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

000
FXUS65 KBOU 121121
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
521 AM MDT Tue Mar 12 2024

.KEY MESSAGES...

- A significant winter storm remains likely across portions of
  Colorado, with relatively high chances (>70%) of seeing over a
  foot of snow across most of the Front Range Mountains, Foothills
  and Palmer Divide.

- The snowfall forecast across the lower elevations is still
  uncertain and will be sensitive to shifts to the storm track,
  but confidence continues to increase in an impactful winter
  storm event across the I-25 corridor and adjacent plains.

- Snow will begin to spread across the mountains late Tuesday into
  Wednesday, with light to moderate amounts likely west of the
  divide.

&&

.SHORT TERM...(Today and tonight)
Issued at 300 AM MDT Tue Mar 12 2024

All of the weather "fun" is in the long term, but those looking
for more mild weather will find some satisfaction in today`s
forecast. High temperatures should be able to reach the lower to
mid 60s, although there will be increasing/persistent mountain
wave clouds especially in/near the Front Range as abundant high
level moisture moves across the forecast area. Scattered snow
showers ongoing in the mountains will dissipate early this morning
as drier air moves in behind this early morning`s shortwave, but
a couple spots appear likely to pick up an inch or two with snow
covered roads before they diminish. Behind that wave, downslope
winds will be increasing in/near the Front Range in these early
morning hours, and will gust to 40-50 mph in some of the wind
prone areas. Those gradients and thus winds, relax through the
afternoon.

For tonight, the next broad trough will begin to carve itself into
the western U.S and deepen. The models are all pretty similar
with showing increasing mid and upper level Pacific moisture into
the state. The large scale lift ahead of the trough will bring
more numerous snow showers into the high country by late evening
and overnight, with scattered rain showers spilling onto the
plains as well - favoring areas along and north of I-76. Impacts
will begin in the high country with snow covered and slick roads
starting to develop tonight, but the main punch of this storm
starts Wednesday into Wednesday night...see long term discussion
below.

.LONG TERM...(Wednesday through Monday)
Issued at 201 AM MDT Tue Mar 12 2024

Wednesday through Thursday evening be the primary concern for this
package.  The models still show two systems impacting northeast CO.
This first trough is progged to move across the region on
Wednesday. The main trough to the northwest, is them progged to
drop southward across UT Wednesday night, it then deepens as it
continues to drop into the Desert Southwest by 18z Thursday.

The models show a period of mainly weak mid/upper level QG ascent
over northeast CO Wednesday and Wednesday night, then its more
neutral or slightly subsident on Thursday.  Synoptically the models
are in pretty good agreement with the timing and location of these
features.  While there are not upper level jets around to impact the
area, there is a fairly prolonged period of deformation that sits
over northeast CO from around 00z Thursday to 00z Friday.  In
addition the models show very favorable mid level (500-700 mb)
lapse rates of 8.0-8.5 c/km. The first wave of mid level cold air
advection develops over region on Wednesday, with a stronger wave
of cold air advection on Thursday. In addition, favorable
east/northeast upslope flow in the mid levels during this period.
As the second trough drops into the Desert Southwest Thursday
night, these features start to weaken.

The Front Range Mountains, Foothills and Palmer Divide have the
greatest likelihood of 12+ inches of snowfall. Outside of these
areas, zones 39, 40, and western sides of zones 45 and 46 could
see 8+ inches of snowfall starting Wednesday night through
Thursday evening. The qpf generated by the GFS is around 2.0
inches of water during the heart of the event, while the other
models are more in the 1.2-1.5 inch range. would still prefer to
stick with the lower consensus qpf but overall it still looks like
a good/great snow event. The areas of greatest uncertainty are
zones 38, 43 where most of the models keep the higher qpf to the
west or south of these areas. The timing of the rain to snow
change appears to be around 00z Thu for Denver so will try to make
sure it`s hedged towards that period. Convective element should
help cool things sooner as the precipitation increases. We went
ahead and issued a Winter Storm Watch for the aforementioned
zones starting Wednesday evening.

As far as the rest of the period is concerned,  a cool and drier
northerly flow aloft will be over CO as an omega ridge sets up
along the west coast. While the plains should stay mostly dry
there will still be a chance of snow in the mountains. Warm and
drier weather will spread across the forecast area by early next
week, with high temperatures climbing back into the 60s across the
urban corridor and northeast plains on Tuesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 521 AM MDT Tue Mar 12 2024

Southwesterly flow has finally established itself at the TAF
sites, with weak subsidence noted in the wake of a passing weak
disturbance. There`s reasonable consensus (>70% confidence) that
winds will stay that way through 18Z, although still can`t rule
out some gustiness to around 20 knots at KBJC due to local
downslope. There is more uncertainty with regard to winds toward
19Z-24Z, as high clouds come in which could limit mixing. We still
think there`s a higher chance (60%) of west/northwest winds
around 8G15kts during peak heating, and a lower chance of diurnal
easterlies under 10 knots. Then winds will likely become variable
for a few hours 23Z-06Z, before a weak front moves in. We`ll also
see a chance of showers and lower ceilings down to 5000-7000 ft
AGL after 06Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 PM this evening to 6 PM MDT
Thursday for COZ031.

Winter Storm Watch from Wednesday morning through late Thursday
night for COZ033>036.

Winter Storm Watch from Wednesday evening through late Thursday
night for COZ039>041-045-046.

&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Cooper
AVIATION...Barjenbruch


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.