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fxus61 kaly 211555 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
1055 am EST Sat Nov 21 2009 


Synopsis... 
a large ridge of high pressure will build into New York 
and New England through Sunday and then lift northeast into the 
Canadian Maritimes on Monday. A low pressure system will then start 
to lift northeast from the Carolina coast Monday morning...and pass 
southeast of Long Island Tuesday morning...bringing unsettled 
weather to much of our region starting late Monday or Monday night. 


&& 


Near term /until 6 PM this evening/... 
clouds continue to spread across the region as lake effect 
moisture gets trapped beneath a boundary layer inversion. Areas 
east of the southern Green Mountains and Berkshires...where some 
downslope is occurring...are remaining partly to mostly sunny. 
Increasing sky cover for many areas this afternoon...but some 
hints in latest guidance that some areas may see the clouds break 
up to some degree. So...going mostly cloudy in many areas. Based 
on current temperatures and area 12z soundings...current maximum 
temperatures look in The Ball park. Everything else untouched. 


Previous afd below... 
clouds will slowly shrink across forecast area this 
morning as strato cumulus associated with upper level trough slide 
through forecast area. Lake response has been weak at best and with airmass 
not being very cold expect that lake induced clouds will only 
linger across portions of western Adirondacks and Mohawk Valley 
into early this afternoon and then start to dissipate. Will keep 
forecast dry today and have temperatures in most areas a few degrees 
below yesterday with highs generally in the middle 40s to middle 50s. 


&& 


Short term /6 PM this evening through Monday/... 
ridge of high pressure will be centered over forecast area late tonight into 
early Sunday and then start to lift northeast into Canada. This 
will result in mainly clear skies with seasonable temperatures tonight 
with lows in the middle 20s to middle 30s. 


On Sunday expect that temperatures maybe a few degrees cooler in the 
valleys than today as despite nearly full sun...orientation of 
high will result in a weak low level easterly flow and mixing will 
be poor only up to 925 mb. Highs on Sunday in the upper 40s to 
lower 50s. 


On Sunday night expect mainly clear skies in the evening and then 
partly cloudy conditions late as high clouds start to lift 
northward ahead of next system. Lows should be similar to Saturday 
night in the middle 20s to lower 30s. 


Monday looks to be the transition day with uncertainty still on 
exact track and orientation of precipitation shield...Gem appears to be 
the fastest and wettest with NAM not far behind as both have 
leading edge of precipitation shield at least north of i90 before 00z Tuesday and 
quantitative precipitation forecast amounts of a tenth to a quarter of an inch across forecast area. While GFS 
and European model (ecmwf) significantly slower with only light rain and a few 
hundredths of an inch of quantitative precipitation forecast into southeast third of forecast area before 00z Tuesday. 
For now will keep forecast dry with increasing clouds on Monday 
morning and then have slight chance to chance probability of precipitation south of i90 
Monday afternoon. High temperatures on Monday expected to be in the middle 
to upper 40s. 


&& 


Long term /Monday night through Friday/... 
Monday nt-Tue...still quite a bit of uncertainty regarding next 
system...currently developing along the western Gulf Coast. The 
general trend in the models over the last 24 hours has been 
weaker...and further S/east with the track. The 00z/21 Gem is most 
aggressive with this feature...tracking it off the New England 
coast...but still far enough west to bring at least some light rain 
to the S/east half of region. The 00z/21 GFS is a bit further 
S/E...while the 00z/21 European model (ecmwf) and at least half of the mrefs keep 
most precipitation out of our region...just clipping far southeast areas late Monday 
nt into early Tuesday. Based on this lingering uncertainty...have 
indicated only slight chance to low chance probability of precipitation for rain across southern 
half of region...while keeping northern areas dry. As for 
temperatures...generally followed close to gmos...with mins mainly in the 
30s...and Tuesday maxes mainly in the upper 40s to lower 50s. Should the 
clouds/precipitation extend further N/W...even cooler maxes are possible. 


