Scientific Forecaster Discussion
fxus61 kbgm 231530
Area forecast discussion
National Weather Service Binghamton New York
1030 am EST Thu Nov 23 2017
partly sunny skies and cool temperatures are expected on
Thanksgiving. On Friday, high pressure in the mid Atlantic
region will produce a southwest flow of milder air along with
mostly sunny skies. A cold front will cross the area on Saturday
bringing scattered rain showers. Following the front Saturday
night into Sunday colder air will produce scattered snow showers
and some steadier lake effect snow showers primarily southeast
of Lake Ontario.
Near term /through Friday/...
10 am update... steady as she GOES with the forecast. Just minor
tweaks made to temperature and sky cover grids, based on the
latest observational data.
Satellite imagery shows a gradual erosion of the lower cloud
deck late this morning, as Our Lake Ontario moisture source gets
cut off via backing low-level flow (going from NW-sw).
Additionally, the thin remaining moist layer (as shown nicely by
the 12z Buffalo sounding) should simply get mixed out over
time. However, given the approach of an upper-level short-wave
from the Ohio Valley this afternoon, we'll still see some mid
and high-level cloud debris at times, albeit thinner in nature.
Overall, partly sunny seems like a good sky descriptor for the
rest of the daylight hours.
Afternoon highs were nudged downward just slightly based on
temperature trends the last few hours. We're still looking at
maximum readings mostly in the 30s this afternoon.
Enjoy the Holiday!
Previous discussion... early this morning satellite shows
mostly cloudy skies over much of the area as low level moisture
remains trapped under an inversion. Scattered flurries are also
occurring over the northern forecast area due to a cool west to
northwest flow. By sunrise flow will become southwest as surface
ridging builds in from the Ohio Valley. This will put an end to
any remaining flurries with skies expected to become partly
sunny. Highs will range in the middle 30s to around 40. A good
weather day for the Holiday.
Tonight...in general a dry period with the exception of
northern Oneida County. Here a surface trough moving through
eastern Canada and favorable flow for some lake enhancement may
produce scattered snow showers with any accumulation an inch or
less. Overnight lows will range in the middle to upper 20s with
readings in the lake plain around 30.
Friday...high pressure off Delmarva will keep a mild southwest
flow across the region along with mostly sunny skies. High
temperatures will range in the middle 40s to around 50 in the
warmer valley areas.
Short term /Friday night through Sunday/...
for Friday night, a strong southwest dry low-level flow dominates
our region to begin Friday night as an upper level short wave trough
axis moves into the Great Lakes region. This trough and associated
surface front reaches the eastern Great Lakes region to eastern Ohio
Valley by 12z Saturday. The 00z GFS and 00z CMC bring some light
showers ahead of this front into central New York between 06z and 12z
Saturday. The 00z Euro and 00z NAM keep most if not all of the quantitative precipitation forecast
west of our forecast area before 12z Saturday. So for now, have
chance pops for rain showers reaching the southern Tug Hill plateau
to Syracuse and northern Finger Lakes region with a ribbon of slight
chance for showers just to the south by 12z Saturday. It should
remain dry Friday night across most of the southern tier of NY,
Catskills and northeast PA.
Then Saturday morning, the front slows down as per the 00z NAM with
the front continuing a little farther east as per the Euro/GFS and
CMC. So given this spread we went from likely pops in our northwest
zones to chance pops and down to slight chance in our far southeast
zones in northeast PA Saturday morning. Cold air advection will
begin but it will be too warm for snow during the day Saturday. By
Saturday afternoon, the front continues east with the precipitation
drying out so have mainly chance pops for light showers.
Then for Saturday night into Sunday, a northwest flow of colder air
works in with lake effect snows and flurries downwind of Lake
Ontario. The flow begins around 290 degrees Saturday night with 850
mb temperature dropping to around -6c to -9c or so with the GFS and
NAM warmer with the inversion lower below the maximum ice Crystal
growth regime, the CMC and Euro are colder with a higher inversion
layer. This continues into Sunday with the Euro/CMC suggesting a 2-4
inch snowfall or a bit more southeast of Lake Ontario. But the NAM
and GFS suggests 1-3 inches at best. Model trends continue to be
warmer each run so we leaned more to the GFS/NAM solution. If this
trend continues, there won't be much lake effect snows at all. Right
our storm total snowfall grid has 1-3 inches southeast of Lake
Ontario Saturday night / Sunday. Rest of forecast area sees
scattered snow showers or flurries with less than 1 inch
Long term /Sunday night through Wednesday/...
for Sunday night and Monday, the Euro / CMC, there will be some warm
air advection with some lake moisture leading to some light snow
showers and flurries in north central New York. Dry weather expected in
south central New York / northeast PA.
For Monday night and Tuesday, a ridge of high pressure and then a
southwest flow of milder air sets up with dry weather. Then for
Wednesday some milder air and a chance for rain showers will
predominate as per superblend. The models diverge a lot by day 6-7
so there is a lot of uncertainty.
Aviation /16z Thursday through Monday/...
moisture trapped under an inversion along with a cool westerly
flow will keep some terminals in the MVFR category through 14z
then a developing southwest flow will improve conditions at all
terminals to VFR. VFR conditions are then expected to continue
West/northwest winds 5-10 knots shifting to the southwest later
this morning at 5-8 knots and continuing overnight.
Friday through Friday night...VFR.
Saturday...possible restrictions in rain showers.
Saturday night through Monday...Lake effect snow showers
causing restrictions, especially for ksyr-krme.