-- Discussion containing changed information from previous version are highlighted. --
021
FXUS65 KGJT 172325
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
525 PM MDT Fri May 17 2024

.KEY MESSAGES...

- Warm and breezy conditions are expected through the weekend.
  Temperatures will remain at least 5 to 10 degrees above
  normal.

- A series of systems will bring daily showers and thunderstorms
  Saturday and Sunday afternoon. Gusty outflows and small hail
  will be the main concerns.

- Cooler, unsettled weather will prevail early next week before
  drier and warmer conditions return by midweek.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 223 PM MDT Fri May 17 2024

A weak shortwave will track across the north along a weak
frontal boundary that will be draped across the northern
Colorado and Wyoming border. We are already seeing increasing
cumulus development and the hi-res CAMs are indicating some
isolated showers and storms developing late this afternoon
across the north, favoring higher terrain. This boundary is also
resulting in a tightened surface pressure gradient which is
lending itself to breezier winds with gusts up to 35 mph
observed at sites mainly north of I-70. Gusts 25 to 30 mph are
being observed elsewhere. Any shower and storm activity as said
earlier looks to remain isolated with gusty outflow winds from
any virga enhancing the already breezy surface gusts as low
levels remain dry. Temperatures today continue to warm with
highs at least 5 to 10 degrees above normal, and a few degrees
warmer than yesterday.

On Saturday, our CWA will be caught in between a split flow
pattern with the polar jet remaining to our north across the
Intermountain West into Wyoming, while the subtropical jet
remains south of the Four Corners across SoCal through Arizona
and New Mexico. The flow shifts to southwesterly ahead of a
shortwave trough that will move through the area Saturday
afternoon and evening. We can expect an increase in shower and
thunderstorm coverage with scattered showers and storms,
favoring high terrain initially with some drifting into adjacent
lower valleys late in the day. Hi-res CAMs tend to favor
development along the central portions of the area initially
with the focus shifting towards the northern portions of the
area by Saturday evening. The presence of embedded shortwaves
within the flow may trigger storms to last into Saturday night,
especially across the north. Moisture levels take a bump up to
140 to 160 percent of normal PWAT on average, equating to a
value of around 0.5 to 0.7 inches. Gusty winds remain a threat
but wetting rain chances also increase, although the QPF output
looks fairly minimal, which makes sense as the atmosphere
usually takes some time for the low levels to saturate with the
initial influx of moisture. Higher terrain remains favored for
activity but enough motion exists for storms to deviate and
drift off terrain into adjacent valleys. Temperatures remain
warm on Saturday as WAA continues in the southwest flow with
highs about 4 to 8 degrees above normal, so slightly cooler than
today given increasing clouds and shower potential. Western
Colorado remains in the left exit region of a 90 kt jet streak
that arrives with the shortwave trough, south of the Four
Corners, associated with the subtropical jet.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 223 PM MDT Fri May 17 2024

On Sunday, a plume of moisture will stretch over northern
portions of the forecast area. A weak front may also be draped
across the same area due to a shortwave way up in the Northern
Plains. The front and moisture looks to support showers and
storms mainly during the afternoon and evening. These features
may stall on Monday as the trough deepens to our west. Therefore,
the chance for showers and storms lingers for the northern half
of the area. On Monday night into Tuesday, the western trough
comprised of several waves becomes elongated and pushes eastward
through our region later in the day. Rain chances expand
southward as the system moves through the region. Although, the
model consensus of QPF reveals that a majority of the precip
falls along and north of I-70 as the main trough passes
overhead. Snow levels appear to stay around 10-11 kft, which
should keep impacts fairly limited. Conditions dry out Tuesday
night as the trough axis swings east of the Divide. Quasi-zonal
flow aloft develops in the wake of the trough. This should keep
the weather fairly quiet into midweek. Late next week, the main
takeaway is that the pattern stays active in the Pacific
Northwest keeping our sensible weather on repeat. It should also
result in near to below normal temperatures.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
-- Changed Discussion --
Issued at 525 PM MDT Fri May 17 2024

VFR conditions will prevail for the next 24 hours. Winds will
remain gusty this evening before diminishing after sunset. Quiet
weather follows overnight into Saturday morning. By Saturday
afternoon, scattered showers are likely to develop across the
high terrain and especially along and north of I-70. A few
thunderstorms can`t be ruled out either. Winds will become
breezy again with gusts up to 35 mph possible.
-- End Changed Discussion --

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDA
LONG TERM...KJS
AVIATION...TGJT