Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 282121
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
321 PM MDT SAT MAY 28 2016

.SHORT TERM...(This evening through Sunday)
Issued at 321 PM MDT Sat May 28 2016

Have seen isolated-scattered showers and a few thunderstorms form
over the mountains and drift eastward out onto the plains over the
past couple hours. Should continue seeing this activity for a few
more hours. Brief heavy rains and small hail will be the main
threats through the early evening. Loss of daytime heating through
the evening will allow showers to come to an end by mid-evening.

Weak westerly flow aloft will continue over the state again on
Sunday, with enough moisture and instability for showers to
develop over the mountains and move over the plains. Model
soundings show CAPE values over 2000 j/kg, so there should be a
bit more strength to the showers that develop. Winds aloft will be
weak, so the threat of locally heavier rain will increase.
Precipitable water values are also forecast to be above .75 inches
late in the afternoon and early evening.

The GFS and ECMWF models are not as wet as the NAM solutions, so
will temper the PoPs back a little bit across the northeast
Colorado plains, in case the shower activity remains in and near
the foothill areas. Otherwise, temperatures will be around
seasonal normals.

.LONG TERM...(Sunday night through Saturday)
Issued at 321 PM MDT Sat May 28 2016

There is weak west-southwesterly flow aloft progged for the
forecast area Sunday night and Monday. By Monday night well into
Tuesday...an upper trough will move into Colorado and the CWA. The
flow aloft stays weak. By 12z Tuesday morning, the upper trough is
through and there is northwesterly flow aloft. There is weak
upward QG motion in the synoptic scale Sunday night into Tuesday
evening, before downward motion moves in by 12z Wednesday morning.
The boundary layer flow will likely adhere to normal diurnal
patterns Sunday night through Monday evening. Models show a decent
cold front with north-northeasterly upslope winds behind it moving
down across the plains and foothills from 06Z to 09Z. The upslope
is progged to continue all day Tuesday and Tuesday night. For
moisture, there is quite a bit over all the CWA through Tuesday
evening, then it decreases overnight. There is fairly decent cape
progged for much of the CWA Sunday evening and late day Monday.
The only decent cape for late day Tuesday is over the mountains
and foothills. The lapse rates are pretty steep much of the time,
except for the plains on Tuesday. It looks somewhat stable behind
the front in the upslope. The best QPF coverage for the CWA is
progged for late day Monday. There are decent amounts of
measurable rainfall in the mountains late day Tuesday as well. for
pops...will go with 30-60%s in the mountains Sunday evening, late
day Monday and late day Tuesday. The plains will have 10-40%s for
those three periods. For temperatures, Monday`s highs are 0-2 C
warmer than Sunday`s highs. Tuesday`s readings are 2-6 C colder
than Monday`s. For the later days, Wednesday through Saturday,
models have northwesterly flow aloft for the forecast area, with
an upper ridge to our west moving towards Colorado. The ridge axis
stays west of our state over Utah through Saturday. The airmass
over the CWA dries out quite a bit and warms up to slightly above
normal temperatures by Friday and Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 321 PM MDT Sat May 28 2016

A few weak rain showers have moved over parts of Denver and it
appears that a couple more showers are about to move over eastern
Boulder and northern Jefferson Counties in the next hour or two.
The threat of any more showers should then be over for the
evening. Southerly winds should prevail overnight and then another
afternoon with a threat of showers will develop again tomorrow.
Flow aloft is once again going to be weak, but with temperatures
a few degrees warmer than today, CAPE values should be higher,
allowing showers and thunderstorms to be a little bit stronger.

&&

.BOU Watches/Warnings/Advisories...
None.
&&

$$

SHORT TERM...Dankers
LONG TERM...RJK
AVIATION...Dankers


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