Tuesday nt-Wed...will indicate dry conditions during this period...as 
most models hint at shortwave ridging building into the region. 
However...by late Wednesday...energy and warm advection approaching from 
the west may lead to some rain by late Wednesday. Thus...have indicated some 
slight chance to low chance probability of precipitation across SW areas for late Wednesday. 
Otherwise...expect maximum temperatures to range from the middle 40s across far 
northern areas...to the Lower/Middle 50s across central and southern 
areas...with overnight mins Tuesday nt mainly in the middle/upper 30s. 


Wednesday nt-Fri...models hint at additional precipitation during this 
period...although differ on the exact triggering mechanisms. The 
00z/GFS hints at a faster wave moving through late Wednesday into Wednesday nt 
with rain...while most mref members...and the European model (ecmwf) depict a 
slightly slower upper level system developing across the Great 
Lakes...while another surface low develops along the southeast coast and tracks 
north-northeast. At the very least...will indicate chance probability of precipitation during this period 
for rain...although some wet snow could be mixed in across higher 
elevations early Thursday. Then...as middle/upper level continue to 
cool...we expect any rain to gradually mix with/change to snow 
across higher elevations by late Thursday...and perhaps within valleys by 
Thursday nt or early Friday. Whether this precipitation is widespread and 
steady...or more scattered and showery is still uncertain...but 
there is at least some possibility for portions of the region to 
receive measurable snow sometime during this period. For 
temperatures...expect mins Wednesday nt to mainly be in the 30s...with Thursday maxes 
mainly in the 30s for higher elevations...and 40s for valleys. For 
Thursday nt...expect mins to fall into the 20s for higher 
elevations...and Lower/Middle 30s for the valleys...with Friday maxes 
ranging from the Lower/Middle 30s across higher elevations...to the 
upper 30s/lower 40s within the valleys. It may also become quite 
windy by Friday...depending on the evolution and track of any surface low 
passing to our east or NE. 


&& 


Aviation /16z Saturday through Wednesday/... 
high pressure will build east across the region Saturday through 
Sunday. 


Today...MVFR level clouds have developed at kgfl and kalb early this 
morning...and will likely continue through at least 15z...before 
rising to VFR levels. However...there is some possibility of MVFR 
ceilings persisting even longer. At kpou...expect VFR conditions through 
at least early tonight. 


Tonight...confidence decreasing on whether additional low clouds 
redevelop later tonight...or skies remain clear with patchy ground 
fog development. Latest model guidance hints at possible MVFR/IFR 
ceilings developing at kgfl and kalb after 06z/sun. At this time...due 
to lingering uncertainty...we have indicated few-scattered clouds below 
1000 feet above ground level at kgfl and kalb after 08z/sun...but should moistening 
trends continue in model guidance...we may need to consider some IFR 
ceilings later tonight at these terminals. At kpou...conditions should 
remain VFR...with perhaps some MVFR visibilities developing late due to 
patchy ground fog. 


Winds will remain from the west to northwest at 5-10 knots today...becoming 
light/variable tonight. Some gustiness is possible through Sat 
morning...especially at kalb...possibly reaching 15-20 knots. In addition...at 
kgfl...some variations in wind direction is possible this afternoon 
due to localized topographical effects. 


Outlook... 
sun...VFR...no sig weather. 
Mon-Tue...VFR-MVFR...chc of rain. 
Wednesday...VFR...chc of showers. 


&& 


Hydrology... 
most rivers have crested and are starting to recede or will crest 
in the next several hours. Rises from the rain that fell Thursday 
night into Friday morning were generally 1 to 2 feet. As high 
pressure continues to build into the region over the 
weekend...water levels will continue to recede in most areas 
through at least Monday. The next chance for rain will be late 
Monday into Tuesday morning...but allot of uncertainty exists at 
this time with storm track and quantitative precipitation forecast amounts. 


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...NAS 
near term...NAS 

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