081 
fxus61 kaly 210140 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
940 PM EDT Sat Mar 20 2010 


Synopsis... 
a cold front will slowly move south and stall over southeastern 
New York tonight. An area of low pressure is forecast to move 
along this boundary from the Ohio Valley Sunday night to the middle 
Atlantic coast Tuesday morning...resulting in a prolonged period 
of cooler and wet weather. 


&& 


Near term /until 6 am Sunday morning/... 
as of 930 PM...the front looks as if it lies near a bos/hfd/pou line 
and might not slip a whole lot further south. However...persistent 
cold air advection continues behind it...indicative of decent 
pressure rises. Temperatures are now in the 30s across our northwest 
areas...to near 50 near Albany...just under 60 at pou. 


Bases on hourly temperatures and upstream temperatures...have decided to lower 
temperatures 2-4 degrees across the board overnight. There are few clouds to 
impede radiational cooling as well...until one reaches north of 
kgfl. These clouds should slip south with time...but have virtually 
no precipitation in them (too thin). 


No changes to Sunday although it might be difficult for temperatures 
to respond upward with clouds in place...and a stalled out cold 
front probably remaining just to the south of Albany. Either 
way...Sunday will not be as mild as previous days. 


**********Previous near term discussion*************** 




After another unseasonably warm day...high and middle level clouds 
were over much of the region. These clouds will trap in some of 
the daytime heat...so we have bumped the lows up a few degrees for 
Sunday morning...from near 30 north to the low 40s south. 


The front passed through the region this afternoon without precipitation 
or even low clouds. The front will continue to slowly move 
southward toward the coast tonight and stall over southeastern 
New York late tonight or early Sunday. 


Have removed the overnight probability of precipitation...except left a slight chance in 
Herkimer County for the after midnight period...as current radar 
and satellite images show all precipitation well to the north and not 
likely to even reach Herkimer County until well after midnight. 


&& 


Short term /6 am Sunday morning through Tuesday night/... 
overrunning along the stalled frontal boundary will bring about 
a possibility of some showers on Sunday. It will be cloudy and 
considerably cooler. Have opted for a blend of the mav and met 
MOS for highs...upper 40s over the Adirondacks and southern 
Vermont...low and middle 50s down the Mohawk Valley and across 
the capital region...middle 50s across the Litchfield Hills and 
near 60 in the middle Hudson region of New York. This is 5 to 10 
degrees cooler than today. We will continue the chance probability of precipitation 
across most of the forecast area...with slight chances in 
the far south...and low likely probability of precipitation along our northern border. 
Interestingly enough...the NAM-12 had some Low Cape values 
extending into part of our region Sunday afternoon...however 
the GFS has none and thus am not expecting convection. 


Sunday night...low level moisture continues to increase...and 
with it the likelihood of overrunning precipitation. And it may get 
just cool enough up north for some p-type issues. The good 
news is height profiles suggest mixing and/or wet snow rather 
than freezing rain. Quantitative precipitation forecast amounts are quite light...so looking 
for less than an inch. Lows Sunday night...from near 30 north 
to the low 40s south. 


Monday...as the low continues to inch closer to the region with 
moisture feeding in from the south rain becomes more likely so 
we have gone with likely probability of precipitation. It will be cloudy and a just a 
bit cooler than Sunday. Snow and mixed precipitation will change back 
to rain shortly after daybreak. 


Monday night and Tuesday will be wet as the trough with the 
vertically stacked low moves across the Middle Atlantic States. 
It will be cold enough for some wet snow to fall across the 
Adirondacks and southern Vermont before it changes back to 
rain during the day Tuesday. Lows Monday night will range 
from the low 30s to the low 40s...with highs Tuesday from 
the upper 30s to the upper 40s. Northeast winds of 10 to 15 
miles per hour will make it feel even colder. 


We may have some flooding concerns to deal with...particularly 
across the Catskills...the Housatonic basin...and southern 
Vermont...with precipitation totals through Tuesday between 1 and 1.5 
inches...and nearly all of it coming as rain. The Housatonic 
River is still high from the heavy rain that fell last weekend. 
The ground is wet...and there are still patches of wet snow across 
the higher elevations in parts of the Berkshires. Considerable 
amounts of wet snow remain in southern Vermont and the Catskills 
which has kept stream flows high. Therefore heavy rain in these 
areas could bring streams and rivers over their banks. 


At this point...it doesn't look to be cold enough for a long 
enough time for winter weather headlines. But should more of 
the cold air to the north be brought into play...we could end 
up with heavier snow up north. 


