508 
fxus65 kbou 192156 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
256 PM MST Wednesday Nov 19 2008 


Short term...a decent boundary is move southeastward across the 
plains right now. Northeasterly flow behind it is gusty to around 
20 knots right now. The stratus is quite aways away yet in 
northeastern Wyoming and north central Nebraska. Dew points in 
those areas area are in the 25 to 30 f range. Temperatures behind 
the front are dropping 3-4 f per hour. I figure sunset will help 
quite a bit and low clouds will get into our plains by middle 
evening. Models have changed little. There is still weak upward 
motion prognosticated in the synoptic scale tonight and Thursday. There 
is still a flattening ridge aloft with increasing 
west-northwesterly jet level flow. The boundary layer flow is 
pretty uniform easterly tonight and Thursday at least up into the 
foothills. For moisture...700 mbs and below look saturated from 06z 
tonight through 00z Thursday afternoon. The GFS is a bit deeper 
than the NAM with the moisture. Both show little moisture above 
that. Forecast sounding continue to point to a drizzle event... 
freezing drizzle much of the time. Will change little with the 
probability of precipitation. For temperatures...thursday's highs are 9-12 c colder than 
this afternoon's. 


Long term...some question about how quickly the low cloudiness will 
advect out of the area. Southerly winds will increase Thursday night 
and flow at the top of the cloud deck will begin to get a westerly 
component. This should put a hole in the clouds on the north side of 
the Palmer Divide. However...this is a good pattern for a Denver 
cyclone which will likely tend to hold the low clouds in against the 
foothills from Denver northward. Eventually this area should erode 
as the top of the deck blows away during the morning...or at latest 
be pushed out as drier air moves in from the north behind another 
weak cold front later in the day. I did keep some drizzle through 
Thursday night and hang on to more cloud cover on Friday. 
Temperatures will still warm nicely in the afternoon. Models 
continue to show the Friday system aloft passing mainly north of 
Colorado...with the further south NAM skirting the northern border 
with clouds and possibly mountain showers. Overall though it looks 
pretty dry once the low levels on the plains flush out. 


There is better consistency since last nights models on a shortwave 
passing north of US on Sunday...then ridging again as a trough 
develops over the east. Again the air mass looks to be pretty 
dry...though the European model (ecmwf) does have the system far enough south to 
threaten some clouds and mountain showers. No big heat wave but dry 
with above normal temperatures Monday and Tuesday...normal highs are 
now around 50. Upstream trough developing along the coast may spread 
moisture and possibly colder air late in the week...Wednesday at 
earliest but probably later. Maybe some light snow for the mountains 
by Thanksgiving but not looking like anything significant before 
next weekend. 
&& 


Aviation...a cold front is pushing through the area at this time. 
By 05z this evening...ceilings should be IFR at the three airports. 
Visibilities due to freezing drizzle and fog should be IFR by about 
09z Thursday morning. IFR conditions should continue at least 
through 21z Thursday afternoon. 


&& 


Bou watches/warnings/advisories...none. 


$$ 
Rjk/gimmestad