920 
fxus61 kokx 202336 
afdokx 


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


Synopsis... 
weak high pressure will move slowly offshore today. A weak cold 
front drop down from the north and approach the area. It will 
slowly move through the region tonight and become nearly 
stationary over the region on Sunday. A large area of low pressure 
over the Southern Plains will slowly move northeast through early 
next week and pass southeast of Long Island Monday night and 
Tuesday. 


&& 


Near term /until 6 am Sunday morning/... 
a weak cold front from the north will move across the area tonight 
and will bring just an increase in cirrus. This will mitigate 
radiational cooling later tonight. Colder than normal spots in 
outlying areas will cool off first this evening as winds become 
light before cloud coverage increases. 


&& 


Short term /6 am Sunday morning through Tuesday/... 
the weak cold front will move through by Sunday morning and will 
stall just south of the area. High pressure building into northern 
New England will allow for winds to become more easterly and 
increase the moisture in the lower levels. More clouds will be 
developing with this increase in moisture beneath an inversion. 
The easterly flow will allow for a greater influence of the cooler 
surrounding waters and lower maximum temperatures can be expected. 


The stalled front will start to lift north of the area with winds 
turning more southerly for Sunday night. Clouds will continue to 
increase with not as cold min temperatures. Most rainfall indicated by 
models for Sunday will be displaced north of the local region with 
just a slight chance of some light rain for northern tier of the 
County Warning Area. Rain chances increase late Sunday night into Monday. 


For Monday...the closed upper level low will be moving from the 
southeast towards the middle-Atlantic with warm air advection 
increasing aloft. Flow aloft as such with be turning more 
southwesterly. This will bring additional moisture into the 
atmosphere with layer precipitable waters exceeding 1 inch by 
Monday afternoon. Isoentropic lifting will be getting more 
efficient by this time as well with rain developing from west to 
east. 


The majority of the rain will fall Monday night into Tuesday 
morning as the upper level low and surface low move into the 
coastal plain of the northeast. Rainfall could be heavy at times 
with higher Omega and vorticity moving in downstream of the low 
pressure system. 


&& 


Long term /Tuesday night through Saturday/... 
light precipitation should continue into Tuesday night as the low moves east of 
the area. Temperatures could cool down enough via northerly flow in its 
wake to allow a change back to wet snow in the higher elevations 
north/west of NYC before precipitation ends. 


Weather will then be generally quiet Wednesday into Thursday night...with only 
slight chance pop Wednesday night as a weakening cold front moves 
through...followed by high pressure of Pacific origin...with temperatures a 
few degrees above normal. 


A cold front will move through during Friday morning...while a weak 
southern stream low moves through the Ohio/Tennessee valleys toward 
the southern middle Atlantic coast. The area will be close to the 
northern fringe of this system...with chance pop Friday afternoon into 
Sat. With the new air mass being of Canadian origin...precipitation 
beginning as rain could change briefly to snow inland and a 
rain/snow mix in coastal sections outside of NYC late Friday 
night-early Sat morning. 


&& 


Aviation /00z Sunday through Thursday/... 
VFR ceilings/visibilities through the taf period. 


S-SW winds will gradually diminish to 5-10 knots over the next hour 
or so...then will become light and variable between 03-05z. East 
winds increase to 5-10 knots late Sun morning...then will turn S in 
the afternoon. 


Broken cirrus at 25 kft through the overnight...then a scattered middle deck 
will overspread the region Sun afternoon. 


Kjfk afternoon hourly wind forecast in support of runway construction 
all wind directions are true...add 13 degrees for magnetic 


20/22z 19018kt 
20/23z 20019kt 
21/00z 21013kt 
21/01z 22008kt 
21/02z 22007kt 


Outlook 00z Monday through Thursday... 
Sun night...VFR...MVFR possibly developing after 06z. 
Mon-Tue...sub-VFR likely. 
Tuesday night...improving conditions with gusty northwest winds. 
Wednesday...VFR ceilings with gusty northwest winds. 
Thursday...VFR. 


&& 


Marine... 
a weak front moves into the waters from the north tonight. 
Tranquil weather conditions are forecast through Sunday with seas 
remaining mostly below 3 feet on the ocean and 1 foot or less on 
the sound. 


For Monday and Tuesday...an area of low pressure will move slowly 
northeast toward the waters...resulting in increasing easterly 
winds. The low passes just south...then east later Tuesday and 
Wednesday. Winds and seas during the timeframe look to stay below 
Small Craft Advisory levels. 


Small Craft Advisory conditions should last on the ocean Tuesday night-Wednesday 
via the combo of north-northwest flow on the back side of the departing low 
and leftover swells...then quiet conditions are expected from Wednesday 
night-Thursday night. 


&& 


Hydrology... 
no significant precipitation is expected through Sunday. 


A widespread rainfall is possible Monday through Tuesday with 
amounts ranging from 1 to 2 inches. Minor urban flooding is 
possible...but more importantly...rivers and streams are running high 
across NE New Jersey and the lower Hudson Valley. Runoff from this storm 
could cause some of them to exceed bank full. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...none. 


&& 


$$ 
Synopsis...jm 
near term...jm 
short term...jm 
long term...bg 
aviation...mps 
marine...bg/jm 
hydrology...jm 
climate...