Weather

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Area forecast discussion 
National Weather Service Upton New York 
405 PM EDT Sat Oct 11 2008 


Synopsis... 
high pressure will build over the northeast this weekend. A back 
door cold front will then move through Monday...and then lift back 
north of the area as a warm front late Monday night into Tuesday 
morning. A series of cold fronts will move across during the middle 
week period...with unsettled weather possibly continuing into 
the weekend. 


&& 


Near term /until 6 am Sunday morning/... 
looking at high pressure and mainly clear skies over the area 
tonight...with just a few wisps of cirrus drifting across from the lower 
Great Lakes. Low level thickness forecasts indicate not too much change 
in air mass...so would expect lows only a touch warmer than those of 
last night...with 50-55 in NYC and the immediate suburbs...and 40s 
most elsewhere...with upper 30s in western Orange County and the 
coldest spots of the Long Island Pine barrens. 


&& 


Short term /6 am Sunday morning through Tuesday/... 
fine Fall weather should continue through much if not all the period. 
The big picture shows an amplifying upper level ridge over most of 
the eastern half of the nation...with a deep cutoff low over the 
west shearing out piecemeal early next week...and a series of 
shortwaves spilling over the ridge into northern New England and the 
Canadian Maritimes. 


The first of these. Shortwaves...now entering northern Maine...will 
help drive a lobe of surface high pressure southward across the area 
on Sunday via middle level confluence in its wake. This wave will dig 
into the base of an already amplifying long wave trough southeast of Nova 
Scotia...enabling a second shortwave still near Hudson Bay to dig southeast 
and send a back door cold front through the area on Monday. 
Temperatures should warm up during the period...with Lower/Middle 70s in most 
places except far eastern CT/Long Island on Sunday...and then a few 
degrees warmer just ahead of the back door front on Monday...with 
lower 80s in northeast New Jersey and 70s elsewhere. 


It now appears that the back door front will lift quickly northeast 
late Monday night into early Tuesday morning...but until it does... 
relatively moist low level onshore flow beneath a shallow frontal 
inversion should lead to development of low stratus and fog late Monday 
night into Tuesday morning across most of Long Island and southern CT. 
Return of SW flow thereafter could lead to another very mild day on 
Tuesday...with temperatures similar to if not warmer than those of Monday...but 
this will ultimately depend on amount of high/middle level clouds 
spilling over the upper ridge to the west ahead of an approaching 
cold front. Think GFS may be too fast in this regard...and have 
leaned toward more afternoon sunshine and 
warmer temperatures. 


&& 


Long term /Tuesday night through Saturday/... 
a somewhat unsettled weather pattern looks to return by middle week 
although expect more in the way of cloud cover than precipitation until 
possibly late in the week. Although the GFS is trending towards the 
European model (ecmwf)...it continues to be the fast outlier in the medium range and 
has been discounted. Generally followed HPC guidance which is 
comprised of the 00z European model (ecmwf) and ecwmf ens mean. 


A cold front associated with a closed low pressure system moving 
across Hudson/James Bay and into the Labrador Sea will approach from 
the north on Wednesday. An offshore low blocking the upper pattern will 
cause this front to slowly move across the area Wednesday afternoon and 
evening. Middle level energy appears minimal...but would not be 
surprised if something was squeezed out. Another low generally 
follows the same track on Wednesday night and Thursday although upper trough 
and dynamics weaken as a large ridge over the southeast forces the upper 
flow over the northern Continental U.S. To flatten. This systems cold front is 
forecast to move across the area during the day Thursday with a return to 
fall expected behind it. A developing coastal system may affect the 
area late in the period...however the 12z European model (ecmwf) has trended further 
south. 


Temperatures will start off above normal...but return back to 
seasonable levels after the cold frontal passage on Thursday. 


&& 


Aviation /19z Saturday through Thursday/... 
unlimited ceilings/visibilities through the taf period. Seabreeze development 
evident in local radar data near JFK at this time...and has already 
developed along South Shore of CT. Do not anticipate a full 
seabreeze regime at LGA...but will more likely see erratic 
easterlies...possibly veering to as much as 140 degree. Speeds 
expected to remain 8 kts or less. 


Outlook for 18z Sunday through Wednesday...VFR with large ridge in 
control. Sub-VFR conditions are possible in fog and/or low stratus 
via an onshore flow Monday night into Tuesday morning...mainly across Long 
Island and CT terminals. A cold frontal passage is possible late 
Wednesday into Wednesday night with a chance of showers. 


... 


Taf code is changing November 5th at 00z... 


Please see... 


Http:/aviationweather.Gov/notice/taf30.Php (lower case) 


... 


&& 


Marine... 
quiet through most of the period. Only concerns at this time are possible 
reduced visibility in fog late Monday night into Tuesday morning via relatively 
moist onshore flow...and possible Small Craft Advisory conditions Thursday night on the 
eastern ocean waters...as the pressure gradient tightens in the wake 
of a cold frontal passage...and as low pressure over the western 
Atlantic intensifies. 


&& 


Hydrology... 
no significant rainfall is expected through next Sat...so rivers and 
streams should continue to slowly recede. 


&& 


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


&& 


$$ 


Synopsis/marine...Goodman/al 
near term/short term/hydrology...Goodman 
long term...Alabama 
aviation...bas 

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