Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 130956
AFDBOU

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

.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 12Z TAFS through 12Z Saturday morning)
Issued at 356 AM MDT Fri Oct 13 2017

Latest GOES-16 satellite imagery shows stratus have developed
pretty much in line with where the high res models said it would:
across the eastern fifth of Colorado, well east of the metro area
airports. The same high res models try to develop stratus (BKN CIG
around 025) on top of or very near KDEN from 11-15Z. GOES-16 is
showing a westward push towards DEN, so will include a tempo
group for the stratus. Otherwise, VFR conditions will prevail
across the airfields through Saturday. There is a good chance a
Denver Cyclone develops west of KDEN and impacts the wind fields
at the metro area TAF sites tomorrow afternoon. ATTM feel winds at
DEN and APA will be E and ENE up to 15 kts through the afternoon
until the cyclone kicks east, weakening winds at APA and DEN
before going to drainage after about 05Z. BJC should see NE winds
until the cyclone spins up, then NNW late evening into the
overnight hours before going to drainage.

&&

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

$$

SHORT TERM...Schlatter
LONG TERM...RJK
AVIATION...Schlatter



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