Weather

948 
fxus61 kokx 061533 
afdokx 


Area forecast discussion 
National Weather Service Upton New York 
1133 am EDT Monday Oct 6 2008 


Synopsis... 
strong high pressure will build down from Ontario through 
tonight...then move offshore Thursday. Low pressure over the 
Tennessee Valley on Thursday will move off the middle Atlantic 
coast on Friday and move towards the region for the weekend. 


&& 


Near term /until 6 PM this evening/... 
departing jet streak and 850-700 frontogenetic region allowing for 
some brief clearing early this afternoon...but 500 mb vorticity 
tracking southeast from upstate New York this afternoon will bring a return to 
partly sunny/mostly cloudy sky conditions at most locations this 
afternoon. Best forcing will be over NE portions of the County Warning Area...so 
left in chance of sprinkles over southeast CT this afternoon...otherwise 
dry. Basically followed the RUC for this update as it has best 
handle on 500 mb vorticity. 


Temperature forecast generally on track...made minor changes to 
reflect latest hourly trends. 


&& 


Short term /6 PM this evening through Thursday/... 
strong subsidence leading to clear skies by this evening. Winds 
diminish and expect most areas to decouple and go 
calm...especially interior sections. This will provide and 
excellent setup for frost. A frost advisory is up for the outer 
zones in New York/New Jersey and CT for after midnight tonight. Suffolk County 
on Long Island is questionable with how cold the Pine Barren 
region can get. However it will be a little more difficult to 
decouple here...and the area that does get frost is too small to 
warrant a frost advisory for the surrounding zone. 


Guidance temperatures look good...but favored the slightly cooler met over 
the mav. 


High pressure solidly in control with sky clear Tuesday...and maybe a 
few popcorn cumulus Wednesday. Cool temperatures with daytime highs in the 
upper 50s to middle 60s. Tuesday night may be the end of the growing 
season for most areas away from the coast with a freeze possible 
under ideal radiational cooling conditions. Lows range from low 
30s inland to upper 40s near the ocean. 


The surface high slides east off the coast and lets return flow 
and middle level moisture work in from the west Thursday...with 
slightly warmer temperatures. 


&& 


Long term /Thursday night through Sunday/... 
large differences in the medium range models for later this week. 
Both the ec and GFS have similar height fields....but the features 
in the ec are about 500 miles west of the GFS. 


Both models drive a strong Pacific jet across the northern 
US...and develop a cutoff low over the lower MS valley by Thursday 
morning. However...the GFS has a much more progressive flow and 
brings that low racing up the US East Coast Friday night on strong 
SW flow ahead of a full latitude trough over the Central Plains. 


The ec keeps this deep trough as a cutoff over the Great Basin 
right through the weekend...and the incipient cutoff over the southeast 
US. The result of all this is a completely different forecast for 
the tri state area for the Friday-Sunday period. 


Will have to monitor the progress of the Pacific jet energy to 
delineate the impact on this weekends weather. Have left chance 
probability of precipitation in the forecast due to the uncertainty at this point. 


&& 


Aviation /15z Monday through Friday/... 
VFR through the taf period. 


Winds will gradually increase today as an upper level trough 
swings through the region and surface high pressure over Canada 
builds southward into the area. Winds direction generally from 
the north/northwest with speeds between 10 and 15 knots. In 
addition...some gusty winds are anticipated. Some of the gusts 
could reach 20 knots. Any gusts are expected to be short lived and 
occur during the afternoon/early evening. 


There could be a few isolated showers today...however timing and 
locations are uncertain at this time and will not mention in the 
tafs. Any showers that develop should not reduce conditions below 
VFR. 


Outlook for 06z Tuesday through Friday...VFR through Wednesday night 
with high pressure in control. Next front approaches Thursday...and 
gets hung up along the East Coast Friday. Sub VFR possible late 
Thursday and Friday. 


&& 


Marine... 
minor changes made...mainly to precipitation forecast. Previous 
discussion follows... 


An upper level shortwave will push across the area waters late 
this afternoon/evening. Meanwhile...high pressure will build in at 
the surface. As a result...winds will increase to around 
15kt...with gusts between 20 and 25 knots this evening and into the 
first half of the overnight period. Seas are also expected to 
increase to 3-4 feet. It looks like a marginal event for small craft 
conditions as far as winds are concerned. At this time...we have 
decided to hold off on any Small Craft Advisory for now and will mention occasional 
gusts up to 25kt. Winds and waves are forecast to subside Tuesday 
with strong high pressure in place. 


Quiet in the long term until perhaps the very end of the forecast 
period...as a wave of low pressure moving up the coast could tighten 
up the pressure gradient enough to build seas to Small Craft Advisory criteria late 
Friday night. 


&& 


Hydrology... 
no major hydrology concerns through the forecast period at this time. A 
system may impact the area by the end of the week into the 
weekend. 


&& 


Okx watches/warnings/advisories... 
CT...frost advisory from 2 am to 10 am EDT Tuesday for ctz005>008. 
New York...frost advisory from 2 am to 10 am EDT Tuesday for nyz067-068. 
New Jersey...frost advisory from 2 am to 10 am EDT Tuesday for njz002. 
Marine...none. 


&& 


$$ 


Synopsis...bs/maloit 
near term...maloit 
short term...bs 
long term...bs 
aviation...British Columbia 
marine...BC/maloit 
hydrology...bs