Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 270224
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
824 PM MDT Thu Apr 26 2018

.UPDATE...
Issued at 820 PM MDT Thu Apr 26 2018

The CWA is virtually cloud-free right now. Satellite pictures
upstream showing clear skies overnight well into Friday
afternoon. Models. The winds are minor across all of the forecast
area at this time. Weaker than normal drainage patterns are
expected overnight. Not much to change on the GFE grids.

&&

.SHORT TERM...(This evening through Friday)
Issued at 225 PM MDT Thu Apr 26 2018

Skies are clearing this afternoon and we should be nearly cloud
free by sunset as airmass continues to dry and stabilize. Winds
will also decrease as surface high pressure drop south across the
High Plains. This should allow for good radiational cooling and
temps dropping into the upper 20s to mid 30s over most of the
plains, and teens/20s in the mountains.

On Friday, the upper level ridge will begin to shift east across
the Rockies, resulting in warmer temperatures under mostly sunny
skies. A couple of models had some weak convection in the Park
County area, but believe this is overdone under the ridge so will
keep the dry forecast in place.

.LONG TERM...(Friday night through Thursday)
Issued at 225 PM MDT Thu Apr 26 2018

Upper level ridging remains in place for early Saturday as the deep,
551 DM closed low spins off the Pacific NW coast. This feature will
progress ESE through the day Saturday bringing upper level flow more
southwesterly Saturday evening. This upper level wind shift combined
with a closed surface low on the plains will help to advect a
North/South oriented band of mid level moisture over the region by
late Saturday. This influx of moisture combined with temperatures in
the mid to upper 70s will help to increase CAPE values into the 300-
400 J/KG range and slightly higher on the NAM. Lapse rates are
decent over the plains with enough deep layer shear to support
isolated to scattered thunderstorms on the plains late Saturday.
Will continue to increase pops during this time with continued
consistency. Model upper air soundings show more of a wind gust
signature than heavy precipitation with an inverted-V structure up
to 600 mb. At this time, thinking main threats will be lightning
with gusty winds up to 35-40 mph. Over the higher terrain
temperatures will support rain with scattered thunderstorms. Chances
of showers will push into early Sunday morning before the increased
moisture lifts out of the area to the NE. Latest temperature
guidance and 700 mb temperatures show consistent values of +10C
which would indicate surface temps approaching 80 degrees F by Sunday
afternoon with 50s to 60s over the high country. Pressure falls
provided by a surface low on the plains will help to pull in warmer
SW winds with some gusting from 20 to 25 mph possible during the
afternoon. These winds could decrease RH values enough to increase
fire danger concerns for portions of the plains. Fuels have been
able to see decent green up with recent snow and rain, however
this is something to watch over the next few days. Currently,
moisture could be high enough over the far NE corner to produce
high instability values and some isolated thunderstorms Sunday
afternoon.

The beginning of next week starts a period of unsettled weather with
and old low pushing various disturbances over the region. The upper
level feature will start over the Pacific NW and progress slowly to
the east keeping CO over WSW flow aloft. This will push a series of
shortwaves over the region. Models do not show moisture increasing
until late Monday/Tuesday so Monday should stay dry with highs in
the 70s. There are increased chances of a wetter period beginning
Tuesday and continuing through mid week with cooling temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 820 PM MDT Thu Apr 26 2018

There will no ceiling issues. Models have week southeasterly
winds for the rest of this evening, then weak south-southwesterly
winds into mid Friday afternoon.

&&

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

$$

UPDATE.......RJK
SHORT TERM...Barjenbruch
LONG TERM....Bowen
AVIATION.....RJK



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