797 
fxus65 kbou 081121 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
420 am MST Thursday Jan 8 2009 


Short term...mean sea level pressure gradients across the state 
remain moderately strong as moderate westerly flow aloft continues 
over Colorado. The enhanced flow aloft has helped surface 
temperatures at many locations along the I-25 corridor to remain 
quite warm for early January. Strong winds also continue in the 
mountains and over the Continental Divide...but not as strong as 
yesterday. With the upper jet that drove yesterdays wind event 
moving further away from the region...expect winds to gradually 
decrease through today. However...winds aloft are still moderate in 
strength...and with all the warming that is expected...the airmass 
will be well mixed through most of the day...allowing the middle level 
winds to mix down to the surface. Winds will not be strong enough 
for any highlights...but will be strong enough to make firefighting 
efforts tricky at best. Temperatures today should have no problem 
making it to the lower and middle 60s by midday. 


With the dry airmass well entrenched over the state and subsidence 
from a weak upper ridge in place...probability of precipitation across the state will be 
zero for today. Later tonight...moisture will begin increasing 
again over the northern mountains with a pretty good chance of light 
snow falling by Friday morning. No accumulations are expected by 
12z tomorrow morning. 


Long term...an upper level trough will move across the area on Friday 
along with a cold front. Cross-sections show moisture depth in the mountains 
up to 500 mb with favorable orographic component and lapse rates 
around 7 c/km with . Thus should see widespread snow with gusty 
winds. Amounts look to be below warning criteria so Winter Weather 
Advisory will likely be needed. Over lower elevations a cold front will 
move across the plains with north-northwesterly low level flow shown by NAM and 
GFS. Thus overall setup not real favorable for snow however with 
decent qg ascent and lapse rates can not rule out at least a slight 
chance of -shsn. Temperatures will be colder on Friday with highs 20 degrees 
cooler than thursdays readings over the plains. 


For Friday night some moisture will linger in the mountains however lapse 
rates will become more stable thus any any additional amounts should 
be light. For Sat and sun dry northwesterly flow aloft will be over the area 
with little chance for precipitation. Cross-sections show increasing flow aloft 
Sat night into sun with setup possibly becoming more favorable for 
high winds in and near the foothills Sat night into Sun morning. Temperature 
wise appears highs on Sat will be near seasonal levels over northestern Colorado 
with 5 to 10 degrees of warming on sun. 


For Sun night and Monday northwest flow aloft will continue over the area with 
cross-sections showing a slight increase in moisture in the mountains 
however lapse rates will remain poor so will keep precipitation chances on 
the low side. Over lower elevations GFS shows a cold front moving into 
northestern Colorado on Monday with some upslope flow possible which could lead to a 
slight chance of snow if enough moisture is available. Temperatures on Monday 
may cool back to at least seasonal levels over northestern Colorado. By Tuesday 
overall pattern will not change much as northwest flow aloft continues. 
Cross-sections do not show a lot of moisture so will keep probability of precipitation on 
the low side in the mountains with dry conditions over lower 
elevations. 




&& 


Aviation...moderate west winds will continue over the state today 
with mountain wave turbulence over the Front Range persisting. At 
kden...ceilings and visibilities will be VFR/unlimited. However gusty west 
winds will prevail through middle-late afternoon. 


&& 


Bou watches/warnings/advisories...none. 


$$ 


Kdrby/rpk