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Area Forecast Discussion (AFD)

Issued by Denver/Boulder, CO (BOU)

FXUS65 KBOU 221056

Area Forecast Discussion
National Weather Service Denver/Boulder CO
456 AM MDT Sat Jun 22 2019

.SHORT TERM...(Today and tonight)
Issued at 456 AM MDT Sat Jun 22 2019

Welcome to Colorado's Summer 2019. A late season upper level storm
system will be moving across the state today and tonight with
temperatures aloft cold enough to produce accumulating snowfall in
the mountains. On the plains, a moist airmass is in place, being
held over northeast Colorado by easterly and northeast winds
circulating around a surface low over southeast Colorado and
northern New Mexico. The approaching upper level trough is
providing abundant dynamic forcing for ascent which will result in
periods of rain showers, especially through the afternoon and
evening. High temperatures on the plains will only be in the 60s,
and that will be while it is not raining. Temperatures may remain
in the 50s if rainfall is widespread and persistent enough.
Mountains temperatures will only be in the 30s to 40s, allowing
for snow to accumulate above 10,000 feet. A Winter Weather
Advisory will remain in effect for most of the north central
Colorado mountains through tonight. Over Rabbit Ears Pass and in
the Park and Gore ranges, it appears that drier air will begin
moving in later today, so the Advisory for that zone will be
allowed to expire at 6 AM this morning.  

Back on the plains this afternoon, as the rainfall is expected to
become widespread, elevated instability above the low levels could
lead to some embedded thunderstorm activity. This will enhance
rainfall amounts locally and produce gusty winds in the vicinity
of the embedded heavier showers. The HRRR has been indicating that
one or two of the embedded thunderstorms could become quite strong
as they progress across the plains in the late afternoon. These
could produce hail up to one-half or three-quarters of an inch,
despite temperatures being so cool.  

The HRRR models do not show much precipitation over the plains
after midnight, but other short range models do not bring any
drying to the region until later tomorrow. For the time being,
will not be too anxious to clear precipitation out of the 
forecast area. 

.LONG TERM...(Sunday through Friday)
Issued at 456 AM MDT Sat Jun 22 2019

Highlights include one more cool and showery day on Sunday 
followed by a significant warming and drying trend through the 
rest of the week. 

The upper level trof will move across Colorado on Sunday and then 
into the central plains on Sunday night and Monday. There is still 
moderate upward ascent as noted on layered QG fields on Sunday 
morning, then significant subsidence moves in during the late 
afternoon and extending through Sunday night. 700mb temperatures 
only around +2c, so again temperatures will only be in the upper 
50s and 60s across lower elevations. Showers will diminish Sunday 
evening followed by clearing skies and a chilly night with 
readings in the 40s plains. 

For Monday, Colorado will be under a mainly dry moderate northwest 
flow pattern.  Mid level warming expected to cap thunderstorm 
development with 700mb temperatures soar to +11c but could see
some isolated high based showers over higher terrain.  This will 
bring temperatures back to around 80 degrees. On Tuesday, the high
pressure ridge will be over Colorado with the flow becoming more 

From Wednesday through Friday, a strong low pressure system will be 
over the Pacific Northwest which will increase the southwest flow
aloft over Colorado and building high pressure back into the 
desert southwest. Afternoon high temperatures will be approaching 
90 degrees on Thursday and Friday with summer in full swing. 
Moisture will be limited, with mainly isolated, high based showers
and storms expected during the late afternoon/evening hours.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 456 AM MDT Sat Jun 22 2019

Ceilings will be mostly MVFR through the day but could drop to IFR
during heavier precipitation, especially during the afternoon and
evening hours. The airmass across eastern Colorado is quite moist
with easterly flow at low levels which will hold moisture against
the foothills. An upper level jet stream and trough will be 
moving over the region, providing the dynamic forcing necessary to
produce periods of rain across northeast Colorado through the 
next 24 hours. Isolated thunderstorms will also be possible at 
times due to an elevated unstable airmass above the cool low 
levels. Winds will be light most of the day, but wind gusts may
accompany the embedded thunderstorm activity. Gusts into the 20s
will be possible. 


Winter Weather Advisory until 6 AM MDT Sunday for COZ033-034.

Winter Weather Advisory until 6 AM MDT early this morning for 



SHORT TERM...Dankers
LONG TERM...Entrekin