Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
859 am MDT Tuesday Apr 28 2015 

issued at 859 am MDT Tuesday Apr 28 2015 

Patchy fog that developed early this morning in wake of partial 
clearing has pretty much burned off with daytime heating. 12z 
Denver showed shallow instability in the moist layer under a 
strong capping inversion near 650 mb. As a result...the daytime 
heating has led to a fast development of shallow 
cumulus/stratocumulus. Expect partly cloudy skies most of the day 
although continued mixing should eventually bring more sunshine 
through the afternoon. Overall forecast is on track with just 
slight adjustments to cloud cover. 


Short term...(today through tonight ) 
issued at 420 am MDT Tuesday Apr 28 2015 

Early in the shift believed fog would form not too long after 
midnight and become widespread on the plains by 09z based on the 
00z NAM and WRF...and 06z rap and hrrr surface and boundary layer relative humidity 
fields. Same models also indicated a surge of northeasterly low-level flow 
around a surface high slipping sewrd out of Wyoming during the pre-dawn 
hours. Still not seeing much in the way of fog yet...although surface 
winds have turned northeasterly in areas east of the I-25 urban corridor 
within the past couple of hours. So will hold onto the fog and low 
cloud forecast for the plains until around 15z this morning. 
Should see lowest visibilities in low lying areas along the South 
Platte from around Greeley to Sterling. Will also keep patchy fog 
in the mountain valleys...particularly South Park with its fresh 
blanket of snow...through early this morning. 

Should see the last of the fog and low cloud burn off by late 
morning as drier air filters down from Wyoming on light northerly 
winds. Could see a band of thick cirrus swinging southward over the 
area late this morning...marking the start to warming aloft. Upper 
ridge building over the western Continental U.S. Is forecast with slowly 
migrate eastward over Colorado next 24 hours. Airmass accompanying 
this ridge is warmer and much drier. Although lingering low-level 
moisture and daytime heating may bubble up into a few showers over 
the mountains and South Park area this afternoon. Should then see skies 
clear overnight. Highs expected today and tonight will Hoover 
around the seasonal norms. 

Long term...(wednesday through monday) 
issued at 420 am MDT Tuesday Apr 28 2015 

High pressure ridge aloft builds across Colorado on Wednesday with 
continued warming and dry airmass. 700mb temperatures nearing +6c 
will result in readings in the 70s across the plains. The ridge 
shifts east of Colorado on Thursday as a fast moving upper level 
disturbance and associated cold front poised to move over the 
region late Thursday afternoon and night with increasing moisture 
and shallow upslope flow developing. This will bring a return to 
late day showers and thunderstorms. Storms may linger well into 
the night...especially southern and eastern sections of the County Warning Area. 

Behind the Thursday trough...the flow aloft becomes more of a zonal 
west to northwest flow with enough moisture to keep a chance of 
afternoon and evening thunderstorms from Friday afternoon and 
continued through the weekend. Storms may become more numerous by 
late Sunday with another weak cold front and an embedded 
disturbance. Highest probability of precipitation will remain over mountains and Palmer 
Divide. Temperatures through the period will be around or a bit 
higher than seasonal normals. 


Aviation...(for the tafs through 18z Wednesday morning) 
issued at 859 am MDT Tuesday Apr 28 2015 

Fog threat has ended this morning but shallow 
cumulus/stratocumulusclouds developing with daytime heating. 
These may go broken with ceilings in the 2000-2500 foot layer 
through about 18z before gradually lifting and scattering out 
again. Ils Landing conditions could linger into early afternoon. 
Otherwise visual landings will prevail with light and normal 
diurnal wind patterns 10 knots or less. 


Bou watches/warnings/advisories... 


short term...Baker 
long term...entrekin 

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