Scientific Forecaster Discussion
fxus61 kaly 082105
Area forecast discussion
National Weather Service Albany New York
405 PM EST sun Dec 8 2019
a light wintry mix will impact the southern Adirondacks
tonight, as clouds thicken and lower for the rest of the region, as
a low pressure system approaches from the mid Atlantic region. The
low pressure system and a frontal boundary will bring mainly rain to
the forecast area tomorrow into Tuesday with milder temperatures and
breezy conditions. Colder air moves back into the region with a
period of snow possible from the capital district and Berkshires
south and east late Tuesday night into Wednesday.
Near term /until 6 am Monday morning/...
..Winter Weather Advisory 11 PM EST to 8 am EST for the
As of 400 PM EST...high pressure continues to move well east of
New England tonight, as broad southwesterly flow will occur in
the low to mid levels associated with the mid and upper level
trough centered over the northern and Central Plains. A series
of short-waves embedded in the southwest flow will impact the
region. One disturbance ahead of a cold front over the northern
and central Great Lakes region will focus a light wintry mix for
the southern Adirondacks. A combination of the isentropic lift
and orographic enhancement off the southwest Adirondacks will
generate some light sleet and freezing rain, as temps will
likely bottom out early this evening, and then slowly rise. The
temps in the Hudson River valley may not fall much due to a
strong low-level jet and the funneling effect due to the
retreating sfc anticyclone and the front to the west.
Also, a southern stream disturbance will be lifting northeast
from the Carolinas. This wave of low pressure forming will
enhance the isentropic lift for some light rain or showers to
move in late south and east of the I-90 corridor. The capital
region may stay mainly dry tonight with breezy conditions. Lows
will be early on in the 20s to lower 30s, and then rise
overnight. Clouds will be thickening and lowering. Some of the
winds gusts this evening could get to 20-35 mph especially over
the confluent region of the capital region and into the upper
Hudson River valley.
Short term /6 am Monday morning through Tuesday night/...
tomorrow...any spotty freezing rain or drizzle should transition
to plain rain over the southern and eastern Adirondacks,as temps
rise above freezing. The temps should rise east of the southern
greens, but if they do not, then an Special Weather Statement for spotty freezing rain
or a west-southwest maybe needed. We leaned toward a superblend and warmer
temps with the strengthening south to southwest flow.
The low-level jet increases with the latest 12z gefs indicating
+v-wind anomalies /southerlies/ of 1 to 3 Standard devs above normal
with precipitable waters increasing to +1 to +3 Standard devs above normal. The
sfc wave will be lifting northeast for periods of rain. It
should be noted the h850 moisture flux anomalies will be in the
+3 to +4 Standard devs above normal, so some moderate bursts of rain
are likely especially south and east of the capital district.
The southwest flow aloft will tend to shunt the pcpn over the
capital region due to shadowing off the Catskills. Temps will
be rising to the 40s with some spotty 50s over the Mid Hudson
valley and perhaps near Bennington, Vermont. The snowpack will begin
to ripen and absorb the initial surge of rainfall.
Monday night...temps continue to rise and steady in the lower
40s to lower 50s. The surface dew points are likely to rise
into the upper 30s to mid 40s, which means the combination of
temperatures and dew points could lead to enhanced snow melt,
along with the locally moderate to heavy rainfall and patchy
fog. Some of the guidance shows a lull in the pcpn after 06z
with the wave moving east of New England. The cold front will be
approaching from western and northern New York by daybreak on Tuesday.
Tuesday...the cold front slides across the region with one more
surge of rain or showers. There is a strong thermal gradient
for a transition to some snow over the southern Adirondacks in
the afternoon. Max temps will be in the late morning and early
PM, but then temps will fall due to the strong cold advection.
Max temps will be in the 40s to mid 50s and then fall in the PM.
Some light snow accums are possible in the southern Adirondacks.
Total quantitative precipitation forecast before night fall may be in the about half an inch to
local amounts of 2.0 inches. See the Hydro section for the super
Tue night...the cold front slows and acts like an Ana front
with moisture pooling northward behind the sfc front and wind
shifts axis. Temps will be dropping quickly in the 20s to lower
30s with teens in the southern Adirondacks. The low and mid
level fgen increases with a weak wave ejecting northeast from
the Delmarva. Periods of light to moderate snow may break out
from the eastern Catskills/capital region and the Berkshires
south. We may need advisories for the southern
Taconics/Berkshires/NW CT and it could be a sloppy morning
commute from the Tri Cities south and east. Lows in the teens
and 20s with wet snow accums of 1 to 3" (highest totals in northwest
CT and the southern Taconics/ prior to daybreak from aly south
and east. See the long term for more details.
Long term /Wednesday through Sunday/...
intrusion of Arctic air with below normal temperatures will dominate
the beginning of the long term forecast, followed by some moderation
in temps, along with the next prospects for precipitation associated
with a possible coastal storm by next weekend.
