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National Weather Service CWSU
000
FXUS61 KBOX 170203
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1003 PM EDT Wed Aug 16 2017

.SYNOPSIS...
Dry and pleasant conditions continue into tomorrow. A weather
system moving through the Great Lakes Region towards the end of
the workweek will bring showers and scattered thunderstorms to
southern New England during Friday and Saturday. High pressure
returns with fair seasonable weather Sunday and Monday. A cold
front approaches from the west Tuesday and Wednesday, bringing
our next chance of showers.

&&

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

1000 PM Update...

Dewpoints continue to drop this evening as a few strato cu moves
through the area. Very comfortable conditions tonight as temps
drop into the 50s. Dry weather will prevail.

330 PM Discussion follows...

Very weak trof remains in place across S New England this
afternoon and has been the reason that dwpts are failing to mix
as well as previously forecast. Although dwpts are shifting into
the upper 50s, there remains a few low 60s this afternoon.
However, noting that the CU field continues to dissipate across
N New England suggesting that as the trof weakens (especially
this evening), the drier air should infiltrate the low lvls and
allow the dwpts to continue to diminish.

This gradual drop in dwpts, along with a trend toward SKC
conditions generally across the board, combined with a weak sfc
pres gradient should allow for a good radiational cooling night.
Mins look to drop into the 50s in most locations expect the
warmest heat islands. Cannot rule out a few upper 40s in the
most sheltered valleys of NW MA, but these would generally be
few and far between. Overall, a good sleeping night.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Tomorrow...
High pres crests over the region providing stout subsidence.
Despite the mostly sunny conditions this suggests, the
combination of suppressed mixing and a cooler start to the day
will lead to overall high temps a few degrees cooler than
yesterday. This is also in spite of generally W flow. Mainly
upper 70s and low 80s in the warmest spots where the downsloping
can be maximized. Overall a pleasant day especially with dwpts
remaining in the 50s.

Will still need to watch mainly exposed beaches across Cape Cod
and Nantucket, as the remnants of Gert continue to shift east, a
lingering swell could maintain a moderate risk for rip currents
through the day in these areas.

Tomorrow night...
A pleasant evening to start, however upper lvl wave will be
tilting and lifting through Ontario and Quebec with sfc wave
pushing a warm front toward New England. PWATs increase through
the overnight hours, such that by 12Z Fri, they near 2.00
inches (or nearly 2 std deviations above normal). Initial
overruning is weak and this moisture load is from the top of the
column to the sfc. Therefore, expecting only building clouds
through the evening, with the risk for any precipitation holding
off until the early morning hours. Indeed, timing of
measurable QPF has slowed on regional models due to this
initial lack of lift and dry column. Still could see some
wetting rainfall by sunrise mainly W of the Worcester hills in
MA and Thames river region of CT. Noting some QPF bullseyes,
but these are mostly likely some convective feedback. Column
remains relatively stable through 12Z.

The increased moisture from W-E will limit diurnal cooling in
spite of the weak pres gradient to start. Coolest areas will
likely be across E MA/RI, where some radiational cooling can
occur initially. Overnight mins range from the upper 50s in
these cooler spots to the low 60s elsewhere due to the increased
cloud cover.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Details...

Friday and Saturday... Moderate confidence.

During Friday and Saturday short waves move eastward thru our area,
with the upper ridge axis shifting offshore and upper trough moving
into the Great Lakes region, gradually approaching our area. Surface
high pressure slides further offshore while surface low churns thru
northern Great Lakes Region, heading towards southern Quebec.

On Friday a warm front associated with the Great Lakes surface low
lifts northward into our area. Southerly flow will bring deep
moisture to southern New England, with precipitable water values
increasing to around 2 inches by midday. This in conjunction with
short waves will allow for rain/showers Friday-Fri night. Lack of
surface-based CAPE on Friday, but surface LIs drop to 0 to
-2 and K indices mid 30s. Should be primarily showers but can`t rule
out rumbles of thunder. Could see brief heavy downpours.

