Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 172053

Area Forecast Discussion
National Weather Service Denver/Boulder CO
253 PM MDT Sun Oct 17 2021

.SHORT TERM...(This evening through Monday)
Issued at 235 PM MDT Sun Oct 17 2021

Mid to upper level moisture and cloud cover will increase tonight
as the ridge moves east and the next trough comes on shore to the
west. Overnight lows should be a few degrees warmer tonight
coming off the warmer high and with scattered overnight clouds.
The low lying areas will still see strong radiational cooling and
inversions which break in the early morning.

There will be an increasing southwesterly flow aloft tomorrow as
the trough moves over the Great Basin. Temperatures should be a
few degrees cooler than those today but still quite warm, in the
70s across the plains and 50s and 60s in the high country. It will
be breezy on the plains in the afternoon, with some areas seeing
peak gusts of 20 to 25 mph. Warm, dry and breezy conditions will
mean another afternoon of elevated fire weather conditions for the
eastern Palmer Divide and adjacent plains mainly of Elbert and
Lincoln Counties. The threat should be mitigated by higher
humidity in the 15 to 20 percent range.

.LONG TERM...(Monday night through Sunday)
Issued at 252 PM MDT Sun Oct 17 2021

Models have an upper closed low moving eastward across the
northern CWA late Monday night through early Tuesday evening.
Fairly strong northwesterly flow aloft dominates Tuesday night.
Upper ridging moves back into the CWA Wednesday and Wednesday
night with decreasing zonal flow aloft. The QG Omega fields show
upward vertical velocity for the CWA Monday night into Tuesday
morning, with the best energy from the closed low north of the
forecast area. There is pretty strong subsidence indicated for the
rest of Tuesday into the evening hours. There is a pretty decent
low level pressure gradient for Tuesday. That along with the
subsidence and a bit of mountain wave set up, will make sure there
are decent downsloping wind speeds in the grids.

Looking at the moisture, the northern half of the CWA, gets the
lion`s share with upper trough Monday night into Tuesday night. The
moisture isn`t very deep. There should be some orographic help in
the mountains from the divide westward. Snowfall amounts do not
look significant all the same. The snow should last in the high
mountains from midnight Monday night to midnight Tuesday night.
No highlights. The downsloping and location of the upper low will
preclude pops for the plains with this event. There is a cold
front that moves across, west to east, Monday night. It is pretty
much a bora type front. For temperatures, Tuesday`s highs are 6-9
C colder than Monday`s highs. Wednesday readings warm up 3-6 C.

For the later days, Thursday through Sunday, upper ridging, zonal
flow and a dry airmass will rule Thursday through Saturday. By
Sunday, the flow aloft is supposed to increase with some broad
weak mean upper troughing. Some of the models point to minor pops
for the mountains.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 235 PM MDT Sun Oct 17 2021

Expect VFR conditions through the TAF period. Skies will remain
mostly clear through this afternoon, increasing to scattered cloud
cover this evening and overnight. Easterly winds this afternoon
may turn northeasterly briefly before coming around southeasterly
in the evening then to drainage tonight through tomorrow morning.
Breezy southwesterly winds with peak gusts up to around 20 knots
are likely tomorrow afternoon.




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