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fxus61 kbtv 212257 
afdbtv 


Area forecast discussion 
National Weather Service Burlington Vermont 
657 PM EDT Thursday Aug 21 2008 


Synopsis... 
high pressure will be anchored off the northeast Atlantic coast 
through Saturday. A south to southwest flow of air will bring warm 
and dry conditions to the forecast area...with slightly above 
normal temperatures expected through the weekend. 


&& 


Near term /until 6 am Friday morning/... 
as of 351 PM EDT Thursday...clear skies again tonight with a wide 
range of lows in the 40s and 50s and strong inversion. With this 
afternoons mixed out dew points in the low 50s expect fog again as 
temperatures drop below that after midnight. The center of the high is 
off the coast but expect an inland reflection through Friday 
morning over New England and New York. 


&& 


Short term /6 am Friday morning through Saturday night/... 
as of 351 PM EDT Thursday...fine late Summer weather will continue 
through Saturday night with the center of the high anchored off 
the northeast Atlantic coast. Temperatures continue to be a challenge as 
guidance continues to be too warm for maximum temperatures. Late August sun 
and relatively wet ground still keeping temperatures from mixing to 850 
again today. GFS MOS about 3 or so degrees too warm again today. 
Model soundings seem to be a better indicator of maximum temperatures which 
would be in the middle 80s vs upper 80s over the next two days 
despite 850 temperatures hovering around +16. The high gradually starts 
to break down on Saturday/Saturday night with some high and middle 
clouds starting to show up but it looks like precipitation should hold 
off until Sunday. 


&& 


Long term /Sunday through Thursday/... 
as of 351 PM EDT Thursday...the long term forecast has numerous 
challenges with limited run to run continuity between the 00z and 12z 
runs in the European model (ecmwf) and GFS. Will trend toward the 00z GFS ensembles 
forecast...with some blend of the 12z GFS and 00z European model (ecmwf). The latest 
ensembles continues to show middle/upper level trough across central Canada 
into the NE Continental U.S. With strong ulvl ridge across the southern United 
States. Meanwhile...the latest 12z GFS shows this middle/upper level 
ridge building into the Ohio Valley/Middle Atlantic States late 
Saturday into next Monday...as trough lifts into eastern Canada. 
However...feel GFS is too aggressive with development of 
ridge...especially with fast west to northwest follow aloft prognosticated 
to be across the NE Continental U.S. From deep trough. Therefore...will lower temperatures 
slightly over the weekend and continue to mention chances of afternoon/evening 
showers/storms...especially on Sunday. Given...the fast westerly 
follow aloft with embedded vorts riding along a surface cold front on 
Thursday into Friday will mention scattered showers/storms. Prognosticated 850 mb 
temperatures behind this front between 10-12c support highs on Thursday in 
the 70s. On Friday...weak short wave ridge tries to build into our 
County Warning Area...ahead of next piece of energy diving down across the Great 
Lakes in the follow aloft. Will keep Friday dry at this time...but will mention 
low chance for showers Saturday into Sunday...with best potential 
across our northern County Warning Area. Latest 12z GFS show prognosticated 850 mb temperatures 
surging to 20c by 00z Monday...which would support highs well into 
the u80s to l90s...but feel this is too quick and aggressive given 
the follow aloft. The GFS continues to Show Low level warm air advection across our County Warning Area on next 
Monday ahead of an approaching surface cold with prognosticated 850 mb temperatures 
between 20 and 22c. Meanwhile...European model (ecmwf) shows best low level warm air advection with 
prognosticated 850 mb temperatures around 20c...across the Middle Atlantic States and 
the Ohio Valley. Will trend toward the cooler European model (ecmwf) at this time...given the 
trends this Summer. 


&& 


Aviation /00z Friday through Tuesday/... 
through 00z Friday...widespread VFR expected through the period 
west/surface high pressure in control. Other than patchy late night/early 
morning br/fog and associated IFR/LIFR conds...clear skies and light winds 
less than 8 knots expected. 


00z Friday through Monday...mid/upper level ridge will continue to 
dominate taf sites Friday into Saturday...before a digging trough 
and associated cold front increase the chances for precipitation on Sunday. 
The small ribbon of 850-500mb moisture and brief stripe of 
700-500mb Omega...suggests overall duration of rainfall will only be 
a couple of hours...with some VFR conditions possible in the 
stronger showers. Overall...instability parameters are 
minimal...but given dynamics and timing of frontal passage...a few storms will 
be possible. Otherwise...mid/upper level trough deepens across our County Warning Area 
on Monday...with weak embedded 500 mb vorticity...which may produce a few 
scattered showers through 18z Monday with MVFR conditions. 


&& 


Btv watches/warnings/advisories... 
Vermont...none. 
New York...none. 


&& 


$$ 
Synopsis...Sisson 
near term...Sisson 
short term...Sisson 
long term...jmg/Taber 
aviation...Taber