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fxus61 kokx 172201 
afdokx 


Area forecast discussion 
National Weather Service New York New York 
601 PM EDT Wednesday Mar 17 2010 


Synopsis... 
weak high pressure will remain across the area into this weekend. 
A series of cold fronts will approach the region from the 
north...one Thursday night and another Friday night...but only 
briefly before lifting back to the north. A strong cold front then 
approaches late Sunday...crossing the area Monday. High pressure 
will follow. 


&& 


Near term /until 6 am Thursday morning/... 
west/northwest flow tonight...with clear skies and diminishing winds 
anticipated once again. 


Temperatures will fall into the 40s...with 30s across the interior/Pine 
barrens. 


&& 


Short term /6 am Thursday morning through Saturday/... 
northern stream trough will give way to height rises by Saturday as 
southern stream trough departs to our south and east. 


Dry and mild weather will prevail through the period...with daytime 
highs generally in the 60s away from the immediate coast. In 
fact...some locations to the northwest of NYC may come close or touch 70. 
Coastal locations will be influenced by the cold water temperatures 
keeping highs 55-60. Generally went above MOS where appropriate. 


At night...followed MOS blend...with a slow moderating trend evident 
in the MOS through the period. 


&& 


Long term /Saturday night through Wednesday/... 
main issue with the extended is the timing of an upper level trough 
which will draw a cold front through the region. 


12z GFS and 00z European model (ecmwf) show distinctly different solutions regarding 
the trough. GFS is more progressive with the northern stream and 
brings precipitation into the forecast area Sunday. In the 
European model (ecmwf)...the northern stream trough is slowed by the development of a 
closed 500 millibar low which develops over Texas due to the effects 
of convection. Noting the time of year...the convective solutions 
seems reasonable...so the official forecast slows the trough and 
associated cold front with lower chances of rain for Sunday and 
warmer temperatures. Temperatures were trended towards the high end 
GFS ensemble guidance. 


This system could produce isolated thunderstorms. Surface based 
chances appear to be limited to the western interior zones. 
Elsewhere...onshore southerly flow over the cold waters should 
result in a stable boundary layer. Elevated thunder possible all 
areas depending on the strength of the low level jet. This will 
enhance rainfall with locally heavy rain possible as precipitable 
water increases to close to one inch. 


Have not yet included thunderstorms in the forecast until the timing 
and evolution of the system becomes a bit clearer. 


A much colder airmass filters in behind the front for Tuesday and 
Wednesday with dry weather on northwest flow aloft. Breezy to windy 
until about 12 to 24 hours after the frontal passage. 


&& 


Aviation /22z Wednesday through Monday/... 
VFR. Sea breeze was sitting on the Grand Central Pkwy...but took 
off to the north at 21z. Winds at klga have shifted to between 180 
and 200 degrees per 22z ob and itws winds. Winds have also shifted 
to the S/southeast in Jersey City and may make it into kewr between 2230z 
and 23z. Wind speeds will likely be around 10 knots during the 
initial push through...but this should only last between 30 and 60 
minutes then fall to between 5 and 8 knots. Along the CT coast...NE 
flow is pushing the sea breeze back towards the coast and kbdr may 
shift back to the west/northwest by 23z. 


Winds lighten overnight and become more westerly...eventually 
becoming variable in direction. 


Outlook 18z Thursday through Monday... 


Thursday-Thursday night...VFR with gusty west to west-southwest winds in afternoon. 


Friday-Sun afternoon...VFR with afternoon sea breezes. 


Sun night-Mon...sub-VFR likely with gusty winds. Low level wind shear possible 
for Sun night. 


&& 


Marine... 
winds expected to remain below Small Craft Advisory thresholds through Saturday. East 
swell continues across ocean waters...with 5 to 7 foot seas 
observed. This in line or just under wave watch iii forecast...and 
seas will subside tonight into Thursday morning. Will continue with 
Small Craft Advisory for hazardous seas headline for tonight. Confidence still low on 
how long 5 foot seas in east swell continue. 5 foot seas in swell could 
very well linger into Thursday morning...but will keep headline as 
is for now given uncertainty. 


Fairly tranquil conditions with regard to winds and seas into 
Saturday...then southern flow picks up later Saturday as pressure 
gradient begins to tighten. 


A cold front will approach the waters Sunday night into Monday. 
Southerly flow ahead of the front Saturday night and Sunday. Dropped 
wave watch down a foot to account for the southerly flow. A brief 
period of Small Craft Advisory winds possible immediately ahead of the front...then 
west winds reach Small Craft Advisory levels behind the front with a slight chance 
for a brief period of gales...mainly on the ocean. Northwest flow 
may result in Small Craft Advisory conditions on Tuesday. 


&& 


Hydrology... 
dry into the weekend. Next significant rain event possible late this 
weekend and early next week with the passage of a strong cold front. 
This will indeed need to be closely watched due to the High River 
and stream levels across southeast New York and northern New Jersey. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...Small Craft Advisory for hazardous seas until 6 am EDT 
Thursday for anz350-353-355. 


&& 


$$