Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 241008

Area Forecast Discussion
National Weather Service Denver/Boulder CO
408 AM MDT Mon Jul 24 2017

.SHORT TERM...(Today and tonight)
Issued at 400 AM MDT Mon Jul 24 2017

Broad high pressure anchored over much of Colorado and Utah with a
light westerly flow aloft. Precipitable water trends are still
running slightly lower then this time yesterday. Appears there
will be an up tick in moisture by tonight as the high pressure
centered shifts a bit across New Mexico and Texas which will
deliver more moisture into Colorado from the south and southwest.
Forecast models showing PW trends increasing to just over an inch
over the Front Range by this evening. Much of this moisture is
still in the mid and upper levels with inverted v type soundings
by late afternoon. With the stronger west to southwest flow
tonight expect gusty winds with the showers over the urban
corridor and plains. Enough moisture in the mountains for heavy
rain and gusty winds with storms.

Temperatures will be even warmer over the plains today with
readings in the mid to upper 90s as 700mb temperatures climb to
+17c. Deeper moisture moving into the mountains later tonight so
would expect some light rain showers redeveloping towards morning.

.LONG TERM...(Tuesday through Sunday)
Issued at 400 AM MDT Mon Jul 24 2017

The mid-summer monsoon machine will continue to drive subtropical
moisture northward over the Desert Southwest and periodically up
across Colorado during the extended period. Most noteworthy is the
abnormally moist and unstable air expected to pool over
Arizona/srn California/srn Nevada in advance of a shortwave
trough pinwheeling around the deep upper low off the central
California coast. Abnormally high 700mb spec humidity values at
the core of this monsoon moisture anywhere from 10 to 13 g/kg.
Models show this disturbance and moisture spreading newrd over
swrn Colorado by late tonight and up across north-central/
northeast Colorado during the afternoon and evening on Tuesday.
Unstable mid-level lapse rates, PW values over an inch and weak
QG forcing generated by the shortwave should have little problem
producing scattered to numerous showers/t-storms capable of
locally heavy rainfall in the high country during this 24 hour
period. East of the mountains, PW will also rise, however the bulk
of the moisture will be concentrated at mid and upper levels.
And, with an increase in mid and high cloud cover, CAPES on the
plains should stay on the low side. Therefore the threat of severe
weather appears low. However, with inverted-V soundings, could
see storms on the plains producing gusty outflow winds to 50 mph
during the afternoon and early evening hours on Tuesday.

On Wednesday, models show the shortwave trough and its moisture
rich air moving east of the state. In its wake, should see the
drying swly bndry layer flow of the past couple of days turning
northerly. This wind shift will lower PWs east of the mtns as
well as lower daytime temperatures by as much as 8-10 deg f.
Expect precip chances on the plains to drop off with arrival of
drier air from Wyoming, whereas shower/storm chances will remain
elevated in the high country with solar heating and moisture
hanging around. Brief heavy rain again a possibility for mtn and
high valley locations Wednesday afternoon and evening.

Thursday and beyond, the upper ridge anchored over the southern
Great Plains during the first half of the week is forecast to
migrate westward over the Rocky Mtn states on Wednesday and be
situated over Great Basin and Desert Southwest by the end of the
week. This large scale pattern shift is expected to reduce storm
chances across the CWA, particularly east of the mtns. A
persistent nwly flow will also keep temperatures near to below
average through Sunday.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 400 AM MDT Mon Jul 24 2017

Like yesterday, expect much of the thunderstorms to remain over
the mountains, but outflow boundaries may kick off additional
isolated storms over the terminals by late in the day. Overall
coverage still looks more isolated so won`t mention TS in the TAFS
but could see some outflow induced gusty winds. Brisk southerly
winds will shift northeast through east during the afternoon.


Issued at 400 AM MDT Mon Jul 24 2017

Storms moving east-northeast over the mtn and high valleys of
n-central Colorado on Tuesday will have the potential to produce
locally heavy rainfall and wind gusts to 45 mph. Some storms
during the afternoon hours could produce over an inch of rain in
under 30 minute, which could result in localized flash flooding in
sloped terrain. East of the mtns the threat of heavy rainfall will
not be as great. Mountain areas could again see some storms late
in the day on Wednesday produce brief heavy rainfall, though total
storm amounts are not expected to be as great.




SHORT TERM...Entrekin
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