BOX issues Area Forecast Discussion (AFD) at Nov 17, 12:12 PM EST306
FXUS61 KBOX 171712
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
1212 PM EST Sun Nov 17 2024
.SYNOPSIS...
Dry weather and above normal temperatures will continue into
Wednesday. A developing low pressure system to our west may
finally bring much needed widespread rainfall late Wednesday
night and Thursday. Unsettled weather pattern will prevail
Friday and Saturday with the chance of showers at times but not
a washout.
&&
.NEAR TERM /THROUGH TONIGHT/...
Wind gusts have already decreased from early this morning, as
expected. This will continue to be the case through the
afternoon with winds further diminishing as high pressure
approaches.
Previous Discussion...
A quiet start to Sunday with high pressure and mid-level
heights on the rise, satellite imagery shows clear skies across
all of southern New England... this trend continues through the
daylight hours of today. Temperatures early this morning are in
the upper 20s and 30s with the exception of Cape Cod and the
Islands, where morning lows are in the upper 30s and low 40s.
Lastly, there is likely to be minor coastal flooding during the
morning high tide cycle for locations in coastal eastern MA. For
further details please see the tides and coastal flooding
section of the AFD.
Mid-level ridging extends into New England this afternoon, not
only does it provide continued sunshine, 925mb temperatures
between +9C and +12C should provide a mild afternoon, despite
not mixing deeply this afternoon. Given the consistent pattern,
leaned on the BCCONSMOS data set to derive high temperatures
60F-65F. On the surface today is a great day, but given the
ongoing fire weather concerns today is not ideal as dew point
temperatures are largely in the upper teens and lower 20s, this
results in min RH values from the upper teens to the low 30s.
One positive note, gusts diminish throughout the day and do
think the stronger winds will occur earlier in the day when RH
values are slightly higher. Nevertheless, continued NW flow this
afternoon with 10 to 15 mph gusts. For further details please
see the fire weather section of the AFD.
&&
.SHORT TERM /MONDAY/...
The mid-level ridge shifts east of the region and a mid-level
low moves south of Hudson Bay, Canada towards the Gulf of Maine.
A weak front extends south and leads to areas of rain along the
front, but drier air advects into the front and leads to a dry
night for the vast majority of southern New England. While an
isolated area of VERY light rain could occur, in mainly far NW
MA, do not get excited, because, if a location would be
fortunate to be beneath an isolated shower, it is likely the
rain would not be measurable due to the significant amount of
dry air lingering beneath those cloud bases. At best a hundredth
or two of rain. At the very least there will be added cloud
cover, which keeps temperatures a little higher than the night
before, mainly in the middle to upper 30s and lower 40s for Cape
Cod and the Islands.
For Monday, the biggest concern revolves around fire weather as
southern New England is placed between the departing mid-level
low east of the Gulf of Maine and a ridge across the northern
Great Lakes. This set up will funnel northwest winds and with
modest mixing of the boundary layer, should be able to tap into
the stronger wind aloft, gusting 20 to 30 mph at the surface.
Some good news would be the min RH values do come up to 45 and
55 percent.
925mb temperatures are right around +4C and +7C, thus highs in
the mid to upper 50s are expected.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Key Points..
* Dry conditions with above normal temps Tue-Wed
* Widespread rain likely late Wed night into Thu evening but
amounts uncertain. Some snow possible in the Berkshires.
* Somewhat unsettled Fri-Sat with chance of showers at times
but not a washout
Monday night through Wednesday...
Upper low exits New Eng Mon night with ridging aloft building
into the region Tue and Wed. Dry weather with above normal temps
expected. Slight cooling at 925 mb Tue then moderating again
Wed. Expect highs in the 50s Tue and upper 50s to lower 60s Wed.
Surface ridge axis will be west of New Eng Tue with enough
gradient to allow for somewhat breezy conditions, then light
winds Wed as ridging moves overhead.
Wednesday night and Thursday night...
Global and ensemble guidance in agreement on anomalous upper
low digging into the Ohio Valley with strong height falls
developing over New Eng. There is still some uncertainty
regarding how the surface features play out which will determine
exact details. A low prob scenario with an intensifying low
pres south of New Eng would allow for rain flipping to
accumulating snow in the Berkshires Thu afternoon and evening.
Still a lot of uncertainty and while we can't completely
discount this scenario, it is a day 5 forecast and we followed
NBM solution for now. The latest deterministic GFS is obviously
an outlier and does not have support of its ensembles. Will have
to continue to monitor.
