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Area forecast discussion 
National Weather Service New York New York 
1023 PM EDT Friday Mar 19 2010 


Synopsis... 
weak high pressure will move slowly offshore through Saturday. A 
weak cold front will move southeast of the area Saturday night. A 
large area of low pressure will move slowly northeast and pass 
southeast of Long Island on Wednesday. 


&& 


Near term /until 6 am Saturday morning/... 
with clear skies...diminishing winds and loss of diurnal 
heating...temperatures will continue to fall through the 50s this evening 
before bottoming out in the upper 40s to around 50 across NYC and 
in the upper 30s to lower 40s elsewhere. Favored radiational 
cooling spots will drop into the lower to middle 30s. 


&& 


Short term /6 am Saturday morning through Monday/... 
for Saturday...an unusually warm SW wind flow will continue ahead of 
an approaching cold front as thin scattered to broken cirrus clouds advect 
NE across the region. Day time temperatures will once again 
average nearly 20 degrees above normal. Although record high 
temperatures are higher for Saturday than they were for 
today...record high temperatures will likely once again be set at 
Islip...JFK and Bridgeport airports. LaGuardia high temperature record of 
71 degrees will also be approached. Followed NAM MOS guidance. 


Starting Saturday night...winds will shift to the NE following the 
passage of a cold front as weak high pressure tries building south 
across New England. With increasing SW winds aloft...an over 
running pattern develops causing clouds to thicken along with a 
chance of sprinkles. 


Sunday into early Monday...an over running pattern continues 
causing mostly cloudy skies along with sprinkles and eventually 
areas of light rain with a light onshore wind flow from east to S. 


Late Monday...a large cutoff low pressure system in the atmosphere will 
cause a surface low to move slowly toward the middle Atlantic coast. Rain 
will become likely late in the day as east winds slowly increase. 


&& 


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 /03z Saturday through Wednesday/... 
VFR through the taf period with sky clear-sct250 skies. 


Generally light and variable winds through the overnight...then west 
winds increase to 5-10 knots late Sat morning. Sea breezes will once 
again impact coastal terminals Sat afternoon...turning winds S-SW 
at 10-15 knots. Winds diminish Sat evening. 


Outlook 00z Saturday through Wednesday... 
Sat night...VFR. 
Sun...VFR with increasing middle-deck and easterly winds. 
Sun night-Tue...sub-VFR likely. 
Tuesday night...improving conditions. 
Wednesday...VFR. Gusty northwest winds possible. 


&& 


Marine... 
tranquil weather conditions are forecast through this weekend. 


As a large area of low pressure moves slowly NE toward the middle 
Atlantic coast on Monday...east winds will gradually increase to 15 
to 20 knots as seas gradually build to 3 to 5 feet. 


For Monday night through Wednesday...although winds should remain below 
Small Craft Advisory/Small Craft Advisory levels...they should be strong enough to bring 
seas on the coastal ocean waters to Small Craft Advisory levels. Seas are forecast 
to slowly subside below Small Craft Advisory levels later Wednesday. 


&& 


Hydrology... 
dry weather is forecast through Saturday. Sprinkles and areas of 
light rain are forecast to produce less than 0.10 inches of rain 
late Saturday night through early Monday. 


Late Monday through late Tuesday...a widespread significant 
rainfall is possible with amounts ranging from 1 to 2 inches. 


&& 


Climate... 
record highs were set at Kennedy...LaGuardia...Islip and Bridgeport 
airports today. 


Here are selected record high temperatures for Saturday March 20th 


Islip...56 degrees in 1991 
Kennedy Airport...62 degrees in 1979 
Bridgeport Airport...65 degrees in 1959 
LaGuardia Airport...71 degrees in 1959 


&& 


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


&& 


$$ 
Synopsis...gc 
near term...gc 
short term...gc 
long term...pfm 
aviation...mps 
marine...gc/pfm 
hydrology...gc 
climate...