Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 131612
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1012 AM MDT Fri Oct 13 2017

.UPDATE...
Issued at 1010 AM MDT Fri Oct 13 2017

Post-frontal low-cloud shield covering most of eastern CO this
morning has just in the past hour or two begun to thin and erode
along its edges. HiRes models for some reason have poorly resolved
this shallow blanket of low-level moisture. The upslope gradient
is weak, but apparently still adequate to keep this moisture in
place. The western edge of the low clouds presently lying on a
GLY-to-DIA-to-PUB line. Lowest CIGs generally in the 900-1600 ft
agl range. As temps warm, T-Td spreads will widen and stratus
deck should give way to clear/mostly clear skies. Still counting
on this happening by early this afternoon. Will need to monitor
temp trends next few hours should high temps on the plains need
adjusting.

&&

.SHORT TERM...(Today and tonight)
Issued at 356 AM MDT Fri Oct 13 2017

Dry southwest flow aloft continues across Colorado. The cold front
that moved across the state overnight has cooled temperatures
quite a bit, and the cooling trend will continue with today`s high
temperatures 10-15 degrees cooler across the Plains and 5-7
degrees cooler in mountains.

Tonight the ECMWF is the lone outlier moving a weak shortwave
trough across the far northeast corner of Colorado. RAP, NAM,
GFS, CMC, HRRRX do not generate any precipitation while the ECMWF
generates a few hours of weak rain showers. Kept low (15-20%)
PoPs from Phillips and Sedgwick Counties just after midnight
tonight but expect the chances to drop with the next run of
models. Overnight lows will be seasonal for mid-October.

.LONG TERM...(Saturday through Thursday)
Issued at 356 AM MDT Fri Oct 13 2017

Models show a southwesterly jet maximum over the forecast area on
Saturday as an upper trough will push eastward across Colorado
through the day into the evening. The upper axis of the trough is
over the eastern border by 06Z Saturday night. The flow aloft
behind the trough is 50-70 knot west-northwesterly winds late
Saturday night and Sunday. The flow aloft remains west-
northwesterly Sunday and Sunday night with an upper ridge moving
our way from the west. The synoptic scale energy ahead for the
trough is not very strong on the QG Omega fields with better
energy to our north over Wyoming. Downward motion is indicated
Saturday night into Sunday morning, with benign vertical velocity
the rest of Sunday and Sunday night. The low level wind and
pressure fields have fairly strong northwesterly winds move into
the CWA on Saturday in conjunction with the passing upper trough.
The strong north-northwesterly boundary layer winds decrease
through the evening Saturday. More normal diurnal trends are
progged Sunday and Sunday night; wind-wise. Concerning moisture,
there is little bit with Saturday`s trough, mostly in the mid
levels, but pretty insignificant. Saturday night through Sunday
night look quite dry, perhaps a bit of cirrus Sunday night. The
QPF fields show a tad of measurable precipitation over the
northern border of the CWA on Saturday. The rest of time there is
nothing. Will leave in the 10-30% pops for the northwesterly
corner of the CWA on Saturday; otherwise no pops. For
temperatures, Saturday`s highs look to be 6-12 C colder than
today`s highs. Sunday`s readings warm up 6-9 C from Saturday`s.
For the later days, Monday through Thursday, models have upper
ridging and flat upper ridging in around Colorado all four days.
It is dry with slight above normal temperatures all four days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1010 AM MDT Fri Oct 13 2017

ILS Ceiling at KDEN has been terribly slow to erode this morning.
Finally detecting clearing over and around KDEN according to GOES
satellite imagery. Ground obs also indicating a rise in the cloud
bases over the airport. This trend should continue with VFR CIG
expected at KDEN by 18z, if not before. Otherwise a light east-
southeast wind at Denver area air terminals will continue for the
remainder of today, then gradually transition to a light south-
southwest wind after sunset under a clear/mostly clear sky.


&&

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

$$

UPDATE...Baker
SHORT TERM...Schlatter
LONG TERM...RJK
AVIATION...Baker


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