198 
fxus65 kbou 212110 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
305 PM MDT sun Mar 21 2010 


Short term...upper level ridge axis will shift eastward with 
westerly flow aloft increasing tonight. The Cross Mountain flow 
increases to about 25-30 knots...and mountain top stable layer 
develops. As a result...should see gusty winds develop over the 
higher peaks late this evening and work down across the Front Range 
foothills and into the far western suburbs by midnight. At this 
time...the lack of a significant Cross Mountain component should 
keep peak gusts under 40 miles per hour in most locations. 


Temperatures will be a few degrees warmer tonight and Monday as the 
downslope component increases. With 700 mb temperatures warming to 2-3c... 
highs will reach the middle 60s in Denver and close to 70f over the 
eastern plains. Main period of mountain wave induced cloudiness 
should occur in the morning hours...followed by mostly sunny skies 
in the afternoon per model cross sections. 


Long term...models have brisk west-southwesterly flow aloft over 
the forecast area Monday night...and southwesterly on Tuesday and 
Tuesday night. By 12z Wednesday morning there is an upper low 
somewhere over the western border area of Colorado. This is a 
change from previous runs. At 00z Wednesday afternoon...there is a 
trough axis moving across westerly Colorado with weaker 
southwesterly flow aloft for the forecast area. There is a weak 
upper level circulation over southeast Colorado to the northwest 
corner of Nebraska depending on the model by 00z late Wednesday 
afternoon. The qg vertical velocity fields have weak upward motion 
prognosticated for the forecast area Monday night into Wednesday evening. 
The strength of this vertical velocity is less than yesterday's 12z 
runs indicated. The low level pressure and winds fields bring the 
cold front into the forecast area about 06z Monday night. The 
upslope flow is prognosticated in the boundary layer through 
Tuesday...Tuesday night...into Wednesday afternoon. For 
moisture...both models show an increase Monday night...then all the 
forecast area has deep moisture in place much of Tuesday into 
Wednesday afternoon. By late Wednesday and Wednesday night both 
models show a significant moisture decrease. The quantitative precipitation forecast fields 
starting bringing measurable precipitation in from the northwest 
Monday night. By Tuesday afternoon...there is measurable 
precipitation over all the forecast area...the best over the 
foothills. There is pretty decent amounts prognosticated over much of the 
forecast area Tuesday night...then a decrease Wednesday through the 
day. By Wednesday night...only a tad is indicated over the 
mountains and foothills. Precipitable water values are in the 0.40 
to 0.50 inch range late Monday evening into Wednesday morning. For 
mountain probability of precipitation...lapse rates are OK...moisture is good...there is 
upward synoptic scale energy...but the orographic enhancement is 
minimal. Will go with 30%s Monday night. By Tuesday will 
increasing them to "likely"s and continue this into Wednesday 
morning. The best period looks to be Tuesday night...with the best 
available moisture...and the deepest upslope. For the plains and 
foothills...most ingredients are there...but the upward motion is 
not great. Will start probability of precipitation on Tuesday...going to "likely"s by 
afternoon in the foothills and adjacent plains. Again...the best 
time for snow will be Tuesday night. Accounting to forecast 
soundings...will go with mixed precipitation on Tuesday morning for 
the Western Plains...then snow by afternoon. Will keep a mix going 
for the eastern plains much of Tuesday. Will taper probability of precipitation off slowly 
in all areas through the day Wednesday. Will opt against highlights 
right now...with model run to run inconsistencies in mind. The best 
snowfall looks to be in the foothills...as with this last storm. 
For temperatures...tuesday's highs are 6-11 c cooler than monday's. 
Tuesday's highs are a tad cooler than wednesday's. For the later 
days...Thursday through Sunday...models have upper ridging Thursday 
into Friday. By Friday night...a fairly decent upper trough is 
prognosticated to move into Colorado and linger about into Saturday 
night. Both the GFS and European model (ecmwf) show this to be more significant 
than yesterday's runs. Will have minimal probability of precipitation in the mountains from 
Friday through Saturday night in the mountains only for now. 


Aviation...only a few high clouds across the area through Monday. 
Normal diurnal wind patterns expected at kden and kapa. At kbjc... 
should see a few periods of gusty west winds up to 25 knots 
developing after midnight as mountain wave develops. 


&& 


Bou watches/warnings/advisories...none. 


$$ 


Barjenbruch/koopmeiners