559
FXUS65 KGJT 021137
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
537 AM MDT Sun Jun 2 2024

.KEY MESSAGES...

- Isolated to scattered thunderstorm development remains a
  threat each afternoon through through Monday with gusty
  outflow winds more likely than wetting rainfall.

- Afternoon showers and thunderstorms return Thursday into next
  weekend favoring the higher terrain.

- Temperatures remain above normal today and into the coming
  week. The warmest temperatures of the season thus far will be
  Thursday and Friday at 10 to 15 degrees above normal.

- The warmer temperatures means runoff will be well underway
  with most major stem rivers showing rises over the next
  several days.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 329 AM MDT Sun Jun 2 2024

The weather pattern we`ve had for the past week will continue for
another couple days with the zonal flow aloft and diurnal heating
driving orographic showers and thunderstorms over the higher
terrain. Drier air is moving into the southern areas of the region
that will significantly limit any convection in the San Juans today
and tomorrow. The stream of Pacific moisture to the north continues
to dip south to feed the shower and thunderstorm activity along and
north of the I-70 corridor. A weak shortwave embedded in the flow
will help support convecting this afternoon, and we may see an
isolated stronger storm, but lack of upper-level dynamics should
keep most of the activity on the tame side with the primary threat
continuing to be strong outflow winds gusting 35 t 45 mph.
Convection will die out through the early evening with mild weather
overnight. Tomorrow will see a similar pattern with afternoon
showers and thunderstorms along and north of the I-70 corridor, but
with the approach of a more active shortwave that will move through
overnight Monday (more on this system below in the long term
discussion), expect to see the storms to generally strengthen going
into the evening. Temperatures Today and tomorrow will continue
about five degrees above normal

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 329 AM MDT Sun Jun 2 2024

The base of a shortwave trough will edge into our northern CWA and
pass through Monday evening, allowing for showers and some isolated
thunderstorms to continue through Monday night across the north.
Moisture remains elevated and the northern mountains stand the best
chance at seeing wetting rain, not snow, as the temperatures stay
fairly mild. The lower elevations look to see trace amounts with
gusty winds the better bet. This shower and storm activity should
clear out by Tuesday morning as a ridge of high pressure builds out
west and drier northwest flow takes hold. Tuesday should provide for
highs a couple degrees cooler than Monday but still warm as we sit
near normal across the north and about 5 degrees above normal along
and south of I-70. The drier northwest flow should put an end to
convection with not much forcing or instability to really get things
going aside from perhaps some building cumulus over the high terrain
and a few isolated storms but chances are fairly low for any
convection Tuesday as a much more stable atmosphere moves in place.
Same goes for Wednesday as the high pressure ridge moves east and
builds overhead. Even drier air expected Wednesday as mixing ratios
drop to below 2 g/kg. This is the start of a significant warming
trend from mid to late this coming week as highs rise up 5 to 10
degrees above normal by Wednesday. Again, limited convective
potential for any storms to form Wednesday.

By Thursday and Friday, the ridge axis will have shifted overhead or
just east of the Divide, allowing some subtropical moisture to
advect northward as the flow becomes southwesterly. The fly in the
ointment is a cut off low off the Baja Peninsula and how this
impacts our weather as the models are struggle busting with how to
handle this cut off low as it tries to force its way through the
high pressure ridge. In the grand scheme of things, Thursday and
Friday afford to be our hottest days thus far in 2024 as high
temperatures climb to 10 to 15 degrees above normal. That`s right,
we are looking at near to low triple digit heat for the lower Grand
Valley and desert valleys of east-central and southeast Utah. Also,
the rest of the lower valleys should see 90s, the higher valleys 80s
and the mountain towns 70s. In addition to the heat, afternoon
convection should crop up again Thursday afternoon, mainly along the
western Colorado high terrain along the divide. By Friday and even
Saturday, shower and thunderstorm coverage looks to expand as models
try to move this cut off low into the ridge, some models breaking
the ridge down and allowing this cut off low to draw more moisture
and forcing into the region, while some models keep the high
pressure ridge in place, almost forming a Rex Block as the cut off
low remains over Arizona with the high pressure centered over the
Great Basin. Time will tell how this plays out, but for the time
being, higher confidence exists in the high temperature forecast
with the projected heat. Low confidence exists for the shower and
thunderstorm activity and how widespread it may be. Can pretty much
at least bet on our typical afternoon storms favoring the high
terrain primarily due to the southerly flow, afternoon diurnal
heating and instability. Low levels still appear dry and with the
heat sticking around and not much impact on temperatures, gusty
outflow winds would be a better bet with any storm activity than
wetting rain at this time.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 520 AM MDT Sun Jun 2 2024

Expect VFR conditions through the TAF period with high-based
afternoon and evening showers and thunderstorms generally over
the higher terrain north of I-70. Gusty outflow winds of 35 to
45 kts will again be the primary concern with any storm
activity. Otherwise, winds will be light this morning becoming
breezy westerlies after about 18Z. Winds drop off again
overnight.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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