Weather

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Area forecast discussion 
National Weather Service Buffalo New York 
256 PM EDT Thursday Aug 21 2008 


Synopsis... 
high pressure will become anchored off the New England coast during 
the next couple days...and this will result in more fair dry 
weather. Our stretch of rain free weather will likely end on Sunday 
when a passing cold front will produce some showers and 
thunderstorms. Canadian high pressure will then bring US another 
round of pleasantly cool late Summer weather Monday and Tuesday. 


&& 


Near term /through Friday/... 
high pressure will continue to dominate the region overnight and 
Friday. Valley fog will again develop overnight then limited high 
cloudiness may approach the western sections of the County Warning Area late 
tonight/Friday as a weak middle level low works its way north across 
the central Great Lakes Friday. 


Temperatures Friday are expected to climb into the middle/upper 80s in 
most locations...with a few of the normally warmer spots in the 
Genesee Valley reaching 90. Recoord high at buf is 87 and may be in 
jeopardy...but the record of 98 at roc will hold. 


&& 


Short term /Friday night through Sunday night/... 
this period will be characterized by seasonably warm and 
increasingly humid conditions...with our string of rain free days 
coming to an end. 


A 592dm 500 mb ridge extending northwards across the eastern Great Lakes 
and New England on Friday night will start to flatten on Saturday as 
a Canadian shortwave will lift across northern Ontario. The 
resulting deep southwesterly flow will keep warm air flowing into 
our region...while low level moisture will be on the increase. Dew 
points that have been below 55 for a few days will rise into the low 
to middle 60s for much of the region by Saturday afternoon...and when 
coupled with 850 mb temperatures of +17...we can expect a middle Summer type day. 
It will remain dry for Saturday though...as high pressure off the 
New England coast will extend back across our region and will thus 
keep the deep moisture plume to our west. 


On Saturday night...our ridge will succumb to the northern Ontario 
shortwave that will be in the process of carving our a proghressive 
long wave trough over the Great Lakes. The associated surface cold front 
will drop across lower Michigan and southern Ontario Saturday 
night...while moisture will pool across our region in advabnce of 
the slow moving front. Will keep the low chance probability of precipitation across the bulk of 
our region for the chance for rain showers/thunderstorms and rain later that night. 


As the long wave trough will cross Quebec on Sunday...the surface cold 
front will be easing across our forecast area. The operaitonal GFS 
and several members of the gefs ensembles suggest that a wave along 
the front will slow its southeastward progression...and any such 
wave would also help to increase the overall lift and precipitation 
potential. Will leave our likely probability of precipitation in play...which are somewhat 
higher than surrounding wfo's and model guidance packages. 


As the front settles to the southeast of the forecast area Sunday 
night...probability of precipitation will decrease accordingly from northwest to southeast 
as the night progresses. 


&& 


Long term /Monday through Thursday/... 
while this four day period will likely consist of another stretch of 
dry and comfortable late Summer weather...the specter of Fay will 
remain as the lone fly in the ointment. 


Medium and long range guidance packages are favoring the scenario 
where the next long wave ridge will build across the Mississippi 
Valley on Monday...then across the Great Lakes and New England 
during the Tuesday to Thursday time frame. An expansive Canadian surface 
high under this ridge would then keep all the tropical moisture to 
our south. The operational 12z run of the GFS has come into line by 
weakly suggesting this...but the more convincing solutions remain 
within the ensembles of the gefs. It would have been nice to see the 
fresh output from the European model (ecmwf)...but that guidance will be too late to 
be incorporated into this package. 


The drier scenario was also favored by HPC...whose graphics depicted 
a blocking surface high through the bulk of the period. Will thus keep 
any mention of precipitation out of the extened package and just use slight chance 
probability of precipitation. This also aligns well with our neighboring wfo's. 


&& 


Aviation /19z Thursday through Tuesday/... 
VFR conditions are expected to prevail over the next 24-36 hours as 
high pressure dominates the region. Valley fog is again expected to 
develop later tonight through Tuesday morning. 


Outlook... 
Saturday...VFR. 
Sunday...possible MVFR in scattered showers and thunderstorms. 
Monday/Tuesday...VFR. 


&& 


Marine... 
no flags are expected through Saturday. 


High pressure over New Jersey this evening will become anchored off 
the New England coast later tonight through Saturday. As a 
result...a weak surface pressure gradient will be found over lakes Erie 
and Ontario. This will keep winds and waves below Small Craft 
Advisory criteria with nearly ideal sailing conditions expected. 


Winds and waves will increase on Sunday during the passage of a cold 
front...with the potential for Small Craft Advisory conditions most 
likely in the wake of the front Sunday night over parts of Lake 
Ontario. Along with the choppier water on Sunday...there will be the 
liklihood of thunderstorm activity. 


&& 


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


&& 


$$ 


Synopsis...rsh 
near term...Levan 
short term...rsh 
long term...rsh 
aviation...Levan 
marine...rsh