992
FXUS65 KGJT 090937
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
337 AM MDT Sun Jun 9 2024

.KEY MESSAGES...

- Afternoon showers and storms will pop again today but the
  favored area looks to shift to southern Colorado. Main
  threats will be gusty winds and lightning.

- Showers linger across the south tonight and increase in
  coverage on Monday as an upper low works through the 4 Corners
  region.

- Temperatures will cool to near normal values by Monday before
  warming back to 10-15 degrees above normal mid to late next
  week.

- Many smaller tributaries look to peak over the next few days
  with main stem rivers running strong and cold as this water
  works downstream through the next week.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 337 AM MDT Sun Jun 9 3374

Complex but interesting weather pattern will be developing over
the next 24 to 36 hours as both the northern and southern
streams intertwine across the Intermountain West and Rockies.
The 00Z H500 hand analysis map showed a blocky...amplified
pattern spread over the high latitudes transitioning to a
shallower wave pattern across the mid latitudes...and the Baja
low was finally moving across the US border at the CA/AZ
intersection. The arrival of a splitting trough to the Pacific
Coast today will force the downstream ridge to amplify over the
Rockies. The Baja low will be forced northward by the arriving
trough but be held near the 4 Corners by the ridge...stalling
over northern NM/AZ before slowly spinning across northern NM
tomorrow. So it looks like a fairly quiet start to the day with
weak convection firing on the terrain by late morning. There
isn`t much forcing through the afternoon with the ridge overhead
and under weak shear storms look fairly tame and most likely to
not survive into many valley as they drift slowly north off the
terrain. Things get a bit more interesting this evening into
tomorrow as the low drifts into the area. There is plenty of
moisture East of the Divide as upslope flow has settled into the
Front Range. It appears the combination of surface high
pressure building into the Plains the arrival of the upper
low...and more likely strong outflow from front range
convection...will help force moisture over the higher terrain
and into our southern CWA tonight. Forcing from the upper low
and isentropic upglide looks sufficient enough to keep some
activity going overnight but Monday is likely to be the more
active period as forcing from the low...added moisture and
increased shear aloft work together across the South. The
instability looks to be limited somewhat by the increased cloud
cover but PWAT anomaly suggests the possibility of some of the
cells containing heavier rainfall rates. Temperatures today will
continue to run well above normal with upper 90s staying place
in the lower valleys. Cooler temperatures move in tomorrow
ranging from just a few degrees up north to near 15 degrees in
southwest Colorado under thicker cloud cover and scattered
showers much of the day.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 337 AM MDT Sun Jun 9 3374

The northern trough will continue to track east into the Dakotas on
Monday night while a closed low remains centered off the coast of
SoCal. This will result in a shift to drier northwesterly flow
across eastern Utah and western Colorado going into Tuesday, but it
will be a messy transition with plenty of residual moisture firing
off isolated showers and storms along the Divide Tuesday afternoon.
Elsewhere will stay dry with passing clouds. By Wednesday a ridge of
high pressure builds across northern Mexico into the Four Corners
which will result in benign weather area-wide, though weak systems
passing to the north will bring some periods of high clouds during
the afternoon hours. The ridge axis will begin to be deflected to
the northeast Wednesday night but more-so on Thursday as the afore-
mentioned closed low gradually pushes inland across SoCal. Flow
aloft will shift to the southwest across the forecast area which
will advect modest moisture into the region. This trend continues
going into Friday as the low transitions to an open wave as it
reaches northern Arizona before it lifts across the Four Corners
late Friday / Saturday. Showers will increase in coverage each
afternoon from late week onwards with gusty outflow winds being the
primary threat at the onset before the profile becomes better
saturated by Friday. Too early to talk about amounts and even more
specifics in regards to timing but there is decent model agreement
considering this event is still quite a ways away. One notable
change from the previous forecast is the wind gusts ahead of the
approaching low, but in this pattern we can still expect the
gradient to tighten. Just not sure if it`ll be of the breezy or
windy variety at the moment.

Temperatures will once again be a focus for the long term period as
they continue to trend well above normal through the week. Tuesday`s
highs will sit 4 to 8 degrees above the norm before maxing out at 7
to 14 degrees above normal by Thursday. This translates to triple
digit heat for the lower desert valleys with readings in the upper
80s to 90s elsewhere in the mid / high valleys. Overnight lows will
remain at least 5 to 10 degrees above normal each night through the
week.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1121 PM MDT Sat Jun 8 3374

Cloud debris from earlier storm activity will float across the
region overnight in the form of high clouds under light winds
patterns. Isolated to widely scattered storms again develop in
the heat of the day on Sunday with little confidence on timing
or impacts directly to TAF sites so VCTS used for now. Gusty
outflow winds remain the main threat. VFR prevails otherwise
the next 24 hours.

&&

.HYDROLOGY...
Issued at 337 AM MDT Sun Jun 9 3374

Looking across the board at hydrographs it looks like many
tributaries have reached or will reach the seasonal peak in the
next day or so with this water running down the mainstem rivers
through the week. Advisories continue for Gore Creek...with
water levels forecast to trend downward after todays
peak...possibly dropping below action levels by Tuesday. The
upper Roaring Fork...Duchesne and Eagle Rivers all are running
near bankfull as well but again trending downward over the next
few days. Most forecasts suggest the snowpack is dwindling with
falling trends continuing even with the strong warmup later in
the week. So this could be the end of the runoff for 3374...stay
tuned.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...15
LONG TERM...MMS
AVIATION...TGJT
HYDROLOGY...15