311 
FXUS61 KBGM 180713
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
213 AM EST Mon Jan 18 2021

.SYNOPSIS...
Lake effect snow showers will continue across the region through
the first half of the week. Colder conditions are expected on
Wednesday as high pressure briefly builds in. A clipper system
will track to our north, bringing another round of light snow to
the region Thursday into Friday. 

&&

.NEAR TERM /THROUGH TUESDAY/...
200 AM Update... 

Broad cyclonic around the backside of the vertically- stacked 
low over the Gulf of Saint Lawrence continues to affect our 
region. A 260-270 degree flow at the base of the low-level 
trough has helped yield a west-east lake effect snow (LES) band 
downwind of Lake Erie. A Special Weather Statement was issued 
for the hilly terrain south of the western Mohawk Valley (S 
Cayuga, N Cortland, S Onondaga, S Madison, N Chenango, and 
Otsego Counties) where enhanced snowfall rates up to 1" per hour
are possible. Do not expect this band to move much through the 
rest of the overnight but it will gradually weaken by early 
morning once the deeper lift associated with a mid-level 
shortwave trough exits the region. Snowfall amounts of 1-3" are 
expected in this area through sunrise. 

The flow will veer slightly out of the W-NW after sunrise. This
will allow the LES band off Erie to change orientation and 
shift southward across the Southern Tier of NY during the
morning hours. A brief burst of heavier snow is possible but the
band should be transitory enough to limit snowfall accumulations
to an inch or less. Additional LES snow showers are possible
across the Twin Tiers region this afternoon but the instability-
shear balance favors more cellular LES activity during peak
heating this afternoon. The combination of disorganized LES
convection and temperatures rising into the mid 30s should limit
snow from accumulating much this afternoon except for the higher
terrain.

Hi-res CAMs indicate the potential for the Lake Erie band to
become more organized by this evening across the Central
Southern Tier of NY and perhaps the Finger Lakes as the flow
backs out of the west again and some deeper lift arrives with
the next shortwave trough. If this does happen, localized
snowfall amounts of 1-3" would be possible (still too uncertain
to know exactly where). 

Several more fast-moving disturbances aloft are expected to 
pass through the region late Monday night and Tuesday. The
steering flow looks to back slightly to W and eventually W-SW. 
This will shift the favorable LES areas downwind of Erie and 
Ontario farther north into the NYS Thruway corridor and Tug Hill
Plateau on Tuesday. 

&&

.SHORT TERM /TUESDAY TONIGHT THROUGH WEDNESDAY NIGHT/...
235 PM Update...

A surface front goes through late Tuesday then another 
Wednesday. Aloft a zonal flow becomes an upper trough over the 
northeast as a strong short wave drop southeast early Wednesday.
Starting late Tuesday a west to northwest low level flow will 
bring added lake moisture into and north of the NY Thruway. Cold
air aloft will provide instability. The highest snow amounts 
will be in the north again but for now amounts look like only a 
few inches every 6 hours. Wednesday night the low level flow 
goes southwest shifting any remaining snow north of the area. 

Turning much colder for Wednesday with readings only expected 
in the 20s. Lows Tuesday night around 20 falling into the teens 
for most and single digits Oneida to Delaware Counties Wednesday
night.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
230 PM Update...

Little change again. Nothing big this period. Cold enough for
mostly snow. Thursday to Friday widespread snow but mostly light
snow amounts. High pressure builds in Saturday and lasts 
through Sunday. Dry and colder Saturday night and Sunday.

315 AM Update... 

High pressure appears to sneak into the area early Wednesday night 
allowing the lake effect to briefly shut down across CNY. The 
pattern remains broadly zonal with minor upper waves and surface 
fronts crossing the area Thursday and Thursday night. Another round 
of light snow and flurries for much of the forecast area on Thursday 
will transition to west-east oriented lake effect snow bands into 
Friday. Flow becomes more northerly and drier heading into Saturday 
as high pressure builds over the western Great Lakes. Single band 
snows should morph into a multi-band scenario and generally weaken 
to flurries and upslope snow showers from the Finger Lakes into the 
Southern Tier. Medium range models generally agree that a strong 
high pressure area will finally build in for Sunday.

Temperatures rebound a little bit for Thursday and Friday with 
readings in the lower-mid 30s, then seasonally normal cold air 
returns next weekend.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Lake-effect snow (LES) continues to affect the CNY terminals 
overnight. Prevailing MVFR CIGs and VSBYs will continue as a 
result with localized IFR mainly tied to where the most 
organized part of the Lake Erie snow band will be situated 
(north of ITH and south of SYR-RME through about 11Z). 

This LES band is expected to drop southward into ITH between 
11-14Z and ELM/BGM between 13-17Z. Brief IFR restrictions likely
as the band passes through. Snow shower activity should be
relatively disorganized during the afternoon. Otherwise, MVFR 
CIGs (1500-2500 ft) will persist for most terminals during the 
day today. W-NW winds 5-10 kt with gusts 15-20 kt are forecast.

A Lake Erie snow band could become better organized this evening
as it targets the Central Southern Tier. Places like ITH, ELM,
and BGM have the best chance to be impacted by this band, which
would mean a brief period of MVFR/IFR conditions between 00-06Z
Tuesday. 

Outlook... 

Tuesday through Wednesday...Stratocu deck will persist across
the region but CIGs will be variable (ranging from 1500-4000 ft
AGL). Scattered lake-effect snow showers will continue during
this time, resulting in periods of MVFR (localized IFR) 
restrictions.

Thursday and Friday...Possible restrictions in scattered to
numerous snow showers at all terminals.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

$$
SYNOPSIS...JRK
NEAR TERM...JRK
SHORT TERM...TAC
LONG TERM...AJG/JAB/TAC
AVIATION...JRK