Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbgm 180925 
afdbgm

Area forecast discussion
National Weather Service Binghamton New York
425 am EST Sat Nov 18 2017

Synopsis...
high pressure will reside over the region this evening then
shift east of the area later tonight. A strong low pressure
system will track west and north of the area this weekend
bringing rain for Saturday and Saturday night followed by gusty
and colder conditions with lake effect snow by late Sunday.

&&

Near term /through tonight/...
400 am update...
main concern is for low pressure system bringing a variety of
weather this weekend, including gusty winds and eventual lake
effect snow Sunday into Monday. See short term portion of the
discussion for details on the winds and snow.

On the front end of the system, we will see rain develop today
and last through tonight. Temperatures as of 3 am widely range
from only 19 in Sidney, to 37 in Penn Yan. However, warm air
just above the surface is surging over the region. Temperatures
will quickly rise this morning as lead shortwave sweeps west-
southwest to east-northeast across the region. Thankfully, pace
of things upstream and now the trend in high resolution models,
is for the initial rain to arrive slightly later this morning
compared to prior thinking. Confidence is thus even higher now
that by the time it actually arrives, temperatures will get
above freezing. We will still have to monitor things closely
just in case near surface temperatures are slow to respond, but
expectations are that it will be all rain.

Temperatures will move up through the day for highs of lower to
mid 40s. Initial wave of rain will press through central twin
tiers to Finger Lakes, with even a bit of instability aloft to
the point that a rogue rumble of thunder cannot be ruled out.
However, the activity will be running into a good amount of dry
air in the low levels the further east it GOES. It may somewhat
break up or at least become significantly lighter as it moves
towards Catskills-Poconos. Then, as deepening surface low moves
roughly across Lake Erie late afternoon to western New York
this evening, stronger wave aloft will also sweep across the
area with deep moisture to produce our main areawide rainfall of
about a half to three quarters of an inch or so. When adding up
all of today through tonight, a few of our more orographic-
lift prone higher elevation spots could end up to nearly an inch
of rain, such as near Ricketts Glen PA as well as pockets of
the Catskills and northern Oneida County in New York.

Models have continued to trend not quite as deep with the low,
but it still gets into the 980s millibar range while tracking
from western to northern New York tonight. Cold front will sweep
across our area between midnight and dawn, probably with a
squally line of showers and gusty winds. Temperatures will still
be above freezing through the night, but the colder air will be
just entering the region first thing Sunday morning.



&&

Short term /Sunday through Monday/...
420 am update...
attention quickly turns to gusty winds areawide Sunday,
followed by accumulating lake effect snow in parts of central
New York late Sunday through Monday.

With models backing off somewhat on the intensity of the surface
low, magnitude of forecast wind gusts has also been tempered
down just a bit. It will still no doubt be a breezy day, with
deep mixing from steep low level lapse rates, strong cold air
advection, and a good pressure gradient. Peak gusts however may
end up being mostly in 35 to 45 mph range. A few power outages
cannot be ruled out, but overall the threat is not quite as
high as had been figured before.

Temperatures will quickly fall into 30s-lower 40s range as cold
air mass overtakes the region Sunday. The solid batch of rain
Saturday night, will transition to scattered rain showers
changing to snow showers on Sunday with shallow moisture. Snow
accumulations during the day Sunday will be nominal, with
moisture residing almost entirely below the dendritic growth
layer. However, secondary shot of cold air will arrive late
afternoon-evening, with deeper moisture extending into the
dendritic growth zone as 850mb temperatures also fall into the
minus 10-12 Dec c range. From early Sunday evening through
midday Monday, Lake effect snow still appears likely. 300 degree
boundary layer flow will guide main band across Onondaga-
Madison-Oneida counties and perhaps into northern Otsego at
times Sunday night, with blowing snow an issue as well. During
this period, snowfall rates may approach 1 to 2 inches per hour
for brief times. Snow and blowing snow will accumulate quickly
and cause potentially hazardous travel conditions late Sunday
night into Monday morning.

Winds will slowly back to the west Monday, and even southwest
into Monday afternoon. This will allow the lake band to shift
north of the thruway. As this occurs, slightly warmer air will
begin to move in from the west and will start to erode the lake
effect snow processes and lower the inversion heights. Snowfall
rates will also diminish into the afternoon, and eventually lift
completely to the north out of the area by the evening. Cloud
cover will mix out from south to north Monday night with quiet
weather and cool temperatures.

At this time, when adding up Sunday through Monday, average
snow amounts of 4 to 8 inches are figured for Onondaga-Madison-
Oneida counties, but of course with lake effect snow there could
be locally higher amounts if a band can remain stationary for
several hours. Several ripples in the flow, and tenuous lake-
to-lake connections, suggest that there will be a lot of
fluctuations in the placement of the bands. We are also figuring
on about 1 to 3 inches or so sneaking into central Cayuga,
northern Cortland, northern Chenango, and Otsego counties.
Perhaps closer to 4 inches in far northern portions of these
counties. Additionally, 2 to 3 inches may extend into Steuben
County courtesy of Lake Erie, especially the highest terrain of
western-southwestern Steuben.

&&

Long term /Monday night through Friday/...
3 am...progressive, energetic upper level flow continues to
dominate through the long range period. To start the period
Monday evening, some weak lake effect will continue to be
possible across the far north, mainly north of I-90 across
Oneida County, before ending by the overnight as the flow shifts
to SW with a warm advection pattern developing. This will occur
as high pressure remains to the south with a low tracking
eastward over far northern Ontario. This will lead to a
seasonably mild day Tuesday under mainly sunny skies with highs
in the upper 40s to low 50s. Beyond this time, forecast gets a
bit trickier as the next cold front and associated trough with
the aforementioned low pushes eastward across the area Tuesday
night into Wednesday. The GFS and Gem continue to indicate a
mainly dry frontal passage while the latest European model (ecmwf) has a deeper
trough that manages to tap into some moisture and develop a low
off the East Coast by Wednesday...potentially bringing some
precip into the area. At this point, not making any big changes
to the forecast so will follow close to 0z superblend and only
mention low chances for rain/snow showers Tuesday night into
Wednesday with temperatures being marginal...generally in the
30s to low 40s.

At this point the end of next week looks to be mainly dry with
seasonably cool temperatures before another system potentially
affects the area next weekend.

&&

Aviation /08z Saturday through Wednesday/...
VFR conditions will hold overnight and for the morning hours on
Saturday. Rain will move into the terminals Saturday morning,
but it will take a few hours before moisture thickens enough to
lower ceilings into MVFR territory. Expect this to generally
occur in the 16 to 20z time frame with visbys also likely going
to MVFR. By the evening, cigs are likely to lower to lower to
IFR at kbgm and potentially kavp by the end of the taf period.

Winds will be light and variable overnight into Saturday morning before
eventually increasing to S/southeast around 10 knots. Prior to this
time, expect low level wind shear to be an issue in the 11-14z
time frame as a strong low level jet moves in while surface
winds remain light.



Outlook...

Saturday night...widespread restrictions in rain showers mixing
with snow showers.

Sunday / Monday...variable ceiling restrictions with scattered
lake effect snow showers north, generally VFR south half. Winds
will also be quite strong and gusty Sunday.

Tuesday...generally VFR.

Tuesday night/Wednesday...restrictions possible in scattered
rain/snow showers.

&&

Bgm watches/warnings/advisories...
PA...none.
New York...none.

&&

$$
Synopsis...mdp

National Weather Service Glossary of Abbreviations