BOX issues Area Forecast Discussion (AFD) at Dec 28, 6:27 PM EST652
FXUS61 KBOX 282327
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
627 PM EST Sat Dec 28 2024
.SYNOPSIS...
A warm front will remain near the South Coast tonight and
Sunday, resulting in areas of drizzle and dense fog. This front
will bring milder air into the region by Sunday night as it
lifts into northern New England, then a cold front will bring
showers with brief downpours Monday. Another low pressure
system should bring rain New Years Day. Then colder and drier
weather should follow into the first weekend of 2025.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
630 PM Update:
Tonight...
Key messages:
* Areas of dense fog and drizzle tonight.
Front remains draped near Cape Cod and should move little
tonight, or even drop back south of the Islands. Light winds and
a somewhat milder airmass over remaining snow pack/cold ground
will maintain areas of drizzle and dense fog. Setup isn't ideal
for widespread dense fog and the need for an Advisory, given
true milder air is expected to remain offshore through night.
Radar shows an area of showers lifting NE from NJ and Long
Island which will clip south coastal areas tonight as well.
Otherwise, forecast is on track with overnight lows in the mid
30s to around 40, just warm enough to prevent any icing
concerns, but something we'll watch if some interior spots
manage to drop closer to freezing toward daybreak.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
250 PM Update:
Key Messages:
* Periods of light rain and areas of fog
* Turning mild late in the day/night and breezy
Sunday...
Warm front begins its northward push into and through SNE, resulting
in periods of WAA rain in the morning and early afternoon, then
tapering off late in the day from south to north. Not expecting any
downpours, just periods of mainly light rain. Areas of fog, locally
dense in the morning. Given low pressure to our west doesn't reach
out latitude until late in the day or at night, true warm sector
airmass is probably delayed until then. Therefore, followed the
cooler guidance for temps Sunday, with highs in the 40s, but low 50s
possible across CT/RI and southeast MA given proximity to warm
sector.
Sunday night...
Very mild with warm sector overspreading the region. Low temps
likely be observed in the evening, then rising into the 50s toward
morning, as dew pts also rise into the 50s. Thus, it will feel mild.
Other than spotty light drizzle/rain in the evening, the main precip
will hold off until 09 - 12z Monday. This is when negative tilt
trough and accompanying low level jet and attending frontal boundary
approach from the west. Heavy, gusty showers will impact CT and
western-central MA beginning 4a-7a Monday, likely slowing down the
AM commute. These heavy showers likely hold off until after 7 AM for
RI and eastern MA. Stout low level southerly jet up to 60 kt toward
12z Mon moves across the south coast. Model soundings are inverted,
so not expecting full mixing. Nonetheless, southerly winds 15-20
with gusts up to 35 mph at times expected. Hence, becoming breezy
late Sunday night.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
250 PM update...
Key Messages:
* Mild through New Year's then temps back to normal by next weekend.
* Wet, windy, and warm Mon - potential for street flooding.
* More rain late New Year's Eve into New Year's Day - may end as
wet snow across higher elevations in western MA.
Theme of extended forecast remains unchanged: ridging off East Coast
combined with trough to our west maintains a mild pattern to close
out 2024, then we see a return to more normal temperatures by next
weekend as broad closed low takes up residence across southern
Canada.
Monday:
Looks to be the most active day of the week as potent upper trough
rotates through New England and drives a cold front through region.
Deep southerly flow will transport plenty of moisture northward into
SNE with precipitable water values climbing to over 1" but system
remains progressive which will reduce threat of excessive rainfall.
Ensemble probabilities favor amounts in 0.5 to 1.0" range but river
ensemble guidance does not indicate any potential for flooding,
despite recent change to a wetter pattern. Certainly may see the
usual poor drainage/street flooding for those commuting Mon morning.
Main concern in these types of setups is potential for convection
and damaging winds. 925mb winds increase to 60kt Mon but forecast
soundings are strongly inverted given warmth aloft so we would need
to see temperatures soar into mid 60s to be able to mix any of these
stronger winds fully to ground, which is pretty unlikely right now.
Highs in 50s to perhaps around 60 seem more likely which falls a
little short (but worth watching). We're also lacking significant
pressure falls as main low tracks well to our NW. Nonetheless,
it will be windy as momentum alone should be able to mix 50-60%
of these winds down.
