Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS65 KBOU 121637

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

Issued at 937 AM MST Fri Jan 12 2018

Snow continues to fall in the mountains this morning with most
roads being snow covered. Satellite is showing some drying moving
into south central Wyoming and should move into northern Colorado
this afternoon. The 12Z soundings at KDEN and KRIW show steep
lapse rates from 400-600mb. This is combined with a moist airmass
and strong ridgetop flow will continue to produce orographic lift
over the mountains. Snow is expected to decrease this afternoon
with the drier air moving into the area. Eventually snow will end
late this afternoon or early evening.

For northeast Colorado, a lot of echoes showing up on radar.
However, looking at web cameras and observations. Very little of
this is reaching the ground. Adjusted higher pops to the west to
line up with the stronger reflectivity. Will keep pops in the
scattered category or lower since very little precipitation is
reaching the ground. Also lowered highs over the eastern plains
where cloud cover and cold air advection should keep temperatures


.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

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 18Z TAFS through 18Z Saturday afternoon)
Issued at 937 AM MST Fri Jan 12 2018

VFR conditions will prevail through tonight, though ceilings may
approach 6000 feet behind a cold front. Westerly winds this
morning are expected to shift to the north around 20Z with the
passage of a weak cold front. Winds will then slowly turn
clockwise and end up southerly around 05Z.


Winter Weather Advisory until 5 PM MST this afternoon for COZ031-



SHORT TERM...Dankers
AVIATION...Meier is the U.S. government's official web portal to all federal, state and local government web resources and services.