NWS Forecaster Discussion
BOX
Area Forecast Discussion National Weather Service Boston/Norton MA.
000
FXUS61 KBOX 231956
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
356 PM EDT Tue Apr 23 2019
.SYNOPSIS...
A cold front will bring a round of showers and maybe a rumble of
thunder tonight into Wednesday morning, followed by mainly dry
weather as another high pressure moves across. Thursday could
be the pick of the week with sunshine, light winds and mild
temperatures. Then we get into another stretch of alternating
wet and dry weather Friday into Tuesday, with near to slightly
above normal temperatures.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Clouds linger across eastern and central Mass into RI at 19Z as
seen on latest GOES-East Visible satellite imagery and
observations. Leftover patchy fog lingers across portions of
Cape Cod, but should dissipate over the next hour or two. With
the cloud cover and cool, onshore wind, noting quite a temp
gradient from E to W, with readings in the 50s across eastern
areas, ranging to around 70 across the CT valley with light
winds.
Expect the high pres ridge to shift steadily E across the
region, reaching the coast by around 00Z. Winds should shift to
S-SE but will be light.
Low pressure will push across southern Ontario and Quebec
tonight, with trailing cold front crossing the region through
the night in the fast northern stream steering flow in place.
12Z models signaled some decent instability with this low, with
TT in the lower 50s, TQ values in the upper teens and the K
indices in the lower 30s. Already noting some CG lightning
across W PA with this front, so have mentioned isolated thunder
in the forecast as the system moves through. May also see some
locally brief downpours mainly across western areas, upwards to
0.25 inches as the moisture plume shifts NE.
The front should clear western areas by around 06Z or so, then
push to east coastal areas by around 12Z. Winds will shift to W
and begin to increase a bit toward daybreak across the west.
Temps will remain on the mild side, only bottoming out in the
40s to around 50.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The cold front will clear the eastern waters Wed morning, with
winds shifting to W-NW. Will see gusts up to 20-25 kt mainly
across the higher terrain during Wed. Otherwise, dry conditions
but cool temperatures will move in. Highs on Wed will range from
around 50 across the E slopes of the Berkshires to the mid 60s
across the southern coastal plain.
Winds will diminish Wed evening as the pressure gradient
relaxes Wed night. Colder air continues to filter in under
partly cloudy skies. Lows will be in the upper 30s well inland
ranging to the mid 40s along the coast.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Highlights...
* Dry Thursday with above normal temperatures
* Active pattern with alternating periods of wet and dry weather
Friday through Tuesday
* Near to above normal temperatures Friday through Tuesday
Discussion...
Southern New England gets stuck right within a transition zone
as several shortwaves move past our region. As each wave moves
by, the path of the mid level flow gets altered, but the overall
average position looks to be right overhead. This will mean
alternating periods of wet and dry weather as each mid level
shortwave and accompanying surface low pressure impacts our
region.
Lots of differences in the timing of these various waves,
especially after Sunday. Have the lowest confidence in the
specifics after that point in time. That said, the most likely
periods of wet weather look to be late Thursday night into
Friday evening, then again late Saturday night into Sunday
evening, then Monday evening into Tuesday.
High pressure off to our east will mean well above normal
temperatures Thursday. Temperatures look to be near to slightly
above normal Friday through Tuesday.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...Moderate confidence.
Through 00Z...
Mainly VFR VSBYS, but MVFR-IFR CIGS linger across
eastern/central Mass terminals into portions of RI. These
should to VFR briefly by around 00Z.
Tonight...
Generally MVFR CIGS across N central terminals and IFR-LIFR CIGS
across E coastal areas. -SHRA move across with local MVFR VSBYS,
with patchy fog and IFR VSBYS along the coast. Conditions
improve after 06Z across CT valley, but continue through the
night further E.
Wednesday and Wednesday night...
Leftover MVFR-IFR conditions across eastern Mass into RI early
Wed, then improve to VFR. W-NW wind gust to 20-25 kt through
midday Wed then should diminish. Expect VFR conditions to
continue through Wed night as high pressure builds across.
KBOS Terminal...
MVFR CIGS/VFR VSBYS this afternoon. CIGS will briefly improve to
VFR, then lower again to MVFR-IFR tonight. SCT -SHRA will move
across, along with low risk for brief thunder overnight. VSBYS
improve to VFR early Wed morning, but MVFR-IFR CIGS linger into
midday before becoming VFR.
KBDL Terminal...
Mainly VFR, but may briefly lower to MVFR around 03Z-06Z in
-SHRA. Winds shift to W by daybreak Wed.
Outlook /Thursday through Sunday/...
Thursday: VFR.
Thursday Night: VFR. Chance SHRA.
Friday: Mainly MVFR, with local IFR possible. Breezy. SHRA.
Friday Night: Mainly VFR, with local MVFR possible. Breezy.
SHRA likely.
Saturday: VFR. Breezy.
Saturday Night: VFR. Breezy. Slight chance SHRA.
Sunday: VFR. Breezy. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Wednesday Night/...High confidence.
Small Craft headlines remain in effect across the eastern open
waters as well as Mass/Ipswich Bays for seas at or above 5 ft.
Some gusts up to 25 kt are also possible into this evening for
the eastern outer waters.
S-SW winds will shift to W as the cold front moves across
overnight into early Wed morning. Winds will gust up to 25 kt
on the outer waters early Wednesday, but seas up to 5 ft will
linger into Wed night.
Outlook /Thursday through Sunday/...
Thursday: Winds less than 25 kt.
Thursday Night: Winds less than 25 kt. Chance of rain showers.
Friday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Rain showers likely.
Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Rain showers likely.
Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Sunday: Winds less than 25 kt. Local rough seas. Chance of rain
showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until noon EDT Wednesday for ANZ250.
Small Craft Advisory until 10 PM EDT this evening for ANZ251.
Small Craft Advisory until 6 AM EDT Thursday for ANZ254-255.
&&
$$
SYNOPSIS...Belk/EVT
NEAR TERM...EVT
SHORT TERM...EVT
LONG TERM...Belk
AVIATION...Belk/EVT
MARINE...Belk/EVT