Saturday with some
uncertainty in how close the southern low moves to the southern
New England coast. The European model (ecmwf) is farthest from the coast...passing
over the 40/70 benchmark and the NAM is closest passing over
Nantucket. The European model (ecmwf) has trended north since the 12z run so went
with a NAM/GFS blend for this portion of the forecast. Beyond
this...models are struggling with a developing blocking pattern.
Models are quick to move towards a more progressive pattern.
Ensembles show the blocking pattern a bit better though there are
differences amongst the members as to whether we will be more
influenced by ridging or troughing. Between this and the models
tendency to rush a return to a more progressive pattern...have a
lower confidence than normal for next week.

Friday night and Saturday...double barrel low pressure moves east
across southern New England. The northern low moves through Quebec
while the southern low passes south of southern New England. The
European model (ecmwf) is the farthest south with the southern low while the NAM is
the farthest north. Expect scattered showers across southern New
England with this system. Steep middle level rates provide enough
instability for thunderstorms to occur and as such have mentioned
thunder in the grids.

Sunday into early next week...as stated above a more blocked pattern
looks to develop with middle level troughing over the NE bringing
unsettled weather to the region. Where exactly the blocked pattern
sets up will determine what sort of weather we are looking at. Some
models have a pronounced easterly flow which would result in
unseasonably cool temperatures and overcast skies across much of the
area. However...a shift could result in more seasonable weather.

&&

Aviation /14z Thursday through Monday/...
low...less than 30 percent.
Moderate...30 to 60 percent.
High...greater than 60 percent.

Short term /through Friday/...high confidence

10 am update...

No changes from 12z tafs. Confidence remains high in dry
runways/VFR and gusty northwest winds. Earlier discussion below.
--------------------------------------------------------

VFR through the period. Main concern will be gusty northwest winds today
as gusts to 35-40 knots expected. Winds will gradually diminish
tonight with light winds Friday.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Friday night through Monday...

Friday night and Saturday...moderate confidence. Mainly VFR. Brief
periods of MVFR/IFR conditions in rain showers/fog.

Sunday and Monday...low confidence. VFR.

&&

Marine...
forecaster confidence levels...

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

Short term /through Friday/...high confidence.

10 am update...

No major changes from previous forecast. Strongest winds near
shore given warmer land temperatures /55-60/ than ocean temperatures /low 40s/.
Earlier discussion below.
---------------------------------------------------------------

Northwest gales expected through today with gusts to 35-40 knots. Winds
diminish through tonight as gradient relaxes with light winds on
Friday as high pressure moves across the waters.

Outlook...Friday night through Monday...

Friday night and Saturday...low to moderate confidence. S winds
and seas increase as a cold front approaches the waters.
Visibilities may be reduced at times in rain showers. Small craft
advisories may be necessary on the outer waters. Winds shift to
the northwest as the cold front crosses the waters.

Sunday and Monday...moderate confidence. North/northwest winds and seas
generally remain below small craft criteria but conditions are
close. Small craft advisories may be needed.

&&

Fire weather...

10 am update...

No major changes from earlier discussion. Previous forecast
matching up nicely with current conditions.
-----------------------------------------------------------

Conditions today are favorable for fire weather headlines with
min relative humidity 15-25 percent and strong wind gusts to 40 miles per hour.
However...recent rainfall in central and eastern new eng will
preclude red flag conditions in these areas. However...less
rainfall occurred in the CT valley and after collaboration with
okx/aly we have decided to issue a red flag warning for north CT.

&&

Box watches/warnings/advisories...
CT...red flag warning until 8 PM EDT this evening for ctz002>004.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...Gale Warning until 8 PM EDT this evening for anz230>237-250-
251-254>256.

&&

$$
Synopsis...kjc/rlg
near term...kjc/nocera/rlg
short term...kjc
long term...rlg
aviation...kjc/nocera/rlg
marine...nocera/rlg
fire weather...