&& 


Long term /Wednesday through Saturday/... 
Tuesday night...closed low pressure system off the New Jersey coast will 
filter colder air into the forecast area. Models show good agreement for 
this system to track northeastward toward the Canadian Maritimes. 
Lingering precipitation will affect the area for Wednesday night. This 
will be a combination of the departing storm...followed by another 
developing low pressure system from central Canada. From this 
point on...models disagreeing on next system/S development and 
track. Have put low chance probability of precipitation in nwern zones to indicate GFS 
stronger and more southerly track of second low. Will need to keep 
an eye on development of this system. 


Third low develops in the southern US...tracking eastward late in 
the week into the weekend. Both GFS and European model (ecmwf) show high pressure 
building in over central Canada...extending into the Great Lakes 
region. This high pressure should keep precipitation to the extreme 
southern zones...as it continues to build in over the region into 
the weekend. 


Seasonable temperatures at the start of the period will become 
slightly below normal as colder air starts to filter in on Friday. 


&& 


Aviation /00z Sunday through Thursday/... 
a big temperature drop could result in the formation of fog at 
gfl...but MVFR ought to be the worst-case scenario due to 
decreasing ground moisture. Expect any br/fog not to last long as 
clouds will impede fog development...then Sunday morning...winds 
will dissipate any fog. Middle and high level clouds expected 
overnight...with VFR low level deck developing Sunday morning at 
kgfl and kalb. 


Some vcsh and -shra will affect kgfl and kalb Sunday 
morning...with chances for precipitation increasing throughout the day 
as a wave of low pressure moves along the stalled boundary to the 
south. Have included vcsh at kpou late in the day. 


Winds will continue to subside...resulting in calm to light and vrb 
conditions at all terminals overnight. Late morning...winds will 
pick up out of the southeast to southwest at 5-10kts. 


Outlook... 
Monday am...mainly VFR...chance -shras. 
Monday PM-Tue...MVFR/IFR ceilings and visibilities with periods of rain. 
Tuesday night...improving to VFR...no sig weather. 
Wed-Thu...VFR...no sig weather. 


&& 


Fire weather... 
a cold front was in the process of crossing the region through late 
Saturday. Although no rain is associated with the front (and few 
clouds initially)...this front will stall just to the south of 
Albany and play an important role in the weather for the next couple 
of days. Moisture will increase along to the north of the stationary 
front. 


A partial recovery tonight with relative humidity values 75-90 percent. A north to 
northeast wind will average 5-10 miles per hour. There is a slight chance of 
shower or two...especially from Albany northward. Any rain that 
falls would be well under a quarter of an inch. 


Sunday will be a cloudy and cooler day compared to past ones. Relative humidity 
values will drop to 35-45 percent range...around 30 across the 
Adirondacks. A northeast wind is forecast to turn to the southeast 5 
to 15 miles per hour. There will be scattered showers...especially north and 
west of Albany. Once again...any measurable rain will be well under 
a quarter of an inch. 


Our weather will become increasingly unsettled Sunday night into 
Monday with a widespread "wetting" rain (more than a quarter inch) 
likely. Actually...snow instead of rain will accumulate across 
portions of the Adirondacks. Wet weather looks to continue into 
Tuesday...drying out Wednesday. 


&& 


Hydrology... 
our very pleasant warm and dry weather is coming to an end. Cloudy 
weather returns Sunday with an increasing chance of showers as time 
GOES on. Diurnal snow melt will continue to boost stream flows in 
the Adirondacks...Catskills... Berkshires...southern Vermont...and 
other areas where snow remains. There is still 4 to 10 inches of 
water in the snowpack over areas of the Adirondacks...Catskills... 
southern Green Mountains...and Berkshires. 


A cutoff low will move into the middle Atlantic region Monday and 
Monday night. This storm has the potential to bring one to one 
and a half inches of rain to the forecast area starting Sunday 
and ending Tuesday. Most of this will occur in the form of rain 
although some wet snow may occur over the Adirondacks and the 
higher elevations of southern Vermont during the nighttime hours. 
The runoff from this rain along with melting snow...wet ground... 
and high existing flows on the Housatonic River may result in 
the possibility of streams and rivers overflowing their banks 
starting late Monday. If the possibility of flooding becomes more 
definite...a watch will be issued Sunday afternoon. 


Please refer to the winter/Spring flood outlook /albesfaly/ for 
more details on the potential for Spring flooding. 


For details on specific area rivers and lakes...including 
observed and forecast river stages and lake elevations... 
please visit the advanced hydrologic prediction service 
/ahps/ graphs on our website. 


&& 


Aly watches/warnings/advisories... 
CT...none. 
New York...none. 
Massachusetts...none. 
Vermont...none. 


&& 


$$ 
Synopsis...rck/kgs 
near term...rck 
short term...rck 
long term...kgs 
aviation...kgs 
fire weather... 
hydrology...rck 

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