Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 150929
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
329 AM MDT Sat Jul 15 2017

.SHORT TERM...(Today and tonight)
Issued at 329 AM MDT Sat Jul 15 2017

East-west shear zone is persisting across Colorado with deep
moisture over the south and shallower moisture capped by warm dry
air aloft over the north. A little eddy in this zone has persisted
for a few days, reinforced by convection each day. This whole
pattern is sliding east now, with the eddy and weak lift
associated with it sliding into southeastern Colorado today.
Models continue to be too aggressive with both any northward
drift of this pattern and the amount of low/mid clouds and
precipitation, especially on the north edge of the deeper
moisture. The NAM has been especially too overdone. We will make
adjustments similar to the last couple of days, keeping the main
area of lift and best chance of heavy rain in southeastern
Colorado, though Lincoln county will be on the edge of this zone
and should have good convective coverage as well. As the eddy
moves east, it could lift the main area of convection into east
central Colorado, still mainly affecting Lincoln county and
perhaps into Washington county as well. Areas further north should
see less organized convection. However, there is increasing low
level moisture in this gradient area so there could be a bit more
rain outside of the main forcing area this afternoon. Meanwhile as
the eddy progresses eastward, drier northerly low level flow will
develop, and the Denver area could begin to dry out before the
end of the day as everything slides eastward. The northern and
probably even the central mountains should see a lower chance of
storms this afternoon because of this drying, and may have a
convective peak in early to mid afternoon. Given the increased low
level moisture, there is still some threat of storms in all but
the northern border areas however. Trimmed temperatures back
slightly in all but the northern areas for cloud cover, but not
nearly as cool as some of the wet guidance. For tonight the storms
and clouds will slowly move east. Threat of showers and a few
storms should linger out east much of the night, but enough
clearing for temps to drop into the upper 50s in most areas by
morning.

.LONG TERM...(Sunday through Friday)
Issued at 329 AM MDT Sat Jul 15 2017

On Sunday, a weak eddy of low pressure will still be wobbling over
eastern CO in the morning which may again provide enough moisture
and instability for some thunderstorms over the cwa in the aftn.
This system has been underperforming regarding pops so will side
with just isold pops in the morning then isolated to scattered
showers or thunderstorms in the aftn. This feature is forecast to
shift off to the east by Sunday evening. For the rest of the
upcoming week, a broad ridge of high pressure will stretch from
the Desert Southwest into the southern Great Plains. A weak
southwesterly flow aloft will allow for areas of sub-tropical
moisture to slip across the state. As a result there will be a
chance of aftn and evng thunderstorms each day. The best chc of
storms will be over the high country with more isolated coverage
across the eastern plains. The severe potential will be low
through the week due to the light flow aloft, but brief moderate
to heavy rain may occur with the stronger storms due the slow
storm motions.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 329 AM MDT Sat Jul 15 2017

VFR through tonight. Thunderstorms are expected to be mainly south
and southeast of Denver in the afternoon and evening. There is a
slight chance of storms near the city between 20z and 00z which
could cause localized MVFR visibilities and require brief periods
of instrument approaches to KDEN.

&&

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

$$

SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Gimmestad



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