National Weather Service Raw Text Product

723 
FXUS65 KBOU 251612
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1012 AM MDT Thu Mar 25 2021

.UPDATE...
Issued at 1011 AM MDT Thu Mar 25 2021

GOES-16 satellite and water vapor show the incoming clouds nicely
this morning ahead of a broad trough digging south across
southeast California. Clouds will increase across the area (and 
already have along and west of I-25), resulting in mostly cloudy 
skies across northeast Colorado by early afternoon. Snow cover 
continues to hold strong across Douglas and western Elbert 
Counties, and areas just east of Aurora in Arapahoe County. Temps 
today should be a touch cooler there than surrounding areas 
because of the persistent snow pack, with highs only the mid 40s. 
Elsewhere high temps look on track for today with 50s expected 
across the plains, 30s to around 40 across the mountain valleys. 
Just made a minor tweak to temps over the snow covered areas south
and east of Denver.

In terms of precipitation chances today (and p-type), we've been
monitoring the latest trends in obs and high res guidance. Our 
best best is for a few showers to form over the mountains 
afternoon with some instability developing, then moving east. The 
chance of measurable precipitation from the lower foothills east 
across the plains is low this afternoon, at around 15-20%. East of
a Greeley to Elizabeth line, then chances drop off to less than 
10 percent. In terms of p-type, anything that falls should be all 
snow above 6500 ft because of wet bulb effects, with a mix of rain
and snow down to 6,000 ft and perhaps even 5,500 ft. It should be
rain below 5,500 feet. The mountains still look good for 1-3" 
through this evening, with the best snow across the northern 
mountains in Jackson/Larimer/Grand Counties. The current forecast 
has this well handled...we mention it to say that confidence in 
the evolution for this afternoon/evening has increased with the 
latest high res guidance.

&&

.SHORT TERM...(Today and tonight)
Issued at 414 AM MDT Thu Mar 25 2021

Forecast soundings and model fields still show the potential for 
some patchy fog in the South Platte River Valley, southern Lincoln
County, and mountain valleys this morning so I have kept it in 
the forecast through about 9 am. Warming will continue today and 
highs should reach the 50s F across the plains and upper 30s to 
lower 40s F in the mountains. Mid level QG ascent and lapse rates 
will gradually increase through the day ahead of the next 
shortwave. Cloud cover will increase over the mountains and 
isolated, light showers should develop. Showers should increase in
the mountains through the day and spread out to the adjacent 
plains by late afternoon or early evening. Rain and rain-snow mix 
is probable on the plains due to the warm temperatures.

Skies will remain mostly cloudy to overcast Thursday night and 
light showers continue. Cloudy skies will help keep temperatures 
warm overnight, with lows in the upper 20s to lower 30s F on the 
plains and lower 20s F in the mountains. These warm temperatures 
overnight will probably mean persistent rain or rain-snow mix for 
the plains. Parts of the northern Front Range Mountains could see 
3 to 5 inches through Thursday night, but elsewhere accumulations 
will be much less and little to no accumulation is expected on 
the plains.

.LONG TERM...(Friday through Wednesday)
Issued at 430 AM MDT Thu Mar 25 2021

An upper level trough will be over the Great Basin on 12z Fri and 
will move southward into central Arizona by early Friday evening. 
Overall best QG ascent with this feature will stay to the west and 
southwest of the area.  However, area will be on the north side of 
an upper level jet and with favorable lapse rates still will see 
snow in the mtns with a good chance of aftn/early evening showers 
across portions of northeast CO. Temps will be cold enough for a mix 
of rain and snow at lower elevations, especially Fri evening before 
precip ends.  As for highs, readings will be in the mid to upper 40s 
across the plains.

On Sat, drier air in NW flow aloft will spread across the area. 
There could still be a few mtn snow showers in the morning but 
should see dry conditions over the area by aftn.  Highs will rise 
into the lower to mid 50s across nern CO.

By Sun,  dry WNW flow aloft will be over the area as a sfc lee 
trough develops by aftn. 1011-700 mb temps increase by 8 degrees 
c which would allow for highs in the lower to mid 60s over nern 
CO. On Mon, an upper level trough will move into the nrn Rockies 
with increasing WSW aloft over the area. This will allow for 
increasing wind and even warmer temps due to stg downslope flow. 
This would lead to highs in the upper 60s to mid 70s across the 
plains.

For Mon night into Tue, there are some differences between the ECMWF 
and GFS.  The ECMWF has a secondary trough moving into the area on 
Tue along with a cold front.  This leads to a decent chc of precip 
over the area with colder temps.  Meanwhile the GFS has a less 
defined trough with not as much moisture and far less precip.  For 
now will go with a blended solution until it becomes more obvious 
what may happen.

&&

.AVIATION...(For the 18Z TAFS through 00Z Friday evening) Issued 
at 1011 AM MDT Thu Mar 25 2021

Light winds throughout the period other than short bouts of gusty
winds associated with convective showers expected near the 
terminals both this afternoon/evening and Friday afternoon/evening.
Pinning down a preferred wind gust direction is futile but 
generally once convection gets going the prevailing winds 
direction should be WNW to NNW. The showers should develop over 
the east slope mountains this afternoon and move east. There is 
possibly going to be more than one round of convective showers 
from mid afternoon past midnight.. For now, any precipitation that
falls should be rain though it could mix with or change over 
fully to snow briefly, especially after 10 PM. Even if some falls 
as snow, there should not be any accumulation on the runways. 
Shower chances look highest from 9 PM
- 2 AM. All precipitation should be away from the terminals by 3 
  or 4 pm. ILS conditions are likely after 10 PM especially under 
  or near any of the showers.

On Friday we are expecting a similar story with convective showers
(even a chance of thunder) should form over the mountains and move
east over the terminals during the late afternoon and evening
hours. Where there is a chance of thunder, it's too low to include
in the TAFs at this time. Cloud bases should be right around 050
and BKN during the afternoon hours prior to shower activity and
will lower a bit once showers move over the terminals. Again, the
showers should be all rain until after 8 PM when they could mix 
with or change over entirely to snow but no accumulation is 
expected on runways.

&&

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

$$

UPDATE...Schlatter
SHORT TERM...Direnzo
LONG TERM...RPK
AVIATION...Schlatter