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FXUS61 KBOX 302110
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
510 PM EDT Sun Apr 30 2017

.SYNOPSIS...
High pressure moves off the coast this evening, and a warm
front moves into southern New England Monday. The front lifts
to the north Monday night followed by a cold front late Monday
night and early Tuesday. Another low pressure center will push
toward the region Thursday, bringing periods of heavy rain late
Thursday through Friday night. Showers may continue into next
weekend as the low lingers across the region.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Modest elevated instability combined with low level theta-e
advection was enough for convective complex with showers and
sct t-storms to hold together as it moved across SNE this
afternoon. The showers have moved offshore but additional
showers are moving into the region from the west which may
linger through late afternoon.

High pres will move offshore tonight with a warm front
approaching SNE late tonight. Low clouds will develop overnight
from south to north with patchy drizzle likely given abundant
low level moisture and mid level dry air moving up from the
south. Also, can`t rule out a few showers overnight as 40 kt
low level jet moves into the region with increasing K indices.

The astronomical tide will be on the high side again...11.45
feet at Boston at 3:35 AM, but little in the way of storm surge
is expected, with southeast winds around 10 mph so not
expecting much in the way of splashover.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday...
The warm front moves into SNE but will likely stall across the
region. Low confidence temp forecast in the vicinity of the
front where large temp gradient is expected. South and west of
the front temps may soar into the lower 70s with the lower CT
valley having the best chance to realize these warmer temps.
Further NE, especially across north central and NE MA temps may
remain in the 50s with E/NE winds as front will likely struggle
to make it that far north. Where the front sets up will be
critical to the temp forecast.

Expect areas of low clouds, drizzle and patchy fog in the
morning, then some improvement into the afternoon, especially
lower CT valley and south coast where some breaks of sun are
possible. Low clouds may persist along and north of the warm
front, especially NE MA. Models indicate pronounced mid level
drying moving into the region Mon along with decreasing K
indices in the coastal plain. This should preclude any
convection or shower activity with main axis of deeper moisture
and instability well to the west, moving across western and
central NY in the afternoon.

Monday night...
Cold front approaches from the west and moves into SNE late Mon
night. Hi-res guidance indicating a line of convection weakening
as it moves east from central NY as no sfc instability is
forecast in New Eng. However, low level jet of 50+ kts, deep
moisture plume and elevated instability will help to bring
showers and a few t-storms into the region. PWAT plume is 3SD
above normal while wind anomalies weaken to +2SD which is
sufficient for locally brief heavy rainfall. There may be some
gusty SW winds developing in the coastal plain as the low level
jet moves in. A low level inversion may keep the stronger gusts
from reaching the surface but any convection may help with
momentum transfer. Something that needs to be monitored. Mild
night as warm front lifts to the north. Temps remaining in the
50s with some lower 60s possible.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...

Overview...
Continue to see model suite and ensembles signal mid level
cutoff low pressure opening up as it crosses the Great Lakes
into southern Canada during the Tuesday-Wednesday timeframe.
Models handling this aspect quite well.

However, once that system shifts to the Maritimes, still
dealing with potential of strengthening low pressure moving out
of the southern Gulf states later this week. Still some timing
issues, but operational models appear to have a better handle in
bringing associated southern stream H5 cutoff NE, though the
GFS still not quite as strong as the GGEM and ECMWF or their
ensemble means. Have noted that the models` handling of the
surface system appears to be in. Timing is a bit slower in
bringing the heavier precipitation into the region...mainly from
late Thursday through at least Friday night, possibly into
early next weekend. Still lower than average confidence overall,
but continued to lean toward a non-GFS solution during the
brunt of the storm Thu night into Sat morning.

Details...

Tuesday...Moderate confidence.
Cold front clears the coast Tue morning, but showers do linger
along the S coast and across N central and NW Mass through at
least midday as the dry slot moves across most of the region.
With the main surface and upper low moving into central Canada,
will still see SW wind flow in place.

Strong low level SW jet moves out of the region Tue morning,
but winds will remain gusty once the sun comes out and allows
for potential maximum low level mixing that will be in place
from H95- H85. Could see gusts up to around 25 kt, possibly a
bit higher along the S coast, Cape Cod and the islands. Expect
high temps to run in the 70-75 degree range away from the S
coast.

Wednesday...Moderate confidence.
Weak high pressure builds across the region during the day.
Noting an H5 short wave moving across during Wed, so could see a
period of diurnal clouds develop across inland areas, away from
the coastal plain. Expect a mainly dry day, except for some
isold showers possible across the E slopes of the Berkshires.
Temps will run near or slightly below seasonal normals.

Thursday-Friday night...Moderate confidence.
Thursday starts off dry, then leading edge of rain shield moves
in from the SW during the day.

