National Weather Service Forecast Discussion

Forecast Discussion for BOX NWS Office
000
FXUS61 KBOX 190732
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
332 AM EDT Tue Mar 19 2024

.SYNOPSIS...
Outside of a few rouge showers it will be largely dry today and
through the daylight hours of Wednesday. Gusty wind persists into
Wednesday with a brief lull tonight. Scattered rain and snow
showers will accompany a cold front passage late Wednesday and
Wednesday evening, followed by windy and colder conditions late
Wednesday night and Thursday. High pressure builds into the
region Friday, then low pressure will likely bring rain Saturday
which may begin as a period of accumulating snow across
portions of the interior.

&&

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

* Noticeably cooler with diurnal CU developing late morning through
  the afternoon.

A quiet Saint Joseph`s Day across southern New England, with no
weather concerns for those traveling to their nearest Italian bakery
for a zeppole! Mid-level trough will move off shore today with the
flow aloft westerly to west/northwesterly. Expecting a breezy west
wind to continue through the day, BUFKIT soundings depict a well
mixed boundary layer, perhaps mixing to 800mb as the RAP and NAM
would suggest. Gusting periodically 20 to 30 mph. As we are tapping
into to cooler temperatures aloft, 850mb temperatures are roughly
around -10C, which is -5C colder than the what is average for middle
of March. Afternoon highs are in the 40s, lower 40s across northern
Massachusetts, middle 40s across the coastal plain, urban centers of
Boston, Hartford, and Providence are 45F-48F. But, adding in the
gusty wind, it will feel as if it were in the 30s.

Similar to Monday, we do expect diurnal CU to develop once again. A
rather dry atmosphere, PWATs less than 1/4" inch will result in a
very low chance of a spot sprinkle or flurry. Latest high-res
guidance paints a VERY isolated chance, likely due strong mid-level
forcing as the mid-level trough pushes off shore. As the probability
is low, opt to leave it out of the grids, but rather mention in the
AFD.&&

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

* Spotty shower possible overnight for far northwest Massachusetts.

* Mild temperatures on Wednesday, spotty shower possible during the
  day, better chance comes late Wednesday.

Tonight: Increasing cloud cover, wind shifts more southwest with
diminishing wind speeds. Spot snow showers are possible across far
northwest Massachusetts do to orographic upslope on the west side of
the Berkshires. PWATs are low, but the SLR are around 16:1, perhaps
a coating of snow, to an half inch for locations AOA 1500 feet. Lows
fall to either side of freezing.

Wednesday: Mid-level warm front moves from south to north during the
day, a spot shower or two possible, otherwise dry. PWATs increase
from WAA to 0.3 to 0.5 this is more or less near normal for mid
March. With the lack of forcing, do not expect much in the way of
showers. The better forcing with the negatively tilted mid-level
trough will come in later, Wednesday night with better chance of
showers and usher in much cooler conditions. More on that in the
long term discussion. Wednesday does feature more gusty wind, this
time it is out of the southwest between 25 to 30 mph. High
temperatures recover to the upper 40s across the interior to the low
50s for the coastal plain.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Points...

* Scattered rain and snow showers Wednesday evening
* Windy and colder Thursday with diminishing wind Friday
* Increasing chances for more significant precipitation Saturday,
  although uncertainty in track of low pressure remains high

Wednesday night into Friday...

Strong shortwave and cold front passage will be accompanied by
scattered rain or elevation snow showers which will become focused
across eastern New Eng Wed evening. Then front moves offshore before
midnight followed by colder and much drier airmass overnight and Thu
as PWATs drop to near 0.10". This will lead to plentiful sunshine
Thu but it come with windy conditions. Winds will ramp up in the
cold advection overnight Wed night with peak of the wind during Thu.
WNW gusts to 30-40 mph expected with possible gusts 40-50 mph over
the higher elevations and wind advisories may eventually be needed.
Chilly airmass as 850 mb temps bottom out at -12 to -15C Thu morning
with temps well below normal. Highs Thu will range from the mid 30s
higher terrain to lower 40s near the coast, with gusty winds making
it feel much colder.

Winds diminish on Friday as high pres builds in from the west.
Continued dry airmass with lots of sunshine and temps remaining below
normal with highs upper 30s to low/mid 40s.

Friday night into Monday...

