Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 191645
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1045 AM MDT Sat Aug 19 2017

.UPDATE...
Issued at 1040 AM MDT Sat Aug 19 2017

No updates planned at this time. Latest HRRR still develops some
weak showers and thunderstorms late this afternoon, primarily
along and south of the Interstate 70 corridor.

&&

.SHORT TERM...(Today and tonight)
Issued at 347 AM MDT Sat Aug 19 2017

Relatively dry and weak zonal flow will remain in place through
tonight. There is some slight destabilization noted on the
forecast soundings, so the going low PoPs mostly in the mountains
and Palmer Divide area seem reasonable. There will also likely be
a weak surface convergence zone over the far eastern plains
associated with the lee trough, and perhaps just enough moisture
convergence along this line to pop a couple late afternoon storms
as well. Showers and storms will be high based today producing
gusty outflow winds and only light rainfall.

Temperatures will warm about 2-3C across the plains from
yesterday, due to the dry westerly flow aloft. Any evening
convection should dissipate by or shortly after dark with the loss
of daytime heating and no synoptic scale support. Lows tonight
will be near seasonal norms.

.LONG TERM...(Sunday through Friday)
Issued at 347 AM MDT Sat Aug 19 2017

Flow aloft will turn more south of westerly Sunday for a slight increase
in subtropical moisture. Convection will fire off again over the
high terrain with a slight chance over the Palmer Divide and far
eastern plains. Main impacts will be gusty outflow winds and some
possible hail as shear begins to increase. Temperatures will be
similar to slightly cooler than today`s readings as more cloud
cover will be moving in.

Sunday night, models continue to hint at possible clouds
overnight as weak upward QG motion dives in from the north and
moisture continues to surge up from the southwest. The GFS
continues to be the dries while the NAM, GEM and EC show at least
partly cloudy skies with some hints of light precipitation. Not
trusting any of the precipitation at this point, but with the
upward QG and increase in moisture, do not see a reason not to go
at least partly cloudy early Monday morning. A shortwave will be
pushing south along the northern Rockies on Monday which will kick
off storms over the high terrain and north of the state in the
early afternoon, this could also help some clouds remain in the
forecast through the eclipse viewing time - not expecting totally
clear skies at this time. Stronger storms may form over the far
northeastern corner of the state, where better instability and
shear exist. A cold front will be trailing south that evening,
keeping a chance of storms and showers through most of the night,
especially along and east of the Divide.

The front will drop temperatures below seasonal normals Tuesday
and Wednesday as high surface pressure keeps weak upslope flow
into the area, with increasing coverage of storms. Another
shortwave moving in from the Great Basin Thursday will turn flow
aloft more southerly and bring another surge of subtropical
moisture for another increase in storm coverage, especially
Thursday, possibly into Friday. Then flow will return to zonal as
the upper ridge builds back over the desert southwest, for warmer
and drier weather for the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1040 AM MDT Sat Aug 19 2017

VFR conditions will persist through Sunday. There should be some
high based convection but for the most part this should stay
confined to areas south and west of KDEN. However, there`s still
about a 20% chance of gusty outflow winds to 30 knots. Otherwise
fairly normal and light diurnal winds should prevail at speeds 10
knots or less.

&&

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

$$

UPDATE...Cooper
SHORT TERM...Barjenbruch
LONG TERM...Kriederman
AVIATION...Cooper



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