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Area forecast discussion 
National Weather Service Buffalo New York 
240 PM EDT Sat Jul 5 2008 


Synopsis... 
high pressure draped across the Great Lakes will settle 
slowly to the southeast the next few days...and will keep dry 
weather in place through Monday. A cold front is then expected to 
slowly drop across the Great Lakes Tuesday and Wednesday along with 
a chance of showers and thunderstorms. Following the front...high 
pressure will build back across the area during the remainder of 
next week...bringing a return to dry weather. 


&& 


Near term /through Sunday/... 
our glorious Holiday weekend weather will continue through Sunday 
as we will continue to lie under a weak surface ridge in area of 
subsidence well north and west of stalled frontal system over Middle 
Atlantic States. Flat upper trough over Ohio Valley will drift east 
and fill during Sunday but may just create enough marginal 
elevated instability for some isolated convection to drift up into 
our higher elevs of southern tier Sun afternoon so will have some slight 
chance probability of precipitation there. Nam12 develops some along Lake Erie boundary later 
Sunday but this look overdone. 850 mb temperatures rise to 14-15c or so 
Sunday...a solid 3 degree c warmer than today's..so we should easily 
tack on a good 4 to 6 degree f to today's maxes which are mostly in 
u70s to near 80. So will go with generally m80s for lower elevs. 
Winds will still be l/v so locally onshore again in afternoon. 


Backing up...a dry quiet night tonight after diurnal cumulus across 
higher elevs dissipates early this evening. Cant rule out a bit of 
valley fog but it should be limited...left it in for an hour or 
two after midnight in most prone areas. 


&& 


Short term /Sunday night through Monday night/... 
dry weather should continue right through Monday as low level 
ridging remains in control across our area...and the weak upper 
level trough over the Ohio Valley slowly drifts east and dissipates. 
The vast majority of any convection associated with this latter 
feature should remain a little to our south and east Sunday night 
and Monday...so have gone with no higher than slight chance probability of precipitation 
along the southeastern periphery of the County Warning Area during this time 
frame...and even lower values elsewhere. 


As we get into Monday night...the slow-moving cold front situated 
over the central Great Lakes on Monday should begin pushing into 
southern Ontario. As this feature may get close enough to western 
portions of the area later Monday night to touch off a little 
convection...have kept low chance probability of precipitation in the forecast across the 
far west for the second half of the night. 


The persistent southwesterly flow on the back side of the low level 
ridge will result in a continued flow of increasingly warm and humid 
air across the area during this period. By Monday...850 mb 
temperatures readings will likely warm to about +16 to +17c...enough 
to support widespread high temperatures in the middle to upper 80s. 


&& 


Long term /Tuesday through Saturday/... 
the aforementioned cold front is forecast to sag slowly southward 
across the Great Lakes region Tuesday and Wednesday. This will 
result in a increasingly better chance of convection early in the 
long term period...with the highest probabilities of precipitation 
likely with the frontal passage itself later Tuesday night and Wednesday. 
Given our still somewhat-distant Vantage Point...have restricted 
probabilities to the upper half of the chance range for now...though 
these may need to be increased as this time frame draws closer. 


Following the frontal passage...have stuck with existing continuity 
and the HPC/ECMWF/GFS idea of high pressure building across the area 
with a return to dry weather for the remainder of the week. 


As for temperatures...the start of the period will feature more 
summertime warmth and humidity in advance of the cold frontal 
passage...with 850 mb temperatures of +17 to +18c supporting 
widespread readings in the middle to upper 80s on Tuesday...and 
possibly a few 90 degree readings across the normally warm spots of 
the Genesee Valley and Finger Lakes. Our temperatures should then drop 
closer to near normal levels /highs around 80/ with the frontal 
passage on Wednesday...and even a bit below normal on Thursday with 
the stronger cold advection in the wake of the boundary. Current 
projections are that this cold air advection will be strong enough to result in 850 
mb temperatures dropping to around +8c...which would support highs in the 
comfortable lower half of the 70s on Thursday. 


Thereafter...a warming trend is expected through the remainder of 
the period as the axis of the surface ridge shifts to our east...and 
upper ridging builds back across the Great Lakes. While the GFS and 
European model (ecmwf) disagree on the magnitude of the warming trend...feel that we 
should see daytime highs return to at least a little above normal 
/into the lower 80s/ by Saturday...if not a bit higher. 


&& 


Aviation /19z Saturday through Thursday/... 
aside from some localized valley fog late tonight across the 
southern tier...conditions will remain VFR through the 24 hour taf 
period through 18z Sunday. Patchy cirrus will drift across the 
region from time to time while some VFR based cumulus will form on 
Sunday away from the lakes. Winds will be light through the 
period as a surface high settles over the lower Great Lakes...with 
local onshore winds during Sunday. 


Outlook... 
Sunday through Monday...VFR. 
Tuesday and Wednesday...VFR/MVFR in showers and thunderstorms. 
Thursday...VFR. 


&& 


Marine... 
high pressure will remain ridged across the Great Lakes through 
tonight...before shifting off the Atlantic coast Sunday and Monday. 
This will result in good boating conditions through Monday. The next 
threat of thunderstorms will likely hold off until Tuesday and 
Wednesday...when a cold front is forecast to slowly approach and 
cross the region from northwest to southeast. 


In terms of the wind forecast for the rest of the weekend...locally 
onshore winds near the lakeshores this afternoon will tend light and 
variable tonight...then weak southeasterlies will develop Sunday 
with the flow turning locally onshore again near the lakeshores. 


&& 


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


&& 


$$ 


Synopsis...jjr 
near term...sfm 
short term...jjr 
long term...jjr 
aviation...sfm 
marine...jjr 

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