Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 250445

Area Forecast Discussion
National Weather Service Denver/Boulder CO
945 PM MST Fri Nov 24 2017

Issued at 945 PM MST Fri Nov 24 2017

The forecast area remains under a swift northwest flow which has
swept the low and mid-level clouds covering the plains earlier
this evening pretty much out of the state. However, GOES-16 IR and
water vapor satellite imagery shows the next wave of mid and high-
level moisture streaming in from southern Idaho and northern
Utah. The thicker clouds presently over sern Idaho are being
enhanced by a weak mid-level shortwave disturbance which models
show tracking southeast over north-central Colorado by around 08z
tonight. As this feature passes by, should see a fairly rapid
increase in cloud cover over the northern mtns and high valleys,
and possibly a few light snow showers at the highest elevations.
Some of this cloud cover may spill out over the plains during the
pre-dawn hours in the form of a standing mtn wave cloud. Once the
shortwave moves through, should see gusty westerly winds dvlpg on
the east facing slopes of the Front Range with increasing mtn top
stability amplifying the mtn wave. Gusts in the 30-45mph range a
possibility esply in those wind prone areas. Lastly, may see
overnight temperatures oscillate up and down a few degs with
passing cloud cover and periods of gusty downslope winds. As
usual, warmest readings will likely show up in breezy areas along
the base of the foothills.


.SHORT TERM...(This evening through Saturday)
Issued at 335 PM MST Fri Nov 24 3357

A strong northwesterly flow aloft this afternoon and early
evening with a 120 kt upper level jet max will translate south
and east across the cwa. A band of showers along the northern
border this aftn has also produced a couple of lightning strikes
as well. Will keep sct to likely pops in the high country, with 10
to 20 percent coverage across the northeast plains. Best chc for
pcpn will be from around 20z this aftn to 02z this evening. Cold
front has pushed through Greeley an should push into the Denver
area in 22-23z period. Will add isolated thunder to the mountains,
foothills and northeast plains through 23z due to the upper level
jet and afternoon instability. By this evening, the focus should
quickly shift to the Palmer Divide. Will keep isolated pops there
until mid evening but drop the thunder. Strong wind gusts will
likely persist in the mountains above timberline tonight, then
decrease on Saturday. Dry and stable on Saturday with high
pressure at the surface and aloft. Gusty winds in the mountains on
Saturday as well but not as strong as today. A little cooler with
the highs around 60 for Denver.

.LONG TERM...(Saturday night through Friday)
Issued at 335 PM MST Fri Nov 24 3357

Moderate westerly flow aloft will continue with several embedded
features. Pretty good model agreement through Tuesday, then models
are completely out of phase by Friday.

A weak warm front aloft will move over bringing some clouds
Saturday night, the the ridge axis will be over on Sunday.
Temperatures will be warmer with very dry aloft that should mix
some lower dew points to the surface. Flow will be a little
stronger on Monday with similar temperatures aloft. There will
likely be a bit better mixing for more wind and a little more
warming on the plains. There may also be a window for some wave
enhancement with another weak shortwave early Monday, but in
general just expecting the same pattern of winds mixing down the
east slopes that we have had this week. Wave clouds will likely
vary, but in a dry air mass they should be less and thinner on
Sunday and Monday.

Some convergence in model simulations for the Tuesday/Wednesday
trough. EC has been slower/deeper/further south but has come back
a bit with a low just closing off but progressive across the
southern Colorado border Tuesday night into Wednesday. GFS has
been weaker but is trending toward this solution. Enough
confidence to bump up PoPs a bit in this period, though the focus
could well be across southern Colorado. Temperatures warm at the
start of this, but then cooling so probably snow or a rain/snow
mix on the plains.

Fair agreement on another wave coming Wednesday night or Thursday,
though the timing and placement varies a bit. Looks to be strong
enough for at least some showers and another surge of cooler air.
This time it should be cold enough for all snow. Raised mountain
PoPs and introduced some on the plains. After that, there is
enough difference in timing and development that the models are
out of phase for Friday. Some agreement on a dry environment and
continue westerly flow. Forecast highs range from around 40 to the
lower 60s depending on which run you look at.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 945 PM MST Fri Nov 24 2017

South-southeast winds 5-15kts will dominate overnight except near
the Front Range foothills, such as at KBJC, where later tonight
could see gusty west winds of 20-30 kts. Otherwise VFR conditions
will prevail with a mid-level mountain wave cloud possibly
forming over the area after 09z tonight.




LONG TERM...Gimmestad
AVIATION...Baker is the U.S. government's official web portal to all federal, state and local government web resources and services.