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Area Forecast Discussion (AFD)

Issued by Denver/Boulder, CO (BOU)

FXUS65 KBOU 161644

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1044 AM MDT Tue Jul 16 2019

Issued at 1043 AM MDT Tue Jul 16 2019

There were a few light showers in the I-70 mountain corridor this
morning, but those have since dissipated. Satellite indicates some
mid level moisture still streaming across the state, but
precipitable water values have trended downward by about 0.10-0.15 
inch. That said, we're seeing new convective development on the 
west slope of Colorado already late this morning. The forecast for
scattered but faster moving storms is still on track this 
afternoon into early evening, with potential for an isolated 
severe storm or two over the northeast corner where deeper 
moisture and MLCAPE near 2000 J/kg exists. The majority of this
threat would be northeast of a Cheyenne to Fort Morgan and Akron 
line, but the weak morning easterly surge that we observed could 
bring this threat just a little farther west than that. 


.SHORT TERM...(Today and tonight)
Issued at 243 AM MDT Tue Jul 16 2019

An upper trough over the western US coast will push inland and
into the Northern Rockies down into the Great Basin throughout
today. This will turn flow aloft from westerly to southwesterly,
continuing the warming trend. Drier air visible on water vapor
imagery is pushing into northeastern Colorado, which is expected
to drop precipitable water values by 0.2 to 0.4 inches over 
yesterday's readings. This will result in another day of 
convection firing off the higher terrain just after noon, then 
spreading east over the plains. The difference will be that the 
storms have a lower potential to produce localized flooding due to
less moisture available and they'll be be moving quicker due to 
faster winds aloft. With a jet over northern state border, higher 
shear will exist over this area and will give a better chance for
stronger storms including a higher chance for hail, possibly up 
to an inch in diameter. A Marginal risk for severe storms is in 
effect for an area northeast of a line from Cheyenne to Fort 
Morgan to Akron, where CAPE values of over 2000 J/kg are expected
to exist.

Storms should exit out east by midnight with clearing skies. A
surface trough will be deepening across the eastern plains to help
increase westerly winds in the high terrain and foothills,
downsloping into the urban corridor. This will result in warm
overnight lows. 

.LONG TERM...(Wednesday through Monday)
Issued at 243 AM MDT Tue Jul 16 2019

Main trend through Friday will be warmer and drier, 
especially Thursday and Friday with temperatures approaching 100 
degrees on the plains and the potential for record setting 

Initially for Wednesday, the high pressure ridge will remain 
anchored across much of the southern high plains with southwest flow 
across Colorado. There will be drier air beginning to work its way 
through mountains and Front Range but still some lingering moisture 
still on the northeast plains. This will continue a slight chance 
for thunderstorms mainly over higher terrain and eastern plains. 

There will be a stronger westerly flow moving across much of the 
western U.S. and Colorado for Thursday and Friday and this will 
bring in much drier air to the region. There is also a strong 120kt 
upper jet which will be draped across the northern Rockies 
through the end of the week. This dry, westerly flow will keep a 
downslope component to the lee of the Rockies and result in 
warming temperatures and dry conditions. 700mb temperatures will 
approach the +20c mark which will push high temperatures in the 
upper 90s to around 100 degrees for Thursday and especially on 
Friday. Strong mid level inversion will keep thunderstorm activity
capped for both days. 

The hot and dry conditions will also result in an increase in fire 
danger with low humidities and some gusty winds in the mountains and 
nearby plains, especially on Wednesday. At this time land 
managers have reported fuel status in the mountains on the low 
side for any rapid fire growth.

Some relief is expected over the weekend as a strong upper trof 
moves over the northern Rocky mountain region and swings a cold 
front into northern Colorado late Saturday or early Sunday. This 
will result in cooler temperatures and a better chance for 
thunderstorms by late Saturday afternoon and potentially into 
Sunday. Once the northern trof swings through, high pressure will 
rebuild into the 4 corners and Western Colorado region early next 
week. Should be enough moisture under the ridge for a chance of
late day storms and seasonable temperatures.  


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1043 AM MDT Tue Jul 16 2019

Another round of scattered thunderstorms containing gusty outflow
winds can be expected again. Main time frame for this would be
21Z-23Z, give or take an hour from the west side of Denver
eastward to KDEN. These storms will push east by 00z and will 
likely push outflow out of the east back to the airports, before 
the winds become drainage again by midnight. 




SHORT TERM...Kriederman
LONG TERM...Entrekin