During Saturday the surface low`s associated cold front advances
eastward through our region, while upper trough approaches from the
west. Models also indicate a zone of upper difluence affecting our
area. While deeper moisture axis shifts offshore, we still start the
day with precipitable water 1.5 inches or so across the eastern half
of the area, somewhat less later in the day. Cape values 500-1000
J/Kg. Expecting scattered showers with a chance of thunderstorms.

Max temps are expected to be mainly in the 70s on Friday. Airmass
warms several degrees Saturday with highs ranging from the upper 70s
to mid 80s. High dew points should contribute to areas of fog each
night/early morning.

Anticipating a drying trend Saturday night, however models hint at
potential for a weak surface low developing along the front in
northern New England as the upper trough passes thru New England, so
this could keep some clouds and a chance for light rain in our area
at least early. Patchy fog possible.

Sunday through Wednesday...

Upper trough lifts out during the Sunday with surface high pressure
building east into the area during Sunday and Monday. So
anticipating a period of mainly dry weather. Then the high moves
offshore Monday night and Tuesday, with increasing moisture later
Tuesday as another short wave and cold front approach from the west.
This could bring our next round of showers for late Tuesday-Tue
night and Wednesday.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

Short Term /through Thursday Night/...

Tonight into tomorrow...High confidence. VFR except some very
patchy ground fog early AM mainly at typically prone terminals.
Winds shift lightly W during the day except sea breezes along
coast.

Tomorrow night...Moderate confidence.
Area of rainfall accompanied by a mix of MVFR/IFR conditions
late, especially during the early Fri morning hours. VFR to
start the overnight. Winds shift to the S.

KBOS Terminal...High confidence in TAF. Sea breeze development
expected for Thu.

KBDL Terminal...High confidence in TAF.

Outlook /Friday through Monday/...

Friday through Monday... Moderate confidence.

Friday...Trending to MVFR/IFR in showers, scattered thunderstorms
and areas of fog.

Saturday...MVFR/IFR to start. Improving to VFR, except for possibly
the Cape and Islands where MVFR/IFR could linger thru the day. Then
localized MVFR/IFR Saturday night in patchy fog possible.

Sunday and Monday...VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

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

Noting seas have reached 8-9 ft along the open ocean waters S of
S New England as hurricane Gert begins its E shift. This will
allow these seas to gradually recede through the overnight
hours. Small craft advisories continue, but will be able to be
dropped as the night progresses. Otherwise, mainly quiet
boating weather continued into tomorrow night after these seas
recede.

Outlook /Friday through Monday/...

Friday...

Winds/seas below SCA thresholds to start, however during late
Friday/Fri night may see some southerly wind gusts to 25 kts. Seas
building to 3-5 feet Friday night. Increasing chance of showers west
to east during Friday. A Small Craft Advisory may be needed. Showers
and scattered thunderstorms Friday night and reduced visibility
in areas of fog.

Saturday...

Lingering showers and scattered thunderstorms Saturday, with reduced
visibility in patchy fog. Seas 3 to 6 feet on the outer waters,
and possibly the exposed portions of the southern waters,
subsiding during Sat night. Southerly winds Saturday turn to the
west Saturday night with gusts to 25 kts possible. A Small
Craft Advisory may be needed.

Sunday and Monday...

High pressure builds over the waters. Winds and seas expected to be
below SCA thresholds. Isolated showers possible early Sunday, but
these move off to the east during the morning.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory for hazardous seas until 8 AM EDT
     Thursday for ANZ254>256.
     Small Craft Advisory for hazardous seas until 3 AM EDT
     Thursday for ANZ235-237.

&&

$$
SYNOPSIS...Doody/NMB
NEAR TERM...Doody/Dunten
SHORT TERM...Doody
LONG TERM...NMB
AVIATION...Doody/NMB
MARINE...Doody/NMB

NWS BOX Office Area Forecast Discussion