Regarding convective potential, high res models show a fine line
ahead of cold front Mon morning, but it will probably fragment as it
enters a less favorable environment in SNE with a lack of low level
instability (if anything, it's more favorable well to our south).
However, this system does have a history of producing severe weather
near Gulf Coast so it's something to watch, though its upper support
should weaken somewhat as it runs up against that Atlantic ridge.
Certainly two things we will keep an eye on with later forecasts,
but right now they do not appear to be a major concern.
New Year's Eve (Tue) into New Year's Day (Wed):
We get a short break from the rain on Tuesday, and in fact, sunshine
will help temperatures reach well into 40s and 50s. Next low
pressure system brings rain back on New Year's Eve into New Year's
Day as it likely crosses through SNE. It's possible that we see a
brief changeover to wet snow behind system Wed afternoon/evening
across higher elevations in MA as colder air is drawn into region.
Thu into Next Weekend:
Dry and colder weather follows Thu into next weekend with colder
W/NW flow, but it's more like a return to more normal temperatures
with highs in 30s to around 40.
&&
.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update: Moderate confidence, mainly due to timing.
IFR/LIFR in drizzle and fog will become more widespread
overnight as front remains stalled near South Coast. Not
expecting much improvement Sun morning but visibilities should
improve slowly, with IFR ceilings hanging on for much of the
day. Ceilings may improve to MVFR Sun afternoon and evening as
warm front finally lifts north. Showers associated with
approaching cold front may reach western MA/CT toward daybreak
Mon.
LLWS expected to become an issue after 16z Sun and lasting
through Sun night with 2000 ft winds 20035-45kt.
KBOS TAF...Moderate confidence, especially with timing of
changes Sunday. Fairly confident visibility will stay aob 1/2SM
in fog tonight. LLWS after 16z Sunday with 2000 ft winds
22035-40kt.
KBDL TAF...Moderate confidence. Still think visibility will drop
to 3/4SM tonight and could go to 1/2SM but wasn't confidence
enough to include. LLWS after 18z Sunday with 2000 ft winds
22035-40kt.
Outlook /Monday through Thursday/...
Monday: MVFR/IFR conditions possible. Windy with local gusts up
to 30 kt. SHRA.
Monday Night: VFR. Breezy.
Tuesday: VFR.
Tuesday Night: Mainly VFR, with areas MVFR possible. Breezy.
RA.
New Years Day: MVFR/IFR conditions possible. Breezy. RA.
Wednesday Night: Mainly VFR, with local MVFR possible. Windy
with local gusts up to 30 kt. Chance RA, slight chance SN.
Thursday: VFR. Windy with gusts up to 30 kt.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
250 PM update...
High confidence through Sunday night.
Tonight...weak warm front remains south of New England, yielding
light south winds across the RI and MA waters. Patchy drizzle and
areas of dense fog will reduce vsby to less than a mile at times.
Sunday...warm front slowly moves into RI/MA waters from south to
north. Winds remain light from the south. Periods of rain with areas
of dense fog reducing vsby to less than a mile at times, especially
in the morning.
Sunday night...warm front lifts north into NH/ME waters, with
southerly winds increasing to 15-25 kt late. Drizzle in the evening
is replaced by heavy showers toward morning. Areas of fog will limit
vsby to 1-3 miles.
Outlook /Monday through Thursday/...
Monday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 10 ft. Rain showers.
Monday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.
Tuesday: Winds less than 25 kt. Local rough seas.
Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Chance of rain.
New Years Day: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Rough seas up to 9 ft. Rain likely.
Wednesday Night: Strong winds with gusts up to 35 kt. Rough
seas up to 10 ft. Chance of rain.
Thursday: Strong winds with gusts up to 35 kt. Rough seas up to
10 ft. Slight chance of rain.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from midnight Sunday night to 4 PM EST
Monday for ANZ230-231-250-251-254.
Small Craft Advisory from 9 PM Sunday to 1 PM EST Monday for
ANZ232>237-255-256.
&&
$$
SYNOPSIS...JWD/Nocera
NEAR TERM...JWD
SHORT TERM...Nocera
LONG TERM...JWD
AVIATION...JWD/Nocera
MARINE...JWD/Nocera
Source:
BOX issues Area Forecast Discussion (AFD) at Dec 28, 6:27 PM EST----------------
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