203 
fxus61 kbuf 212325 
afdbuf 


Area forecast discussion 
National Weather Service Buffalo New York 
625 PM EST Sat Nov 21 2009 


Synopsis... 
high pressure extending from Quebec to the Ohio Valley will slowly 
move to the Gulf of Saint Lawrence and keep dry air over the region 
through Monday. Some limited moisture from low pressure along the 
middle Atlantic coast will spread over portions of the region Tuesday. 
A storm system moving into the central Great Lakes will bring 
unsettled weather on Wednesday. 


&& 


Near term /through Sunday/... 
300 PM update...region covered under a low stratus deck at middle 
afternoon...with some earlier sunny breaks having filled in as expected. 
Just too much low level moisture around. Satellite loop show a weak 
middle level trough moving across SW New York and this should continue to push 
east and allow for some subsidence in its wake...as evident by 
clearing over lower Michigan...too late to allow for any sunshine 
this afternoon here...but perhaps some limited clearing later this 
evening. This will be a difficult call however...and even if we do 
clear...fog is again a distinct possibility later tonight and toward 
daybreak due to relatively high dew points and experience from 
Saturday morning. So...will only slowly decrease sky grids a bit 
this evening...then add patchy fog to all areas from about midnight 
to 8-9 am Sunday. Winds will be light. 


Sunday has the potential to be a beautiful day...of which we have 
had quite a few during this unusually pleasant November. Fairly 
strong ridge of high pressure will be directly overhead...and we 
will have ridging in the middle levels as well...unlike today where 
trough was present. 925 mb temperature of +6c would support l-M 50s with a 
decent amount of sunshine...and that is the question. We will likely 
start off the day with some low cloud and/or fog...and with such 
light winds and low late November sun angle...will again have 
difficulty burning it off...but expect the moist layer to be much 
shallower than today's...so will therefore erode cloud quickly in 
the 15-18z time frame..leading to a sunny afternoon. Will go closer 
to mav maxes...mostly l-M 50s...but an earlier breakout to sunshine 
would result in even milder temperatures. Normal for Nov 22 is 45. 


&& 


Short term /Sunday night through Tuesday night/... 
an expansive area of high pressure will stretch from New Brunswick 
southwest to the upper Ohio Valley through Monday evening. Sunday 
night the high will bring mainly clear skies with some patchy fog 
across southern tier valleys. Expect lows generally from the upper 20s 
to lower 30s north country and interior sections of the southern 
tier, to middle 30s elsewhere. 


The high will bring sunny/mostly sunny skies to the region Monday. 
850 temperatures of +2 to +4c shld allow temperatures to reach the lower 50s 
across the lower elevations...a few degrees cooler across higher 
terrain. 


Monday night, will bring in a chance of showers across areas from 
the interior of the southern tier and southern and eastern Finger 
Lakes to southern portions of the Eastern Lake Ontario counties as 
Atlantic moisture works west around the north side of low pressure 
along the middle Atlantic coast. The ham keeps far western areas dry 
with high pressure from northern New England extending back west to 
the Central Lakes while the GFS tries spreading some moisture from the 
Ohio Valley associated with a middle level short wave into the far west 
portions of our County Warning Area. At this point will only go with slight chance probability of precipitation in 
the far west. 


On Tuesday, will keep slight chance probability of precipitation over the bulk of the area as 
much of our region is between the low moving off the middle Atlantic 
coast and another low moving into the central miss valley. Will keep 
chance probability of precipitation in the morning from the coastal system mainly just over Allegany 
County and southeast portions of the Eastern Lake Ontario counties. Expect 
another day with above normal temperatures with most areas reaching the lower 
50s. 


Tuesday night, low pressure is expected to move into the western 
and Central Lakes with a southerly flow of increasingly moist air 
spreading into areas from The Finger lakes west. Retreating high 
pressure from the St law valley shld keep the Eastern Lake Ontario 
region dry. The southerly flow shld keep temperatures from dropping much 
with lows in the low to middle 40s, a bit cooler across the north 
country. 


&& 


Long term /Wednesday through Saturday/... 
the now well advertised pattern change still appears on track to 
arrive for the Thanksgiving Holiday. The current pattern across the 
noam sector is more or less zonal...with transient relatively low 
amplitude troughs moving through the westerlies along and just north 
of the US/Canadian border. The gefs ensemble mean continues to 
forecast the nao index to become weakly negative by the end of the 
month...with the pna index trending positive. In the mean...this 
should yield a colder pattern for the Great Lakes and northeast for 
the last week of November into early December with a trough favored 
over the eastern Continental U.S. In such a pattern. The indicies are not 
forecast to be particularly strong however...so no dramatic pattern 
change is expected...rather a trend towards cooler and more 
seasonable temperatures. 


Continuity still looks good with chance probability of precipitation from Wednesday right 
through Saturday. A big upper trough is expected to strengthen with 
a closed upper low developing over the Great Lakes and moving to 
western New York by Friday and then moving to New England Saturday. 


Temperatures shld still be warm enough Thursday for the precipitation to be in the 
form of rain showers but then it will get colder Thursday night for 
a mix of rain and snow, changing to snow showers toward Friday 
morning. The precipitation shld be in the form of rain/snow showers Friday 
with highs only in the upper 30s to lower 40s. 


Friday night it shld get cold enough for all areas to see chance of 
snow showers with lows in the upper 20s to lower 30s. There will be a 
better chance of snow showers in northwest flow southeast of Lake Erie and Ontario. The 
northwest flow shld shld continue chance mixed precipitation into Saturday with highs 
in the upper 30s to low to middle 40s. 


&& 


Aviation /23z Saturday through Thursday/... 
dense stratus deck will linger across the region through the 
night...with some patchy dense fog again becoming possible late 
tonight as the boundary layer once again becomes more saturated 
with nocturnal cooling. Therefore...have continued to indicate 
widespread MVFR ceilings tonight...lowering to a period of LIFR 
conditions in fog overnight just about anywhere. 


During Sunday...conditions should finally improve to VFR by 
midday as the low cloudiness/fog gradually mixes out as high 
pressure provides for some good subsidence. That said...forecast 
confidence in the exact timing of this improvement is still fairly 
low. 


Outlook... 
Sunday night through Tuesday...mainly VFR. 
Wednesday...VFR with chance showers. 


&& 


Marine... 
high pressure will keep winds and waves below small craft criteria 
through Monday. 


&& 


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


&& 


$$ 


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

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)