Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 290227
AFDBOU

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

.UPDATE...
Issued at 825 PM MDT Sat May 28 2016

Still some decent storms on the plains, mainly in pockets of
untapped air. Activity is decreasing overall. I will need to add
some low pops to the northeast corner for a few hours after
midnight in case the current activity around Greeley persists or
there is the redevelopment that the HRRR has been showing on weak
outflows coming back in from the northeast. Already added in the
evening showers over the mountains but these should be much less
by midnight. Rest of the forecast is looking good.

&&

.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 00Z TAFS through 00Z Sunday evening)
Issued at 825 PM MDT Sat May 28 2016

VFR through Sunday. Still some showers and thunderstorms around
mainly east of Denver for the next couple of hours, but very low
chance of anything affecting the Denver area terminals. Widely
scattered storms expected again late Sunday afternoon with short
lived impacts of heavy rain, small hail, and wind gusts to 40
knots possible with some of the storms.

&&

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

$$

UPDATE...Gimmestad
SHORT TERM...Dankers
LONG TERM...RJK
AVIATION...Gimmestad



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