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Area forecast discussion 
National Weather Service Buffalo New York 
909 PM EDT Sat Mar 20 2010 


Synopsis... 
a weak cold front will settle slowly south across Pennsylvania 
tonight. An area of limited moisture between the frontal boundary 
and high pressure extending from Quebec to the Central Lakes will 
persist over the area through Sunday. A more widespread rain will 
arrive later Monday into Tuesday as a stronger area of low 
pressure moves into the Middle Atlantic States. 


&& 


Near term /through Sunday/... 
local surface observations and weather radars showing that the cold 
front continues to sag across western Pennsylvania this evening. 
Expect the front to slow and stall over southern PA overnight with 
only middle level cloudiness across our forecast area...rather than the 
lower clouds earlier thought. Have lowered probability of precipitation to low chance range 
for the possibility of a few sprinkles or light showers...a low 
chance of any measureable precipitation over the southern tier late 
overnight. 


On Sunday...expect a wave to lift across the north country...with 
a chance rain or snow showers. Elsewhere see a chance of showers in 
the morning...but as the front meanders north...may see improving 
conditions in the southern tier. Temperatures will vary 
significantly across the forecast area...with the sharp gradient 
resulting in a low confidence forecast. Generally favor a blend 
between the nam12/rgem for temperatures...ranging from highs near 40 
in the north country...with 60 again a possibility in interior 
portions of the southern tier. 


&& 


Short term /Sunday night through Tuesday/... 
there will be a break in precipitation Sunday evening with most or all of 
the County Warning Area briefly dry. Later Sunday night moisture ahead of the 
frontal boundary just to our south will begin to spread northward. 
Will bring in chance of showers to the southern tier and southern 
Finger Lakes. High pressure over Ontario though should keep areas 
further to the north dry overnight but will bring in increasing 
clouds. 


On Monday the closed upper low over Alabama lifts northeast to 
Virginia by Tuesday whi8le the surface low over the Ohio Valley Monday 
moves to Pennsylvania Tuesday morning. Moisture ahead of the low 
will lift north during Monday and will sperad a chance of showers to 
much of the region except the far north country by the afternoon 
with probability of precipitation becoming likely across the southern tier in the afternoon. 


It looks like the best chance of rain will come Monday night into 
early Tuesday as a southeast flow of Atlantic moisture ahead of the 
low overspreads the region and will increase probability of precipitation to categorcial 
over the entire region. During Tuesday will keep Cat probability of precipitation east of 
Lake Ontario through middle afternoon as the low moves to eastern PA 
and lower probability of precipitation to chance range for areas from The Finger lakes west. 


&& 


Long term /Tuesday night through Saturday/... 
moist cyclonic flow around low east of Cape Cod will keep chance probability of precipitation 
over the region Tuesday night mainly across areas east of Buffalo. 
Temperatures get cold enough for threat of snow showers east of Lake Ontario 
later at night and also across interior sections of the hills 
southeast of Buffalo. Will lower probability of precipitation to slight chance range Wednesday 
morning as low moves further east of Cape Cod then drier air from 
the Central Lakes moves east into the region during the afternoon 
with skies becoming partly sunny. Temperatures continue above normal getting 
to the upper 40s to lower 50s. 


Wednesday night, the European model (ecmwf) drops a rather dry cold front down from 
southern Ontario and northern New York while it sends a middle level 
short wave east across Quebec. Meanwhile, the GFS has a stronger 
short wave moving further south across northern New York to New 
England by Thursday morning with more lift across central and 
northern New York and spits out some precipitation from The Finger lakes eastward 
during the evening. It is also quite a bit colder behind the front 
at 850mb (-6 to -10c by 12z Thursday vs -1 to -6c on the ecmwf). At this 
time will keep chance probability of precipitation only across the Eastern Lake Ontario 
counties in the evening tapering to slight chance back into the central 
Finger Lakes and nothing further west. Again it looks like some snow 
could mix in across the north country before the threat of precipitation 
ends later at night. 


Thursday, high pressure shld bring fair weather with highs in the 
middle to upper 40s. Another cold front drops southeast across the area 
Thursday night with limited moisture. Again the European model (ecmwf) is drier and 
not as cold behind the front. Will go more toward the European model (ecmwf) and keep 
probability of precipitation only in the slight chance range for the bulk of the region, 
except for the far north country. 


On Friday, the front moves further south into Pennsylvania and 
chilly high pressure over Quebec builds south into the region. Will 
keep slight chance probability of precipitation in for areas from The Finger lakes westward as cold 
northerly upslope flow south of Lake Ontario could generate an 
isolated shower. Temperatures will be cold enough in the morning for it to be 
in the form of snow as well. 


The high will keep dry weather over the area Saturday but both 
Friday and Saturday will see below normal temperatures. Highs in the low to 
middle 40s are expected Friday and the same for Saturday but areas east 
of Lake Ontario are only expected to reach the middle to upper 30s. 


&& 


Aviation /01z Sunday through Thursday/... 
a frontal boundary will stall near Pittsburgh this evening...with 
little movement through Sunday morning. Little weather will be 
associated with the front. Upstream radar and surface observations 
show only middle deck cloudiness with little low level moisture. Will 
keep tafs dry with middle level ceilings...VFR through the night and 
Sunday. 




Outlook... 
Sunday night through Monday night...MVFR/IFR with rain likely. 
Tuesday...MVFR/VFR. A chance of showers. 
Wednesday and Thursday...VFR likely. 


&& 


Marine... 
no marine flags are expected through the rest of the weekend 
as relatively weak pressure gradients will be in place across the 
lower lakes. Winds and waves should remain below Small Craft 
Advisory criteria through Monday. Northeast winds are expected to 
increase Monday night as the pressure gradient tightens between high 
pressure over Quebec and low pressure over the Middle Atlantic States. 


&& 


Buf watches/warnings/advisories... 
New York...none. 
Marine...none. 


&& 


$$ 


Synopsis...jjp 
near term...apffel/wch 
short term...jjp 
long term...jjp 
aviation...wch 
marine...apffel/jjp 

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