Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 250405
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
905 PM MST Mon Feb 24 2020

.UPDATE...
Issued at 853 PM MST Mon Feb 24 2020

As the center of the upper level trough continues to move
southeastward from over the northern high plains and onto the
central US plains of NE/KS overnight, strong northwest flow aloft
will keep the scattered snow showers going across the high
country and even onto the plains overnight. Latest CDOT cams
continue to show periods of restricted visibility over the
highest mountain terrain from showery snow and gusty winds.

As the main weather producing trough axis rotates around the
upper low in over northern CO around 12Z Tuesday, this will usher
in the coldest air at the surface along with increasing
instability aloft. Current forecast is on track with respect to
timing of the colder air, strongest winds, precip generation and
winter highlights Tuesday morning. At this time, the Front Range
Urban Corridor looks to be dominated by strong and dry downslope
flow during all of this. Thus, still expect the urban areas to
remain mostly snowfree. Will need to monitor early Tuesday to see
if any anti-cycloning takes place with surface winds being forced
into the foothills.

Main question this evening is whether to include the Palmer Ridge
in the Winter Weather Advisory as the short range models are
trending toward placing more snow to the west over the higher
terrain. Current thought is to hold off on with inclusion of the
west Palmer Ridge at this time since higher resolution models are
indicating a hit or miss, banded and showery nature to the precip
in the afternoon. Will see if later model runs ramp this up even
higher or end up decreasing coverage. Otherwise, this evening
through 12z should be the calm`er before the main action Tuesday
morning.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 328 PM MST Mon Feb 24 2020

Orographic lift from strong northwest flow aloft across the
mountains will continue to produce snow and blowing snow through
tonight and into Tuesday morning. Flow aloft turns more northerly
on Tuesday and will cause snow to decrease in the mountains.
Additional snowfall amounts of 3 to 6 inches are expected for the
mountains through Tuesday morning. The heaviest snow and strongest
winds will be found at mountain top and through the passes.
Travel will remain difficult in the higher mountains through
tomorrow morning.

A short wave trough over Montana will dive south-southeast and
strengthen into a closed low over western Kansas Tuesday morning.
Models have been trending farther west with this feature. The 12Z
ECMWF is one of the models that have trended westward. It also has
more QPF over eastern Colorado. Thinking most locations will see
some snowfall. Not a lot of moisture with this system to work
with, but 1 to 3 inches of snow seems possible over the eastern
plains. Winds will also be strong Tuesday with gusts reaching 40
to 50 mph. Wind prone areas could approach 60 mph. Because of the
snow and blowing snow, will issue a Winter Weather Advisory for
the eastern plains for Tuesday. With models trending westward,
think this system has the potential to out perform the models.

Across the Front Range, gusty west to northwest winds to 40 mph
will decrease after sunset. Northerly winds increase Tuesday
morning again with gusts to 40 mph possible. The northerly winds
user in colder air with highs Tuesday struggling to get above
freezing. A few snow showers will be possible, but the best chance
will be over the eastern plains.

.LONG TERM...(Tuesday night through Monday)
Issued at 328 PM MST Mon Feb 24 2020

The upper level system that produces the snow on the eastern
plains through tomorrow afternoon will be moving away from the
state by evening, with rapidly improving conditions expected
across northeast Colorado in the evening. Cold air will be well-
entrenched over the forecast area, and as winds decreasing and
skies become partly cloudy, temperatures will drop to some pretty
cold readings Wednesday morning. Lows in the single digits will be
common across the plains, and even colder in the mountains.

The period Wednesday through Saturday will be dry on the plains
with a general warming trend. An upper ridge building over the
western U.S. will put Colorado under northwesterly flow aloft,
which could keep things breezy in the mountains and out onto the
plains at times. A weak short wave embedded in the northwesterly
flow is expected to bring some light snow to the mountains
Wednesday night and Thursday. Snow amounts at that time look like
they will be light. As the plains remain dry, temperatures will
also be slowly rising, reaching into the 50s from Friday through
Sunday, with Saturday being the warmest day of the week.

By late in the weekend, flow over the state will be changing to
westerly and then southwesterly as a potent upper trough develops
off of the California coast. Early next week, this trough is now
forecast to move across southern Arizona and New Mexico, too far
south to have too much impact on northern Colorado. However,
cooler air will be moving into the state, which will cause the
beginning of next week to be somewhat unsettled.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 853 PM MST Mon Feb 24 2020

VFR conditions will persist overnight across the Denver Metro area
airports. Will expect a light west to southwesterly component to
the surface winds through early Tuesday morning before a cold
front brings a wind shift from the north. Will expect lowering
ceiling after 12Z along with light snowfall after 16Z. Light snow
combined with strong north to northwest winds will bring reduced
visibility through the afternoon hours of Tuesday. Will expect
improving conditions with snow coverage decreasing along with
weakening winds into Tuesday evening.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 AM to 5 PM MST Tuesday for COZ046-
048>051.

Winter Weather Advisory until 9 AM MST Tuesday for COZ031-033-
034.

&&

$$

UPDATE...Fredin
SHORT TERM...Meier
LONG TERM...Dankers
AVIATION...Fredin



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