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fxus61 kbgm 231217 
afdbgm

Area forecast discussion
National Weather Service Binghamton New York
717 am EST Wed Jan 23 2019

Synopsis...
a low pressure system lifting will bring a wintry mix to the
region today. Initial snow sleet and freezing rain with the warm
front this morning, gradually changes to rain during the
afternoon from west to east. However, after mainly rain tonight, a
cold front will change rain back to snow showers late Thursday.
Slick roads could result from these multiple precipitation types.

&&

Near term /until 6 PM this evening/...
610 am update...
Winter Weather Advisory was started an hour earlier for a set
of counties in twin tiers to Cortland-upper Susquehanna areas;
change from snow/sleet to freezing rain in these areas is
happening ahead of schedule. More of the area could also average
near a tenth of an inch ice instead of mainly below; and some
higher elevation locations could get between one-two tenths.

Previous discussion...
a Winter Weather Advisory remains in effect areawide, with
counties having different starting and ending times based on
expected evolution of icy wintry mix to rain scenario.

Arctic air mass has been in place the last few days, and it will
take awhile for the stable cold air in the low levels underneath
the inversion to scour out. However, that sharp inversion is
also providing a smooth surface for which to have a strong low
level jet out of the south-southwest, quickly surging warm air
and moisture across the region aloft. Two concerns with this;
one is that temperatures will be warm enough just a few thousand
feet off the ground, to result in freezing rain/sleet becoming
the primary precipitation types. Also, the very cold ground from
the Arctic air mass will be slower to respond than the air
temperatures. Known Road temperatures are only in the mid teens
to lower 20s at this hour. This will rise somewhat as the day
carries on, but not in time to prevent icing from occurring on
untreated roads even as air temperatures get a bit above
freezing.

Dewpoints remain very low early this morning, and thus
snow-to-sleet may occur first due to wetbulbing, especially
with the initial wave of precipitation - mostly virga at first -
in the northern zones. Eventually though, the entire area is
prone to getting at least a light glaze of ice today. For the
eastern southern tier-upper Susquehanna regions of New York and
points south including northeast PA-Catskills, this will
likely occur mostly after the morning commute. For the central
southern tier-Finger Lakes-New York thruway corridor however, the
first light snow-ice may include some of the commute even
though most will occur after. Temperatures rise through the
day, though as mentioned before, freezing rain may linger even
as the air gets above 32 degrees simply due to the very cold
ground. Ice amounts will range from a trace to a tenth of an
inch, with the higher elevations most prone to getting that
tenth. It may take until early evening for the ice threat to
finally wane in the higher terrain east of I-81. As for snow,
very little accumulation if any is expected; well under an inch
except northern Oneida County may get an inch or so. By 6 PM,
temperatures will be mostly mid 30s to near 40, and rising; but
Poconos-Catskills may still be close to freezing.

&&

Short term /6 PM this evening through 6 PM Thursday/...
405 am update...
main concerns are following details of rain changing back to
snow, especially thursday; also stream rises that could lead to
isolated ice jams in response to rain and window of melting
snow, especially the Poconos-Catskills part of our area.

It is not totally out of the question for pockets of the
Catskills to still be dealing with patchy ice this evening.
However, temperatures will continue to rise overnight, to the
point that our region will be in the upper 30s to upper 40s by
dawn Thursday. Moisture will continue to stream across the area,
as the system slows down awaiting a new wave of low pressure
along the incoming cold front. Also, right entrance region of
the upper jet will be right over US, causing forced ascent. When
adding today through tonight, total precipitation - mostly in
the form of rain - will range from several tenths of an inch to
nearly an inch, with heaviest amounts where orographic lift
enhances rainfall. This includes higher elevations of northeast
PA, to Catskills, as well as northern Oneida County.

With snowmelt from temperature surge, especially Poconos-
Catskills, in addition the rainfall; we could see pretty solid
rises in rivers and streams. We are not expecting flooding but
will have to keep a close eye on things, and ice jams are not
out the question where recent Arctic air has allowed to build
ice in smaller channels. That is, rising levels may lift and
break the ice, potentially allowing jamming to occur as it flows
downstream and comes across obstacles/sharp streambed turns.

