985
FXUS65 KBOU 311732
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1132 AM MDT Fri May 31 2024

.KEY MESSAGES...

- Chance of more storms today and tonight, a few could be severe
  with the greatest threat over the Palmer Divide into East
  Central Colorado.

- Severe storm threat again on Saturday, turning warmer.

- Hottest temperatures of the year Sunday into early next week,
  along with drier weather.

&&

.UPDATE...
Issued at 1025 AM MDT Fri May 31 2024

Cold front last night has brought cooler temperatures and low
clouds to the Front Range and parts of the eastern plains. Under
the low clouds across the Front Range temperatures are still only
in the lower 50s. These clouds are expected to burn off early this
afternoon allowing temperatures to warm into the upper 60s to
lower 70s. Over the Palmer Divide and across the plains south of
I-76, low clouds are scattered which is expected to allow better
warming. Here, with temperatures reaching the mid to upper 70s
yield ML CAPE of 1000-1500 J/kg. There is also an area of
convergence to the southeast of Denver. Expect the first storms of
the day to start here, some of which may be severe. Best chance
for severe storms today is over Elbert, Lincoln, and Washington
Counties. Expect the Front Range to be capped much of the day due
to the cooler temperatures. For this evening and overnight, a
couple models show storms developing over the northeast plains.
Given low confidence in the models and the recent severe storms
the past few evenings, will keep a chance for thunderstorms in the
forecast for the late evening and overnight hours.

&&

.SHORT TERM /Through tonight/...
Issued at 353 AM MDT Fri May 31 2024

After last night`s significant Denver hailstorm, showers and
storms pushed slowly east across the plains, and continue in these
pre-dawn hours. The next batch which came in from the northwest
appeared to have some forcing going for it with a cold
front/enhanced convergence, and some lift in the right rear
entrance region of a departing speed max. As the front continues
to undercut that, there will be a gradual weakening and
diminishing trend in the early morning hours.

For late this afternoon and evening, there is still a conditional
threat of severe storms. The cold front early this morning will
not help our cause for instability, as we`ll see areas of stratus
fill in behind it. That means somewhat cooler temperatures than
originally forecast. The low level winds fields do turn from
northerly to more easterly in the afternoon, which would support
some modest warming. However, given this morning`s frontal surge
and slow recovery, we think if any place had a higher threat of
warming/destabilization and convective initiation it would be the
Palmer Divide into southeast Colorado. That said, the low level
flow turns more southeasterly in the evening and could allow
further destabilization and weakening cap. Given MLCAPE is
advertised to climb into the 800-1500 J/kg range (if we do see
more heating e.g. Td 72/48), and deep layer shear increasing to
50+ kts, a few supercells are possible with large hail being the
primary threat again. Finally, with low level theta-e advection
this evening and another speed max passing to our north, the
severe threat could retreat northward as we head into the evening
hours possibly spreading up toward the I-76 Corridor. The highest
probabilities of anything severe would still be over the Palmer
Divide to Limon and perhaps as far north as Akron.

Some drying is then noted overnight and with the passing speed max
we think most of this convection will be ending before midnight.

&&

.LONG TERM /Saturday through Thursday/...
Issued at 353 AM MDT Fri May 31 2024

Saturday could be yet another day of severe storm threat. In fact,
it`s looking more favorable for severe storms than it did just
12-24 hour ago. There is less drying noted aloft, and thus we`ll
see higher storm coverage. Granted, most of the storms over the
mountains and along the I-25 Corridor will be higher based.
BUT...there is less lee troughing than previously advertised, and
thus there is reasonable potential the low level moisture does not
scour as far east as previously forecast. The severe threat for
Saturday afternoon into early evening could be back as far west as
the southern/eastern portions of Denver onto the adjacent plains,
with the highest probability of severe storms toward Fort Morgan,
Strasburg, and points east across the plains. MLCAPE is advertised
to get a bump up with the warmer temperatures and still moisture
advection over the plains, with 1400-2000 J/kg expected. Low
level wind shear will increase, but hodographs right now are still
fairly straight so hail and high winds will be the primary
threats. But, it`ll be the first of June and that could spell a
couple landspouts too in typical first week of June fashion.

Summer heat will take hold by Sunday, with high temperatures
pushing 90F across the I-25 Corridor and plains. We still can`t
totally rid ourselves of a severe threat over the northeast
plains, but other locations in/near the Front Range will almost
certainly be turning drier with a more pronounced downslope.
Models are still indicating a bit more mid/upper level moisture
for Sunday, enough for some virga or light rain showers in/near
the mountains especially toward the north.

For Monday and Tuesday, flat ridging in the westerly flow aloft
is expected to keep temperatures warm, in the mid 80s to lower
90s. The airmass is looking too dry for showers or storms. On
Tuesday, models are coming into better agreement showing a trough
tracking across the Northern Plains. This will cause flow aloft
to turn northwesterly and bring a cold front into the area by
Monday night or Tuesday. The front should be fairly shallow though
so still expect a warm day Tuesday. There would be just a slight
(10-20%) chance of a storm.

For Wednesday and Thursday, an upper level ridge builds somewhere
over the western half of the country. Models are still unclear
where the ridge will set up. Expect warm conditions to continue
Wednesday and Thursday though slight cooling may occur behind
Tuesday`s cold front. Chances for showers and storms continue to
be low, with the vast majority of the ensemble members showing dry
conditions continuing through Thursday. One of the outliers
remains the operational GFS. It shows some subtropical moisture
moving northward late next week. Can`t rule this out, though this
seems to be a stretch given what the other models show.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1132 AM MDT Fri May 31 2024

Low stratus clouds will give way to stratocumulus clouds after
18Z with ceilings slowly rising in the 2500-5000 foot range. Best
chance for thunderstorms will be to the south and east of DEN
where less cloud cover will allow temperatures to warm and help
destabilize the airmass. Still a chance for a storm near DEN and
will continue with the VCTS beginning at 23Z. Threat for storms
ends in the 04-06Z window. Another round of storms are expected
Saturday, beginning 19-20Z. There`s a chance for low clouds
09-15Z, though they are expected to stay to north of the Denver
area.

&&

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

&&

$$

UPDATE...Meier
SHORT TERM...Barjenbruch
LONG TERM...Barjenbruch
AVIATION...Meier