Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 200954
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
354 AM MDT Sat May 20 2017

.SHORT TERM...(Today and tonight)
Issued at 354 AM MDT Sat May 20 2017

Upper level low near the Colorado/Kansas/Nebraska tri-state
intersection will move slowly east/northeast across Nebraska
today, and then into the upper Midwest tonight.

Light rain and snow on the back side of the low across the
northeast Colorado plains early this morning will gradually
diminish as subsidence moves in. In the mountains, some shallow
moisture is trapped there with a few light snow showers.
Meanwhile, dry conditions prevail along the Front Range including
the I-25 corridor, and stratus deck is gradually eroding with
developing west/northwest flow.

Daytime heating may bring a few showers or an isolated
thunderstorm back to the mountains this afternoon, and then
approach of the next weak wave and mid level moisture could keep
a stray shower or two in the high country overnight. Otherwise
look for sunshine to return today with warmer temperatures, but
they`re still a good 10-15 degrees below normal. Temperatures are
near freezing early this morning along the Front Range. Only
partial clearing is limiting radiational cooling, but it is just
cold enough to keep the freeze warning in place til 8 AM.

.LONG TERM...(Sunday through Friday)
Issued at 354 AM MDT Sat May 20 2017

A weak upper level trough in nw flow aloft will move across the area
Sun aftn thru Sun night. There is some wk mid lvl ascent with
this feature with lapse rates in the 6-7 c/km range. The ECMWF is
a bit slower with the trough passage as compared to the GFS.
Overall should see an increasing chc of showers over the higher
terrain by aftn with at least a slight chc across the plains. By
Sun evening will see snow showers in the mtns with a chc of
showers across nern CO. If the trough is slower as shown by ECWMF
then shower activity may continue thru late Sun night. As for
highs readings will rise into the lower to mid 60s across nern CO.

On Mon another upper level trough embedded in nnw flow aloft will
move across the area late in the aftn thru Mon night.  Once again
there will be some mid lvl ascent with this feature with lapse rates
in the 7-8 c/km range.  In addition there will be a cold fnt moving
across the plains which will enhance upslope flow Mon evening.  Thus
will see a good chc of snow showers in the mtns as the upper level
trough moves across with a chc of showers and a few storms across
the plains.  There could be period of steadier pcpn Mon evening in
an nr the foothills. As for highs readings will be in the lower
to mid 60s across the plains.

For Tue the flow aloft will become more nly.  There will still be
some moisture embedded in the flow so will keep in a chc of showers
in the mtns with a slight chc across the plains.  Temperatures will
be a few degrees cooler across nern CO with readings in the upper
50s to lower 60s.

On Wed drier air in wnw flow aloft will be over the area so no pcpn
is expected.  Temps will be warmer as well with readings rising in
the lower to mid 70s across the plains.  For Thu the flow aloft will
become more wsw as an upper level trough develops over the Pacific
NW.  Both the ECWMF and GFS show some moisture embedded in the flow
with decent lapse rates so will mention a slight chc of storms
mainly over the higher terrain. Temperatures will continue to rise
with readings in the 75 to 80 degree range over nern CO.

On Fri the upper level trough will remain over the nwrn US with wsw
flow aloft remaining over the area. Low lvl moisture will increase
over the plains with increasing instability so will mention a
slight chc of storms. Across the higher terrain drier air is fcst
so will keep pops on the low side. Temperatures will be similar to
Thu.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 354 AM MDT Sat May 20 2017

Stratus deck is eroding to the east so VFR conditions are expected
to prevail through the period. Only a slight chance of brief
patchy fog developing north of the Denver metro area airports 12Z-
14Z. Light winds this morning should transition to more northerly
flow around 10 knots 18Z-00Z, and then back to normal
south/southwest winds after 00Z.

&&

.HYDROLOGY...
Issued at 354 AM MDT Sat May 20 2017

Latest river data shows the Cache La Poudre river near Greeley
crested yesterday. Flows will remain elevated but below advisory
stage, so we have cancelled that section of the advisory. The
South Platte has crested near Greeley and is slowly receding.
Flows continue to rise downstream toward Morgan county, and are
expected to reach advisory levels there so no changes to the
existing Flood Advisory for those segments of the South Platte
through the weekend.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 8 AM MDT this morning for COZ038>043.

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...RPK
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch



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