896 
fxus65 kbou 300947 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
345 am MDT Sat Aug 30 2008 


Short term...upper ridge gradually shifting east with southwest 
flow aloft developing over Colorado by tonight. Surface winds also 
steadily increasing as the upper trough edges eastward into the 
Pacific northwest. Not a lot of change in stability from yesterday 
as a slight increase in low level moisture will be offset by a 
little drying aloft today. Deeper moisture will move in from the 
southwest later tonight. So until then...marginal instability with 
the best thunderstorm chances remaining over the mountains south of 
Interstate 70. A little better chance for severe storms on the 
Palmer Divide this evening as low level moisture could provide convective available potential energy 
of 1000-1500 j/kg if it is warm enough...but still a small threat 
especially given the weak shear which will lead to pulse storms. 
Main changes were to add low probability of precipitation to Lincoln County this evening and 
increase overnight winds a little. 


Long term...on Sunday...an increasing south to southwesterly flow 
aloft will occur ahead of a storm system dropping out of the Pacific 
northwest. Most of the moisture ahead of the trough appears to be over 
the western half of the County warning forecast area...so will keep best thunderstorm coverage in and 
near the mountains. Interactive soundings still show the air mass capped 
at or below 600 mb over the eastern plains...so no probability of precipitation planned there for Sunday 
aftn/evng. Low level moisture will be increasing however...expecially 
for Sunday night into Monday. Surface winds over the eastern plains will increase 
signficantly as strong upper level winds mix down to the surface. Specific 
humidities are prognosticated to increases from 8g/kg to 12 g/kg over much of northestern 
Colorado Monday aftn/evng. Interactive soundings on Monday yield convective available potential energy from 
around 800 to 1700 j/kg with precipitable water values around one inch. On Monday 
the GFS appears to have the southern most track with the upper low 
over northern Nevada at 12z shifting it into northestern Wyoming by 12z Tuesday. The 
strongest upward qg vertical ascent occurs Monday aftn/evng. Main 
adjustment involved increasing the probability of precipitation another 10-20 
percent...especially in the mountains. By Tuesday a drier west-northwesterly 
flow aloft will be over Colorado following the passage of this first 
system. The rmdr of the week will remain unsettled with a continued 
northwesterly flow over Colorado for Wednesday through Friday. Will confine most the 
adjustments to Sunday and Monday. 


&& 


Aviation...VFR conditions expected through tonight. Isolated 
thunderstorms are expected southwest and south of Denver again. 
South winds will increase this afternoon...with gusts over 20 knots 
expected after 22z. The winds will continue overnight. 


&& 


Bou watches/warnings/advisories...none. 


$$ 
Gimmestad/Cooper