574 
fxus61 kokx 231136 
afdokx 


Area forecast discussion 
National Weather Service New York New York 
636 am EST Monday Nov 23 2009 


Synopsis... 
low pressure passing well south and east of Long Island today and 
tonight will bring a moist northeasterly flow to the tri-state 
area. The low will gradually move east of Cape Cod on Tuesday and 
allow high pressure to build in Tuesday night into Wednesday. Low 
pressure tracks from the Great Lakes into New England on Thursday 
into Friday resulting in unsettled weather. Colder and breezy 
weather moves in for the weekend in the wake of the system. 


&& 


Near term /until 6 PM this evening/... 
stratus continues to increase in coverage as easterly flow off the 
ocean prevails. The question for today is does is rain? Numerical 
model suite is supporting the develop of light precipitation during the 
afternoon. This will likely develop over Long Island first, than 
then spread/develop west (similar to the way the stratus develop 
overnight). 


Lift is not very impressive this afternoon with some warm advection 
seen in the veering low level NAM and GFS profiles that results in 
the strengthening of the low level inversion. Thus, feel this is an 
occasional light rain/drizzle type of precipitation. 


Temperatures do not move much today do to the lack on heating and the 
moderately breezy conditions off the Atlantic. 


Bottom line - a raw November day. 


&& 


Short term /6 PM this evening through Wednesday/... 
weak low pressure develops along the Carolina coast and tracks 
northeast to a position east of Cape Cod by late Tuesday. This is 
being driven by short wave energy coming out of the Tennessee Valley 
this morning as seen in the water vapor imagery. This shortwave 
moves though the long wave ridge on the East Coast and clears out the 
old cut offs that have been sitting around (currently over western 
CT and eastern ky). 


As a result of the weak upper forcing, do not believe the 
operational GFS development of a 1006 hpa on Tuesday east of Cape 
Cod. Prefer the weaker (old) European model (ecmwf) run. The local importance of this 
choice is tuesday's clouds and resulting temperatures. The weaker solution 
keeps winds more easterly on Tuesday resulting in another cloudy day 
with cool temperatures and occasional light precipitation - at least in the morning. 


The above also is consistent with the previous forecast. Which, with 
uncertainty for Tuesday being high in terms of cloud cover and 
temps, is best to stay with that forecast and not flip/flop. 


Temperatures range is small the next 48 hours due to cloudiness and 
persistent easterly flow. 


Wednesday looks good as high pressure builds in. Temperatures were raised 
slightly. 


&& 


Long term /Wednesday night through Sunday/... 
unsettled describes the period. Closed low moves from Chicago 
Thursday am to near local area by Saturday morning as it deepens. 
Latest GFS (00z)is very similar to the old (12z) European model (ecmwf) with this 
part of the forecast. NCEP global ensemble forecast system show 
surprisingly little spread with this system. Thus, the long term 
appears to have more forecast confidence than the short term. 


At the surface, weak low pressure near Michigan on Thursday 
redevelops on the triple point on Friday am over the local area and 
then deeps rapidly over New England. 


In terms of sensible weather...difluent southwesterly flow aloft and 
on-shore southeasterly surface flow mean clouds with at least a 
chance of light rain for Thanksgiving. 


The rapid development of the surface low early Friday (with a few 
hundred joules of elevated cape on the GFS soundings) supports the 
possibility of more rare November thunderstorms. This along with 
heavier rain and strong easterly winds means a rather unpleasant 
time for early morning shoppers. 


On Saturday...while upper low tracks over the region, the deeper 
(colder) GFS profiles keep any mixed precipitation inland. Windy too on the 
backside of the deep low. Based on GFS profiles...there some 
potential for Wind Advisory for Saturday. 


&& 


Aviation /12z Monday through Friday/... 
ceilings mostly VFR...with some variations to MVFR...by 14z or 
widespread MVFR ceilings are expected. However...not highly 
confident on the timing. Expect ceilings to remain MVFR as light 
rain develops and visibilities lower to MVFR in light rain and fog. 
Toward 22z ceilings likely lower to high end IFR. Not highly 
confident in this happening and ceilings may well remain MVFR. 


