National Weather Service Forecast Discussion

000
FXUS65 KBOU 271755
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1055 AM MST Wed Jan 27 2021

.UPDATE...
Issued at 1055 AM MST Wed Jan 27 2021

Area of patchy fog over the northern urban corridor and into Weld
County continues to erode with visibility improving. However, with
the erosion being slower than expected, and the cold pool of air
below it with warm advection aloft, will expect this cold pool to
persist through the day. Viewing some high res guidance, have
cooled high temperatures today over the South Platte Valley, and
areas north of the expected Denver Cyclone boundary. Southerly
winds off the Palmer Divide will allow temperatures to likely
reach into the low to mid 40s there, while north of the boundary
(a line from Golden northeast to DIA and into southern Weld
County) will remain under the cold airmass. Temperatures will
likely stay in the low to mid 30s, though the latest runs of the
HRRR keeps readings in the upper 20s. Have adjusted the max
temperature forecast today to reflect cooler temperatures in the
aforementioned areas.


&&

.SHORT TERM...(Today and tonight)
Issued at 315 AM MST Wed Jan 27 2021

An upper level ridge will build over the area today and tonight with
the flow aloft gradually becoming more southwesterly.  Outside of
some mid and high level moisture moving across no precip is expected.

For this morning, good radiational cooling and light winds combined
with moisture, from recent light snow, is allowing for the
development of fog and low clouds along nrn portions of the I-25
Corridor. Overall coverage of dense fog so far has been limited.
HRRR has been no help as each hour it has a different solution as
to how widespread it may be. Will continue to see how things
evolve the next few hours before issuing an advisory.

As for highs this aftn, not sure about overall snow cover across the
plains.  For now will keep readings in the 35 to 40 degree range but
areas with no snow cover could reach the lower to mid 40s.  Closer
to the front range HRRR has a Denver Cyclone this aftn with readings
staying in the upper 20s on the back side of the cyclone over the
nwrn suburbs into swrn Weld county.

For tonight, winds will increase over the higher terrain as the flow
aloft strengthens.  Thus will see gusty winds develop after
midnight. However speeds will stay below highlight criteria.

.LONG TERM...(Thursday through Tuesday)
Issued at 315 AM MST Wed Jan 27 2021

On Thursday, the high pressure ridge aloft will shift eastward
across the central plains resulting in an increasing southwest
flow aloft over Colorado. With this flow, thermal ridge builds
into Colorado as 700mb temperatures climb to around +2c on the
plains. This will result in warming temperatures back into the
upper 40s and 50s across the plains. Expect much of the snow cover
on the ground to be gone after Thursday.

On Friday, continued southwest flow aloft in response to incoming
Pacific system moving into the Great Basin. Generally dry through
much of the daytime, but expect an increase in snow showers across
the mountains with approaching trof and weak to moderate QG ascent.
The synoptic forcing will be strongest across Southern Colorado with
less support over Northern portions of the state. Still some slight
warming Friday afternoon as 700mb temperatures nudge upwards another
degree.  Best chance of mountain snowfall will be late Friday night
and Saturday morning with improved orographic flow from the west
and northwest. Snow showers will diminish late Saturday afternoon
and night over the mountains. Unfortunately with this open wave,
northeast Colorado will remain under a downslope northwest flow
with little or no chance of any precipitation. The system does
close off across southern Kansas but too little too late for any
benefit to the plains.

On Saturday night through Monday, broad high pressure aloft will
build back into the region with dry conditions and warming
temperatures. Readings will be back into the 50s over the plains by
Monday.

On Tuesday and Wednesday, next more potent trof will take aim over
the region with colder temperatures and a chance of snow over the
entire region. Both GFS and European solutions are dropping a storm
system into the Great Basin and possibly the 4 corners region late
Tuesday and Wednesday. However, quite a bit of variance in the
models from Wednesday and beyond on the track and intensity and some
of fear of the storm dropping too far south. For now the forecast
will show cooler temperatures and a chance of snow.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday morning)
Issued at 1055 AM MST Wed Jan 27 2021

VFR conditions expected through Thursday morning as a ridge moves
overhead. Winds will be light and variable for another hour or
two this morning, then a Denver cyclone will develop by midday.
This cyclone boundary will remain near or directly over DEN
through the afternoon, so confidence in wind directions there is
low. Generally expect northerly winds to the north and west of
this, and southerly winds to the south and east. Winds should go
to drainage by mid evening, with yet another Denver Cyclone
expected Thursday.



&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Kriederman
SHORT TERM...RPK
LONG TERM...Entrekin
AVIATION...Kriederman

NWS BOU Office Area Forecast Discussion