Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 202124
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
324 PM MDT Sat May 20 2017

.SHORT TERM...(This evening through Sunday)
Issued at 320 PM MDT Sat May 20 2017

Precipitation over the far northeastern corner of the state from
the departing low has finally ended with clouds decreasing from
west to east. Just enough moisture in the northwesterly flow for
light showers over the mountains and fair weather cumulus over the
plains, expected to clear after sunset. With clearing skies
overnight, temperatures will drop, but not as cold as we saw last
night. Most areas over the plains will stay above freezing, though
some higher areas over the Palmer and Cheyenne ridges may dip
below for a short time. Not a big enough area to issue Freeze
Warnings again overnight.

A shortwave moving toward the state in northwest flow aloft
tonight will bring scattered showers to the northern mountains
after midnight, with accumulations less than an inch expected.
This shortwave will produce a northerly surge over the plains
Sunday to increase moisture, but not cooler temperatures. Expect
scattered rain and snow showers tomorrow across the area, with
snow levels around 9500 feet. A few weak thunderstorms will be
possible as well. Temperatures are expected to warm 5 to 10
degrees, with readings still below normals for this time of year.

.LONG TERM...(Sunday night through Saturday)
Issued at 320 PM MDT Sat May 20 2017

A weak shortwave will drop over Colorado in northwest flow Sunday
night. This should give enough lift to keep clouds and scattered
showers around. Then northerly flow will strengthen on Tuesday as
the deep upper low over the midwest drops southward a bit. This
will bring some cooling aloft and a surge of northerly winds on
the plains along with another batch of showers. Through this time
frame the instability appears limited, so there should be little
or no thunder. Temperatures should be warm enough to keep the snow
above 7000 feet, with some accumulations in the high mountains.

A ridge will shift over the Rockies for Wednesday and Thursday.
This is trending stronger and could give several days of warm and
dry weather. There are hints of a shortwave passing over the
Rockies on Thursday, but most solutions keep the lift and
moisture north of Colorado. We`ll still have some low PoPs in case
this wave is enough to produce some late day showers/storms. A
stronger shortwave may push a larger scale trough axis over or
past us on Saturday. Still some timing/strength variations, but
pretty good agreement on this for so far out. This should bring a
modest cold front across the plains and some lift. Model
consensus is that upper levels will still be rather warm/dry on
Saturday, so it may be more of a plains/nighttime threat, or this
could just lead to increased convection during the day Sunday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 320 PM MDT Sat May 20 2017

VFR conditions expected through Sunday afternoon. Gusty north-
northwesterly winds will begin to decrease after 00z, to return to
a drainage direction overnight. They should return through the
west direction, though some hi-res model runs showing it go
through the east direction. Winds will become light and variable
by 12z before a northerly push tomorrow morning after 15z.
Scattered fair weather cumulus will decrease after sunset. Some
moisture will move in with the northerly push, may produce
scattered low clouds, shown on forecast soundings. Showers are
expected to increase tomorrow after 18z, with ceilings potentially
lowering to ILS under the showers.

&&

.HYDROLOGY...
Issued at 320 PM MDT Sat May 20 2017

Latest river data shows river levels on the South Platte near
Kersey slowly receding but still right at Action stage, so will
keep the Flood Advisory going with flows remaining elevated. Data
also show the crest of the South Platte River has yet to reach
Weldona in Morgan County as well as western Logan County. Flows
are still 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...
None.
&&

$$

SHORT TERM...Kriederman
LONG TERM...Gimmestad
AVIATION...Kriederman
HYDROLOGY...Kriederman


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