SHORT TERM /THROUGH SUNDAY/
Issued at 223 AM MDT Sat Jul 27 2024

Drier air has started to slowly invade the region from the west, as noted by the widening T/Td spread aloft in the 00Z sounding from GJT. Still, we know how this goes, with moisture in the low and mid-levels of the atmosphere being a bit harder to scour out. As a result we've seen showers and some embedded storms linger early this morning, thanks to the slow departure of yesterday's shortwave. Some activity will continue going into daybreak before showers and storms re-develop by midday. This will be due to yet another shortwave brushing northeast Utah and northwest Colorado this afternoon, as well as the arrival of a 60 kt jetstreak overhead. The problem with the jet is its presence will be two-fold. First, it will provide additional lift for convection to develop. But, it could also be the punch that is needed to quickly advect drier air in from the west, resulting in fewer storms. CAM guidance is consistent in seeing storms develop over the higher terrain but, with surface dewpoints projected to remain in the 40s, some drift into the valleys can be expected. With better shear under the jet we could see stronger storms develop, some of which would be capable of producing gusty winds and small hail. Heavy rain and localized flooding will also be possible, but again it just depends on how quickly drier air moves in. So, not the most confident forecast and we'll just have to see how the situation evolves.

Further complicating matters is the potential for critical fire weather this afternoon. Southeast Utah is most favored, with guidance dropping humidities right into the low to mid teens.
The jet will lead to stronger winds at the surface with forecast gusts in that region right around 25 to 30 mph. The probability of seeing that combination of low humidities and gusty winds is between 40 and 60 percent. Given borderline probabilities and the potential for shower development, opted to not issue any fire weather highlights for today.

Confidence increases on Sunday as the ridge of high pressure builds to our south. Dry southwest flow will increase in earnest across eastern Utah and western Colorado as the now 70-80 kt jet remains in place. Below normal PWATs will lead to sunny skies area-wide which will allow for deeper mixing Sunday afternoon.
Widespread gusts of 25 to 30 mph are expected which, when combined with humidities in the upper single digits to low teens, will lead to critical fire weather conditions. As a result, went ahead and issued a Fire Weather Watch for zones whose fuels have been deemed critical.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
Issued at 223 AM MDT Sat Jul 27 2024

A dry period sets up for the long term period though southern portions of the forecast area will see some chances for showers and storms midweek onwards. The work week starts out with a broad, somewhat disorganized, area of high pressure setting up over Texas, extending into New Mexico and Arizona. Flow around this high will cause some subtropical moisture to move up from Mexico, reaching Arizona and New Mexico but not our CWA As this occurs, a relatively dry trough will come ashore along the West Coast and as it approaches the area, keep us under generally southwest flow. Both the GFS and EC then start advecting some of the subtropical moisture into our area. As of now, guidance suggests this moisture will be confined to the San Juans starting Tuesday afternoon and continuing for each afternoon through Friday. Coverage will slowly increase each day with the southern valleys possibly seeing some convection Thursday afternoon and again on Friday. Elsewhere, plenty of sunshine is expected as high temps reach several degrees above normal with triple digits possibly making a return for the Grand Valley and much of eastern and southeastern Utah Thursday and again Friday. A relatively weak 50kt jet streak will be stretched across the CWA through Wednesday and will bring some gusty winds to the northern half of the CWA Will need to keep an eye on things as fire weather concerns will likely increase.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
Issued at 0532 AM MDT Sat Jul 27 2024

A line of showers and storms has just entered western Colorado and will affect KGJT in the next hour or so. As it continues to move east, KRIL and possibly KEGE may see this later on this morning. Another round of convection is expected again today with some heavy rain and gusty winds being the main concerns.
Where confidence remains high, included VCTS for this afternoon.
Brief MVFR will be possible if a stronger cell moves over a TAF site. Even so, VFR will be the predominant flight condition.

FIRE WEATHER
Issued at 223 AM MDT Sat Jul 27 2024

Scattered showers and thunderstorms are expected once again today, favoring the higher terrain. Drier weather will prevail across far southeast Utah and, with occasional gusty winds, near critical fire weather conditions are possible. However, coverage and uncertainty due to possible storms prevented the issuance of a Red Flag Warning. More widespread critical fire weather conditions are becoming increasingly likely on Sunday as dry weather returns area-wide and gusts of 25 to 30 mph are expected. Therefore, a Fire Weather Watch has been issued for zones whose fuels are critical for Sunday afternoon and early evening. Similar conditions are possible Monday before winds decrease on Tuesday.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Fire Weather Watch from Sunday afternoon through Sunday evening for COZ200-202-203-205-290-292-293.
UT...Fire Weather Watch from Sunday afternoon through Sunday evening for UTZ486-487-490.