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fxus61 kokx 212341 
afdokx 


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


Synopsis... 
high pressure builds across eastern Canada...and into the 
Maritimes thorough Monday. An area of low pressure will develop 
off the southeast US coast Sunday...then move up coast 
Monday...passing south and east of Long Island through Tuesday. Weak 
high pressure builds in from the north Wednesday. Another storm 
system may impact the tri- state to close the upcoming work week. 


&& 


Near term /until 6 am Sunday morning/... 
mostly clear skies expected as winds diminish. This combination 
will result in decent if not ideal radiational cooling for at 
least a few hours tonight. Forecast lows...and dewpoints approach 
the middle 30s in spots...so early morning fog is a possibility. This 
is not in the grids at this point given that decoupling should 
only last a few hours as NE winds pick up a bit. 


Undercut MOS in general in the normally cooler spots across 
Orange/Putnam County and The Pine Barrens of Li. Persistence and 
MOS very close elsewhere. 


&& 


Short term /6 am Sunday morning through Tuesday night/... 
deep layer ridge passes north of the County Warning Area Sunday...allowing 
easterly flow on the south side to increase. All in all a decent 
day with highs near or slightly below climatological norms with 
east winds. 


Tricky temperature forecast Sunday night...as cold air damming and low 
level cold air advection continue from the north and east. There 
may again be a period of decoupling...thus forecast low temperatures are 
expected to end up close to tonight's. This period is perhaps the 
lowest confidence temperature forecast of the short term. If surface 
winds stay up...and increasing moisture from a developing surface 
low get here earlier than expected...lows will be much warmer than 
forecast. 


Model solutions still diverge on the track and intensity of a 
diffuse coastal low...but the wind fields are bit more aligned. 


Precipitation expected to hold off until Monday night...although a brief 
period of light overrunning rain possible Monday afternoon. 
Increased pop to likely for about the eastern two thirds of the 
County Warning Area Tuesday morning...but this ultimately depends on if the low 
center passes close enough to put the area in the best lift. The 
NAM continues to be the most robust in terms of quantitative precipitation forecast...but the 18z 
run has backed off from its 1 to 1.5 inch forecast earlier today. 
Light rain...primarily wrap around...possible into Tuesday night. 


Not a whole lot of temperature variation Monday night through Tuesday 
night...especially near the coast. 


&& 


Long term /Wednesday through Saturday/... 
low pressure departs the region Tuesday night with chance probability of precipitation for -ra ending. 
SW flow aloft develops Wednesday as 500 mb low drops into the Ohio Valley. 300 mb 
jet produces some lift...but forcing otherwise is weak as 
evidenced by the time heights. With marginal moisture...only light precipitation 
expected at this time. A lull settles in Wednesday night into Thursday...then the focus 
shifts to late Thursday and Friday. Another 500 mb low drops into the Ohio 
Valley with a complex reflection at the surface. Models hint at low 
pressure developing along the northern Gulf Coast and tracking northeastward off the 
Atlantic coast...with a second low developing over the eastern Great 
Lakes. Although there is a spread in the model solutions...it appears a 
shot of rain on track during the period. Main issue may turn out to 
be the wind if the 12z GFS/European model (ecmwf) solutions are close and a 980s low 
occludes over northern New England Sat morning. 


&& 


Aviation /00z Sunday through Thursday/... 
winds initially around 10 kts at a few locales in and around NYC 
metropolitan this evening. Otherwise...northwest flow under 10 knots should veer north 
overnight. Winds then turn NE with speeds increasing to around 10 
knots...higher at NYC/coastal terminals...toward or just after 
daybreak Sunday morning as high pressure over the the Ohio Valley 
builds NE into New England. Radiation fog with MVFR conditions may 
occur...although confidence in this happening is low...late 
tonight at kswf and kgon. Will have to monitor other terminals 
outside the NYC urban heat island for this possibility close 
to/just after sunrise. 


VFR through the day Sunday with NE winds 9 to 12 kts. 


Outlook 00z Monday through Thursday... 
Sunday night...VFR. 
Monday...sub-VFR possible. 
Monday night-Tue...sub-VFR likely. 
Tuesday night-Wed...becoming VFR. 
Thursday...sub-VFR possible. 


&& 


Marine... 
northerly flow becomes northeast overnight...as high pressure 
settles into eastern Canada. The pressure gradient strengthens 
through Sunday evening with lowering pressure to the south. Small 
craft conditions expected to begin on ocean waters Sunday evening. 
Expect winds to increase from south to north...and it is possible 
the the waters right along the coast of Long Island will not see 
25 kts until Monday morning. 


Small craft wind conditions...with a few gusts possibly 
approaching gale force Monday through Tuesday. 


Small Craft Advisory seas on the ocean linger Tuesday night into Wednesday...then begin to 
subside as low pressure weakens north of the coastal waters. A complex low 
pressure system will then impact the waters late Thursday into Friday. Depending 
on the exact track and intensity of the system...gales may be 
possible during the period. 


&& 


Hydrology... 
dry through Monday morning. A quarter to a half an inch of 
rainfall is possible Monday afternoon through Wednesday. More 
precipitation is expected towards the end of next week. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...Small Craft Advisory from 6 PM Sunday to 6 PM EST Monday for 
anz350-353-355. 


&& 


$$ 
Synopsis...bs 
near term...bs/pw 
short term...bs 
long term...jmc 
aviation...precipitable water 
marine...bg/jmc 
hydrology...bs