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Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
551 PM MST sun Feb 19 2017 

issued at 551 PM MST sun Feb 19 2017 

Main area of lift ahead of the trough is currently producing 
moderate snow over the mountains and light rain and gusty winds 
over the urban corridor at the moment. The moderate snow should 
occur for the next 2-3 hours before moisture rapidly decreases and 
subsidence occurs over the back of the trough. A few rain showers 
will still be possible over the eastern plains through midnight. 


Short term...(this evening through monday) 
issued at 349 PM MST sun Feb 19 2017 

Area radars show some showers over the mountains, but they are 
light. There is nothing over the plains right now. Models push the 
upper trough across the County Warning Area overnight and then increasing 
northwesterly flow aloft is progged on Monday. There is upward 
motion on the qg Omega fields this evening for the cwa, then all 
downward motion is progged overnight and Monday. Models all have 
northwesterly low level winds after the upper trough passes this 
evening. Downsloping winds are progged on Monday, weaker and 
westerly over the foothills and western plains; stronger and 
northwesterly over the eastern half of the plains. Moisture is 
wide spread this evening and relatively deep in the mountains. 
After the upper trough axis pushes across, things dry out 
significantly. The quantitative precipitation forecast fields have some measurable precipitation 
over the western half of the County Warning Area this evening, then a tiny bit 
more over the high mountains overnight, then nothing on Monday. So 
for pops, 60-90%s look good in the mountains tonight, less in the 
high valleys and foothills, down to 10-20%s over the plains 
early. Although the winds could help with orographic enhancement 
tonight in the mountains, by the time the directions get 
favorable, the moisture is gone. There is no cape progged this 
evening over the plains like there was yesterday on the 12z models 
for this evening. There is a decent looking mountain wave set up 
on the cross sections tonight, but speeds don't look high enough 
for highlights. For temperatures, monday's highs will be 0-2 c 
cooler than today's highs. 

Long term...(monday night through sunday) 
issued at 139 PM MST sun Feb 19 2017 

Monday night, the ridge axis will shift to the east with an 
increasing westerly flow aloft over the region. The models show 
some increase in moisture in the mountains west of the Continental 
Divide but dry from the Front Range foothills eastward. The 
pattern will be the same on a slight chance of pcpn will be 
possible in the mountains mainly north of Interstate 70. The 
pattern will continue through the day on Tuesday. The nam12 
spatial cross-section shows a weak mountain wave developing around 
12z Tuesday morning so gusty winds in the mountains and foothills 
will be a good possibility. Could see some gusts to 50 mph over 
exposed eastern slopes. Gusty winds will persist in the mountains 
and foothills, with dry conditions with temperatures climbing into 
the lower to mid 70s across the urban corridor and northeast 
plains. The dry conditions will elevate the fire danger across the 
northeast plains, refer to the fire weather discussion below. 
Tuesday night/Wednesday, Pacific moisture increases in the 
mountains below 600 mb so chc of pcpn will increase in the 
mountains west of The Divide, but persistent dry conditions with 
gusty winds at time over the northeast plains. A weak front is 
progged to back into the urban corridor around 18z Wednesday so 
there will be a slight drop in temperatures on Wednesday, with 
weak cold air advection aloft but temperatures will remain well 
above normal. Wednesday night, a stronger southwesterly flow aloft 
will be over Colorado with moisture increasing in the mountains 
ahead of the next trough. Stronger cold air advection with the 
next trough axis moves across northern Colorado on Thursday. Best chc of 
accumulating snow in the mountains will be Thu/Thu night. Chc of 
pcpn will carryover on the northeast plains, with the highest pops 
across the northern tier counties. Cooler with a strong sfc 
pressure gradient as the system exits the region Thursday night. 
Short wave ridging and subsidence on Friday with continued cool 
temperatures. Increasing moisture across northern and western Colorado 
Friday night through Saturday night, as another system moves into 
the Desert Southwest and is progged to lift northeast into Colorado late 
Sunday/Sunday night. 


Aviation...(for the 00z tafs through 00z Monday afternoon) 
issued at 551 PM MST sun Feb 19 2017 

Expecting the south-southeasterly winds to switch over relatively 
quick over the next hour or two to the northwest as the upper 
trough pushes east and a frontal push moves through. Winds may be 
gusty out of the northwest for a few hours before decreasing quickly and 
may become NE for a few hours overnight. Eventually, a drainage 
pattern should establish, however winds may stay gusty out of the 
west all night. Ceilings may briefly lower to 8000 ft between 
01-06z when a few sprinkles are possible, then quickly raise and 
scatter out. 

Mostly clear skies are expected Monday with westerly winds, with 
speeds less than 12 kts. 


Fire weather... 
issued at 349 PM MST sun Feb 19 2017 

Winds come up fairly strong for the eastern plains Monday 
afternoon, and humidity progs drop the rhs into the mid and upper 
teens. The conditions will get close to red flag warning criteria 
over the eastern plains Monday afternoon, but no highlights for 

Unseasonably warm temperatures with relative humidities dropping 
into the teens will be possible across the northeast plains of 
Colorado Tuesday afternoon, elevating the fire danger. Stronger 
winds will be in the foothills, but gusty winds over the Palmer 
Divide could warrant a Fire Weather Watch at some point. The 
threat will remain elevated on Wednesday but not as high as 
Tuesday. Temperatures will remain above normal but will be 
slightly cooler with a weak frontal passage Wednesday aftn. 


Bou watches/warnings/advisories... 


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