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Area forecast discussion 
National Weather Service Buffalo New York 
314 PM EDT Sat Sep 6 2008 


Synopsis... 
scattered showers will end this evening as the remnants of Tropical 
Storm Hanna move east to New England. An upper level disturbance 
will bring a chance for a few showers on Sunday before high pressure 
brings dry conditions Sunday night and Monday. A cold front 
approaching from the central Great Lakes will bring a better chance 
for showers and possible thunderstorms Monday night and Tuesday. 


&& 


Near term /through Sunday/... 
the rain west of the area that was associated with a weakening cold 
front has almost dissipated and will not be a factor in the forecast 
tonight. The outer rain bands of Hanna east of the Genesee Valley 
and east of Lake Ontario are weakening as they get stretched 
northward. We have lowered the probability of precipitation to chance in the late afternoon 
and evening, and move the rain out of the area by midnight as Hanna 
moves east toward New England. However clouds will linger with 
clearing in the west not until around midnight and east of Lake 
Ontario not until close to dawn. With the recent rain we have put 
areas of fog in the southern tier...which is normal for this time of 
year. 


Both the NAM and GFS bring a short wave across the area Sunday 
afternoon, and we have followed guidance with clouds and chance 
pops, but only minor precipitation amounts are expected. 


&& 


Short term /Sunday night through Tuesday night/... 
any showers left over from Sunday should end quickly in the evening 
as the energy associated with the passing short wave moves into New 
England. Otherwise...expect mainly dry conditions Sunday night as 
high pressure ridges north from the Ohio Valley. The high will 
maintain dry conditions on Monday as it keeps precipitation associated with 
the southern Ontario trough to our north. 


The weather has the potential to become a little active Monday night 
as a strong low level jet advances ahead of the intensifying central 
Great Lakes low and its trailing cold front. The combination of 
strong low level moisture convergence with the low level jet and 
added lift in the rrq of an approaching upper level jet streak will 
set the stage for showers and possibly some elevated convection. 


Strong warm air advection associated with the low level jet will 
cause 850mb temperatures to rise to +15c to +16c between 06z and 
12z. Thus...will follow the trend started by the previous shift and 
keep Monday night's low temperatures higher than guidance...while 
showing increasing temperatures after midnight. 


Expect showers and thunderstorms to continue Tuesday as the cold 
front advances across western and central New York during the 
afternoon and interacts with moist...unstable air in the boundary 
layer. Additional lift associated with a vigorous upper level trough 
could set the stage for some active convection...if we can get some 
sunshine. A well defined dry slot following the front should allow 
most of the showers to end before 00z Wednesday. 


Strong cold air advection behind the front will cause 850 mb 
temperatures to dip to about plus 3c by 12z Wednesday. The 
corresponding surface temperatures will cool into the 
40s...especially at inland locations away from the lakes. 
At this time...it seems that a lack of moisture in the boundary 
layer may preclude the development of showers as the colder air 
crosses the warmer water of the lakes. 


&& 


Long term /Wednesday through Saturday/... 
high pressure centered over New York state will bring mostly sunny 
skies with temperatures in the 60s as 850 mb hover just below plus 
5c. As the center of the high shifts to New England Wednesday 
night...a light southeast flow will set up across the area...but 
another chilly night is anticipated with temperatures expected to 
range through the 40s. 


Thursday will feature mostly sunny skies with the New England high 
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 and possible thunderstorms will become more widespread 
Friday as the cold front pushes across New York state. High pressure 
should bring mainly dry conditions on Saturday. 


&& 


Aviation /19z Saturday through Thursday/... 
occasional IFR ceilings and visibility will improve from the west 
this evening as moisture from Hanna withdraws east. Conditions will 
lift to VFR with some dense fog forming in the southern tier 
overnight. Moisture with an approaching short wave will bring 
lowering ceilings and a chance of showers Sunday afternoon, but 
conditions should remain VFR. 


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


&& 


Marine... 
a northwest flow in the wake of T.S. Hanna will produce choppy 
conditions on the lakes tonight. High pressure ridging north from 
the Ohio Valley will set up westerly winds on the lakes Sunday and 
Monday with no significant increase in waves expected. 
Increasing southwest winds ahead of an approaching cold front may 
generate Small Craft Advisory conditions on Tuesday. 


&& 


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


&& 


$$ 


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