009 
fxus61 kbuf 211313 
afdbuf 


Area forecast discussion 
National Weather Service Buffalo New York 
913 am EDT sun Mar 21 2010 


Synopsis... 
limited moisture between high pressure over Quebec and a cold front 
front that has stalled south of Pennsylvania will impact parts of 
western and north central New York state today. A more widespread 
rain will spread north across the area Monday and Tuesday as an 
low pressure moves east along the stalled front. 


&& 


Near term /through tonight/... 
at 900 am...radar shows an area of showers crossing Lake 
Ontario...headed towards the north country. There is a tight 850 
mb gradient in this region...even though the surface boundary is 
further south. Oddly...it seems older runs of the NAM/GFS had a 
better handle on this...with much of the 00z and 06 runs of the 
NAM/GFS slow in spinning this up...though they do seem to catch on 
by 18z today. Will up probability of precipitation to likely in the north country...while 
trending back probability of precipitation south of this boundary...where it appears the 
chance of measurable precipitation is minimal. 


Precipitation type is a challenge as this area enters the north 
country...with snow/sleet/rain all being precipitation types which have 
been reported upstream. 12z Buffalo sounding shows a + 4c 
wedge...however at Watertown...the sounding is forecast to be 
cooler...so could see a mixed bag given the warm layer...and a 
narrow cool layer beneath it. Could see snow/sleet/rain through 
this morning...with lingering activity changing over to rain by 
afternoon. 


Otherwise...conditions should improve from south to north today. 
Satellite shows significant breaks in clouds which will move into 
the southern tier late this morning. Will hedge a bit more 
optimistic on sky conditions...and a tad warmer south where sun is expected. 


Tonight our region will be playing the waiting game for the next 
system which will eventually bring our region some widespread rain. 
An anomalously deep (-4 Standard deviations for 500 mb hgts) upper level 
low...the same one responsible for the freak Oklahoma snowstorm on 
Saturday...will be churning over the lower Mississippi Valley while 
its surface reflection will be lifting up the Ohio Valley. 


As a result...our confluent upper level flow will gradually give 
way to a diffluent flow while low level moisture will be on the 
increase. While the bulk of tonight should be precipitation free...the 
potential for some rain will increase across the western southern tier 
and Finger Lakes region as we progress into the wee hours of Monday 
morning. Temperatures will settle to between 35 and 40 for most 
areas...so there will not be a threat for any mixed precipitation. 


&& 


Short term /Monday through Tuesday night/... 
low pressure centered over Arkansas early this Sunday morning will 
become the main weather maker for our County Warning Area during this time period. 
The low is forecast to move northeast from the Ohio Valley 
Monday...then track east across PA Monday night before reaching the 
New England coast on Tuesday. 


Rain developing ahead of this system will continue to lift slowly to 
the north on Monday and impact the entire County Warning Area by Monday evening. 
Will continue to show a gradual north to south increase in probability of precipitation as 
moisture surges ahead of the low. 


Still looks like the steadiest rain will fall Monday night into 
Tuesday morning when increasing upper level diffluence ahead of the 
deep upper level low will enhance large scale lift across New York 
state. In terms of quantitative precipitation forecast...the latest HPC guidance indicates a general 
0.50 to 0.85 inch of rain across our County Warning Area through Tuesday with the 
highest amounts concentrated over the southern tier. 


Expect the steadiest rain to taper off gradually from west to east 
Tuesday and Tuesday night as the main center of the low shifts east 
into New England. The models still suggest that temperatures aloft 
will get cold enough Tuesday night to support a mix of rain and snow 
across the north country. 


&& 


Long term /Wednesday through Saturday/... 
drier air advecting in behind the departing low will bring mainly 
dry conditions on Wednesday with above average temperatures. 


Wednesday night...the NAM suggests a weak cold front with rather 
limited moisture will push east across New York state. A weak short 
wave accompanying the front may generate enough lift to generate a 
few rain and snow showers east of Lake Ontario for part of Wednesday 
night. 


Thursday, high pressure should bring fair weather with highs in the 
middle to upper 40s. A more significant cold front is forecast to cross 
the area Thursday night with limited moisture. The latest European model (ecmwf) is 
still not quite as cold as the GFS...but any precipitation that accompanies 
the passing cold front will likely change to snow showers before 
daybreak Friday. 


On Friday, the front moves further south into Pennsylvania and 
chilly high pressure over Quebec builds south into the region. Will 
leave in slight chance probability of precipitation from The Finger lakes westward as a cold 
northerly upslope flow south of Lake Ontario may generate an 
isolated rain or snow shower. 


The high will keep dry weather over the area Saturday...but both 
Friday and Saturday will likely see below normal temperatures with 
readings struggling to get out of the 30s east of Lake Ontario. The 
rest of the area should see temperatures in the lower to middle 40s. 


&& 


Aviation /13z Sunday through Thursday/... 
an area of low clouds and showers will skirt across parts of the 
Niagara Frontier and Lake Ontario nearshore this morning...and this 
will result in a few hours of IFR ceilings for sites such as kbuf...kroc 
and especially kiag. By late this morning through...VFR conditions 
are expected region wide under an extensive Alto-cumulus deck. 


Tonight...low pressure will lift to the north across the Ohio 
Valley. This will spread increasing amounts of low level moisture 
into our region...particularly across the western southern tier 
where ceilings should deteriorate to at least MVFR levels after midnight 
for sites such as kjhw and kelz. 


Outlook... 
Monday through Monday night...MVFR/IFR with rain likely. 
Tuesday...MVFR/VFR. A chance of showers. 
Wednesday and Thursday...VFR likely. 


&& 


Marine... 
no marine flags are expected through the rest of the weekend into 
Monday as relatively weak pressure gradients will be in place across 
the lower lakes. Increasing northeast winds ahead of an approaching 
low will cause more significant waves to develop Monday night and 
Tuesday. 


&& 


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


&& 


$$ 


Synopsis...tjp 
near term...apffel/rsh 
short term...tjp 
long term...jjp/tjp 
aviation...apffel/rsh 
marine...tjp 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)