Scientific Forecaster Discussion
fxus61 kgyx 191759 aac
Area forecast discussion...updated
National Weather Service Gray ME
1259 PM EST Tue Nov 19 2019
low pressure will gradually move away from the region this
afternoon, but until then mixed precipitation will be likely
across the higher terrain of Maine and New Hampshire. Clouds
will remain over the forecast area tonight through Wednesday as
upper level low pressure moves across the forecast area. Some
snow showers or freezing drizzle will be possible in higher
terrain. A brief period of high pressure and fair weather
arrives Thursday before a strong cold front sweeps across the
region on Friday.
Near term /until 6 PM this evening/...
1 PM update: quick update to adjust pops...but also drop the
winter wx advisory on schedule as snowfall amounts this
afternoon do not justify extending this headline. However...some
slick spots on roads are possible...particularly over the higher
1043 am update: boosted near term temperatures a tad based on
late morning observations. Otherwise..only minor adjustments
necessary as band of rain and some snow continues to lift north.
Accumulations have generally been one inch or less over the
higher terrain of southwest New Hampshire...with similar amounts expected
further north given how quickly the back edge of the
precipitation shield is moving north.
849 am update: going forecast in good shape with minor
adjustments for near term temperatures and refining
precipitation area. Watching webcams over southwestern New Hampshire
showing snow levels lowering with some slick travel likely
before precipitation comes to an end from south to north.
635 am update...little change to the going forecast at this
hour. The next short wave trough and associated forcing for
ascent is on the Massachusetts/New Hampshire border as evidenced by the band of
moderate precipitation. A flip to snow is likely across a good
portion of southwestern New Hampshire over the next hour or two as the
ascent leads to cooling in the column. Snowfall forecast
haven't changed, basically looking at up to an inch on the
valley floors to 1-4 inches at higher elevations. Otherwise, a
mix of rain and snow is not out of the question across the rest
of southern/central New Hampshire as well as portions of the coastal plain
of ME this morning. Advisories remain in effect.
As one short wave trough moves into the Canadian Maritimes early
this morning, another short wave trough quickly approaches from
the southwest. This short wave is associated with the heavier
precipitation echoes located across upstate New York and southern New
England as of 08z.
This batch of precipitation will affect mostly our western and
southwestern New Hampshire zones this morning. Forcing for
ascent should be strong enough to cool the column to around
freezing across southwestern New Hampshire this morning, quite likely
Flipping any mixed precipitation to snow in the higher
elevations for a few hours. Have gone ahead and painted in an
area of 1-3" snowfall generally above 1000 ft in elevation this
morning, including the Monadnocks. Locally higher amounts are
possible above 2000 ft, including the White Mountains.
Cooling may be sufficient enough to allow to a brief flip to
snow on the valley floors as well, but little in the way of
accumulation is expected there. Further east, into eastern New Hampshire
and the coastal plain of Maine, the stronger forcing for ascent
associated with this short wave trough will remain to the west.
While a mix with snow or a little bit of sleet at times will be
possible this morning, accumulations are not expected at this
Otherwise, the winter weather advisories remain in place this
morning for lingering freezing rain at higher elevations. Still
seeing several mesonet readings between 30-32 degrees in the
advisory area as of 08z.
Improving conditions are expected this afternoon as the short
wave trough moves away.
Short term /6 PM this evening through 6 PM Wednesday/...
upper level low pressure and low level moisture lingers tonight
and Wednesday allowing for cloudy skies to continue. With the
low level moisture in place we cannot rule out some spotty light
freezing drizzle and snow showers at times, especially across
the higher terrain of New Hampshire both tonight and Wednesday.
Long term /Wednesday night through Monday/...
the final shortwave trof within the broader pattern will cross the
region Wed night. Model guidance still hinting at a favorable
set up for an inverted trof and lingering lower cloud cover
and/or some showers. Will continue with some chance to slight
chance pop mainly across New Hampshire and adjacent swrn ME to account for
Shortwave ridging will move in for much of Thu but as the description
suggests...it will be short-lived. A strong cold front will
cross the region Fri. While the bulk of the forcing will remain
to our north...800 mb temps will go from around +5 to -10c as the front
moves thru. This will certainly be enough change for some
showers along the front and gusty cold air advection winds behind it.
Perhaps more interesting will be the trailing srn end of the
front. As forcing weakens it will hang up to our S...while model
guidance forecasts an upper low to eject out of the swrn Continental U.S..
depending on where the boundary stalls this upper low has the
chance to track newd along it and bring another round of precip
to the forecast area. Given the fresh supply of cold air ahead
of this wave that could make for interesting ptype forecasts.
At this time deterministic guidance is suppressed and mostly out
to sea with precip. But that being said...ensemble guidance is
much more uncertain about that scenario...and much of that
uncertainty is tied to just how amplified the follow up wave
is. I want to keep at least some pop in the forecast despite the
19.00z suite coming in dry.
Aviation /18z Tuesday through Sunday/...
short term /through Wednesday night/...
Summary: a trough of low pressure will gradually depart the region
through tonight with ample low level moisture resulting in low
clouds and some fog. A mid level disturbance will bring some
light rain and snow showers on Wednesday before high pressure
begins to arrive from the west Wednesday night.
Restrictions: now through daybreak Wednesday will be dominated by
LIFR/IFR ceilings - visibilities with low clouds and some fog. Gradual
improvement is expected on Wednesday with IFR/MVFR the dominant
category...but occasional -shrasn and dz expected. More
substantial improvement is expected Wednesday night with a
return to VFR.
Winds: light winds /5kts or less/ will prevail through Wednesday
morning before strengthening from the northwest 10-15kts during the
day Wednesday...and continuing through Wednesday night.
Llws: no low level wind shear expected through Wednesday night.
Long term...lingering inverted trof and any MVFR cigs or local
IFR in shsn move out with shortwave ridging and VFR replacing it.
This will linger into Thu night before the next system
approaches. Fri looks like it is trending towards a strong cold
frontal passage...with rain showers/shsn and local IFR possible but
mostly MVFR. Some gusty winds possible behind the front as
colder air moves back into the region.
short term...scas continue for the waters today, and through
tonight on the outer waters as seas will take some time to come
down to 5 ft.
Long term...winds and seas will be gradually diminishing Wed
night...but I still expect some Small Craft Advisory conditions outside of the
bays to start the period. Shortwave ridging allows a small break in
hazardous conditions Thu...but a strong cold front crossing the
waters will bring a return to widespread scas. Gale force gusts
are possible outside of the bays behind this front.
seas will very slowly subside as we head into the next high
tide. However, some splashover possible around the time of this
afternoon's high tide but impact should be minimal. Some model
information is indicating that tides could be a bit higher
Wednesday afternoon, so we'll have to watch that one more for
splashover and erosion.
Marine...Small Craft Advisory until 4 am EST Wednesday for anz150-152-