172 
fxus61 kokx 081629 
afdokx 


Area forecast discussion 
National Weather Service Upton New York 
1129 am EST Thursday Jan 8 2009 


Synopsis... 
low pressure continues to intensify as it tracks northeast into 
the Canadian Maritimes. High pressure passes well south of the 
region on Friday. Developing low pressure will move through the 
region Saturday and Saturday night...then high pressure returns 
for Sunday and Monday. Another low passes through the region 
Monday night and Tuesday...then a polar airmass overspreads the 
region for the middle of the week. 


&& 


Near term /until 6 PM this evening/... 
morning update to reflect a few changes. 


First change was to have a slight chance of snow showers across 
Long Island and New York City...with a chance of snow showers 
across New Jersey...lower Hudson Valley and Connecticut. 


Second change was to cancel the Wind Advisory for southern New 
Haven...Kings...Queens...Nassau and western Suffolk. Will continue 
the Wind Advisory until 4pm for eastern Suffolk and eastern 
southern Connecticut. Winds are expected to increase to 25 to 35 
miles per hour...with gusts up to 45 miles per hour as the pressure gradient increases 
with a departing low to the north. 


Otherwise...a middle-level shortwave and upper trough axis will 
rotate through the region today. Skies will generally remain 
cloudy. Highs today will be right around normal...generally in 
the middle 30s to around 40. 


&& 


Short term /6 PM this evening through Friday night/... 
upper trough eventually passes to the east later tonight and 
skies will be clearing out as high pressure builds over the southeast 
U.S. Winds winds remain gusty...generally at 10 to 15 miles per hour with 25 
miles per hour gusts. Strongest winds are expected over NYC. 


Surface ridge passes south of the area Friday and Friday night. Skies will 
be mostly sunny...and with diurnal heating and mixing...winds will 
be increasing once again to 15 to 25 miles per hour with gusts of 30 to 35 
miles per hour. 


Low pressure develops over the Midwest Friday night...and a warm front 
will be lifting north into the area after midnight. The best 
chances for radiational cooling will be during the evening...with 
clear skies and diminishing winds. With clouds increasing after 
midnight...think temperatures will hold steady...then slowly rise towards 
daybreak. Will carry slight chance probability of precipitation for the western half of 
the County Warning Area after midnight...but precipitation will be slow to make it to the 
region. 


&& 


Long term /Saturday through Wednesday/... 
unsettled weather expected on Sat as low pressure passes through the 
region. Models showing divergent solutions regarding the track of 
the next system. 00z/08 NAM has a primary low moving into western 
New York/PA by Sat afternoon...then has a secondary low developing over 
the Delaware-Maryland-Virginia Sat evening...and that low tracks through the region 
from 06z-12z sun. This is primarily a warm solution...with snow 
changing over to rain for much of the area. 00z/08 GFS keeps one 
low which passes south of Long Island Sat afternoon/evening. 
00z/08 European model (ecmwf) is similar to the NAM...only the secondary low is not 
quite as pronounced as it is on the NAM. Will go with a consensus. 
Will carry likely probability of precipitation for the region starting out with all 
snow...then will have snow changing to rain across NYC/Long 
Island. This is subject to change...as the rain/snow line could be 
shifted north or south depending on further solutions. Based on 
surface temperatures and quantitative precipitation forecast...2-4" snow is possible...but is subject to 
revisions. 


Will then keep slight chance probability of precipitation on the forecast on sun as upper 
trough swings through the region. Surface high passes south of the 
area on Monday. Arctic front then swings through the area by middle 
week. 850 mb temperatures will be plunging to -22c to -26c...resulting in 
highs in the teens and lower 20s and lows in the single digits to 
teens from Tuesday night through Wednesday night. This will represent some 
of the coldest air of the season. 


&& 


Aviation /16z Thursday through Monday/... 
VFR today. The main story is strong west winds through the day. 
Expect west winds around 240-270...as winds slowly turn to the 
west/northwest (270-300) by late afternoon and evening. Sustained 
speeds of 15 to 25 kts expected with some gusts well into the 
30s. These brisk winds continue through the afternoon...then 
diminish slightly tonight. Still expect good mixing conditions 
much of the night...with usual airports across the interior 
observing fewer gusts as the night progresses as weak and shallow 
inversion develops. 


Otherwise...upper trough will produce VFR ceilings today. Best 
chance for any isolated snow shower is kswf. 


Some clearing occurs tonight as the trough moves east. 


Outlook 12z Friday through Monday... 
VFR Friday and Friday night. On Saturday...fast moving low pressure 
may bring snow or possibly a period of mixed precipitation near the 
coast...with sub-VFR conditions. Improving ceilings/visibility Sunday as 
clipper departs...VFR probable through Monday. 


&& 


Marine... 
as low pressure deepens to the north...tight pressure gradient 
will persist through the day. Gales continue in strong westerly 
winds. 


By tonight...low pressure moves to Canadian Maritimes as ridge of 
high pressure slowly builds from the west. Pressure gradient 
remains tight tonight through Friday as winds turn to the 
northwest. Gale force winds continue for the eastern waters into 
tonight...before falling back a bit later tonight. An occasional 
gust to gale force is possible Friday all waters. 


Winds finally lighten Friday night and Saturday as the ridge of 
high pressure builds just south of the waters. The high tracks to 
the east and gives way to upstream low pressure...which will move 
over the waters Sunday morning. Brisk northwest flow will prevail 
once again behind this low Sunday night. Another high quickly 
passes by to the south Monday as next system approaches from the 
west. 


Followed wave watch iii forecast through the period...with 
harbors/sound and Bay sea forecasts in line with expected winds 
and past history with such winds. 


&& 


Hydrology... 
no significant quantitative precipitation forecast expected through Friday night. The next system 
Sat/Sat night could bring 1/2 inch liquid quantitative precipitation forecast to the area. 


&& 


Tides/coastal flooding... 
tough forecast as guidance disparities exist. Right now NGM./GFS 
guidance running too low. Overall I feel low water problems are 
possible today and tonight. Right now highest confidence across 
shallow South Shore bays and western Long Island Sound for low 
water problems. Not as confident across New York Harbor at this time. Right now 
tidal departures still running above normal. This will 
change...but not sure if it will occur with this upcoming low tide 
cycle as west winds prevail. Do have a little more time in the 
sound as low tide occurs several hours later. 


By tonight...northwest flow could very well result in widespread 
low water problems...but guidance inconclusive on forecast 
departures at this time. Will just continue low water advisory 
from previous locations one more low tide cycle...and will allow 
time to monitor trends. 


&& 


Okx watches/warnings/advisories... 
CT...Wind Advisory until 4 PM EST this afternoon for ctz011-012. 
New York...Wind Advisory until 4 PM EST this afternoon for nyz079-081. 
New Jersey...none. 
Marine...Gale Warning until 6 PM EST this evening for anz335-338-345. 
Gale Warning until midnight EST tonight for anz330-340-350-353- 
355. 
Low water advisory until 5 am EST Friday for anz335. 
Low water advisory until 3 am EST Friday for anz345. 


&& 


$$ 

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