517
FXUS65 KGJT 251000
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
400 AM MDT Wed Sep 25 2024

.KEY MESSAGES...

- Dry and unseasonably warm conditions are expected for the
  remainder of the week. Near-record highs are expected from
  Thursday through the weekend.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 359 AM MDT Wed Sep 25 2024

High pressure remains overhead today and tomorrow resulting in
continued warm and dry conditions. Today`s temperatures are forecast
to be a few degrees warmer than yesterday with abundant sunshine.
The additional 2-3 degrees will lead to near-record temperatures in
some locations. For example, today`s daily record high temperature
is 89 at GJT and the forecast currently sits at 88. Seasonably warm
conditions amplify again tomorrow with afternoon highs around 10
degrees above normal for late September. As a result, records will
once again be on the line. Winds remain light and terrain driven
through the short term forecast.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 359 AM MDT Wed Sep 25 2024

High pressure across the West, though flattened by the mid-level
shortwave trough which moved across the northern Rockies on
Thursday, will persist on Friday. However, a couple of subtle
changes in the pattern are expected to bring some light
shower/thunderstorm activity along the southern and central
mountains along the Continental Divide Friday afternoon through
early Friday evening. First, the passage of the trough causes the
700 mb high to recenter over the eastern Colorado Plains resulting
in convergence along the Divide. Secondly, jet level heights take on
a decided cyclonic curvature overhead as they tilt toward the
deepening low over the east-central U.S. where remnant moisture from
TS Helene merges with a quasi-stationary low already in place there.
Since the 315 K isentropic surface didn`t indicate an advection of
moisture into the area, and in fact showed moisture was already in
place on Thursday (Thursday forecast is dry), it appears these
factors, when combined with above normal warmth, will be the drivers
of moist convection. Per the previous discussion, expect this
activity will mainly occur on the eastern side of the Divide, but
can`t rule out some development on the western Colorado side. NBM
was a bit slow to pick up on these developments, but expect PoPs
will rise with subsequent runs as all operational models generated
QPF over the aforementioned area during this time frame. This
activity is unlikely to pose much of a threat to the region as
moisture depth appears insufficient for heavy rain and very little
shear indicated to sustain organized convection. Therefore, expect
the main threat will be gusty outflow winds as high as 45 mph. For
the remainder of the forecast area on Friday, above normal warmth
will be the big story with record or near record highs expected for
some locations.

The low with remnants of Helene will persist over the east-central
states through the weekend essentially preventing the area of high
pressure over the West from moving off. In fact the high retrogrades
just a bit and as a result, temperatures will remain near record
levels with little chance for precipitation. A trough moving over
the northern tier states flattens the ridge and by Monday return
flow towards the Divide from the east brings the potential for
isolated showers and/or thunderstorms during the afternoon/early
evening both Monday and Tuesday. Again, this activity isn`t likely
to be impactful and NBM just hinting at moist convection at this
time. Meanwhile, highs will continue to run well above normal with
highs continuing to challenge records.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1012 PM MDT Tue Sep 24 2024

High pressure will continue with VFR conditions at terminals
through the TAF period. Light terrain driven winds and clear
skies will continue.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...KAA
LONG TERM...NL
AVIATION...TGJT