Area Forecast Discussion
Issued by NWS Grand Junction, CO

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931
FXUS65 KGJT 152339
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
539 PM MDT Mon Jul 15 2024

.KEY MESSAGES...

- Temperatures are expected to remain a few degrees above normal
  with daily thunderstorm chances through the remainder of the
  week and into the weekend as moisture is recycled under the
  area of high pressure over the region.

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

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

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 252 PM MDT Mon Jul 15 2024

SubTropical High pressure was centered over the S.Rockies on
this morning`s H500 hand analysis map. This high will be slowly
nudged back to the West through midweek as another trough digs
into the Upper MidWest. Staying under the main circulation of
this high will basically bring a run...rinse and repeat pattern
in place the next several days. There is a lack of a deeper
monsoonal moisture tap and large scale forcing so there is
nothing really to throw a dart at for the thunderstorm forecast.
Instead mesoscale forcing is more likely to give a clue to where
storm chances may be a bit more robust...as in the remnant
circulation that was drifting northward through central Utah
this morning and fired early storms off the Tavaputs. Another
weakly defined wave in PVU fields across N.Utah has also given
the storms over the Uintas a bit of punch. These won`t be
handled well in the models and expect to makes adjustment on the
fly the next few days. The pattern will support the typical
terrain based storms forming by mid-day. The challenge will be
watching how these storms evolve through the day with moisture
profiles still suggestive of gusty outflow winds and boundary
interactions driving storm the storm mode. Under the right
scenario some of the storms will be capable of heavier rainfall
rates and producing some hail but the flooding threat remains
low at this time. The moisture profile and lingering energy
supports nocturnal storm activity but again nothing is written
in stone attm. Otherwise temperatures will continue to run above
normal until further notice with residual convective cloud
cover highly dictating overnight lows as well.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 252 PM MDT Mon Jul 15 2024

High pressure will be sitting directly overhead by Wednesday with a
westward shift by Friday over the Great Basin and Desert Southwest.
PWAT values hover around 130 percent of normal Wednesday and
Thursday before inching up towards 160 percent of normal by Friday
into the coming weekend. With high pressure directly overhead
Wednesday and Thursday, moisture will get recycled under the high
for daily afternoon storms forming over the high terrain with gusty
outflow winds, lightning and small hail the primary threats. Cannot
rule out locally heavy rain with stronger storms but excessive
rainfall does not appear widespread as moisture is not as robust.
The high will retrograde back to the west by Friday into the weekend
as a few shortwaves track around the northern side of the ridge
through the Northern Rockies and drop down across the Divide and
Front Range, so this could be the reason for the slight bump up in
moisture levels and could result in increased shower and
thunderstorm coverage compared to Wednesday and Thursday. The lower
elevations may see some storms late in the day, especially Friday
into the weekend but overall should remain drier with gusty outflow
winds the primary concern. Temperatures remain mostly unchanged
during this stretch as high pressure keeps highs around 5 degrees
above normal but could end up closer to normal by the weekend due to
increased clouds and showers. This pattern though with the high
pressure ridge to our west and northerly to northwest flow over
western Colorado is not a particularly favorable for a monsoonal
moisture return. Daily storms and convection seem more a product of
recycled moisture left under this ridge and disturbances tracking
down the Front Range into the Plains. Details are a bit unresolved
so some uncertainty exists in the forecast this weekend and
beyond.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 534 PM MDT Mon Jul 15 2024

Showers and storms have fired again this afternoon bringing some
brief, heavy rain and gusty outflow winds to TAF sites. This
trend will continue through 02-03Z before convection dies down.
Outflow boundaries will linger across the region keeping those
variable and gusty winds in the forecast for the next several
hours, however. Calm conditions expected overnight with another
round of convection expected again tomorrow afternoon and
evening with more gusty outflows and some brief, heavy rain.
Despite the convection, widespread VFR is expected to continue
for the next 24 hours.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...15
LONG TERM...MDA
AVIATION...TGJT