Surface cold front will advance west to east across the area
Thursday, but jet support will continue aloft with precipitation
starting to take an anafront nature. That is, forced ascent will
cause precipitation for a ways behind the front instead of just
ahead of it. Rain will thus mix with and change to snow as the
cold air advects in and temperatures fall through the day. Brief
window of freezing rain and sleet is not totally out of the
question since the cold air near the ground will outpace it
aloft, scooping underneath. Overall though, we are expecting a
small coating to an inch or two of snow behind the rain,
especially in central New York. Northeast PA-Sullivan County New York
should at least see brief snow showers on the back edge of the
precipitation, but accumulations of up to a slushy inch will
probably be limited to the highest terrain of the northern
tier and Catskills. Precipitation will be primarily east of
Interstate 81 in the afternoon. By early evening, temperatures
should range from mid-upper 20s northwest, to lower 30s
southeast.

&&

Long term /Thursday night through Tuesday/...
130 am update...
long term period features seasonably cold air and a series of
weak disturbances zipping through the area, with lake effect
snow showers between.

Low passes well north of the area Friday with snow showers but
more importantly a fresh supply of Arctic air for the weekend.
Broad upper trough remains in place and allows a stronger system
and yet another cold front for Sunday, this reinforces the lake
effect into Monday. Milder air and yet another wave arrives for
Tuesday with more snow.

Made only minor adjustments to the temps and pop grids to the
latest guidance as the grids were in good shape. Previous
discussion continues below.

Previous discussion...
Saturday, lake effect winds down as a ridge of surface high
pressure moves into the mid Atlantic states. This will push the
low level winds off of Lake Ontario back to west-southwest. The band of les
will shift out of Oneida County. Temperatures will continue to
be below normal with highs in the teens for cny and around 20
for nepa and Sullivan County New York.

Saturday night through tuesday: in general, no significant
storms are expected during this period at this time. Just a
couple weak disturbances that will move through the area with
chances of snow showers.

Beginning with Saturday night, most of the area looks
dry with the exception being over cny where there will be a
chance of snow showers ahead of the first of the
aforementioned weak disturbances during this time period. Only
put low chance pops across cny for now as there is some model
disagreement. The European model (ecmwf) is much slower and therefore keeps the
entire area dry while the GFS and Canadian support a faster
system with snow showers approaching cny. This weak system will
continue to move eastward on Sunday and Sunday night, bringing
a more widespread chance of snow showers. Then a brief dry
period (looks like the first half of Monday right now), before
the next system approaches late in the day Monday. Therefore,
put chance pops for snow showers across the western half of the
area with much lower chances further east, where it may remain
dry all day. These snow shower chances continue Monday night and
into Tuesday, mainly because of uncertainty in the timing of
this system. Another factor to keep an eye on is the track of
this system. Model guidance is suggesting at this time that the
system may track west of the area over the Great Lakes. Should
this westward trend continue, rain may be able to mix in over
portions of the area, mainly east. For now kept p-type as just
snow, but this may need to be updated as we get closer.

In terms of temperatures, near normal highs for this time of the
year are expected Sunday-Tuesday, generally in the 20s to lower
30s. Single digits to lower teens for lows expected Saturday
night with generally teens to lower 20s Sunday and Monday
nights.

&&

Aviation /12z Wednesday through Sunday/...
messy system with multiple precipitation types and low level
wind shear this taf period. The New York terminals will experience
freezing rain and MVFR ceilings, changing to plain rain with
time this afternoon yet with ceilings further lowering into fuel
alternate required levels. Precipitation at kavp will be
primarily rain, starting this afternoon, also with lowering
ceilings. There is a small chance that kavp could begin with
brief freezing rain if rain starts prior to 18z. Rain will
continue, and ceilings will lower further, into this
evening/overnight. At all terminals, a strong south-southwest
low level jet of 35-40 knots will increase to 40-55 knots and
thus low level wind shear will be present today through most of tonight. Krme-
ksyr surface winds will be southeast around 10 knots or less,
except ksyr eventually veers more southerly 10-15 knots with
higher gusts later today into evening. Surface winds at
remainder of terminals generally south or south-southwest 10-15
knots with gusts into the 20s knots, except lighter at kavp.

Outlook...

Thursday...rain gradually changing back to snow on back side of
system; restrictions likely.

Thursday night through Saturday night...restrictions possible
in snow showers, especially the New York terminals.

Sunday...chance of snow and associated restrictions.

&&

Bgm watches/warnings/advisories...
PA...Winter Weather Advisory until 5 PM EST this afternoon for
paz038-039.
Winter Weather Advisory until 7 PM EST this evening for paz040-
043-044-047-048-072.
New York...Winter Weather Advisory until 5 PM EST this afternoon for
nyz044>046-055>057.
Winter Weather Advisory until 7 PM EST this evening for nyz062.
Winter Weather Advisory until 7 PM EST this evening for nyz009.
Winter Weather Advisory until 3 PM EST this afternoon for
nyz015>018-022>025-036-037.

&&

$$

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