436
FXUS65 KGJT 191020
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
420 AM MDT Fri Jul 19 2024

.KEY MESSAGES...

- Temperatures are expected to remain a few degrees above normal
  with daily thunderstorm chances through the remainder of the
  week with a slight drying trend late in the weekend.

- Threats from thunderstorms will mainly be from gusty outflow
  winds though a few storms will be capable of producing small
  hail and moderate to heavy rainfall rates. Overall flooding
  threats remain low.

- The combination of high based storms, gusty outflow winds and
  lightning will also keep a threat of new wildfire starts in
  the picture.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 418 AM MDT Fri Jul 19 2024

Satellite imagery shows the high pressure is slower to move out of
southern Arizona than the models predict, but with a shortwave
descending south out of Canada along the front range through the day
to nudge it a bit this afternoon, it should still slide northwest
towards the Great Basin through the short term period. That the high
remains farther to the south is keeping light nocturnal showers going
across southeastern Utah and southwestern Colorado at this time.
These showers should diminish going into the morning hours.

Though the dynamics associated with the descending shortwave are
weak, it will be enough to enhance the normal diurnal showers and
thunderstorms we`ve been having. Look for more widespread coverage
today over the high country with some storms moving down off the
mountains into the valleys through the afternoon. With the inverted-
V soundings, these storms will produce strong outflow winds gusting
40-50 mph, especially in the lower valleys. With weak flow aloft,
these storms may be slower moving, and in areas of training, can
produce localized flash flooding. Always be aware of your
surrounding when you`re out in the hills and note what weather is
going on around you. As the shortwave pass south of the region late
this afternoon, showers and thunderstorms will decrease northwest to
southeast across the region with lingering showers mostly along the
Divide through the evening.

Drier air moves into the region Saturday with pwats dropping below
0.6 inches across the northern areas. Expect another round of
diurnal driven afternoon showers and thunderstorms across eastern
Utah and Western Colorado with the lingering moisture, but they will
be isolated north of the I-70 corridor and more scattered to the
south.  These storms will last into the evening hours before
tapering off. Temperatures will remain near normal to five degrees
above normal through the short term period.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 418 AM MDT Fri Jul 19 2024

The ridge of high pressure remains to our west over the Great Basin
with a cut off low spinning over the Midwest to our east, leaving
our CWA in a fairly stagnant pattern with northerly flow over the
area this weekend through at least mid next week. The placement of
the high pressure far enough west will keep the deeper moisture over
Nevada, while the northerly flow advects drier air into the region
by early next week with PWAT anomalies reducing to around 60 to 80
percent of normal across the northern and central portions of the
area. Largely, the models are showing an overall decrease in storm
activity although feel that persistence is usually a good bet as
this is the same pattern that we`ve been under for some time.
Anticipate there will be enough moisture trapped under this ridge to
allow for daily afternoon convection, although best storm chances
may be more relegated to the western Colorado divide and Four
Corners regions where the better moisture resides due to the dry
northerly flow. Moisture may slowly erode, but still be enough for a
few storms to produce locally heavy rain at times although gusty
outflow winds and small hail may be the more likely outcomes. Storms
are likely to favor the higher terrain with some southward drift
into lower elevations, especially down south, but the precipitation
output for lower elevations is fairly meager at best.

By mid to late next week though, the cut off low over the Midwest
looks to get absorbed in Upper Midwest/Great Lakes trough. A Pacific
low is projected to move inland over the PacNW and help nudge the
high pressure ridge over the Great Basin further east, which may
allow this moisture trapped underneath to begin advecting eastward
into eastern Utah and western Colorado by next Thursday and beyond.
This is still a ways out and a lot of factors will influence the
forecast one way or the other, but it does provide a bit of hope for
better moisture. Temperatures will be largely unchanged with no real
advection either way, so again, persistence is your friend.  Look
for highs to be near to around 5 degrees above normal during the
coming week with warm, above normal lows as well.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1143 PM MDT Thu Jul 18 2024

Light showers will linger through the early morning with some
isolated showers possible by daybreak. However, the majority of
shower and thunderstorm activity will arrive Friday afternoon
and continue through the evening, with most TAF sites seeing
potential for VCTS. Gusty outflow winds and brief moderate to
heavy rain is possible with storms. Most storm activity is
expected to wind down after sunset, with a few isolated showers
lingering past midnight.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDA
LONG TERM...DB
AVIATION...MDA