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Area forecast discussion 
National Weather Service Buffalo New York 
932 PM EDT Wednesday Jul 23 2008 


Synopsis... 
the massive upper low which has caused the unsettled weather of 
late will move across the eastern lakes Thursday and finally lift 
off to Quebec by Friday. This will keep the threat of showers and 
thunderstorms across the region through Thursday before a dry mild 
day on Friday. Another weak front will cross the lakes on Saturday 
and bring a return to unsettled conditions...while slow 
improvement will follow early next week as high pressure builds in 
from the Ohio Valley. 


&& 


Near term /through Thursday/... 
areas of showers and thunderstorms continue this evening over 
portions of the area. First...across western New York a large cluster of 
storms is located over northwest PA. The movement of these storms is 
nothing short of bizarre with storms moving towards just about every 
point on the Compass. Low level flow has become highly complex with 
numerous convectively generated outflow boundaries superimposed over 
weak/shallow northeast flow at the surface. The center of the middle 
level circulation is now in northwest PA...and will continue to drift 
slowly east overnight. Numerous impulses of vorticity rotating 
around the middle level low combined with low level moisture 
convergence will continue to support the area of rain/storms in northwest 
PA through at least the first half of tonight. Some of these may 
eventually drift into the southern tier as well. Given the very slow 
moving nature of these storms will have to monitor trends very 
closely for potential flooding concerns. 


Another small area of showers is also starting to develop over 
Western Lake Ontario offshore of Toronto...drifting slowly south. 
This appears to be in an area of low level convergence to the 
northwest of the parent surface low across the twin tiers of NY/PA. 
This area may tend to Blossom overnight and work slowly south 
towards the Niagara Frontier. 


East of Lake Ontario...a large area of convection continues to lift 
slowly north through the Saint Lawrence valley within the warm 
advection Wing ahead of the surface low. This has produced some very 
heavy rainfall locally in northern Jefferson County...up 2.5 inches 
at Cape Vincent. Expect this to lift into Canada through midnight. 
Additional rain and storms over the middle Atlantic will spread north 
overnight in response to very strong jet dynamics...by in large 
missing the County Warning Area to the east. Do expect some westward development 
however as the upper trough continues to dig over western New York...which 
should allow for deeper lift and some rain to develop again late 
across the Eastern Lake Ontario region. 


Have attempted to offer some temporal and spacial details in the 
grids for the next 6 hours. The Niagara Frontier from buf-roc should 
be mainly dry through the wee hours of the morning...but did bring 
chance probability of precipitation into all areas again late tonight given the high degree 
of uncertainty with respect to mesoscale-Beta scale forcing mechanisms. 
Most likely areas for more widespread rain tonight would be the 
southern tier and east of Interstate 81. 


Chance probability of precipitation will linger across the entire County Warning Area on Thursday as the 
upper trough and low move west to east across the region. Any breaks 
in the cloud cover will only help to destabilize the lower 
atmosphere and produce scattered thunderstorms and rain within the general coverage of 
scattered showers. Temperatures will remain a little below normal under the 
cloud cover and scattered precipitation. 


&& 


Short term /Thursday night through Saturday night/... 
cut off low over eastern New York at the start of the period will 
lift northward into Quebec by Friday and take the threat for 
convection with it. Weak high pressure will work into the area 
Friday and bring a break in precipitation...before the next trough 
works down across the area on Friday with a renewed threat of 
convection. 850 mb temperatures of 16c Friday should allow temperatures to break 
80 over most spots...then cool to the mid to upper 70s on Saturday with 
cooler middle level air working in along with more cloudiness. 


&& 


Long term /Sunday through Wednesday/... 
GFS/HPC graphics show high pressure gradually building east from 
the Ohio Valley through this period but we will still be in a 
general west to northwest flow aloft with minor ripples moving 
along it. Will keep 30 probability of precipitation in for Sunday with a more distinct 
short wave...then lower pop to 20 Monday and 10 Tuesday and 
Wednesday...but confidence fairly low. Still...it looks to be less 
unsettled than this week. Temperatures will average a degree or two below 
normal...averaging in u70s to near 80. 


&& 


Aviation /02z Thursday through Monday/... 
for the time being rain has moved away from all the taf sites... 
although storms are still lurking nearby kjhw. For now have tafs 
mainly dry overnight given highly uncertain motion and placement of 
convective activity. Will continue to monitor trends and amend as 
necessary. 


Most of the County Warning Area is VFR...with a few patches of MVFR ceilings across 
western New York. Expect this to be the case through the first 6-10 hours 
of the 00z taf cycle. Late tonight...NAM BUFKIT profiles and MOS 
guidance suggest the abundant low level moisture field will Foster 
the development of areas of low stratus. Have gone with this idea in 
the terminals with low end MVFR ceilings and some visibility restriction after 
about 09z...but forecast confidence is low. 


Expect additional scattered showers Thursday as extensive wrap 
around moisture crosses the region on the western side of the middle 
level and surface lows. MVFR ceilings should be common across much of 
the area...especially from the morning through early afternoon with 
little in the way of mixing to erode the low level moisture. 


Outlook... 
Friday...VFR. 
Saturday and Sunday...VFR/MVFR in scattered shra/tsra. 


&& 


Marine... 
no marine headlines for the foreseeable future. 


Look for general light winds to continue through Friday with flow 
tending westerly Thursday and Friday. The next frontal passage 
looks to be Saturday but overall winds should remain generally westerly 
at moderate speeds through the weekend. 


&& 


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


&& 


$$ 


Synopsis...sfm 
near term...Hitchcock/wch 
short term...sfm 
long term...sfm 
aviation...Hitchcock 
marine...sfm/wch 

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