320
FXUS65 KGJT 150256
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
856 PM MDT Sun Jul 14 2024

.KEY MESSAGES...

- The desert valleys of eastern Utah and the Grand Valley in
  western Colorado remains hot today with temperatures well
  above normal. Heat Advisories remain in place through this
  evening.

- Widely scattered to scattered thunderstorm coverage and dry
  low levels will carry the elevated risk of fire starts. A Red
  Flag Warning remains in effect through this evening for areas
  where fuels are critical and better storm coverage exists.

- Temperatures remain seasonably warm with daily thunderstorm
  chances through the seven day forecast as moisture continues
  to filter in around the high pressure.

&&

.UPDATE...
Issued at 854 PM MDT Sun Jul 14 2024

A few storms persist at this hour but lightning strikes have
diminished greatly. This trend will continue over the next few
hours so the Red Flag Warning for dry lightning will be allowed
to expire. Also, temperatures have dropped below heat advisory
criteria so that advisory will also be allowed to expire.

Outflow boundaries continue to move across the area this evening
bringing some wind gusts of 35 to 45 mph. These winds will
diminish over the next few hours as convection winds down.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 302 PM MDT Sun Jul 14 2024

High pressure appears centered somewhere around Farmington near
the southwest Colorado and northwest New Mexico border in a
broad circulation area you can see on satellite with more
widespread thunderstorm activity developing over the high
terrain. Storms today have popped over all higher terrain so
more widely scattered to scattered nature as anticipated. There
is a bit of shear in this environment as evidenced by the
southwest low level cloud movement and the storm tops taking a
different direction based on the upper level flow around the
high. Storms are fairly pop and drop at this time, especially
over the San Juans where the upper level flow is opposite that
of the low level flow, likely resulting in these storms getting
sheared out and being fairly short lived. The area where the
upper level flow is helping and not hindering is southeast Utah
where storms are a bit more prolific. Dry thunderstorms still
remains a concern given the dry low levels of the atmosphere and
potential for fire starts, so the Red Flag Warning remains in
effect for those more prone areas with dry fuels and more widely
scattered or greater storm coverage. However, cannot rule out
locally moderate to heavy rain in a few cells, especially across
the south and southeast Utah where storms are training a bit.
Gusty outflow winds 40 to 50 mph and small hail also remain a
concern. Our precipitable water (PWAT) on the 12Z GJT sounding
did climb up to 0.73 inches so the moisture is increasing around
the high, but with DCAPE of 1400 to 1500 J/kg and an inverted V
sounding, gusty outflow winds are the main concern. However, the
environment will eventually adjust to the moisture increase
heading into Monday, with less of a dry thunderstorm concern and
better potential for measurable rain, especially in the higher
elevations. Expect more storm coverage and more cloud cover on
Monday. With the moisture increasing as PWAT rises to 0.75 to 1
inch across the area (about 150 percent of normal), opted not to
extend the Red Flag Warning for dry thunderstorms into Monday.

In terms of temperatures, the cloud cover has had a bit of an
impact on the heat today and forecasted highs, which are
currently running a few degrees below the forecasted highs thus
far. While above normal temperatures will still remain, the
temperatures do look to cool a bit more heading into Monday.
Therefore, opted not to extend the Heat Advisory as well for the
eastern Utah valleys and Grand Valley in west-central Colorado.
Yes, it will still be very warm but increased moisture and
therefore, cloud cover and storm activity should help provide
slightly cooler temperatures that an extension of the Heat
Advisory does not appear warranted. The current Heat Advisory
remains in effect for the remainder of the day through 9 pm MDT
this evening.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 302 PM MDT Sun Jul 14 2024

The center of high pressure oscillates around the Four Corners
through the first half of the long term period. While the
positioning of said high doesn`t appear to fall into the ideal
location for a direct plume of monsoon moisture into the CWA,
the rotating high will still provide an uptick in moisture
across the region. Precipitable water anomalies ramp up to 150
percent of normal by Tuesday, with remnant moisture rotating
overhead through Thursday. Expect a chance of showers and storms
to remain in the forecast each afternoon, favoring high terrain
on the Divide.

Ensemble guidance demonstrates a shift in high pressure, back
west of the Divide, by the end of the week. If the high
retrogrades back over to the Great Basin, GJT may tap into
supplementary moisture sources driven by low pressure systems
deepening along the lee of the Northern Rockies. PWAT anomalies
spike to 200 percent of normal over the weekend, which improves
the chance of wetting rain (i.e. measurable precipitation)
across the Western Slope. Even if desert valley floors don`t end
up seeing a lick of rain this week, increased cloud cover will
at least relax daytime highs, 3 to 8 degrees cooler. Much closer
to those seasonal norms for mid July than what we`ve experience
thus far this month.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 454 PM MDT Sun Jul 14 2024

Scattered showers and thunderstorms will continue through this
evening, favoring the higher elevations. Gusty outflow winds to
40 kts will be the main threat though some brief CIG reductions
will be possible in stronger showers. Elsewhere will experience
passing mid and high clouds. A few showers may persist into
Monday morning before storms redevelop over the mountains after
18Z. Outside of convection, occasionally breezy conditions can
be expected with gusts to around 20 kts.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.

UT...None.

&&

$$

UPDATE...TGR
SHORT TERM...MDA
LONG TERM...ERW
AVIATION...TGJT