352
FXUS65 KBOU 131723
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1123 AM MDT Mon May 13 2024

.KEY MESSAGES...

- Drier/warmer today with scattered late day showers and
  thunderstorms over the mountains and foothills and isolated
  showers and storms over the immediate plains.

- Scattered afternoon/evening thunderstorms Tuesday, most numerous
  in the mountains and decaying as they push east.

- Front brings cooler and wetter weather on Wednesday.

- Warmer and generally drier starting Thursday, with lesser but at
  least isolated daily afternoon showers/thunderstorm coverage,
  highest for the mountains.

&&

.UPDATE...
Issued at 1008 AM MDT Mon May 13 2024

Ridging will slowly build eastward across the Central Rockies today
and tonight. Appears to be enough moisture and instability under the
ridging to produce scattered showers and isolated thunderstorms over
the higher terrain. A few of these should survive off the higher
terrain through early evening. The current forecast calls for 10-30s
PoPs with this activity which looks on track. Made a few adjustments
the sky forecast to line up with current trends. No other changes to
the forecast were made.

&&

.SHORT TERM /Through tonight/...
Issued at 330 AM MDT Mon May 13 2024

Mostly clear conditions are noted on the satellite pictures at
this time. Winds are fairly weak across the forecast area as well.
Temperatures in in the upper 30s to mid 40s F over the plains
currently, with 30s in the foothills and 20s to mid 30s in the
mountains.

Models have upper ridging over the CWA today and tonight with fairly
weak northerly jet level flow today. It will become northwesterly
tonight. The QG fields show weak downward to neutral synoptic
scale motion today and tonight. The low level wind proggs indicate
normal drainage wind patterns expected with fairly weak speeds
both today and tonight.

Looking at moisture, it has dried out a bit from yesterday, with
precipitable water values progged in the 0.35 - 0.80 inch range
today and tonight. There is some CAPE around late in the day, with
the highest values over the mountains, foothills and immediate
plains, but it is not significant. There is some warming aloft and
instability is not great overall.  Will leave the highest late
day pops in the mountains and foothills with 20-50%s and will go
with 10-20%s over the immediate plains.

For temperatures, todays highs look 4-6 C higher than yesterday`s
highs.  I went with lower to mid 70s over the plains.

&&

.LONG TERM /Tuesday through Sunday/...
Issued at 135 AM MDT Mon May 13 2024

Zonal flow takes hold aloft on Tuesday as the weak ridge axis
departs into the Midwest, keeping a modest stream of mid-level
moisture in place over the region. Simultaneously, light
downslope flow off the Front Range below 700 mb will allow for
marginal additional warming across the lower elevations, where
temperatures with climb into the mid to upper 70`s. Weakly
unstable conditions will open the door to scattered afternoon
convection developing over the high country, then migrating east
over the urban corridor. These storms should find it rather hard
to sustain their intensities as they push off the higher terrain,
so precipitation chances will drop progressively with increasing
distance from the mountains. Warm and relatively dry near-surface
conditions will provide for DCAPE values of 700-1,000 J/Kg, thus
supporting some locally gusty outflow winds from decaying storms
as they drift eastward.

The approaching upper-level trough moves promptly overhead on
Wednesday, and the associated surface cold front is slated to push
through likely some time Wednesday morning, although there are
still a few differences in timing among the guidance. Highs on
Wednesday should be a healthy 10 to 15 degrees below Tuesday`s
values as a result. With light northeast flow prevailing in the
post-frontal environment, we`ll have a modest upslope component
through the day, aiding in the development of mostly stratiform
precipitation as it taps into a partially saturated vertical
profile. Therefore, not surprisingly, the higher precipitation
totals should be focused along the lee of the Front Range,
foothills (especially southern), Denver metro, and Palmer Divide,
with amounts between 0.20-0.70" looking fairly reasonably as an
area-wide average. Latest guidance has trended slightly drier
however, so we`ll have to keep an eye on that trend moving
forward. It`s worth mentioning that vertical temperature
differentials still seem sufficiently high to generate enough
instability for a few embedded convective elements in the
afternoon. The coldest air looks to remain farther north as this
system moves through, but snow levels could nonetheless lower to
about 9,000 ft, so potential for locally impactful snow
accumulations will still need to be monitored for the higher
elevations.

The trough exits to the east by Thursday, though northwest flow
aloft on the backside will support a low chance (~20%) for a few
weak afternoon showers/storms, primarily in the high country.
Temperatures will start to rebound as well, with some parts of the
plains and urban corridor potentially bouncing back into the 70`s.
Warming accelerates Friday into Saturday as a thermal ridge
expands over the Rocky Mountain region. Scattered afternoon
showers/storms look reasonable each day, but no signals at this
time for any overly wet or severe weather pattern.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1123 AM MDT Mon May 13 2024

VFR to prevail through tonight and Tuesday. There will be a chance
for gusty winds around the showers and storms that form, otherwise
light diurnal winds will prevail. Scattered showers and isolated
thunderstorms are expected to form over the higher terrain west
of Denver after 18Z. Isolated showers/storms will be possible in
the Denver area. There`s about a 10 percent chance for a
thunderstorm at the airports. Gusty outflow winds will accompany
some the showers and storms that develop, and could produce a wind
shift.

&&

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

&&

$$

UPDATE...Meier
SHORT TERM...RJK
LONG TERM....Rodriguez
AVIATION...Meier