Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 262125
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
325 PM MDT Sun Mar 26 2017

.SHORT TERM...(This evening through Monday)
Issued at 325 PM MDT Sun Mar 26 2017

Upper and surface low has pushed into Kansas this afternoon. Brief
clearing and upslope flow allowed for some convection along the
foothills, which is now pushing east across the urban corridor.
Still could see a weak thunderstorm pop up, most likely south of
I70 near the foothills. Expect this convection to continue east
for the rest of the afternoon and decrease by sunset. Hires models
showing some lasting over Larimer County into the evening, not
seeing a good reason with forecasted winds or any sort of short
wave to support this however. Skies will clear this evening,
though high clouds from the next system will spread over the area,
likely inhibiting any radiational fog from forming. The exception
is over the far northeast corner where southeasterly winds will
advect in areas of fog, likely over Phillips and Sedgwick counties
towards sunrise.

Southwesterly flow aloft ahead of the next system will bring
warmer temperatures Monday. Precipitation is expected to push into
the mountains late morning with snow levels 8000-9000 feet. A few
showers may affect the Palmer Divide before evening, but the rest
of the plains don`t look to moisten up throughout the column for a
mention of showers yet. Southeasterly winds will be increasing as
a surface low deepens along the lee of the Rockies ahead of the
next system pushing into the Great Basin.

.LONG TERM...(Monday night through Sunday)
Issued at 325 PM MDT Sun Mar 26 2017

...Stormy weather pattern in place through the week...

A stronger upper level storm system will drop into the Desert
Southwest Monday night into early Tuesday. Q-G lift ahead of this
system will increase across the forecast area through Monday
evening, so expect showers to become more numerous and lift
northeast across portions of the plains.  There appears to be a
lead short wave associated with this trough and modest theta-e
advection overnight, so an organized area of showers and possibly
an embedded thunderstorm may eventually lift northeast across the
plains overnight. Will continue with the highest PoPs there, while
reducing them later in the night along the Front Range.

On Tuesday and Tuesday night, the models have trended northward
and a little faster again. I don`t anticipate the track being as
far north as the GFS and NAM show considering the speed max
digging down behind the trough axis, but even the ECMWF is
tracking east across northern/central New Mexico, and there is a
broad area of circulation around this low with upslope flow
Tuesday afternoon and night from southeast Wyoming all the way
through eastern Colorado. Precipitation production should be
quite efficient with persistent weak to moderate Q-G lift,
moderate upslope flow, and neutral to slightly unstable lapse
rates. Precipitable water values are also advertised to be close
to be one half inch, or near the 99th percentile for this time of
year. Temperatures have trended colder in the latest runs, which
seems to be common lately. As a result, we will be trending snow
levels downward, with some snow possibly mixing in across the
Denver area on the tail end of this event late Tuesday night or
Wednesday morning. However, not anticipating any accumulation at
this time except over the Palmer Divide roughly south of Castle
Rock. Will continue to monitor this. Mountain and foothill
locations should see several inches of snow, and if the upslope
component strengthens sufficiently we could see 1 foot plus
accumulations. Still a bit early for winter storm watch for the
foothills and mountains at this time.

Drier weather should eventually build from northwest to southeast
across the forecast area in this storm`s wake later Wednesday
into Wednesday night. Thursday should return to near to slightly
above normal temperatures with a short-lived ridge moving in.

The next storm is still expected to move into the Central and
Southern Rockies Friday into Saturday. This storm is advertised to
be colder than the Tuesday to Wednesday storm, bringing potential
for accumulating snow down onto the plains. This storm is still a
long way out and it may dig too far south to significantly affect
our area, but certainly will need to watch this one over the next
few days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 325 PM MDT Sun Mar 26 2017

NNE winds are decreasing with some NWrlys likely from the
convection off the foothills. Ceilings should remain around 5000
through around 00z. Showers will affect the airports through 01z,
with ceilings dropping possibly down to MVFR under the showers.
Hi res shows some instability and convection lasting possibly
through 05-06Z, over the northern urban corridor - think this is
overdone at this point. No sign of thunder, but cannot totally
rule it out, don`t think this will affect any of the airports now.

For tonight, ceilings may linger around 5000 ft through the
evening hours but should rise above 10000 ft around midnight.
Tough call on which direction winds will go to drainage by 06z.

Winds will increase out of the SE Monday afternoon as a surface
low deepens.

&&

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

$$

SHORT TERM...Kriederman
LONG TERM...Barjenbruch
AVIATION...Kriederman



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