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Area forecast discussion 
National Weather Service Buffalo New York 
1013 PM EDT sun Sep 7 2008 


Synopsis... 
showers across the Eastern Lake Ontario region will diminish 
overnight. High pressure building east will bring clearing to the 
rest of the region tonight. The high will bring mostly sunny skies 
on Monday morning then a cold front approaching from the central 
Great Lakes will bring an increase in clouds later Monday with a 
better chance for showers and thunderstorms Monday night and 
Tuesday. Clearing skies and cool temperatures will follow the front 
Tuesday night and Wednesday. 


&& 


Near term /through Monday/... 
raised probability of precipitation to likely through late evening across the north country 
with area of rain on radar currently moving through that region. 
Elsewhere mainly clear to partly cloudy skies. 


The NAM shows a lake band off east end of Lake Ontario lt tonight so will 
continue chance probability of precipitation there overnight. Some potential to Lee of Lake 
Erie as well but not totally committed to mention in zones but have 
put in slight chance probability of precipitation in grids for now. No change to min temperatures 
overnight. 


Earlier forecast had ridging on Monday with sunshine and highs in 
the middle and upper 70s. There is some doubt in amount of sunshine for 
Monday. 18z NAM even brings in chance of showers with short wave ahead of 
weak cold front over the Central Lakes but 18z GFS still keeps area dry 
with possible exception of area up around the St law valley. Next shift 
will probably have to add at least more clouds to Monday forecast. 


&& 


Short term /Monday night through Wednesday night/... 
the GFS and the NAM track an intensifying low northeast toward the 
lower Great Lakes Monday night before lifting it our across southern 
Quebec Tuesday. The main forecast challenge is that the models still 
differ somewhat on the track and timing of the low as it get closer 
to New York state. The NAM keeps the main center of the low farther 
to the northwest and is slower with the eastward progression of the 
trailing cold front which will cross New York state on Tuesday. 
This timing difference not only has implications regarding the 
potential for convection on Tuesday...but it will also impact the 
temperature trends for Tuesday. At this time...plan to follow the 
more progressive solution of the GFS which is closer to the timing 
depicted by the European model (ecmwf) and preferred by HPC guidance. Following this 
trend...will indicate a gradual northwest to southeast increase in 
probability of precipitation across the area Monday night...while tapering the precipitation off 
Tuesday afternoon. Convection is still a possibility Monday night 
into Tuesday morning as moist and somewhat unstable air surges ahead 
of the approaching cold front. Strong low level and upper level jets 
tracking east across New York state will generate additional lift. 
Expect most of the convection to be east of our County Warning Area by early Tuesday 
afternoon as the cold front moves into eastern New York state. We 
may also see steady or slowing falling temperatures during the 
afternoon with the GFS showing 850 mb temperatures cooling to about 
plus 4c during the afternoon...after starting out in the lower teens 
at 12z Tuesday. 


The anticipated track of the surface low...just north of Lake 
Ontario...will also generate breezy to windy conditions late 
Monday night through at least Tuesday morning...especially 
downwind of Lake Erie where the winds will channel up the lake. 


The circulation between the departing surface low and high pressure 
riding into the Great Lakes will set up cool northerly flow across 
the area Tuesday night. It still seems that there will not be enough 
moisture in the boundary layer for the development of widespread 
lake effect clouds or precipitation. 


Wednesday will feature mostly sunny skies...but temperatures will 
stay in the 60s with 850 mb temperatures forecast to stay below plus 5c. 
The center of the surface ridge is forecast to move across New 
England Wednesday night. This will result in mainly clear skies and 
light southeast winds...favoring good radiational cooling which may 
allow temperatures to dip into the middle and upper 30s across the 
interior valleys of the southern and east of Lake Ontario. 


&& 


Long term /Thursday through Sunday/... 
Thursday will feature mostly sunny skies with high pressure centered 
over New England still in control. Expect temperatures to moderate 
to more seasonable levels. Clouds will begin to increase Thursday 
night as the high slides off the East Coast and a cold front 
approaches from the central Great Lakes. A few showers are possible 
before daybreak Friday. The increase in cloud cover and increasing 
southerly winds will also keeps overnight lows milder than the 
previous two nights. 


Showers will become more widespread Friday as the cold front tracks 
east across the state. The weather will remain somewhat unsettled 
Saturday and Sunday with a few more fronts forecast to cross the 
area. But...a lower amplitude zonal flow aloft may allow 
temperatures to moderate to slightly above average levels during 
the second half of the forecast period. 


&& 


Aviation /02z Monday through Friday/... 
an area of showers over the eastern end of Lake Ontario will move 
across the north country at the beginning of the taf period and will 
bring occasional MVFR conditions through around 03z-05z. Elsewhere VFR 
conditions will predominate through the taf period. Fog is expected 
to from later tonight across the southern tier and is expected to 
lower conditions to LIFR to vlifr form 08z-13z. Some lake effect 
clouds and showers are expected east of Lake Ontario later tonight 
into Monday morning and will create MVFR conditions. 


Monday night and Tuesday...areas of MVFR with a cold front and 
possible thunderstorms. 
Wednesday and Thursday...VFR. 


&& 


Marine... 
high pressure ridging north from the Ohio Valley maintain a westerly 
flow on the lakes tonight through most of Monday with no significant 
waves expected. Increasing southwest to west winds associated with a 
passing cold front will likely generate Small Craft Advisory 
conditions on the lakes late Monday night and Tuesday. High pressure 
riding into the lower lakes will allow winds and waves to subside 
Tuesday night and Wednesday. 


&& 


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


&& 


$$ 


Synopsis...jjp/tjp 
near term...apb/jjp 
short term...tjp 
long term...tjp 
aviation...jjp/apb 
marine...tjp