305 
fxus61 kbgm 210809 
afdbgm 


Area forecast discussion 
National Weather Service Binghamton New York 
309 am EST Friday Nov 21 2008 


Synopsis... 
a widespread significant lake effect snow storm will affect much 
of upstate New York, and portions of far northern Pennsylvania, 
through today and into the weekend. 


&& 


Near term /until 6 PM this evening/... 
models in good agreement regarding low level wind flow off of 
Ontario today. It appears from the 300-310 flow snow will begin in 
earnest over Onondaga and Madison counties late this morning, and 
could become quite intense during the afternoon. This is in 
response to steepening lapse rates and a rising el layer. Snowfall 
rates in excess of an inch per hour will affect this region during 
peak afternoon commute times. 


&& 


Short term /6 PM this evening through Sunday night/... 
difficult to pin down exactly where the warning and advisory 
accumulations will fall at this juncture. Based on 300-310 flow 
shifting toward 320-330 flow overnight, it looks like a sure bet 
that Onondaga County will continue to see heavy snow. The new flow 
trajectory off Ontario should hit Cayuga County as well. Opted to 
keep Chenango/Cortland out of the warning due to this wind shift, 
but it is going to be a very close call. 


El heights continue to rise, indicating high instability. Snow 
growth region appears optimum as well, with plenty of Omega lift 
within. 


We may need to expand advisory into the southern tier of New York and 
possibly northern Bradford PA as tonight's trajectory will 
continue well into Saturday. Will forecast 3-5 inches over 
approximately 18 hours into the twin tiers for now. 


More shear is introduced into the wind flow Saturday afternoon, 
and the flow begins to swing back toward 300-310 by evening. So 
will bring bands back to the northern areas this period, but will 
forecast mainly multiband activity and lighter accums. 


High pressure building aloft should turn off the lakes by late 
morning Sunday. 


&& 


Long term /Monday through Thursday/... 
updated at 225 am...only change to medium range forecast was to raise probability of precipitation 
into the chance category for all areas days 6-7. Still diffs in the 
mdl's west/respect to potnl midweek storm...but given latest 
Euro/GFS and HPC manual forecasts...we'll likely see synoptic -shsn or 
lake induced activity...or combination of both next Wed/Thu. 
Previous below... 


Unsettled conditions...with below normal temperatures...is still 
anticipated for the foreseeable future. 


General model agreement about an anchored eastern U.S. Trough throughout 
the period. Detail differences continue amongst the medium range 
guidance with regards to how amplified this trough gets next 
week...which has implications on the degree of cyclogenesis that takes 
place near the East Coast. The European model continues to be the 
most aggressive with coastal storm development by the middle of 
next week...while the GFS is farther north and not quite as well 
developed. 


Once again...given much uncertainty...have utilized HPC grids. We 
generally have a chance of rain or snow on Monday...followed by 
daily chances for snow shower activity...as colder air tries to reload and 
build in from the northwest. 


&& 


Aviation /08z Friday through Tuesday/... 
Lake effect snows will cause MVFR to IFR conditions across central New York 
in favored areas. At this time...believe rme will see gnrly VFR this 
morning...with MVFR later this afternoon and possibly tonight as flow aligns from 
the west-northwest. Elsewhere across central New York...nearly low level flow this morning 
will gradually back...with widespread MVFR to IFR conditions in 
shsn...most persistent at syr/ith/bgm. At Elm and avp...potnl for 
brief MVFR in -shsn but expect VFR to prevail at these sites. Later 
tonight...expect MVFR to IFR to prevail at syr/ith/bgm due to les. 
Winds nearly this morning 5-10 kts...becmg west-northwest this afternoon 10-20 kts. 


Outlook... 


Friday night into Sunday...occasional MVFR/IFR expected...as a 
prolonged lake-effect snow event sets up over the region. 


Later Sunday into Monday...improvement back to VFR foreseen. 


Later Monday and Tuesday...restrictions may develop again...as 
rain or snow could impact the terminals. 


&& 


Bgm watches/warnings/advisories... 
PA...none. 
New York...Lake effect Snow Advisory from 10 am this morning to 10 am EST 
Sunday for nyz009-016-037-044-045. 
Lake effect snow warning from 10 am this morning to 10 am EST 
Sunday for nyz017-018-036. 


&& 


$$ 
Synopsis...djp 
near term...djp 
short term...djp 
long term... 
aviation...