505
FXUS65 KBOU 021124
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
524 AM 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 tonight/...
Issued at 237 AM MDT Tue Jul 2 2024

Water vapor satellite shows a weak shortwave racing across
northeast Colorado this morning, with a band of weak/poorly
organized showers stretching from Park county into the far
northeast corner of the state. Another trailing shortwave is
located near the CO/WY/UT border with a few showers noted there
too.

As the parent longwave trough axis advances to the east today, the
plume of better moisture will shunt off to the south and east,
leaving most of the area dry today. Temperatures behind this
morning`s cool front will be a few degrees cooler than yesterday,
with highs in the mid 80s across the plains.

The one exception to the dry weather today may be across Lincoln
county, where models hold on to enough moisture for some modest
instability. Most members of the HREF develop a couple of storms
there this afternoon or evening. I suppose a strong storm is
possible there, but the better parameter space is east of our
forecast area into Kansas.

&&

.LONG TERM /Wednesday through Monday/...
Issued at 127 AM MDT Tue Jul 2 2024

Colorado will be under zonal flow aloft on Wednesday before a
shortwave trough arrives Wednesday night. This trough will provide
lift due to QG ascent as well as increase deep layer shear. At the
surface, lee cyclogenesis will form over northeast Colorado with
south or southeast winds developing across the far eastern plains.
Models indicate a dryline will develop across the plains with the
most likely position being from Fort Morgan to Deer Trail to Simla.
This dryline will help to initiate storms along it in the late
afternoon. The strength and coverage of these storms will depend on
the moisture and instability on the east side of the dryline. If the
models that show dew points in the low 60s to the east of the
dryline verify, CAPE values may exceed 2,000 j/kg. In that scenario,
there may be good coverage of strong to severe storms with a few
supercell thunderstorms. Large hail and severe wind gusts would be
the primary threats from these storms but there could also be a
supercellular tornado or two that develops near sunset as the low
level jet increases. The other scenario is that the moisture on
the east side of the dryline has dew points in the upper 40s to
low 50s. Instability would be much less and the chance of severe
storms would be lower. In that scenario, strong wind gusts would
be the primary threat and storms may form in a more linear
fashion. At this time, it is difficult to tell which scenario is
favored. How convection evolves today and tonight will play a
major role in what happens Wednesday.

Late Wednesday evening, a cold front will move southward
throughout our CWA which will bring much cooler and drier air. By
Thursday, the shortwave trough aloft will be east of our CWA which
will lead to subsident flow. There will also be a high pressure
center over norther Colorado and Wyoming at the surface. All of
these factors will lead to very pleasant outdoor conditions on the
Fourth of July. Highs will be in the low 80s across the plains
with plenty of sunshine. There could be a stray shower or two in
the late afternoon but the vast majority of the area will remain
dry. The only concern on Thursday will be near critical fire
weather conditions in Park County. Relative humidity will decrease
to as low as 10 percent with gusts around 30 mph possible. Across
the plains, there may be pockets of elevated fire weather
conditions due to gusts up to 30 mph. Relative humidity will not
be close to the 15 percent threshold which is nice due to the
amount of fireworks that will likely be lit.

Colorado will spend all of the time from Friday through next Monday
under northwest flow aloft. While northwest flow aloft can be an
active pattern for our CWA in the summer, it appears this period
will be rather quiet. The reason is that most of the moisture will
have been pushed out of our forecast area by the cold front that
moves through on Wednesday night. There is not a significant low
pressure system to produce easterly flow to bring the moisture
back in. Therefore, the vast majority of the area will be dry
Friday through Monday. Having said that, there will be a couple isolated
showers and storms each day so a few areas may still have to deal
with gusty winds and a little bit of rain. High temperatures will
be about 5 degrees below normal on Friday and will slowly
increase through Monday.

By the middle of next week, long range ensembles show a good signal
for very hot temperatures. This occurs as a ridge over the west
coast of the US moves eastward towards Colorado.

&&

.AVIATION /12Z TAFS through 12Z Wednesday/...
Issued at 521 AM MDT Tue Jul 2 2024

VFR through the TAF period. Secondary push of northerly winds has
made it past DEN and this northerly flow should continue for a
couple of hours before weakening. Satellite and obs upstream of
the terminals have shown no signs of producing any low stratus and
models have backed off on that potential for this morning. The
exiting mid-level cloud cover should decrease through the day.

The rest of the forecast period should be mostly quiet, with winds
generally shifting from NW to NE this afternoon and evening, with
an eventual transition to drainage flow by late evening.

&&

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

&&

$$

SHORT TERM...Hiris
LONG TERM...Danielson
AVIATION...Hiris