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Area forecast discussion 
National Weather Service Taunton Massachusetts
1007 am EDT Wednesday Jul 29 2015

Synopsis...
hot and humid conditions today through Thursday. A cold front will
bring scattered thunderstorms late Thursday and Thursday night. Not
as warm and less humid weather is expected Friday into the weekend
and probably into early next week. While Friday through early next
week will be mainly dry...can/T rule out an afternoon and evening
thunderstorm each day.

&&

Near term /until 7 PM this evening/...

10 am update...

***a hot afternoon on tap for southern new england***

Upper level ridging and 850mb temperatures around +18c will result in a hot
afternoon. High temperatures will generally be in the lower to middle
90s...except along portions of the immediate coast where sea breezes
will keep it a bit cooler. Mostly sunny skies will probably become
partly sunny this afternoon as diurnal cumulus clouds develop. A
very isolated spot shower or two can not be ruled out by middle to late
afternoon...but if anything were to develop it would be extremely
isolated. Therefore...will not include in the forecast.

We opted to cancel the heat advisory for the Hartford/Springfield
metropolitan areas for this afternoon. Enough westerly winds in the
boundary layer should allow dewpoints to fall into the middle 60s.
So despite highs mainly in the middle 90s...heat index values may
fall 4 or 5 degrees short of criteria.

&&

Short term /7 PM this evening through 6 PM Thursday/...
tonight...

Dry weather will resume tonight. However there could be another
round of fog especially for the South Coast...cape and islands where
dewpoints will be highest. Otherwise a muggy and mild night will be
on tap with temperatures dropping into the low 70s.

Tomorrow...

Descent shortwave will move through the flow on Thursday pushing a
cold front across the area. Warm...humid airmass with southerly
flow will be in place ahead of this approaching front. The
southerly flow will allow for much of the region to have 70+
dewpoints. This will help keep temperatures slightly lower...in the upper
80s to low 90s. Heat indices will still be high...reaching into the
low to middle 90s.

00z guidance is in good agreement on timing of the front. In fact
most models have sped this system up by about 6+ hours. Showers
and thunderstorms will begin to move into the region around 18z and
push across the area by Thursday night. A few strong to a severe
storm is possible as instability will be quite high with marginal
middle-level lapse rates. Shear values look to be along or behind the
front...which could limit strong/severe potential. Biggest threat
with these storms appears to be heavy downpours leading to nuisance
flooding as precipitable water values are about 2+ inches. Gusty winds/localized
downburst also cannot be rule out due to the inverted-v soundings.

&&

Long term /Thursday night through Tuesday/...
highlights...

* pattern change to more seasonable temperatures is accompanied by showers
and thunderstorms Thursday night

* not as warm and humid Friday and beyond

* mainly dry weather prevails Friday through Tuesday

Synoptic overview and model preferences...

Impressive and anomalous vortex currently over southern Manitoba as
seen on the latest water vapor imagery will become the main weather
feature this period...as it evolves into a much broader circulation
over James and Hudson Bay this weekend and next week. This results
in a broad mean long wave trough setting up across the Great Lakes
and the northeast. This will suppress excessive heat and humidity
airmass currently over the area southward beginning Friday and
lasting through the weekend into early next week. Given good multi
model agreement among deterministic and ensemble guidance regarding
the large scale flow this period...forecast confidence is above
average.

Daily sensible weather details...

Thursday night...

Northern stream short wave and attending cold front move across the
area. Modest synoptic scale forcing associated with this feature.
While instability and shear is marginal in the prefrontal
environment...precipitable waters climb to 2+ inches /+2 Standard deviations above
climo/. Thus greater risk of heavy downpours and localized flooding.
Warm and muggy conditions prevail as Post frontal airmass doesn/T
arrive until Friday.

Friday through Tuesday...

Trend toward more seasonable temperatures and lower humidity arrives
Friday behind departing cold front with highs in the 80s and lows in
the 60s. Too difficult at this time range to time individual short
waves embedded in the cyclonic flow. So best wording would be many
hours of dry weather this period but cyclonic flow and cooler temperatures
aloft will result in the risk of a thunderstorm during peak heating
hours each day.

&&

Aviation /14z Wednesday through Sunday/...
forecaster confidence levels...

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

Short term /through Thursday/...

Today into tonight...high confidence in VFR conditions. May see
patchy fog overnight dropping conditions to IFR.

Thursday...VFR to start conditions dropping to MVFR in -shra/thunderstorms and rain
between 18-00z. A few strong storms are possible.

Kbos terminal...high confidence. Sea breeze continues into the
afternoon.

Kbdl terminal...high confidence.

Outlook /Thursday night through Sunday/...

Thursday night...MVFR and IFR in scattered showers/T-storms and fog.
Moderate to high forecast confidence.

Friday and Saturday...moderate to high confidence in VFR conditions.
Very low risk for an afternoon T-storm Saturday.

Sunday...moderate confidence for mainly VFR.

&&

Marine...
forecaster confidence levels...

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

Short term /tonight through Thursday/...high confidence.

Winds and seas below Small Craft Advisory today and tonight has high pressure will
be in place. Approaching cold front on Thursday will increase
winds along the southern waters. Could see some gusty near 25 kts.
Persisent southerly swell will increase seas between 4-6 feet. A
Small Craft Advisory may be needed on Thursday.

Outlook /Thursday night through Saturday/...

Thursday night...SW winds 15 to 20 knots with gusts up to 25 knots
possible. Rough seas on south ocean waters with wind waves of 3 to 6
feet possible. Visibility reduced in scattered showers/thunderstorms and fog.
Moderate to high forecast confidence.

Friday/Saturday and Sunday...cold front slowly moves offshore with
wind shift from south-southwest to west-southwest. Dry weather and good visibility. High forecast
confidence. Leftover southerly swells on south ocean waters from Thursday
night linger Friday but slowly diminish.

&&

Climate...
record highs for 7/29:

Boston97 on 1933 & 1931

Providence95 on 2002 & 1949

Bradley96 on 1933

Worcester94 on 1892

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...air quality alert until 11 PM EDT this evening for maz017>024.
Rhode Island...air quality alert until 11 PM EDT this evening for riz005>008.
Marine...none.

&&

$$
Synopsis...nocera/dunten
near term...Frank
short term...dunten
long term...nocera
aviation...nocera/dunten
marine...nocera/dunten
climate...staff

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