Looks like another potential soaker to move across from Thu
night through Fri night. Expect best chance for heaviest
rainfall during the Fri into Fri evening timeframe. Excellent
shot of tropical moisture transport thanks to moisture plume
moving out of the Gulf of Mexico. PWATs increase to 1.5 to 1.6
inches by Fri. Also noting strong SE-S low level jet moves
across late Thu night and especially Fri, on order of 50-60 kt.
Have also mentioned potential for thunderstorms during Friday,
mainly across RI/SE Mass.

Will still see periods of moderate rain Fri night, but best
dynamics look to shift out of the region.

Saturday-Sunday...Low confidence.
Long wave trough lies W of the region, mainly across the
Appalachians through most of this period. Will still showers
from time to time with the cold pool aloft linger near or west
of the region, though could be mainly diurnally driven both
days. Have carried chance POPs at this point.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

Short term...through Monday.

Through 00z...Brief MVFR in showers eastern MA until 19z,
otherwise VFR.

Tonight...Moderate confidence.
Conditions deteriorating to MVFR/IFR after midnight as stratus
and patchy drizzle develops. Areas of fog developing along the
south coast toward daybreak.

Monday...Moderate confidence.
IFR/LIFR cigs with patchy fog in the morning. Conditions may
improve to MVFR/VFR in the afternoon CT valley and near the
south coast, but likely remaining IFR central and NE MA. Patchy
drizzle in the morning along with a few showers possible.

Monday night...Moderate confidence.
Widespread IFR/LIFR likely eastern New Eng and lowering to IFR
in the west with area of showers and a few t-storms moving
through from west to east. Gusty SW winds developing in the
coastal plain. Areas of LLWS near the south coast with SW winds
45-55 kt at 2k ft.

KBOS TAF...High confidence in trends. Lower confidence in
timing.

KBDL TAF...High confidence in trends. Lower confidence in
timing.

Outlook /Tuesday through Friday/...

Tuesday...High confidence.
MVFR-IFR CIGS linger through midday in leftover showers and
patchy fog, then improve to mainly VFR. A few showers may linger
across N Mass during the afternoon. Chance of TSRA across Cape
Cod and the island through mid morning. LLWS with SW winds up to
45-50 kt along S coastal areas early Fri.

Wednesday-Wednesday night...High confidence. VFR.

Thursday-Friday...Moderate confidence.
Mainly VFR Thursday. Area of light rain moves in during
Thursday. CIGS/VSBYS lower to MVFR Thu night with some patchy
fog. Rain will be heavy at times Fri. Mainly MVFR-IFR CIGS/MVFR
VSBYS, but may see periods of IFR-LIFR CIGS during Fri. Chance
of thunderstorms on Fri into Fri evening across RI/SE Mass.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Monday Night/...

Tonight...High confidence.
Mainly SE winds less than 20 kts with seas below SCA. Vsbys
lowering in fog toward daybreak over the south coastal waters.
Patchy drizzle developing.

Monday...Moderate confidence.
Warm front moves into the waters Monday. SE winds become SW
south of the front, mainly over the southern waters, while
easterly winds will persist across NE MA waters. Wind speeds
should remain below SCA. Visibility restrictions in areas of
drizzle and patchy fog through early Monday afternoon.

Monday night...Moderate confidence.
SE winds become SW across NE MA waters, otherwise increasing SW
winds with gusts 25-30 kt developing, especially south coastal
waters with building seas. SCA will be needed with low risk for
gales but strong inversion will likely keep winds below gale
force. Vsbys reduced in showers and fog. Isold t-storms
possible.

Outlook /Tuesday through Friday/...

Tuesday...Moderate confidence.
SW winds will gust up to around 30 kt from Cape Cod southward,
diminishing Tue night. Seas will remain high, up to 7-9 ft on
the southern open waters, but may subside below 5 ft on the
eastern open waters by Tue night. Showers linger mainly over the
eastern waters, with scattered thunderstorms possible across
the waters near Cape Cod and the island Tue, but will push
offshore by Tue night with improving conditions. Small crafts
likely continue.

Wednesday...Moderate confidence.
W winds may gust to 25 kt at times on the southern open waters
during Wed, diminishing Wed night. Seas remain at or above 5 ft
across the southern outer waters, lingering around 5 ft S and E
of Nantucket Wed night.

Thursday...Moderate confidence.
Expect winds and seas below small craft criteria. Visibility
restrictions move in from W-E in light rain during the day.

Thursday night-Friday...Low to moderate confidence.
E-SE winds increase Thu night, gusting to 25-30 kt on the
southern waters after midnight. SE winds may gust to around 35
kt on the waters from Plymouth south during Fri. Gales possible.
Seas build up to 7-10 ft Fri afternoon/night on the outer
waters. Thunderstorms possible Fri into Fri evening. Visibility
restrictions in periods of heavy rain.

&&

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

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...KJC/EVT
MARINE...KJC/EVT

NWS BOX Office Area Forecast Discussion