344 
fxus61 kokx 210526 
afdokx 


Area forecast discussion 
National Weather Service Upton New York 
1226 am EST Friday Nov 21 2008 


Synopsis... 
a large upper low will move across eastern Canada into the 
weekend...with northwest flow across the tri-state area. 
A series of weak disturbances will reinforce cold air already in 
place. A more potent storm is possible Monday and Tuesday. High 
pressure returns by midweek. 


&& 


Near term /until 6 am this morning/... 
just some minor adjustments to the sky grids. Rest of forecast on track. 


Unseasonably cool temperatures across the region under deep 
cyclonic flow aloft. St/SC layer is rather thick across much of 
the County Warning Area west of NYC...and even has a few snow flurries in it. 
These are represented in the first part of tonights forecast. 


Mins tonight should be close to last night...but in areas where 
decoupling occurs it will be a few degrees colder. Very cold 
relatively with mins running 10-15 degrees below normal. Went with 
MOS trends...but shaved a few degrees due to poor model handling 
of early season cold outbreaks. 


Clouds overspread the region toward morning as an upper trough 
with a reinforcing shot of cold air approaches. 


&& 


Short term /6 am this morning through 6 PM Saturday/... 
latest data suggests that the approaching shortwave will pass far 
enough south of the region to avoid measurable snow. A better 
possibility exists that as the amplifying trough initiates cyclogenesis 
off the middle Atlantic coast Friday...that moisture gets thrown back 
into the cold air. This would help produce a period of light snow. 


Do not expect accumulations as the snow will be light. Temperatures will 
once again be cold...with highs in the low to middle 30s away from 
the coasts...and upper 30s along the coast and around NYC. 


850 mb temperatures drop sharply Friday night into Sat as the offshore low 
intensifies... pulling in -16c air. Kept slight chance probability of precipitation across 
far northwest zones with the possibility of instability or even lake 
induces snow showers. Temperatures will be the main story with low lows 
in the upper teens to middle 20s both Friday/Sat night...and only 
rising to within a couple of degrees either side of freezing on 
Sat. 


&& 


Long term /Saturday night through Thursday/... 
high pressure in control 
for Sunday...centered over southern middle-Atlantic region. Cold air 
filtering in on northwest winds will mean below normal temperatures. This 
high pushes off the coast by Sunday night into Monday 
morning...with slight moderation in temperatures. At the same 
time...a warm front will approach from the west through Monday 
night and move south of the area by Tuesday morning. Precipitation 
may start as light snow or a mix for interior locations...but 
should change to all rain by Tuesday. A stationary front will 
linger over the tri-state through Tuesday night...then finally 
pushes north of the area by Wednesday morning. High pressure 
builds in late Wednesday...and remains over the area through 
Thursday. 


&& 


Aviation /06z Friday through Tuesday/... 
generally VFR conditions through the forecast period. Some scattered 
flurries are possible across the lower Hudson Valley late Friday 
afternoon...but too uncertain and chances too low to include at this 
time. A low will be developing off the middle Atlantic coast during the 
day Friday and tracking to the northeast Friday night. No 
precipitation is expected with the low...and ceilings and 
visibilities will remain VFR. However...if the low does track 
farther to the west...the New York City and coastal terminals may 
see some light snow with MVFR conditions. With the low deepening and 
colder air moving in behind the low...northwesterly winds increase 
and become gusty after 00z Saturday. 


Outlook for 06z Saturday through Tuesday...VFR late Friday night 
through Sunday. Sub-VFR conditions could possibly develop on Monday 
and continue into Tuesday...depending on the timing and track of the 
next frontal system. Rain and snow will be possible. 


&& 


Marine... 
forecast on track...no updates Art this time. 


Winds and waves will remain below advisory levels through Friday 
morning. Currently seeing gusts into the low 20s across ocean 
waters...but this should die down a bit within a few hours of 
sunset. 


Low pressure will develop and intensify southeast of the 40n 70w 
benchmark on Friday causing the pressure gradient to increase 
between this storm and strong Canadian high pressure over the 
Midwest. Small Craft Advisory conditions will likely develop on the ocean waters by 
late Friday afternoon. Put up Small Craft Advisory on all other waters Friday 
evening...although it should be noted that occasional gusts to 25 
kts are possible in the afternoon. 


Current model data...and climatology suggests that winds will remain 
below gale force Friday night and Sat. Nonetheless...it could be 
close. Will continue to mention it as a possibility in the severe weather potential statement...as 
the scenario looks very similar to last Tuesday/S storm...which 
just barely reached gale force gusts on the eastern sound and 
ocean waters. 


The pressure gradient starts to relax Sat night...but flags will 
likely be needed into Sun morning (for seas) until center of the 
high builds over the eastern Seaboard. 


&& 


Hydrology... 
no significant precipitation through early next week. An oceanic 
storm may bring significant precipitation to the area Tuesday. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EST 
Saturday for anz330-335-338-340-345. 
Small Craft Advisory from 1 PM this afternoon to 6 PM EST 
Saturday for anz350-353-355. 


&& 


$$