Winds from the north northeast to northeast...030 to 060...through 
the period with speeds 10 to 15 knots. 


Taf comments (forecaster insight on timing, confidence, trends and ground ops) 


Kewr...ceiling heights and timing uncertain...amendments 
likely. 


Kewr hourly wind forecast 
all wind directions are true...add 13 degrees for magnetic 
23/10z 04010kt 
23/11z 04011kt 
23/12z 03011kt 
23/13z 03011kt 
23/14z 03011kt 
23/15z 03011kt 
23/16z 03012kt 
23/17z 03012kt 
23/18z 03012kt 
23/19z 03012kt 
23/20z 03012kt 
23/21z 03012kt 


Kjfk...ceiling heights and timing uncertain...amendments 
likely. 


Klga...ceiling heights and timing uncertain...amendments 
likely. 


Kteb...ceiling heights and timing uncertain...amendments 
likely. 


Khpn...ceiling heights and timing uncertain...amendments 
likely. 


Kswf...ceiling heights and timing uncertain...amendments 
likely. 


Kisp...ceiling heights...visibilities timing 
uncertain...amendments likely. 


Kbdr...ceiling heights...visibilities timing 
uncertain...amendments likely. 


Kgon...ceiling heights...visibilities timing 
uncertain...amendments likely. 


Outlook 12z Tuesday through Friday... 
Tuesday...IFR/MVFR ceilings and visibilities in rain and fog 
early...with conditions improving to VFR during the morning. 
Tuesday night...VFR. 
Wednesday...VFR. 
Wednesday night through Thursday...sub VFR possible in rain. 
Friday...sub VFR possible in showers. Snow possibly mixing in north 
and west of the NYC terminals at night. 


&& 


Marine... 
already solidly at Small Craft Advisory levels (both seas and gusts) on the coastal 
ocean zones at 8z...and with pressure gradient continuing to tighten 
would expect remainder of coastal ocean waters to have gusts to 
25-30 knots within the next few hours...so have left headlines as is to 
get started. 


With damming high remaining anchored over the Canadian Maritimes 
with an extension back into the northeast...and a slowly 
strengthening coastal low working its way NE from the southeast 
coast...pressure gradient will remain tight through Tuesday...and 
thus with at least 80 percent confidence that gusts to Small Craft Advisory levels 
will continue on all waters through then...have extended the Small Craft Advisory 
through Tuesday for all waters. 


The persistent strong NE flow will build seas to 6-11 feet by tonight 
(highest southeast portion of anz-350 lowest western portion of anz-355). 
Could see some 5-6 feet waves near the moth of Long Island Sound late 
tonight/Tuesday morning as well. As low pulls to the east-northeast Tuesday 
winds back to the north and diminish slightly. 


North winds continue to diminish Tuesday night as pressure gradient 
continue to relax...and expect the sound/Harbor/bays to fall below 
Small Craft Advisory criteria by midnight...but seas on the ocean zones will stay 
at/above criteria through all the night. 


High pressure building in Wednesday/Wednesday night should provide a 
24 hour or so period with sub-Small Craft Advisory conditions. 


This lull comes to an end late Thursday as winds increase out of the 
east ahead of another coastal storm...this one likely much stronger 
than the one that impacted the area earlier in the week. For now 
capping things at small craft levels due to some uncertainty in the 
low/S track/strength but would not be surprised if at least gale 
force gusts impacted all waters Thursday night into Friday. 


&& 


Hydrology... 
light precipitation starting this afternoon into early Tuesday. Quantitative precipitation forecast is 
generally a quarter inch or less. A more significant quantitative 
precipitation event is possible Thursday night into early Friday 
with over and inch on average. 


At this time...no significant hydrologic problems are anticipated. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...Small Craft Advisory until 6 PM EST Tuesday for anz330-335-338- 
340-345-350-353-355. 


&& 


$$ 
Synopsis...jst 
near term...jst 
short term...jst 
long term...jst 
aviation...met 
marine...pfm 
hydrology...jst 

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