Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 240147

Area Forecast Discussion
National Weather Service Denver/Boulder CO
747 PM MDT Thu May 23 2019

Issued at 747 PM MDT Thu May 23 2019

This evening radar and web cameras in the mountains are now
showing some improving conditions moving up from the south. On the
plains, a few areas of showers are also moving from south to
north. Radar data from Grand Junction shows some more shower
activity still heading toward the north central mountains. A back
edge to the showers my be developing over the northern San Juan
mountains which will signal the end to the precipitation. Timing
of the current forecast package seems to be pretty close, with
scattered snow shower activity continuing over the mountains until
about midnight. Similarly, the shower activity on the plains
probably has only a couple more hours to go. On the far eastern
plains, areas of fog have developed with visibilities generally
down to about 2 miles.

With the current forecast advertising the end of rain and snow
showers over the next few hours, the only change this time around
will be to add the areas of fog on the plains. Dry air will be
spreading over the state overnight as the upper low lifts
northward over Wyoming. Sunny skies and warmer temperatures will
usher in the holiday weekend.


.SHORT TERM...(This evening through Friday)
Issued at 225 PM MDT Thu May 23 2019

Upper level low can be seen on water vapor and is moving NNE into
Utah, with increased lift out ahead of it in western and central
Colorado. With the upper jet moving over central Colorado
increasing south to southwesterly winds aloft speeds over the
higher terrain have increased at Berthoud pass and others. The
showers that were in place over western Colorado for most of the
morning are starting to move over the divide and central mountains
as the jet pushes eastward. Snow has started to increase in
intensity across Park and Summit counties with the snow pushing
North and increasing in coverage over the next few hours.
Lightning has been seen in the storms over the west with the
increased lift. This will help with the convective nature of the
snow showers over the higher terrain and could cause a few hours
of reduced visibility and hazardous travel conditions over the
higher mountain passes. Will keep the advisory in place to account
for the increased impacts into the early evening hours. Across
the lower elevations the surface high is gradually lifting to the
NNE with increasing SE winds on the plains. The increased low
level upslope flow will allow for continued light rain and
lowered clouds into the evening hours. With the cooling aloft and
upper jet moving across later this afternoon some increased
showers will be possible after 2 pm for a few hours. By the
evening hours, upper flow will turn more southwesterly in the mid
to lower levels and westerly aloft. This will usher in drier flow
as the upper low pushes North. This will bring an end to the
precipitation across the plains after midnight tonight. Some
lingering snow showers will be possible in the northern mountains
due to moisture and the exiting jet so kept pops over that region.

For Friday, snow will end over the far northern mountains by the
afternoon with continued dry conditions across the plains.
Temperatures will rebound with highs in the upper 60s to lower
70s. Westerly flow will continue across the mountains allowing
enough stability to bring some increased winds to the higher
terrain during the afternoon hours. Some isolated storms will be
possible across the mountains by the afternoon with a mix of rain
and some snow possible over the higher terrain.

.LONG TERM...(Friday night through Thursday)
Issued at 225 PM MDT Thu May 23 2019

For Friday night and Saturday, there will be continued
weak troughiness across Southern California and a downstream
southwest flow aloft over Colorado. This will result in a
generally dry weather pattern with warming temperatures. Synoptic
forcing will be weak subsidence to neutral forcing. 700mb
temperatures will climb to 7-8c by Saturday afternoon and a return
to temperatures in the 70s. The only chance of showers will be
over the far northern mountains, closer proximity to the upstream

By late Saturday and Sunday, a deeper storm system will dive across
southward across California with a continued moderate south to
southwest flow aloft. Thermal ridge will be over Colorado Sunday
afternoon with even warmer temperatures as 700mb temperatures warm
to +11c. Expect an influx of low level moisture on the plains
Saturday night and Sunday and with improving profile could be a
few stronger storms out towards the border areas with Nebraska and

 On Sunday night, the California low begins to move
eastward into the southern Great Basin with increasing moisture
and weak upward QG ascent developing. This could lead to a greater
chance for showers by Sunday evening in the mountains and
possibly over the far northeast plains in proximity to dry line
with better moisture over the central plains.

Colorado weather will become more unsettled again from Monday
through Wednesday as the California low moves across central and
northern Colorado during the Monday night and Tuesday time period
along with a strong upper jet to help provide lift.  Both GFS and
European solutions continue to be similar in the timing and track.
Best chances of showers will be over northern sections of CWA for
locations just north of the upper low. Snow levels will lower down
to around 8000 feet by Tuesday morning with some snow accumulation
again over the higher foothills and mountains.

The synoptic pattern becomes more clouded by midweek with expected
some troughiness will remain over the Great Basin but long range
models showing rather diverse solutions. Drier and warmer again by
late week with just isolated late day showers and storms.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 747 PM MDT Thu May 23 2019

Radar data would indicate that the last of the showers are moving
out of the Denver area at the present time. Drier air will begin
moving up from the south over the next few hours, bringing VFR
ceilings and unrestricted visibilities. Winds should remain out of
the south overnight. Forthcoming TAFs will continue to advertise
optimistic conditions.




LONG TERM...Entrekin
AVIATION...Dankers is the U.S. government's official web portal to all federal, state and local government web resources and services.