043 
fxus61 kokx 101119 
afdokx 


Area forecast discussion 
National Weather Service New York New York 
619 am EST Wednesday Mar 10 2010 


Synopsis... 
high pressure over the region will slowly move northeast through the 
end of the week. A potent storm system over the Central Plains will 
slowly move towards the region Thursday through Sunday...then move 
east of the region early next week. High pressure builds back into 
the region on Tuesday. 


&& 


Near term /until 6 PM this evening/... 
upper level ridging and surface high pressure will provide another 
dry weather day. The approach of a warm front today will result in 
an increase in cloud cover. Winds will start off the day from the 
northeast and will gradually shift around to the east/southeast. 
Mav/met guidance numbers will very similar on daytime highs and 
followed. Highs today are expected to reach the middle to upper 50s. 
Lower 50s can be expected across Long Island and coastal locations. 


&& 


Short term /6 PM this evening through Friday/... 
high pressure and upper level ridging shift eastward tonight and 
Thursday. This will allow a slow moving low pressure system moving 
across the Central Plains to approach. Meanwhile...a warm front will 
lift north of the region overnight. 


Probability of precipitation gradually increase throughout the day on Thursday and Thursday 
night with the approach of the low and the vicinity of the frontal 
boundary. Isentropic lift will allow for the development of light 
rain or drizzle. At this time...am expecting more drizzle than light 
rain. There may be a chance of some light freezing rain/freezing 
drizzle across Orange County Thursday morning...however confidence 
is low and removed any mention of frozen precipitation from the 
forecast. This will need to be re-evaluated by the day shift. 


Likely probability of precipitation expected on Friday for much of the area as moisture 
continues to increase with the low pressure system moving into the 
Ohio Valley. The rain is expected to be mainly light in nature on 
Friday...however there may be some periods of moderate rain by 
afternoon. 


Followed a mav/met blend once again for the short term period. Highs 
on Thursday expected to climb into the middle 50s...with lower 50s 
expected across Long Island and coastal locations. Cooler conditions 
are expected on Friday with cloud cover and light rain/drizzle 
expected. Highs should only reach the upper 40s to lower 50s. 
Overnight lows fall into the 30s and 40s. 


&& 


Long term /Friday night through Tuesday/... 
moisture feed associated with an 500 mb low over the Ohio Valley will 
result in a heavy rain threat...particularly Saturday and Saturday 
night. Likely probability of precipitation Friday night through Sunday morning...with HPC 
rainfall amounts in excess of 3 inches over NYC and model quantitative precipitation forecast values 
generally in the 2 to 4 inch range. Heaviest precipitation axis shifts east 
of the area Sunday afternoon...with chance probability of precipitation persisting into 
Monday morning. 


Any lingering showers wind down on Monday as the upper low transits 
the area...finally shifting to the east on Tuesday. 


&& 


Aviation /12z Wednesday through Sunday/... 
high pressure over the area with vrb winds this morning. If there is a 
prevailing direction it will be to the NE. Winds veer to southeast around 
17-18z as the high drifts eastward. Light flow at or below 6kt tonight. Wind 
directions will have east component but vary. 


Sea breeze development possible today. Most likely spots at this time kgon 
and kjfk. Tempo included in the taf for this until confidence 
increases. If it does develop it will prevail through about 00z. 


Few-scattered cirrus this morning then middle clouds showing up on radar 
across southwestern PA time out to getting here about 17-18z. Clouds lower 
after 00z. Ceilings through 06z VFR. 


Timing differences exist amongst the models for MVFR timing after 6z 
Thursday. Leaned towards the faster onset of low clouds but limited 
ceilings to bkn035 at 13z to compensate. Future tafs will revise as 
the data improves. 


Outlook 18z Thursday through Sunday... 
Thursday afternoon...MVFR likely in -ra. Easterly flow increases. 
Thursday night-Sat night...MVFR with periods of IFR. Increasing southeast 
flow. +Ra possible Friday night through Sat night. Potential for high 
winds Sat afternoon-Sat night with sustained at or above 25kt and higher gusts. 
Sun...sub-VFR likely. 


Kjfk afternoon hourly wind forecast in support of runway construction 
all wind directions are true...add 13 degrees for magnetic 
10/19z 13006kt 
10/20z 13006kt 
10/21z 13006kt 
10/22z 13006kt 
10/23z 13005kt 
11/00z 12004kt 
11/01z 12004kt 
11/02z 10004kt 
11/03z 09004kt 


&& 


Marine... 
high pressure over the waters today will drift east over Cape Cod tonight. 
Winds generally at or below 10kt all waters...with seas 1ft or less 
sound/bays and 2ft or less ocean due to some residual swell. 


Pressure falls SW of the waters Thursday...and continues to fall until low pressure 
reaches a point S of the waters Sat night. This will set up an 
increasing pressure gradient across the waters through the period. East winds will 
steadily increase...with Small Craft Advisory conditions on the ocean by Friday morning due 
to building seas...and marginal Small Craft Advisory winds rest of the waters Friday. Winds 
will increase to Small Craft Advisory levels all waters Sat...with gales likely late 
Sat and Sat night. The prolonged east wind will result in at least 6 feet 
seas across portions of the western/central sound and higher across the east. 
Seas will build to around 20ft on the ocean. 


The low will potentially stall sun just S of the waters before being 
forced eastward out to sea by an upper level system on Monday. This will result 
in backing winds and a continued threat for gales...especially 
across the eastern waters. 


&& 


Hydrology... 
generally less than a tenth of a rain is expected through Thursday 
(wednesday being dry). Steadier rain begins to develop Thursday 
night and Friday...then could become heavy at times Friday night 
through Saturday night...with diminishing intensity and coverage 
Sunday into Monday morning as the storm pulls to the east. Generally 
expect 2-4 inches of rain from Thursday night through Monday morning 
with isolated higher amounts possible. This...coupled with snow melt 
across northwest zones...could cause flash and river flooding 
concerns...and definite minor/urban flooding problems over the 
weekend. 


&& 


Tides/coastal flooding... 
strong and persistent east winds will result in the potential for coastal 
flooding along portions of the sound and bays late Sat and Sat night. 


Across the Atlantic coast...high seas combined with the surge will 
have the potential to produce beach erosion along with coastal 
flooding. 


&& 


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


&& 


$$ 
Synopsis...British Columbia 
near term...British Columbia 
short term...British Columbia 
long term...British Columbia 
aviation...jmc 
marine...jmc 
hydrology...British Columbia 
tides/coastal flooding...jmc 

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