Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 212136
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
336 PM MDT Fri Apr 21 2017

.SHORT TERM...(This evening through Saturday)
Issued at 336 PM MDT Fri Apr 21 2017

Current satellite and radar analysis shows mid level circulation
spinning southeast across southern Washington county late this
afternoon. Subsidence is building in behind it, with
precipitation intensity and coverage generally diminishing. The
exception is the convective development occurring in/near the
Front Range but even here intensity has been limited by northwest
flow a couple thousand feet above the ground. This downslope
component however is expected to decrease through the evening with
a more of a northeasterly push. As a result, should see further
shower development through early evening along the Front Range.
Snow level is already lower than advertised by most model data,
with snow still occurring in the middle of the afternoon from
Cheyenne to Pine Bluffs and southward just across the Wyoming
border. Foothill locations should see amounts in the 1-4 inch
range through tonight, with perhaps up to 6 inches in a few spots
that see more persistent heavier convective showers. Right now
that favors the foothills north of I-70, and most likely toward
the Wyoming border as another convective area is sinking southeast
with another weak short wave. That wave is indicated to reach the
northern portions of the forecast area late this evening, so may
see showers linger overnight with a few more spreading onto the
plains. Overall these should be light, but that also means lower
elevations will see a chance of some snow including the Denver
metro area. At this time, we do not anticipate more than a dusting
possible on grassy surfaces, and a worst case scenario of an
inch.

On Saturday, expect any lingering morning rain and snow showers
to dissipate with stronger subsidence finally building in. Can`t
rule out a few convective showers in/near the Front Range
Foothills through the afternoon, but overall expect some
moderation and drying on Saturday. High temperatures will be about
5 degrees below normal.

.LONG TERM...(Saturday night through Friday)
Issued at 336 PM MDT Fri Apr 21 2017

The forecast period will start out dry and warm from Sunday into
Monday as an upper ridge builds over the Great Basin then moves
over Colorado. However, the ridge will be developing in the
larger context of a very progressive upper level flow pattern
that is going to dominate weather over the western U.S. through
the latter part of next week. As soon as the ridge develops it
will be moving out, with each of the mid-range models showing the
positively tilted ridge axis over eastern Kansas and Missouri by
Sunday evening. Colorado will be under southwesterly flow aloft
through Monday with increasing moisture through the day. Scattered
snow showers should be moving into the northern mountains by
Monday afternoon. The rest of the week is forecast to have brisk
westerly flow across the western half of the country, including
Colorado. Pacific moisture will be embedded in the westerly flow,
and next week will feature periods of light snow continuing in the
mountains. On the plains, short wave impulses embedded in the flow
pattern will likely kick off diurnal showers each day. It is
difficult to pinpoint whether any day is preferred over any other.
This will also keep temperatures around normal through the week.

By the end of the week, the ECMWF and GFS present two different
solutions as some sort of trough amplifies over the intermountain
west. The main feature of this is going to be cooler temperatures
and a better chance at a more organized storm system next Friday
or Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 336 PM MDT Fri Apr 21 2017

MVFR ceilings are filling in and overall expect those to hold
through most of the night with a more easterly upslope component.
Local IFR ceilings possible with clouds generally lowering toward
the foothills. Fog and terrain obscurations are expected in the
foothills with the cloud deck running into the ground. But just a
slight chance we would see fog develop on the plains and Denver
Metro area airports as the stratus deck should be too persistent
and thick to allow for much radiational cooling. Clouds are
expected to gradually lift and break up through 18Z-21Z Saturday
with daytime mixing.

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Dankers
AVIATION...Barjenbruch



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