NWS Forecast Area Discussion - New England Area

000
FXUS61 KBOX 221946
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
346 PM EDT Fri Jun 22 2018

.SYNOPSIS...
High pressure that was centered over northern New England moves
offshore but keeps our region mainly dry tonight. Scattered showers
and a few thunderstorms are expected at times this weekend...but
it is uncertain if any activity will linger into Monday. Mainly
dry weather with seasonable temperatures anticipated Tuesday
and Wednesday with a ridge of high pressure in control. Summer
heat and humidity should return by the end of next week as this
high moves east of the region.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

Tonight...

The high pressure that was centered over northern New England this
afternoon moves offshore tonight. Our area remains in an E/SE flow
with increasing moisture as a low pressure system in the Midwest and
its associated warm front move gradually ENE-ward. Mainly expect an
increase/thickening in cloud cover over our area. Could see some
showers towards daybreak but model soundings show a lot of dry air
to overcome, so will limit pops to chance/slight chance towards
daybreak. Lows mainly in the 50s.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...

Saturday...

A warm front lifts NE-ward during the day, and may reach the south
coast of New England around 00Z. Increasing moisture is
expected throughout southern New England, with precipitable
water increasing to 1.5 inches or higher. The approach of the
front will provide lift, allowing for the development of showers
across our area. Planning on going with likely pops. While it
doesn`t look to be a washout for the full day, hi-res guidance
is in agreement on areas of showers moving thru the region.

Model thermal profiles show a low level inversion which makes sense
given warm front to the S, and an onshore/E wind providing a cooler
marine influence near the surface. However some elevated instability
is anticipated, which should yield isolated thunderstorms and
the potential for brief locally heavy rainfall. Plan to go with
likely pops and considerable cloudiness. High temps will be on
the low side, only reaching into the 60s. A few spots might
reach 70.

Saturday night...

Warm front lingers in our vicinity Sat night, accompanied by a 30-40
kt low level jet. This will continue to provide a lifting mechanism
for showers. Precipitable water values remain at or above 1.5
inches, so brief locally heavy rainfall is possible. Model
soundings showing continued elevated instability. Will continue
with likely pops, with isolated thunderstorms. Best chance for
thunder is probably along south coastal MA/RI, closer to the low
level jet. Areas of fog developing.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...

* Warmer with scattered showers and t-storms on Sunday
* Mainly dry/seasonable temps with comfortable humidity Tue and Wed
* Summer heat/humidity should return by the end of next week

Details...

Sunday...

The warm front will lift north of most locations Sunday
morning...allowing a warmer and more humid airmass to move into the
region.  High temps should reach into the upper 70s and lower 80s
despite potential for a fair amount of clouds.  We may see a period
of partial sunshine though and if that does occur a few middle 80s
would be possible.

The main concern will be Sun afternoon/evening when a pre-frontal
trough/cold front approach from the west.  There probably should be
enough instability for scattered showers and a few thunderstorms
during that time.  If we can muster 1000 J/KG of MLCape...which is
dependent on solar insolation and amount of low level moisture
return a few strong thunderstorms would be possible. 0 to 6 km shear
is on the order of 30 to 40 knots...but mid level lapse rates are
weak and we will not have the anomalous environment that we saw last
Monday. Nonetheless...a few strong thunderstorms with gusty winds
and heavy rainfall are possible if enough instability can be
realized.

Monday...

A vigorous shortwave/cold pool aloft will drop southeast into the
Northeast on Monday.  The GFS is most aggressive showing the
anomalous cold pool dropping furthest south into our region with
500T dropping below -20C.  This scenario would likely produce
scattered showers and thunderstorms along with some hail given such
cold temperatures aloft.  While this solution is possible, appears
to be a low probability at this time given the rest of the guidance
is further north and east with the cold pool...resulting in mainly
dry weather.  Therefore...will just include some low pops for now
and see how the models trend over the next 24 hours.

Tuesday and Wednesday...

Mainly dry and pleasant early summer weather with a ridge of high
pressure in control.  High temperatures will mainly be in the upper
70s to the middle 80s along with comfortable humidity levels.

Thursday and Friday...

A pattern change to more summerlike warmth and humidity expected Thu
and Fri as upper level ridging builds to sour south...resulting in
rising height fields in southern New England.  Highs should be well
up into the 80s to perhaps over 90...but specific details this far
out remain uncertain.  Dry weather probably dominates...but a few
showers/t-storms can not be ruled out.


&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...High confidence thru
tonight, then moderate confidence.

Thru 00Z...VFR conditions hold for the remainder of this
afternoon, except for some localized IFR stratus Block Island
and south coastal RI. E/SE winds persist.

Tonight...Areas of fog may form in the vicinity of the Cape and
Islands, bringing localized MVFR-IFR conditions. Otherwise,
VFR. Scattered -SHRA develop towards 09Z-12Z.

Saturday...Scattered SHRA continue across the region, with isolated
TSRA. MVFR/IFR to start along the south coast/Cape/Islands, VFR
elsewhere to start but deteriorating to MVFR/IFR during the day.

Saturday night...Mainly MVFR/IFR conditions in areas of showers
and fog. Isolated TSRA.

KBOS Terminal...High confidence in TAF thru tonight, then
moderate confidence. VFR thru tonight, deteriorating to MVFR
Sat morning then IFR towards 00Z Sat.

KBDL Terminal...High confidence in TAF thru tonight, then
moderate confidence. VFR thru tonight, deteriorating to MVFR
Sat morning then IFR towards 00Z Sat.

Outlook /Sunday through Wednesday/...Moderate confidence.

Sunday: Mainly VFR, with local IFR possible. Chance SHRA,
slight chance TSRA.

Sunday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, slight chance TSRA, patchy BR.

Monday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA, isolated TSRA.

Monday Night: VFR.

Tuesday through Wednesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Saturday Night/...High confidence.

Tonight and Saturday...E-SE winds in place. A few gusts approaching
25 kt on the southern outer waters late tonight into early Saturday.
Visibility restriction in areas of fog along the southern waters
late tonight, then in showers and areas of fog moving in from S-N
during Sat. Isolated thunderstorms possible during Sat.

Saturday Night...SW winds less than 25 kt. Seas approaching 5 ft on
the southern outer coastal waters. Showers likely with isolated
thunderstorms. Areas of fog visibility 2-3 nm or less.

Outlook /Sunday through Wednesday/...Moderate confidence.

Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers, isolated thunderstorms, patchy
fog.

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers, isolated thunderstorms,
patchy fog. Local visibility 1 to 3 nm.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Slight chance of rain showers,
isolated thunderstorms.

Monday Night: Winds less than 25 kt. Seas up to 5 ft.

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Tuesday Night: Winds less than 25 kt. Seas up to 5 ft.

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Frank/NMB
NEAR TERM...NMB
SHORT TERM...NMB
LONG TERM...Frank
AVIATION...Frank/NMB
MARINE...Frank/NMB

NWS BOX Office Area Forecast Discussion