BOX issues Area Forecast Discussion (AFD) at Jul 2, 2:07 AM EDT167
FXUS61 KBOX 020607
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
207 AM EDT Tue Jul 2 2024
.SYNOPSIS...
High pressure over New York moves southeastward into the southern
off waters through Wednesday. Expect full sun, seasonably warm
temperatures and low levels of humidity today and Wednesday. Cloud
cover increases Wednesday evening ahead of a weak cold front that
moves through Southern New England on the Independence Day holiday,
bringing a risk for showers and thunderstorms. Pop-up showers
possible on Friday, but a more unsettled weather pattern develops
for the weekend. Temperatures are generally seasonable to slightly
above normal, but with elevated humidity levels from Independence
Day into the weekend.
&&
.NEAR TERM /THROUGH TODAY/...
A sprawling, seasonably-strong 1024 mb high pressure cell was
located near Rochester NY early this morning, and ridging from it
was extending eastward into Southern New England. Tranquil
conditions with dewpoints falling thru the 50s for most. Some
patches of fog but these should be dissipating shortly after
sunrise.
Shaping up to be an outstanding early-July day for Southern New
England, as the aforementioned high pressure area ridges eastward.
Wall to wall sun today from the beaches to the Berkshires and points
in between today, with comfortable humidity levels. Should see
cirrus clouds start to overspread very late in the day but that's
about it. Modest northerly wind this morning subsides with
slackening pressure gradient, and winds by late morning into the
aftn become driven by mesoscale effects (terrain and
seabreezes). Highs in the low to mid 80s for most, with mid to
upper 70s near the coasts with anticipated seabreezes.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
High pressure expected to open tonight over eastern NY to
shift SE thru tonight into the southern offshore waters and
generally maintain that position through Wed. Thus continued
tranquil weather is expected both tonight and Wednesday,
although will see periods of high clouds spill into Southern New
England.
The question mark for tonight is on potential for patchy
radiation fog at least in the river valleys. We do get into a
modest southerly flow late tonight and that should bring
dewpoints up somewhat (into the mid/upper 50s). Models for
tonight seem pretty mixed on the potential and also is not really
hinted at in the MOS progs either, but it seems like one of
those nights where you could get at least river valley fog to
develop with good radiational cooling expected. MOS used for
lows in given radiational cooling, with lows in the 50s for
most, though the urban areas and hills could see readings near
60.
Modest southerly gradient expected for Wed, but think weak flow
aloft should again favor seabreezes on both coasts. More of a mix of
sun and high clouds for Wed, along with dewpoints rising to near 60
so humidity levels should be tolerable. Highs in the 80s, with late-
day highs on the eastern MA coast once seabreeze-driven winds shift
to the SW.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights:
* A couple showers are possible, along with increased humidity
on Independence Day.
* Warm, humid, and showers about for Friday and this coming weekend,
but timing remains uncertain.
Thursday and Friday:
Axis of the mid-level ridge is oriented from southwest to northeast
but is shifting offshore and deamplifying, allowing for a zonal
pattern. There is good agreement for Thursday a surface low pressure
system moves from west to east across Quebec and weak cold front
moving across New England. Overall weak forcing, thus do not expect
a washout, despite PWATs between 1.5 and 2.0 inches. Ensembles, like
DESI show less than a 10% probability for 0.25" of new rainfall for
Thursday afternoon, with a realistic/likelihood for a few hundredths
of an inch of new rainfall are between 40% and 50%. Timing remains
uncertain given no large scale forcing, but expect we will have a
better idea once the high-res models are able to capture the meso
scale features. As of 02/00z, NAM 3KM only goes out to 12z Thursday
or 8am on July 4th. Heading into Friday, there are subtle height
rises along with weak shortwave energy traversing through the zonal
mid-level regime. As PWATs remain well above normal, 1.5" to 1.8",
and even higher values along the southern coast nearing 2.25".
Again, fairly low probabilities for new rainfall, around 25%
probability of 0.1". Important to note, that localized heavier
downpours still cannot be ruled out a this point in time given how
moisture rich the atmosphere is.
And as you might imagine, with anomolously high PWATs, dew points
are elevated and will be the type of humidity you can feel. Both
Thursday and Friday air temperatures in the middle and upper 80s
with dew points in the upper 60s and low 70s. Overnight lows are in
the middle to upper 60s, with low 70s possible in urban centers.
Saturday and Sunday:
Unsettled pattern into the weekend ahead, while model guidance is in
a good amount of agreement on the mid-level pattern, there is a good
deal of uncertainty in the surface features. Right now, it appears a
warm front lifts across the region some time Saturday and cold front
passage on Sunday. The air mass is still quite warm and muggy this
coming weekend, but could change, especially for Sunday depending on
the timing of the front. For now, highs are generally middle to
upper 80s with the potential for oppressive humidity, as dew points
are in the low 70s.
Monday:
Mid-level high over Bermuda with a trough over the eastern third of
the CONUS. There is spread in the surface features amongst 02/00z
guidance and have very low confidence in this part of the forecast.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
06z TAF Update:
Today through Wednesday: High confidence.
VFR for all airports through the period. Winds today start light
northerly (4-8 kt), with seabreezes developing 15-17z on both
coasts. Winds then turn light southerly tonight and overnight,
which continue into Wednesday as well. Another period of
seabreezes expected on Wed on both coasts following a roughly
similar timeframe of onset and cessation.
KBOS TAF...High confidence in TAF. VFR thru the period. NW
winds around 4-8 kt to start ease and shift to seabreezes/ESEly
around 8-10 kt ~15-17z thru 23z-00z, then begin a clockwise
turn to NW for overnight. Another period of seabreezes for Wed.
KBDL TAF...High confidence in TAF. VFR thru the period. N winds
around 5-8 kt today, but shift to light southerly late today
which continue into Wed.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: VFR. Slight chance SHRA.
Independence Day: VFR. Breezy. Slight chance SHRA.
Thursday Night through Friday Night: VFR. Slight chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Generally pleasant marine weather conditions as broad high pressure
gradually builds into the waters by Wed. Northerly winds this
morning around 10-15 kt to steadily decrease this afternoon
(becoming ESE near the immediate eastern MA coast), then begin to
shift to light SW late in the overnight hrs. Light SSW winds for
Wed, with local ESE winds near the immediate shorelines for Wed.
Seas 3 ft or less all waters.
Outlook /Wednesday Night through Saturday/...
Wednesday Night: Winds less than 25 kt.
Independence Day through Saturday: Winds less than 25 kt.
Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Loconto/Dooley
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Dooley
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Jul 2, 2:07 AM EDT----------------
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