Weather

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Area forecast discussion 
National Weather Service Buffalo New York 
638 am EDT sun Sep 7 2008 


Synopsis... 
an upper level disturbance will bring a chance for a few showers 
today...then high pressure brings dry conditions tonight and 
Monday. A cold front approaching from the central Great Lakes will 
bring a better chance for showers and thunderstorms on Tuesday with 
much cooler temperatures for midweek. 


&& 


Near term /through tonight/... 
have made a rather aggressive update to the early morning package by 
raising the chance probability of precipitation across the Niagara Frontier to likely. Probability of precipitation for 
parts of the western southern tier have been raised from 40 to 50. See 
below for details... 


Synoptically...weak surface based ridging over the forecast area this 
morning will give way to a passing shortwave this afternoon and 
evening. The shortwave will be reflected as an inverted surface 
trough as it moves across through. This will lead to a few light 
showers later today...with the highest chance for any precipitation coming 
near Lake Erie and particularly over the iag Frontier. 


While today will start out with a fair amount of sun...Alto-cu will 
be quick to advect across the region from the middle west. These clouds 
will increase from west to east from middle morning through midday... 
with most sites having cloudy skies for the afternoon. These clouds 
will be associated with a shortwave that was tracking east from 
southern Michigan at daybreak. This feature will Cross Lake Erie 
late this morning before heading across southern Ontario during the 
afternoon. 


Low level lift generated from the feature will be minimal...as will 
be the lift added from a weakly coupled 300 mb jet found over the 
eastern Great Lakes. Even so...Doppler radar composites from the middle 
west show a slug of showers moving in our direction. These showers 
were vastly underdone by both the 00z and 06z operational GFS and 
NAM model runs. 


The newer model runs however do finally 'spin up' some fairly decent 
precipitation for the far western counties for the afternoon. This includes 
the sref...which is more impressed with quantitative precipitation forecast at this point. The 
majority of the sref ensembles have now come into line with 
depicting activity over the iag Frontier. The bulk of any showers 
should hold off until after 18z...and then lift into southern Canada by 
nightfall. 


For tonight...a surface ridge will move across the Ohio Valley and 
lwoer Great Lakes in the wake of the exiting shortwave. This should 
allow for partial clearing...especially over the western counties. 


While most areas will have dry weather tonight...800 mb temperatures of 8c may 
be cool enough to generate some nuisance lake effect rain showers 
east of Lake Ontario. Lake Delta t's will range from 13 to 14...with a 
fairly low sheared environment aimed at the Tug Hill. Will carry chance 
probability of precipitation for this potential. 


&& 


Short term /Monday through Tuesday night/... 
the active portion of the upper jet will move to the north of the 
forecast area on Monday with party sunny skies. It will be rather 
breezy as the ill defined frontal boundary will be just to the north 
and the pressure gradient will still be tight enough to support 
afternoon winds in the 15 to 20 miles per hour range. The next system will be 
taking form over the Midwest as a deeper trough digs across the 
upper plains to the Middle Lakes by Monday evening. This will develop a 
surface low over Southern Lake Michigan by 00z Tuesday...and move it 
to near the Ottawa river by 12z Tuesday. A low level jet will form 
along the associated cold front and 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 keep overnight 
temperatures higher than guidance...while showing increasing temperatures 
after midnight. 


Expect showers and thunderstorms on Tuesday as the cold front 
advances across western and central New York during the afternoon 
and interacts with moist and unstable air in the boundary layer. 
Additional lift associated with a vigorous upper level trough 
could set the stage for some active convection...even without the 
additional warmth from 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 Tuesday night. The 
corresponding surface temperatures will cool into the 40s. 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 not 
enough to prevent a rather chilly night with temperatures generally 
in the 40s and even to the upper 30s over the southern tier. 


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 over the very western edge of the forecast area. The increase 
in cloud cover and increasing southerly winds will also keeps 
overnight lows milder than the previous two nights. 


Showers will become more widespread Friday as the cold front stalls 
and becomes a stationary front...then another round of rain is 
possible on Saturday as moisture increases from the south and 
intercepts the stationary front. 


&& 


Aviation /12z Sunday through Thursday/... 
while VFR conditions were found across much of western New York at 
06z...low clouds and patchy fog are likely to develop through the 
early morning hours. This should lead to a few hours of IFR ceilings for 
the few hours surrounding sunrise. 


Conditions will then rapidly improve to VFR once again soon after 
daybreak...although clouds (generally Alto-cu) will be on the 
increase from west to east as the late morning and midday progress. 
There could even be a few light showers this afternoon and 
evening...but conditions should generally remain VFR. 


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


&& 


Marine... 
circulation around the western edge of the rapidly retreating 
remains of Hanna will produce northerly winds across the lake early 
today. High pressure ridging north from the Ohio Valley will set up 
westerly winds on the lakes later today through Monday with no 
significant waves expected. Increasing southwest winds ahead of an 
approaching cold front may generate Small Craft Advisory conditions 
on Tuesday. Much colder air across Lake Ontario after the cold front 
passes Tuesday afternoon may produce winds near 30 knots with higher 
gusts. 


&& 


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


&& 


$$ 


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

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