145 
fxus61 kokx 070533 
afdokx 


Area forecast discussion 
National Weather Service Upton New York 
133 am EDT Tuesday Oct 7 2008 


Synopsis... 
a large area of cool Canadian high pressure will build over the 
region on Tuesday and then slide south of the area on Wednesday 
resulting in clear/sunny skies. Milder temperatures along with 
clouds and possibly light precipitation is expected to return 
Thursday into Friday as a southwesterly flow set up. The unsettled 
weather may continue into the weekend. 


&& 


Near term /until 6 am this morning/... 
updated the afm and pfm for hourly temperature trends. 


Upper level short wave has moved off the coast...east of the 
area...as seen on water vapor imagery. Drier air moving in with 
rising heights and thickness. 


North-northwest flow prevails in the low levels through morning and only the 
protected locals will decouple from the boundary layer. 


Low temperatures in the 40s (50 lga) for most locations except well inland 
where 30s prevail. (Upper 30s in The Pine Barrens of Li - but wind 
prevents being even colder there) 


Frost advisory is up - but thinking is that this will be mainly 
patchy frost in the protected valleys. Will reword the advisory 
to reflect this idea. 


&& 


Short term /6 am this morning through Thursday/... 
high pressure slides southeast across the region on Tuesday. Light 
winds for Wednesday am with clear skies indicates more of a 
widespread frost and will include interior Suffolk County as 
well. Temperatures by Wednesday morning drop into the 20s in the 
northwest per mav MOS (which is cooler than other mos), which 
seems good based on the clear skies and calm winds. Thus am 
issuing a freeze watch and wording the colder areas as widespread 
frost. This should be the killing frost - normal time for first 
frost is Oct 10 for our northern areas. 


Return flow warms temperatures for Wednesday night as clouds advect in. 


Light precipitation possible by late Thursday. 


&& 


Long term /Thursday night through Monday/... 
still large differences in the medium range model guidance for later 
this week...especially with regard to Pacific jet energy moving ito 
southern Canada...which in turn translates to low forecast 
confidence. The 00z European model (ecmwf) was more aggressive with this jet 
energy...undercutting eastern Canadian ridging beginning Thursday and 
producing drying northwest flow aloft for Friday and beyond as strong high 
pressure develops/builds down from the Great Lakes. Meanwhile...a 
southern stream cutoff low gets trapped underneath a building long 
wave ridge along 80w...which is suspect as European model (ecmwf) southerly bias with 
southern stream cutoff lows may be coming into play. 


The 12z GFS is weaker with the jet moving across Canada and appears 
to be trending toward the ecwmf...but does not allow the southern 
stream low to become cut off from the westerlies...bringing it up 
into the area with a good shot of rain Friday into Friday night. 


Both models have also dug their heels in with respect to 
trends...and the Canadian has flip-flopped from a GFS-like solution 
in the 00z run to European model (ecmwf)-like in the 12z...further reflecting the 
uncertainty. As a result will have to carry low chance pop through 
much of the long term...with very low confidence in forecast 
details. 


&& 


Aviation /06z Tuesday through Saturday/... 
VFR through the period. High pressure continues to build toward 
the area into Tuesday. Skies will be clear with unlimited 
visibilities. Winds from the north will gradually back around to 
the northwest early Tuesday morning...then become more westerly 
late Tuesday as the center of the surface builds west of the 
terminals. Winds will then become light and variable Tuesday night. 


Outlook for 06z Wednesday through Saturday...VFR through Thursday. 
A slow moving storm system will possibly bring sub-VFR conditions 
from Thursday night into Saturday...depending on its exact track. 
A low confidence forecast in the extended for the weekend. 


&& 


Marine... 
high pressure slides across the region on Tuesday changing the 
flow to southerly on Wednesday. Tranquil winds and seas expected 
through Thursday. 


For the long term...forecast reflects quiet conditions from Thursday 
night and beyond...but confidence is low beginning Friday night. If 12z 
GFS solution of weak low pressure moving up the coast comes to 
pass...Small Craft Advisory conditions in the form of hazardous seas could occur Friday 
night into Sat night. 


&& 


Hydrology... 
no major hydrology concerns through the forecast period at this time. Some 
light precipitation is expected late Thursday into Friday. 


&& 


Okx watches/warnings/advisories... 
CT...frost advisory until 8 am EDT this morning for ctz005>008. 
New York...frost advisory until 8 am EDT this morning for nyz067-068. 
Freeze watch from late tonight through Wednesday morning for 
nyz067-068. 
New Jersey...frost advisory until 8 am EDT this morning for njz002. 
Freeze watch from late tonight through Wednesday morning for 
njz002. 
Marine...none. 


&& 


$$