589
FXUS65 KBOU 022309
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
509 PM MDT Tue Jul 2 2024

.KEY MESSAGES...

- Drying trend today, with a few showers and storms across the
  eastern plains this afternoon and evening.

- Strong to severe thunderstorms will be possible across the
  plains Wednesday afternoon/evening.

- Gorgeous weather conditions are expected on the Fourth of July.

&&

.SHORT TERM /Through Wednesday/...
Issued at 226 PM MDT Tue Jul 2 2024

A few weak storms have attempted to develop over Elbert County so
far this afternoon. MLCAPE values are rather low with SPC
mesoanalysis showing < 200 J/kg across the Palmer Divide and far
east plains. The mentioned areas will be more favored for showers
and storms this afternoon and evening. Elsewhere, chances will be
low (< 20%) with lacking moisture and instability.

Tomorrow will be warmer with temperatures warming aloft. Highs rise
into the upper 80s to low 90s across the plains and 60s/70s for the
high country. A dryline sets up across the plains likely east of
Denver County from Morgan County southward through Adams/Arapahoe
Counties with 50s dewpoints on the east side. On the west side of
the boundary, across the urban corridor and high country, it will be
well-mixed and therefore dry at the surface. Breezy conditions
combined with RH < 17% in the afternoon may result in periods of
elevated fire weather conditions for the urban corridor and higher
elevations.

Focusing back to the other side of the dryline, we will also have a
favorable environment for severe thunderstorms. An upper jet and the
passage of an upper shortwave trough will provide lift. Higher
instability will follow the dryline with the higher values on the
east side where the better moisture is. HREF mean CAPE values range
800-2000 J/kg with the higher values further east. 0-6km bulk shear
values will be in favorable ranges as well with means 30-40 kts.
This will favor a large hail and damaging wind threat for severe
strength storms that may develop. The higher threat will be again
east of the dryline as storms will likely initiate along this
boundary in the afternoon. High-res CAMs show general agreement with
segments of storms initiating on the boundary toward mid-
afternoon. There are subtle differences between individual
solutions on how far east/west it initiates on the plains, but
this is all likely reliant on where that dryline sets up
tomorrow.

&&

.LONG TERM /Wednesday night through Tuesday/...
Issued at 226 PM MDT Tue Jul 2 2024

Strong upper level high will be centered along the California
coast Thursday (4th of July). This will produce a northwest flow
aloft across Colorado. The upper level high will very slowly
progress eastward this weekend and into early next week. Only
making it to Nevada on Tuesday. Over the past several days, models
have been too progressive with this high moving eastward, thus
the temperature forecast has been on the high side. Flow aloft
over Colorado will remain northwesterly through the weekend. As
the high slowly nears Colorado, flow aloft becomes more northerly.

Now for the detail...For Wednesday evening/night, some lingering
thunderstorms will be possible into the evening before they shift
off to the east. Then a cold front pushes south through the area
overnight Wednesday and brings cooler air for the 4th of July.
Highs will be on the cool side with readings in the upper 70s to
lower 80s. Airmass will dry and be fairly stable. Can`t rule out
some weak storms over the Palmer Divide and nearby plains late in
the day. Much of the same is expected for Friday with another cool
and mainly dry day. May see breezy conditions Thursday over the
higher terrain, but winds Friday look weaker.

For the weekend, a weak trough embedded in the northwest flow
aloft will move into Wyoming Saturday. Ridging ahead of this, is
expected to bring warmer temperatures with highs around 90F. With
dry air staying in place and warming aloft, chances for showers
and storms will be very low.

The upper level trough moves across the region Saturday night. A
cold front associated with this system also pushes south through
the area Saturday night. This will bring cooler temperatures for
Sunday with highs in the upper 70s to lower 80s. The northeast
winds behind the front may increase moisture, enough for
isolated/scattered showers and storms. Models show a slight
increase in moisture, but nothing great with precipitable water
values at or slightly below normal.

For Monday and Tuesday, flow aloft becomes more northerly as the
high inches closer to Colorado. Expect temperatures to slowly
increase each day as the warm air under the high begins to filter
into the state. Chances for showers and storms still look low,
with precipitable water values at or below normal.

&&

.AVIATION /00Z TAFS through 00Z Wednesday/...
Issued at 506 PM MDT Tue Jul 2 2024

Winds were trending to more NNW and will switch to more NE
by 01z. Winds will then go more east and then to drainage
in the 07z-09z time period.  On Wed, winds will be north by
19z but may switch to WNW by 21z.  Otherwise VFR thru the
period.

&&

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

&&

$$

SHORT TERM...Mensch
LONG TERM...Meier
AVIATION...RPK