Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
938 am MST Sat Jan 31 2015 

issued at 931 am MST Sat Jan 31 2015 

Minor adjustments at this time...have extended fog...some dense...into 
the early afternoon for areas along and east of a Sterling to Akron 
line. Have also slightly increased probability of precipitation along the northern border. 
In the mountains...some fog there as well so added patchy fog to 
the grids through early afternoon. 


Short term...(today through tonight ) 
issued at 308 am MST Sat Jan 31 2015 

Precipitation on the plains has failed to materialize with a dry 
subcloud layer and no significant forcing mechanism. Latest 
radar/satellite analysis does show a weak frontogenetical area 
organizing over the northern border with some echoes there...but 
all virga so far. The low levels may gradually moisten there with 
continued lift early this morning so will keep a few showers there 
otherwise the plains should remain dry most of the morning...with 
even some breaks in the clouds possible given thinning of moisture 
per satellite imagery. In the mountains...should see only a few 
bands of light snow continue. 

By this afternoon...the middle level frontogenetical area shifts 
southward across the forecast area and this will bring a little 
better chance of light precipitation across the plains. Dont 
expect anything terribly organized...but shallow upslope combined 
with improving lapse rates should help chances that precipitation would 
survive on the plains. Will continue the light rain/snow chances 
for this period with relatively mild temperature profile in place. 

Main attention will turn toward northern branch energy and 
stronger cold front arrival this evening. Cold front should push 
across the plains between 7 PM and 10 PM with shallow upslope 
flow behind it. However...the airmass will continue to destabilize 
with the NAM forecast soundings showing even a bit of cape in the 
low levels. There will also be potential instability around with a 
dry layer above 600 mb. Finally...there is an upper level jet 
driving right across the Front Range. All of these parameters 
raise concern for banded heavy snow showers. Have increased probability of precipitation 
and snow amounts for the Front Range. Liked some of the features 
of the hires nmm model so blended that into the forecast. Most 
accumulations on the plains should be under an inch...but anywhere 
heavier bands set up could easily see a quick 2-3 inches of snow 
late this evening into the early morning hours. At this time this 
would favor the western/southern Denver suburbs into the foothills 
and Palmer Divide area. 

Meanwhile...mountain areas should see a trace to 3 inches today 
and another 1-3 inches tonight. 

Long term...(sunday through friday) 
issued at 308 am MST Sat Jan 31 2015 

Drier air in northwesterly flow aloft will spread across the area on sun. 
There may still be some lingering light snow early in the morning 
mainly from Denver south to the Palmer Divide into the southern foothills. 
Otherwise the rest of the day should be dry except for a slight chance 
of -shsn in the higher mountains temperatures will be colder on sun with gusty 
northerly winds over the plains. 

For Sun night through Monday brisk west-northwest flow aloft will continue with some 
moisture affecting the mountains although orographics will be favorable 
moisture depth will be rather limited with lapse rates only in the 5- 
6 c/km range thus snow amounts should stay mainly on the light side. 
At lower elevations it will be dry however it will be windy at times 
in the foothills and near the Wyoming border. Forecast component along winds 
and low level pressure gradient are marginal for high winds at this point. 
As for highs readings will rise back into the 50s over northestern Colorado. 

Not much change expected for Monday night into Tuesday as brisk west-northwest flow 
aloft will remain over the area. Cross-sections show some increase 
in moisture in the mountains by Tuesday afternoon with lapse rates becoming more 
unstable so will see a good chance of snow. At lower elevations once 
again expect dry conditions with gusty winds in the foothills and near 
the Wyoming border. Afternoon highs over northestern Colorado will be warmer than Monday with 
readings rising into the upper 50s to lower 60s. 

By Wednesday a weak upper level trough may track across the area in the west-northwest 
flow aloft. In addition a cold front is forecast to move into northestern Colorado on Wednesday 
with upslope flow developing. Furthermore there is some middle level 
ascent and with position of upper level jet there would be some 
potential for precipitation enhancement. Overall this setup would bring a 
good chance of snow to the mountains and possibly at lower elevations if 
things come together right. As for highs if fnt does move across 
northestern Colorado by Wednesday morning then readings would stay in the 30s over the 

For Thursday and Friday mainly dry northwesterly flow aloft will be over the area 
with only a slight chance of -shsn in the mountains winds will be gusty at 
times in the mountains and foothills. Temperatures will rise into the 45 to 50 
degree range over northestern Colorado on Thursday and from 55 to 60 by Friday. 


Aviation...(for the tafs through 18z Sunday morning) 
issued at 931 am MST Sat Jan 31 2015 

VFR conditions will persist through today...although ceilings 
could lower to under 6000 feet this afternoon with ils Landing 
conditions. Brief light rain/snow showers also possible this 
afternoon with visibilities possibly lowering to 4-5 miles. Light 
north/northwest winds much of the day under 10 knots. 

Tonight...snow showers expected to develop behind frontal passage 
around 03z-04z. Snow showers should become more numerous behind 
the front. While prevailing visibilities may hold at 3-5sm or 
even higher...potential for heavier snow showers with brief 1/4 to 
1/2 mile visibility is there. Main time for these heavier showers 
would be 04z-11z...with local accumulations around 2 inches 
possible in heavier bands. North/northeast winds 10-15 knots 
behind front with a few gusts around 25 knots with frontal 


Bou watches/warnings/advisories... 


short term...barjenbruch 
long term...rpk 

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