Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 181149
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
449 AM MST Thu Jan 18 2018

.SHORT TERM...(Today and tonight)
Issued at 445 AM MST Thu Jan 18 2018

Ridge axis moving into the Rockies today with warm advection
continuing. Some high clouds are thinning as they move over the
ridge axis. This will shift slowly east, but they should be fairly
thin through today and just gradually thicken tonight.
Temperatures will be 5 to 10 degrees warmer today, then the
thickening clouds and slightly enhanced drainage winds will keep
the temperatures milder overnight tonight.

.LONG TERM...(Friday through Wednesday)
Issued at 445 AM MST Thu Jan 18 2018

...FRIDAY`S WARMTH WILL BE REPLACED BY A WINTER STORM SYSTEM WITH
SNOW AND COLDER TEMPERATURES THIS WEEKEND...

Friday will be dry and unseasonably warm as the upper ridge shifts
east. This will bring an increasing downslope component and
inversions should be fairly shallow to start the day, aiding the
warmup. However, there may be some enhanced mountain wave clouds
along the Front Range, so will have to maintain some
conservativeness with regard to possible record breaking warmth.
The record high for Denver on Friday is 68F, but we should be at
least close to that. Locations farther north including Fort
Collins and Greeley will still have to fight a bit of the
inversion and any clouds there will keep temperatures several
degrees cooler. Fire danger will become elevated over the Palmer
Divide and Park County area Friday afternoon, but winds and
humidity should both stay just under Red Flag criteria.

By Saturday, the next winter storm system which is stronger than
most of those we`ve seen this winter, will move across the Great
Basin. Showers are expected to develop ahead of this system over
the mountains due to increasing Q-G lift and moisture through the
day, while the plains remain dry. Temperatures will be hard to
pin down on the plains, but still potential for another fairly
mild day depending on exactly where surface low develops and
begins to draw colder air in from the north and northeast. At this
time, will go with the model averages which suggest highs in the
40s over the northeast plains and 50s closer to Denver.

The main shot of winter weather is still expected to move in late
Saturday night into Sunday morning. The models, which had slowed
this systems arrival over the past few runs, maintained relatively
similar speeds over the last 12 hours. Thus, expect a rain/snow
mix to develop behind the front Saturday evening across the
plains, quickly changing to snow with strong cold advection.
Favorable parameters with this storm include deep and moderate Q-G
lift, as well as steep lapse rates of 6.5-7.5 C/km. Moisture may
be somewhat limited per previous discussion and latest model
guidance. 700-500 mb specific humidities are around 2 g/kg, and
precipitable water values are near 0.25 inch. Not bad for January
but not great either. Also, the models continue to point to
northerly flow and not a terribly strong upslope component. This
could still change given the amount of lift present so will watch
this over the next couple days. Overall, it`s still looking like a
light to moderate snow event over most of the forecast area. Snow
should taper off from west to east across the plains Sunday
afternoon/early evening as the storm exits into the Central
Plains.

After that system, there is still some moisture in westerly flow
so will maintain some chance of snow in the mountains into
Tuesday. Plains locations should stay dry with temperatures
returning to near normal levels for the mid portion of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 445 AM MST Thu Jan 18 2018

VFR through tonight with light winds.

&&

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

$$

SHORT TERM...Gimmestad
LONG TERM...Barjenbruch
AVIATION...Gimmestad



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