986 
FXUS65 KBOU 281642
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1042 AM MDT Wed Jul 28 2021

.UPDATE...
Issued at 1037 AM MDT Wed Jul 28 2021

Mid-level water vapor imagery shows an upper level ridge oriented 
over Colorado and the US Central Plains. Dry air in the mid-levels 
is quite evident over eastern Colorado with the more favorable 
moisture to our north and west. Observational soundings this morning 
reflect these conditions with dry air and warming in the upper 
levels indicating a dry day for most areas. Seeing some cumulus 
development over the mountains/foothills from the heating this 
morning. HREF members show weak instability and moisture over the 
higher terrain in the afternoon, so kept in chances for scattered 
showers and weak storms for the mountains/foothills. Current 
temps are around a few degrees warmer than this time yesterday 
over the plains keeping the forecast on track for slightly warmer 
highs for today. Given the current trend, Denver has a good shot 
at meeting or breaking the previous record of 98 degrees. 


&&

.SHORT TERM...(Today and tonight)
Issued at 406 AM MDT Wed Jul 28 2021

The upper ridge over the CONUS will continue to build today and
heights continue to rise across northeast Colorado. High
temperatures will climb into the upper 90s to low 100s across the
plains under mostly clear skies. The daily record high for Denver
of 98 F, set in 1876, will definitely be in jeopardy. Recent runs
of the HRRR Smoke model suggest a continued relative break in
smoke concentrations as flow around the high keeps most of it
north of Colorado. Subsidence and warm, dry air aloft will
continue to suppress convection but moisture will start to
increase over the mountains as the ridge slowly shifts east, which
should allow for some isolated to scattered storms over the high
terrain. Storm intensity will be limited by a lack of instability
but expect some light precipitation and gusty outflow winds. Skies
will clear overnight but lows will still be a bit warmer than
normal, in the mid 60s across the plains and 40s and 50s in the
high country. 

.LONG TERM...(Thursday through Tuesday)
Issued at 426 AM MDT Wed Jul 28 2021

High pressure will remain centered east of the forecast area 
Thursday into mid day Friday. The flow aloft is very weak. By 
Friday afternoon and night, the upper ridge center is stretched 
across Colorado northwestward out of the state. The flow aloft 
remains extremely weak through the weekend. The QG-Omega fields 
show very weak upward vertical velocity in place over the CWA 
Thursday through Friday night. 

With the upper ridge center moving into Colorado on Friday and 
through the weekend, moisture is progged to increase over the CWA. 
Precipitable water values are expected to come up into the 0.8 to 
1.4 inches range Friday night through at least Sunday night. With
the light flow aloft and all the increased moisture, heavy 
rainfall and flash flooding is certainly possible, and more so 
over the burned areas in the foothills and mountains from Friday 
afternoon into early next week. 
 
Temperatures look to stay above normals Thursday and Friday. 
Thickness fields indicate a cool down later Friday afternoon and 
evening. It looks like high temperatures will get below seasonal 
normals from Saturday through Tuesday, with Sunday looking like 
the coolest day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1037 AM MDT Wed Jul 28 2021

Expect VFR conditions through the period. Winds will become more
northerly through the afternoon then turn clockwise back to
drainage by the evening. Showers and weak storms are possible over
the higher terrain, but should stay confined to the higher 
elevation. 

&&

.HYDROLOGY...
Issued at 426 AM MDT Wed Jul 28 2021

Wednesday will see isolated to scattered thunderstorms over the
mountains. Storms will be slow moving but the moisture supply
remains limited, so the threat of burn scar flooding will still be
very low.

There will be a limited threat of flash flooding over the burn 
areas late day on Friday moisture increases. The threat of 
flooding will increase on Saturday and Sunday for all the 
forecast area, not just for the burn areas. This is because of the
increased moisture and slow movement of the showers and 
thunderstorms. Two inch per hour rain fall rates will be possible 
during the afternoon and evening periods of Saturday and Sunday. 
There will be a slight decrease in moisture Monday and Tuesday, 
but there will still be a threat of heavy rainfall. 

&&

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

$$

UPDATE...Mensch
SHORT TERM...EJD
LONG TERM....RJK
AVIATION...Mensch
HYDROLOGY....EJD/RJK