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Area forecast discussion 
National Weather Service Buffalo New York 
154 PM EDT Friday Jul 18 2008 


Synopsis... 
typical middle Summer weather will continue through the weekend as 
high pressure builds over the eastern states. It will remain dry 
most of the time...however isolated to scattered mainly afternoon 
and evening thunderstorms are possible. Low pressure in the upper 
atmosphere will approach the area late Sunday into Monday and 
bring with it an increased threat of thunderstorms. High pressure 
and somewhat drier air and near normal temperatures is then 
expected for the middle of next week. 


&& 


Near term /through tonight/... 
expect the most of the region to remain dry through the 
afternoon/evening hours. Forecast concern again revolves around 
convective potential. Across most of the County Warning Area...building middle level 
heights and warming temperatures aloft will effectively cap the potential 
for deep moist convection. That said...with strong heating again 
combined with rich low level moisture...moderate to strong 
instability will develop with SBCAPE approaching 2000j/kg inland 
away from lake influences. With this type of instability present 
and the potential for locally enhanced low level convergence along 
lake breeze boundaries and over complex terrain of the southern 
tier/Finger Lakes...will maintain slight chance of storms across 
the southern tier and Finger Lakes. 


Severe Thunderstorm Watch has been issued for the north country. 
Strong middle level west-southwest flow is crossing the Saint Lawrence valley 
during peak afternoon heating. While the bulk of the activity 
should remain across far northern New York, the possibility of 
strong winds/large hail does exist over Oswego...Jefferson and 
Lewis counties. 


Temperatures this afternoon will again soar reaching into the low 
90s in areas away from the lakes. 


Convection should move east and weaken this evening with loss of 
daytime heating and eastward progress of the enhanced middle level 
flow. The weak frontal boundary will begin to sag slowly south 
again overnight in response to height falls spreading east through 
Quebec. The 00z NAM tries to generate some convection along the 
boundary as it sinks into the Niagara Frontier overnight. While 
this is not entirely out of the question...only a small percentage 
of sref members /less than 20 percent/ support this. The GFS also 
keeps the boundary dry...so for now have retained continuity and 
maintained a dry forecast overnight tonight. 


&& 


Short term /Saturday through Sunday/... 
the upper air pattern during the weekend will be characterized by 
a fast west to east flow...containing weak embedded shortwaves. 
Latest model runs continuing to show a weakening frontal boundary 
drifting south tonight and stalling over western New York during the 
weekend. This boundary will be the focus for scattered showers and 
thunderstorms...primarily during the afternoon and evening. The best 
chances for convection look to be Sunday with approach of a stronger 
shortwave. Severe weather threat during the weekend looks to be 
limited with overall rather weak wind fields with bulk shear 
generally less than 30 knots and elevated wet bulb zero heights 
above 12k feet. Nonetheless...still cannot rule out isolated severe 
threat. Heavy rainfall will be a threat as well with precipitable 
water values forecast to be near 2 inches. Though 850 mb 
temperatures will be around plus 18c...cloud cover should keep 
temperatures in the middle to upper 80s with humid dew points in the 
middle to upper 60s. 


&& 


Long term /Sunday night through Thursday/... 
an upper trough will bring an increased chance of convection late 
Sunday night into Monday, then as it pulls out high pressure with 
drier will build in from the west Tuesday with 850 mb temperatures 
falling to around +10, resulting in fair weather (only a slight 
chance of precipitation) and near normal surface temperatures around 
80 Wednesday and Thursday. 


&& 


Aviation /18z Friday through Wednesday/... 
scattered convection will continue to develop this afternoon 
across southern Ontario...moving across the north country. Some of 
these thunderstorms may reach severe limits and could reach to the 
vicinity of kart. 


Elsewhere...mainly VFR conds prevail...with limited areas of MVFR 
in haze. Overnight tonight expect a repeat performance with 
respect to br/fog with areas of MVFR...and local vlifr forming in 
the river valleys of the southern tier. 


Outlook... 
Saturday...mainly VFR except for isolated afternoon and evening 
thunderstorms. Areas of MVFR possible in br late Sat night. 
Sunday and Monday...shra/tsra with areas of MVFR. 
Tuesday...mainly VFR except for isolated afternoon and evening 
thunderstorms. 


&& 


Marine... 
southwest winds will freshen to around 20 knots on the eastern 
end of Lake Erie late this morning through early tonight ahead of 
a weak frontal boundary dropping south through the Great Lakes. 
Waves will build to around 4 feet during this time period... 
therefore will issue a Small Craft Advisory. Conditions on the 
western end of Lake Ontario will remain just below small craft 
threshold. Winds and waves will subside on both lakes later 
tonight. Winds should become variable with locally onshore flows 
developing both Saturday and Sunday as a weak surface front drops 
across the area and dissipates. 


&& 


Buf watches/warnings/advisories... 
New York...none. 
Marine...Small Craft Advisory until 7 PM EDT this evening for lez020- 
040-041. 


&& 


$$ 


Synopsis...Levan 
near term...Levan 
short term...tma 
long term...apb 
aviation...Levan 
marine...jjp/Levan