BOX issues Area Forecast Discussion (AFD) at Apr 23, 6:48 AM EDT660
FXUS61 KBOX 231048
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
648 AM EDT Wed Apr 23 2025
.SYNOPSIS...
Warm and dry today followed by a chilly night driven by radiational
cooling. Rather mild and dry conditions continue with high pressure
over New England to round out the end of the work week, though there
is a low chance of a passing shower late Thursday evening/night for
northern Massachusetts, majority of the region is dry. A system for
Saturday brings the next chance for widespread rainfall, though
exact details remain uncertainty. Drier conditions return late this
weekend into early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Key Messages...
* Seasonable day with lots of sun and light winds.
* Chillier night tonight outside of the urban centers.
Quiet, zonal flow in the mid levels today with high pressure
building at the surface will allow for a seasonable and quiet
weather day. Relatively light NW winds continue through the daytime
hours, 5-10 mph. These will become calm overnight as good
radiational cooling conditions allow the boundary layer to decouple.
So, light winds and clear skies will allow locations outside of the
typical urban corridors to cool into the upper 30s and low 40s.
&&
.SHORT TERM /THURSDAY/...
Short Term
Key Messages...
* Warmer on Thursday with quiet and dry weather, save for the chance
of a spot shower in NW MA in the evening.
A broad mid level ridge overhead together with surface high pressure
just offshore will prolong the quiet and dry weather through
Thursday. The only exception is for western and central MA which may
be in close enough proximity to a weak shortwave and moisture plume
to our north to support widely scattered showers Thursday evening.
Temperature-wise, we will warm a few degrees on Thursday as warm
advection in the low levels pushes 925 mb temps up a few degrees
closer to 12C which would result in highs in the upper 60s and mid
70s, cooler along the south coast.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Key Messages:
* Warm and mostly dry Friday, outside of a stray shower in northern
Massachusetts Thursday evening/night.
* The next chance for widespread rain comes in Saturday, but there
are uncertainties with the exact timing.
* Drier conditions Sunday into early next week.
The Big Picture: Nearly zonal flow at 500mb across the CONUS into
Friday, a 850mb shortwave may produce a couple of spotty showers
late Thursday evening into predawn Friday for those in far northern
Massachusetts. Otherwise, dry on Friday with surface high pressure
across New England. This feature moves northeast towards Nova Scotia
ahead of the only soaking chance of rain for this part of the
forecast, arriving Saturday. Behind the system, mid-level ridging,
surface high pressure builds in from the northwest with drier
conditions Sunday into Tuesday of next week.
Thursday Night to Friday Night: Weak shortwave rides the northern
edge of the 850mb high, with the greatest forcing displaced to the
north in northern New England. Cannot rule out a rouge shower for
areas in northern Massachusetts, mainly along and north of Route 2.
Will have mild overnight lows in the 50s. Otherwise, dry conditions
and increased cloud cover for Friday. Will be another warm day, as
850mb temperatures remain above normal +10C to +12C a quick look at
BUFKIT and GFS and NAM show mixing Friday afternoon to 850mb. Highs
Friday reach the mid-70s and for those in the CT River Valley may
reach near 80F. At the coast it will be cooler do to the onshore
wind/seabreeze given the time of year, and there the highs cooler in
the low-60s, perhaps upper 50s for the Islands and outer Cape Cod.
Increasing clouds, becoming cloudy overnight ahead of the incoming
system, will lead to a mild night in the 50s.
Saturday and Saturday Night: Broad northern stream mid-level trough
moves across the northeast and development of a low-pressure system
with a southerly LLJ. Will have anomolous PWATs advect into southern
New England, 1.3" to 1.5", which is ~3 standard deviation above
normal. There remains a uncertainty with respect to the exact timing
of the onset and end time the rain, as mentioned previously,
GFS is biased towards a more progressive outcome, continued to
lean towards the slower solution which would bring rain in from
west to east overnight with the steadiest through the day on
Saturday, even rumbles of thunder cannot be ruled out with
limited MUCAPE of a few hundred J/kg. A widespread soaking rain,
modest probabilities for rainfall amounts greater than 0.5"
across the region at 60 to 70 percent. Increase the potential
rainfall to 1.0" or greater will have probabilites between 30
and 40 percent. WPC does have a low chance of excessive
rainfall, placing all of southern New England under a marginal
outlook. Will want to check back with us if you have outdoor
plans for Saturday.
Sunday through Tuesday: Quiet weather to follow on Sunday, though it
will be cooler, but features drying conditions as mid-level ridging
and surface high pressure arrives. North-northeast flow Sunday lends
to a cooler afternoon, highs in the upper-50s to low-60s. The flow
becomes southwest Monday and Tuesday, bringing warmer temperatures
in the upper-60s to low-70s on Monday, then low and middle 70s on
Tuesday.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12Z TAF Update:
Today: High Confidence
VFR. West/northwest winds around 10 knots. About a 50/50 chance
for a sea-breeze at BOS, but likely would be after 18Z if it
develops.
Tonight: High Confidence
VFR. Light and variable winds.
Thursday: High Confidence.
VFR. Winds light and variable, becoming southerly 5-10 kts in
the afternoon.
KBOS TAF...High confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Thursday Night through Sunday/...
Thursday Night through Friday: VFR.
Friday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.
Saturday: Mainly MVFR, with local IFR possible. Breezy. SHRA
likely, isolated TSRA.
Saturday Night: VFR. Breezy. Chance SHRA.
Sunday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Thursday...
A cold front crosses the waters early this morning resulting in a
wind shift to the northwest. This will also help usher out any
remaining fog/low stratus over the south coastal waters. High
pressure builds in from the west today and will support calm
conditions over the coastal waters through at least Thursday.
Outlook /Thursday Night through Sunday/...
Thursday Night through Friday: Winds less than 25 kt.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers.
Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Rain showers likely,
isolated thunderstorms.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...BW/Dooley
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Dooley
AVIATION...BW/Dooley
MARINE...BW/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Apr 23, 6:48 AM EDT----------------
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