Weather

927 
fxus61 kokx 071733 
afdokx 


Area forecast discussion 
National Weather Service Upton New York 
133 PM EDT sun Sep 7 2008 


Synopsis... 
weak high pressure builds in from the west through tonight...then 
slides off the middle Atlantic coast on Monday and Monday night. A 
cold front will approach from the west on Tuesday...then cross the 
tri-state Tuesday night. High pressure then ridges in from the 
Great Lakes Wednesday and Wednesday night...then moves off the New 
England coast on Thursday. This high will then dominate our 
weather through Friday. A cold front will slowly approach from the 
west Friday night and Saturday. 


&& 


Near term /until 6 PM this evening/... 
have adjusted daytime highs down a few degrees based on initial 
conditions and hourly trends. 12z MOS guidance has also trended 
cooler...even though the Eta model MOS is still is significantly cooler 
than the GFS. Cold advection following Hanna will continue 
through the day and should cape temperatures to the lower 80s in metropolitan 
New York...and in the middle to upper 60s elsewhere. 


Northwest winds continue to diminish and will gradually veer around to 
the west this afternoon...generally 10 to 15 miles per hour. Downslope flow 
will minimize cloud cover. 


&& 


Short term /6 PM this evening through Tuesday night/... 
westward extension of Bermuda high builds in through the middle 
levels...with rising heights and zonal flow keeping things dry 
into Tuesday morning. Slightly cooler 850 temperatures will yield 
highs a bit cooler than today on Monday. Relatively clear sky 
conditions and light winds should promote decent radiational 
cooling tonight...with lows below normal (lower 50s normal cool 
spots middle 50s to around 60 elsewhere). Southerly return flow 
Monday night should result in lows a few degrees warmer Monday 
night than tonight. Followed a met/FWC blend at night (mav too 
warm) and a met/FWC/mav blend during the day (tempering mav 
numbers a tad but reflecting impact of downslope flow). 


An approaching strong cold front should bring a chance of showers 
and thunderstorms by Tuesday afternoon...with them becoming more 
widespread Tuesday night as the front crosses the tri-state. With 
1000-1500 j/kg of cape by late afternoon/early evening...Theta-E 
ridge building over area and decent shear...have the potential for 
some strong to possibly severe storms late Tuesday afternoon and 
evening. 


&& 


Long term /Wednesday through Saturday/... 
longer range models in fairly good agreement through Thursday 
night...then European model (ecmwf) is much faster in bringing a cold front through 
than the GFS to close the week (due to differences in handling 
high offshore). Due to these differences and no clear cut reason 
to favor one over the other...made little changes in the 
Friday/Saturday time frame (which already was leaning towards 
slower frontal passage. 


Will be noticeably cooler behind cold front Wednesday/Thursday with 
highs in the lower to middle 70s. Did lower lows Wednesday night (now 
have upper 40s in normal colder locations) and Thursday 
night...however believe that will end up being lowered further as 
guidance often underestimates amount of cold air behind these 
early season fronts (typically under does strength of high building 
in from south central canada)...then with high offshore and SW 
return flow setting up should see moderating temperatures 
Friday and Saturday. With differences in frontal timing do have 
chance probability of precipitation in Friday-Saturday (could end up being more diurnal 
Friday afternoon/evening and dry in the morning and late at night 
vice current blanket chance probability of precipitation currently in forecast). 


&& 


Aviation /18z Sunday through Friday/... 
VFR conditions. Weak trough over the area resulting in winds 
jumping around from west to northwest. Feel most terminals remain west/northwest 
(280-300) through the afternoon. Speeds of 9-12 kts diminish as 
the afternoon progresses as gradient weakens and diurnal mixing 
ceases. Winds lighten from the west toward evening. Little cloud 
cover to speak of...with maybe some ac toward evening as upstream 
cloudiness associated with weak upper trough approach. Skies clear 
overnight with light west winds. 


Mainly clear Monday morning with light west/northwest winds of 5 to 10 
kts. Coastal terminals such as kjfk/kisp/kbdr and kgon should back 
to the southwest by late morning. 


Outlook for 12z Monday through Friday... 
high pressure and VFR Monday afternoon and night. Showers/thunderstorms could 
produce sub VFR conditions Tuesday afternoon into Tuesday night ahead of 
an approaching cold front. High pressure and VFR conditions return 
Wednesday and Thursday. Sub VFR possible later Friday ahead of next front. 


&& 


Marine... 
large sea/swell combination still exists in the wake of Hanna across 
ocean waters. This will produce pounding high surf and dangerous 
rip currents today...with the high surf diminishing today...but 
strong rip currents are expected to continue into Tuesday. Refer 
to the latest coastal flood statement for details. 


The pressure fields over the area supports a continuing decrease 
in winds speeds. However...seas will be a be slower to 
respond...mainly due to the longer period swell in place. A Small 
Craft Advisory remains in effect for the ocean waters through 
tonight. 


High pressure building in will allow conditions to continue to 
diminish into Monday. 


Winds back to southerly and pick up again Tuesday ahead of a potent 
cold front. Small Craft Advisory winds may be reached south of Li ahead of the 
front...and gusty northwest winds and higher seas may necessitate a Small Craft Advisory on 
Wednesday morning. 


Long period swells from Hurricane Ike may impact the local waters 
through much of next week. 


&& 


Hydrology... 
The Saddle river at Lodi and the pomperaug river in New Haven 
County CT has dropped below flood stage this morning. No other 
new flooding is expected and river levels will continue to recede 
with dry weather through Monday. 


The next chance for rainfall is Tuesday afternoon and night...with 
about 0.5 inches expected basin wide. Locally higher amounts are 
possible in thunderstorms. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...high surf advisory until 6 PM EDT this afternoon for 
nyz075>077-080-081. 
New Jersey...none. 
Marine...Small Craft Advisory for hazardous seas until 6 PM EDT this 
afternoon for anz355. 
Small Craft Advisory for hazardous seas until 1 am EDT Monday 
for anz350-353. 


&& 


$$ 
Synopsis...pfm 
near term...pfm 
short term...pfm 
long term...mas/pfm 
aviation...precipitable water 
marine...bs 
hydrology...bs/pfm 

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