350
FXUS65 KGJT 300436
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1036 PM MDT Sun Sep 29 2024

.KEY MESSAGES...

- Isolated showers across northwest Colorado this evening will
  produce some gusty winds and very little rainfall.

- Near record high temperatures continue this week with very
  little spread in ensemble model outputs.

- Model agreement remains consistent with the region dominated
  by high pressure through next weekend.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 235 PM MDT Sun Sep 29 2024

The southern reaches of a trailing frontal boundary associated with
an open wave passing through Alberta this afternoon has managed to
organize into some localized instability on the terrain of the West
Slope this afternoon. Dry boundary layer conditions and weak
steering flow are keeping these features anchored to terrain and
mostly just gusty outflow, virga showers. We did see a lightning
strike in the San Juans, so at least one shower has exceeded
expectations for the day. Isolated showers will remain in the
forecast this evening across the northern half of the CWA as the
shortwave swings through. An umbrella will likely prove unnecessary,
but some gusty winds and very scattered raindrops will make it seem
more threatening. Afternoon temperatures remain well above normal
around the region, with Grand Junction Regional breaking another
record, last set in 2010. Overnight lows will remain warm as well.
Monday will find us back under the drier influence of the northwest
flow coming across the ridge in the eastern Pacific. It does look
like a bit of moisture and cloud cover will reappear on the terrain
Monday afternoon favoring our southern mountains. Afternoon thermal
instability could form another shower or two along the southern
Divide, but dry surface conditions will chew into rainfall quickly.
Highs will remain near record values again Monday with the region
cut off from the polar jet, as discussed below.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 235 PM MDT Sun Sep 29 2024

What a boring long term period. The polar front jet will stay well
to our north through Saturday. As the jet drives most disturbances
across the region, any troughs or shortwaves will also stay to our
north. An area of high pressure off the California coast will be
flattened and eventually rebuild and strengthen towards the end of
the week. This strengthening will occur over the Great Basin and be
centered squarely over the Four Corners region by Friday.
Deterministic GFS and EC are highlighting some very isolated spots
of 0.01 to 0.02 inches of precip over the San Juans during the week
but even if this occurs, it`ll be a sprinkle and that`s about it. So
it`s going to be another period of rinse and repeat. Dry, warm to
hot, and mostly sunny through Sunday. High temps will run well above
normal for early October though a slight cooldown is possible
heading into next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1033 PM MDT Sun Sep 29 2024

A wave passing by to the north over the next several hours will
keep a few stubborn showers and the occasional thunderstorm
going, mainly along and north of I-70. These showers and storms
have already proven capable of producing strong, gusty winds in
excess of 50 knots, frequent lightning, and brief heavy rain.
Skies should clear by daybreak, with winds remaining generally
light and terrain driven outside of the influence of storms. A
few fair weather cumulus will be possible during the afternoon
across the higher terrain, but otherwise expect clear skies to
prevail tomorrow, along with VFR conditions. Winds will be
westerly to northwesterly, and capable of gusting up to 25 knots
in the afternoon.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...LTB
LONG TERM...TGR
AVIATION...TGJT