327 
FXUS65 KBOU 072317
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
517 PM MDT Tue Sep 7 2021

.SHORT TERM...(This evening through Wednesday)
Issued at 139 PM MDT Tue Sep 7 2021

Temperatures have been slower to warm today due to cooler air 
behind last night's cold front and the increase in smoke today. 
Another cool night can be expected for low lying areas due to the 
dry airmass, clear skies, and light winds. Not much change in the 
weather for Wednesday as the upper level high over the Great Basin
dominates the weather pattern. The airmass will warm up a few 
degrees over northeast Colorado with most locations in the upper 
80s to around 90F degrees. 

.LONG TERM...(Wednesday night through Tuesday)
Issued at 139 PM MDT Tue Sep 7 2021

Hot and mostly dry conditions persist through much of the period 
with potential for record breaking highs Thurs/Fri. There is good
agreement among ensemble guidance for an upper level ridge to 
push east into the region by Thursday. Dry and unseasonably warm 
conditions increase fire weather concerns, but overall weaker 
winds limit this potential. Agreement decreases into the weekend 
in the details of a few passing systems, but overall will see a 
return of showers/thunderstorm chances, mostly over the higher 
terrain. 

Thursday, the main axis of the upper ridge slides east advecting 
higher heights into CO promoting further warming and drying 
Thursday and Friday. 700mb temperatures increase 2-4 C compared to
Wednesday. There is potential for records to be broken Thurs/Fri
for Denver area although smoke may hinder this. Thursday will be 
close with a previous record of 94. There's a higher chance to 
break the record Friday with ens means in the mid-upper 90s and a
"low hanging" record of 93 for Denver. With the ridge overhead, 
both days will see below normal moisture. When mixed, relative 
humidities could be in the single digits to teens. Something to 
keep an eye on as it does increase fire weather concerns. With 
ensemble guidance showing the jet max to the north, winds will be 
weaker under the ridge limiting potential. Increasing W flow 
Friday may bring some potential for gusts over North Park. 
However, most ensemble members stay under 25 mph gusts. 

Agreement decreases among ensemble/deterministic guidance over 
the weekend through early next week. There is a spread in 
solutions evident in deterministic guidance for the timing/position
of passing shortwave troughs. This would mainly impact precip.
chances. Moisture increases in the region and with some 
instability and weak QG forcing for lift, there will be a return 
of shower and thunderstorm chances. Higher chances will be over 
the higher elevations. Chances continue into early next week. A 
shift to westerly component flow aloft from the weakened ridge 
and shortwave passages brings potential for increased winds over 
the higher terrain through early next week. The slight increase in
moisture should limit fire weather potential. Temperatures will 
be slightly cooler each day through the weekend into early next 
week with highs in the 80s in the lower elevations and 70s in the 
higher elevations by Monday. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 414 PM MDT Tue Sep 7 2021

VFR conditions will continue for all TAF sites across the area.
Northeasterly winds will continue through the early evening 
hours. There is an increase in low-level winds tonight due to 
drainage from the Palmer Divide. This will most likely begin 
around 07Z at KDEN and increase winds up to 11kts. Winds will 
decrease by early Wednesday morning at all sites 13Z through 
Wednesday afternoon turning southwesterly. Although surface 
visibility has improved, slant visibility will be impacted due to 
wildfire smoke. Overall, a few high clouds are possible at all 
terminals.


&&

.HYDROLOGY...
Issued at 139 PM MDT Tue Sep 7 2021

No flash flooding concerns through Friday as conditions will be 
hot and dry. Moisture gradually returns over the weekend and weak 
forcing will allow for scattered showers and thunderstorms over 
the higher terrain into early next week. Instability will likely 
be limited with precipitable water values over the mountains in 
the .5- .7" range. This will keep flash flood potential limited. 

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Meier
LONG TERM...Mensch
AVIATION...AD
HYDROLOGY...Mensch