Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 241402
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1002 AM EDT SUN JUL 24 2016

.SYNOPSIS...
Excessive heat and humidity is expected at times through the
middle of next week, at least away from the immediate coast.
Another risk for scattered showers and thunderstorms is possible
late next week with a cold front dropping south.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
10 AM update...
Forecast remains on track. Expect highs topping out around 90 in
the CT valley and portions of RI and interior E MA, with 80s
elsewhere. Seabreezes develop this afternoon which will cool
temps a bit along the coast. Comfortable humidity levels with
dewpoints mixing out into the 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Tonight...
Outside of increasing high clouds late from convective debris
upstream, mainly quiet night with temps dropping into the 60s. The
initially SKC/weak pres gradient would help here, but expect
slight increase in dwpts thanks to return flow.

Mon...
Potential to be one of the hottest days of the summer thus far as
H85 temps will warm to +20C by afternoon. While this could easily
support temps in the mid to even upper 90s at several spots, there
is some question of the aforementioned cloud debris limiting
initial mixing/warming. It looks like enough breaks across the W
could support the heat across the CT valley, so will be issuing a
heat advisory there as dwpts surge back into the mid-upper 60s.
Not as confident elsewhere, but there is still some time to
monitor trends. More heat advisories could well be needed in the
next 24 hours.

The other issue, given the very hot/humid airmass return, will be
the risk for convective activity with an acute shortwave passage
late in the day on Mon. ML CAPE values are progged to be near
1500j/kg by the late afternoon, and this is on the normally
conservative ECMWF. This will come along with a decent cold pool
aloft with mid lvl lapse rates nearing 6.5C/km. Shear is minimal
to start but does increase through the day as the shortwave
approaches. Therefore, will need to monitor for afternoon/evening
strong-severe thunderstorm activity. Winds once again the primary
issue thanks to good D-CAPE values and increasing LLJ. This
correlates to current SPC Day 2 SWO. Given the lapse rates peak
late, this could be another instance of very late day convection
that lingers well into the overnight hours.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights...

* Excessive heat at times through mid week, at least away from the
  immediate coast

* Monday night is the highest risk for scattered showers and
  thunderstorms with the threat for some severe weather, and even
  very localized urban type flooding

* Cold front may bring another risk for scattered showers
  and thunderstorms sometime late this week but timing uncertain

Details...

Nearly zonal mid level flow persists through mid week, then
transitions to a broad trough. Latest guidance remain consistent on
this trend, with only minor variations in amplitude and timing. At
the surface, a subtropical high pressure will keep the above normal
temperatures and humid weather mainly in place. Will favor a
consensus solution to smooth over the minor differences.

Monday Night...

A weak cold front associated with a low pressure in Quebec is
expected to move across southern New England Monday night. While
this has been a consistent signal in the guidance the past several
days, we will need to watch if this boundary either washes out, or
stalls. If this boundary stalls, there may be a very localized urban
type flood threat, with precipitable water values around 2.0 inches.
Still some uncertainty at this point. Severe weather threat should
be diminishing with time, which is typical for our region.

Tuesday and Wednesday...

Assuming the weak cold front clears our region early Tuesday
morning, dry weather should prevail into Wednesday. High
temperatures should still be mainly in the 90s during this time away
from the immediate coast.  Should be less humid during this time, at
least compared to Monday.

Thursday through Saturday...

Above normal temperatures will continue over this time, but probably
not quite as hot as early this week.  A frontal boundary may
approach late this week, and bring the risk for another round or two
of showers and thunderstorms. The timing of any showers and
thunderstorms appears to be diurnal in nature, at this time. Not
looking like a washout.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels.

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

Short Term /through Monday/...

Today and tonight...high confidence.
VFR, only ACK may see some localized late night fog. Otherwise, NW
winds slacken through the day, allowing sea breezes to develop.

Monday...moderate confidence.
VFR starts the day, although very hot and hazy weather expected.
Late day, localized thunderstorms and showers may bring some
temporary IFR/MVFR conditions.

KBOS TAF...High confidence. VFR. Sea breeze expected today,
although start time may be an hour or so later than typical.

KBDL TAF...High confidence.

Outlook /Monday Night through Thursday/...

Monday night...Moderate confidence. Mainly VFR outside of lower
conditions in scattered showers and thunderstorms.

Tuesday and Wednesday...High confidence. Mainly VFR. Lower
confidence in a few hours of early morning patchy fog in the
typically prone locations.

Thursday...Moderate confidence. Mainly VFR. Briefly MVFR in
scattered showers and thunderstorms.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Monday/...High confidence.

Weak high pres builds over the waters today and lingers through
most of Monday. Quiet boating weather is expected for most of this
time.

There is a risk for late day thunderstorms Monday which will need
to be watched.

Outlook /Monday Night through Thursday/...Moderate to high confidence.

Winds and seas should generally remain below small craft advisory
thresholds over this time. The main concern is the risk for
scattered thunderstorms Monday night, and perhaps again on
Thursday.

&&

.EQUIPMENT...
The KBOX radar continues operating in a degraded state. Radar
returns are running about 10 dBZ too high. Please keep this in
mind when evaluating its data.

Technicians will be onsite later today to replace a defective
part. The radar will be out of service while this is done. We
apologize for the inconvenience.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 11 AM to 6 PM EDT Monday for CTZ002.
MA...Heat Advisory from 11 AM to 6 PM EDT Monday for MAZ010-011.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Belk/Doody
NEAR TERM...KJC/Doody
SHORT TERM...Doody
LONG TERM...Belk
AVIATION...Belk/Doody
MARINE...Belk/Doody
EQUIPMENT...


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