Still considerable spread in the deterministic and ensemble guidance
regarding potential impacts from a possible coastal storm through
the weekend. Looks like there will be an initial surge of warm
advection precip late Fri night into Sat as southern stream moisture
lifts north into SNE along an inverted trough/surface wave. With
antecedent cold air initially in place, precip may start as snow,
especially interior with some accum possible before changing to rain
during Sat. While forecast confidence is below normal for Sat,
confidence decreases significantly beyond Sat. Complex upper level
pattern with uncertainty how northern stream energy interacts with
southern stream system. ECMWF and Canadian maintain a split flow
with southern stream low remaining to the south into Monday with
persistent easterly low level jet and deep moisture plume leading to
wet weather and gusty winds lingering into Sun-Mon. GFS shows more
phasing with northern and southern stream low pres impacting region
Sat with potentially heavy rainfall, then system moves off to the
east with drying conditions Sun-Mon. Due to large spread in the
guidance we leaned toward NBM for the Sat-Mon period which offers
high pops for Sat, then drying out Sun-Mon. But confidence is very
low and large forecast adjustments will likely be needed.

Astronomical tides this weekend are low with Boston around 9.5 ft
through Mon. However, if ECMWF solution is closer to reality,
persistent easterly flow will likely build seas and surge enough for
the potential for minor flooding and beach erosion over multiple
tide cycles.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

Today... High Confidence.

VFR. West/northwest 10 to 15 knots with gusts of 20 to 25 knots. Another
round of mid level CU with bases of 5-8 kft.

Tonight... High Confidence.

VFR. Decreasing winds turning south/southwest less than 10 knots.

Wednesday... High Confidence.

VFR. Southwest winds 10 to 15 knots with gusts of 20 to 25 knots.
Another round of mid level CU with bases of 5-8 kft. Low chance for
a spot rain shower or snow shower in higher terrain of northwest
Massachusetts.

KBOS TAF... High confidence.

KBDL TAF... High confidence.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR. Strong winds with local gusts up to
40 kt. Slight chance SHRA.

Thursday: VFR. Strong winds with gusts up to 45 kt.

Thursday Night: VFR. Strong winds with local gusts up to 40 kt.

Friday: VFR. Windy with local gusts up to 30 kt.

Friday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SN, chance RA.

Saturday: MVFR/IFR conditions possible. Windy with gusts up to
30 kt. RA likely.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Wednesday... High Confidence.

Dry conditions today and tonight, increasing rain chances late
Wednesday afternoon ahead of an approaching cold front. Continued
Small Craft Advisory due to marginal winds and seas. Will sea
the near water advisory end by late this morning, with southern
outer waters continuing into this evening as seas are 4-5 feet.

Increasing chances gale force winds could arrive as early as
Wednesday evening and lasting into the overnight hours.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Low risk for gale force winds with gusts up to
40 kt. Areas of rough seas. Slight chance of rain showers.

Thursday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 10 ft.

Thursday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Areas of rough seas.

Friday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Seas locally approaching 5 ft.

Friday Night: Winds less than 25 kt. Chance of rain.

Saturday: Low risk for gale force winds with gusts up to 30 kt.
Areas of rough seas. Rain likely.

&&

.FIRE WEATHER...

Today...

Minimum afternoon relative humidity values drop into the 25 to
35 percent range today, away from the higher terrain of western
Massachusetts and northwest Connecticut. Winds are west to
northwest gusting of 20 to 25 mph, a few gusts up to 30 mph are
anticipated by late morning/early afternoon.

In coordination with our fire weather partners, have held off
on issuing another SPS for elevated fire weather concerns.

Thursday...

Gusty WNW winds and rather dry airmass will lead to the potential of
elevated fire weather concerns again on Thursday. Minimum relative
humidity values of 20-40 percent are expected with gusts 30-50
mph.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for
     ANZ231>235-237-251.
     Small Craft Advisory until 2 PM EDT this afternoon for ANZ250.
     Small Craft Advisory until 8 AM EDT Wednesday for ANZ254>256.

&&

$$

SYNOPSIS...KJC/Dooley
NEAR TERM...Dooley
SHORT TERM...Dooley
LONG TERM...KJC
AVIATION...KJC/Dooley
MARINE...KJC/Dooley
FIRE WEATHER...KJC/Dooley

NWS BOX Office Area Forecast Discussion