308
FXUS65 KGJT 031139
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
539 AM MDT Thu Jul 3 2025

.KEY MESSAGES...

- Widespread showers and thunderstorms are anticipated today,
  with an increased risk of heavy rain and localized flash
  flooding.

- Temperatures will remain below normal today and tomorrow,
  before warming to 5-10 degrees above normal early next week.

- Lingering moisture tomorrow will lead to another round of
  afternoon showers and thunderstorms over the terrain, but the
  rest of the holiday weekend will be mostly dry.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 308 AM MDT Thu Jul 3 2025

The open trough of low pressure is currently over the western Great
Basin, while the axis of the ridge of high pressure has shifted into
the western Great Plains. As a result, the plume of deepest tropical
moisture has shifted eastward into central and eastern Utah, with
PWATs sitting at 180-210% of normal. This has kept clouds and a few
light showers going mainly across eastern Utah, and southwestern
Colorado. Northwestern Colorado continues to see relatively clear
skies. Model guidance did a decent job anticipating this clear slot,
and carries it into the daytime hours. This results in warmer
temperatures forecast today, and an increased chance of organized
convection thanks to the development of increased instability. To
the west, where clouds and showers are currently and are expected to
linger, instability will be more difficult to come by. The lift
provided by the approaching trough will be enough to act on the
abundant moisture and trigger convection, but this is expected to be
more stratiform in nature, with a few embedded stronger storms. Now,
there does remain a bit of uncertainty as to whether that clear slot
will last long enough into the morning to develop the instability
necessary. If it clouds up, the entire region will see a more
stratiform event. Where organized convection does develop, look for
frequent lightning and gusty outflow winds to be the main threats.
Heavy rain and localized flash flooding will also be a concern in
prone areas today, thanks to the now saturated atmosphere and
anomalously deep moisture. In the areas that see primarily
stratiform rain, precipitation is likely to fall in a widespread,
steady light to moderate fashion. The embedded stronger storms will
provide periods of heavy rainfall, and localized flooding remains a
concern here as well. The Weather Prediction Center has the majority
of the region under a Marginal Excessive Rainfall threat, meaning
there is at least a 5% chance of rainfall exceeding local flash
flood guidance within 25 miles of a given point. Temperatures will
run 5-10 degrees below normal today, depending largely on how much
sunshine any given spot sees during the morning.

Dynamic lift provided by the approaching trough will be with us
through late tonight or early tomorrow morning, as the trough axis
isn`t projected to swing through until after midnight. This,
combined with that deep pool of moisture still in place, will keep
convection going well after sunset, although the loss of daytime
heating makes it likely that all convection will transition to a
stratiform character. All activity looks to taper off by daybreak
tomorrow as transient ridging builds in and drier air begins to
advect in. Now, after moisture surges like this, it can take a bit
of time to scour out all the surface moisture trapped in the
terrain, and indeed ensemble model guidance keeps above normal PWAT
values in place through Friday evening. This means that afternoon
showers and thunderstorms are likely to form over the higher
terrain, with gusty winds, lightning, and brief heavy rain once
again the main risks. In prone locations and areas where soils have
become saturated, a local flash flooding risk will remain through
Friday night. Activity will finally taper by midnight. Temperatures
will rebound somewhat on Friday thanks to increasing sunshine, but
will remain around 5 degrees below normal for one more day.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 308 AM MDT Thu Jul 3 2025

High pressure and dry air exert enough influence Saturday to
produce a mostly hot and dry forecast across the CWA. The terrain
immediately west of the Divide and north of highway 50 could see an
isolated shower or two pop up Saturday afternoon. Varying degrees of
subsidence pose high uncertainty in shower coverage Saturday on the
terrain. Dry boundary layers will likely keep much of anything from
reaching the surface, aside from gusty outflow winds. This should
feel familiar, as we`ve held on to this same basic regime the past
week ahead of the current moisture surge.

Sunday and beyond, models are bullish for high pressure building
over the Southwest. Some extra-tropical moisture starts to bubble
under the high from the south. This returns non-zero afternoon
precipitation chances to the CWA Sunday into Wednesday. According to
guidance, temperatures closer to the high pressure center push well
above 100 early next week around the Four Corners. Elsewhere, we
expect temperatures in excess of 7-10 degrees over climatology
during this warm up. Light winds under the high will keep critical
fire weather conditions under thresholds, but hot and very dry
conditions will persist. Showers and thunderstorms that arise will
continue to produce gusty outflow winds and potential dry lightning.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 537 AM MDT Thu Jul 3 2025

Showers have lingered across eastern Utah, and will fill in from
west to east through the next 3-6 hours. In addition, look for
gradually lowering ceilings. Areas closer to the Divide will see
clear skies for the next few hours before showers and
thunderstorms develop this afternoon. Main threats remain gusty
outflow winds, frequent lightning, and heavy rain. Outside of
the influence of storms, wind will be westerly, occasionally
gusting to 20 knots. VFR conditions are expected to prevail, but
drops to MVFR conditions will be possible under heavy rain.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BGB
LONG TERM...LTB
AVIATION...TGJT