151
FXUS65 KGJT 172107
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
307 PM MDT Sat Aug 17 2024

.KEY MESSAGES...

- Deeper monsoonal moisture develops this evening and
  thunderstorm and shower coverage will increase Sunday.

- Localized flash flooding remains a concern Sunday & Monday
  with some training thunderstorms possible.

- While moisture values decrease Tuesday, remnant moisture will
  keep afternoon showers a threat on the terrain Tuesday and
  Wednesday.

- PWAT values remain in excess of 130 percent of normal through
  week`s end, keeping showers and thunderstorms in the forecast.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 300 PM MDT Sat Aug 17 2024

Monsoonal moisture has made an abrupt return to the region. Deep
saturation has yet to enter the equation though. This morning`s
Grand Junction sounding showed some weak moisture return to the mid
levels with the dry boundary layer still holding solid. Dewpoints
are still reflecting this around the area this afternoon, with many
spots holding on to upper 30`s and low 40`s dewpoints. Around the
Utah line things get a little wetter, but one has to cross west of
the Wasatch to get into the deeper moisture. This deeper moisture
should arrive on our doorstep early this evening along a shortwave
trough that will work on some moisture and provide additional rounds
of showers. Most of this activity will favor the terrain, with a few
drifting over the valleys. Gusty outflows around 45 mph and some
light rain are possible this evening. Showers wane steeply after
midnight. Some activity could linger on the west side of the Divide,
but will conclude before daybreak. Deeper convection returns Sunday
with the atmosphere well saturated and PWAT values in excess of 150
percent  of normal around the CWA. With the dry boundary layer
conditions out of the way on Sunday, we can expect some productive
showers around the area. Localized flash flooding becomes a concern
under training storms Sunday afternoon and evening. Probabilistic
forecasts hint at a swath of rainfall in excess of 1/2 an inch
across the San Juans and northeastward into the Central Mountains.
While this remains a target of concern, there will likely be other
areas of productive rainfall. Showers will slowly decay into lighter
stratiform precipitation Sunday night and taper by daybreak Monday.
Afternoon temperatures will hover around climatology thanks to cloud
cover from storms, while overnight lows will remain on the warm side
in the higher dewpoint regime within the tropical influenced
airmass.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 300 PM MDT Sat Aug 17 2024

On Monday not much changes in the pattern with a strong low pressure
still located off the Pacific Northwest coast, and high pressure
over the Southern Plains. These two features will keep the anamolous
plume of moisture across our area so look for another day of
scattered convection. A shortwave not associated with the low or
high passes to our north and causes a slight drying on Tuesday. As
that occurs the high pressure nudges closer to the area before the
troughing eventually shoves to high way east. We will see a downturn
in afternoon storms. Despite the drying moisture is replaced rather
quickly so chances increase on Wednesday. It appears that the
moisture will stay rather steady through the end of the week. These
daily rounds of convection will lead to a continually saturating
profile, with the potential for heavy rain outweighing odds for
gusty winds with storms. As a result, flash flooding concerns will
increase from midweek onwards so, similar to last week, be sure to
stay tuned to the latest forecast before heading out or making plans
to recreate. Temperatures through the period will be a bit of a
rollercoaster. As the new work week begins daytime highs will be
sitting a few degrees above normal before climbing to 4 to 8 degrees
above normal for Tuesday. If the monsoon surge comes back as
anticipated, Wednesday`s highs will moderate by a couple of degrees
before dropping back to below normal from Thursday onwards.
Overnight lows through the long term will be unseasonably warm for
mid to late August.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1105 AM MDT Sat Aug 17 2024

Scattered storms are moving through eastern Utah now and that
trend will continue through the evening. Additional develop over
the high terrain is expected over portions of Colorado as well.
These storms will be capable of strong winds and brief heavy
rainfall. VFR conditions will prevail, but period of MVFR are
possible. Showers linger tonight with minimal impacts.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...LTB
LONG TERM...KJS
AVIATION...TGJT