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Area forecast discussion 
National Weather Service Upton New York 
517 am EST Sat Nov 22 2008 


Synopsis... 
Canadian high pressure builds in from the plains through tonight... 
then slowly sinks to the south of the region into Monday morning. 
A complex low pressure system will approach from the west on 
Monday...then slowly lift northeast across the northeastern states 
into Thursday. High pressure then builds in from Canada to close 
the work week. 


&& 


Near term /until 6 PM this evening/... 
a sharp upper level trough is beginning to exit the region today 
as surface high pressure tries to build in from the southwest. The 
pressure gradient will remain tight between this approaching high 
pressure and a strong area of low pressure moving inland over the 
Canadian maritime. Cold advection will shut off this morning...and 
then by this afternoon heights and thickness layers will begin to 
slowly rebound. This will keep US from being being colder than 
yesterday...as highs are generally expected to be right around 
Friday/S maximum temperatures. 


Lake effect activity upstream will continue to result in some 
residual clouds today. Lower levels should be dry enough for 
lingering streams to be contained from progressing past the 
Catskills. There may be a stray flurry across the higher 
elevations of western Orange County...but confidence is not high 
enough to include in forecast at this point. Elsewhere...ocean 
effect will result in additional instability clouds over the ocean 
waters. Expect precipitation to be far enough offshore to keep 
from affecting the coastal waters forecast zones. 


&& 


Short term /6 PM this evening through Monday/... 
heights rebound Saturday night and Sunday with flow aloft briefly 
becoming zonal Sunday night before the next polar jet intrusion 
into the northeast begins to take place on Monday. 


Expect dry weather with gradually warming temperatures for the 
second half of the weekend and the start of next week...especially 
as surface high pressure begins to slide to and off the 
southeastern coast. This will result in winds backing to southwest 
by Sunday evening...allowing for a warm advection pattern to set 
up. 


Expect a cold night tonight with favorable radiational cooling 
conditions once the winds drop off. This will result in 
temperatures down near the coldest levels observed to date...with 
middle 20s in and around New York City and some areas in the teens 
across interior sections and The Pine Barrens of eastern Long 
Island. Significant improvement will arrive Sunday night into 
Monday...when temperatures should average about 10 degrees warmer 
than today or tonight. However...this will still be a shade below 
climatological normal...indicating how chilly we are to start the 
weekend. 


Have slowed in the increase in clouds and delayed the onset of 
precipitation on Monday given the highly amplified flow aloft. 
This tends to favor a slower progression than the models 
depict...especially when cutoff lows are present. Would not be 
surprised to see rain hold off until around dusk Monday evening. 


&& 


Long term /Monday night through Friday/... 
a warm front associated with low pressure digging into the Great Lakes 
will lift north through the region Monday night. The low itself will 
track over western New York state...then a persistent northwest flow will 
establish itself over the region as it slowly tracks towards eastern 
Canada through the week. 


The best chances for precipitation over the area will be Monday night/early 
Tuesday as a weak secondary low develops just over the Delaware-Maryland-Virginia area 
before tracking north over the local area. Will increase probability of precipitation to 
likely over the eastern two-thirds of the County Warning Area...as that is where 
best forcing is expected. Temperature profiles could become a bit 
problematic...but much of the southern portion of the County Warning Area can expect 
rain...while inland locations will be cold enough to support snow. 
Several weak shortwaves will rotate through the base of the trough 
for the first half of the week...keeping chance probability of precipitation in the forecast. 
Unseasonably cold temperatures remain over the area as highs will generally 
be in the upper 30s to low 40s. 


&& 


Aviation /09z Saturday through Wednesday/... 
VFR...with winds the main concern. Deepening low pressure well 
east/north of the terminals will move north into the Canadian 
Maritimes today...while high pressure builds from the west. A large 
pressure gradient between the two...along with colder air moving 
into the area...will produce strong northwest winds/gusts through the taf 
period. Kewr has settled down to a direction to the left of 310... 
which will affect dual operational runway configuration into the 
morning push. 


Winds will increase during the day on Sat via mixing of higher winds 
from aloft. As the low moves well to the north late in the period... 
winds will very gradually diminish. 


Outlook for 06z sun through Wednesday...winds will continue to 
gradually diminish through sun. Sub-VFR conditions may develop late 
Monday afternoon or Monday night into Tuesday...as low pressure approaches 
from the west and then lingers nearby through Wednesday. 


&& 


Marine... 
the pressure gradient between an intensifying ocean storm moving 
into the Canadian Maritimes and inland high pressure...along with 
mixing of stronger winds from aloft...should be sufficient to 
produce frequent gale force gusts on the ocean into tonight...so 
have raised a Gale Warning for the ocean waters. Confidence level 
not as high for gales elsewhere...but will mention occasional 35-knots 
gusts for the the eastern sound/bays. 


Winds gradually diminish late tonight and turn west on sun...but Small Craft Advisory 
conditions are likely to continue on the eastern sound/bays through 
Sun afternoon or evening...and on the ocean through all of Sun 
night. The ocean waters west of Moriches Inlet could see a brief 
lull Monday morning before winds/seas once again return to Small Craft Advisory 
levels via strengthening southerly flow ahead of low pressure 
approaching from the west...with gusts just under gale force 
possible Monday evening. 


Winds turn west on Tuesday...then a persistent west-northwest flow at 15-20 knots on the 
ocean and 10-15 knots elsewhere will be in place through the period. 
Small Craft Advisory conditions are likely to continue on the ocean through the 
period...as seas build to 6-8 feet...while the sound/Harbor/bays 
experience rough/choppy conditions just below Small Craft Advisory criteria. 


&& 


Tides/coastal flooding... 
tidal departures are currently about -0.5 feet in New York Harbor and 
western Long Island Sound...and these negative departures should 
increase further with continued strong offshore flow. NGM guidance 
appears excessively low...but even the more conservative GFS 
guidance points toward potential for blowout tides on the western 
sound with the low tide after midnight tonight and again Sunday 
afternoon. Will monitor departures today to assess need for low 
water advisories during these times. 


&& 


Hydrology... 
dry through late Monday afternoon...then there is the potential 
for moderate rainfall Monday night and Tuesday...with spotty 
precipitation into the middle of next week as a slow moving storm 
system impacts the area. It is too soon due to differing model 
solutions to offer any meaningful predictions on quantitative precipitation forecast amounts. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...Small Craft Advisory until 6 am EST Sunday for anz330-335-338- 
340-345. 
Gale Warning until 6 am EST Sunday for anz350-353. 
Gale Warning until midnight EST tonight for anz355. 


&& 


$$ 

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