Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 121126
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
426 AM MST Fri Jan 12 2018

.SHORT TERM...(Today and tonight)
Issued at 426 AM MST Fri Jan 12 2018

Mountain areas are picking up light to moderate snowfall with web
cameras along the I-70 corridor showing some snow covered
highways. Models continue to show the moderate snowfall continuing
through midday and then beginning to taper off. Will let the
Winter Weather Advisory remain in effect with additional
accumulations of 4 to 8 inches expected by this evening. Scattered
snow shower activity will probably continue through tonight, but
models do not produce much QPF and satellite imagery shows a break
in the moisture plume presently working it s way over southern
Idaho.

On the plains, a batch of snow is expected to move over the
northeastern zones this morning, but with only light
accumulations. Along the i-25 corridor, northerly winds are
expected to increase as a lee trough of low pressure develops
downwind from the mountains. Wind gusts of 25 to 35 mph will be
possible at times. The downsloping winds will keep the weather dry
and bring some warming, with high temperatures making it to the
upper 40s and lower 50s. Benign weather is expected overnight as
the north to northwesterly flow aloft continues.

.LONG TERM...(Saturday through Thursday)
Issued at 426 AM MST Fri Jan 12 2018

NW flow aloft will remain over the area this weekend with some mid
and high level moisture embedded in the flow. Cross-sections
still show some lingering lower level moisture in the nrn mtns on
Sat so will keep in a chc of light snow especially in the morning.
Across nern CO it will be dry both days. At the sfc, a lee trough
will begin to develop along the front range on Sat and then
become more defined on Sun. A shallow layer of cold air will
likely remain in place over the far northeast plains on Sat but
then should begin to erode on Sun as downslope low level flow
becomes better established. Overall will have readings in the 40`s
across nern CO except 30`s over the far nern corner for Sat. On
Sun highs will warm into the lower to mid 50s except for mid to
upper 40s over the far nern plains.

For Sun night into Mon Nwly flow aloft will continue across the
region as an arctic fnt moves into nern CO.  At this time believe
the ECMWF has a better handle on temp fields versus the GFS.
Guidance temps look to high on Mon based on source region for the
cold air.  At this point will drop highs into the mid 20s to lower
30`s across the plains but it could easily be 10 degrees colder.
Meanwhile there is a potential disturbance embedded in the flow
aloft, and with nern CO being in the right exit rgn of an upper
level jet this could lead to period of snow on Mon. Thus have
bumped up pops into the chc category over the plains.

By Tue the flow aloft will become more nly as stg sfc high pres
resides over the cntrl US.  850-700 mb temps begin to moderate,
however, shallow cold air may still linger over the plains with
guidance temps still probably too warm.  Cross-sections show a dry
airmass over the area so will keep a dry fcst in place.

For Wed the ECMWF and GFS have some radical changes from what was
shown last night.  Both models now show an upper level trough moving
across the area.  The Canadian Model maintains a flat upper level
ridge over the area which was what the ECMWF and GFS were showing
last night.  Ensemble data fm the GFS shows a lot of spread so
confidence for the middle part of next week is very low.  For now
will just mention a slight chc of snow in the mtns with warmer
temperatures across the plains.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 426 AM MST Fri Jan 12 2018

Gusty winds at times should be the main aviation problem today.
Ceilings are expected to remain at or above 10,000 ft AGL through
the next 24 hours as northwesterly flow aloft carries moisture
into the mountains and the Denver area remains in a cloud shadow
downstream from the higher terrain. North to northwest winds are
expected to increase by late morning with gusts of 20 to 35 knots
around the Denver area airports. The strongest gusts will be a
KBJC, but KDEN could still see gusts up to 25 knots. Gusty winds
will continue through late afternoon. Winds will return to
diurnal southerlies during the evening.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST this afternoon for COZ031-
033-034.

&&

$$

SHORT TERM...Dankers
LONG TERM...RPK
AVIATION...Dankers



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