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Area Forecast Discussion (AFD)

Issued by Denver/Boulder, CO (BOU)

                            
000
FXUS65 KBOU 242133
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
333 PM MDT Sat Aug 24 2019

.SHORT TERM...(This evening through Sunday)
Issued at 114 PM MDT Sat Aug 24 2019

Water vapor showing upper trof axis has shifted southeast into 
the far northeast corner of Colorado this afternoon with building 
ridge of higher pressure upstream. QG fields showing increasing 
subsident flow over the northeast plains by this evening so not 
expecting any thunderstorms over the county warning area tonight. 
Further west towards the mountains, fair amount of mountain wave 
clouds this afternoon with decent gusty winds over the higher 
mountains passes with gusts in the 40-50 mph range up on Berthoud 
Pass today. Cloud cover has also kept temperatures a bit cooler 
today, more in the lower 80s so far this afternoon. 

Sunday will be characterized by a dry and moderate northwest flow
regime across Colorado. Main concerns will be the high fire 
danger, which will be addressed below with gusty winds and low 
humidities over mountains and higher terrain areas. Temperatures 
will warm considerably by Sunday afternoon with readings climbing 
well into the mid/upper 90s as 700mb temperatures rise to around
+19c.  The record for Denver is 99 degrees, so may be a degree or
2 shy. Forecast soundings show a dry airmass over the region with
warming aloft and no chance for thunderstorms in the county 
warning area. Airmass will become well mixed by Sunday afternoon 
with gusty winds in the mountains and plains. Cross sections showing
continue potential wind gusts of 30 to 50 mph over mountain passes.


.LONG TERM...(Sunday night through Saturday)
Issued at 300 PM MDT Sat Aug 24 2019

A big pattern change will begin to take place on Sunday night lasting
through the middle of the work week. This pattern will feature a
strong longwave trough over the northern Great Plains with a
surface cyclone over souther Canada. The GEFS has the 500 mb 
heights in this trough at the minimum in the database over the 
North Dakota area on Tuesday to give an idea of the strength and 
cold air associated with this trough. At the surface, a series of 
cold fronts will move through eastern Colorado with the first 
arriving early Monday morning. This will cool high temperatures to
the upper 70s and low 80s across the plains Monday afternoon. A 
Longmont anticyclone will develop with strong northwest winds 
across the Cheyenne Ridge and northeast winds over the Palmer 
Divide. The slight upslope flow over the Palmer Divide could 
develop a shower or two Monday afternoon but there will be a 
strong mid level inversion which will greatly limit any shower 
activity.

Another cold front will push through the area on Tuesday with even
cooler air behind it. High were decreased to the 70s over the 
plains since there will likely be some cloudiness during the day. 
Showers and perhaps a weak thunderstorm will be possible along 
this front especially if the front comes through during the 
afternoon/peak heating. 

The  trough will continue to move eastward on Wednesday with an 
upper level ridge building over the southwest US. Downslope flow 
over our CWA will allow temperatures to climb slightly above 
normal with dry conditions. Weak shortwaves will move around the 
northern extent of this ridge on Thursday and Friday bringing a 
chance for scattered thunderstorms. Highs will be above normal and
Denver may get back into the 90s. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 114 PM MDT Sat Aug 24 2019

VFR with still a good batch of mountain wave cloudiness 
today and this evening. northerly winds at local terminals will 
shift east and southeast this evening before turning southerly 
drainage overnight. Airmass is dry in low levels with no 
thunderstorms expected through Monday. 

&&

.FIRE WEATHER...
Issued at 114 PM MDT Sat Aug 24 2019

Fire danger will be increasing by Sunday afternoon over the 
mountains and higher terrain towards the Wyoming border. Minimum 
humidity levels will be dropping below 15 percent while mountain 
wind gusts expected in the 30 to 50 mph range during the 
afternoon. Will be upgrading the fire weather watch to a red flag 
warning for current areas. High mountains will be windy but 
humidities will be above 20 percent so won't have any flags raised
there.
 
&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM to 8 PM MDT Sunday for COZ211-
213>215-238-242.

&&

$$

SHORT TERM...Entrekin
LONG TERM...Danielson
AVIATION...Entrekin
FIRE WEATHER...Entrekin