Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
341 am MDT Thursday Jun 20 2013 


Short term...the broad upper low remains over the Pacific 
northwest and northern rockies resulting in a continued southwest 
flow pattern across Colorado. The airmass is quite dry so no 
thunderstorms are expected today or tonight. Weak surface front 
pushing southward over the northeast plains early this morning and 
will be through most of NE Colorado by 15z. This will push the 
surface low into western Kansas by afternoon while even drier low 
level air is behind this front with dewpoints dropping into the 
teens and 20s over southern Wyoming. There is a bit of cooler air 
behind the front as well so highs today will be a little 
lower...generally 3-5 degrees cooler than Wednesday highs. Low 
level moisture will be a bit higher towards the Kansas and 
Nebraska borders but even then...airmass looks too capped for any 
storms out there. 


Long term...operational models continue to show an upper trough 
migrating Ohio so slowly eastward over the Pacific northwest and 
northern Rocky Mountain regions during the Friday-Sunday time frame. 
Models appear to be in generally good agreement especially with 
large scale features. On Friday...the 500 mb trough axis is 
prognosticated to be over the Washington/Oregon/Idaho line with moderate 
southwesterly flow aloft downstream over Colorado. At lower 
levels...light/variable winds in the morning across the County warning forecast area align 
with the stronger southwesterly flow aloft with strong diabatic heating 
later in the day. Strongest south-southwesterly surface winds are 
expected across southeastern portions of the forecast area where gusts to 
around 25 kts are possible. The combination of very low relative humidity 
values...dry fuels...steep boundary layer lapse rates and these 
gusty winds make it necessary to issue a Fire Weather Watch for 
this area...specifically for fire weather zones 214 and 241. Kept 
eastern Elbert/Lincoln County fire weather zones 246/247 out of the 
watch...at least for now...because of the recent wetting rainfall 
in this area. Isolated gusty T-storms also a possibility over the 
higher slopes/ridges of the Front Range mountains and far northeast 
corner of the state where low-level moisture will be more 
plentiful. Maximum temperatures on Friday should generally be 4-5c 
above average for the date. 


For the remainder of the extended period...should see subtle day-to- 
day changes in temperature under clear to partly cloudy skies. 
However as the upper trough referred to above lifts newrd over the 
northern Great Plains on Sunday...a weak cold front is forecast to slide 
south across northestern Colorado early in the day resulting a 3-4c drop in 
temperatures from the day before. May also see a weak T-storm or two 
pop in the far northestern corner of the state late in the day. Otherwise 
it should continue to be quite dry. The trough moves out allowing 
another upper trough to drop in over the Pacific northwest on 
Monday. This puts north Central/Northeast Colorado under a very 
warm and dry southwest flow again. By Tuesday...models show this 
trough weakening and racing east across the northern rockies with 
little impact on our weather. By midweek...medium range models 
indicate a large dome of hot and dry air centering over southwest 
Colorado. At present time MOS temperature guidance is indicating 
maximum temperatures at lower elevations in the low/middle 90s on 
Wednesday. However should this ridge of hot air set up a bit 
farther east...we may once again see readings around the 100 degree 
mark on the plains. 


&& 


Aviation...observation at apa/den continue to show some smoke reducing 
visibilities at times from fires across southern Colorado. 
Frontal boundary to the north should move thorugh terminals 
between 11-12z and should suppress the smoke layer back to the 
south and result in improving visibilities. Behind the 
front...surface winds will shift northerly...then more east and 
southeast this afternoon. Airmass will be very dry so no 
thunderstorms are expected. 


&& 


Fire weather...will continue with the earlier issued red flag 
warnings for mountain valleys...Park County and Palmer Divide this 
afternoon. The stronger SW flow aloft will mix to the surface this 
afternoon resulting in gusty southwest winds and very low relative humidity 
levels below 10 percent. More of the same for Friday 
afternoon...hence the Fire Weather Watch for southern portions of 
County Warning Area. 


&& 


Hydrology...no issues. 




&& 


Bou watches/warnings/advisories... 
red flag warning from noon today to 8 PM MDT this evening for 
coz211-213-214-241. 


Fire Weather Watch from Friday afternoon through Friday evening 
for coz214-241. 


&& 


$$ 


Short term...entrekin 
long term....Baker 
aviation...entrekin