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Area forecast discussion 
National Weather Service Buffalo New York 
335 am EST Wednesday Dec 3 2008 


Synopsis... 
a ridge of high pressure will give all of western and central New 
York a break in the recent wintry pattern today with some sunshine 
and mild temperatures. A sharp cold front will cross the region 
Thursday morning with rain showers ahead of it and snow showers in 
its wake. This will usher in a shot of midwinter cold and associated 
lake snows from Thursday night into early Saturday. 


&& 


Near term /through tonight/... 
the combination of warming temperatures aloft and increasing low 
level wind shear has caused the lingering lake effect snow to end. 
Our main focus then shifts to the cold front that is pushing through 
the upper Midwest and Central Plains early this morning. Southerly 
downsloping winds ahead of the front will allow temperatures to warm 
into the lower to middle 40s across most of the County Warning Area today. The moderate 
southerly flow will give the air a chilly feel though. 


In terms of sunshine...the latest infrared image shows the clouds thinning 
across the Genesee Valley and Finger Lakes area...but a steep 
subsidence inversion...based around 5k feet is trapping low level 
moisture across the far western part of the state and east of Lake 
Ontario.Still expect these clouds to thin out as much drier air 
above the inversion mixes down with the onset of daytime heating. 


The aforementioned cold is forecast to cross the central great 
tonight and reach far western New York by 12z Thursday. A 40 to 50 
knot low level jet surging ahead of the front will transport 
increasing low level moisture north from the lower Mississippi 
Valley into our area. A 120 knot upper level jet tracking from the 
central greats to southern Ontario will also enhance the large scale 
lift. Based on this...will continue with the trend from the previous 
forecast and indicate a west to increase in probability of precipitation overnight. Since 
most of the County Warning Area will still be under the influence of a relatively 
mild southwest flow...expect most of the precipitation to fall as rain. The 
far western part of the state could see a mix of rain and snow 
toward daybreak as 850 mb temperatures dip to about -5c right behind 
the cold front. 


&& 


Short term /Thursday through Saturday/... 
the cold front will work its way across western areas Thursday 
morning and reach eastern New York later in the day. Strong cold 
advection will follow the front but there will be strong subsidence 
and surface ridging so there will be little Post frontal precipitation. 
Rain showers will briefly change to snow showers but end quickly 
with little/no accumulate. 


Then we turn our attention to the lake effect potential. Some of the 
coldest air of the Young season will advect across the lakes Thursday 
nt into Saturday am with 850 mb temperatures of -14c to -16c but we have 
some caveats...especially off Erie. There will remain good surface 
ridging and very dry air through this period...and with flow more 
270-280 there will be little if any moisture picked up from Huron or 
the upper lakes. There will undoubtedly be some activity...maybe a 
few/several inches eventually on the Chautauqua ridge Thursday nt and 
Friday...but confidence is too low for watch in this area. Will start 
to increase probability of precipitation here late Thursday afternoon. 


Conditions will be somewhat more favorable off Ontario with 270-280 
flow setting up Thursday evening and continuing through most of Friday before 
backing to 250-260 Friday nt. 00z nam12...which has been doing a good 
job of late...is a bit meager with quantitative precipitation forecast...less than in previous 
runs...and again this may be due to the very dry air advecting in. 
Still...with some hint of multi-lake connection and little 
shear...feel a bit more confident on getting warning level snowfall 
on Tug Hill/Oswego County so will issue a lake effect watch for 
Oswego/Lewis/Jefferson cos from 7 PM Thursday to 7 am Sat. Jeff city 
will not see too much till late Friday or Friday nt when winds back a bit 
but later shifts can pinpoint it better as we get closer to the 
event. 


Finally...as for buf metropolitan potential...winds do indeed back to a 
favorable 240-250 vector from about 04z to 14z Sat...with little 
shear and decent moisture fields...so there is potential of at least 
a few inches across the area predawn Saturday...but then...band should be 
in the process of weakening as it lifts north later Sat morning as 
winds back further and shear increases. 


Later Saturday...a clipper moves to Lake Michigan and then into 
mich...will bring chance of light snow to west in afternoon as it gets 
closer. Surface flow will be S-southeast though so little accumulate. 


&& 


Long term /Saturday night through Tuesday/... 
the clipper low will move to vicinity of western New York by 12z Sunday then 
redevelop off new eng coast later sun and sun nt. We should all get 
some light snow Sat nt and sun am...but accums look minor...couple 
inches at best. North country will see the least so maintained only 
chance probability of precipitation there...likely elsewhere...lowering from west to east in 
afternoon. 


A shot of colder air follows late sun/sun nt with some snow 
showers...but northerly flow should inhibit much lake effect. Strong 
ridge crosses area Monday for a dry day...then next system 
approaches from west Tuesday with southerly flow ahead of it. Kept chance 
probability of precipitation Tuesday but introduced rain showers in west due to pattern 
recognition with these warm advection patterns as 850 mb's warm to 
-5c or higher in afternoon. 


&& 


Aviation /09z Wednesday through Sunday/... 
ridging will begin to partially clear things out a bit overnight. 
Any early MVFR ceilings northeast of the lakes should become VFR by 
08z. The rest of the night will be VFR and also all day Wednesday 
with just middle and upper decks of clouds. A cold front will 
approach Wednesday night with rain beginning over the western 
sites by the end of this taf period. 


Outlook... 


Late Wednesday night...MVFR/IFR overnight in rain. 
Thursday MVFR in snow showers...IFR east of the lakes in lake 
effect snow. 
Friday...IFR in lake snows east of the lakes..VFR 
elsewhere. 
Saturday...deteriorating to IFR/MVFR in widespread snow 
showers. 
Sunday...MVFR with IFR southeast of Lake Ontario in lake snows. 


&& 


Marine... 
look for fresh south to southwest winds today...increasing to near 
gale force later tonight just ahead of the cold front. Winds will 
then shift abruptly to the west and northwest in the wake of the 
front Thursday with brisk westerlies continuing into Friday. 


Wind speeds will be sufficient for small craft advisories off Lake 
Erie and the east end of Lake Ontario through at least Friday. Gale 
warnings will be issued for the Open Lakes tonight. 


&& 


Buf watches/warnings/advisories... 
New York...Lake effect snow watch from Thursday evening through Saturday 
morning for nyz006>008. 
Marine...Small Craft Advisory until 9 PM EST this evening for lez040- 
041. 
Gale Warning from 9 PM this evening to 7 am EST Thursday 
for lez040-041. 
Small Craft Advisory until 7 am EST Thursday for lez020. 
Gale Warning from 1 am to 7 am EST Thursday for 
loz043>045-063>065. 
Small Craft Advisory until 1 am EST Thursday for loz045. 


&& 


$$ 


Synopsis...sfm 
near term...tjp 
short term...sfm 
long term...sfm 
aviation...jjp/Sage 
marine...sfm/tjp 

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