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000
FXUS61 KBOX 190706
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
306 AM EDT Fri Apr 19 2024

.SYNOPSIS...

Partial sunshine and seasonable temperatures return to the region
today...but it will be cooler on the immediate coast. An approaching
cold front will bring a period of showers and a few downpours very
late tonight into Saturday morning. Gradual partial clearing and
pleasant temperatures are in store for later Saturday. Elevated fire
weather potential possible Sunday through Tuesday due dry and
gusty winds. Our next opportunity for unsettled wet weather
returns mid week with colder temperatures.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

305 AM Update...

* Partly sunny today with highs near 60...but 50-55 on the coast

Considerable mid-level cloudiness covered the region very early this
morning with even a left over spot shower. Brief upper level ridging
does build into the region today. This should probably result in
enough subsidence for a period of partial sunshine later this
morning and afternoon. Confidence on sky conditions today is a lower
than normal for a near term forecast...so later shifts may need to
make adjustments. Given the mild start...this should be enough to
push high temps to near 60 in most locations. However...onshore
surface winds will keep high temperatures generally in the 50 to 55
degree range along much of the immediate coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

Key Points...

* Period of showers late tonight into Saturday am with some downpours
* Partial sunshine returns later Sat with highs well into the 60s

Details...

Tonight and Saturday...

A cold front/shortwave will be approaching the region late tonight
into Saturday morning. The guidance has increased the low level
moisture return & forcing associated with this front over its last
few cycles. A modest southwest LLJ coupled with Pwats increasing to
over 1 inch support a period of widespread showers late tonight
into Sat morning. We also expect some downpours given this
combination. There is even a low risk for a rumble of thunder...but
did not feel it was worth inserting into the forecast at this point.

Most of the showers will have exited the coast by Saturday
afternoon. In fact...we expect some partial sunshine to develop
from west to east as drier air works into the region. Despite
cooling temps aloft...a mild start and the increasing April sun
angle should push afternoon highs well into the 60s across most
locations. While generally dry weather is expected Saturday
afternoon...enough heating coupled with a cold pool aloft may
trigger a few brief spot showers.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

Highlights

* Dry and breezy Sun through Tue. Elevated fire weather concerns
  possible.

* Shower chances return late Tue through Wed. Temps trending cooler.

* Turning drier on Thu with much colder temps.

Saturday Night through Tuesday...

Cyclonic flow in place through this timeframe. Will have a shortwave
skirt through New England on Sun. A southern stream trough will
remain shunted well to our south of Mon. Another trough slides
into/across the Great Lakes on Tue. A mid level ridge builds from
the Northern Plains late Sat into the Great Lakes/Mississippi River
Valley by early Mon and into/offshore of New England by late Tue.
High pressure begins nudging into our region from the center of the
country late Sat/Sun. The high builds into the Lower Mississippi
River Valley to OH Valley by late Mon and offshore on Tue.

Dry and quiet weather expected through this timeframe. Though there
could be a few lingering showers tapering off late Sat. Main concern
during this timeframe is elevated fire weather concerns. Despite the
high nudging in we remain gusty Sun/Mon due to a tightened pressure
gradient between the high and the lows well off to our north and
east. The GFS and NAM both show we should be able to mix to roughly
800 hPa per Bufkit soundings. The GFS also shows us being this well
mixed on Tue as well. This should allow drier air to mix down fairly
easily aloft. With this in mind and given the pre-greenup have
increased temps and lowered dew points/RH values during this
timeframe from the default NBM. As we saw earlier in the week we
tend to overachieve in these set ups, so am anticipating the same.
At this point though am more confident for the Sun/Mon timeframe
given upper flow will be out of the W/WNW, which will aid in
downsloping. Could be a bit tougher on Tue as winds turn southerly
ahead of our next incoming system. Increased temps to the 75th
percentile of guidance for now and results in temps ranging from the
upper 50s to mid 60s. Lowered RH/dew points to the 10th percentile
of guidance for Sun/Mon and the 25th for Tue. Min RH values
bottoming out in the mid 20s to the low 40s. Given the 20-30 mph
gusts there could be elevated fire weather concerns.

Tuesday Night through Thursday...

Another period where we are caught in cyclonic flow. A trough will
dig into the Great Lakes region Tue Night into early Wed. The
trough/cutoff digs into New England on Wed. The trough/cutoff may
still be overhead or kicked out of the region on Thu. Our next
opportunity for unsettled/wet weather late Tue into Wed as a system
slides in and perhaps through. The system may still be nearby on Thu.

A cold frontal system swings through New England late Tue through
Wed. At this point appears that the be opportunity for widespread
rain showers comes during the Wed timeframe. The PWAT plume not
appearing overly impressive with only low probs (10-20 percent) of
PWATs AOA 1 inch per the EPS/GEFS and GEPS. Do have a deeper S/SWly
low level jet at 850 hPa, which could really help squeeze out the
moisture available. At this point deterministic guidance show
roughly 30-50+ kt jet in place. Should remain mild as the system is
swinging through, so precip will be all rain. However, as things are
winding down much colder air filters in late Wed into early Thu.
Would not be surprised if there are some snowflakes mixing in. At
this point total precip appearing to be generally between 0.1 and
0.5 inches. We`ve got mod to high (30-80+ percent) probs of totals
AOA 0.1 inches and low probs (10-30 percent) of 0.5 inches. For now
have just stuck with WPC.

Will be seeing temperatures trending downward through this
timeframe. Much cooler on Thu with highs in the 50s.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...

Forecast Confidence Levels:

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

06z TAF Update...

Today...High Confidence.

VFR. SSE winds 5 to 15 knots.

Tonight and Saturday...High Confidence.

An approaching cold front will bring a period of MVFR-IFR
conditions very late tonight into Sat morning. This will also be
accompanied by several hours of showers with a few downpours
too. Most locations should see conditions improve to VFR by
early Saturday afternoon...but this process may take a few hours
longer towards the Cape and Islands. S winds 5 to 10 knots
tonight becoming W at 10 to 15 knots by Sat afternoon. A few
gusts in the 20 to 25 knot range may also develop across the
interior by mid to late afternoon.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night through Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday: VFR. Breezy.

&&

.MARINE...

Forecaster Confidence Levels:

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

Today through Saturday...High Confidence.

Continued small craft headlines this morning for our far southwest
waters from leftover lingering marginal 5 foot swell...but these
should diminish by early afternoon. Otherwise...a relatively weak
pressure gradient should keeps winds & seas below small craft
advisory thresholds into Saturday.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Winds less than 25 kt.

Sunday through Sunday Night: Winds less than 25 kt. Seas
locally approaching 5 ft.

Monday through Monday Night: Winds less than 25 kt.

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas locally approaching 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 1 PM EDT this afternoon for ANZ255-
     256.

&&

$$

SYNOPSIS...Frank/BL
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...BL
AVIATION...Frank/BL
MARINE...Frank/BL