Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 222145

Area Forecast Discussion
National Weather Service Denver/Boulder CO
345 PM MDT SUN MAY 22 2016

.SHORT TERM...(This evening through Monday)
Issued at 345 PM MDT Sun May 22 2016

Have seen a few showers develop over Larimer County over the past
couple hours, with additional showers expected over the next few
hours. A short wave seems to be embedded in the prevailing
southwest flow which is producing the shower activity across
northwest Colorado and the northern mountains. The HRRR and RAP
models indicate that a band of shower activity related to this
short wave will develop on the plains after 02z. The I-25 corridor
should remain dry, but areast to the east of Fort Morgan should
see an hour or so of shower activity between 02z and 06z. Showers
will move out of the state by 06z with clearing skies overnight. A
weak surge of northerly winds across the plains will follow the
passage of the evening shower activity.

Additional cooling is expected tomorrow as weak northerly flow
continues. More thunderstorm activity is expected over the
mountains tomorrow afternoon as the state remains under southwest
flow aloft and an upper jet moves over the state, bringing a bit
more dynamic forcing than we have had the past couple days. Late
in the afternoon showers are then expected to spread out onto the

.LONG TERM...(Monday night through Sunday)
Issued at 345 PM MDT Sun May 22 2016

A cross CONUS blocking trough-ridge-trough pattern keeps a warm
and relatively dry swly flow over Colorado through mid-week.
Models show a couple of weak mid-level pertabations carried along
in this flow and passing over nern portions of the cwa Monday
evening and again Tuesday afternoon and early evening. Storms
forming on a wind shift line just east of the I-25 corridor is
forecast to shift northeast across weld...Adams and Morgan
counties Monday evening. Sfc based capes and instability may be
sufficient to support a few strong storms capable of small hail...
stg gusty winds and brief heavy rainfall. This storm area will
shift east-northeast with the shortwave passing through the nern
corner of the state during the mid to late evening hours. Models
indicate 3-hour qpf amounts in the 0-20-0.30 inch range out there.
The late Tuesday shortwave appears a bit weaker and farther
north with more of an impact on the northern Front Range and
northern I-25 corridor around Ft. Collins. Brief rainfall land
gusty winds probably main output from these high based cells.

Wednesday looks drier with strong mid-level subsidence..and temps
generally around average with a downslope flow off the Front
Range. Strong diabatic heating should still manage to generate a
few late day showers/t-storms over the high terrain.

Thursday-Friday time wave upper trough passing over
the Great Basin is still progged to makes slow eastward progress
across Colorado during the period. GFS has come into closer
agreement with the European model which has changed little during
the past few runs. Both models as well as the DGEX and Canadian
models all show this trough and its cooler temperatures and
moisture enhancing shower/storm chances across the cwa. Best
chance for measurable precip appears to be late Thursday
afternoon/evening over and along the Front Range and Palmer
Divide...and on the northeast plains Friday afternoon with the
passage of a cold front. Would not rule out a few pockets of heavy
rainfall with rising precipitable water with this system.

By Saturday...models show this trough and front moving out across
the Great Plains and a shortwave upper ridge building over the
state...bring warmer and drier conditions to the area. This
trend continues Sunday with southerly flow and an amplifying


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 345 PM MDT Sun May 22 2016

Northeasterlies are expectred to last a few more hours. Have not
seen too much shower activity over the foothills of Boulder and
Jefferson Counties up to this point, so the idea of a shift to
northwest winds this evening may not be a valid one. A little
later in the evening the idea of surge of north winds is still
advertised by the HRRR and RAP models. A turn to drainage
southerly winds is not expected until near sunrise. Tomorrow
afternoon should see more convective development across the Denver
area as the continuing southwest flow aloft begins transporting
some Pacific moisture over the state.


.BOU Watches/Warnings/Advisories...


SHORT TERM...Dankers
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