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Nov 15/16 First Weenie Obs

RUNNAWAYICEBERG

By RUNNAWAYICEBERG,
in New England

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Baroclinic Zone

Baroclinic Zone

Posted
Posted
Quote 

000
FXUS61 KBOX 151942
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
242 PM EST Thu Nov 15 2018

.SYNOPSIS...

A high impact but short duration snowstorm is on tap for areas
away from the very immediate coast this evening. Precipitation
transitions to mainly ice and then rain overnight, except
perhaps portions of the high terrain in Massachusetts. Dry
weather with chilly temperatures move in Friday afternoon
through most of the weekend as high pressure builds across. A
weak low may bring patchy light rain and/or snow late Sunday
into Monday. Another shot of colder air moves in by the middle
of next week, though it should be mainly dry.

&&

.NEAR TERM /THROUGH TONIGHT/...

235 pm update...

* High impact/short duration snowstorm this evening for many
* Winter Storm Warnings posted for northwest of I-95

A high impact/short duration winter storm is on tap across much
of the region this evening. Potent closed mid level energy
across the Ohio Valley was inducing an 80+ knot winds at 700 mb.
The result has been for heavy snow to break out across portions
of the mid Atlantic States this afternoon.

1) Heavy Snow Away From The Very Immediate Coast This Evening:

This potent speed max/convergence zone at 700 mb will continue
to lift northward resulting in very strong frontogenetic
forcing this evening across southern New England. Heavy snow
should develop after 4 or 5 pm across our northern CT zones and
spread northeastward into northeast MA after 7 or 8 pm. Highest
impact expected in our CT zones...given the heavy snow with 1 to
2 inch per hour rates will impact a large portion of the
evening rush hour. The latter half of the evening rush hour will
likely be impacted in the Springfield...to Worcester to
Providence areas.

The biggest question with this forecast is how well this band of
strong frontogenesis will maintain itself as it lifts northeast.
Confidence is highest across our CT/RI and interior southeast MA
zones. Further north...the guidance is somewhat split on that
potent speed max at 700 mb. The RGEM/NAM maintain it across
northern MA...while the ECMWF/GFS tend to weaken it and shunt it
further east. Regardless...it will snow heavy across much of the
region for a time but this will impact accumulations. We still
feel that 4 to 7 inches of snow looks good for much of the
region. Given the short duration/high impact event and
considering some light icing will persist after the main
event...feel warnings are warranted for much of the region. Snow
amounts will likely be much lighter on the very immediate
coast. SST around 50 with an easterly wind will result in making
it difficult to get more than an inch in these locations before
a quick change to rain.

2) Warming Aloft/Mid Level Dry Air Late This Evening:

Much of the region appears cold enough for mainly snow through
02z or 03z. However...the very potent 700 mb southerly jet will
transport mid level warmth northward across the region. Ptype
should transition from snow to ice/rain from 02z through 06z
across southern New England. At the same time...mid level dry
air will be cutting off our snowgrowth. Regardless...it appears
that the damage will be done across the region but some lighter
rain/ice will linger. Ptype will mainly be rain across eastern
MA/RI...but some light sleet/freezing rain may persist for a
time across the interior.

It does appear that temperatures by daybreak Friday will be
above freezing for most of the region for the morning rush hour.
The exception will be some of the high terrain...especially
interior northern MA where some light sleet/freezing rain may
still result in slippery travel

3) Strong to Damaging Winds:

A strong easterly low level jet of 55 to 65 knots is expected
to develop at 925 mb during the overnight hours along with
impressive pressure falls. Low level lapse rates are fairly
steep along the coast. This will result in a period of easterly
wind gusts of 40 to 50 mph along the eastern MA coast and up to
60 mph across the Cape/Islands. High wind warnings have been
issued for the Cape/Islands with wind advisories along the
eastern MA coast. Will have to watch for some downed trees and
isolated to scattered power outages.

&&

.SHORT TERM /FRIDAY/...

Friday...

The surface low pressure system looks to track near the
southeast New England coast Friday morning. Its associated
closed 700 mb level will also track across the southeast portion
of our region. The result will be periods of rain through Friday
morning...before coming to an end by afternoon. However...colder
air wrapping in behind the system may allow for portions of
interior MA /especially the high terrain/ to transition back to
a period of snow. It is possible that some of these areas see an
additional 1 to 3 inches of snow in this region. However...for
the rest of the region temps should remain above freezing with
perhaps just some wet snow flakes mixing in at the end.

Precipitation petty much ends by Friday afternoon and we may
see some peeks of sun late in the day. Afternoon temps should be
in the 30s to the lower 40s with gusty northwest winds.

&&

 

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