Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 210330
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
930 PM MDT Sun May 20 2018

.UPDATE...
Issued at 930 PM MDT Sun May 20 2018

The dry up has begun. Cloud ceilings over the plains have been
rising the past few hours, and in many areas the first time above
6000 feet agl in days. The few remaining light rain showers
hanging over and along the Front Range may not have much longer to
live with drier air spreading down from foothills and Palmer
Divide. This will also be a notable absence of fog tonight,
except perhaps in low lying areas such as along the South Platte
River north of Denver. Even there, the pockets of fog that manage
to form should be shallow and thin, and dissipate not long after
sunrise. Therefore, expect gradual clearing with an equally
gradual reduction in temperatures overnight. Some of the HiRes
models also indicate a gradual speed increase in the south-
southwest winds on and near the Palmer Divide after midnight.
Should these winds develop, overnight temperatures in this area
will get a healthy head start on the big warm up on the way
tomorrow.


&&

.SHORT TERM...(This evening through Monday)
Issued at 338 PM MDT Sun May 20 2018

Current satellite pictures are showing the low cloudiness hanging
on over the foothills and the western half of the plains. Area
radars indicate isolated convective coverage over mountains and
high valleys. The low level wind field is weak with mainly an
upslope component right now. Current ACARS soundings indicate a
significant stable layer from 730 to 680 MB. Models have upper
ridging over the Colorado tonight and Monday with 30 to 50 knot
southwesterly jet level flow. The QG Omega fields show benign
energy in the synoptic scale tonight and Monday. The low level
winds should return to normal drainage patterns overnight.
Monday`s winds will likely have some southwesterly direction
thrown in by afternoon. For moisture, Monday`s dew point progs
show 30s F and mid 40s F in most areas with some 50s F over the
far eastern border areas. The CAPE fields show minimum values over
the high country only this evening. For Monday, there is some
CAPE over the all the CWA by afternoon, with the far eastern
border showing values around 2000 J/kg. Forecast soundings have a
cap in place over the plains Monday afternoon. The QPF fields
show limited measurable rainfall over the mountains and foothills
this evening, then a tad over the southwestern quarter of the CWA
Monday afternoon. Will go with "scattered" pops over the mountains
and foothills this evening. For Monday afternoon will go with
"scattered" pops over the high mountains only, with 0-20%
elsewhere.

.LONG TERM...(Monday night through Sunday)
Issued at 338 PM MDT Sun May 20 2018

Models continue to show an upcoming week with warmer temperatures
and a repetitive cycle of morning sunshine followed by afternoon
showers and thunderstorms. At the upper levels, an upper low is
forecast to develop over southern California that will remain in
place through Wednesday morning. Over Colorado, the southwest flow
aloft will transport moisture aloft into the region. At lower
levels, a broad area of low pressure will remain in place over
Colorado and Utah which will draw Gulf of Mexico moisture into the
region by southerly flow and nocturnal jets. Temperatures are
forecast to climb into the lower 80s each day with dew points in
the 40s. This should provide enough energy each afternoon to de-
stabilize the airmass and produce isolated to scattered
thunderstorm activity. Mountain areas should see the shower
activity first each day due to strong heating over the elevated
terrain. For the latter half of the week, upper ridging over
Colorado is forecast to become a little stronger as a new upper
level low forms off the California coast. The GFS indicates a weak
cold front moving into Colorado that will switch the flow to
northerly. The ECMWF does not share this solution, but continues
the moist southerly flow over the eastern plains. The end result
will be the same either way, as daytime heating leads to more
afternoon shower activity. Flow aloft will not be strong through
the week, so no organized strong thunderstorms are expected. Just
brief periods of light to moderate rain from thunderstorms that
pulse up and down through the afternoon and evening hours. The
warm temperatures will keep the Spring runoff of the mountain
snowpack going, but without extreme heat, no hydro problems are
expected.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 930 PM MDT Sun May 20 2018

Drier air has begun to spread over the Denver Metro area and as a
result, the spotty light rain showers have dissipated for the most
part, and cloud ceilings continue to quickly rise. This trend
should continue overnight with a slightly enhanced south-
southwest drainage wind developing after midnight. Tomorrow will
be much drier and warmer, and with noticeably less cloud cover.
Although, there is a slight chance that a gusty light rain
shower or two could drift off the Front Range late in the
afternoon.


&&

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

$$

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



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