125 
fxus61 kokx 201754 
afdokx 


Area forecast discussion 
National Weather Service New York New York 
154 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 PM this evening/... 
another unseasonably warm day across the area with just some thin high 
clouds around. 12z okx sounding indicates mixing to near 800 hpa 
with temperatures in lower boundary layer about 2 degrees warmer 
than yesterday. In addition...nearly full sunshine is expected today 
and morning temperatures are running at least several degrees 
warmer than yesterday. Therefore...maximum temperatures were increased by 
several degrees across the area yielding highs approximately 25 
degrees above normal. Warmer for inland areas and cooler with 
towards the coastline with sea breeze developing and advecting in 
relatively cooler temperatures over the water. 


Weak surface low moves across eastern Quebec today with its attending 
cold front approaching from the north. 


&& 


Short term /6 PM this evening through Monday/... 
high pressure builds over southern Quebec and northern New England tonight 
which will help push the front through the local area with winds 
shifting to the NE. Deeper moisture remains north of the area and 
while there could be a few sprinkles...do not expect any 
measurable precipitation so removed schc probability of precipitation from forecast through sun. 


Unclear how far south the front gets...but don't think it will 
move much until Sun night/Monday as low pressure approaches from the southeast. 
Have kept the front close to the area...with mostly cloudy 
skies...and chance probability of precipitation Monday morning...then increasing to Cat by Monday 
night with the low passing to the south. 


Temperatures sun and Monday remain above normal...but only by around 10 
degrees. 


&& 


Long term /Monday night through Friday/... 
European model (ecmwf) generally running slower than GFS in the extended. Noting that 
the GFS has generally been too progressive all winter...and that the 
12z European model (ecmwf) is a tad slower than the 00z European model (ecmwf)...opted for slower 00z 
European model (ecmwf) solution in the extended (did not quite want to go with 12z 
European model (ecmwf) at this time as it is on the slow end of all available 
solutions). However with uncertainty on whether coastal low for 
late next week ends up staying to our south or impacting the 
area...did under play 00z European model (ecmwf) slightly with that system. 


Expect moderate rain Monday night...with strong isentropic lift 
evident in all models...going with likely probability of precipitation for now...but would 
expect to be raised to categorical as time GOES on. 


With region on backside of storm Tuesday/Tuesday night opted for 
rain showers...as isentropic lift no longer the dominate lifting 
mechanism. For now European model (ecmwf) keeps colder air aloft to our north...so no 
p-type issues expected on the back end. 


Should be dry Wednesday-morning with ridging building over the 
region...with the ridge axis passing to our east by Thursday 
afternoon. Have slight chance probability of precipitation Thursday afternoon ahead of an 
advancing cold front from the northwest...then chance probability of precipitation for showers 
Thursday night/Friday as the front slowly crosses the tri-state (and 
front becomes anafrontal Friday. Not much moisture to work 
with...and bulk of forcing staying to the north...so have removed 
chance of thunder...as ingredients do not appear to be there to 
support it. 


Question then becomes how far S does high building down from the north 
get...which will determine impact of frontal low forming on front 
over the lower Tennessee River valley Friday. For now have opted for 
mostly cloudy sky conditions Friday...but could end up being a bit 
less cloudy/wet than currently forecast. 


For temperatures..with bulk of cold air forecast to stay to our 
north...and slower frontal timing in European model (ecmwf)...basically went a few 
degrees above mex guidance at day (also noting its under performance 
of late during the day)...and around a mex/mex ensemble mean blend 
at night. Basically expect temperatures above normal through 
Thursday night...then near normal on Friday. 


&& 


Aviation /18z Saturday through Thursday/... 
VFR weather conditions will persist through 18z Sunday. 


Winds...as a weak cold front moves slowly southeast toward the area...a SW 
pressure gradient between the front and a high pressure system over the southeast 
U.S. Will increase. Wind directions will mainly range from 220-240 
degrees with sustained speeds 10-15 knots. Although not included in the 
latest taf forecasts...isolated wind gusts of 15-20 knots are 
possible until sunset. 


Winds will quickly decrease after sunset and become light and 
variable between 01z and 03z at most terminals. 


The cold front is forecast to move southeast of the area between 06z and 
09z tonight. Light NE winds will develop with the approach of 
sunrise as low level instability begins to increase. 


Sunday...middle and upper level ceilings will gradually lower but remain 
VFR as low pressure begins to approach the area. Light NE winds will 
gradually become southeast and increase to around 10 knots Sunday afternoon. 


Kjfk afternoon hourly wind forecast in support of runway construction 
all wind directions are true...add 13 degrees for magnetic 
20/18z 22014kt 
20/19z 22014kt 
20/20z 22014kt 
20/21z 22014kt 
20/22z 22013kt 
20/23z 22012kt 
21/00z 22010kt 
21/01z 22008kt 
21/02z 22007kt 


Outlook 18z Sunday through Thursday... 
sun aftn-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 approaches the waters from the north today and tonight. 
Tranquil weather conditions are forecast through this weekend. 


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. As such...winds will shift to the north/northwest and 
could be quite strong. Small Craft Advisory a good possibility but cannot rule out 
gales. 


As mentioned...seas tranquil initially. Then expect seas to increase 
ahead of the storm Monday night and Tuesday in east flow. Seas 
subside somewhat behind the storm in north/northwest flow Wednesday. 
Wave watch iii captures all this and seems reasonable through the 
period. 


&& 


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. 


&& 


Climate... 
here are selected record high temperatures and forecast temperatures 
for today 


Location..................record..........forecast temperature 
Islip.....................56/1991..............74 
Kennedy Airport...........62/1979..............72 
Bridgeport Airport........65/1959..............72 
LaGuardia Airport.........71/1959..............76 
Central Park..............83/1945..............75 
Newark/Liberty Airport....85/1945..............76 


&& 


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


&& 


$$ 
Synopsis... 
near term...jm 
short term... 
long term... 
aviation...gc 
marine... 
hydrology... 
climate... 

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