Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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 191026

Area Forecast Discussion
National Weather Service Denver/Boulder CO
426 AM MDT Mon Mar 19 2018

.SHORT TERM...(Today and tonight)
Issued at 426 AM MDT Mon Mar 19 2018

GOES-16 Water Vapor imagery shows the storm system that was
responsible for a welcome (assuming you like precipitation)
snowfall event across a good chunk or our area is moving east across
the KS/OK border. Latest radar trends show the wrap-around
precipitation shield is weaker and moved further east than
advertised in the models, and thus have dropped PoPs for all but
the far eastern Plains zones. Weak subsidence on the backside of
the short wave trough has already spread over our area and should
continue through midday. Accordingly we dropped the Winter Weather
Advisories for all areas several hours before they were
originally set to expire. The snow that fell was very wet and thus
despite continued strong north winds across the Plains through
this afternoon, do not expect any blowing snow issues. The
pressure gradient between the high across the northern Rockies and
the 994 mb low across northern Oklahoma will keep the north winds
up much of today across the eastern Plains in the 25-35 mph
range. Temperatures will be slow to warm given continued cold
advection with northerly flow at 700 mb. Expect highs in the 40s
most areas, with the coldest temps (near 40) expected along the
Palmer Divide where the heaviest snow fell. The HRRR and HRRRX
indicate some convective showers may develop over the mountains
and reach the eastern foothills during the afternoon and adjacent
Plains before they dissipate. Kept slight chance PoPs in there for
the potential west of I-25 as lapse rates are steep in the wake
of the trough and the late March sun should warm the boundary
layer. Wet bulbing would mean any precip would start as rain/snow
or graupel mix then change quickly to all snow/graupel. Little to
no accumulation expected with these showers.

In the mountains weak northwest flow will continue to advect
shallow moisture throughout today and this evening. Orographic
snow showers are possible with light accumulations in the 1-3 inch
range, generally north of I-70. Highs should be in the 20s to mid
30s and no issues expected from winds given the weak flow aloft.

Tonight seasonably cool temperatures will prevail area-wide with
clearing skies and light winds as the ridge begins to build over
our area. Flow increases across the higher mountains tonight but
only into the 30 mph range with higher gusts.

.LONG TERM...(Tuesday through Sunday)
Issued at 426 AM MDT Mon Mar 19 2018

The big picture advertised over the last couple days remains the
same. We`ll see slight upper level ridging and warming Tuesday
through Wednesday, then a subtropical moisture plume arriving
across the mountains Thursday into Friday, followed by some
cooling and a chance of unsettled weather by the weekend.

With regard to details, there is some mid and upper level moisture
underneath the building ridge and warm advection Tuesday into
Wednesday. At this point, we only see a slight chance of snow
showers in the mountains as models usually overdo the moisture a
bit in warm advection. Dry conditions will persist on the plains.
Temperatures on Tuesday should be able to reach the lower to mid
50s as downslope flow and breezy west winds combine with 700 mb
readings warming to around -4C. On Wednesday, mid level temps warm
another 5-6C so should see highs push into the mid 60s on the

By the time we reach Thursday, a continuation of warm advection in
southwest flow aloft and downslope warming should be able to boost
high temps into the lower to mid 70s on the plains. Meanwhile, the
plume of subtropical moisture which will dump significant
precipitation in Central and Southern California will approach the
state. However, by the time this moisture arrives into our
mountains the majority of it will be wrung out over numerous
mountain ranges to the southwest. As a result, we should see
showers but mainly of the light variety and even a mix of
rain/snow for elevations below ~9500 feet.

By Friday, we are still seeing signs that cold advection will
return to the mountains and thus bring a better chance of
accumulating snowfall. On the plains, we should see a weak cold front
arrive with a few showers possible late in the day or into

For this weekend, there is still considerable uncertainty with
regard to timing of short waves or intensity of those for that
matter. As a result, we`ll keep the forecast closer to climatology
for this period until more confidence in any given solution can
be obtained.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 426 AM MDT Mon Mar 19 2018

The snow has departed the metro area terminals and CIGs have
improved to MVFR. VFR conditions should occur not long after
sunrise as drier air works its way in from the north and weak
subsidence spreads across the area. North winds will be the
prevailing direction today, with gusts to 25 kts at DEN, and up
to 20 kts at APA. Winds at BJC will be much weaker, 10 kts or
less. There is an outside chance of weak rain/snow showers moving
off the mountains and making it to BJC and maybe APA. These
showers could briefly reduce flight category to MVFR and shift
winds to the west-northwest, but overall the chance of this
occurring is too low to mention in the TAFs ATTM. VFR, no precip,
and light drainage winds should occur at the metro area terminals
tonight into Tuesday morning.





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