Developing low level jet and increased forcing acting on a
decent PWAT plume will likely bring a period of widespread
showers sometime late Wed night into Thursday. One factor going
against a significant rainfall is that duration of heavier
rainfall may be limited as guidance is indicating a relatively
narrow band of enhanced moisture rotating through SNE followed
by a dry slot. ECMWF and GEFS ensembles show moderate to high
probs (50-80%) of 0.50"+ and 20-50% probs of 1"+, with highest
probs in western New Eng. Preliminary forecast suggests rainfall
averaging 0.50 to 1.0 inch, with locally higher amounts in the
west which will help with the exceedingly dry conditions but
certainly not a drought buster.
Best forcing and moisture should be lifting to the north during
Thu night which should result in rain becoming more scattered,
but this will depend on whether a secondary low develops to the
south which would cause steadier rain to linger into Thu night,
with potential for snow showers in the Berkshires.
Friday and Saturday...
Upper low will gradually move into New Eng Fri and Sat.
Specific details are uncertain but cold pool aloft and residual
moisture will lead to an unsettled pattern Fri-Sat with chance
of rain showers at times, mixed with snow over higher elevations
but certainty not a washout, and there will likely be some
breaks of sunshine as well. Below normal temps expected Fri and
Sat.
&&
.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update...
High confidence through Monday night...
VFR through the period. Increasing high clouds late today and
tonight, then some low-mid level cloud cigs Monday morning. NW
gusts to 15-20 kt today, light NW to calm wind tonight, then NW
wind increasing to 10-20 kt Monday afternoon with a few higher
gusts. NW wind gusts diminish Monday night but remain breezy.
KBOS Terminal...High Confidence in TAF.
KBDL Terminal...High Confidence in TAF.
Outlook /Monday Night through Thursday/...
Monday Night through Tuesday: VFR. Breezy.
Tuesday Night through Wednesday: VFR.
Wednesday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA.
Thursday: Mainly MVFR, with areas IFR possible. Breezy. SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Monday...High confidence.
Seas continue to diminish, falling below advisory criteria this
evening. Northwest winds remain elevated through this morning
and ease into this afternoon.
Will maintain a Small Craft Advisory for marginal seas on the
outer most sections of the eastern zones through this afternoon,
with the exception of the southeast waters, from Provincetown
to Nantucket given 5 ft seas could linger there until midnight
or so.
Seas are between 2 and 4 ft Monday, increasing NW winds behind
a front may lead to a short-fused advisory for the waters south
of RI.
Outlook /Monday Night through Thursday/...
Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Tuesday Night through Wednesday: Winds less than 25 kt.
Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft. Chance of rain showers.
Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Rain showers likely.
&&
.FIRE WEATHER...
ELEVATED FIRE WEATHER CONCERNS SUNDAY FOR SOUTHERN NEW ENGLAND...
Conditions remain very dry today with min RH values lowering to
the upper teens and 20s in the afternoon. Areas NEAR Cape Cod
will have higher min RH values in the upper 30s to mid 50s. Less
wind expected with gusts to 10-15 mph this afternoon. Have
coordinated with our state fire weather partners and issued a
Special Weather Statement to highlight the fire danger today.
On Monday, there is improving min RH values, but do expect
stronger gusts between 20-30 mph. We will need to touch base
with our partners today and discuss what type of headline could
be needed.
&&
.TIDES/COASTAL FLOODING...
* Coastal Flood Statement for eastern MA coast; including Cape
Cod and Islands for this mornings high tide.
Astronomical tides have peaked just under 12' MLLW and are
slowly on the decline. Still, there will be minor coastal
flooding, which is best described as sporadic and nuisance
flooding, as the surge with this mornings high tide is close to
1 ft. A coastal flood statement is in effect for east coastal MA
for the late morning high tide..
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ250-
255.
Small Craft Advisory until 2 AM EST Monday for ANZ254.
&&
$$
SYNOPSIS...KJC/Dooley
NEAR TERM...BW/Dooley
SHORT TERM...Dooley
LONG TERM...KJC
AVIATION...BW/Dooley
MARINE...KJC/Dooley
FIRE WEATHER...KJC/Dooley
TIDES/COASTAL FLOODING...Dooley
Source:
BOX issues Area Forecast Discussion (AFD) at Nov 17, 12:12 PM EST----------------
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