Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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424
FXUS65 KBOU 241602
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1002 AM MDT Sat Jun 24 2017

.UPDATE...
Issued at 1002 AM MDT Sat Jun 24 2017

A stable and moist airmass continues to lay over the eastern
plains of the state. A Denver cyclone is helping to keep lower
clouds and hazy conditions over the urban corridor while the high
country remains dry under the upper level ridging. ACARS soundings
show the stable airmass very well, up to about 680mb. Still
expecting a slight chance of showers and a weak thunderstorm or
two over the higher terrain south of I70 later this afternoon into
the early evening. High surface pressure over the Great Plains
will try to keep the airmass over the plains stable in upslope
flow, though breaks in the clouds may allow for just enough
heating later today to reach convective temperatures. Also, a weak
wave currently over WY/SD/NE state lines is progged to produce
another northeasterly surge into the area up to 700mb near 00z. Last
several runs of the HRRR and experimental HRRR show this occurring
with some convection starting over the foothills of Larimer County
and pushing its way east over Weld County into the early evening
hours. Will watch the evolution of the shortwave as well as the
ACARS soundings for changes in the strength of the inversion to
see if we need to add thunder to the northern urban corridor and
plains.



&&

.SHORT TERM...(Today and tonight)
Issued at 307 AM MDT Sat Jun 24 2017

An upper level ridge over the Desert Southwest and a large trough
over the Great Lakes will produce a northwest flow aloft today.
The airmass temperature doesn`t change much today, but more sun
will result in warmer high temperatures. Cross sections show the
airmass is moist at 5000 to 10000 feet, so expect periods of
clouds, especially this evening when models show it should cloud
up again. Isolated storms will be possible along the Front Range
foothills and mountains and also along the Palmer Divide. West of
the divide will be too dry and stable while the plains remain too
stable for convection. If storms form, they are expected to be
weak and produce gusty winds to 40 mph and light rain.

Cross sections show it should be mostly cloudy this evening with
clearing after midnight. If skies clear some as planned,
overnight lows will drop into the upper 40s to lower 50s across
northeast Colorado. Any convection should quickly die off this
evening as the airmass stabilizes.

.LONG TERM...(Sunday through Friday)
Issued at 307 AM MDT Sat Jun 24 2017

On Sunday upper level high pressure will be centered over southern
Arizona...with an upper level trough of low pressure covering much
of the central and eastern United States. Colorado will remain under
the influence of a weak to moderate northwest flow aloft. Weak
upslope flow will continue from the surface up to around 700
mb...which will result in another day with below normal temperatures
on the plains. The cool stable airmass will inhibit the formation of
showers and storms across the northeast plains. However...isolated
to scattered afternoon and evening showers and storms will be
possible over the higher terrain where greater instability exists.

Temperatures are expected to warm to near normal values on Monday
as upper level high pressure builds over the Rocky Mountain Region.
There will be just enough residual moisture combined with daytime
heating to produce a few late afternoon and early evening showers
and storms over the higher terrain mainly south of Interstate 70.

On Tuesday...a flat upper trough moving into the western United
States is forecasted to push the upper ridge eastward into the
central plains states. This will allow a westerly flow aloft to set
up over Colorado. This pattern will produce a downslope flow along
the Front Range Urban Corridor...resulting in hot and dry
conditions. Further to the east across the plains...more available
moisture combined with an upper level disturbance may produce a few
afternoon and early evening thunderstorms.

On Wednesday...a weak cool front is expected to bring slightly
cooler temperatures to the region...with mostly dry conditions due
to a dry and stable airmass.

Thursday and Friday...an upper level trough of low pressure and a
couple of associated cold fronts should result in cooler
temperatures and a better chance for precipitation...especially
across the far northeastern plains.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1002 AM MDT Sat Jun 24 2017

MVFR ceilings continue to hold on over BJC and other area airports
due to the Denver Cyclone, with ceilings elsewhere improving to
VFR. Forecast soundings show ceilings hanging around the 4000-6000
feet through the day, likely scattered to broken at times through
the day, rising in height further this evening.

Isolated thunderstorms are expected to form over the higher
terrain west of the Denver area and also to the south of the
Denver area.

Winds are expected to prevail out of the northeast through most of
the day, east by 03Z then southerly after 06Z.

&&

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

$$

UPDATE...Kriederman
SHORT TERM...Meier
LONG TERM...Kalina
AVIATION...Kriederman



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