A wave of low pressure developing along a frontal boundary to our
south and east should allow precipitation to linger across southeast
areas Wednesday morning. Forecast thermal profiles suggest p-type
should be snow. The question is how much precipitation occurs from
mid level forcing and moisture, as some southern stream energy
translates northeastward. Latest 12z/08 deterministic and ensemble
model guidance suggests the possibility of at least a few additional
inches of snow across portions of the Mid Hudson valley northeast
into northwest CT, the southern Berkshires, and southern Taconics, although
can not rule out precipitation lingering farther north in the
morning, which could allow some snow closer to the capital region of
New York into the northern Berkshires. Stratiform precipitation should
taper off by afternoon, however Arctic front and main upper level
trough passage should promote snow showers and perhaps embedded
squalls for the afternoon/evening hours, especially for the Mohawk
Valley northward. High temps mainly in the mid 20s to mid 30s, with
temperatures possibly falling during the afternoon hours.
Snow showers should transition to more of a lake effect/enhanced
event Wednesday night through Thursday morning, initially favoring
the southwest Adirondacks and western Mohawk Valley, before shifting
southward and becoming more multi-banded during Thursday morning,
with areal coverage likely decreasing in the afternoon as a
subsidence inversion lowers with high pressure building closer.
Otherwise, quite blustery with Wed night lows in the single digits
and teens, and highs Thursday mainly in the teens and 20s, although
could approach the lower 30s in the Mid Hudson valley. Wind chills
look to drop to zero to 10 below across northern areas, and zero to
10 above elsewhere Wednesday night.
High pressure should bring fair but cold conditions for Thursday
night into Friday night, with lows Thursday night dropping into the
single digits above and below zero across northern areas, and teens
elsewhere, with some potential for pockets of temps dipping to -10 f
or lower across the southern Adirondacks, depending on cloud cover
and wind. Highs Friday mid 20s to lower 30s.
Lots of uncertainty regarding next possible storm system for late
Friday night into next Sunday, with most likely period of
precipitation next Saturday. Siding closer to 12z/ec for onset
timing based on past performance. Thermal profiles look relatively
warm aloft, so this could be a rain/ice (rain/freezing rain)
situation, depending on how much shallow low level cold air remains
across the region. Will have to watch trends through the week. Lows
Friday night and Saturday night in the mid 20s to low 30s, although
may be warmer depending on ultimate storm track, with high
temperatures in the mid 30s to lower 40s.
Aviation /21z Sunday through Friday/...
VFR conditions expected through 03z/09 at all taf sites although
high clouds will be increasing. Ceilings start dropping towards 5kft
after 03z/09 and then should trend downwards towards by 06-09z/09. A
few showers are possible after 06z/09 but addressed this with vcsh
as coverage and intensity should be low. However, vsibilities are
expected to become MVFR due to fog development. By 12z/09, both
ceilings and visibilities could drop to IFR status, especially at
psf and gfl, tomorrow morning due to thickening fog. For now, only
Show Low MVFR ceilings and visibilities by 12z/09 but future updates
may trend lower. Showers become more widespread mid - late
morning tomorrow and should fog develop, it could stick around
through at least 18z/09.
Southerly winds become breezy this afternoon ranging from 8-15kts
and become southeast tonight and stay breezy. Southerly winds
decrease towards 12z/09 becoming near or less than 5kts. Low-
level wind shear should also develop at psf and pou.
Monday night: high operational impact. Breezy definite rain...fg.
Tuesday: moderate operational impact. Likely rain showers.
Tuesday night: high operational impact. Likely rain showers...shsn...sn.
Wednesday: moderate operational impact. Chance of shsn.
Wednesday night: moderate operational impact. Scattered shsn.
Thursday: low operational impact. Isolated shsn.
Thursday night: no operational impact. No sig weather.
Friday: low operational impact. No sig weather.
temperatures will remain below normal tonight into early
tomorrow, so little melting and/or runoff is expected on the
weekend. This will allow the snow pack to be maintained and
unripened. Temperatures will likely rise to above normal
values tomorrow and continue into Tuesday, with periods of rain
likely. There is increasing confidence that temperatures and
dewpoints will rise into the mid 30s to lower to mid 40s late
Monday afternoon through Tuesday morning, especially along and
south of the Mohawk Valley to southern Vermont. Those temperatures
and dew points along with locally heavy rain could enhance snow
There is uncertainty with the amount and placement of the
heaviest rain, however our current forecast is for about a half
an inch to about two inches in the hsa with the highest totals
in the southeast extreme over the Housatonic basin in northwest CT, the
southern greens, and also in the west/southwest Adirondacks.
Mmefs guidance varies with the naefs and gefs suggesting some
rivers reach action stage and perhaps and isolated Stem nicking
minor flood stage and the sref suggesting some rivers reaching
minor flood stage. Uncertainty in the amount of snow melt and
where the heaviest rain will fall is why there is such a variety
of solutions in the sources of guidance.
The bottom line, none of the nerfc forecasts are projecting
flooding at this time. Some ripening and melting of the snowpack
and runoff is expected, although widespread flooding is not
anticipated at this time. Rises on area waterways are likely
during this timeframe.
It will turn sharply colder Tuesday into Wednesday and continue through
the end of the week, which should put a stop to any melting/runoff,
and allow river levels to recede. Light to moderate snow amounts
are possible Tue night into Wednesday from the capital region
south and east in northwest CT and the Mid Hudson valley.
For details on specific area rivers and lakes, including latest
observed and forecast river stages and lake elevations, please visit
the advanced hydrologic prediction service /ahps/ graphs on our
New York...Winter Weather Advisory from 11 PM this evening to 8 am EST
Monday for nyz032-033-042-082.