BOX issues Area Forecast Discussion (AFD) at Dec 17, 3:33 AM EST485
FXUS61 KBOX 170833
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
333 AM EST Tue Dec 17 2024
.SYNOPSIS...
Periods of rain overnight into early Tuesday morning, then drying
out the rest of the day and unseasonably mild. Dry weather prevails
into Wednesday afternoon, but a fast moving weather pattern likely
yields another period of rain late Wednesday into early Thursday,
and perhaps more precipitation again Friday into Saturday. This will
be followed by very cold and blustery weather this weekend into
early next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
3:30 AM update...
Widespread light and pockets of moderate rainfall early this
morning with the passage of a warm front. Early morning
temperatures are quickly climbing into the low-50s with a few
areas still holding onto the 30s --- mainly areas to the north
of Springfield, MA. Blend of high resolution guidance for the
hourly temperatures through this morning, which brings this area
of the CWA into the low-40s before sunrise. The warm front does
bring higher dewpoints which promotes areas of fog, not
expecting widespread dense fog, rather areas of lower visibility
between 1 to 3 miles with isolated areas of locally dense fog,
visibilities less than 1/4 mile.
Rain ending from west to east during the mid-morning, but the
outer Cape and Islands holds onto the rain as late as 11am to
noon.
Overall, the forecast remains in good shape with no wholesale
changes, see the prior discussion below.
Key Messages:
* Unseasonably mild and dry mid to late morning & afternoon
Tuesday...
Approaching warm front and attending modest low level southwest jet
is yielding periods of rain overnight into early Tuesday morning
across the entire region. Then ending west to east around daybreak,
but later in the morning across Cape Cod and Nantucket. Rainfall
amounts expected to range from 0.10 to 0.25 inches, with localized
amounts from 0.35 to 0.50 possible. Mid to late morning, strong
column drying with model PWATs crashing from 1.0-1.2 inches in the
early morning, to less than 0.4 inches in the afternoon. Noticeable
warm sector airmass over the area in the morning, with +8C at 925 mb
across the I-95 corridor, along with dew pts in the low 50s! Thus,
it will feel mild Tuesday morning. Strong column drying mentioned
above combined with gusty WSW wind 15-25 mph, should result in
partial clearing/sunshine in the afternoon. If this materializes,
highs around 60 are possible from eastern CT-RI into eastern MA.
However, if low clouds are slower to clear, expect highs in the mid
to upper 50s. Still unseasonably mild, as normal highs for mid
December are in the upper 30s to lower 40s.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
1 AM update...
Key Messages...
* Dry and remaining relatively mild Tue night and Wednesday
Tuesday night...
Short wave ridging provides dry weather. As high pressure advects
across SNE, good radiational cooling occurs towards morning.
Therefore, derived mins from the cooler MOS guidance.
Wednesday...
Short wave ridging & dry column lingers, providing dry weather for
the bulk of the daylight hours. However, progressive upper air
pattern results in clouds on the increase in the afternoon with rain
possible by sunset across CT into western-central MA. Still
relatively mild with SW flow/WAA warming 925 mb temps from to +2C to
+4C, which should support highs in the 40s to near 50 along the
south coast. Surface winds will be light from the SSW.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
1 AM update...
Key Messages:
* Another period of rain Wed evening/overnight, possibly wet snow
high terrain
* Dry and cooler Thursday
* Ocean storm passing offshore Fri/Sat?
* Unseasonably cold Sat night/Sun/Mon
Precipitation...
Fast moving upper air pattern yields another period of rain Wed
evening and overnight, possibly wet snow across the high terrain,
although low level temps are marginal. Given progressive pattern,
dry weather returns Thursday. Then building western ridge yields an
amplified downstream east coast trough Fri/Sat. However, given the
lack of high latitude blocking, this trough remains progressive with
surface wave tracking offshore. The ECMWF AIFS is slightly closer to
the coast with a glancing blow. Still far enough out in time that it
bears watching, in case short wave trough verifies a bit sharper,
backing the mid level flow and storm track closer to the coast.
However, this appears to be a low probability event. Thereafter, dry
weather is likely later Sat into Sun/Mon.
Temperatures...
Seasonably cool Thursday with sunshine returning, highs in the 40s
and a modest NNW breeze. Fairly pleasant for mid to late Dec. Cooler
and brisk Fri, with NE winds and increased cloud cover as long wave
trough and offshore low develops. Then on the backside of the
departing offshore low and amplifying mid/upper trough, strong CAA
overspreads SNE with much colder weather for the weekend into early
next week. The core of the cold air appears to settle over the
region Sunday, with highs only in the 20s, lows in the single digits
and wind chills possibly below zero Sunday morning across the high
terrain. These temperatures are 15-20 degs colder than normal!
&&
.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z update...
Thru 12z...high confidence on trends, some uncertainty on exact
timing.
Widespread IFR/LIFR in periods of rain and fog. SSE winds and
gusty along the coast, up to 30 kt at times.
After 12z...high confidence on trends, some uncertainty on exact
timing.
IFR/LIFR in rain and fog early, improves to VFR in the
afternoon, but may only improve to MVFR across southeast MA. SSW
winds 15-25 kt in the morning becoming WSW in the afternoon at
10-20 kt.
Tuesday night and Wednesday...high confidence on VFR, dry
weather and light/variable winds.
KBOS TAF...Moderate Confidence in TAF.
KBDL TAF... Moderate Confidence in TAF.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: Mainly MVFR, with areas IFR possible. Breezy.
RA.
Thursday: VFR. Breezy. Chance RA.
Thursday Night: VFR.
Friday: Mainly VFR, with local MVFR possible. Chance SN, chance
RA.
Friday Night: MVFR/IFR conditions possible. Breezy. Chance SN.
Saturday: Mainly VFR, with local MVFR possible. Breezy. Chance
SN.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
1 AM update...
Tuesday...high confidence. Warm front yields SSE winds 20-30 kt
early Tue morning. Then the front lifts north of the MA/RI
waters with winds becoming SW 15-25 kt later in the morning,
then WSW 15-20 kt in the afternoon. Rain and early morning fog
limits vsby to less than 1 miles at times, improving late
morning and likely to the horizon during mid to late afternoon.
Tuesday night and Wednesday...high confidence. Weak high
pressure provides tranquil marine weather, with light winds, dry
weather and good vsby.
Outlook /Wednesday Night through Saturday/...
* Arctic blast likely over the weekend
Wednesday Night: Winds less than 25 kt. Local rough seas. Rain.
Thursday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Rain likely.
Friday Night: Winds less than 25 kt. Seas up to 5 ft. Rain
likely, snow likely. Local visibility 1 to 3 nm.
Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of
snow, chance of rain. Areas of visibility 1 to 3 nm.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 AM EST this morning for ANZ230-
236.
Small Craft Advisory until 1 PM EST this afternoon for
ANZ231>235-237-251.
Small Craft Advisory until 7 PM EST this evening for ANZ250.
Small Craft Advisory until 1 AM EST Wednesday for ANZ254>256.
&&
$$
SYNOPSIS...Nocera
NEAR TERM...Dooley/Nocera
SHORT TERM...Nocera
LONG TERM...Nocera
AVIATION...Nocera
MARINE...Nocera
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 17, 3:33 AM EST----------------
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