125
FXUS65 KBOU 280346
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
946 PM MDT Sat May 27 2017

.UPDATE...
Issued at 927 PM MDT Sat May 27 2017

The convection is nearly over for the CWA right now. Current
satellite pictures are showing the upper trough axis moving south
over the northern CWA right now. The water vapor pictures show
decent subsidence on the back side of the axis. Will clean up the
GFE grids in a cosmetic fashion.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 342 PM MDT Sat May 27 2017

Main batch of showers is moving over the Palmer Divide with
moderate rain at times. Additional instability showers are
developing over Larimer and Weld Counties which will travel
southeastward with some more precipitation through the early
evening. Showers should diminish after 6 PM as daytime heating
comes to an end. Drier and more subsident conditions are expected
on Sunday as a little more ridging moves in from the west.
Lingering moisture over the mountains along with heating of the
higher terrain will de-stabilize the airmass over the mountains
with scattered afternoon thunderstorms expected. Afternoon showers
should remain over the mountains, and then dissipate as they move
away from the higher terrain. Temperatures should also be much
warmer, into the lower 70s on the plains.

.LONG TERM...(Sunday night through Saturday)
Issued at 342 PM MDT Sat May 27 2017

An upper level low over the Great Lakes and a ridge over the
western states will produce a northwest flow aloft over Colorado
through Tuesday. A few showers and thunderstorms will linger into
the early Sunday evening over the higher terrain, including the
Cheyenne Ridge and Palmer Divide. A weak push from the north will
bring slightly cooler temperatures for Monday. A slight increase
in moisture will result in a better chance for showers and
thunderstorms. The higher elevations will again see the best
chance for storms as the plains will be somewhat capped. For
Tuesday, another round of afternoon and evening thunderstorms are
expected. Temperatures will warm into the lower to mid 70s across
northeast Colorado. The far northeast plains look too stable for
convection at this time.

For Wednesday, the upper level ridge shifts eastward and is
centered over the Great Basin and Central Rockies. Models showing
a short wave trough under cutting the ridge over the Southern
Rockies. This may increase thunderstorm chances on Wednesday. The
GFS model shows CAPE climbing to 1500 J/kg, but with the ridge
nearby shear may not be that strong. However, will need to watch
Wednesday for a possible severe threat. Expect warmer temperatures
Wednesday with readings in the mid to upper 70s across northeast
Colorado.

On Thursday and Friday, the upper level ridge is forecasted
weaken and shift east of Colorado. The GFS shows a broad trough
moving across the Rockies. Meanwhile, ECMWF has a westerly flow
aloft with a cutoff low slowly moving east across western Texas.
Plan on splitting the difference and go with low pops with
temperatures near normal. If the GFS pans out, it will be cool and
unsettled.

The GFS and ECMWF are in better agreement on Saturday. They show
a ridge moving over the Central Rockies ahead of a trough moving
onto the west coast. This should result in dry conditions and
warmer temperatures.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 927 PM MDT Sat May 27 2017

Models have a bit more west and southwesterly component to the
normal drainage winds at DIA for the overnight. Not sure. It
isn`t easy to buck normal diurnal trends around here. Current TAF
has a wind direction of 230; that`s okay. There will be no ceiling
issues overnight and Sunday.

&&

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

$$

UPDATE.......rjk
SHORT TERM...Dankers
LONG TERM....Meier
AVIATION.....rjk